Article

Biomechanical testing of the LCP - How can stability in locked internal fixators be controlled?

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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.

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... Accordingly, we reproduced the osteoporotic bone model based on this CTI in this study. To reproduce subtrochanteric fracture models, transverse fracture lines at eight levels in the subtrochanteric region [0, 10,20,25,30,35,40, and 50 mm below the lower margin of the lesser trochanter and three different fracture gaps (1, 2, and 3mm) for each of the eight sites were produced on each normal and osteoporotic bone model using ABAQUS (version 6.14, Dassault Systems, Paris, France) (Fig 1). ...
... The following bone density-HU and elastic modulus-bone density relationships were used [23,24] where ρ is the apparent density (g/cm 3 ), and E is the elastic modulus (MPa). The material properties of the femoral cortical bone and nail were referenced from earlier publications ( Table 1) [25,26]. Titanium alloy (TI6Al4V) was used for the Gamma 3 CMNs for the purpose of analysis. ...
Article
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A finite element analysis was performed to evaluate the stresses around nails and cortical bones in subtrochanteric (ST) fracture models fixed using short cephalomedullary nails (CMNs). A total 96 finite element models (FEMs) were simulated on a transverse ST fracture at eight levels with three different fracture gaps and two different distal locking screw configurations in both normal and osteoporotic bone. All FEMs were fixed using CMNs 200 mm in length. Two distal locking screws showed a wider safe range than 1 distal screw in both normal and osteoporotic bone at fracture gaps ≤ 3 mm. In normal bone FEMs fixed even with two distal locking screws, peak von Mises stresses (PVMSs) in cortical bone and nail constructs reached or exceeded 90% of the yield strength at fracture levels 50 mm and 0 and 50 mm, respectively, at all fracture gaps. In osteoporotic bone FEMs, PVMSs in cortical bone and nail constructs reached or exceeded 90% of the yield strength at fracture levels 50 mm and 0 and 50 mm, respectively, at a 1-mm fracture gap. However, at fracture gaps ≥ 2 mm, PVMSs in cortical bone reached or exceeded 90% of the yield strength at fracture levels ≥ 35 mm. PVMSs in nail showed the same results as 1-mm fracture gaps. PVMSs increased and safe range reduced, as the fracture gap increased. Short CMNs (200 mm in length) with two distal screws may be considered suitable for the fixation of ST transverse fractures at fracture levels 10 to 40 mm below the lesser trochanter in normal bone and 10 to 30 mm in osteoporotic bone, respectively, under the assumptions of anatomical reduction at fracture gap ≤ 3 mm. However, the fracture gap should be shortened to the minimum to reduce the risk of refracture and fixation failure, especially in osteoporotic fractures.
... As such, prior studies reduced the stiffness of metal plates via various tactics: non-locking screws, but they can undergo pull-out from the plate [28]; optimizing screw location and number, but this requires parametric analysis [29]; increasing the "working length" distance between screws just on either side of the fracture, but this could reduce mechanical stability [29]; far cortical locking screws that "toggle", but they are thinner with higher stresses than standard screws [28,30]; dynamic screws elastically suspended to permit sliding, but the plate "pockets" housing the elastic elements can fail [28,31]; semi-rigid non-metallic screws, but they could loosen and wear more easily than metal screws [32]; and alternative plate materials like polymers and fiber-reinforced polymers, but they are not always biocompatible or hydrophobic [19,21,[33][34][35][36]. The present authors used AIM and SIM/AIM ratio as criteria to investigate semi-rigid plates for distal femurs [35]; but this has not been done for CPTF plating. ...
... As such, prior studies reduced the stiffness of metal plates via various tactics: non-locking screws, but they can undergo pull-out from the plate [28]; optimizing screw location and number, but this requires parametric analysis [29]; increasing the "working length" distance between screws just on either side of the fracture, but this could reduce mechanical stability [29]; far cortical locking screws that "toggle", but they are thinner with higher stresses than standard screws [28,30]; dynamic screws elastically suspended to permit sliding, but the plate "pockets" housing the elastic elements can fail [28,31]; semi-rigid non-metallic screws, but they could loosen and wear more easily than metal screws [32]; and alternative plate materials like polymers and fiber-reinforced polymers, but they are not always biocompatible or hydrophobic [19,21,[33][34][35][36]. The present authors used AIM and SIM/AIM ratio as criteria to investigate semi-rigid plates for distal femurs [35]; but this has not been done for CPTF plating. ...
Article
Comminuted proximal tibia fractures are an ongoing surgical challenge. This “proof of concept” study is the first step in designing a new percutaneous plate for this injury under toe-touch weight-bearing as prescribed after surgery. Finite element simulations generated design curves for overall stiffness, bone and implant stress, and interfragmentary motion using 3 fixations (no, 1, or 2 “kickstand” (KS) screws across the fracture gap) over a range of plate elastic moduli (EP = 5 to 200 GPa). Combining well-established optimization criteria to enhance callus formation (i.e. 0.2 mm ≤ axial interfragmentary motion ≤ 1 mm; shear / axial interfragmentary motion ratio < 1.6), lessen stress shielding (i.e. bone stress under the proposed plate > bone stress under a traditional titanium or steel plate), and reduce steel screw breakage (i.e. screw max stress < ultimate tensile stress of steel) resulted in plate design recommendations: 172.6 ≤ EP < 200 GPa (no KS screw), 79.8 ≤ EP < 100 GPa (1 KS screw), and 4.9 ≤ EP < 100 GPa (2 KS screws). A prototype plate could be made from materials currently used or proposed for orthopaedics, such as polymers, fiber-reinforced polymers, fiber metal laminates, metal foams, or shape memory alloys.
... In addition to regaining length, apposition, and axial alignment, achieving normal rotational alignment and the radial bow is necessary to restore good range of supination and pronation of the forearm [1] . However, Stoffel et al. [2] showed that plate osteosynthesis with rigid fixation has shown a high complication rate including delayed or nonunion, infection, hardware failure and most importantly refracture after plate removal, primarily due to necrosis of bone under the plate. The locking compression plate is latest in a long sequence of basic improvements in AO technology. ...
... Diaphyseal fracture of ulna and radius present specific problems in addition to those common to all fractures of shaft of long bones due to their anatomical characteristics and conservative treatment of these fractures lead to poor functional outcome. Stoffel et al. [2] showed that plate osteosynthesis with rigid fixation has shown a high complication rate including delayed or nonunion, infection, hardware failure and most importantly refracture after plate removal, primarily due to necrosis of bone under the plate. ...
