The anatomy and basic biomechanics of the wrist joint

Automatic analysis of the scapholunate distance using 4DCT imaging: normal values in the healthy wrist

AIM

Early diagnosis of scapholunate ligament (SLL) injuries is crucial to prevent progression to debilitating osteoarthritis. Four-Dimensional Computed Tomography (4DCT) is a promising dynamic imaging modality for assessing such injuries. Capitalizing on the known correlation between SLL injuries and an increased scapholunate distance (SLD), this study aims to develop a fully automatic approach to evaluate the SLD continuously during wrist motion and to apply it to a dataset of healthy wrists to establish reference values.

MATERIALS AND METHODS

50 healthy wrists were analysed in this study. All subjects performed radioulnar deviation (RUD), flexion-extension (FE), and clenching fist (CF) movements during 4DCT acquisition. A novel, automatic method was developed to continuously compute the SLD at five distinct locations within the scapholunate joint, encompassing a centre, volar, dorsal, proximal, and distal measurement.

RESULTS

The developed algorithm successfully processed datasets from all subjects. Our results showed that the SLD remained below 2 mm and exhibited minimal changes (median ranges between 0.3 mm and 0.65 mm) during RUD and CF at all measured locations. During FE, the volar and dorsal SLD changed significantly, with median ranges of 0.90 and 1.27 mm, respectively.

CONCLUSION

This study establishes a unique database of normal SLD values in healthy wrists during wrist motion. Our results indicate that, aside from RUD and CF, FE may also be important in assessing wrist kinematics. Given the labour-intensive and time-consuming nature of manual analysis of 4DCT images, the introduction of this automated algorithm enhances the clinical utility of 4DCT in diagnosing dynamic wrist injuries.

Flexed position of the wrist in the cast reliably prevents displacement after physeal Salter-Harris I and II distal radius fractures

BACKGROUND

Salter-Harris I and II fractures of the distal radius are common injuries. In our facility, immobilisation is performed in a way that counteracts angulation forces. The aim of our study was to determine whether there are significant differences between patients with and patients without a loss of reduction treated with this method and to determine what degree of flexion reliably prevents secondary displacement.

PATIENTS AND METHODS

We conducted a retrospective study of 112 patients (mean age: 12 years) who had sustained a Salter-Harris type I or II fracture of the distal radius and were treated with reduction. Patients were grouped according to fracture type and whether they sustained a loss of reduction or not. Patients were compared for gender, age, initial angulation, angulation after reduction, degree of flexion/extension of the wrist in the cast, residual angulation, duration of immobilisation, and complication rate. We also analysed whether a 45-degree flexed position of the wrist in plaster provides reliable protection against secondary displacement.

RESULTS

In group I, patients with no loss of reduction had a significantly greater degree of wrist flexion in the cast, a significantly shorter duration of immobilisation and significantly less residual angulation. Patients with an apex-volar deformity with the wrist immobilised at more than 45 degrees of flexion had no loss of reduction at all and had significantly less residual angulation compared with patients with the wrist immobilised at less than 45 degrees of flexion. In this patient group, loss of reduction was noted in 28% of cases. The patients in group II with loss of reduction showed a significantly higher angulation after the reduction. During the follow-up examination, one patient experienced physeal arrest followed by an ulnar impaction syndrome. Other complications recorded were minor.

CONCLUSIONS

In summary, based on our results, we recommend that all physeal fractures of the distal radius with an apex-volar angulation can be safely treated with reduction and immobilisation counteracting the forces of angulation. For apex-dorsal fractures, palmar flexion of 45° allows for reliable reduction.

Can a structured home-based rehabilitation program reduce dorsal central wrist pain?

OBJECTIVES

Dorsal central wrist pain, often a consequence of peri-scapholunate ligament injury, can result in a decline in functional performance. There is a scarcity of clinical data evaluating the effectiveness of conservative management on peri-scapholunate ligament injury. Conservative management includes education, immobilization with orthotic devices, scapholunate-stabilizing muscle strengthening, and proprioception training. The identification of the ligamento-muscular reflex and scapholunate-stabilizing muscles formed the rationale for a rehabilitation training program. We have devised an innovative standardized 16-week treatment program for patients with dorsal central wrist pain associated with acute peri-SL ligament injury. We hypothesized that the program can effectively reduce dorsal wrist pain and improve functional performance.

