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Biomechanical testing of the LCP - How can stability in locked internal fixators be controlled?
Abstract
New plating techniques, such as non-contact plates, have been introduced in acknowledgment of the importance of biological factors in internal fixation. Knowledge of the fixation stability provided by these new plates is very limited and clarification is still necessary to determine how the mechanical stability, e.g. fracture motion, and the risk of implant failure can best be controlled. The results of a study based on in vitro experiments with composite bone cylinders and finite element analysis using the Locking Compression Plate (LCP) for diaphyseal fractures are presented and recommendations for clinical practice are given. Several factors were shown to influence stability both in compression and torsion. Axial stiffness and torsional rigidity was mainly influenced by the working length, e.g. the distance of the first screw to the fracture site. By omitting one screw hole on either side of the fracture, the construct became almost twice as flexible in both compression and torsion. The number of screws also significantly affected the stability, however, more than three screws per fragment did little to increase axial stiffness; nor did four screws increase torsional rigidity. The position of the third screw in the fragment significantly affected axial stiffness, but not torsional rigidity. The closer an additional screw is positioned towards the fracture gap, the stiffer the construct becomes under compression. The rigidity under torsional load was determined by the number of screws only. Another factor affecting construct stability was the distance of the plate to the bone. Increasing this distance resulted in decreased construct stability. Finally, a shorter plate with an equal number of screws caused a reduction in axial stiffness but not in torsional rigidity. Static compression tests showed that increasing the working length, e.g. omitting the screws immediately adjacent to the fracture on both sides, significantly diminished the load causing plastic deformation of the plate. If bone contact was not present at the fracture site due to comminution, a greater working length also led to earlier failure in dynamic loading tests. For simple fractures with a small fracture gap and bone contact under dynamic load, the number of cycles until failure was greater than one million for all tested constructs. Plate failures invariably occurred through the DCP hole where the highest von Mises stresses were found in the finite element analysis (FEA). This stress was reduced in constructions with bone contact by increasing the bridging length. On the other hand, additional screws increased the implant stress since higher loads were needed to achieve bone contact. Based on the present results, the following clinical recommendations can be made for the locked internal fixator in bridging technique as part of a minimally invasive percutaneous osteosynthesis (MIPO): for fractures of the lower extremity, two or three screws on either side of the fracture should be sufficient. For fractures of the humerus or forearm, three to four screws on either side should be used as rotational forces predominate in these bones. In simple fractures with a small interfragmentary gap, one or two holes should be omitted on each side of the fracture to initiate spontaneous fracture healing, including the generation of callus formations. In fractures with a large fracture gap such as comminuted fractures, we advise placement of the innermost screws as close as practicable to the fracture. Furthermore, the distance between the plate and the bone ought to be kept small and long plates should be used to provide sufficient axial stiffness.
... In a no-gap model, Ellis and colleagues showed significantly lower strains when screws were placed further away from the osteotomy site than when screws were positioned close to it. 10 This correlates with the findings in Stoffel and colleagues 11 whereby an increased plate working length reduced plate stress in a 1-mm fracture gap model. This has further been supported by several authors who have suggested that shortening the working length of the plate by placing screws closer to the fracture site increases plate strain, predisposing it to failure. ...
... 9,12 Contrary to the above-mentioned studies, other studies have demonstrated that plate strain is significantly lowered and more evenly distributed in large fracture gap constructs with a shorter plate working length placed in cyclical axial loading. 10,11,13,14 Chao and colleagues 14 demonstrated that larger plate working lengths resulted in larger bending moments on the plate, resulting in higher plate strain and higher plate failure when the working length is increased. ...
... This may have led to the potential misinterpretation of the results and to the propagation of the concept that an increased working length better distributes strain along the plate and decreases plate strain in a fracture gap model despite the fact that several studies have demonstrated lower plate strain with a shorter working length. 10,11,[13][14][15] We therefore propose to conduct a comprehensive examination of the plate strain using strain gauges under multiple realistic configurations of canine fractures, and to evaluate the effect of bone contact, screw placement, fracture length, and fracture position on plate strain using bone surrogates subjected to "load-controlled," nondestructive loading conditions. Our null hypothesis was that in various fracture gap models a shorter plate working length would have equal strain compared with a long plate working length. ...
Introduction This study provides a comprehensive examination of plate strain under realistic fracture configurations. The effect of plate working length, plate contact, fracture length, and position on strain was evaluated using bone surrogates subjected to “load-controlled,” nondestructive conditions.
Materials and Methods Five 3.5-mm locking compression plates (LCP) were instrumented with six strain gauges. The gauges were glued between holes in predetermined locations marked by laser engraving. Nine fracture models were created using bone surrogate, each representing a combination of the criteria under study: long versus short working length, degree of plate compression, fracture location, and fracture length. All five plates were tested under each of the nine configurations. The constructs were mounted in an Instron testing machine with a 5-kN load cell. Each specimen was cyclically loaded at a rate of 5 mm/min to 50, 100, and 200 N.
Results Decreased plate strain was noted with a short plate working length in all fracture configurations ( p < 0.05). Increasing the plate working length increased the strain at higher loads and on the plate adjacent to the fracture gap. The size of the fracture gap and fracture location had minimal effects on plate strain ( p < 0.05). Elevation of the plate off the bone (1.5 mm) resulted in increased plate strain under all loading conditions ( p < 0.05).
Conclusion Our null hypothesis was rejected in that a short plate working length resulted in decreased plate strain in all comminuted fracture configurations. Our secondary hypothesis was validated in that elevation of the plate from the bone resulted in increased strain in all configurations. As plate strain identifies regions of mechanical weakness whereby a construct may prematurely fail by acute overload or cyclic fatigue, identifying factors that may increase plate strain allows the surgeon to reduce these variables as much as possible to reduce the incidence of implant failure and subsequent fracture failure.
... Although recent biomechanical studies have shown that supplementation with a medial plate increases fixation rigidity [14][15][16][17][18], there is some debate about which plate construction provides the best mechanical environment. Ultimately, this is crucial as the appropriate stiffness and fracture motion for distal femur fracture healing is unknown, and the fixation construct can lead to a nonunion, either because it is too stiff or too flexible [3,19]. ...
... A possible explanation could be the small sample size used in our study, although the p value for the DFLP + PHLP group did not tend towards statistical significance. Another possible explanation can be attributed to the length of the plates, since for more comminuted fracture patterns, a long plate has been shown to provides better axial and torsion stability than a short plate [19]. ...
... At the same time, all implants and screws configuration used were previously well validated in biomechanical studies for distal femur fixation. [14][15][16][17][18][19][32][33][34][35][36][37]. Distal fixation of the lateral plate with at least five locking screws has been founded sufficient to fix distal femur fractures [16,35] while facilitating additional screws placement in the medial supplementary plate models. ...
IntroductionFixation of distal femur fractures with a lateral pre-contoured locking plate provides stable fixation and is the standard treatment in most cases, allowing early range of motion with a high rate of union. However, in situations, the stability achieved with the lateral plate alone may be insufficient, predisposing to fixation failure. The objective of the study was to compare, in synthetic bone models, the biomechanical behaviour of the fixation with a distal femur lateral pre-contoured locking plate solely and associated with a 3.5 mm proximal humeral locking plate applied upside down or a 4.5 mm helical locking compression plate on the medial side.Material and methodsA total of 15 solid synthetic left femur samples were used. A metaphysical defect at the level of the medial cortex was simulated. The samples were randomly distributed into three groups equally. All groups received a 4.5/5.0 mm single lateral 9-hole distal femur lateral pre-contoured locking plate. Group 1 had no supplementary plate. Group 2 received a supplementary 6-hole 3.5 mm proximal humeral locking plate and Group 3 received a supplementary 4.5/5.0 mm helical 14-hole narrow locking compression plate.ResultsBoth supplementary plate types used in groups 2 and 3 contributed to increase the apparent stiffness of the construct, but pairwise comparison showed statically significant difference only between group 1 and 3. No significant difference was observed between groups 2 and 3.Conclusion
Both supplementary plates might be considered for improving the fixation in distal femur fracture in selected cases.
... The caprine tibial segmental defect model has been well documented in the literature, but fixation and stabilization options vary among research groups [11,[16][17][18]. Fracture fixation has varied based on clinical application, and reported methods for external and internal fixation include options such as intramedullary pins/nails, intramedullary interlocking nails, single bridging plates, or overlapping auto-compression plates [25,30]. Orthopedic plate stabilization is a desirable option as it reflects the current standard of care for clinical management of fractures, does not interfere with the defect, and provides for ease of imaging assessment for evaluation of gap fillers including biomaterial scaffolds and other implants [25]. ...
... The results highlight the importance of caution when translating in vitro modeling to in vivo application of orthopedic techniques. Mechanical testing of two locking plate constructs of varying length and tibial coverage showed no difference in mechanical strength or construct stability when exposed to single cycle to failure compressive force in vitro, but upon in vivo application of the construct, significant associations of plate length and tibial coverage with construct The locking plate and locking compression plate combine mechanical stability of a type-1 external fixator with the benefits of internal fixation such as lower infection risk and lack of external interference [30]. Mechanical testing of LCP stabilized gap defects in vitro have documented superior strength against bending and compressive forces in vitro when compared to conventional dynamic compression plates, but questions have been raised regarding the fixation's torsional strength [1-3, 14,15,21]. ...
Purpose:
Locking plate fixation of caprine tibial segmental defects is widely utilized for translational modeling of human osteopathology, and it is a useful research model in tissue engineering and orthopedic biomaterials research due to its inherent stability while maintaining unobstructed visualization of the gap defect and associated healing. However, research regarding surgical technique and long-term complications associated with this fixation method are lacking. The goal of this study was to assess the effects of surgeon-selected factors including locking plate length, plate positioning, and relative extent of tibial coverage on fixation failure, in the form of postoperative fracture.
Methods:
In vitro, the effect of plate length was evaluated using single cycle compressive load to failure mechanical testing of locking plate fixations of caprine tibial gap defects. In vivo, effects of plate length, positioning, and relative tibial coverage were evaluated using data from a population of goats enrolled in ongoing orthopedic research which utilized locking plate fixation of 2 cm tibial diaphyseal segmental defects to evaluate bone healing over 3, 6, 9, and 12 months.
Results:
In vitro, no significant differences in maximum compressive load or total strain were noted between fixations using 14 cm locking plates and 18 cm locking plates. In vivo, both plate length and tibial coverage ratio were significantly associated with postoperative fixation failure. The incidence of any cortical fracture in goats stabilized with a 14 cm plate was 57%, as compared with 3% in goats stabilized with an 18 cm plate. Craniocaudal and mediolateral angular positioning variables were not significantly associated with fixation failure. Decreasing distance between the gap defect and the proximal screw of the distal bone segment was associated with increased incidence of fracture, suggesting an effect on proximodistal positioning on overall fixation stability.
Conclusions:
This study emphasizes the differences between in vitro modeling and in vivo application of surgical fixation methods, and, based on the in vivo results, maximization of plate-to-tibia coverage is recommended when using locking plate fixation of the goat tibial segmental defect as a model in orthopedic research.
... Plate osteosynthesis with rigid fixation (i.e., dynamic compression plate, limited contact dynamic compression plate, and locking plate) represents the standard treatment for metaphyseal fractures, and it provides long-term stabilization while leaving an open space for biomaterial/construct implantation [5,7,10]. However, at the early stages of fixation, this technique diverts load eccentrically from the tibial shaft to the plate, and the balance of fixation rigidity and mechanical stimulation across the fracture/ostectomy site remains a focus of biomedical research [10][11][12]. The dynamic compression plate (DCP) offers adequate biomechanical stiffness of fixation, but it is associated with potential complications from excessive periosteal contact and pressure, including potential avascular necrosis and/or impaired healing [7,13,14]. ...
... Conversely, locking plate fixation relies on the screw plate interface for fixation stability and can maintain sufficient strength in cases with weak metaphyseal bone (i.e., osteoporosis, osteomalacia, or severe fracture comminution) that would warrant tissue engineering or biomaterial-based intervention [12,15]. This construct carries similar mechanical stability to external fixation but reduces risks associated with long-term external fixation, including infection or patient-associated trauma to the fixation [6,[10][11][12]. Studies have confirmed similar rates and quality of fracture healing between DCP and locking plate fixation, despite a significant increase in fixation rigidity with the locking plate [13,16]. ...