... Therefore, plates are more commonly used for femoral fracture fixation and have become effective devices for treating fracture. Biological (BO) fixation [3] advocates to protect the surrounding blood supply by reducing the contact between the implant and bone, so as to protect the soft tissue around the fracture, which is helpful to achieve the secondary healing of fracture. With the continuous evolution of plate technology, many types of plate products are introduced, such as limited contact dynamic compression plate (LC-DCP), point contact plate (PC-Fix), bridging plate (BP), locking compression plate (LCP) and minimally invasive fixation system (LISS). ...
... The bone plate design for proximal intertrochanteric fractures was tested using a simulated fracture (AO/ OTA-31A3 type) mesh model as input. Based the method suggested in our previous study [3], several valid anatomic feature parameters of the fractured model were measured including femoral head radius (20.246 mm), distal length (207.882 mm), and anterior and posterior diameter of the condyle (55.911 mm). ...
Article
Full-text available
Personalized anatomic plate is used in the surgical treatment of femoral fracture for the good matching between individual femur and plate. However, the development process of personalized plate is time-consuming and laborious at present due to anatomic and fracture differences between individuals. To improve the efficiency and quality of plate design, this study proposes an integrated computer-aided approach for parametric investigation of anatomic plate design. Based on the constraint deformation of femur template, a reference model was constructed, and major fracture segments were quickly restored to each original anatomic region by rigid registration to the reference model. The experimental results indicate that personalized anatomic plates can be constructed and edited quickly and intuitively with semantic parameters in high level, and contribute to the improvement of design efficiency and quality of customized plates for individuals.
... 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. ...
Article
Full-text available
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. ...
Article
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.
... As more and more concepts about biological fixation become clearer the innovation of plates progressed and lead to the development of less invasive stabilizing system. Research to combine these two methods has lead to the development of the anatomically contoured locking compression plate [6] . ...
... Indirect closed reduction and extra periosteal dissection in MIPO technique with bridging long plate provide anatomic alignment and relative stability, which enables limited motion at the fracture site that creates secondary bone healing with callus formation [9] . In-vitro biomechanical studies have made recommendations that the long plates with limited number of screws are essential to achieve a sound, flexible fixation and to reduce implant failure [10] . We also found good callus formation in the fracture site. ...
... Distal tibial fractures usually result from high-velocity injuries with significant violation of the inherently deficient soft tissue envelope in this area. Consequently, operative treatment of fractures in this area by conventional ORIF is expected to cause further compromise to the soft tissue envelope [29]. In this study, 11 cases developed deep infections with skin dehiscence and exposure of the hardware, and nine of them had preoperative diabetes mellitus. ...
... Point-contact fix 1, later point fix 2. As more and more concepts about biological fixation became clearer, the innovation of plates progressed and lead to the development of less invasive stabilizing system. Research to combine these two methods has lead to the development of the anatomically-contoured locking compression plate [6] . This new system is technically mature as it offer numerous fixation possibilities and has proven to worth in complex fracture situations and in osteoporotic bones. ...
... More concepts of biological fixation becoming clearer, the innovation of plates progressed drastically and led to the development of less invasive stabilizing system. Many researches to combine these two methods has led to the development of the anatomically contoured locking compression plate [6] . "Three-column fracture" is defined as at least one independent articular fragment in each column [7] . ...
... 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. ...
Article
Full-text available
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.
... of diaphyseal fractures. 3 As opposed to the conventional plating system that the stability of fixation is achieved by compressing the plate to the bone, the LCP system uses the locking feature of the plate and screws to stabilize the fracture. 4 Numerous LCP parameters influence its functionality and durability. ...
Article
Performance of the locking compression plate (LCP) is a multi-factorial function. The control parameters of plating, such as geometries, material properties, and physical constraints of the LCP components, affect basic functions associated with the bone fixation, including the extent of stress shielding and subsequent bone remodeling, strength and stability of the bone-LCP construct, and performance of secondary bone healing. The main objectives of this research were: (1) to find the appropriate values of control parameters of an LCP construct to achieve the optimized performance throughout bone healing; and (2) to unravel relationships between LCP parameters and the LCP's performance. Different values for the plate/screw modulus of elasticity (E), plate width (W), plate thickness (T), screw diameter (D), bone-plate offset (O), and screw configuration (C), as six control parameters, were considered at five different levels. Taguchi method was adopted to create trial combinations of control parameters and determining the best set of parameters, which can optimize the overall performance of the LCP. All design cases were analyzed using the finite element method. The optimal set of control parameters consisting of 150 GPa, 12 mm, 4 mm, 5.5 mm, 2 mm, and 123,678 were determined for E, W, T, D, O, and C, respectively. Furthermore, ANOVA was used to rank the most influential parameters on each function of the LCP fixation. In the overall performance of the LCP fixation, E, D, T, C, W, and O showed a contribution percentage of 46%, 22%, 10%, 11%, 8%, and 3%, respectively. This article is protected by copyright. All rights reserved.
... With the better understanding of fracture healing biology and biomechanics of fracture fixation and healing, there is evolution of new concept of fracture fixation with fixed angular stable plate, (internal fixator, LCP) and minimally invasive surgical techniques. The trend of treatment is towards biological fixation, which can be accomplished by LCP and MIPPO technique [4] . ...
... The free working length is one of the most important factors influencing the resulting mechanobiology of a locking plate osteosynthesis. A longer working length leads to a reduced stiffness of the construct and larger interfragmentary movements in the fracture gap [43,44]. Furthermore, the comparative study determined the axial stiffness over ten cycles (cycles 10 to 19) [28][29][30]. ...
Article
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In recent years, an increase in periprosthetic femur fractures has become apparent due to the increased number of hip replacements. In the case of Vancouver type B1 fractures, locking plate systems offer safe procedures. This study compared the distal lateral femur plate (LOQTEQ®, aap Implantate AG) with a standard L.I.S.S. LCP® (DePuy Synthes) regarding their biomechanical properties in fixation of periprosthetic femur fractures after hip arthroplasty. We hypothesized that the new LOQTEQ system has superior stability and durability in comparison. Eighteen artificial left femurs were randomized in two groups (Group A: LOQTEQ®; Group B: L.I.S.S. LCP®) and tested until failure. Failure was defined as 10° varus deformity and catastrophic implant failure (loosening, breakage, progressive bending). Axial stiffness, loads of failure, cycles of failure, modes of failure were recorded. The axial stiffness in Group A with 73.4 N/mm (SD +/− 3.0) was significantly higher (p = 0.001) than in Group B (40.7 N/mm (SD +/− 2.8)). Group A resists more cycles than Group B until 10° varus deformity. Catastrophic failure mode was plate breakage in Group A and bending in Group B. In conclusion, LOQTEQ® provides higher primary stability and tends to have higher durability.
