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Mechanical performance comparison of two surgical constructs for wrist four-corner arthrodesis via dorsal and radial approaches
Abstract
Background
Four-corner arthrodesis, which involves fusing four carpal bones while removing the scaphoid bone, is a standard surgery for the treatment of advanced stages of wrist arthritis. Nowadays, it can be performed using a dorsal approach by fixing a plate to the bones and a new radial approach is in development. To date, there is no consensus on the biomechanically optimal and most reliable surgical construct for four-corner arthrodesis.
Methods
To evaluate them biomechanically and thus assist the surgeon in choosing the best implant orientation, radial or dorsal, the two different four-corner arthrodesis surgical constructs were virtually simulated on a 3D finite element model representing all major structures of the wrist. Two different realistic load sets were applied to the model, representing common tasks for the elderly.
Findings
Results consistency was assessed by comparing with the literature the force magnitude computed on the carpal bones. The Von Mises stress distribution in the radial and dorsal plates were calculated. Stress concentration was located at the plate-screw interface for both surgical constructs, with a maximum stress value of 413 MPa for the dorsal plate compared to 326 MPa for the radial plate, meaning that the stress levels are more unfavourable in the dorsal approach.
Interpretation
Although some bending stress was found in one load case, the radial plate was mechanically more robust in the other load case. Despite some limitations, this study provides, for the first time, quantified evidence that the newly developed radial surgical construct is mechanically as efficient as the dorsal surgical construct.
... Значительное количество исследователей указывает на незаменимость участия реабилитологов в послеоперационном периоде. Подконтрольная разработка оперированного сустава позволяет исправить порочный стереотип движения, сформированный у пациентов за долгие годы болезни [16][17][18][19][20]. Привлечение ревматологов необходимо для подбора базовой терапии, принимая во внимание единый патологический механизм морфологических изменений сустава [6,17,21]. ...
Introduction Survival of implants is an important indicator of improvement in the patient's quality of life. In foreign literature, the issue of implant survival finds special attention.
The aim of the work was to evaluate the efficacy and survival of an unconstrained ceramic wrist joint endoprosthesis.
Materials and methods We analysed 83 cases of total wrist arthroplasty with an unconstrained ceramic implant at long-term follow-up. At the Novosibirsk RSITO, total wrist arthroplasty was performed in 81 patients with severe changes in the wrist joint from 2011 to 2021. Two patients underwent arthroplasty on two joints. A retrospective uncontrolled cohort study was conducted which divided the hospitalized patients into three groups according to the etiological cause of the disease. Radiological methods were used to control the state of the implant (radiography in two projections and CT-scans of the wrist joint). For binary indicators, the number, rates and 95 % confidence interval of frequencies were calculated according to the Wilson formula in the groups. Comparison was carried out by Fisher's exact two-sided test. The p-error was corrected using the Benjamini – Hochberg method. Kaplan – Meier curves were constructed for survival analysis. The groups were compared using a generalized chi-square test.
Results Each case of repeated surgical intervention was evaluated from the standpoint of selected groups. Depending on the time elapsed from surgery to revision, we calculated the time frame for overall and group survival of the components of the wrist joint endoprosthesis. The causes and scope of surgical revision are presented.
Discussion There are no data on the survival of unconstrained ceramic wrist joint implants in the foreign literature. Graphic images according to a proposal for the division of the orthopaedic postoperative period are presented. Conclusions 1. Intermediate conclusions in regard to total arthroplasty with an unconstrained ceramic endoprosthesis of the wrist joint inspire optimism in obtaining a stable positive effect of motion range lost due to the degenerative process in the wrist joint. 2. An 11-year follow-up period demonstrates that the survival rate of an unconstrained ceramic wrist endoprosthesis is 88 %.
... Recent medical literature shows a significant increase in the use of 3D imaging as a diagnostic tool in many clinical cases, including facial fractures (de Carvalho et al. 2021, Wickwire et al. 2022, naso-orbital-ethmoid fractures (Onisor 2022), cervical fractures (Ren et al. 2021) and orbital blowout fractures (Jansen et al. 2018). Researchers have also used this technology to conduct virtual surgery on the scaphoid bone (Faudot et al. 2021) while other studies have used it to scan the peri-orbital region for a very high clinical accuracy (Hollander et al. 2021). This project used human tissue samples and advanced imaging technology in the form of two-dimensional (2D) and three-dimensional (3D) imaging to investigate the variation and correlations between the CP and the olfactory foramina, alongside examining the dimensions of the Crista Galli in correlation with the CP. ...
Investigations on the structural variations in the cribriform plate (CP), olfactory foramina and the Crista Galli showcase the benefits of using 3D imaging on smaller structures. These techniques reveal accurate details about bone morphology and density. Comparing different techniques, this project aims to examine the correlation between the CP, olfactory foramina, and Crista Galli. Computed tomography was used to translate and apply the findings acquired from the samples in radiographic studies on CPs for potential clinical significance. The findings show that the surface area measurements were significantly larger when using 3D imaging techniques in comparison with the 2D counterpart. Using 2D imaging, the maximum surface area of the CPs was 239.54 mm2, however, paired 3D samples showed the maximum surface area was 355.51 mm2. The findings show that Crista Galli's dimensions varied greatly, with length ranging from 15 to 26 mm, height ranging from 5 to 18 mm, and width ranging from 2 to 7 mm. The 3D imaging allowed for surface area measurements on the Crista Galli, and the surface area ranged from 130 to 390 mm2. When 3D imaging was used, significant correlations were found between the surface area of the CP and the length of the Crista Galli (p = 0.001). The findings show that measurements on the Crista Galli using 2D and 3D reconstructed radiographic imaging reflect similar ranges of dimensions to 3D imaging measurements. The findings also suggest that the Crista Galli may increase in length with the CP to support the latter and olfactory bulb during trauma which may be used by clinicians alongside 2D CT scans for optimal diagnosis.
... This methodology can provide a prediction of stress distribution and has the ability to predict problematic contact surfaces and wear, guiding researchers and clinicians to choose an optimal orientation for implants, and to improve elements in the design phase. [6][7][8] The FEM is a numerical method used to solve differential equations that represent a mathematical model. 9 A general FEM process is divided into three steps: (1) preprocessing or model preparation, (2) solution, and (3) postprocessing. ...
Background Understanding wrist biomechanics is important to appreciate and treat the wrist joint. Numerical methods, specifically, finite element method (FEM), have been used to overcome experimental methods' limitations. Due to the complexity of the wrist and difficulty in modeling, there is heterogeneity and lack of consistent methodology in the published studies, challenging our ability to incorporate information gleaned from the various studies.
Questions/Purposes This study summarizes the use of FEM to study the wrist in the last decade.
Methods We included studies published from 2012 to 2022 from databases: EBSCO, Research4Life, ScienceDirect, and Scopus. Twenty-two studies were included.
Results FEM used to study wrist in general, pathology, and treatment include diverse topics and are difficult to compare directly. Most studies evaluate normal wrist mechanics, all modeling the bones, with fewer studies including cartilage and ligamentous structures in the model. The dynamic effect of the tendons on wrist mechanics is rarely accounted for.
Conclusion Due to the complexity of wrist mechanics, the current literature remains incomplete. Considering published strategies and modeling techniques may aid in the development of more comprehensive and improved wrist model fidelity.