MATERIALS AND METHODS

Recruited subjects underwent the 16-week home-based program, which included immobilization and rehabilitation exercises, to improve their wrist stability. Follow-up was arranged every 4 weeks for progress monitoring. The Short-Form 12 item questionnaire version 2, power grip, pinch grip, wrist range of motion, total performance score and total pain score when performing activities of daily living were used to evaluate the effectiveness of the program. An exercise adherence questionnaire was used to evaluate adherence to the home rehabilitation program.

RESULTS

Twenty-three subjects (26 wrists) completed the program. Pain on visual analog scale improved by 5.1 cm and total pain score improved from 14.4/20 to 19.5/20. Total performance score reached 39/40, which indicated near-normal wrist function. Power grip and pinch grip increased by 22.3% and 17.8%, respectively. The physical component scale of the Short-Form 12 item questionnaire showed significant improvement, while the mental component scale did not. Overall adherence was fair.

DISCUSSION

Conservative management, including immobilization and rehabilitation training, can provide significant clinical improvement in patients with dorsal central wrist pain associated with acute peri-scapholunate ligament injury.

CONCLUSION

Standardized wrist rehabilitation can be taken as a reference treatment modality. It is an evidence-based non-invasive treatment option for clinicians and therapists.

Effects of a neuromuscular joint-protective exercise therapy program for treatment of wrist osteoarthritis: a randomized controlled trial

BACKGROUND

Individuals with wrist osteoarthritis (OA) can suffer from pain, muscular weakness, and impaired motion of the wrist, which can reduce the quality of life. While there is strong evidence that all patients with OA should receive first-line treatment with education and exercises, this approach has not yet been proposed for individuals with wrist OA. Therefore, this trial aimed to evaluate the effectiveness of a first line neuromuscular joint-protective exercise therapy program compared to a training program with range of motion (ROM) exercises in patients with wrist OA.

METHODS

In this randomized controlled trial (RCT), 48 patients with symptomatic and radiographically confirmed wrist OA were randomly allocated to a 12-week self-management program with either a neuromuscular joint-protective exercise therapy program (intervention group) or a training program with ROM exercises only (control group). Our primary outcome measure was the Patient-Rated Wrist Evaluation (PRWE) with secondary outcome measures of grip strength, range of wrist motion, the Numerical Pain Rating, Scale (NPRS), the Disabilities of the Arm, Shoulder, and Hand (DASH) and the Generalized Self-Efficacy Scale (GSES). The outcome measures were evaluated by a blinded assessor at baseline and 12 weeks. Between-groups differences were analyzed using the Mann-Whitney U test and within-group differences were analyzed with the Wilcoxon signed-rank test.

RESULTS

A total of 41 participants were analyzed at 12 weeks. There were no significant differences in PRWE between the groups at 12 weeks (p = 0.27). However, DASH improved significantly in the intervention group compared to the control group (p = 0.02) and NPRS on load within the intervention group (p = 0.006). The difference in DASH should be interpreted with caution since it could be due to a non-significant increase (worsening) from baseline in the control group in combination with a non-significant decrease (improvement) in the intervention group.

CONCLUSIONS

This RCT showed that the novel neuromuscular joint-protective exercise therapy program was not superior in reducing pain and improving function compared to a training program with ROM exercises at 12 weeks. Future research is warranted to evaluate the effectiveness of forthcoming exercise therapy treatment programs for patients with wrist OA.

TRIAL REGISTRATION

ClinicalTrials.gov, NCT05367817. Retrospectively registered on 10/05/2022. https://clinicaltrials.gov .