... In our study, radiological union was seen at an average of 17.35 weeks which is comparable to study of distal femur fractures by polyaxial plating by Pascarella, et al., and J B Erhardt, et al., [16,17]. Gautier, et al., described guidelines about locking compression plate in distal femur fractures and advised to put plate as a bridging plate, for communited fractures the plate length being 2 to 3 times longer than fracture length and 3 or more empty holes around fracture site while Stoffel, et al., suggested that screws should be as close to fracture site as possible [19,20]. ...
... In the present study, the authors considered that not only the bridging span but also the scattering and clustering of the proximal screws influence callus formation and fracture union. Naturally, scattering the proximal screws tends to shorten the working length and lead to increased construct stiffness, whereas clustering tends to lengthen the working length and lead to decreased construct stiffness [15]. It is generally known that extremely high or extremely low stiffness of the fixation construct could impair callus formation in the MIPO treatment [16,17]. ...
Article
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Introduction The importance of fixation construct in locking compression plate (LCP) is not well enlightened until recently. The aim of this study was to investigate radiological and clinical outcomes of scattering and clustering of the proximal screw fixation construct in unilateral LCP treatment of the distal femoral fractures. Materials and methods Patients who were treated for distal femoral fractures using unilateral LCP between January 2014 and December 2019 in our institute were included in this retrospective study. They were divided into groups 1 (35 cases, scattered proximal screw fixation) and 2 (35 cases, clustered proximal screw fixation). Mean follow-up period was 23.6 months for group 1 and 21.3 months for group 2. Medical history, patient demographics, injury characteristics, and surgical characteristics were reviewed and analyzed. Radiological findings including time to callus formation, bridging callus formation, union, and symmetry of the union were assessed and compared between the groups. Clinical outcomes included total blood loss during the operation, postoperative range of motion, and number of revision surgery. Results The time for callus formation (5.8 weeks in group 1 vs. 4.1 weeks in group 2, p = 0.009) and bridging callus formation (12.5 weeks in group 1 vs. 10.7 weeks in group 2, p = 0.009) was significantly earlier in group 2. Despite similar union rates between groups, the mean time for radiological union was longer in group 2 (10.7 vs 7.4 months, p = 0.001). Though statistically insignificant, more asymmetric union was observed in group 2 (17 vs 11 cases). Conclusions Despite a delay in initial callus and bridging callus formation, scattering the proximal screws was better in achieving earlier and more balanced radiographic union than the clustered fixation. We recommend to avoid bridging more than five holes in the whole plate fixation construct to lessen the asymmetric callus formation and to prevent eventual plate breakage
... The cortical thickness was approximately 2.5 mm and 4.5 mm in medial and post wall of this tibial site, respectively. Simulated AO/OTA 43-C1 type fracture was used in this study [10].1 mm gap was simulated between bone fragments ( Figure 1) [11]. Three distal tibial plates were involved in the current study. ...
Article
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This study compares the novel Asia Distal Lateral Tibial Locking Plate mechanical stability to that of the current anterolateral and medial tibial plates based on finite element analysis. Four-part fracture fragment model of the distal tibia was reconstructed using CAD software. A load was applied to simulate the swing phase of gait. The implant stress and the construct stiffness were compared. The results of the anterolateral plate and the medial plate were similar and the displacement values were determined lower than those in the medial plate. In the simulated distal tibia fracture, the Aplus Asia Distal Lateral Tibial Locking Plate and medial distal tibial plate tibia fixations will lead to a stiffer bone-implant construct compared to the anterolateral distal tibial plate. Moreover, the stress in the Aplus Asia Distal Lateral Tibial Locking Plate was lower than those for the medial distal tibial plate and anterolateral bone plates. The Aplus Asia Distal Lateral Tibial Locking Plate has better stabilization and is an anterolateral plate that avoids more soft tissue damage than other bone plates. The Aplus Asia Distal Lateral Tibial Locking Plate could be one of a suitable design in tibia distal fracture fixation.
... More concepts of biological fixation becoming clearer, the innovation of plates progressed drastically and led to the development of less invasive stabilizing system. Many researches to combine these two methods has led to the development of the anatomically contoured locking compression plate [6] . "Three-column fracture" is defined as at least one independent articular fragment in each column. ...
... 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. ...
Article
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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.
... The stability and biomechanical properties of large fragment locking plate constructs have been studied and well described. The working length (the distance of the first screw to the fracture site), the number of screws, and the distance of the plate to the bone are all known to effect the axial stiffness and torsional rigidity of the construct [16]. Locking hole inserts, also known as threaded screw head inserts, have been evaluated to determine whether or not filling the empty locking holes changes the properties of the plate once all screws have been placed. ...
Article
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Purpose The study was to determine the effect of locking hole inserts and their insertion torque on the fatigue life of a large fragment Locking Compression Plate (LCP) under bending forces. Methods Fatigue strength of the LCP was examined using cyclic three-point bend testing at 80% yield strength of the construct. Locking hole inserts were used in 2, 4, and 6-hole of a 12-hole plate to simulate three different working lengths. Within each working length, plates were tested without locking inserts serving as the control group. In the experimental groups, inserts were tightened to manufacturer recommendations (4 Nm) and using overtorque (8 Nm). Results Significantly fewer cycles to failure were observed in control groups versus the locking hole insert groups for all working lengths (2-hole: 4 Nm p = 0.003, 8 Nm p = 0.003; 4-hole: 4 Nm p = 0.02, 8 Nm p < 0.001; 6-hole: 4 Nm p = 0.004, 8 Nm p < 0.001). There was a statistically significant increase in fatigue strength when using overtorque in the 4-hole ( p = 0.04) and 6-hole ( p = 0.01) defect groups. This was not shown in the 2-hole defect group ( p = 0.99). Conclusions By placing locking inserts in the empty locking regions of Combi holes along the working length, the number of cycles to failure was increased. Tightening inserts to twice the recommended insertion torque further increased cycles to failure in longer working length models. A longer fatigue life has the potential to decease the incidence of plate failure especially in the setting of delayed union due to poor intrinsic healing capacity, fractures in the geriatric population, osteoporosis and periprosthetic fractures.