Little is known about the mechanics of in vivo loading on total wrist prostheses where many studies have looked at the mechanics of other types of arthroplasty such as for the hip and the knee which has contributed to the overall success of these types of procedures. Currently surgeons would prefer to carry out arthrodesis on the wrist rather than consider arthroplasty as clinical data have shown that the outcome of total wrist arthroplasty is poorer than compared to the hip and knee. More research is needed on the loading mechanisms of the implants in order to enhance the design of future generation implants. This study looks at the load transfer characteristics of the Universal 2 implant using a finite element model of a virtually implanted prosthesis during gripping. The results showed that the loading on the implant is higher on the dorsal and ulnar aspect than on the volar and radial aspect of the implant. The whole load is transmitted through the radius and none through the ulna.
Although limited carpal fusion is a choice of treatment in several wrist disorders, little is known about the biomechanics of these procedures, especially the loads carried by the ligaments. In a finite element study, four types of limited carpal fusions (scaphotrapeziotrapezoid, capitohamate, four corner fusion with and without scaphoid excision) were simulated and the loads carried by the ligaments were recorded. Measurements were repeated with and without implantation. The load transmission through the ligaments varied by the type of the fusion but, radioscaphoid and long radiolunate ligaments carried significantly more loads if not excised during the operation. Implantation did not affect the results in most cases. The model of the present study may be useful in preoperative planning.
The total replacement of wrists affected by rheumatoid arthritis (RA) has had mixed outcomes in terms of failure rates. This study was therefore conducted to analyse the biomechanics of wrist arthroplasty using recently reported implants that have shown encouraging results with the aim of providing some insights for the future development of wrist implants. A model of a healthy wrist was developed using computed tomography images from a healthy volunteer. An RA model was simulated based on all ten general characteristics of the disease. The ReMotion ™ total wrist system was then modelled to simulate total wrist arthroplasty (TWA). Finite element analysis was performed with loads simulating the static hand grip action. The results show that the RA model produced distorted patterns of stress distribution with tenfold higher contact pressure than the healthy model. For the TWA model, contact pressure was found to be approximately fivefold lower than the RA model. Compared to the healthy model, significant improvements were observed for the TWA model with minor variations in the stress distribution. In conclusion, the modelled TWA reduced contact pressure between bones but did not restore the stress distribution to the normal healthy condition.
Scaphoid excision and 4-corner arthrodesis is a salvage option for patients with advanced carpal collapse. This study aims to compare the clinical outcomes of 4-corner arthrodesis (FCA) at one year, 2 years, and a minimum of 10 years.
A cohort study was performed of patients having scaphoid excision and FCA procedure by a single surgeon. Thirty-one of 35 recruited were followed up for 10 years. The mean patient age was 47 years. All patients had scaphoid excision and FCA, using bone graft and 3M Shapiro staples (3M, St Paul, MN). Patients were followed up prospectively at one year, 2 years, and a minimum of 10 years after surgery by an independent observer. Three patients were lost to follow-up between the 2-year and 10-year assessments because they were untraceable, and one patient died at 7 years, without any further intervention. Before surgery, pain scores measured with a visual analog scale, range of wrist movement, grip and pinch strength, and scores from a self-assessment functional questionnaire were recorded prospectively. These measures were repeated at each time point, in addition to patient satisfaction scores measured on a visual analog scale.
The pain scores decreased from a median preoperative score of 6/10 to 0/10 at one year. Grip strength did not change significantly. Wrist flexion decreased significantly after surgery, by an average of 22%. The average patient-reported satisfaction score was 8/10. There was no significant change in pain, wrist function, satisfaction, or arc of motion between one and 10 years. Two of 35 patients recruited had gone on to a total wrist arthrodesis for ongoing pain.
The outcome of scaphoid excision and 4-corner arthrodesis is favorable at one year and does not deteriorate significantly between one and 10 years. There is a low rate of conversion to total wrist arthrodesis. Pain scores are reduced at the cost of reduced wrist flexion.
The aim of this work was to create an anatomically accurate three-dimensional finite element model of the wrist, applying subject-specific loading and quantifying the internal load transfer through the joint during maximal grip. For three subjects, representing the anatomical variation at the wrist, loading on each digit was measured during a maximal grip strength test with simultaneous motion capture. The internal metacarpophalangeal joint load was calculated using a biomechanical model. High-resolution magnetic resonance scans were acquired to quantify bone geometry. Finite element analysis was performed, with ligaments and tendons added, to calculate the internal load distribution. It was found that for the maximal grip the thumb carried the highest load, an average of 72.2 +/- 20.1 N in the neutral position. Results from the finite element model suggested that the highest regions of stress were located at the radial aspect of the carpus. Most of the load was transmitted through the radius, 87.5 per cent, as opposed to 12.5 per cent through the ulna with the wrist in a neutral position. A fully three-dimensional finite element analysis of the wrist using subject-specific anatomy and loading conditions was performed. The study emphasizes the importance of modelling a large ensemble of subjects in order to capture the spectrum of the load transfer through the wrist due to anatomical variation.
Partial wrist arthrodesis is a commonly performed procedure for the treatment of posttraumatic wrist arthritis because of its ability to provide pain relief without sacrificing complete wrist motion. The purpose of this study was to evaluate the redistribution of force after four-corner fusion and scaphoid excision, and to correlate the findings with the reported clinical outcomes.
Fifteen cadaveric wrists were used to study the biomechanics of the four-corner fusion. Pressure-sensitive film (super-low-pressure-indicating film-Pressurex, Sensor Products Inc, Madison, NJ) was inserted into the radiocarpal joint. Using the MTS 858 Mini Bionix (MTS System, Eden Prairie, MN), 50-kg loads (220 N) were applied to the wrists before and after simulated four-corner fusion and scaphoid excision. Statistically, we compared the pressure in the normal (intact) wrists versus four-corner fusion and scaphoid excision. The pressure measurements across the scaphoid fossa, lunate fossa, and triangular fibrocartilage complex (TFCC) were compared.
There is a statistical significant difference between scaphoid, lunate, and TFCC mean total force when pre and post-fusion were compared (p = 0.0001). Our study revealed a statistical significant decrease in the mean scaphoid total force after scaphoid excision and four-corner fusion (p = 0.0001). We also found a subsequent increase in mean total force after scaphoid excision and four-corner fusion for the lunate fossa that did not reach statistical significance (p = 0.08), and no difference in load across the TFCC area (p = 0.995).
Our findings suggest that load is preferentially transferred to the radiolunate joint after scaphoid excision with four-corner fusion.
Displaced intra-articular distal radius fractures are difficult to treat, with numerous associated complications. The potential onset of post-traumatic osteoarthritis (OA) is a major concern. The relationship between malreduced intra-articular fracture of the distal radius and subsequent early onset of radiocarpal OA is clinically important, yet poorly understood. To better understand this presumed mechanical relationship, detailed information regarding joint loading, kinematics and associated stress distributions must be obtained. Toward this end, a three-dimensional finite element (3D FE) contact model of the radiocarpal joint has been developed, including the radius, lunate, scaphoid, articulations between these bones and selected soft tissues near the joint. FE model geometry was derived from cryomicrotome sections of a cadaver wrist. Radiocarpal contact stress distributions in the intact and simulated malreduced fracture conditions, previously collected using a cadaveric intra-articular fracture model, are used to establish validity of the computational model. Finally, a section of the distal radius constituting the entire lunate fossa was displaced 1,2 and 3 mm to represent a depressed lunate die-punch fracture.