Scapholunate Instability: Diagnosis and Management - Anatomy, Kinematics, and Clinical Assessment - Part I

Injuries to the scapholunate joint are the most frequent cause of carpal instability. The sequelae of these injuries account for considerable morbidity, and if left untreated, may lead to scapholunate advanced collapse and progressive deterioration of the carpus. Rupture of the scapholunate interosseous ligament and its critical stabilizers causes dyssynchronous motion between the scaphoid and lunate. Additional ligament injury or attenuation leads to rotary subluxation of the scaphoid and increased scapholunate gap. Intervention for scapholunate instability is aimed at halting the degenerative process by restoring ligament integrity and normalizing carpal kinematics. In the first section of this review, we discuss the anatomy, kinematics, and biomechanical properties of the scapholunate ligament as well as its critical ligament stabilizers. We provide a foundation for understanding the spectrum of scapholunate ligament instability and incorporate meaningful new anatomical insights that influence treatment considerations. The purpose is to provide an update regarding the anatomy of the scapholunate ligament complex, importance of the critical ligament stabilizers of the proximal carpal row, introduction of safe technique to surgically expose the scaphoid and lunate, as well as pathoanatomy as it pertains to the treatment of scapholunate dissociation. In the second section of this review, we propose a novel ligament-based treatment algorithm based on the stage of injury, degree and nature of ligament damage, and presence of arthritic changes.

Anatomical study of the dorsal capsulo-scapholunate septum using high frequency ultrasonography

INTRODUCTION

The dorsal capsulo-scapholunate septum (DCSS) is a recently described capsuloligamentous structure between the dorsal bundle of the scapholunate ligament (SLL) and the joint capsule of the wrist. It acts a secondary stabilizer of the scapholunate joint. The aim of this study was to evaluate the visibility and normal appearance of DCSS on high frequency ultrasound.

HYPOTHESIS

The DCSS can be analyzed using high frequency ultrasound.

MATERIALS AND METHODS

Three cadaveric wrists were dissected in order to study the DCSS; one without labeling and the other two after labeling under ultrasound guidance. On two other wrists, a correlation between the structure considered to be the DCSS on ultrasound and the corresponding CT arthrography and anatomical sections was carried out. Finally, sagittal ultrasound sections of the DCSS region on 42 healthy wrists were analyzed retrospectively.

RESULTS

During dissection, the DCSS corresponded to a fibrous structure extending to the dorsal surface of the scaphoid and lunate, with certain fibers converging towards the SLL. On high-frequency ultrasound, a hyperechoic fibrillar structure was visualized at the theoretical position of the DCSS. The dissections performed after ultrasound-guided transfixion showed that its limits corresponded to the limits of the DCSS. The anatomical, CT arthrography and ultrasound sections in the DCSS region were concordant. The DCSS was retrospectively visible on at least one reference ultrasound slice in 90.5% of healthy wrists, and was always hyperechoic. Its average thickness was 1.38±0.24mm.

DISCUSSION

Our study describes the normal sonographic characteristics of the DCSS, visible in a majority of healthy patients on high-frequency ultrasound. The analysis of the sonographic characteristics of the DCSS in the context of acute wrist trauma should be evaluated, and a diagnostic decision tree has been proposed.

LEVEL OF EVIDENCE

IV.

Campanacci Grade III Giant Cell Tumors of Distal End Radius Treated With Wide Excision and Reconstruction: A Retrospective Case Series

Introduction

Campanacci Grade III Giant Cell tumors of the distal radius are difficult to manage as they are associated with a high recurrence rate. Wide excision of the distal radius and reconstruction with an ipsilateral proximal fibula or ulnar translocation reduces the recurrence rate significantly and gives acceptable function to the hand and wrist.

Methods and materials

This was a retrospective study of eight patients with Campanacci grade III giant cell tumors of distal radius treated with wide excision of distal radius followed by reconstruction at our institute. Four cases were operated on with ulnar translocation and four cases were operated on with ipsilateral proximal fibula grafting after wide excision of the distal radius. Patients were studied for the Musculoskeletal Tumor Society (MSTS) score and visual analogue scale (VAS) score for pain at one year, recurrence, and complications.

Results

The mean MSTS score of the total series was 24.75 ± 1.6. The mean VAS score for the total series was 1.62 ± 0.4. Of the eight cases, two cases had a recurrence, one patient had persistent wrist paint, and two patients had wrist subluxation.

Conclusion

Wide excision of the distal radius followed by reconstruction with a proximal fibula or ulnar translocation is a good option to avoid repeated surgeries in patients with Campanacci grade III giant cell tumors of the distal radius and achieve acceptable functional results for the wrist and hand.