... [4] Also, in the literature, there are recommendations indicating that the distance between the plate and the bone should be as small as possible to increase its mechanical stability though locking plates do not need to be in full contact with the bone. [6,7] Manufacturers provide different plate lengths for left and right femurs. These are all unisize plates intended to fit every adult femur. ...
Article
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ABSTRACT Objectives: This study aims to investigate the fitness of two anatomic distal femoral plates with cadaveric femurs and to show whether current plates optimally match each femur. Materials and methods: Two different sets of plates with five, seven and nine shaft holes were applicated on 62 cadaveric femurs. Ball clay was molded onto the entire inner surfaces of the plates and then the plates were fixed to the bones using two self-locking nylon cable zip ties. The volume of ball clay sandwiched in between the plate and bone was calculated and used as a quantitative fit parameter. Data of each plate were analyzed separately. Results: Using Double Medical Technology Incorporated TM plates, the mean plate to bone volumes were calculated as 8.4 mL (range, 5-14 mL), 10.0 mL (range, 6-17 mL), and 13.1 mL (range, 7-25 mL) in five, seven and nine-hole plates, respectively. Using Zimmer Biomet Incorporated TM plates, the mean volumes were 10.5 mL (range, 6-21 mL), 12.7 mL (range, 7-22 mL) and 16.3 mL (range, 8-30 mL) in five, seven and nine-hole plates, respectively. Within each group, the measurements were significantly correlated positively with femoral length. Conclusion: Optimal fit may not be achieved in each femur using current distal femoral plate implant sets. Thus additional sizes of plates should be supplied in the implant sets. Keywords: Cadaveric dry femur bone, congruency of locking plates, distal femur plate, fit assessment parameter, plate bone fit, precontoured plate fit, quantitative fit parameter. Citation: Utkan A, İğdir V, Arslan A, Şen Esmer T, Özkurt B. Fit assessment of two different anatomically contoured distal femur plate sets on cadaveric bones. Eklem Hastalik Cerrahisi 2019;30(2):137-142.
... 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. ...
Article
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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]. ...
Article
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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.
... The concave surface experiences compressive stress, and the crack does not detect here. Another example is the fracture line or crack due to torsion [6][7][8]. This leads to spiral fracture, as shown in Figure 1. ...
Conference Paper
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Qualitative flexural modulus analysis for establishing appropriateness of pig femur bone for biomedical experimentation about automatic alignment of fractured femur bone of human using controlled angular/linear incremental motion. Abstract A fracture is a lesion produced by mechanical force on the hard or mineralized tissues such as bone. In recent years the study of fracture mechanics has assumed significance owing to a rise in fracture incidence. This has been due to several reasons including-ageing population, changing dietary habits, changing work environment These developments have led to increasing use of the mechanistic approach to study fractures and use the subsequent to develop instruments and practices to prevent and heal fractures. This paper provides an overview of types of fractures and the reason for their occurrence, further we will study and compare by means of experiment fractures caused by bending load on Pig Femur with the available data. From the result obtain for Young's Modulus of pig bone and human bone the error obtained is not greater than 5%.It can be concluded that pig bones have similar properties to that of human bones and can be adequately used for the purpose of testing in biomechanical experiments. The purpose of flowchart for deformity correction bone is developed, which will be further useful for alignment of straight bone fracture of orthopedic patients.
... The material properties of the femoral cortical bone, nail, and blocking screw were studied from earlier publications (Table I). 17,18 For analytic purposes, titanium alloy (TI6Al4V) was used for the Gamma 3 nails (Young's modulus 114 GPa, Poisson ratio 0.34), and stainless steel (316 L) was used for the blocking screws (Young's modulus 147 GPa, Poisson ratio 0.29). Different material properties were assigned to different femoral regions. ...
Article
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Aims There are concerns regarding nail/medullary canal mismatch and initial stability after cephalomedullary nailing in unstable pertrochanteric fractures. This study aimed to investigate the effect of an additional anteroposterior blocking screw on fixation stability in unstable pertrochanteric fracture models with a nail/medullary canal mismatch after short cephalomedullary nail (CMN) fixation. Methods Eight finite element models (FEMs), comprising four different femoral diameters, with and without blocking screws, were constructed, and unstable intertrochanteric fractures fixed with short CMNs were reproduced in all FEMs. Micromotions of distal shaft fragment related to proximal fragment, and stress concentrations at the nail construct were measured. Results Micromotions in FEMs without a blocking screw significantly increased as nail/medullary canal mismatch increased, but were similar between FEMs with a blocking screw regardless of mismatch. Stress concentration at the nail construct was observed at the junction of the nail body and lag screw in all FEMs, and increased as nail/medullary canal mismatch increased, regardless of blocking screws. Mean stresses over regions of interest in FEMs with a blocking screw were much lower than regions of interest in those without. Mean stresses in FEMs with a blocking screw were lower than the yield strength, yet mean stresses in FEMs without blocking screws having 8 mm and 10 mm mismatch exceeded the yield strength. All mean stresses at distal locking screws were less than the yield strength. Conclusion Using an additional anteroposterior blocking screw may be a simple and effective method to enhance fixation stability in unstable pertrochanteric fractures with a large nail/medullary canal mismatch due to osteoporosis. Cite this article: Bone Joint Res 2022;11(3):152–161.
... 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. ...
Article
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.
Article
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.
Thesis
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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.
Article
Background Periprosthetic femur fractures (PFFs) that occur distal to a total hip arthroplasty (THA), Vancouver C fractures, are challenging to treat. We aimed to report patient mortality, reoperations, and complications following Vancouver C PFFs in a contemporary cohort all treated with a laterally-based locking plate. Methods We retrospectively identified 42 consecutive Vancouver C PFFs between 2004 and 2018. There was a high prevalence of comorbidities, including 9 patients with neurologic conditions, 9 with a history of cancer, 8 diabetics, and 8 using chronic anticoagulation. Mean time from THA to PFF was 6 years (range, 1 month – 25 years). All fractures were treated with a laterally-based locking plate. Fixation bypassed the femoral component in 98% of cases and extended as proximal as the lesser trochanter in 18%. Kaplan-Meier survival was used for patient mortality, and a competing risk model was used to analyze survivorship free of reoperation and non-union. Mean follow-up was 2 years. Results Patient mortality was 5% at 90 days and 31% at 2 years. Cumulative incidence of reoperation was 13% at 2 years. There were 5 reoperations including revision osteosynthesis for non-union and/or hardware failure (2), debridement and hardware removal for infection (2), and removal of hardware and total knee arthroplasty for posttraumatic arthritis (1). Cumulative incidence of non-union was 10% at 2 years. Conclusion Patients who sustained a Vancouver C PFFs had a high mortality rate (31%) at 2 years. Moreover, 13% of patients required a reoperation within 2 years, most commonly for infection or non-union.