The purpose of this study was to analyze the effects of locking plate fixation used for bridging of tibial segmental ostectomy and of cast immobilization on gait biomechanics in goats. We hypothesized that stable fixation of a segmental bone defect, using a locking plate construct, would result in minimal changes in biomechanical variables of gait in goats, but full-limb immobilization would result in lasting alterations in the immobilized limb’s gait kinetics. A pressure-sensing walkway was used to measure biomechanical characteristics for stride, gait, and walking vertical force. Thirteen, non-lame adult Boer-cross goats were trained to walk over a pressure-sensing walkway prior to instrumentation. Segmental ostectomy was performed on the right hind tibia of each goat and the defect was stabilized using bridging plate fixation with a locking compression plate. Per the protocol of an ongoing orthopedic study, the same goats underwent right hindlimb cast immobilization between one and four months postoperatively. Data was collected preoperatively and then over twelve months postoperatively in goats with unrestricted mobility. Statistical analysis revealed no significant alterations in hindlimb kinematics or maximum force when comparing the period after surgery with that after cast immobilization; significant decreases in forelimb stride length and velocity were noted postoperatively but normalized prior to cast placement, suggesting the overall functional stability of fixation. Cast immobilization had a profound and sustained effect on gait with significant alterations in both forelimb kinetics and hindlimb kinetics and kinematics for the remainder of the trial period; increased hindlimb asymmetry characterized by greater weight distribution and impulse to the left hindlimb was observed, suggesting the potential for long-term and/or permanent detrimental effects of prolonged limb immobilization.
... 7,[16][17][18] Por último, en cuanto al correcto montaje de la osteosíntesis para el tratamiento de estas fracturas, se recomiendan las placas largas que se extiendan desde el trocánter mayor hasta el fémur distal para prevenir fracturas secundarias. 19 El largo y la distribución de los tornillos se han estudiado extensamente y están documentados en el artículo de Stoffel y cols., 19 por ejemplo, para los trazos simples son, por lo menos, de 8 a 10 veces la longitud del trazo de fractura y, para los trazos conminutos, de 2 a 3 veces la longitud de la conminución, inclusive una distribución simétrica de los tornillos e idealmente un 50% de los orificios de la placa utilizados. Otro punto por considerar es el solapamiento del implante sobre la prótesis proximal, principalmente en las fracturas Vancouver tipo C, que debe incluir, al menos, 6 cm, según lo publicado por Kubiak y cols. ...
... 7,[16][17][18] Por último, en cuanto al correcto montaje de la osteosíntesis para el tratamiento de estas fracturas, se recomiendan las placas largas que se extiendan desde el trocánter mayor hasta el fémur distal para prevenir fracturas secundarias. 19 El largo y la distribución de los tornillos se han estudiado extensamente y están documentados en el artículo de Stoffel y cols., 19 por ejemplo, para los trazos simples son, por lo menos, de 8 a 10 veces la longitud del trazo de fractura y, para los trazos conminutos, de 2 a 3 veces la longitud de la conminución, inclusive una distribución simétrica de los tornillos e idealmente un 50% de los orificios de la placa utilizados. Otro punto por considerar es el solapamiento del implante sobre la prótesis proximal, principalmente en las fracturas Vancouver tipo C, que debe incluir, al menos, 6 cm, según lo publicado por Kubiak y cols. ...
Introducción: Nuestro objetivo fue analizar los resultados del tratamiento con osteosíntesis en pacientes con fracturas Vancouver tipos B1 y C, evaluar las complicaciones, las reintervenciones y la tasa de mortalidad en este grupo. Materiales y Métodos: Estudio multicéntrico, retrospectivo. Se estableció una base de datos que incluía a 53 pacientes con fracturas periprotésicas de fémur Vancouver tipos B1 y C tratadas con osteosíntesis, desde 2008 hasta 2021, en dos centros hospitalarios de alta complejidad. Resultados: La fijación proximal más utilizada fue con tornillos bicorticales más lazadas de alambre. El tipo de fractura según la clasificación de Vancouver se correlacionó con un valor significativo en el uso de tornillos de compresión interfragmentaria (p 0,001), con un total de 13 pacientes (24,52%), 9 en fracturas Vancouver tipo C. El tiempo de consolidación promedio fue de 4 meses, con un puntaje promedio del Harris Hip Score de 68. Doce pacientes (22,64%) tuvieron complicaciones: retraso de la consolidación (7 casos; 13,2%), falla de la osteosíntesis con trazo de fractura a nivel distal del tallo (un caso; 1,88%), una nueva osteosíntesis por falla a nivel del material de osteosíntesis (un caso; 1,88%) y tres fallecieron (5,66%). Conclusiones: El manejo de las fracturas femorales periprotésicas es un tema complejo y desafiante. El tratamiento con osteosíntesis constituye un método exitoso que requiere de la aplicación de principios actuales de técnicas mínimamente invasivas que, junto con una fijación proximal estable, mejoran las posibilidades de éxito.
... [10][11][12] Other fixation characteristics such as plate-working length and number of screws have been evaluated biomechanically. 13,14 However, their clinical and operative impact has not been well clarified. 13,14 This study aimed to determine the risk factors for reoperation following operative fixation of a distal femur fracture in a cohort studied over a 10-year period in a level-one trauma center.. ...
... 13,14 However, their clinical and operative impact has not been well clarified. 13,14 This study aimed to determine the risk factors for reoperation following operative fixation of a distal femur fracture in a cohort studied over a 10-year period in a level-one trauma center.. ...
Introduction: Various factors including patient demographics, fracture types, and fixation methods can affect the outcomes of distal femur fractures. This study aimed to analyze the risk factors for reoperation after operative fixation of these fractures. Methods: This was an institutional review board (IRB) approved retrospective study of extra-articular, partial articular, and complete articular distal femur fractures treated with operative fixation at a Level I trauma center between 2008 and 2018. The study included a consecutive series of adult patients operatively treated for a distal femur fracture. The primary outcome was reoperation rate due to infection, non-union, or implant failure. Periprosthetic distal femur fractures were excluded. Statistical analysis used logistic regression. Results: This study included 73 patients; 70 (96.0%) were closed fractures, and 3 were open. The average age at time of fracture was 61.6 years ± 18.2 years old. Fixation methods included external fixation (3 out of 73), intramedullary nailing (8 out of 73), and locking plates (62 out of 73). Of the 73 cases, 71 cases required nail alone, while two cases required nail and plate combination. The median follow-up time after operation was 14.2 months (InterQuartile Range, (IQR): 3.0, 17.2). Infection was reported in 6 out of 73 (8.0%) patients; reoperations occurred in 11 out of 73 (15.0%) patients. Age at presentation was the only patient demographic to negatively impact the odds of reoperation (odds ratios (OR) = 0.96, 95.0%, confidence interval (CI): [0.92, 0.99]). Patients who sustained motor vehicle accidents (MVA) were 4.6 times more likely to require reoperation when compared to falls as the mechanism of injury (P-value = 0.032). Additionally, open fracture type was 13.6 times more likely to require reoperation as compared to the closed fracture type (P-value = 0.041). Using bone grafts decreased the risk of additional surgery as there was 80.0% less chance of requiring reoperation (OR = 0.2, 95.0% CI: [0.05, 0.77], P-value = 0.019). This was the only operational characteristic to impact the odds of reoperation. Conclusion: Several risk factors may lead to reoperation following operative fixation of distal femur. This study found that age of presentation, mechanism of injury, type of fracture including Arbeitsgemeinschaft für Osteosynthesefragen, (AO)/Orthopedic Trauma Association, (OTA) classification and bone graft use can all impact the odds of reoperation. While some of these factors cannot be controlled, having a better understanding of the risk factors associated with reoperation of distal femur fractures can lead to better management of these fractures by orthopaedic surgeons
... The simple cylindrical rod representing long bone fracture for computer simulation was reported as well [6,7]. In experimental works, utilisation of cylindrical rod [6][7][8][9][10] and synthetic bone [11] to mimic long bone structures were implemented. 3D beam elements were used to model the proximal and distal of long bone to analyse the fracture fixation of external fixator system [12]. ...
... Previous studies demonstrate various methods to develop bone structure for analyses. Hollow cylinder, solid rod and beam element are some of the approaches [5][6][7]9]. In present study, instead of using structural approximation, we revealed simple technique on developing bone structure based on real anatomy. ...
Femur bone is commonly used for various experimental and computer simulation works in multidiscipline research. Various techniques are applied prior to mimic the actual bone properties. In order to perform any research related to human bone, some issues need to take into account such as cost, ethical concern and limited bone sample availability. Experimental test and computer simulation related to femur bone model commonly executed using hollow cylinder, solid rod or beam elements instead of real anatomy. The aims of present study is to provide 3D femur bone model construction considering both cortical and cancellous structures utilising only one software approach. The constructed model could be utilised for various research purposes such as computer simulation, 3D print of bone model and experimental test. Complete femur bone model which include proximal, shaft and distal condyles is successfully constructed and ready to be used for further investigation. Mimics software was the only software used in present study to performed overall task.
... FE methods additionally permit the fracture geometry, state of healing, and implant type to be rapidly and parametrically varied to evaluate implant deflections under innumerable circumstances of clinical relevance. FE and numerical analyses have frequently been implemented in fracture healing studies to evaluate the effects of implant design (59)(60)(61)(62), implant placement (63-65), bone-implant load transfer (66)(67)(68), screw placement configurations (62,65,69), fracture geometry (65,(70)(71)(72)(73)(74), and the mechanoregulation of healing (70,(75)(76)(77)(78)(79)). Yet to the authors' knowledge, only one prior study has implemented this technique to predict implant deflections (56), and this study was limited to a singular variation of fracturetreatment type. Thus, an additional goal of this study was to conduct a parametric series of 1,632 FE analyses to better characterize implant deflections. ...
... FE methods additionally permit the fracture geometry, state of healing, and implant type to be rapidly and parametrically varied to evaluate implant deflections under innumerable circumstances of clinical relevance. FE and numerical analyses have frequently been implemented in fracture healing studies to evaluate the effects of implant design (59)(60)(61)(62), implant placement (63-65), bone-implant load transfer (66)(67)(68), screw placement configurations (62,65,69), fracture geometry (65,(70)(71)(72)(73)(74), and the mechanoregulation of healing (70,(75)(76)(77)(78)(79)). Yet to the authors' knowledge, only one prior study has implemented this technique to predict implant deflections (56), and this study was limited to a singular variation of fracturetreatment type. Thus, an additional goal of this study was to conduct a parametric series of 1,632 FE analyses to better characterize implant deflections. ...
Background:
Rapid prediction of adverse bone fracture healing outcome (e.g., nonunion and/or delayed union) is essential to advise adjunct therapies to reduce patient suffering and improving healing outcome. Radiographic diagnostic methods remain ineffective during early healing, resulting in average nonunion diagnosis times surpassing six months. To address this clinical deficit, we developed a novel diagnostic device to predict fracture healing outcome by noninvasive telemetric measurements of fracture bending stiffness. This study evaluated the hypothesis that our diagnostic antenna system is capable of accurately measuring temporal fracture healing stiffness, and advises the utility of this data for expedited prediction of healing outcomes during early (≤3 weeks) fracture recovery.
Methods:
Fracture repair was simulated, in reverse chronology, by progressively destabilizing cadaveric ovine metatarsals (n=8) stabilized via locking plate fixation. Bending stiffness of each fracture state were predicted using a novel direct electromagnetic coupling diagnostic system, and results were compared to values from material testing (MT) methods. While direct calculation of fracture stiffness in a simplistic cadaver model is possible, comparable analysis of the innumerable permutations of fracture and treatment type is not feasible. Thus, clinical feasibility of direct electromagnetic coupling was explored by parametric finite element (FE) analyses (n=1,632 simulations). Implant mechanics were simulated throughout the course of healing for cases with variations to fracture size, implant type, implant structure, and implant material.
Results:
For all fracture states, stiffness values predicted by the direct electromagnetic coupling system were not significantly different than those quantified by in vitro MT methods [P=0.587, P=0.985, P=0.975; for comparing intact, destabilized, and fully fractured (FF) states; respectively]. In comparable models, the total implant deflection reduction (from FF to intact states) was less than 10% different between direct electromagnetic coupling measurements (82.2 µm) and FE predictions (74.7 µm). For all treatment parameters, FE analyses predicted nonlinear reduction in bending induced implant midspan deflections for increasing callus stiffness.
Conclusions:
This technology demonstrates potential as a noninvasive clinical tool to accurately quantify healing fracture stiffness to augment and expedite healing outcome predictions made using radiographic imaging.
... Both excessive stress values at the support and excessive movement between the fracture blocks always appear in the failure of the ULLP internal xation, especially in UOSFF. However, clinically quantifying three-dimension (3D) fracture-site motion and stress values remains impractical, and determining the location where the ULLP xation failed or resulted in implant breakage is also largely limited by the inability to measure or predict fracture-site motion [16][17][18] . Computational modeling, especially FE analysis, permits parametric investigation at a lower cost. ...
Background
Osteoporotic supracondylar femoral fractures (OSFF) have historically been managed by the lateral anatomical locking plate with reasonable success. However, for some kinds of unstable and osteoporotic supracondylar femoral fractures (UOSFF), especially with bone defects, unilateral locking plate (ULLP) fixation failed or resulted in implant breakage. This paper is going to explore what is the stable internal fixation for UOSFF by adding the bilateral locking plate (BLLP) fixation.
Methods
OSFF models were divided into two groups according to the fracture line type, which would be further subdivided according to their angle of fracture line, presence of bone defect, location and degree of bone defect. Thereafter, kinds of locking plate fixation were constructed. A 2010-N load was applied to the femoral head, and a 1086-N load was applied to the greater trochanter. In this condition, the maximum von Mises stress distribution of models were investigated.