The Dorsal Ligament Complex: A Cadaveric, Histology, and Imaging Study

PURPOSE

The distinction between the dorsal intercarpal (DIC) and dorsal scaphotriquetral (DST) ligaments is imprecise and unclear in the literature. The purpose of our cadaveric study was to define the origins, insertions, and anatomic relationships of the dorsal wrist ligaments and relate these anatomic findings to magnetic resonance imaging (MRI) scans and histology.

METHODS

The study included 17 unmatched fresh-frozen cadaveric specimens (7 male and 10 female), with a mean age of 67.1 years (range, 48-86 years). Wrists with arthritis or carpal malalignment were excluded. Ligaments were dissected and insertion sites were recorded in the radioulnar (width) and proximodistal (length) dimensions, centered at the midpoints of the insertion. Three cadaveric specimens underwent a histologic analysis to demonstrate ligament composition and insertion sites. Three additional cadavers underwent MRI, from which 3-dimensional models were built to model ligament topography.

RESULTS

The conjoined triquetral insertion of the DIC, DST, and dorsal radiocarpal (DRC) measured 88.5 ± 6.4 mm². In each specimen, there were 2 distinct deep and superficial components of intercarpal fibers. The deep component inserted on the lunate with an area of 59.0 ± 5.0 mm². The deep and superficial components diverged as they coursed radially. The superficial component proceeded to the scaphoid ridge, trapezium, and trapezoid, whereas the deep component inserted on the proximal row. The deep fibers blended distally from their lunate insertion with the DST, forming a robust, 2.9 ± 0.8-mm wide extension over the dorsal capitate. The DRC inserted on the lunate, proximal to the DIC and DST insertions, with an area of 23.9 ± 5.4 mm².

CONCLUSIONS

The dorsal ligament complex forms a firm link across the proximal carpal row and the DST provides extension of the proximal row over the capitate.

CLINICAL RELEVANCE

This information can guide surgeons while performing a dorsal approach to the wrist and repairing traumatic ligament disruption.

Comparison of Optimization Strategies for Musculoskeletal Modeling of the Wrist for Therapy Planning in Case of Total Wrist Arthroplasty

The human wrist joint is an elegant mechanism. The wrist allows the positioning and orienting of the hand to the forearm. The computational modeling of the human hand, especially of the wrist joint, can reveal important information about biomechanical mechanisms and provide the basis for its dysfunction and pathologies. For instance, this could be used for therapy planning in total wrist arthroplasty (TWA). In this study, different optimization methods and sensitivity analyses of anatomical parameters for musculoskeletal modeling were presented. Optimization includes finding the best available value of an objective function, including a variety of different types of objective functions. In the simplest case, optimization consists of maximizing or minimizing a function by systematically choosing input values from within an allowed set and computing the value of the function. Optimization techniques are used in many facets, such as the model building of joints or joint systems such as the wrist. The purpose of this study is to show the variability and influence of the included information for modeling, investigating the biomechanical function and load situation of the joint in representative scenarios. These possibilities to take them into account by an optimization and seem essential for the application of computational modeling to joint pathologies.

Anatomy, Biomechanics, and Loads of the Wrist Joint

The wrist is by far the most differentiated section of the musculoskeletal system. The spectrum of wrist injuries ranges from minor injuries to complex traumas with simultaneous loss of functions, resulting in enormous economic costs. A proper understanding of the anatomy and biomechanics is essential for effective treatment, whether conservative or surgical; this applies to the wrist no less than to other parts of the human body. Here; information on the wrist anatomy; kinematics; and biomechanical behavior is presented, commencing with a brief explanation of the structure of its hard and soft tissues. Eight carpal bones in combination with two forearm bones (radius and ulna) construct the wrist joint. The motion of the wrist joint is initiated by the muscles of the forearm, and strong and short ligaments ensure the stability of the wrist. All of these components are essential to bringing functions to the wrist joint because these structures allow wrist mobility and sustainability. In addition, the kinematics of the wrist joint is presented and different biomechanical model approaches. The therapeutic (surgical) restoration of the balance between the load–bearing capacity and the actual stress on a joint is the prerequisite for a lifelong and trouble-free function of a joint. Regarding the complex clinical problems, however, a valid biomechanical wrist joint model would be necessary as assistance, to improve the success of systematized therapies based on computer–aided model–based planning and intervention.