Article
Background: Outcomes following proximal interphalangeal joint (PIPJ) arthrodesis by a variety of surgical methods are available. Reports detailing clinical outcomes following PIPJ arthrodesis utilising the proximal interphalangeal joint locking compression plate (PIP-LCP) and abaxial transarticular lag screws technique are limited. Objectives: To report survival, radiographic, and clinical outcomes following PIPJ arthrodesis with PIP-LCP and abaxial transarticular lag screw fixation. Study design: Retrospective case series. Methods: Medical records of all horses undergoing pastern arthrodesis from 2009-2018 were reviewed. Arthrodeses performed using a 3-hole, 4.5 mm narrow LCP, specifically designed for the proximal interphalangeal joint, were included. Patient details, presentation, radiographic findings, intraoperative and postoperative data, and complications were documented. Short and long term follow-up was available for 23 horses. Results: Thirty PIPJ arthrodeses were performed in 29 horses meeting the criteria for inclusion. Twenty-eight horses (97%, 95%CI 83-100) survived to discharge. Twenty-three horses (79%, 95%CI 60-92%) had successful outcomes including 12 of the 15 forelimb cases and 11 of the 13 hindlimb cases with available follow-up. Fifteen of 19 performance horses returned to athletic activity. Soundness in performance horses was recognised at less than 3 months in 1 case, 3 to 6 months in 6 cases, 6 to 12 months in 5 cases, and greater than 12 months in 6 cases. Complications included 3 implant infections, support limb laminitis (2 horses), and fragmentation of the extensor process of the distal phalanx (1 horse). Main limitations: A retrospectively reviewed, small study population with a variety of breeds and disciplines. Conclusions: The PIP-LCP construct provides a very good prognosis for performance and an excellent prognosis for pasture soundness.
Article
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This study aimed to evaluate the effectiveness of bridge plating of simple tibial fractures in dogs by minimally invasive plate osteosynthesis (MIPO). Medical and radiographic records of twenty-nine dogs with simple tibial fractures that underwent bridge fixation by MIPO were retrospectively evaluated. The clinical outcome was classified considering the presence of lameness at the end of the treatment. The tibial mechanical joint angles were measured and compared with the values described in the literature. Additionally, fragment apposition and implant disposition were evaluated. Based on the modified Radiographic Union Scale for Tibial fractures, the moment of clinical union was determined. Clinically, at the end of treatment, only one patient presented lameness at a trot. While there was no significant difference between the bone alignment in the frontal plane values and the values described in the literature (P>0.05), the caudal proximal tibial angle was significantly higher (P=0.001). The median fragment apposition was considered acceptable. The average bridge plate ratio, plate working length, and plate screw density were 0.8, 0.57, and 0.48, respectively. The median time to clinical union was 30 days. Bridge plating in simple tibial fractures resulted in fast healing and low complication rates.
Article
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.
Article
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The application of volar locking plate (VLP) is promising in the treatment of dorsally comminuted and displaced fracture. However, the optimal balance between the mechanical stability of VLP and the mechanobiology at the fracture site is still unclear. The purpose of this study is to develop numerical models in conjunction with experimental studies to identify the favourable mechanical microenvironment for indirect healing, by optimizing VLP configuration and post-operative loadings for different fracture geometries. The simulation results show that the mechanical behaviour of VLP is mainly governed by the axial compression. In addition, the model shows that, under relatively large gap size (i.e., 3–5 mm), the increase of FWL could enhance chondrocyte differentiation while a large BPD could compromise the mechanical stability of VLP. Importantly, bending moment produced by wrist flexion/extension and torsion moment produced from forearm rotation could potentially hinder endochondral ossification at early stage of healing. The developed model could potentially assist orthopaedic surgeons in surgical pre-planning and designing post-operation physical therapy for treatment of distal radius fractures.
Article
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.
Article
Background : Locking screws with a typical buttress thread have high levels of failure in patients with osteoporotic bones. This study aims to develop a novel thread design for the locking screw and compare its fixation stability with the typical buttress thread. Methods : Locking screws with a novel thread design that possess an undercut feature and locking screws with a typical buttress thread were manufactured from stainless steel. Their fixation stabilities were then evaluated individually under a lateral migration test and evaluated in pairs together with a locking plate (LP) in an osteoporotic bone substitute under cyclic craniocaudal and torsional loadings. A finite element analysis (FEA) model was constructed to analyze the stress distributions present in the bone tissue adjacent to the novel thread versus the buttress thread. Results : The biomechanical test revealed that the novel thread had a significantly higher lateral migration strength than the buttress thread. When applied to a LP, the locking screw with the novel thread requires more cycles and higher forces or torque to resist migration up to 5 mm or 10 degrees than the buttress thread. The FEA simulation showed that the novel thread can make the stress distribute more evenly at the adjacent bone tissue when compared with the buttress thread. Conclusions : The locking screw with the novel undercut thread had superior lateral migration resistance during both initial and continued migration and superior fixation stability when applied to a LP under both cyclic craniocaudal loading and torsional loading than the locking screw with a typical buttress thread.
Article
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The femur fractures of the elderly, in particular in the two varieties subtrochanteric and of the distal femur, remain nowadays one of the most important challenges in surgical fracture treatment as they are often complicated, with an oblique or a spiral shape, intra-articular and with a comminuted nature. Plate osteosynthesis and retrograde nailing are almost the unique options for the treatment of these fractures. The use of cerclages for the osteosynthesis or a dynamic plate system could be interesting treatment options that are often not considered.