Results
Firstly, it was obviously found that the stress concentration in the BLLP group was more dispersed than that in the ULLP group. Secondly, according to the fracture line analysis, the stress value of fracture line type in “\” model group was higher than that of “/” model group. Moreover, with the increase of fracture line angle, the stress value of the model increased. Thirdly, from the bone defect analysis, the stress value of the medial bone defect (MBD) model group was higher than that of the lateral bone defect (LBD) model group. And as the degree of bone defect increased, the stress value increased gradually in the model group.
Conclusion
In the following four cases, lateral unilateral locking plate fixation cannot effectively stabilize the fracture end, and double locking plate internal fixation is a necessary choice. First, when the angle of the fracture line is large (30, 45). Second, when the fracture line type is “/”. Third, when the bone defect is large.Fourth, when the bone defect is medial.
... The fewer-screw predictably will increase the load sharing for individual screws; however, the stability also can be controlled by changing the working length. A similar observation was also reported by Stoffel [46]. ...
An understanding of the biomechanical characteristics and configuration of flexible and locked plating in order to provide balance stability and flexibility of implant fixation will help to construct and promote fast bone healing. The relationship between applied loading and implantation configuration for best bone healing is still under debate. This study aims to investigate the relationship between implant strength, working length, and interfragmentary strain (εIFM) on implant stability for femoral midshaft transverse fractures. The transverse fracture was fixed with a fragment locking compression plate (LCP) system. Finite element analysis was performed and subsequently characterised based on compression loading (600 N up to 900 N) and screw designs (conventional and locking) with different penetration depths (unicortical and bicortical). Strain theory was used to evaluate the stability of the model. The correlation of screw configuration with screw type shows a unicortical depth for both types (p < 0.01) for 700 N and 800 N loads and (p < 0.05) for configurations 134 and 124. Interfragmentary strain affected only the 600 N load (p < 0.01) for the bicortical conventional type (group BC), and the screw configurations that were influenced were 1234 and 123 (p < 0.05). The low steepness of the slope indicates the least εIFM for the corresponding biomechanical characteristic in good-quality stability. A strain value of ≤2% promotes callus formation and is classified as absolute stability, which is the minimum required value for the induction of callus and the maximum value that allows bony bridging. The outcomes have provided the correlation of screw configuration in femoral midshaft transverse fracture implantation which is important to promote essential primary stability.
... Due to reduced technical feasibility, cantilever and torsional testing were omitted and only axial loading experiments were performed. Because this loading mode best simulates the hypothesized predominantly compressive physiologic loading at the fracture site during weight-bearing [15,39,40], and because we allowed the bone-fixator construct freedom of movement in all three dimensions, we believe that this model is still well suited to describe the clinical relevance to the lower limb. ...
Monolateral pin-to-bar-clamp fixators are commonly used to stabilize acute extremity injuries. Certain rules regarding frame geometry have been established that affect construct stability. The influence of sagittal pin angulation on construct stiffness and strength has not been investigated. The purpose of this biomechanical study was to demonstrate the effect of a pin angulation in the monolateral fixator using a composite cylinder model. Three groups of composite cylinder models with a fracture gap were loaded with different mounting variants of monolateral pin-to-bar-clamp fixators. In the first group, the pins were set parallel to each other and perpendicular to the specimen. In the second group, both pins were set convergent each in an angle of 15° to the specimen. In the third group, the pins were set each 15° divergent. The strength of the constructions was tested using a mechanical testing machine. This was followed by a cyclic loading test to produce pin loosening. A pull-out test was then performed to evaluate the strength of each construct at the pin–bone interface. Initial stiffness analyses showed that the converging configuration was the stiffest, while the diverging configuration was the least stiff. The parallel mounting showed an intermediate stiffness. There was a significantly higher resistance to pull-out force in the diverging pin configuration compared to the converging pin configuration. There was no significant difference in the pull-out strength of the parallel pins compared to the angled pin pairs. Convergent mounting of pin pairs increases the stiffness of a monolateral fixator, whereas a divergent mounting weakens it. Regarding the strength of the pin–bone interface, the divergent pin configuration appears to provide greater resistance to pull-out force than the convergent one. The results of this pilot study should be important for the doctrine of fixator mounting as well as for fixator component design.
... These observations suggested that a considerable stress concentration was applied at the distal-most screw following sagittal plane bending loads for 3.5-mm constructs. 18,44 In addition, none of the 2.7-mm constructs with a transverse fracture completely detached. Instead, the plate bent considerably, plastically deforming, and displaced the fracture. ...
Objectives
Implant prominence after ulnar fracture fixation may be mitigated by the use of lower profile plates. The biomechanical strength and stability of 2.7-mm and 3.5-mm locking compression plates for fixation were compared.
Methods
Two fracture conditions, transverse (N = 10) and oblique (N = 10), were evaluated in an in vitro study. Half of the specimens for each condition were fixed with 2.7-mm plates and the other half with 3.5-mm plates, all fixed with conventional dynamic compression mechanisms. Specimens were loaded under ±2 Nm of cyclic axial torsion, then under 10 Nm of cyclic cantilever bending, and bending to failure. Interfragmentary motion and strain were analyzed to determine construct stability as a function of fracture pattern and plate size.
Results
Interfragmentary motion was significantly larger in all constructs fixed with 2.7-mm plates, compared with 3.5-mm plates ( P < 0.01). The 2.7-mm constructs with transverse fractures had the greatest motion, ranging between 5° and 10° under axial rotation and 5.0–6.0 mm under bending. Motions were the lowest for 3.5-mm constructs with oblique fractures, ranging between 3.2 and 4.2 mm under bending and 2°–3.5° for axial rotation. For oblique fractures, the bending moment at ultimate failure was 31.4 ± 3.6 Nm for the 2.7-mm constructs and 10.0 ± 1.9 Nm for 3.5-mm constructs ( P < 0.01). Similarly, for transverse fractures, the bending moment was 17.9 ± 4.0 Nm for the 2.7-mm constructs and 9.7 ± 1.3 Nm for the 3.5-mm constructs ( P < 0.01).
Conclusions
Although 3.5-mm plates were more effective at reducing fracture motion, they were consistently associated with refracture at the distal-most screw hole under load to failure. By contrast, 2.7-mm plates plastically deformed despite excessive loads, potentially avoiding a subsequent fracture.
Level of Evidence
Level V.
... A lot of focus was placed on implant development and the evaluation of various implant types for the surgical treatment of distal femur fractures from the 1990s to the early 2000s. As a result, numerous publications comparing various plating systems for straightforward transverse or intricate intraarticular distal femoral fractures were published [4][5][6][7][8][9] . For extraarticular, sagittal unicondylar or supra-and intercondylar distal femur fracture types, the various plating systems, such as blade plates, dynamic compression plates, or locking compression plates, are all appropriate. ...
... Moreover, excessive rigidity and stress concentration increase the fracture risk around the internal fixation [7]. The length of the bridging zone could be increased by not using screws in holes that are close to the fracture site, thus reducing rigidity [8]; however, this technique has not been consistently proven to be effective [5]. ...
Background:
Locking plates are commonly used in the treatment of comminuted metaphyseal distal femoral fractures. However, locking plates form a strong structure and promote asymmetrical callus formation, which is not conducive for rapid fracture healing and may increase fracture risk. To overcome this, we designed a micromotion-balancing fixation system based on locking plates.
Methods:
Six healthy pigs (Bama miniature pigs) were used to establish a model of bilateral comminuted distal femoral fracture (AO/ASIF: 33-C2). Standard drilling was performed on one of each pig's hind limbs (control group), whereas eccentric drilling was performed on the other hind limb (experimental group). Both femurs were fixed with a 3-hole locking compression plate using 5-mm-diameter screws. At 12 postoperative weeks, all pigs were euthanized and the femurs with compression plates were radiographically examined. The level of fracture healing and loosening/internal fixation failure were recorded. Bone mineral density, number of trabeculae, trabecular morphology, and calcification precipitations were assessed.
Results:
All pigs survived, and the fractures healed. No complications related to fracture healing, such as infection and internal fixation failure, were noted. The bone mineral density of the near and far cortical calli, number of the near and far cortical callus trabeculae, and difference in bone mineral density between the near and far cortical calli in the experimental group were significantly higher than those in the control group (p < 0.01). However, the difference in the number of trabeculae between the near and far cortical calli was significantly lower in the experimental group than in the control group (p < 0.01).
Conclusion:
This newly designed system provides stable fixation for comminuted distal femoral fracture, increases the overall strain at the fracture site, and balances the strains at the near and far cortices to achieve uniform callus growth and fracture healing.
... During the 1990s to the early millennium, a great deal of attention was paid to implant development and the comparison of different implant types for surgical management of distal femur fractures. Thus, numerous publications appeared that compared different plating systems for simple transverse or complex intraarticular distal femoral fractures [4][5][6][7][8][9]. The various plating systems, such as blade plates, dynamic compression plates, or locking compression plates, are all suitable for extraarticular, sagittal unicondylar, or supra-and intercondylar distal femur fracture types. ...
Background:
Distal femur fractures are challenging in surgical management as the outcome is crucial for restoring the biomechanical stability and longitudinal axis of the leg and function of the knee joint.
Methods:
A retrospective review of all distal femoral fractures treated in a level I trauma center over a decade was performed. The radiographs were reviewed for fracture entity, osseous healing, implant failure, mechanical axis, and degenerative joint changes. Clinical outcome was reviewed regarding postoperative complications and postoperative range of motion of the knee joint.
Results:
130 patients who were managed with screw fixation (n = 35), plating systems (n = 92) or intramedullary nailing systems (n = 3) remained for evaluation. Mean follow up was 26 months. Clinical outcome was significantly better for flexion degrees following screw fixation (p = 0.009). Delayed fracture union (p = 0.002) or non-union (p = 0.006) rates were significantly higher in plate osteosynthesis. Mild pathologic deformity for varus and valgus collapse was found following plate osteosynthesis.
Conclusions:
Screw fixation shows fewer postoperative complications than plate fixation and is favored for extra and partial intraarticular distal femur fractures. Plating constructs remain the superior fixation method in complex distal femur fractures but are associated with higher rates of non-union and leg axis deviation.
... There have been multiple cases reporting the application of externalized LCP in various regions of the body [22]. It has been shown that the main factors affecting the stiffness of LCP include working length, number of screws, distance from the plate to the bone and length of the plates [23]. Thirty millimeters is the upper bound of bone-plate distance to keep fixation stable in distal tibia fractures [24,25]. ...
Background: Various techniques have been reported to treat large, segmental tibial defects, such as autogenous bone graft, vascularized free fibula transfer and bone transport. We present a case of a 24-year-old male with a 17-year history of chronic osteomyelitis with obvious lower limb length discrepancy and severe varus deformity of the tibia secondary to osteomyelitis in childhood. Aim: The aim of this work is to provide an alternative choice for treating patients in developing countries with severe lower limb deformity caused by chronic osteomyelitis. Case Presentations: Without surgical intervention for a prolonged period of time, the patient was admitted in our institute for corrective surgery. Corrective surgery consisted of three stages: lengthening with Ilizarov frame, removal of Ilizarov frame and fixation with externalized locking plate, and removal of externalized locking plate. Tibia bridging was achieved at the distal and proximal junction. The range of motion (ROM) of the knee joint was nearly normal, but the stiffness of the ankle joint was noticeable. The remaining leg discrepancy of 0.1 cm required no application of a shoe lift. Moreover, the patient could engage in daily activities without noted limping. Conclusions: Distraction–compression osteogenesis using the Ilizarov apparatus is a powerful tool to lengthen the shortened long bone and adjust the deformity of the lower limbs. Externalized locking plates provide an alternative to the traditional bulky external fixator, as its low profile makes it more acceptable to patients without compromising axial and torsional stiffness. In all, a combination of Ilizarov frame, externalized locking plate and tibia bridging is an alternative for patients in similar conditions.
... 26 The biomechanical environment of the fracture site is mainly affected by the stiffness of the bone plate. In the design of the bone plate, sufficient fixation stability is often selected as the design objective, in which mechanical indexes such as stress, 27 strain, 28 or displacement 29 are usually the evaluation criteria of fixation stability. However, sufficient fixation stability may fail to produce the level of biomechanical stimulation required for fracture healing. ...
The biomechanical stimulus is the most important factor for fracture healing and mainly determined by the structural stiffness of bone plate. Currently, the materials commonly used in bone plates are stainless steel and titanium, which often lead to stress shielding effects because of their higher elastic modulus compared with the bone. This paper suggests an optimal design method of lattice bone plate based on fracture healing theory. Firstly, the mechanical regulation model with deviatoric strain is established to simulate the tissue differentiation process during fracture healing process. The ratio of the average elastic modulus of callus at the 120th day to the elastic modulus of mature bone is used to characterize the fracture healing rate. Secondly, the optimal elastic modulus of the design domain is obtained by the optimization mathematical model with the maximum fracture healing rate. Then, the design domain is filled with microstructures, the porosity of which is adjusted to make it possible that the equivalent elastic modulus is equal to the optimized value. And the finite element analysis of the bone plate with microstructure is executed. Finally, the designed lattice bone plates are manufactured through 3D printing, and the mechanical test is carried out. The simulation results indicate that the fracture healing rate is maximum when the elastic modulus of material in design domain is 38GPa under the constraints of fixation stability. And both the finite element analysis and experiment results show that the designed lattice bone plate meet the strength requirements of fracture internal fixation implants. This article is protected by copyright. All rights reserved.