Is the Dorsal Fiber-Splitting Approach to the Wrist Safe? A Kinematic Analysis and Introduction of the "Window" Approach

PURPOSE

To compare the kinematic effects of the dorsal fiber-splitting approach for scapholunate ligament repair to a dorsal "window" approach that spares all ligaments.

METHODS

We randomized 24 fresh-frozen paired cadaveric forearms to either the dorsal fiber-splitting capsulotomy approach (FSC) or the dorsal window approach (window) following scapholunate interosseous ligament (SLIL) division. Loaded fluoroscopic radiographs were obtained after each of the 4 testing conditions following cyclic loading (200 cycles; 71 N): (1) intact SLIL, (2) SLIL-division, (3) surgical approach, and (4) closure. FSC specimens were randomly allocated to 2 subgroups for closure with either a suture anchor (n = 6) or a simple running suture closure (n = 6). Radiographic parameter measurements included the scapholunate gap, radiolunate angle, scapholunate angle, and dorsal scaphoid translation.

RESULTS

Following the FSC, there were significant alterations in all radiographic parameters when compared with the intact and SLIL-division conditions. The window approach did not result in significant changes in any radiographic parameter. When compared to the window approach, all radiographic parameters of the FSC approach were significantly altered. Following closure with suture anchors in the FSC group, radiographic parameters improved, whereas with standard closure they failed to do so. Despite anchor closure, dorsal scaphoid translation, radiolunate angle, and scapholunate angle all remained elevated compared with scapholunate-divided wrists.

CONCLUSIONS

The FSC produced significant changes in carpal posture under load, including scapholunate diastasis, dorsal intercalated segment instability, and dorsal scaphoid translation in SLIL-deficient wrists. The window approach preserved the critical dorsal ligament stabilizers and did not produce changes in carpal posture.

CLINICAL RELEVANCE

The FSC may create iatrogenic changes in carpal posture that cannot be fully corrected with standard or anchor closure. The window approach does not alter carpal posture and should be considered when performing surgical procedures on the scaphoid or lunate.

Carpal Kinematics in Madelung Deformity

PURPOSE

Various skeletal and soft tissue abnormalities have been identified in Madelung deformity and have been hypothesized to play a causal role in its progressive symptomatology; however, our pathological understanding of these changes remains limited. In this study, we biomechanically assessed the Madelung deformity wrist, using 4-dimensional computed tomography imaging.

METHODS

Nine Madelung deformity wrists (5 patients; age, 24 ± 5 y) and 18 healthy wrists (9 volunteers; age, 28 ± 3 y) underwent 4-dimensional imaging during flexion-extension motion and radioulnar deviation. Carpal kinematics and radiocarpal joint parameters were quantified and compared.

RESULTS

In Madelung deformity wrists, significantly decreased rotation was seen in the lunate (-4.6°) and the triquetrum (-4.8°) during flexion-extension motion. During radioulnar deviation, significant decreases were visible in lunate bone translation (-0.7 mm), triquetrum bone translation (-0.6 mm), and triquetrum bone rotation (-1.9°). Patients had significantly decreased articulating surface areas of the scaphoid (1.4 ± 0.2 cm² versus 1.6 ± 0.2 cm²) and lunate (1.2 ± 0.4 cm² versus 1.5 ± 0.3 cm²) fossa, and significantly increased radioscaphoid (1.3 ± 0.1 mm versus 1.2 ± 0.1 mm) and radiolunate (1.6 ± 0.2 mm versus 1.3 ± 0.3 mm) joint space thicknesses.

CONCLUSIONS

There is a decreased mobility of the lunate and triquetrum bones in Madelung deformity.

CLINICAL RELEVANCE

Four-dimensional imaging could be used in future studies that investigate the effect of surgical ligament release on carpal kinematics and subsequent wrist mobility.