Chapter
Devices for orthopedic trauma treatment need to satisfy three key clinical requirements and consequent mechanical demands arising from them: they must support fracture healing; they must not fail during the healing period; and they should not loosen or cause patient discomfort. This chapter discusses the biomechanics and design issues associated with fulfilling the above demands by commonly used devices: external fixators, plates and screws, and intramedullary nails. In most cases, healing occurs via callus formation, which is supported by an appropriate amount of interfragmentary motion between fractured bone fragments. Delayed healing can cause failure of the device due to fatigue. Healing depends on the mechanical behavior of the bone–device construct, which has been extensively investigated. The problem of device loosening, particularly in poor-quality bone, has received relatively less attention, and this chapter considers its evaluation in some detail. This chapter also shows that the demands on the device change as healing progresses and device choice and configuration needs to consider healing in preoperative planning. It also discusses the issues associated with replicating the in vivo boundary conditions in laboratory experiments and numerical simulation. Recent studies on modeling of loosening due to cyclic loading are also discussed.
Article
Introduction: In the surgical fixation of fractures, proper biomechanical stability is key in preventing clinical complications including poor fracture healing, residual deformity, loss of fixation, or implant failure. Stability is largely influenced by treatment decisions made by the surgeon. The interplay of surgeon-controlled variables and their effect on the three-dimensional (3D) biomechanics of a fracture fixation construct are often not intuitive, and current training methods do not facilitate a deep understanding of these interactions. Methods: A simulation software interface, FracSim, was developed. FracSim is built on a large precomputed library of finite element simulations. The software allows a surgeon to make adjustments to a virtual fracture fixation construct/weight-bearing plan and immediately visualize how these changes affect 3D biomechanics, including implant stress and fracture gap strain, important for clinical success. Twenty-one orthopaedic residents completed an instructor-led educational session with FracSim focused on bridge plating. Subjects completed pretests and posttests of knowledge of biomechanical concepts and a questionnaire. Results: Subjects scored a mean of 5.6/10 on the pretest of biomechanical knowledge. Senior residents scored better than junior residents (P = 0.04). After the educational session with FracSim, residents improved their test scores to a mean of 8.0/10, with a significant improvement (P < 0.001). Questionnaire scores indicated that subjects believed that FracSim had realistic implants, constructs, and motions and that training with FracSim was purposeful, desirable, efficient, fun, and useful for enhancing the understanding of fracture fixation biomechanics. Discussion: This new type of simulation software enables interactive visualization of 3D fracture fixation biomechanics. Limitations of this study include lack of a control group undergoing traditional education and lack of a delayed posttest to assess retention. FracSim may provide an effective and engaging way to promote a deeper understanding of biomechanical concepts in the orthopaedic learner.
Article
The locking compression plate (LCP) and screw sets are widely used as internal fixator assemblies to treat long bone fractures. However, the surgeon's critical challenge is choosing the implant set (plate and screws) for each patient. The present study introduces a parametrized simulation-based optimization algorithm for determining an LC system with the best bone-implant stability. For this purpose, a three-dimensional fractured bone supported by an LC system was generated, and the discrete genetic optimization approach was utilized to design the optimum implant. Initially, an algorithm was developed to optimize the optimum layouts for different numbers of screws. For the middle third transverse fracture, six screws were selected as the optimal number of the screws. In a second stage, the model was run to determine the best LC plate dimensions for desired fractured bones. Finally, optimal plates were identified for simple middle third transverse, 60° middle third oblique, and distal third transverse femoral fractures. The results of these simulations and those for other fracture types can be exploited to achieve improved surgical outcomes by selecting proper implants and screws configurations.
Article
Practical relevance The femur is the most commonly fractured bone in cats. Femoral fractures usually result from high-velocity trauma such as a road traffic accident or fall from a height and, as such, are associated with a wide variety of concurrent injuries. The initial focus of treatment should always be on assessment and stabilisation of the major body systems. Once any concurrent injuries have been addressed, all femoral fractures need surgical stabilisation, with the notable exception of greenstick fractures in very young cats, which can heal with cage rest alone. A number of different surgical options are available depending on the fracture type, location, equipment, surgeon experience and owner finances. Clinical challenges Femoral fractures can vary hugely in complexity and the small size of feline bones can limit the choice of implants. Furthermore, cats can present unique challenges in the postoperative period due to their active nature and the limited means to control their exercise level. Audience This review is aimed at general and feline-specific practitioners who have some experience of feline orthopaedics, as well as those simply wishing to expand their knowledge. Aims The aim of this review is to help clinicians assess, plan and manage feline femoral fractures. It provides an overview of diagnostic imaging and a discussion of a range of suitable surgical options, including the principles of different types of fixation. It also highlights cat-specific issues, approaches and implants pertinent to the management of these cases. Evidence base A number of original articles and textbook chapters covering many aspects of femoral fractures in cats and dogs have been published. Where possible, this review draws on information from key feline research and, where necessary, extrapolates from relevant canine literature. The authors also offer practical guidance based on their own clinical experience.
Article
This paper aims to identify an optimum bone fracture stabilizer. For this purpose, three design variables including the ratio of the screw diameter to the plate width at three levels, the ratio of the plate thickness to the plate width at three levels, and the diameter of the bone at two levels were selected for analysis. Eighteen 3D verified finite element models were developed to examine the effects of these parameters on the weight, maximum displacement and maximum von Mises stress of the fixation structure. Considering the relations between the inputs and outputs using multivariate regression, a genetic algorithm was used to find the optimal choices. Results showed that the diameter of the bone and the amount of load applied on it did not have a significant effect on the normalized stresses on the structures. Furthermore, in all ratio of the plate thickness to the plate width, as the ratio of the screw diameter to the plate width increased, the amount of stress on the structure decreased. But, by further increasing the ratio of the screw diameter to the plate width, the amount of stress on the structure increased. On the other hand, by increasing the value of the ratio of the plate thickness to the plate width, the maximum amount of stress on the structure decreased. Finally, optimal solutions in terms of the weight and the maximum amount of stress on the structure were presented.