... First, locking screw bridging the fracture gap; plate-bone distance of more than 5mm; plate material, dimension and shape; screw configuration; plate length and working length; mis-insertion; and angulated insertion of the screwhead can cause the implant-related radial collapse and failure [4][5][6][7][8][9][10][11] . In addition, fracture configuration and screw-bone interface can pose bone-related failure 5,12,13 . ...
INTRODUCTION: The purpose of this study is the evaluation of radial collapse, based on the number of screws used in the metaphyseal region and by distal dorsal distance (DDD) and lunate facet distance (LFD) measurement.
MATERIALS AND METHODS: Between 2015 and 2019, 60 patients who were being treated with volar locking plates due to isolated distal radius fracture were evaluated. Control radiographs were taken on the first day and at 3rd-, 6th- and 12th-month follow-ups. Distal dorsal cortex distance and lunate facet distance were measured in the lateral radiographs. The number of screws used in the metaphyseal region was also evaluated. According to the number of screws, the amount of collapse was analysed based on both the LFD and the DDD.
RESULTS: The mean age of patients was 43.5±12.7 years. Thirty-three of the patients included in the study were male and 27 were female, and the minimum follow-up period was one year. According to the mean number of screws, groups were defined as up to 6 screws or 7 screws and above. There was a statistically significant difference between the groups in terms of DDD collapse at the 6th-month and 12th-month follow-ups (p
... where ρ is the apparent density (g/cm 3 ) and E is the elastic modulus (MPa). The elastic modulus values of the cortical bone and prosthesis were assigned to be 12 GPa and 110 GPa, respectively, while the Poisson ratios of the cortical bone and the prosthesis were both assigned to be 0.3 [6,18,19]. The base of the ulna was fixed in all degrees of freedom. ...
Background:
Comminuted fractures of the coronoid process significantly compromise the stability and function of the elbow joint. Reconstruction of the coronoid process with a prosthesis has been suggested as an alternative to restore the architecture. The purpose of this study was to investigate the strength and stability of various methods for the fixation of a coronoid prosthesis by finite element analysis.
Materials and methods:
A coronoid prosthesis was designed based on the morphological information from computed tomography images acquired from 64 subjects in whom the top 40% of the coronoid process height was replaced. Four methods for the fixation of the prosthesis were suggested: (1) a double 2.0-mm fixation bolt, anterior to posterior; (2) a double 2.5-mm fixation bolt, anterior to posterior; (3) a single 4.0-mm fixation bolt, posterior to anterior; (4) a single 4.5-mm fixation bolt, posterior to anterior. The integrated prosthesis-bone constructs were analyzed via the finite element analysis of 10 simulated proximal ulna models with loading applied along the axis of the humerus and with three different elbow flexion angles (30°, 90°, and 130°). The maximum principal stress and the total deformation were quantified and compared.
Results:
A coronoid prosthesis was developed. The maximum principal stress of the fixation bolts occurred around the neck of the fixation bolt. For a comparison of the strengths of the four fixation methods, the maximum principal stress was the lowest for fixation using a single 4.5-mm fixation bolt. The value of the maximum principal stress significantly decreased with increased elbow flexion angle for all fixation methods. The maximum deformation of the fixation bolts occurred at the head of the fixation bolt. For a comparison of the maximum deformations in the four fixation methods, the maximum deformation was the lowest for fixation using a single 4.5-mm fixation bolt. The value of the maximum deformation significantly decreased with increased elbow flexion angle for all fixation methods.
Conclusions:
The present study suggested that fixation of a coronoid prosthesis with a single 4.5-mm fixation bolt from posterior to anterior is an excellent option in terms of the strength and stability. Level of Evidence Experimental study.
... Groups with three screws at the proximal segment (X126 and N126) were chosen for the greater stiffness and fewer strain that could reduce the systematic error. In clinical practice, such fractures are often fixed with three screws on each side of the fracture gap to achieve good stability [19][20][21][22].When comparing the distance in case of the three screws with different arrangements, the results showed that when the middle screw was far from the fracture line, the overall stiffness and the near cortical strain decreased significantly (p < 0.05). These results are similar to those reported by Stoffel et al. [23]. ...
Abstract Objective A micromotion-based balanced drilling system was designed based on a locking plate (LP) and far cortical locking (FCL) concept to maintain the balance of micromotions of the cortex on both sides of a fracture region. The system was tested by axial compression test. Methods The fracture gap was set to 2 cm, and locking screws with a diameter of 5 mm and a locking plate were used to fix it. The diameters of the two sections of the stepping drill were 3.5 mm and 5.0 mm, respectively. One of the matching drilling sleeves was a standard sleeve (eccentricity, 0 mm) and the other was an eccentric sleeve (proximal eccentricity, 1 mm). A model of the fixed locking plate (AO/ASIF 33-A3) for distal femoral fractures with a gap of 2 cm was established based on data from 42 artificial femurs (SAWBONE). According to the shape of the screw holes on the cortex, the fixed fracture models were divided into a control group (standard screw hole group X126, six cases) and an experimental group (elliptical screw hole group N, 36 cases). The experimental group was further divided into six subgroups with six cases in each (N126, N136, N1256, N1356, N12356, N123456), based on the number and distribution of the screws on the proximal fracture segment. The control, N126, and N136 groups were subjected to an axial load of 500 N, and the other groups were subjected to an axial load of 1000 N. The displacements of the kinetic head, far cortex, and near cortex were measured. The integral structural stiffness of the model and the near cortical strain were calculated. The data of each group were analyzed by using a paired t-test. Results When the far cortical strains were 2%, 5%, and 10%, the near cortical strains in group N126 were 0.96%, 2.35%, and 4.62%, respectively, significantly higher than those in the control group (X126) (p
... To broaden its application to diverse clinical cases and prove its effectiveness through quantitative analysis, this surgical procedure has been vigorously investigated [9][10][11] with a focus on the design of the LCP and on the appropriate number of screws for preventing bone loss [12][13][14][15][16]. The existing literature shows that placement of a calcar screw in the lower part of the proximal humerus can help achieve safe and stable fixation; using calcar screws particularly make sense in case of a fracture in which there is unstable medial support of the proximal humerus caused by the varus of humeral head. ...
This study proposes a finite element analysis (FEA) model for complex fractures at the osteoporotic proximal humerus and investigates the relevance of using a calcar screw in surgical treatments using this model. Two types of three-dimensional (3D) fracture models of patients with osteoporotic humerus were constructed reflecting the mechanical properties of the osteoporotic humerus, such as the Young’s modulus and Poisson’s ratio, and two load conditions mimicking the clinical environment were applied for simulation. Using the 3D models and the conditions, the FEA software calculated the concentration and distribution of stresses developing in the humerus, locking compression plate (LCP), and screws. Then, we evaluated and predicted the fixed state of a LCP system depending on whether the maximum stress value exceeded tensile strength. When axial force was applied, insertion of the calcar screw led to significant reduction of stress applied on screws in the fracture model having a medial gap by approximately 61%, from 913.20 MPa to 351.84 MPa. Based on the results, it was clearly confirmed that using of calcar screws improved the stability of a three-part fractures and simultaneously reinforced medial support.
... However, bone plating guidelines are difficult to follow in some fractures with small fragments. Therefore, it has been suggested that with locking fixation, two screws on each side of the fracture should be sufficient to achieve stability (Stoffel et al., 2003). The locking T-plates are useful for the shorter distal bone fragments which allows the placement of two locking screws in the same level of the bone fragment. ...
Abstract: Metacarpal (MC) and metatarsal (MT) fractures are common in small animal medicine in cats and dogs. Conservative and surgical methods have been described for treatment. This study was aimed to evaluate the diagnosis, treatment, and prognosis of 32 cases (22 cats, 10 dogs) with MC/MT fractures. The demographic and diagnostic information of the patients, procedures (before, during and after the operation), treatments applied, and prognosis findings are within the scope of the study. Ninety-seven bones with MC/MT fractures were most at diaphyseal 1/3 (43 bones) and distal 1/3 (48 bones) localizations. The most common fracture types were transverse (65) and oblique (27). The fractures of 39 extremities were single bone fractures in 25.64%, two bones in 20.51%, three bones in 33.33%, and four bones in 20.51%. Treatment methods were external coaptation in 11 extremities, surgical osteosynthesis in 23 extremities, cage rest in four extremities, and amputation in one extremity. It was determined that the prognosis was excellent in 19 of 23 extremities that underwent surgical osteosynthesis, good in three, and postoperative death occurred in one case. Out of 11 extremities with external coaptation, six were excellent, and five were good. It was determined that two of the four extremities treated with cage rest were very good, one was good, and one was moderate. This study has evaluated the treatment of metacarpal and metatarsal fractures in cats and dogs in terms of diagnostic and clinical results, and original data were presented. Conservative treatment is considered successful in fractures if closed, not dislocated, without weight-bearing bones on the metacarpal and metatarsal bones or if only one MC/MT bone is fractured. However, it was shown that surgical osteosynthesis is essential if the fractures are dislocated, and the two or more weight-bearing bones are affected.
Keywords: Extremity, Intramedullary pin, Orthopedics, Osteosynthesis, Veterinary.
... However, bone plating guidelines are difficult to follow in some fractures with small fragments. Therefore, it has been suggested that with locking fixation, two screws on each side of the fracture should be sufficient to achieve stability (Stoffel et al., 2003). The locking T-plates are useful for the shorter distal bone fragments which allows the placement of two locking screws in the same level of the bone fragment. ...
Radial and ulnar fractures are common in small animals. Especially toy and miniature breed dogs are at high risk of incidence. Although there are plenty of studies on the treatment of radius and ulna fractures in small animals, studies related to the radius and ulna fractures in toy and miniature breed dogs are limited. The objective of this study was to report the diagnostic information and treatment outcome of radial and ulnar fracture treatment in toy and miniature breed dogs. Radius and ulna fractured 22 toy and miniature breed dogs were included in the study. Clinical findings, radiographic images, treatment applications, prognosis and outcomes were evaluated. As a treatment method, external coaptation in 5 extremities and surgical reduction and osteosynthesis in 17 extremities were performed. Out of 5 dogs who underwent external coaptation, 4 had good outcome and 1 had malunion. Out of 17 patients which underwent surgical treatment, 13 had a good outcome, 2 had nonunion, 1 had surgical site infection, and 1 had malunion and implant failure. As a result, original data on the etiology, diagnosis, treatment, prognosis evaluations, and surgical outcomes of radius and ulna fractures of toy and miniature breed dogs were presented. External coaptation considered could be successful in closed and undislocated radius and ulna fractures of toy and miniature breed dogs. However, the surgical approach and osteosynthesis performing are considered essential in dislocated, comminuted, complicated fractures, or open fractures. Further prospective studies are needed to compare specific surgical treatment methods.
... Hence, using a longer plate and inserting enough numbers and appropriate length of screws into each fragment is crucial to prevent plate breakage and to obtain a mechanically strong fixation. Especially in the helical plate fixation for the humerus, inserting as many screws as possible into the proximal fragment and at least four bicortical screws into the distal fragment is necessary to resist rotation [13]. ...
Introduction
AND IMPORTANCE: A re-nonunion after failed intramedullary nailing for a nonunion of the humeral shaft and a peri-implant distal humeral fracture with an ununited humeral shaft are rare cases. Therefore, no consensus has been established regarding the treatment strategies.
Case presentation
Case 1: An 84-year-old woman presented with humeral shaft re-nonunion after intramedullary nailing. The images revealed callus formation and loosening of the implant, suggesting a lack of mechanical stability. Nail removal and helical plating were performed. One year postoperatively, bony union was achieved. Case 2: A 59-year-old woman presented with a peri-implant distal humeral fracture with an ununited humeral shaft after nailing. Nail removal and helical plating were performed using a minimally invasive plate osteosynthesis (MIPO) technique. The distal humeral fracture was fixed with plates. One year postoperatively, bony union was achieved.
Clinical discussion
Imaging findings in Case 1 indicated that nonunion was caused by a lack of mechanical stability. In Case 2, stabilization of the ununited humeral shaft was also needed. Helical plating provides a mechanically strong fixation and prevents damage to the radial nerve and soft tissues.
Conclusion
Evaluating the causative factors of nonunions is important. Helical plating provides mechanical stability and is associated with bony union without autologous bone grafting for a re-nonunion of humeral shaft lacking mechanical instability. For a peri-implant distal humeral fracture with an ununited humeral shaft, helical plating with the MIPO technique provides diaphyseal fracture union and enables the minimal length of distal humeral plate fixation.