Single-Cut Single-Screw Capitate-Shortening Osteotomy for Kienbock's Disease

Background  Kienbock's disease, in spite of an uncertain natural history, is known to cause lunate compromise, leading to central column collapse, carpal instability, and degenerative arthritis of the wrist. Joint leveling procedures are performed in the early stages of Kienbock's disease to "unload" the lunate. Capitate shortening is the preferred procedure in Kienbock's patients with positive ulnar variance. Description of Technique  We describe the rationale and a simplified technique of capitate shortening in early Kienbock's disease. This is a single-cut osteotomy with single-screw stabilization. Patients and Methods  We have performed this technique in three cases. We present a case of a 26-year-old male who presented with a 1-year history of pain in his right wrist. Radiology performed demonstrated lunate sclerosis. Diagnostic arthroscopy revealed healthy articular surfaces. Single osteotomy capitate shortening was performed with an oscillating saw and fixed with a single cannulated compression screw. A shortening of 1.5mm was obtained with this technique. Results  At 1- to 2-year follow-up, all three patients had considerable pain relief but did not have a complete resolution of pain. There was a significant improvement in function and grip strength. There have been no cases with infection, nonunion, avascular necrosis or a need for a salvage procedure. Conclusion  The simplified technique of capitate shortening is easy to perform, less traumatic to the capitate vascularity, and leads to good short-term functional results.

Anatomical relationship of palmar carpal bone landmarks used in locating the lunate and capitate during palpation: A cadaveric investigation

STUDY DESIGN

Descriptive in situ cadaveric study.

INTRODUCTION

Performing accurately directed examination and treatment to the wrist requires clinicians to orient to carpal bone structures.

PURPOSE OF THE STUDY

To examine the anatomical relationships that exist within the wrist-hand complex and identify the accuracy of surface anatomy mapping strategies for localizing anatomical landmarks using a palmar approach.

METHODS

Twenty-three embalmed cadavers were dissected using standardized procedures. Metal markers were placed in the most prominent palmar landmark of key carpal structures. Relationships between the most prominent palpation landmarks and the carpal bones of interest were visualized using fluoroscopy.

RESULTS

The most successful methods of palmar capitate localization included the midpoint of a line from trapezium tubercle to pisiform; the midpoint of a line from scaphoid tubercle to hamate hook; or the intersection (cross) of these 2 diagonal lines, with successful capitate identification 100% (23/23) of the time. The most successful method for locating the lunate included the midpoint of a line from the radial styloid process to the ulnar styloid process, which identified the lunate in 100% (23/23) of cases.

DISCUSSION

The results of this cadaveric anatomical relationship study support the use of the midpoint of a line from pisiform to trapezium tubercle, the midpoint of a line from scaphoid tubercle to hamate hook, or a combination (cross) of these lines to locate the capitate from a palmar approach. In addition, the anatomical relationships examined in this study support the use of the midpoint of a line from the radial styloid process to ulnar styloid process to locate the lunate from a palmar approach. Knowledge of these anatomical relationships may improve the clinician's confidence in locating the capitate and lunate during intercarpal examination, special testing, and treatment.

CONCLUSION

Results of this study provide information of the anatomical relationships of the carpal bones from a palmar approach, giving clinicians a foundation for proper orientation to the carpal bones during clinical examination and intervention. Further research is needed to evaluate the reliability and accuracy of these methods for surface palpation on live patients.

Performance evaluation of surgical techniques for treatment of scapholunate instability in a type II wrist

We investigated the performance of three tenodesis techniques, modified Brunelli, Corella, and scapholunate axis (SLAM) methods in repairing scapholunate interosseous ligament (SLIL) disruption for a type II wrist using finite element-based virtual surgery and compared the results with those of a previous investigation for a type I wrist. In addition, a comparison of the carpal mechanics of type I and type II wrists was undertaken in order to elucidate the difference between the two types. For the type II wrist, following simulated SLIL disruption, the Corella reconstruction technique provided a superior outcome, restoring dorsal gap, volar gap, and SL angle to within 3.5%, 7.1%, and 8.4%, respectively, of the intact wrist. Moreover, application of the ligament reconstruction techniques did not significantly alter the motion pattern of the type II and type I wrists. For the type I wrist, SLIL disruption resulted in no contact between scaphoid-lunate cartilage articulation, whereas for the type II wrist, some contact was maintained. We conclude that the Corella ligamentous reconstruction technique is best able to restore SL gap, angle, and stability following SL ligament injury for both type II and type I wrists and is able to do so without altering wrist kinematics. Our findings also support the view that type I wrists exhibit row behaviour and type II wrists column behaviour. In addition, our analysis suggests that the extra articulation between the lunate and hamate in a type II wrist may help improve stability following SL ligament injury.