Background:
The trapeziometacarpal joint is a common site for osteoarthritis development in the hand. When osteoarthritis is present, it results in significant functional disabilities due to the broad range of activities performed by this joint. However, our understanding of osteoarthritis initiation and progression at this joint is limited because of the current lack of knowledge regarding the properties and structure of the corresponding cartilage layers. The objective of this study is to assess the morphological and mechanical properties of trapeziometacarpal cartilage via the combination of indentation testing and contrast-enhanced computed tomography. Such research may lead to the development of medical imaging-based approaches to measure cartilage properties in vivo.
Methods:
Intact first metacarpals and trapezia were extracted from 16 fresh-frozen human cadaver hands. For each specimen, load-displacement behavior was measured at 9 testing sites using a standardized indentation testing device to calculate the normal force and Young's modulus of the cartilage sub-regions. The specimens were then immersed in CA4+ contrast agent solution for 48 h and subsequently scanned with a resolution of 41 μm in a HR-pQCT scanner to measure cartilage thickness and attenuation. Finally, correlations between compressive Young's modulus and contrast-enhanced computed tomography attenuation of the cartilage were assessed.
Findings:
No significant difference was found in cartilage thickness between the trapezium and first metacarpal, but the comparison between articular regions showed thinner cartilage around the volar aspect of both the first metacarpal and the trapezium. The first metacarpal cartilage was stiffer than the trapezial cartilage. A significant positive correlation was observed between Young's modulus and mean contrast-enhanced CT attenuations in superficial and full-depth cartilage in both the first metacarpal and the trapezium cartilage.
Interpretation:
The quantitative measurements of trapeziometacarpal thickness and stiffness as well as a correlation between Young's modulus and contrast-enhanced computed tomography attenuation provides a method for the non-destructive in vivo assessment of cartilage properties, a greater understanding of thumb cartilage behavior, and a dataset for the development of more accurate computer models.
Hand strength data are needed to understand and predict hand postures and finger loads while placing the hand on an object or surface. This study aims to analyze the effect of hand posture and surface orientation on hand force while pressing a flat surface. Twelve participants, 6 females and 6 males ages 19-25, performed three exertions (100%, 30% and 10% MVC- Maximum Voluntary Contraction) perpendicular to a plate in 4 angles (-45°, 0°, 45° and 90° with respect to the horizontal plane) at elbow height. Exertions involved pushing in two postures: (1) whole hand and (2) constrained to only using the fingertips. Inter-digit joint angles were recorded to map hand and finger motions and estimate joint moments for each condition. Participants exerted twice the force when pushing with whole hand vs. fingertips. 72-75% of the total force was exerted over the base of the palm, while only 11-13% with the thumb for exertions at 90°, 45° or 0° plate angles. Males maximum force for pushing at 0°, 45° and 90° plates averaged 49% higher than females for the whole hand and 62% for the fingertips (p < 0.01). There was no significant sex difference (p > 0.05) for the -45° plate. Thumb joint loads were generally higher than the other individual fingers (p < 0.05) in all % MVC and accounted for 12% of total force during whole hand exertions. On average, joint moments were 30% higher during fingertip conditions vs. whole hand. Thumb and finger joint moment magnitudes when pushing the plate at 100% MVC indicated that Metacarpophalangeal (MCP) joint moments were higher (p < 0.05) than Distal Interphalangeal joints (DIP) and Proximal Interphalangeal joints (PIP) under whole hand and fingertips conditions.
Carpal injuries treated over a 16 year period were studied to determine the incidence of various types of injury and to evaluate results of methods of treating these injuries. The literature was reviewed for purposes of comparison and to determine those methods which have been most successful in restoring satisfactory function to injured wrists.
Finite element analysis is commonly used to assist in the development and evaluation of orthopedic devices. The physics of these models are simplified through approximations that enable more efficient simulations, without compromising the accuracy of the relative comparisons between implant designs or configurations. This study developed and evaluated a technique to approximate the behavior of a finely threaded screw using a smooth cylinder with the threads implicitly represented through interfacial contact conditions. This pseudo-threaded model was calibrated by comparing to simulations that explicitly modeled the thread geometry with frictional contact. A parametric analysis was performed with a single screw-in-bone system, five loading directions, and three Young׳s moduli that span the range of cancellous bone (200, 600, and 1,000MPa). Considering that screw cut-out from cancellous bone is a critical clinical issue in the osteoporotic proximal humerus, the pseudo-threaded model was compared with a bonded interface to examine three different screw configurations in a 3-part proximal humerus fracture across 10 patients. In the single screw-in-bone system, the pseudo-threaded model predicted the screw displacement of the explicitly threaded model with 1-5% difference and estimated the strain distributions and magnitudes more accurately than a bonded interface. Yet, the relative comparisons of implant stability across the three different screw configurations in the proximal humerus were not affected by the modeling choice for the bone-screw interface. Therefore, the bonded interface could serve as a more efficient methodology for making relative comparisons between implants that utilize the same thread profile.
An enhanced musculoskeletal biomechanical model of the wrist joint is presented in this article. The developed computational model features the two forearm bones radius and ulna, the eight wrist bones, the five metacarpal bones, and a soft tissue apparatus. Validation of the model was based on information taken from the literature as well as own experimental passive in vitro motion analysis of eight cadaver specimens. The computational model is based on the multi-body simulation software AnyBody. A comprehensive ligamentous apparatus was implemented allowing the investigation of ligament function. The model can easily patient specific personalized on the basis of image information. The model enables simulation of individual wrist motion and predicts trends correctly in the case of changing kinematics. Therefore, patient-specific multi-body simulation models are potentially valuable tools for surgeons in pre- and intraoperative planning of implant placement and orientation.
Background and objective:
Carpal fusions are useful for treating specific carpal disorders, maximizing postoperative wrist motion, hand strength, reducing pain and instability of the joint. The surgeon selects the appropriate treatment by considering the degree of stability, the chronicity of the injury, functional demands of the patient and former patient's outcomes as well. However there are not many studies regarding the load distribution provided by the treatment. So, the purpose of this study is to analyze the load distribution through the wrist joint with an arthrodesis treatment and compare the results with a normal wrist.
Method:
To this end the rigid body spring model (RBSM) method was used on a three-dimensional model of the wrist joint. The cartilage and ligaments were simulated as springs acting under compression and tension, respectively, while the bones were considered as rigid bodies. To simulate the arthrodesis, the fused bones were considered as a single rigid body.
Results:
The changes on the load distribution for each arthrodesis agree with the treatment objective, reducing load transmission through a specific articular surface. For example, for SLAC/SNAC II most of the treatments reduced the load transmitted through the radioscaphoid fossae, almost by 8%. However, the capitolunate (CL) arthrodesis was the treatment that managed to keep the load transmitted through the radiolunate joint closer to normal conditions. Also, in treatments where the scaphoid was excised (3-corner, 4-corner and capitolunate arthrodesis), the joint surface between the lunate surface compensates by doubling the transmitted force to the radius.