... single-beam constructs and offer many advantages, such as decreased need for accurate plate contouring, reduced screw loosening and improved fracture site stability or preservation of periosteal blood supply beneath the plate. [1][2][3] The stability of the locking construct depends not only on the material, design and size of the implants but also on the strength of the locking mechanism. [4][5][6] Two main factors that influence the locking mechanism strength and durability can be recognized; additionally, both are directly influenced by the surgical technique. ...
Objective The aim of this study was to evaluate the effect of screw insertion angle and insertion torque on the mechanical properties of a 3.5 fixed-angle locking plate locking compression plate (LCP) and 3.5 variable-angle locking plate polyaxial locking system (PLS).
Methods In the LCP group, screws were placed abaxially at 0, 5 and 10 degrees. In the PLS group, screws were placed at 0, 5, 10, 15 and 20 degrees abaxially. The insertion torque was set to 1.5 and 2.5 Nm in the LCP and PLS groups respectively. A load was applied parallel to the screw axis, and the screw push-out force was measured until the locking mechanism was loosened.
Results The 3.5 LCP showed higher push-out strength than the 3.5 PLS when the screws were placed at 0 degree regardless of the insertion torque. The off-axis insertion of 3.5 LCP locking screws resulted in a significant decrease in push-out strength (p < 0.05). A higher insertion torque value significantly increased the screw holding strength for the 3.5 LCP (p < 0.05). The 3.5 PLS system had a significantly higher push-out force when the screws are at 0 degree than at 5, 10 and 15 degrees, and 20 degrees (p < 0.05) at any given insertion torque. An increase in the insertion torque did not have a significant effect on the push-out strength of the 3.5 PLS locking system.
Conclusion The 3.5 PLS is more sensitive to the screw insertion angle than to the insertion torque, whereas the 3.5 LCP is affected by both factors. Placing 3.5 LCP locking screws off-axis significantly reduces the screw holding strength; therefore, this approach has to be avoided. The findings of our research indicate that a 1.5 Nm torque can be used for a 3.5 PLS.
... Distal femur fractures present a considerable challenge in the treatment. They are due to high energy trauma with extensive soft tissue damage with articular and metaphyseal involvement and also ligamentous involvement of the knee joint [1]. Older patients, especially women, sustain fractures due to osteoporosis. ...
The femur is the largest bone in the body connecting between the tibia and pelvic bone. Studies have proved this bimodal distribution of supracondylar fractures of the femur. The locking plate's standard is to have an anatomical reduction of the bone under the soft tissue envelope and could be applied without stripping the periosteum. The aim: to study the union rates with locking compression plates and clinical outcome associated with this treatment modality, range of movements of the knee, pain relief and return to normal activities and work. Methodology: this is a prospective study on patients with distal femur fractures. Conducted at Santhiram medical college and general hospital, Nandyal from October 2018 to September 2020. All patients aged more than 18 years diagnosed with distal femur fractures. Results: in our study, around 46 % of them had Muller A1 type, followed by 23 % had Muller C1 and C2 respectively, and the remaining 13.3 % had Muller A2. Around 67 % had a Thomas splint with traction, 16.7 % had B.B. splint, 13.3 % had A/K POP slab, and the remaining 3 % had upper tibial traction with B.B. splint. The majority of the study participants, 53 %, had knee flexion more than 120 degrees. 30 %, took <16 weeks for the union, 33 %, took 16-20 weeks to complete weight-bearing, eight patients (26 %) had excellent outcomes; 21 patients (70 %) had a satisfactory outcome; one patient (3.3 %) had an unsatisfactory outcome. Conclusion: in our study, out of 30 patients, eight patients had excellent outcomes, 21 patients had satisfactory outcomes, and one patient had unsatisfactory outcomes. We conclude, open reduction and internal fixation with a locking compression plate resulted in good clinical and radiologic outcomes
In orthopedic surgery, patient-specific bone plates are used for fixation when conventional bone plates do not fit the specific anatomy of a patient. However, plate failure can occur due to a lack of properly established design parameters that support optimal biomechanical properties of the plate.This review provides an overview of design parameters and biomechanical properties of patient-specific bone plates, which can assist in the design of the optimal plate.A literature search was conducted through PubMed and Embase, resulting in the inclusion of 78 studies, comprising clinical studies using patient-specific bone plates for fracture fixation or experimental studies that evaluated biomechanical properties or design parameters of bone plates. Biomechanical properties of the plates, including elastic stiffness, yield strength, tensile strength, and Poisson’s ratio are influenced by various factors, such as material properties, geometry, interface distance, fixation mechanism, screw pattern, working length and manufacturing techniques.Although variations within studies challenge direct translation of experimental results into clinical practice, this review serves as a useful reference guide to determine which parameters must be carefully considered during the design and manufacturing process to achieve the desired biomechanical properties of a plate for fixation of a specific type of fracture.Graphical Abstract
Background and objectives:
The healing outcomes of distal radius fracture (DRF) treated with the volar locking plate (VLP) depend on surgical strategies and postoperative rehabilitation. However, the accurate prediction of healing outcomes is challenging due to a range of certainties related to the clinical conditions of DRF patients, including fracture geometry, fixation configuration, and physiological loading. The purpose of this study is to investigate the influence of uncertainty and variability in fracture/fixation parameters on the mechano-biology and biomechanical stability of DRF, using a probabilistic numerical approach based on the results from a series of experimental tests performed in this study.
Methods:
Six composite radius sawboneses fitted with titanium VLP (VLP 2.0, Austofix) were loaded to failure at a rate of 2 N/s. The testing results of the elastic and plastic behaviour of the VLP were used as inputs for a probabilistic-based computational model of DRF, which simulated mechano-regulated tissue differentiation and fixation elastic capacity at the fracture site. Finally, the probability of success in early indirect healing and fracture stabilisation was predicted.
Results:
The titanium VLP is a strong and ductile fixation whose flexibility and elastic capacity are governed by flexion working length and bone-to-plate distance, respectively. A fixation with optimised designs and configurations is critical to mechanically stabilising the early fracture site. Importantly, the uncertainty and variability in fracture/fixation parameters could compromise early DRF healing. The physiological loading uncertainty is the most adverse factor, followed by the negative impact of uncertainty in fracture geometry.
Conclusions:
The VRP 2.0 fixation made of grade II titanium is a desirable fixation that is strong enough to resist irreparable deformation during early recovery and is also ductile to deform plastically without implant failure at late rehabilitation.
When obtaining surgical fixation of lateral malleolus fractures, a cortical lag screw is commonly used to obtain anatomic reduction. Subsequently, a neutralization plate is applied. Slight loss of fracture reduction after plate placement occasionally occurs. Although this is frequently attributed to poor bone quality or suboptimal initial lag screw fixation, a frequently overlooked factor is screw order when applying the neutralization plate. The purpose of this technique tip is to highlight the biomechanical rationale behind this loss of reduction and advocate a specific screw order for lateral malleolus fixation.
Objective:
The aim of this study was to determine the effect of plate-bone distance (PBD) and working length on 2.0-mm locking compression plate (LCP) stiffness and strain in four-point bending and torsion in a diaphyseal fracture gap model.
Study design:
A total of 54 LCP with three screws per fragment were assigned to one of nine combinations of working length (WL; short, medium, and long), and PBD (1, 1.5, and 3 mm) for a sample size of six per construct configuration. Stiffness was measured under quasistatic, nondestructive four-point compression bending and torsion. Plate surface strain was recorded using three-dimensional (3D) digital image correlation during four-point compression bending.
Results:
WL had a significant effect on overall construct stiffness in both compression bending and in torsion, with shorter WL constructs having higher stiffness (p < 0.0001). PBD had no effect on construct stiffness in compression bending; however, a significant reduction in stiffness was noted in torsion (p = 0.047) as PBD incrementally increased. WL had a significant effect on plate strain in compression bending, with shorter WL constructs having lower plate strain (p < 0.0001). PBD had no effect on plate strain in compression bending except for lower plate strain recorded in long WL constructs with 1-mm PBD, compared with 1.5- and 3-mm PBD constructs (p < 0.0001).
Conclusions:
Longer WL constructs, regardless of PBD, had lower stiffness in compression bending, while in torsion, some modulation of this effect was noted with incremental decreases in PBD. Longer WL resulted in high plate strain, regardless of PBD.
Clinical findings, manufacturer instructions, and surgeon's preferences often dictate the implantation of distal femur locked plates (DFLPs), but healing problems and implant failures still persist. Also, most biomechanical researchers compare a particular DFLP configuration to implants like plates and nails. However, this begs the question: Is this specific DFLP configuration biomechanically optimal to encourage early callus formation, reduce bone and implant failure, and minimize bone "stress shielding"? Consequently, it is crucial to optimize, or characterize, the biomechanical performance (stiffness, strength, fracture micro-motion, bone stress, plate stress) of DFLPs influenced by plate variables (geometry, position, material) and screw variables (distribution, size, number, angle, material). Thus, this article reviews 20 years of biomechanical design optimization studies on DFLPs. As such, Google Scholar and PubMed websites were searched for articles in English published since 2000 using the terms "distal femur plates" or "supracondylar femur plates" plus "biomechanics/biomechanical" and "locked/locking," followed by searching article reference lists. Key numerical outcomes and common trends were identified, such as: (a) plate cross-sectional area moment of inertia can be enlarged to lower plate stress at the fracture; (b) plate material has a larger influence on plate stress than plate thickness, buttress screws, and inserts for empty plate holes; (c) screw distribution has a major influence on fracture micro-motion, etc. Recommendations for future work and clinical implications are then provided, such as: (a) simultaneously optimizing fracture micro-motion for early healing, reducing bone and implant stresses to prevent re-injury, lowering "stress shielding" to avoid bone resorption, and ensuring adequate fatigue life; (b) examining alternate non-metallic materials for plates and screws; (c) assessing the influence of condylar screw number, distribution, and angulation, etc. This information can benefit biomedical engineers in designing or evaluating DFLPs, as well as orthopedic surgeons in choosing the best DFLPs for their patients.
Objective:
To determine whether deficient early callus formation can be defined objectively based on association with an eventual nonunion and specific patient, injury, and treatment factors.
Methods:
Final healing outcomes were documented for 160 distal femur fractures treated with locked bridge plate fixation. Radiographic callus was measured on postoperative radiographs until union or nonunion had been declared by the treating surgeon. Deficient callus was defined at 6 and 12 weeks based on associations with eventual nonunion via receiver operator characteristic analysis (ROC). A previously described computational model estimated fracture site motion based on the construct employed. Univariable and multivariable analyses then examined the association of patient, injury, and treatment factors with deficient callus formation.
Results:
There were 26 nonunions. Medial callus area at 6 weeks < 24.8 mm2 was associated with nonunion (12 of 39, 30.8%) vs. (12 of 109, 11.0%), p = 0.010. This association strengthened at 12 weeks with medial callus area < 44.2 mm2 more closely associated with nonunion (13 of 28, 46.4%) vs (11 of 120, 9.2%), p < 0.001. Multivariable logistic regression analysis found limited initial longitudinal motion (OR 2.713 (1.12 to 6.60), p = 0.028)) and Charlson Comorbidity Index (1.362 (1.11 to 1.67), p = 0.003) were independently associated with deficient callus at 12 weeks. Open fracture, mechanism of injury, smoking, diabetes, plate material, bridge span, and shear were not significantly associated with deficient callus.
Conclusion:
Deficient callus at 6 and 12 weeks is associated with eventual nonunion and such assessments may aid future research into distal femur fracture healing. Deficient callus formation was independently associated with limited initial longitudinal fracture site motion derived through computational modeling of the surgical construct, but not more routinely discussed parameters such as plate material and bridge span. Given this, improved methods of in vivo assessment of fracture site motion are necessary to further our ability to optimize the mechanical environment for healing.
Background
Proximal humeral shaft fractures are surgically challenging and plate osteosynthesis with a long straight plate is one operative treatment option in these patients although endangering the radial nerve distally. Helical plates potentially avoid the radial nerve by twisting around the humeral shaft. Aim of the study was to investigate in a human cadaveric model the biomechanical competence of helical plates versus straight lateral plates used for fixation of proximal third comminuted humeral shaft fractures.
Methods
Eight pairs of humeral cadaveric humeri were instrumented using either a long 90°-helical plate (Group1) or a straight long PHILOS plate (Group2). An unstable proximal humeral shaft fracture was simulated by means of a 5 cm osteotomy gap. All specimens were tested under quasi-static loading in axial compression, internal and external rotation, and bending in four directions. Subsequently, progressively increasing cyclic loading in internal rotation until failure was applied and interfragmentary movements were monitored by motion tracking.
Results
During static testing flexion/extension deformation in Group1 was significantly higher, however, varus/valgus deformation as well as shear and torsional displacement under torsional load remained statistically indifferent between both groups. During cyclic testing shear and torsional displacements were both significantly higher in Group1 compared to Group 2. However, cycles to catastrophic failure remained statistically indifferent between the groups.
Conclusions
From a biomechanical perspective, although 90°-helical plating is associated with higher initial stability against varus/valgus collapse and comparable endurance under dynamic loading, it demonstrates lower resistance to flexion/extension and internal rotation with bigger shear interfragmentary displacements versus straight lateral plating and, therefore, cannot be considered as its real alternative. Alternative helical plate designs should be investigated in the future.