Article
Background Implant removal rates after clavicle plating are high. Recently, low-profile dual mini-fragment plate constructs have proven lower implant removal rates for the fixation of diaphyseal clavicle fractures. However, these constructs have not been subject to a biomechanical investigation. Aims To investigate:(1) the biomechanical competence of different dual plate designs in terms of stiffness and cycles to failure, and (2) to compare them against 3.5 mm single superoanterior plating. Methods Twelve artificial clavicles were assigned to 2 groups and instrumented with titanium matrix mandible plates as follows: group1 (2.5 mm anterior+2.0 mm superior) and group2 (2.0 mm anterior+2.0 mm superior) after an unstable clavicle shaft fracture(AO/OTA15.2C) was simulated. Specimens were cyclically tested to failure under craniocaudal cantilever bending, superimposed with torsion around the shaft axis and compared to previous published data of 6 locked superoanterior plates tested under the same conditions (group3). Findings Displacement after 5000 cycles was highest in group3 (10.7 ± 0.8 mm) followed by group2 (8.5 ± 1.0 mm) and group1 (7.5 ± 1.0 mm), respectively. Both were significantly higher in group3 as compared to both groups1 and 2 (p ≤ 0.027). Cycles to failure were highest in group3 (19,536 ± 3586) followed by group1 (15,834 ± 3492) and group2 (11,104 ± 3177), being significantly higher in group3 as compared to group2 (p = 0.004). Interpretation Low-profile 2.0/2.0 dual plates demonstrated similar initial stiffness compared to 3.5 mm single plates, however, they revealed significantly lower cycles to failure. Moreover, low-profile 2.5/2.0 dual plates showed significant higher initial stiffness and similar resistance to failure compared to 3.5 mm single locked plates and can therefore be considered as a useful alternative for diaphyseal clavicle fracture fixation.
Article
Objectives The aim of this study was to measure and compare the stiffness and cyclic fatigue of two plate-bone model constructs, with either two or three locking screws per fragment, under cyclic compression. Methods A 10-hole 3.5 mm stainless steel locking compression plate (LCP) was fixed 1 mm from a synthetic bone model in which the fracture gap was 47 mm. Two groups of 10 constructs, prepared with either two or three bicortical locking screws placed at the extremities of each fragment, were tested in a load-controlled compression test until failure. Results The three-screw constructs were stiffer than the two-screw constructs (196.75 ± 50.48 N/mm and 102.43 ± 22.93 N/mm, respectively) and the actuator displacements of the two-screw constructs were higher (18.02 ± 1.07 mm) than those of the three-screw constructs (14.48 ± 2.25 mm). The number of cycles to failure of the two-screw constructs was significantly lower (38,337.50 ± 2,196.98) than the that of the three-screw constructs (44,224.00 ± 1,515.24). Load at irreversible deformation was significantly lower in the two-screw constructs (140.93 ± 13.39 N) than in the three-screw constructs (184.27 ± 13.17 N). All constructs failed by plate bending at the gap between the two cylinders. Clinical Significance Omission of the third innermost locking screw during bridging osteosynthesis subjected to compression forces led to a 13.3% reduction in the number of cycles to failure and a 23.5% reduction of the load withstood by the plate before plastic deformation occurred.
Article
Introduction Nonunion rates for distal femur fractures treated with lateral locked plating (LLP) remains as high as 18-22% despite significant advances with implant design and construct modulation. However, whether treatment of distal femur fractures with rIMN has improved outcomes compared to LLP has not been well characterized. The purpose of this study was to compare outcomes of complete articular distal femur fractures (AO/OTA 33-C) treated with either LLP or rIMN. Methods 106 distal femur fractures in 106 patients between January 2014 and January 2018 were identified. Medical records were reviewed to collect patient age, gender, body mass index, sagittal and coronal plane alignment on immediate postoperative radiographs, time to union, incidence of nonunion, and incidence of secondary operative procedures for repair of a nonunion. Results Of 106 patients, 50 underwent rIMN and 56 underwent LLP. The mean age at the time of injury was 51 years (21 to 86 years) and there were 55 males. Average coronal alignment of 83.7o of anatomic lateral distal femoral angle (aLDFA) and sagittal alignment of <1o of apex anterior angulation in the rIMN group. In the LLP group there was an average of 87.9o of aLDFA and 1.9o of apex anterior angulation (p=.005 and p=.36). Average time to union in the rIMN group was 6 months and 6.6 months in the LLP group (p=.52). Incidence of nonunion in the rIMN group was 11.8% and 27.5% in the LLP group (p=.008). There were 8 secondary procedures for nonunion in the rIMN group and 18 in the LLP group (p=.43). Conclusions Our results demonstrated a higher nonunion rate and coronal plane malalignment with LLP compared to rIMN. While prospective data is required, rIMN does appear to be an appropriate treatment for complete articular distal femur fractures with a potentially decreased rate of nonunion.
Article
The diagnosis of fracture nonunion following plate osteosynthesis is subjective and frequently ambiguous. Initially following osteosynthesis, loads applied to the bone are primarily transmitted through the plate. However, as callus stiffness increases, the callus is able to bear load proportional to its stiffness while forces through the plate decrease. The purpose of this study was to use a “smart” fracture plate to distinguish between phases of fracture healing by measuring forces transmitted through the plate. A wireless force sensor and small adapter were placed on the outside of a distal femoral locking plate. The adapter converts the slight bending of the plate under axial load into a transverse force which is measurable by the sensor. An osteotomy was created and then plated in the distal femur of biomechanical Sawbones. Specimens were loaded to simulate single-leg stance first with the osteotomy defect empty (acute healing), then sequentially filled with silicone (early callus) and then polymethyl methacrylate (hard callus). There was a strong correlation between applied axial load and force measured by the “smart” plate. Data demonstrate statistically significant differences between each phase of healing with as little as 150 N of axial load applied to the femur. Forces measured in the plate were significantly different between acute (100%), early callus (66.4%), and hard callus (29.5%). This study demonstrates the potential of a “smart” fracture plate to distinguish between phases of healing. These objective data may enable early diagnosis of nonunion and enhance outcomes for patients.