Conclusions:
The common arthrodesis for treating SLAC/SNAC II-III, reduces, in fact, the load on the radioscaphoid joint. Alternative treatments that reduce load distribution on the radiocarpal joint should be three corner and capitolunate arthrodesis for treating SLAC/SNAC-II; and for SLAC/SNAC-III four corners with scaphoid excision. On Kienbock's disease. Scaphocapitate (SC) arthrodesis is more effective on reducing the load transmission through the radiolunate and ulnolunate joints. All arthrodesis treatment should consider changes on the load transmission, and also bones' fusion rates and pain reduction on patient's outcomes.
Introduction
Four-corner fusion was described in 1984 by HK Watson for the treatment of SLAC wrist. This intervention has undergone few changes since that description, but the debate on the fixation method is still not resolved.
Hypothesis
Dorsal locking plates provide better stability, short immobilization and a quicker return to daily activities than traditional fixation methods such as staples.
Materials and methods
Thirty-one fusions using the Medartis Aptus Four-Corner Fusion® plate at a mean 13.1 months’ follow-up and 35 using staples at a mean 80.4 months’ follow-up were reviewed in a clinical and radiographic retrospective comparative study.
Results
Results were comparable between the two groups in terms of range of motion (flexion-extension arc of 67.3° for plates and 60.6° for staples), force (29.6 and 28 kg.F), pain and disability (PRWE 34.8/150 and 40.9; QuickDASH 19.83/100 and 30). Mean time off work was significantly shorter in the plate group (4.5 vs. 7.9 months). There were no non-unions in the plate group, versus 2 in the staples group. Dorsal impingement implicating hardware was also less frequent in the plate group (2 vs. 11).
Discussion
The dorsal locking plate did not improve final results in four-corner fusion in terms of range of motion, force, pain or function compared to staples. However, it provided stable fixation, allowing a shorter immobilization and a quicker return to work. Although the initial cost is higher, it could allow significant savings on postoperative costs, shifting the technical debate into the field of public health.
Level of evidence
Level IV, retrospective study.
Although several types of intercarpal fusion have been advocated for the treatment of Kienbock's disease, the clinical outcome of each procedure is still inconclusive. The joint load and ligament tension based on a three-dimensional model were measured to determine which intercarpal fusion procedures unload the lunate and whether they alter the force transmission through the entire wrist joint. Ten theoretical models of wrists were used to simulate three different operative procedures: capitate-hamate fusion, scapho-trapezial-trapezoidal fusion, and scaphocapitate fusion. A discrete element analysis technique was used to perform these investigations. The joint force and ligament tension of normal wrists and of simulated operative procedures were calculated according to the deformation of each spring element, simulating the articular cartilage and the carpal ligaments. Scaphocapitate and scapho-trapezial-trapezoidal fusions significantly decreased the joint force at the radiolunate joint and the lunocapitate joint compared with the intact wrist. In contrast, these fusions significantly increased this value at the radioscaphoid joint in comparison with the intact wrist. In the midcarpal joint, scaphocapitate fusion also increased the joint force at the scapho-trapezial-trapezoidal joints and at the triquetral-hamate joint, whereas scapho-trapezial-trapezoidal fusion increased it at the scapho-capitate joint. Capitate-hamate fusion yielded no significant changes of the joint forces through the entire wrist joint. In the analysis of ligament tension, scaphocapitate and scapho-trapezial-trapezoidal fusions significantly decreased the tension only in the dorsal scapholunate ligament. These findings demonstrate that scaph-ocapitate and scapho-trapezial-trapezoidal fusions are effective in decompressing the lunate. By contrast, capitate-hamate fusion is ineffective in reducing lunate compression. Although scaphocapitate and scapho-trapezial-trapezoidal fusions are recommended for the treatment of Kienbock's disease, clinicians should consider that the increase of force transmission through the radioscaphoid and the midcarpal joints may lead to early degenerative changes after these procedures have been performed.
Although nearly every combination of intercarpal arthrodeses has been described, excision of the scaphoid and fusion of the remaining carpal bones in neutral alignment was a unique concept when it was introduced nearly 20 years ago. This time-tested and established procedure that is commonly known as the 4-corner or 4-bone arthrodesis is based on the principle that the radiolunate articulation is often spared from degenerative changes from conditions that result in rotatory subluxations of the scaphoid. The 4-corner arthrodesis is a motion-sparing, limited arthrodesis that reliably results in pain relief, improved grip strength, and overall high patient satisfaction with low associated nonunion and complication rates. Copyright © 2001 by the American Society for Surgery of the Hand
Scapholunate advanced collapse (SLAC) and scaphoid nonunion advanced collapse (SNAC) are the two most common patterns of posttraumatic wrist arthritis. This review discusses the etiology and clinical evaluation, as well as up-to-date treatment options, for both of these conditions. Classic as well as newer innovative techniques are discussed with clinical outcomes in order to provide an evidence-based review of the world's literature on SLAC/SNAC wrist.
A finite element model of the wrist was developed to simulate mechanical changes that occur after surgery of the wrist. After partial arthrodesis, the wrist will experience altered force transmission during loading. Three different types of partial arthrodesis were investigated - radiolunate, radioscaphoid, and radioscapholunate - and compared with the healthy untreated wrist. The results showed that the compressive forces on the radiocarpal joint decreased compared with the untreated wrist with both radiolunate and radioscaphoid fusions. The load transmission through the midcarpal joints varied depending on arthrodesis type. The forces in the extrinsic ligaments decreased with the fusion, most noticeably in the dorsal radiotriquetral ligament, but increased in the dorsal scaphotriquetral ligament. From the results of the study it can be concluded that the radioscapholunate fusion shows the most biomechanically similar behaviour out of the three fusion types compared with the healthy wrist. The modelling described in this paper may be a useful approach to pre-operative planning in wrist surgery.
The implicit finite element (FE) method can encounter numerical difficulties when solving non-linear quasi-static problems. The iterative approach employed may have trouble achieving convergence in analyses with a highly non-linear material behaviour, such as a crystal plasticity constitutive model. In the case of the explicit FE method the solver equations can be solved directly to determine the solution without iteration, thus providing an alternative, more robust method. In this study, a rate-dependent crystal plasticity algorithm was developed for use with the explicit FE package, ABAQUS/explicit. The subroutine and an equivalent implicit version were used in a series of comparative boundary value problem analyses. The suitability of the implicit and explicit solvers to various loading conditions was assessed and multiple processor speedup rates were also investigated. The results of the study showed that, for simpler loading conditions, the implicit method had a shorter solution time. In the case of loading conditions involving contact, the explicit method proved to be the preferable choice. The explicit method displayed constantly high levels of parallelisation efficiency compared to the implicit method for analyses solved using multiple processors. In conclusion, although the implicit FE method is traditionally favoured when solving quasi-static problems, it is important to recognise the advantages that the explicit method has in solving certain loading conditions.