Biomechanical factors is an important aspect that affects bone healing directly. Although some biologic etiologies of fixation failure can be directly affected by the physician, there are only minimally under the surgeon’s control. The surgeon should do their best to preserve soft tissue, vessel, and the zone of injury. Skillful surgical technique, tight wound closure, and appropriate antibiotic therapy could decrease the risk of infection and reduce the risk of fixation failure. If failure occurs suddenly or prior to the expected time when fracture healing would occur, a mechanical issue is usually the primary cause. Biomechanics study the role of force and energy in biological systems. The fracture fixation should follow the principle of biomechanics. Excessive stress concentration and fatigue, leading to increased pressure load and bending load, results in internal fixation failure. Understanding the biomechanical principles underlying stable fixation and failure fixation could help the surgeon determine the appropriate investigation and intervention. Appropriate biomechanical fixation technology will promote fracture healing, accelerate rehabilitation of patients, and reduce nonunion of fracture. Biomechanical study can help the design of the internal fixation and also plays an important role on the improved clinical effects; furthermore, it will help clinicians to choose reasonable diagnosis and treatment strategies.
In contemporary orthopedics, biomechanics of human motion has come to reflect the investigation of the joint’s mechanical properties throughout joint motion. This involves the stresses in the joint throughout motion, the limits of and to motion, and the interaction between these two during joint function. This chapter will discuss these properties with regard to each joint. As such, an appreciation and understanding of joint kinematics, including the native joint, the diseased joint, and the replaced joint is critical for the next stage of improvements in joint arthroplasty. This chapter will outline and discuss the current understanding of how joint kinematics change throughout common pathologies as well as following joint arthroplasty.
The treatment of extra-articular proximal tibial fractures is a therapeutic challenge due to the frequently significant soft tissue injury, the effect of the deforming forces and the need for an exact restoration of the bony alignment. Various methods of osteosynthesis are available for surgical stabilization. The locking plate osteosynthesis is the most frequently used procedure because of its good biomechanical stability, especially in osteoporotic bones, and the protection of the periosteal blood flow. Depending on the extent and stability of the defect zone, especially in the case of a medial comminuted zone and the bone quality, bilateral plate osteosynthesis can be necessary. If the proximal fragment is big enough, closed reduction and intramedullary nailing are possible. In the case of severely compromised soft tissue or very short epiphyseal fragments, the construction of an external fixator, e.g. hybrid external fixator, is recommended, which also allows definitive treatment under early full weight bearing. The most important complications are axial and torsional malalignments.
Background: With the rise in the incidence of proximal tibia fractures in India due to road traffic accidents, this prospective study was intended to assess the operative procedure in the management of such fractures using the locking compression plate (LCP).
Methods: 30 subjects attending the study site scheduled to undergo the defined surgery were enrolled as per the study selection criteria.
Results: A total of 30 patients with proximal tibia fractures were enrolled. Majority of cases were due to RTAs, with a higher incidence of types IV, V and VI. Average time for union of fracture ranged from around 16-24 weeks. 23 patients were treated with ORIF and 7 patients were treated with MIPO technique. Three different principles of fixation were done using the LCP, viz. compression, bridging and combined. Functional outcome was evaluated, which revealed excellent results in 53.33% patients, good results in 30% patients, fair results in 13.33% results, while 3.33% had poor outcomes.
Conclusions: Based on the findings of the present study we can conclude that overall Locking Compression plate (LCP) for fractures of the proximal tibia is a useful adjunct in the management of trauma patients. The locking compression plate system with its various type of fixation act as a good biological fixation including difficult fracture situations.
Keywords: Tibia fracture, Locking compression plate, Proximal tibia
Background The choice of surgical options for open tibial fractures and closed tibial fractures with soft tissue problems has been controversial.Supra-cutaneous locking plate fixation may be able to provide an personalized treatment plan.
Methods After retrospective analysis of the clinical database, we collected data on 19 patients identified as having chronic osteomyelitis after routine surgery for tibial fractures or open tibial fractures.All patients who underwent external fixation with a supra-cutaneous locking plate were followed up for 12.89±3.81 months postoperatively.Further statistical analysis was not performed because the number of cases was too small and the injuries and fracture types were different.
Results The postoperative Fugl-Meyer lower limb motor function score was 32.47±3.34 in 19 operated patients, which was evaluated according to the Mazur ankle scoring system: 11 cases were excellent, 5 cases were good, 2 cases were acceptable, and 1 case was poor, with an excellent rate of 84%. The duration of time that passed between the implantation of the supra-cutaneous locking plate and its subsequent removal ranged from 13.00±1.05 months.
Conclusions In certain tibial patients with specific indications, such as open tibial fractures without significant bone or soft tissue defect, closed tibial fractures with severe blisters or compromised soft tissue condition, and surgical site infections following tibial internal fixation with no significant bone or soft tissue defect, supra-cutaneous locking plate fixation may be used. It offers sufficient biomechanical stability for fracture repair while minimizing the inconveniences associated with bulky circular frames or external fixators.The supra-cutaneous locking plate fixation used as the final treatment may also result in a little shorter hospital stay for these individuals and lower healthcare expenses.
Background
Locking plates are commonly used in the treatment of comminuted metaphyseal distal femoral fractures. However, locking plates form a strong structure and promote asymmetrical callus formation, which is not conducive for rapid fracture healing and may increase fracture risk. To overcome this, we designed a micromotion-balancing fixation system based on locking plates.
Methods
Six healthy pigs (Bama miniature pigs) were used to establish a model of bilateral comminuted distal femoral fracture (AO/ASIF: 33-C2). Standard drilling was performed on one of each pig’s hind limbs (control group), whereas eccentric drilling was performed on the other hind limb (experimental group). Both femurs were fixed with a 3-hole locking compression plate using 5-mm-diameter screws. At 12 postoperative weeks, all pigs were euthanized and the femurs with compression plates were radiographically examined. The level of fracture healing and loosening/internal fixation failure were recorded. Bone mineral density, number of trabeculae, trabecular morphology, and calcification precipitations were assessed.
Results
All pigs survived, and the fractures healed. No complications related to fracture healing, such as infection and internal fixation failure, were noted. The bone mineral density of the near and far cortical calli, number of the near and far cortical callus trabeculae, and difference in bone mineral density between the near and far cortical calli in the experimental group were significantly higher than those in the control group (p < 0.01). However, the difference in the number of trabeculae between the near and far cortical calli was significantly lower in the experimental group than in the control group (p < 0.01).
Conclusion
This newly designed system provides stable fixation for comminuted distal femoral fracture, increases the overall strain at the fracture site, and balances the strains at the near and far cortices to achieve uniform callus growth and fracture healing.
Distal femoral fractures are fractures associated with high rates of morbidity and mortality, affecting to three different groups of individuals: younger people suffering high-energy trauma, elderly people with fragile bones and people with periprosthetic fractures around previous total knee arthroplasty. They have been classically treated with conventional plates and intramedullary nails and more recently with locked plates that have increased their indications to more types of fractures. The main objective of the present work is the biomechanical study, by means of finite element simulation, of the stability achieved in the osteosynthesis of femoral fractures in zones 4 and 5 of Wiss, by using locked plates with different plate lengths and different screw configurations, and analysing the effect of screw proximity to the fracture site. A three dimensional (3D) finite element model of the femur from 55-year-old male donor was developed, and then a stability analysis was performed for the fixation provided by Osteosynthesis System LOQTEC® Lateral Distal Femur Plate in two different fracture zones corresponding to the zones 4 and 5 according to the Wiss fracture classification. The study was focused on the immediately post-operative stage, without any biological healing process. The obtained results show that more stable osteosyntheses were obtained by using shorter plates. In the cases of longer plates, it results more convenient disposing screws in a way that the upper ones are closer to fracture site. The obtained results can support surgeons to understand the biomechanics of fracture stability, and then to guide them towards the more appropriate osteosynthesis depending on the fracture type and location.
This study presents a comparative structural finite element analysis between two different fixation methods for high-energy tibial plateau fractures: limited contact dynamic compression plate (LC-DCP) and locking compression plate (LCP). Several computational methods were employed to obtain an accurate finite element bone model with non-homogeneous properties. The goal is to evaluate the mechanical behavior of the fractured bone under each type of treatment within the scope of a single case study. Based on Computed Tomography (CT) images from the human lower limbs, the bones and implants were modeled using Computer-Aided-Design (CAD) with Autodesk Fusion 360©. Afterwards, finite element analysis was carried out in both assemblies. Altair HyperWorks© was used for pre- and post-processing the analysis and Abaqus CAE© was chosen as solver. The finite element model was built considering the boundary conditions foreseen in the specific bibliography and the assembly was submitted to a vertical compressive load based on the human Body Weight (BW). The results of both simulations were compared regarding the independent motion of the bone fragments over the fracture site. Smaller relative displacement between the bone fragments leads to shorter recovery time since this condition provides more stability and low tissue strain, which are required to generate bone. The osteosynthesis with LCP achieved the best results since it presented reduced independent motion in the fracture site, as foreseen in literature.
The presented work aims at describing some of the many applications of computational modelling (and finite element method in particular) in the field of biomechanics. More specifically, applications to the characterization of biological tissues and to the proposition of biosubstitutes will be detailed. This contribution starts with a snapshot of the numerous experimental and computational methods that have been developed in biomechanics to predict tissue behaviour and their interactions with their environment, or to propose repair solutions after an injury.
Some of my contributions in response to clinical issues (including bone reconstruction, bone tissue characterization, the proposition of ligament substitutes or the development of biomaterials for bone repair) are then detailed. In the reported work, a particular attention is paid to the confrontation of simulation results with experimental data in order to evaluate the validity of the proposed models.
Lastly, this contribution ends with the description of my future research project organized in two different axes: the first one concerns the characterization of soft fibrous tissues with original applications in the field of reproductive biomechanics, while the second on focuses on the in silico modelling and development of new bone substitutes. These research activities will be carried on in a highly multidisciplinary context, with constant connections to clinical applications.
Humeral shaft fracture is one of the most common fractures in older adults. For humeral shaft fractures, a fixed treatment is performed using a straight plate. A straight locking plate is designed such that it can be inserted at a right angle (to the fractured bone), and the screw hold angles are designed to facilitate perpendicular insertion, which may lead to nonunion, such as a pull-out or breakage. Herein, a screw was inserted to the plate, and changes in gripping force with varying angles of screw placement was investigated with an aim to optimize the incision site. Finite element analysis was used to determine the stress of plates and screws under three conditions (load, tensile, and bending) which were applied to 13 plate models with varying screw angle combined with the humeral shaft fracture model. The results showed that the von Mises stress of the plates and screws at the same pressure was the highest when both the screws were positioned at an angle of 5° to the plate at the top and bottom, rather than the conventional vertical screw insertion. In conclusion, it was confirmed that by varying the angle of the plate insertion screw to minimize the incision site, the fixation strength could be further increased. If these results are applied to actual procedures, it is expected that they will not only minimize the scope of incision for plate fixation but also reduce side effects such as bone and screw joint breakage after the procedure.
Objective:
To review the current status and progress of locking plate for the treatment of distal femoral comminuted fractures.
Methods:
The related literature was extensively reviewed to summarize the current status and progress in the treatment of distal femoral comminuted fracture with locking plate from four aspects: the current treatment situation, the shortcomings of locking plate and countermeasures, the progress of locking technology, locking plate and digital orthopedic technology.
Results:
Treatment of distal femoral comminuted fractures is challenging. Locking plates, the most commonly used fixation for distal femoral comminuted fractures, still face a high rate of treatment failure. Double plates can improve the mechanical stability of comminuted fractures, but specific quantitative criteria are still lacking for when to choose double plates for fixation. The far cortial locking screw has shown good application value in improving the micro-movement and promoting the growth of callus. The biphasic plating is a development of the traditional locking plate, but needs further clinical examination. As an auxiliary means, digital orthopedic technology shows a good application prospect.
Conclusion:
The inherent defect of locking plate is a factor that affects the prognosis of distal femoral comminuted fracture. The optimization of locking technology combined with digital orthopedic technology is expected to reduce the failure rate of treatment of distal femoral comminuted fracture.
Minimally invasive plate osteosynthesis (MIPO) in conjunction with the less invasive stabilization system (LISS) first requires reduction and retention of the fracture using such aids as external fixation, distractors, and percutaneous reduction clamps before the plate can be applied. Based on the open indirect “biological” technique of osteosynthesis, the LISS was combined with an AO distractor (LISS tractor) integrated into the LISS plate. This made reduction possible against the plate before final fixation of the LISS plate.
The LISS tractor concept was validated in three patients and we present the technique here. No malalignments >5° occurred. Fluoroscopy lasted 3.0 min (range: 2.1–4.5) and the operation 125 min (range: 90–150). Modification of the well-known LISS technique by integrating the distractor into the LISS plate to simplify reduction and to provide temporary retention of the fracture has the potential to reduce the fluoroscopy time, the operation time, the rate of malalignments, and the learning curve for this MIPO technique.