Article
Background and objective : Therapeutic exercises could potentially enhance the healing of distal radius fractures (DRFs) treated with volar locking plate (VLP). However, the healing outcomes are highly dependent on the patient-specific fracture geometries (e.g., gap size) and the loading conditions at the fracture site (e.g., loading frequency) resulted from different types of therapeutic exercises. The purpose of this study is to investigate the effects of different loading frequencies induced by therapeutic exercises on the biomechanical microenvironment of the fracture site and the transport of cells and growth factors within the fracture callus, ultimately the healing outcomes. This is achieved through numerical modelling and mechanical testing. Methods : Five radius sawbones specimens (Pacific Research Laboratories, Vashon, USA) fixed with VLP (VRP2.0+, Austofix) were mechanically tested using dynamic test instrument (INSTRON E3000, Norwood, MA). The loading protocol used in mechanical testing involved a series of cyclic axial compression tests representing hand and finger therapeutic exercises. The relationship between the dynamic loading rate (i.e., loading frequency) and dynamic stiffness of the construct was established and used as inputs to a developed numerical model for studying the dynamic loading induced cells and growth factors in fracture site and biomechanical stimuli required for healing. Results : There is a strong positive linear relationship between the loading rate and axial stiffness of the construct fixed with VLP. The loading rates induced by the moderate frequencies (i.e., 1-2 Hz) could promote endochondral ossification, whereas relatively high loading frequencies (i.e., over 3 Hz) may hinder the healing outcomes or lead to non-union. In addition, a dynamic loading frequency of 2 Hz in combination of a fracture gap size of 3 mm could produce a better healing outcome by enhancing the transport of cells and growth factors at the fracture site in comparison to free diffusion (i.e. without loading), and thereby produces a biomechanical microenvironment which is favourable for healing. Conclusion : The experimentally validated numerical model presented in this study could potentially contribute to the design of effective patient-specific therapeutic exercises for better healing outcomes. Importantly, the model results demonstrate that therapeutic grip exercises induced dynamic loading could produce a better biomechanical microenvironment for healing without compromising the mechanical stability of the overall volar locking plate fixation construct.
Article
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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.
Article
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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.
Article
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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.
Article
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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.
Article
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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.
Article
Full-text available
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.
Article
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.
Article
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.
Article
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).
Article
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.
Article
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.
Article
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.
Article
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.
Article
From January 1982 through December 1988, 150 patients with 153 Winquist Class III and IV comminuted diaphyseal femur fractures due to high energy blunt trauma were treated with immediate plate fixation. A total of 260 major general surgical systems were injured in 150 patients. Forty-nine patients did not have adequate preoperative spine radiographs due to positioning or time factors. Nineteen patients 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 I, 25 grade II, 10 grade IIIA, 4 IIIB, 2 IIIC. 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 degrees 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 degrees of knee motion and 140 fractures have greater than 130 degrees 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.
Article
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.
Article
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.
Article
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.
Article
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.
Article
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.
Article
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.
Article
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.
Article
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.
Article
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.
Article
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.
Article
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.
Article
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.
Article
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.
Article
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.
Article
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.
Article
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.
Article
The appearance of porous bone under fixation plates during fracture healing, attributed to disturbance of blood supply by the plate, has led to new plate designs with reduced plate to bone contact. The fixation stability afforded by these devices, in comparison to implants commonly used for fixation, is not well known. Therefore, the construct stiffnesses of osteotomized synthetic tibiae fixed with dynamic compression plates, external fixators, or two configurations of noncontact plates were compared in axial compression, bending, and torsion with and without cortical contact at the osteotomy site. The results of this study show that (1) the noncontact plated constructs achieve comparable fixation rigidity to constructs using dynamic compression plates or external fixators, if applied at a distance no greater than 5 mm from the surface of the tibia, and (2) the fixation rigidity of the noncontact plate decreases as the distance between plate and bone surface increases.
Article
Our purpose was to study the relationship between the number of plate holes filled and the spacing between the screws and the resultant strength of plated constructs. Broad regular DC plates were anchored with 4.5-mm cortical screws to blocks of polyurethane foam. Six constructs were tested: (a) screws in holes 1, 2, and 3; (b) screws in holes 1 and 3; (c) screws in holes 1 and 4; (d) screws in holes 1 and 5; (e) screws in holes 1 and 6; (f) screws in holes 1, 3, and 5. The strength was quantified using a material-testing system. In cantilever and four-point bending, the constructs were loaded in both gap-closing and gap-opening modes. Screws in holes 1, 2, and 3 were tested against other constructs. For cantilever bending (gap opening and gap closing), construct (a) was stronger than construct (b), as strong as construct (c), but weaker than the constructs with more widely spaced screws (p < 0.0001). In terms of four-point bending, for gap opening, the standard fixation (construct (a) was stronger than construct (b) but weaker than the more widely spaced constructs. For gap closing, construct (a) was stronger than constructs (b) and (c) but weaker than the rest. Regardless of the spacing of screws and the plate length, strength in torsion was dependent on the number of screws securing the plate. In a laboratory fracture model of plate-bone constructs tested to failure by screw pullout, wider spacing of bone screws increases the bending strength of screw-plate fixation and can be more effective than increasing the number of screws. Torsional strength is independent of screw placement in plates of a given width and depends on the number of screws used.
Article
Fracture of the long bones results in a repair process that has the potential to restore the anatomic morphology and mechanical integrity of the bone without scar tissue. The repair process can occur in two patterns. In the first, under conditions of rigid stabilization, direct osteonal remodeling of the fracture line can occur with little or no external callus, a process known as direct bone repair. The second pattern of repair involves bridging of the fragments with external callus and formation of bone in the fracture site by endochondral healing. This type of repair is known as indirect bone healing and occurs under less rigid interfragmentary stabilization. The rate of healing and the extent of callus in this type of repair can be modulated by the mechanical conditions at the fracture site. Applying cyclic interfragmentary micromotion for short periods has been shown to influence the repair process significantly, and characteristics of this stimulus influence the healing response observed. In the current study, a short term interfragmentary cyclic micromovement applied at a high strain rate induced a greater amount of periosteal callus than the same stimulus applied at a low strain rate. This high strain rate stimulus applied later in the healing period significantly inhibited the progress of healing. The beneficial effect of this particular biophysic stimulus early in the healing period may be related to the viscoelastic nature of the differentiating connective tissues in the early endochondral callus. In the early endochondral callus, high rates of movement induce a greater deformation of the fracture fragments because of the stiffening of the callus. Alternatively, the transduction pathway may involve streaming potentials as a result of the high movement rate.
Article
Based on existing knowledge of noncontact plates, an experimental prototype of a nonperiosteal contact internal fixation implant ("noncontact internal fixator") has been designed. The construct rigidity of osteotomised synthetic composite femora, fixed with the noncontact fixator and a reamed, statically-locked intramedullary nail were compared in axial compression, two plane bending and torsion in four types of diaphyseal fractures. With the exception of axial loading in the presence of extensive comminution, the fixation stability provided by the noncontact fixator is significantly higher than that of the tested intramedullary nail. Any degree of cortical contact between the two main fragments is important for the stability of this nonperiosteal contact fixation system under axial load. Appropriately-designed "internal fixators" could provide not only a number of biological and technical advantages, but also fixation stability comparable and in certain aspects superior to that of other fixation methods.