Understanding the pathomechanics involved in rheumatoid arthritis (RA) of the wrist provides valuable information, which will invariably allow various therapeutic possibilities to be explored. The computational modelling of this disease permits the appropriate simulation to be conducted seamlessly. A study that underpins the fundamental concept that produces the biomechanical changes in a rheumatoid wrist was thus conducted through the use of finite element method. The RA model was constructed from computed tomography datasets, taking into account three major characteristics: synovial proliferation, cartilage destruction and ligamentous laxity. As control, a healthy wrist joint model was developed in parallel and compared. Cartilage was modelled based on the shape of the articulation while the ligaments were modelled with linear spring elements. A load-controlled analysis was performed simulating physiological hand grip loading conditions. The results demonstrated that the diseased model produced abnormal wrist extension and stress distribution as compared to the healthy wrist model. Due to the weakening of the ligaments, destruction of the cartilage and lower bone density, the altered biomechanical stresses were particularly evident at the radioscaphoid and capitolunate articulations which correlate to clinical findings. These results demonstrate the robust finding of the developed RA wrist model, which accurately predicted the pathological process.
In this study, a computational model of the wrist joint complex was developed and validated for investigating the biomechanical function of the joint in clinically representative scenarios. Joint behavior and kinematics were dictated only by osteoarticular contact, ligamentous constraints, and muscle loading. Three-dimensional articular surfaces of each bone were generated from CT images, while ligaments and muscles were modeled as linear springs and constant-magnitude force vectors, respectively. Commercially available rigid body dynamics software was to both build the model and simulate joint function. Range of motion model predictions were compared to a cadaveric study analyzing the effects of scaphoid distal pole excision and triquetral excision after radioscapholunate (RSL) fusion for validation. The computational model was able to accurately predict flexion, extension, radial deviation, and ulnar deviation motions in four states: normal (intact), RSL fusion, RSL fusion with the scaphoid distal pole excised, and RSL fusion with both the scaphoid distal pole and triquetrum excised. The model was also able to calculate other parameters of interest that are not easily obtainable experimentally, such as midcarpal forces. This model and modeling approach are anticipated to have value as a predictive clinical tool including effect of injuries or anatomical variations and initial outcome of surgical procedures for patient specific planning and custom implant design.
Computational models are increasingly being used for the analysis of kinematics and contact stresses in the wrist. To this point, however, the morphology of the carpal cartilage has been modeled simply, either with non-dimensional spring elements (in rigid body spring models) or via simple bone surface extrusions (e.g. for finite element models). In this work we describe an efficient method of generating high-resolution cartilage surfaces via micro-computed tomography (μCT) and registration to CT-generated bone surface models. The error associated with μCT imaging (at 10 μm) was 0.009 mm (95% confidence interval 0.007-0.012 mm ), or ~1.6% of the cartilage thickness. Registration error averaged 0.33±0.16 mm (97.5% confidence limit of ~0.55 mm in any one direction) and 2.42±1.56° (97.5% confidence limit of ~5.5° in any direction). The technique is immediately applicable to subject-specific models driven using kinematic data obtained through in vitro testing. However, the ultimate goal would be to generate a family of cartilage surfaces that could be scaled and/or morphed for application to models from live subjects and in vivo kinematic data.
Scapholunate advanced collapse (SLAC) and scaphoid nonunion advanced collapse are common patterns of wrist arthritis. Scaphoid nonunion advanced collapse is caused by trauma, whereas SLAC wrist may also result from chronic pseudogout and can appear bilaterally without a clear history of injury. Surgical treatment for SLAC wrist includes 4-corner arthrodesis, capitolunate arthrodesis, complete wrist arthrodesis, proximal row carpectomy (PRC), denervation, and radial styloidectomy. Scaphoid nonunion advanced collapse wrist has the additional surgical option of excision of the distal ununited scaphoid fragment. Controversy persists over the relative merits of PRC versus 4-corner arthrodesis and whether PRC may be performed in the setting of capitate arthritis.
A four-corner arthrodesis of the wrist is a salvage procedure for the treatment of specific wrist disorders, to achieve a movable, stable and pain free joint. However, a partial arthrodesis limits the postoperative range of motion (ROM). The goal of this study is to understand the mechanism of the reduction of the ROM and to evaluate the effect of the orientation of the lunate in the four-corner arthrodesis on the range of motion by using a biomechanical model, containing articular contacts and ligaments. Multi-body models of a normal wrist and a four-corner arthrodesis wrist with different orientation of the lunate were used for simulations of flexion-extension motion (FEM) and radial-ulnar deviation motion (RUD). The ROM of the postoperative wrist was reduced from 145° to 82° of the total arc of FEM and from 73° to 41.5° of the total arc of RUD. The model simulations show that the range of motion reduction is caused by overtension of the extrinsic wrist ligaments. Different positioning of the lunate changes the balance between the contact forces and ligament forces in the wrist. This explains the effect on the postoperative range of motion. The 20° flexed lunate did not give any gain in the extension motion of the wrist, caused joint luxation in flexion and limitation in RUD. The 30° extended lunate caused overtension of the extrinsic ligaments attached to the lunate. The ROM in this case is dramatically reduced. The model simulations suggest that the neutral position of the lunate seems to be most favorable for mobility of the wrist after a four-corner arthrodesis procedure.
Anatomic and biomechanical research of the wrist has yielded a substantial amount of information that improves our basic knowledge of carpal morphology and function of the wrist and provides information to better assess and improve treatment(s) for various problems of the wrist joint. A precise knowledge of the anatomy and biomechanics of the wrist is useful not only for diagnosis of traumatic ligamentous injuries or degenerative change of the wrist joint but also for treatment for wrist dysfunction.
Mechanisms of lubrication of human synovial joints have been analysed in terms of the operating conditions of the joint, the synovial fluid and articular cartilage. In the hip and knee during a walking cycle the load may rise up to four times body weight. In the knee on dropping one metre the load may go up to 25 time body weight. The elastic modulus of cartilage is similar to that of the synthetic rubber of a car tyre. The cartilage surface is rough and in elderly specimens the centre line average is 2-75 mum. The friction force generated in reciprocating tests shows that both cartilage and synovial fluid are important in lubrication. The viscosity-shear rate relationships of normal synovial fluid show that it is non-Newtonian. Osteoarthrosic fluid is less so and rheumatoid fluid is more nearly Newtonian. Experiments with hip joints in a pendulum machine show that fluid film lubrication obtains at some phases of joint action. Boundary lubrication prevails under certain conditions and has been examined with a reciprocating friction machine. Digestion of hyaluronate does not alter the boundary lubrication, but trypsin digestion does. Surface active substances (lauryl sulphate and cetyl 3-ammonium bromide) give a lubricating ability similar to that of synovial fluid. The effectiveness of the two substances varies with pH.
A new pressure-sensitive conductive rubber sensor was used for investigation of the pressure distribution through the radio-ulno-carpal joint. Twelve of these transducers were placed in the radio-ulno-carpal joint. Pressure was measured in seven different wrist positions under loads incrementally increasing from 0 to 12 kg. Half of the sensors showed less than 0.5 MPa, even at maximum load, while a high-pressure area was located palmary in each fossa. The peak pressure measured in the wrist neutral position was 2.4 MPa on the scaphoid fossa, 1.5 MPa on the lunate fossa, and 1.1 MPa on the triangular fibrocartilage with a 10 kg load. The peak pressure ratio between the scaphoid and the lunate was 1.7 in the neutral wrist position. This increased in radial deviation to 2.9 and decreased in ulnar deviation to 0.8. The force-transmission ratio was 50% through the scaphoid fossa, 35% through the lunate fossa, and 15% through the triangular fibrocartilage in the neutral position. The advantage of this sensor is that it is thin and flexible and provides reliable reproducible quasi-instantaneous measurements.