Diaphyseal fractures of the tibia in 80 patients were treated by external skeletal fixation using a unilateral frame, either in a fixed mode or in a mode which allowed the application of a small amount of predominantly axial micromovement. Patients were allocated to each regime by random selection. Fracture healing was assessed clinically, radiologically and by measurement of the mechanical stiffness of the fracture. Both clinical and mechanical healing were enhanced in the group subjected to micromovement, compared to those treated with frames in a fixed mode possessing an overall stiffness similar to that of others in common clinical use. The differences in healing time were statistically significant and independently related to the treatment method. There was no difference in complication rates between treatment groups.
We studied 99 patients who had had the fixation device removed from a healed hip fracture. During a total of 630 patient years 17 second hip fractures were observed, but only two of these were in the previously fractured hip. We conclude that the fixation device may be safely removed from a healed hip fracture.
A three-dimensional, linear finite element model was generated for an intact plexiglass tube with an attached six-hole stainless steel compression plate. We examined external forces representing axial, off-center axial, and four-point bending, along with superimposed plate and screw pretension. Strain gage experiments were conducted to test model validity and the finite element results were contrasted to a composite beam theory solution. Excellent correspondence was observed between finite element and strain gage data for the most significant strain components. Composite beam theory tended to overestimate the neutral axis shift which results from plate application. The model also demonstrated fracture site distraction due to plate pretension, and the tendency for outer screw failure for the combination of bending-closed with a preload in the plate and screws.
The results of the operative treatment of 27 humeral shaft fractures treated at the University of Louisville during a 2-year period were reviewed. The aim of this study was to analyze 1) the indications and results of surgical treatment, 2) the indications for nailing versus plating, and 3) the failures and their treatment (especially surgical nonunions). Indications for surgery were polytrauma patients (including open fractures, associated neurovascular injuries, associated ipsilateral forearm injuries) and isolated unstable fractures in which closed reduction failed. Plate and screw osteosynthesis was used in patients with proximal and distal fractures, in the presence of neurovascular injuries, progressive radial nerve palsy and failure of closed reduction due to interposition of soft tissue. Intramedullary antegrade nailing was preferentially used in polytrauma patients. Seven patients (25%) needed further surgery because of nonunion. The frequency was higher after plating (30%) than after nailing (20%), it was more common in comminuted fractures, middle third fractures and after insufficient distal locking. Exchange nailing resulted in union in 5 of the 7 cases. Although excellent results with low complication rates are reported in the recent literature following plate and screw osteosynthesis or locked intramedullary nailing, we found that operative treatment of difficult humeral shaft fractures is still fraught with a high complication rate.
Minimally invasive plate osteosynthesis (MIPO) in conjunction with the less invasive stabilization system (LISS) first requires reduction and retention of the fracture using such aids as external fixation, distractors, and percutaneous reduction clamps before the plate can be applied. Based on the open indirect "biological" technique of osteosynthesis, the LISS was combined with an AO distractor (LISS tractor) integrated into the LISS plate. This made reduction possible against the plate before final fixation of the LISS plate. The LISS tractor concept was validated in three patients and we present the technique here. No malalignments > 5 degrees occurred. Fluoroscopy lasted 3.0 min (range: 2.1-4.5) and the operation 125 min (range: 90-150). Modification of the well-known LISS technique by integrating the distractor into the LISS plate to simplify reduction and to provide temporary retention of the fracture has the potential to reduce the fluoroscopy time, the operation time, the rate of malalignments, and the learning curve for this MIPO technique.
Die Lockung Compression Plate (LCP) stellt nicht eine neue Platte dar, sondern ein Platten-Schrauben-System, welches die herkömmlichen Platten (T-, L-Rekonstruktionsplatten, sowie DCP und LC-DCP, etc.) ersetzen kann und zusätzlich die Möglichkeit der winkelstabilen Verankerung bietet. Die LCP liegt in den Dimensionen 3,5 Klein- und 4,5/5,0 Großfragmentsystem vor. Es steht das komplette Plattensortiment in diesem neuen Design zur Verfügung. Dank dem Kombinationsloch der LCP kann diese mit konventionellen, bikortikalen Knochenschrauben, mit Kopfverriegelungsschrauben oder mit einer Kombination von konventionellen und Kopfverriegelungsschrauben implantiert werden. Die Anwendung der LCP ist vorteilhaft bei Operationspflichtigen gelenknahen Frakturen am distalen Speichenende, bei Frakturen am distalen Humerusanteil, Ellbogenluxationsfrakturen, bzw. bei proximalen Oberarmfrakturen, bei Frakturen des Schienbeinkopfes, bei proximalen Tibiafrakturen, sowie Frakturen der distalen Tibia. Vorteile sind auch bei der Stabilisierung von Osteotomien gegeben. Bei MIPPO ist die LCP auch im diaphysären Bereich vorteilhaft. Die LCP stellt einen neuen AO-Standard dar.
1: Rationale.- 2: Anticipation (Preoperative Planning).- Fractures and Post-traumatic Residuals.- Osteotomies.- The Goals of Planning.- Preoperative Planning by Direct Overlay Technique: The Making of a Jigsaw Puzzle.- Preoperative Planning of an Acute Fracture Using the Sound Side: Solving the Jigsaw Puzzle.- 3: Reduction with Plates.- Using a Straight Plate as a Reduction Aid.- Reduction of a Distal Third Oblique Fracture of the Tibia by Means of an Antiglide Plate.- Fractures of the Fibula.- Forearm Fractures.- Acetabular Fractures.- Using the Angled Blade Plate as a Reduction Tool.- Proximal Femur.- Summary.- 4: Reduction with Distraction.- The Femoral Distractor.- The External Fixator in Reduction and Internal Fixation of Os Calcis Fractures.- The Minidistractor.- Summary.- 5: Substitution.- Combined Internal and External Fixation.- Composite Fixation.- Summary.- 6: Tricks.- Tricks with Instruments.- Tricks with Implants.- References.
In internal fixation devices, bone screws are used to compress the plate against the bone surface thus providing a stable fixation system capable of transmitting forces. Previous work has shown that the position of the screws and the degree of plate-hole occupation play an important part in the tor-sional rigidity of the fixation (1) and the anchorage strength between plate and bone (2).
Seven-hole 3.5 mm broad and 5-hole 4.5 mm narrow dynamic compression plates were applied to paired canine cadaveric tibias in a stable fracture model. Paired tibias were tested to acute failure in rotation and four-point bending, and to fatigue failure in four-point bending. Resistance to screw pullout was measured for three 3.5 mm cortical screws and two 4.5 mm cortical screws inserted in the configurations of the bone plates. All plate-bone systems failed by fracture of the bone through a screw hole. The 3.5 mm plate-bone system was stronger in acute failure in rotation and in four-point bending. There was no difference in stiffness, and no difference in the number of cycles to failure in fatigue testing. Three 3.5 mm screws had greater resistance to pullout than two 4.5 mm screws. Results indicate that the 7-hole 3.5 mm broad dynamic compression plate has a biomechanical advantage over the 5-hole 4.5 mm narrow dynamic compression plate.
Tensile breaking load, strength, strain, modulus of elasticity and density plus the histological structure at the fracture site, were determined for 207 standardized specimens of cortical bone from the embalmed femur, tibia, and fibula of 17 men from 36 to 75 years of age. The men were divided into a younger group (41.5 years old-avg) and an older group (71 years old-avg). Specimens from younger men had a greater average breaking load, strength, strain, modulus and density than those from older men. The percentage of spaces in the break area was greater in specimens from older men, but specimens from younger men had a slightly greater percentage of osteons, osteon fragments, and interstitial lamellae. The number of osteons/mm2 and of osteon fragments/mm2 was greater in specimens from older men but the average area/osteon and area/osteon fragment was greater in specimens from younger men. Thus, there are quantitative and qualitative differences in the histological structure of bone from younger and older men. Differences in the tensile properties of bone from younger and older men can be explained by histological differences in the bone.
The schuhli out is a device designed to lock an AO 4.5-mm cortical screw to a 4.5-mm dynamic compression plate independent of bony contact with the plate. The nut engages the screw below the plate, elevating the plate, and locking the screw at a 90 degrees angle, thus preventing toggling. Photoelastic modeling and biomechanical testing on sheep tibias were done to determine the mechanical properties of constructs using schuhli nuts. Use of schuhli nuts was shown to decrease stress in the bone below the plate. The initial axial stiffness of a construct fixed with schuhli nuts is less than a construct with standard screws, but the rate of loss of stiffness with cyclic loading is similar. When a cortical defect is present at the near cortex and the screw engages the far cortex only, the use of a schuhli nut significantly improves the stability of the construct compared with a standard screw alone, and behaves mechanically the same as a standard construct with intact cortices. This indicates that the schuhli nut acts as a substitute for a deficient cortex. The schuhli nut can be useful in osteoporotic bone because it prevents the screw from stripping the threads in the bone as the screw is advanced. It also serves to lock the screw to help prevent the screw from backing out. The schuhli nut may be a useful tool to improve stability in the treatment of complex fractures, reconstructions, or in pathologic bone.
An axisymmetric finite element code was used to predict stresses and displacements in the proximal tibia of the human knee. Joint geometries were determined from a midfrontal section of a normal lateral tibial plateau. Constitutive relations, tibiofemoral forces and joint contact areas were estimated from the literature. Fourier expansions were used to provide localized loading over the assumed contact region. The results emphasize that subchondral trabecular bone serves to transmit the large loads applied to the cartilage surface by gradually concentrating these loads into the compact bone of the tibial diaphysis. The model predicts a nearly hydrostatic stress state in articular cartilage within the contact region and high tensile principal strains at the edge of the contact region. For trabecular bone, the model predicts maximum compressive stresses beneath the center of the contact region and maximum shear stresses beneath the edge of the contact region. The predicted principal stress directions in the continuum representation for trabecular bone also bear a strong resemblance to the trabecular architecture of the lateral tibial plateau.
From January 1982 through December 1988, 150 patients with 153 Winquist Class ITI and IY comminuted diaphyseal femur fractures due to high energy blunt trauma were treated with immediate plate fixation. A total of 260 major gênerai surgical systems were injured in 150 patients. Forty-nine patients did not have adequate preoperative spine radiographs due to positioning or time factors. Nineteen patient« had spine fractures; nine were diagnosed post-femoral fixation. The average injury severity score (ISS) was 22.7. Three patients died (2%). Our institution predicted mortality with this ISS for patients without pelvic or femur fractures at 15% (P= .0003).
Six patients moved to other states and three were lost to follow up due to noncompliance. One of us reviewed 141 fractures in 138 patients at a minimum of 12 months follow up and completion of treatment. Forty-nine fractures were open; 8 grade 1, 25 grade ?, 10 grade ???, 4 ???, 2 HIC. A total of 153 pelvic or ipsilateral major orthopedic injuries were present in 141 fractures. An additional 188 major associated orthopedic injuries were noted.
The average time to union was 17.2 weeks. One plate was applied in 11° of varus. Five plates failed from fatigue and five from repeat traumas. Seven plate failures were rodded and healed within 8 weeks. There was one persistent nonunion. One fracture, open IIIC, became infected after uniting. One patient has 110° of knee motion and 140 fractures have greater than 130° of knee motion.
Plate fixation is a safe technique for immediate femoral stabilization in the face of high energy blunt trauma. Failures occur late and are easy to reconstruct Intramedullary nails are the preferred method of reconstruction. Ultimate knee function is excellent. Infection rates (1/49) in open fractures are acceptably low.
Our continuously evolving understanding of bone biology has led to a new approach to plate fixation. In comminuted fractures, anatomical reduction of all fragments is no longer a goal in itself. Preservation of the viability of the bone fragments seems to be the key to unimpaired fracture healing in internal fixation. The rapid integration of unreduced but vital fragments into the fracture callus functions as a bio-buttress system and prevents fatigue fracture of the implant. To realize the new concept of biological internal fixation, the limited contact dynamic compression plate, which minimizes vascular damage to the plated bone segment, has been developed.
Bone necrosis secondary to avascularity may not only delay or inhibit consolidation of a fracture, it may also be a cause of refracture. Both initial trauma und surgical insult will determine the extent of necrosis. Only the latter is under the surgeon's control; it can be reduced by gentle soft tissue handling and by minimizing periosteal stripping. While the impact of avascular necrosis on fracture healing is well recognized, its role in the pathogenesis of refractures has received less attention. Cortical necrosis delays bridging of gaps; these gaps act as stress risers which, following resumption of full activity or after implant removal, can lead to refracture. Evaluation of 28 refractures in 25 patients, with biopsies in 14 patients, suggests that the duration of fracture immobilization through external or internal means must be sufficiently long to allow vascular invasion of necrotic areas, their substitution by new bone and bridging of the fracture. These processes must be followed by radiographic studies prior to implant removal. Special attention needs to be paid to adequate visualization of the fracture gap on successive radiographs.