The relationship between the amount of force transmitted through the distal ulna and seven radiologically apparent anatomic parameters (ulnar variance, radial tilt, palmar tilt, lunate fossa angulation, carpal height, carpal ulnar distance, and ulnar head inclination) was examined in 58 fresh cadaver forearms. A positive, although very weak, relationship was found between the amount of force and the ulnar variance (r = 0.44). This suggests that a clinically more positive ulnar variant wrist will not necessarily cause more force to be transmitted to the head of the ulna than a wrist with a more negative ulnar variance, primarily because the triangular fibro-cartilage complex is thicker in arms with a more negative ulnar variance. Changes in ulnar variance of a forearm due to ulnar lengthening or radial shortening do, however, dramatically alter the force transmission. No other relationships were found between the ulnar force and the other radiologic parameters.
One hundred sixty-five cadaveric wrists were dissected to assess the incidence of a medial (hamate) facet on the lunate and any associated pathologic conditions. Forty-seven of these specimens and 137 clinical patients' radiographs were reviewed to attempt to recognize and further assess the incidence of a medial (hamate) facet on the lunate. Two types of lunate were identified. Type I, in which there was no medial facet, was evident in 34.5% of the dissected specimens and type II, in which there was a medial facet, was evident in 65.5% of the dissected specimens. The medial facets in the type II lunates ranged from a shallow 1 mm facet to a deep 6 mm facet. Significant cartilage erosion with exposed subchondral bone at the proximal pole of the hamate, which was not identifiable by radiograph, was evident at dissection in 44.4% of the type II lunates, while none (0%) of the type I lunates had such associated hamate pathologic conditions. This type II lunate, with the high incidence of associated hamate pathology, may be an unidentified cause of wrist pain on the ulnar side.
Degenerative arthritis of the wrist follows very specific patterns from onset to terminal severe bone and joint destruction. About 95% of them occur as periscaphoid area problems: SLAC (scapholunate advanced collapse pattern) wrist (55%), triscaphe arthritis (26%), and a combination of the two (14%). In SLAC wrist, the repeating sequence of degenerative change is based on and caused by articular alignment problems between the scaphoid and the radius. Changes then progress between the capitate and the lunate that are secondary to carpal collapse. In triscaphe arthritis, the degenerative change is limited to between the trapezium, trapezoid, and distal scaphoid. SLAC procedure (fusion of the capitate, lunate, hamate, and triquetrum along with silastic scaphoid implant) for SLAC wrists and triscaphe arthrodesis (fusion of the scaphoid, trapezium, and trapezoid) for triscaphe arthritis, are designed to make maximum use of undamaged structures and to maintain full-power, painless, mobile human wrists.
The morphologic features of the carpal bones and their contacts play a highly significant role in the mechanism of the wrist joint. Displacements of the proximal carpal bones in both flexion and deviation of the hand take place in longitudinal articulation chains that are linked one to another. This concept is supported by the following observations: differences in curvature between the facets of the proximal carpals at the radiocarpal level suggest that simultaneous movements occur at the midcarpal level; the position of the proximal carpal bones is determined by their position with respect to both the distal carpal bones and the radius; displacements of the proximal carpal bones to the distal carpals result in swerving motions in the transverse plane in addition to dorsopalmar rotation (as a result, the volar rotated position of a proximal carpal in the volar flexed hand will differ from its position in the radial deviated hand and the positions of the proximal carpals in the dorsiflexed hand will differ from these in the ulnar deviated hand); and the three articulation chains, radial, central, and ulnar, cannot function on their own, since the linkage in the longitudinal direction is associated to a transverse linkage by the mutual joint contacts between the chains and by ligamentous interconnections.
Four thousand wrist x-ray films were reviewed to establish the pattern of sequential changes in degenerative arthritis of the wrist. After eliminating all other arthritides, we studied 210 cases of degenerative arthritis. The most common pattern (57%) was arthritis between the scaphoid, lunate, and radius; 27% of cases occurred between the scaphoid, trapezium, and trapezoid; a combination of these two patterns occurred in 15%. Twenty operations were performed on 19 patients with the scapholunate advanced collapse pattern. Eighteen of 19 patients had less pain postoperatively and none required pain medication. Flexion-extension and radial-ulnar deviation motions showed considerable improvement after the operation.
The distal radioulnar joint is an intricate part of wrist function. The radius and hand move in relation to, and function about, the distal ulna. Significant loads are transmitted to the forearm unit through the distal ulna via the triangular fibrocartilage. The anatomic relations between the distal radius and ulna and the ulnar carpus are precise, and even minor modifications in these relations leads to significant load-pattern changes. The authors can only speculate on the clinical ramifications of such load-pattern modifications. Since M. DeSault's dissertation on dislocation of the distal radius, published in 1791, much has been written on injuries to, and afflictions of, the radiocarpal area. Although injuries and afflictions in this area undoubtedly have not changed throughout the years, an increasing variety of ulnar wrist syndromes and treatment programs are being recognized. This phenomenon attests not only to the need for continuous investigations of wrist problems but also to the great excitement that presently exists in the field. Better understanding of the anatomy and newer knowledge of the biomechanics of the distal radioulnar joint should herald an ulnar wrist renaissance.
Fusion of selected bones of the carpus, occasionally combined with the radius or metacarpal bases, has been used to treat a wide variety of serious pathologic conditions of the wrist. Indications include severe localized degenerative arthritis and posttraumatic changes secondary to subluxation, dislocation, or residual instability resulting in significant pain. The procedure was performed on 28 wrists in 26 patients. There were three failures to obtain union initially, two of which united after secondary grafting procedures. All patients had less pain and most had functional, though limited, ranges of wrist motion. Limited wrist arthrodesis provides a workable alternative to complete wrist fusion and Silastic wrist arthroplasty for many wrists with localized destruction.
The anatomy and function of the triangular fibrocartilage complex (TFCC) of the wrist was studied through anatomic dissections and biomechanical testing of 61 specimens. The TFCC was found to be a homogenous structure composed of, but not dissectable into, the articular disc, the dorsal and volar radioulnar ligaments, the meniscus homologue, the ulnar collateral ligament, and the sheath of the extensor carpi ulnaris. The TFCC was found to be perforated in 53% of specimens dissected, and all of the wrists with a demonstrable perforation showed evidence of damage or erosion of the cartilage of the lunate and/or distal ulna. Biomechanical studies suggest that the TFCC functions both as a cushion for the ulnar carpus and as a major stabilizer of the distal radioulnar joint. Perforations of the TFCC can result in the ulna-lunate abutment and cartilage erosion. Since excision of the TFCC may lead to ulnolunate abutment, chronic wrist pain, and/or instability of the distal radioulnar joint, it is not recommended.
Patients with scapholunate advanced collapse (SLAC) wrist do not have to undergo total wrist arthrodesis; the SLAC pattern spares the radiolunate articulation, providing a basis for salvage. We report the results of 100 cases in which a technique comprised of scaphoid excision and limited wrist arthrodesis was used. The average followup period of 44 months revealed excellent functional status and a high rate of patient satisfaction. The majority of employed patients were able to return to their original jobs, and many chose to resume wrist-related recreational activities. Pain relief was good to excellent in most cases. Extension/flexion averaged 72 degrees (53% of a normal opposite wrist), radioulnar deviation 37 degrees (59%), and grip strength 80% of the opposite side. X-ray films revealed only two instances of radiolunate destruction, both in conjunction with ulnar translation of the carpus. The other 98 patients demonstrated a well-preserved radiolunate joint regardless of followup interval. Complications were few. Nonunion occurred in three cases. A dorsal impingement of the capitate and radius (12%) was felt to be technique-related and avoidable by careful capitolunate alignment.
The purpose of the present study was to evaluate the accuracy of peripheral quantitative computed tomography (pQCT) in measuring the thickness of the radial cortex. Thirty left forearm specimens were scanned on an XCT 960 Stratec pQCT device using a 2.5 mm thick slice at the junction of the middle and the distal third of the radius. Cortical and trabecular areas were assessed using a threshold procedure; cortical thickness was subsequently calculated assuming a circular ring model for the radius. Cortical thickness was also measured on the true shape of bone using an iterative contour detection procedure. Subsequently 2.5 mm thick resin-embedded cylindrical radial specimens, matched with the site of pQCT examination, were obtained and contact radiographs were performed. After tenfold magnification, the cortical and trabecular areas of the specimens were measured using computerized planimetry and cortical thickness was calculated assuming a circular ring model. The cortical thickness could be assessed by pQCT in all cases using the threshold algorithm (mean (SD) 2.51 (0.58) mm) and in 21 cases could be directly measured on the true shape of bone (2.62 (0.32) mm). The cortical thickness of the specimens showed good correlation and high proportionality with that measured using pQCT with either the threshold algorithm (r = 0.941, slope = 0.976) or the iterative contour detection procedure (r = 0.883, slope = 0.987). In conclusion, pQCT is able to assess the thickness of the radial cortex, at the junction of the middle and the distal third, with high accuracy.
Limited wrist arthrodesis is a useful method for treating specific carpal disorders that maximizes residual wrist motion and strength while eliminating pain. Selective fusion of specific carpal units can be used in degenerative arthritis, rotary subluxation of the scaphoid, midcarpal instability, scaphoid nonunion, Kienbock's disease, and congenital synchondrosis or partial fusion of specific carpal joints. This report presents our experience with more than 1000 limited wrist arthrodeses, and provides a review of the indications and technical considerations for specific intercarpal fusions, and subsequent results. To date this is the largest series of intercarpal arthrodeses and the study has demonstrated that these techniques are reliable and effective in dealing with a wide range of wrist disorders.
To examine the ability of activity of daily living (ADL)-impaired older adults to successfully rise, and, when successful, the time taken to rise, from a bed and chair under varying rise task demands.
Seven congregate housing facilities
Congregate housing residents (n = 116, mean age 82) who admitted to requiring assistance (such as from a person, equipment, or device) in performing at least one of the following mobility-related ADLs: transferring, walking, bathing, and toileting.
Subjects performed a series of bed and chair rise tasks where the rise task demand varied according to the head of bed (HOB) height, chair seat height, and use of hands. Bed rise tasks included supine to sit-to-edge, sit up in bed with hand use, and sit up in bed without hands, all performed from a bed where the HOB was adjusted to 0, 30, and 45 degrees elevations; roll to side-lying then rise (HOB 0 degrees); and supine to stand (HOB 0 degrees). Chair seat heights were adjusted according to the percent of the distance between the floor and the knee (% FK), and included rises (1) with hands and then without hands at 140, 120, 100, and 80% FK; (2) from a reclining (105 degrees at chair back) and tilting (seat tilted 10 degrees posteriorly) chair (100% FK); and (3) from a 80% FK seat height with a 4-inch cushion added, with and then without hands. Logistic regression for repeated measures was used to test for differences between tasks in the ability to rise. After log transformation of rise time, a linear effects model was used to compare rise time between tasks.
The median total number of tasks successfully completed was 18 (range, 3-21). Nearly all subjects were able to rise from positions where the starting surface was elevated as long as hand use was unlimited. With the HOB at 30 or 45 degrees essentially all subjects could complete supine to sit-to-edge and sit up with hands. Essentially all subjects could rise from a seat height at 140, 120, and 100% FK as long as hand use was allowed. A small group (8-10%) of subjects was dependent upon hand use to perform the least challenging tasks, such as 140% FK without hands chair rise and 45 degrees sit up without hands. This dependency upon hand use increased significantly as the demand of the task increased, that is, as the HOB or seat height was lowered. Approximately three-quarters of the sample could not rise from a flat (0 degrees HOB elevation) bed or low (80% FK) chair when hand use was not allowed. Similar trends were seen in rise performance time, that is, performance times tended to increase as the HOB or chair seat elevation declined and as hand use was limited. Total self-reported ADL disability, compared to the single ADL transferring item, was a stronger predictor of rise ability and timed rise performance, particularly for chair rise tasks.
Lowering HOB height and seat height increased bed and chair rise task difficulty, particularly when hand use was restricted. Restricting hand use in low HOB height or lowered seat height conditions may help to identify older adults with declining rise ability. Yet, many of those who could not rise under "without hands" conditions could rise under "with hands" conditions, suggesting that dependency on hand use may be a marker of progressive rise impairment but may not predict day-to-day natural milieu rise performance. Intertask differences in performance time may be statistically significant but are clinically small. Given the relationship between self-reported ADL disability and rise performance, impaired rise performance may be considered a marker for ADL disability. These bed and chair rise tasks can serve as outcomes for an intervention to improve bed and chair rise ability and might also be used in future studies to quantify improvements or declines in function over time, to refine physical therapy protocols, and to examine the effect of bed and chair design modifications on bed and chai
The ligaments of the wrist are responsible for guiding and constraining the complex motion of the carpal bones relative to the forearm bones, the metacarpals, and contiguous carpal bones. The majority of wrist ligaments are found within the joint capsule as organized thickenings composed of parallel collagen fascicles, small caliber nerves and blood vessels, and lined on their deep surfaces by synoviocytes. The palmar radiocarpal ligament complex is composed of the radioscaphocapitate, long radiolunate, radioscapholunate and short radiolunate ligaments. The ulnocarpal ligaments include the ulnolunate, ulnotriquetral and ulnocapitate ligaments. Dorsally, the radiocarpal joint is spanned by the dorsal radiocarpal ligament. Palmar ligaments connecting the proximal and distal carpal rows include the scaphotrapeziotrapezoid, scaphocapitate, triquetrocapitate and triquetrohamate ligaments. Within each row are interosseous ligaments connecting adjacent carpal bones, each divisible into dorsal and palmar components. There are unique regions within some of the ligaments, such as a zone of fibrocartilage in the proximal regions of the scapholunate and lunotriquetral interosseous ligaments, and strong deep regions connecting the trapezoid, capitate, and hamate. The distal radioulnar joint is connected by the triangular fibrocartilage complex, composed of a fibrocartilaginous disc and the palmar and dorsal radioulnar ligaments. The ulnocarpal ligaments attach to the palmar radioulnar ligament rather than directly to the ulna, allowing increased independence between wrist and forearm motion.