Poor clinical results with autocompression plates and six years of biochemical investigations, have led to the conclusion that a plate should not be tightened directly to a bone. Consequently, in 1979, platform screws and special autocompression plates were invented. These were later developed into the original system of stable osteosynthesis called Zespol. The system consists of a plate, platform screws, and nuts that together form a small clamp fixator. The Zespol system enables a surgeon to perform compression, neutralization (protecting) contact, and bridging osteosynthesis. In all types of osteosynthesis, the Zespol fixator can be used either internally or externally. From June 1982 through December 1988, Zespol was applied in 1295 osteosyntheses (850 fractures and 445 pseudoarthroses). The average healing time of fractures was 18 weeks, and in cases of nonunions, 21 weeks. Second operations were required in 5.1% of cases, generally with good or fair results. The overall final results were 97.9% good and fair, and 2.1% poor.
Trauma centers treat more and more patients who have sustained multiple injuries during high energy accidents. The techniques of internal fixation of such fractures may be dictated by the concomitant soft tissue trauma, rather than by the bony injury. Three stages of soft tissue injuries are recognised: Stage I delineates compromised soft tissues which may be treated with standard techniques of internal fixation, provided that further devialization by surgery is avoided. Stage II implies partial, non-circumferential destruction of soft tissues, requiring alternative techniques of internal fixation to prevent (mainly septic) complications. In stage III, the soft tissues about the fracture site are destroyed and need early, specific soft tissue reconstruction. Indirect reduction without further devascularization of bone, aiming at perfect alignment rather than anatomical reduction of extraarticular fractures, optimal rather than maximal internal fixation as well as the inclusion of soft tissue reconstructive procedures into the armamentarium of the orthopaedic surgeon, require an intellectual and technical reorientation but can be shown to improve the results of the treatment of fractures with concomitant soft tissue injury.
The effects of early physiologic dynamic compression on fracture healing were studied in the dog. Transverse midtibial osteotomies were performed bilaterally and stabilized with a relatively rigid external fixation system in a neutralization mode (800 microns) to prevent compression of the osteotomy ends during weight bearing. On the 15th day, one osteotomy in each animal was subjected to dynamic compression through weight bearing by release of the fixator-telescoping mechanism (axial dynamization), while the other side remained unchanged as the control. Analysis of sequential roentgenograms showed that the callus distribution was more symmetric on the dynamic compression side. The two sides showed no significant differences in quantitative technetium-99 bone scans or in osteotomy-site blood flow. There were no statistical differences in new bone formation, bone porosity, or maximum torque between sides. The fixation had maintained the initially created osteotomy gap on the control side and tended to unite through a gap-healing mechanism. The dynamic compression side showed reduction in gap size and union by more of a contact-healing mechanism. There were no statistical differences in the rate of pin loosening, but its distribution according to pin location was significantly different between the two sides.
Although it is known that the mechanical environment affects the fracture healing process, the optimal conditions for the different stages of healing have not been defined. In the present studies, the influence of applying a very short period of axial micromovement with defined characteristics to healing fractures has been studied both in simulated and clinical tibial fractures. The fracture healing process is seen to be acutely sensitive to small periods of daily strain applied axially within two weeks of fracture. There are boundaries of strain magnitude and force of application of applied movement that, if exceeded, inhibit the healing process. The application of appropriate applied strain to clinical tibial fractures at a time shortly after injury, when most patients would be very inactive, appears to enhance the healing process when using external skeletal fixation.
An idealized plated bone model was used to test the hypothesis that selected screw removal could alter the bone strain field and be a viable treatment for stress protection osteoporosis. Eighteen bone screw modifications were evaluated for their effects on bone strain. The three variables studied were number, position, and length of screws. Removal of two or four bone screws from an eight hole plate significantly increased the strain per load on the bone model over the values with eight screws in the plate (p less than 0.05). The four screw configurations increased bone strain more than the six screw configurations. It also was shown that the position of screws in the plate could significantly alter the bone strain per load results. Removal of six bone screws from an eight hole plate also increased the bone strain per load, but to excess in some tests. In those configurations, the results were not statistically different from the unplated configuration. Replacement of the full length screws with eight half length screws that engaged only the near cortex significantly reduced bone strain per load as compared with eight bicortical bone screws.
Grade III open tibial fractures are known for frequent complications and poor clinical results, yet published series are few and cite conflicting results. To address this dilemma, the authors report a prospective study of 202 consecutive Grade III tibial fractures. All injuries were treated under protocol at the authors' university with primary external fixation and serial debridement. Equinus deformity was prevented with a new tibiometatarsal frame extension. Severe injuries crossing the ankle or knee were temporarily stabilized with external fixation across these joints. Staged reconstruction of soft tissue and then bone was undertaken for 176 of these tibias in patients who survived their multiple injuries. Reconstructive procedures included skin grafts in 57%, muscle flaps in 32%, and bone grafts in 28%. Gastrosoleus myocutaneous flaps were successful in 92% of cases versus 66% for free flaps. Late follow-up data were obtained for 171 (97%). Infection occurred in 15% and led to amputation in 7%. The infection rate was reduced to 9% in the second half of the series largely by removal of all necrotic bone prior to wound coverage. Angulation (greater than 10 degrees) in 9% and delayed union were lessened with early posterolateral grafting followed by progressive fracture loading in the fixator. A 9% incidence of pin tract drainage or loosening was reduced with predrilling and diaphyseal half pins. The time to fixator removal averaged 87 days. Ninety-three percent of the fractures united (median time, nine months) but healing times varied widely according to the amount of tissue injury and bone loss. Eighty-nine percent had satisfactory late clinical function. Results from this study, the largest series of open Grade III tibial fractures reported to date, suggest that successful staged reconstruction is now a reasonable expectation for most of these severe injuries.
A three-dimensional finite element model of the proximal tibia has been developed to provide a base line for further modeling of prosthetic resurfaced tibiae. The geometry for the model was developed by digitizing coronal and transverse sections made with the milling machine, from one fresh tibia of average size. The load is equally distributed between the medial and lateral compartments over contact areas that were reported in the literature. An indentation test has been used to measure the stiffness and the ultimate strength of cancellous bone in four cadaver tibiae. These values provided the statistical basis for characterising the inhomogeneous distribution of the cancellous bone properties in the proximal tibia. All materials in the model were assumed to be linearly elastic and isotropic. Mechanical properties for the cortical bone and cartilage have been taken from the literature. Results have been compared with strain gage tests and with a two-dimensional axisymmetric finite element model both from the literature. Qualitative comparison between trabecular alignment, and the direction of the principal compressive stresses in the cancellous bone, showed a good relationship. Maximum stresses in the cancellous bone and cortical bone, under a load which occurs near stance phase during normal gait, show safety factors of approximately eight and twelve, respectively. The load sharing between the cancellous bone and the cortical bone has been plotted for the first 40 mm distally from the tibial eminence.
One hundred twelve comminuted or rotationally unstable fractures of the femur were treated with the Grosse-Kempf interlocking nail. Two-thirds of the fractures had comminution involving more than 50% of the cortex. Of the 112 nailings, 82 were static and 30 dynamic. Clinical and radiographic fracture union occurred in 98% of cases; there were two nonunions. There were no instances of deep wound infection or osteomyelitis. Only two patients had a change of limb length greater than 1 cm. Angulation in any plane greater than 10 degrees was noted in three patients (2.5%). External rotation deformities occurred in eight patients (7.0%). The interlocking nail has expanded the indications for the use of closed intramedullary nailing in the treatment of complex fractures of the femur. The incidence of infection and nonunion is remarkably low. Immediate stability of the fracture allows for immediate mobilization of the patient, early rehabilitation of the limb, and a shorter hospital stay.
The pattern of early healing of canine tibial osteotomies associated with two different types of external fixation devices was investigated. Two-plane fixation was significantly more rigid than one-plane fixation in three of the five loading conditions that were examined. The more rigid fixation allowed less lateral displacement at the site of the osteotomy, induced less formation of callus early in the healing process, permitted direct bridging by osteons more frequently, and provided healing that was more rigid early in the process of repair. In the later stages of healing there were no differences in the quantity of callus or in the strength of the healing bone. In this canine model, external fixation with higher rigidity resulted in rapid union that differed from the union that resulted after less rigid external fixation only with regard to porosity, torsional stiffness, and displacement at the site of the fracture.
Thirty-two plates originally used for fracture fixation in the ulna and radius in twenty-three patients were removed at Hennepin County Medical Center in Minneapolis between 1977 and 1982. The plate was on the ulna in eighteen arms and on the radius in fourteen. Removal of twenty-one plates was elective, and eleven were removed because of slight pain or discomfort. The interval between plate application and plate removal ranged from eight to sixty-two months. The average duration of cast immobilization used for protection after removal of the plate was six weeks. There were seven refractures, which occurred between two and forty weeks after plate removal. Three refractures occurred at the former fracture site; three, through the fracture site, extending into an adjacent screw-hole; and one, at one screw-hole. No refracture occurred more than forty weeks after removal of the plate.
The incidence and clinical details of refractures of the shaft of the tibia a series of 534 adult patients after conservative primary treatment were analysed. Fracture of the callus is defined as a secondary fracture occurring within twelve months of the primary injury in the area of bone healing by callus. A fracture of the callus was recorded in 13 patients (2.4 per cent), in whom 11 fractures occurred after a primary fracture caused by indirect, rotational violence. The incidence among these was 6.3 per cent. For torsional fractures of the tibial shaft the following factors were associated with appreciably increased frequency of subsequent fracture of the callus: repeated closed reduction; fracture of the fibula at a different level from that of the tibia, and marked initial lateral displacement. When these factors were present simultaneously, the incidence was 18 per cent.
Cortical bone porosis associated with the dynamic compression plate (DCP) prompted the development of the limited-contact dynamic compression plate (LC-DCP) and the point-contact fixator (PC-Fix) to increase bone vascularity. However, the comparative fixation characteristics of the three designs are unknown. Transverse fractures were physiologically created in paired cadaveric sheep tibiae, which were plated before torsion testing and four-point bending to failure. The tibiae were grouped randomly and compared as follows: DCP versus LC-DCP, DCP versus PC-Fix, and LC-DCP versus PC-Fix. Mean torque to failure demonstrated no significant difference between the three plates (p < 0.33). Mean bending stiffness, gap opening, and moment to failure also demonstrated no significant difference between the three designs with p < 0.29, < 0.13, and < 0.16, respectively. The LC-DCP and PC-Fix have torsion and bending properties comparable with the DCP in the fixation of simple transverse diaphyseal fractures.
Nailing technique has changed in recent years in some important aspects which are not limited to the omitted reaming procedure. These changes concern patient positioning, reduction technique, the use of temporary stabilizers such as the 'Pinless', and determination of implant length and diameter. Approach and exposure techniques have been modified to new, less invasive procedures, in order to fulfill technical, functional and aesthetic requirements. Techniques and tricks have been developed for avoidance of fragment diastasis and axial and torsional malalignment. Finally, simple algorithms are described for the management of large bone defects, bilateral tibia shaft or ipsilateral femoral shaft fractures, number and location of locking bolts, the 'when and how' of patient mobilization and load bearing, and primary and secondary dynamization. These algorithms, techniques and procedures were developed in a series of 152 tibia shafts, which were stabilized with the AO unreamed tibia nail (UTN) in a prospective study between March 1989 and June 1994. Of these, 75 cases with a mean follow-up of 19.4 +/- 6.3 (range 11-37) months after trauma were reviewed. Fractures were classified according to Müller (1990): 14 type A, 37 type B and 24 type C. Closed soft tissue damage was categorized according to our classification: C0/1, n = 5; C2, n = 12; C3, n = 9 (Tscherne 1982). Among 49 open fractures 8 were OI, 18 OII, 10 OIIIA and 13 OIIIB (Gustilo 1976). The main minor intraoperative complication was drill bit breakage (n = 10), most frequently at the proximal locking holes. The main postoperative complication was breakage of locking bolts (n = 16), mainly between weeks 6 and 20. Minor secondary reinterventions were, in most cases, secondary dynamization under local anaesthesia. Major reintervention were: soft tissue reconstructions (n = 5), isolated cancellous bone graft (n = 6), and change of treatment (n = 12). There were nine changes to a reamed nail, two changes, in very proximal fractures, to plate osteosyntheses. There were three deep infections. Mean time to union was 23.9 weeks (range 10-48 weeks, n = 73); in two cases non-union was observed. The overall result was judged with the Karlström-Olerud score, which was applicable in 66 of 75 cases; excellent, n = 2; good, n = 22; satisfactory, n = 24; fair, n = 9; poor, n = 9. In the remaining nine cases no scoring was attempted because of severe injuries around the knee or ankle.
The load axis of the curved-shaped proximal femur lies not inside, but outside the bone. Therefore high bending forces are acting, the medial cortex absorbing pressure, the lateral cortex absorbing tension. In a transverse fracture, a laterally applied plate will absorb the tensile stresses, the medial cortex the pressure forces. When medial butress due to bony defect is missing, the laterally applied plate is subjected to cycling bending and will undergo fatigue fracture. This dilemma is compensated by a wave-plate with bone graft: The compression forces are detoured to the lateral cortex and the plate is again subjected to tension. Furthermore since the plate is standing away from the bone, the plate does not disturb the blood supply at the fracture side and bone healing.