To assess hand function in accordance with its accepted definition and to compare the results of three different assessment techniques.
A clinical-type assessment was used together with measurement of pinch grip and three-dimensional biomechanical trials.
Traditional clinical assessment may not relate to a patient's actual hand function. If hand function is defined as "the ability to use the hand in daily activities" then it is more appropriate to measure the forces available for performing everyday tasks using biomechanical tests.
Eight female patients with rheumatoid arthritis and eight control subjects were recruited for the study. Volunteers underwent a clinical-type assessment using a six-task activity board. Lateral pinch grip of both hands was measured using a custom-built transducer. Biomechanical trials were conducted using a 6 degree-of-freedom transducer and 6-camera motion analysis.
Functional differences between the two subject groups were apparent using all three methods of assessment. Pinch strength correlated well with the biomechanical trial data but results from the clinical-type assessment provided only a weak correlation.
Clinical-type assessments do not give an accurate measure of hand function. Pinch strength measurements can provide a cost-effective alternative to full biomechanical analysis.
Traditional functional assessment uses measurements of grip or pinch strength and range of motion together with a subjective assessment of activities of daily living. This study demonstrates that pinch strength measurements can provide an accurate measure of hand function. The results from activity-board trials do not reflect hand ability and are of limited use for hand evaluation.
A finite element model accounting for large sliding frictional contact requires, depending on the type of contact algorithm in use, the definition of many numerical parameters such as contact stiffness, convergence norm and tolerance, compenetration monitoring, over-relaxing factors, etc. All these parameters do not have a physical meaning and thus they cannot be measured experimentally. This makes their identification quite complex. The aim of this study was to investigate the role of parameter identification on the accuracy of results produced by finite element models accounting for bone-implant frictional contact, when the Penalty method is used. The sensitivity analysis of several numerical parameters that may govern the state of results was carried out. Two parameters, contact stiffness and convergence tolerance, were found to play a crucial role in establishing the accuracy of the finite element results. Based on the achieved results it was stated that any numerical-only study involving contact non-linearity and omitting careful qualification of the model limits should be rejected from any peer-reviewed journal.
We measured the peak hand impact force involved in bimanually arresting a forward fall to the ground from a 1-m shoulder height in five healthy young males. The effects of three different subject instruction sets: "arrest the fall naturally"; "keep the head as far from the ground as possible"; and "minimize the peak hand forces" were studied by measuring body segment kinematics, ground reaction forces, and upper-extremity myoelectric activity. The hypotheses were tested that the (a) arrest strategy did not influence peak impact force, (b) arm configuration, impact velocity and upper-extremity electromyography (EMG) levels correlate to the peak impact force (c) and impacting the ground with one hand leading the other does not increase the impact force over that obtained with simultaneous hand use. The results show that these subjects were able to volitionally decrease the peak impact force at the wrist by an average of 27% compared with a "natural landing" (p=0.014) and 40% compared with a "stiff-arm landing" (p<0.0005). The magnitude of the peak unilateral wrist force varied from 0.65 to 1.7 body weight for these moderate falls onto a padded surface. Peak force correlated with the elbow angle at impact, wrist velocity at impact and with pre-EMG triceps activity. The force was not significantly higher for non-simultaneous hand impacts. We conclude that fall arrest strategy can substantially alter the peak impact forces applied to the distal forearm during a fall arrest. Therefore, the fall arrest strategy likely influences wrist injury risk independent of bone strength.
The purpose of this study was to accurately quantify three-dimensional in vivo kinematics of all carpal bones in flexion and extension and radial and ulnar deviation.
The right wrists of 11 healthy volunteers were imaged by spiral CT with rotational increments of 5 degrees during ulnar-radial deviation and of five of them also during flexion-extension motion. One regular-dose scan was used and the subsequent scans during wrist motion were performed with one-tenth of the regular dose. A three-dimensional matching technique using the internal structure of the bones was developed to trace the relative translations and rotations of the carpal bones very accurately.
Most of our results are in concordance with previously published in vitro data. We could, among others, substantiate proof to the statement that there is more than one kinematic pattern of the scaphoid. Furthermore, we could accurately describe small adaptive intercarpal motions in vivo of the distal carpal row.
To our knowledge, this is the first time the three-dimensional in vivo kinematics of all eight carpal bones is quantified accurately and non-invasively.
Kinematics of an injured wrist can be compared to these reference data. It may become possible that in this way a ligament lesion can be detected with high specificity and sensitivity, and that no other diagnostic modality will be needed. With these data we made animations with which the complex movements of the bones during different motions of the wrist can be viewed. In the future it may become possible that this analysis provides valuable information on the long-term results of operative interventions and possibly predicts results of operative techniques.
1. The prehensile movements of the hand as a whole are analysed from both an anatomical anda functional viewpoint.
2. It is shown that movements of the hand consist of two basic patterns of movements which are termed precision grip and power grip.
3. In precision grip the object is pinched between the flexor aspects of the fingers and that of the opposing thumb.
4. In power grip the object is held as in a clamp between the flexed fingers and the palm, counter pressure being applied by the thumb lying more or less in the plane of the palm.
5. These two patterns appear to cover the whole range of prehensile activity of the human hand.
Ellipsoid and toroid-shaped articulations for total wrist prostheses were evaluated using computer modeling and laboratory experiments. An ellipsoidal design was found to accommodate greater width of the concave proximal component, resulting in better capture and prosthetic stability than a toroid shape. An ellipsoid articulation also provides greater contact area through the available arc of motion. An ellipsoidal articulation is a reasonable design for total wrist arthroplasty.
Four-corner arthrodesis with scaphoid excision has been used to reduce pain and preserve functional range of motion for patients with radioscaphoid arthritis. Early results of 4-corner arthrodesis with scaphoid excision using dorsal circular plate fixation are compared with reported results in the literature.
We reviewed retrospectively the first 18 four-corner arthrodeses performed with this system by 4 hand surgeons. Two patients had revision surgery for nonunions before the study that were considered failures. Eight patients returned for final radiographs, objective examination, and functional questionnaire. The average follow-up period was 20 months (range, 13-33 mo). These results were compared with reported results in the literature using alternate fixation methods.
Radiographic union was achieved in only 3 wrists. Range of motion was 46% that of the opposite normal wrist and grip strength compared with the opposite wrist was 56%. Five patients would have the procedure again and 6 of 8 have returned to their original employment.
Four-corner arthrodesis with scaphoid excision using a circular internal fixation plate produced a high number of nonunions. Grip strength and range of motion results also were inferior to those reported in the literature.
The scaphoid plays a critical role in maintain-ing normal carpal kinematics. SLAC and SNAC wrist arthritis demonstrate the ramifications ofscaphoid pathology on wrist biomechanics. In the past, symptomatic SLAC or SNAC pathology spelled total wrist arthrodesis. Over the past 20 years there has been a movement toward limited wrist arthrodesis in the treatment of SLAC/SNAC wrists. In the long-term follow-up of four-corner fusions, patient satisfaction is high, patients are able to return to their previous vocation, and wrist function averages 60%-70% of the contralateral wrist. The Spider plate is a recent advancement in the four-corner fusion armamentarium that has thus far shown great promise in respect to fusion rates (100% in the first documented series [36]),functional range of motion, intercarpal stability[37], and patient satisfaction.