Wrist essentials: the diagnosis and management of scapholunate ligament injuries

LEARNING OBJECTIVES

After studying this article, the participant should be able to: 1. Understand the pathophysiology of a scapholunate injury. 2. Understand how to diagnose scapholunate injuries 3. Formulate and carry out a surgical plan for patients with a scapholunate injury.

SUMMARY

Scapholunate ligament instability is the most common form of carpal instability. Untreated scapholunate injuries can lead to a predictable pattern of wrist arthritis. Early forms of scapholunate ligament instability can be missed, and clinical detection relies on an educated observer. This article covers the basic anatomy and biomechanics of the wrist, and reviews in detail scapholunate ligament injury. This article also reviews and discusses the current relevant topics and issues surrounding scapholunate ligament injury.

Patterns of radiocarpal joint articular cartilage wear in cadavers

The radiocarpal joint transmits about 80% of the compression forces crossing the wrist. However, primary osteoarthritis of this joint is surprisingly uncommon, suggesting that articular cartilage wear is not sufficient to produce arthritic symptoms. By examining the distal radius, scaphoid, and lunate in aged cadavers, wear patterns were charted and measured, allowing assessment of radiocarpal joint wear and mechanics. Bilateral radiocarpal joints of 16 females and 14 males (age 77.7 ± 14.4, N = 30) were exposed and measurements of the wear recorded microscopically. Wear locations were mapped, and X-Y loci and wear areas calculated. Gender right and sides compared. Over 95% of distal radius wear showed distinct radial-scaphoid and radial-lunate wear areas. These bilateral areas were in the palmar half of the distal radius. One main central wear area was seen in 95% of the scaphoid, and 97% of the lunate articular surfaces that were examined. Articular wear showed a circular pattern and was minimal in 95.7% of the surfaces, and the lunate showed the largest wear area. Wear patterns in males and females support the literature that for most ADLs the wrist is in slight extension and ulnar deviation. There are gender differences, but wear areas between sides were similar. Female wear indicates their wrist is positioned more often in a more extended and ulnarly deviated position than males. The wear patterns suggest rotational movements of the scaphoid and lunate during wrist motion and that the wrist is most often used in neutral flexion/extension to slight extension.

Studying primate carpal kinematics in three dimensions using a computed-tomography-based markerless registration method

The functional morphology of the wrist pertains to a number of important questions in primate evolutionary biology, including that of hominins. Reconstructing locomotor and manipulative capabilities of the wrist in extinct species requires a detailed understanding of wrist biomechanics in extant primates and the relationship between carpal form and function. The kinematics of carpal movement, and the role individual joints play in providing mobility and stability of the wrist, is central to such efforts. However, there have been few detailed biomechanical studies of the nonhuman primate wrist. This is largely because of the complexity of wrist morphology and the considerable technical challenges involved in tracking the movements of the many small bones that compose the carpus. The purpose of this article is to introduce and outline a method adapted from human clinical studies of three-dimensional (3D) carpal kinematics for use in a comparative context. The method employs computed tomography of primate cadaver forelimbs in increments throughout the wrist's range of motion, coupled with markerless registration of 3D polygon models based on inertial properties of each bone. The 3D kinematic principles involved in extracting motion axis parameters that describe bone movement are reviewed. In addition, a set of anatomically based coordinate systems embedded in the radius, capitate, hamate, lunate, and scaphoid is presented for the benefit of other primate functional morphologists interested in studying carpal kinematics. Finally, a brief demonstration of how the application of these methods can elucidate the mechanics of the wrist in primates illustrates the closer-packing of carpals in chimpanzees than in orangutans, which may help to stabilize the midcarpus and produce a more rigid wrist beneficial for efficient hand posturing during knuckle-walking locomotion.

Management of carpal instability in athletes

Hand and wrist injuries are common in most athletic events and sports. Carpal fractures and ligamentous injuries are common in athletes and require physicians, trainers, and therapists who treat and diagnosis these injuries to have an understanding of the carpal bone anatomy and vascularity along with the potential for progression to instability. Research is still needed to further investigate the optimal treatments of all carpal injuries in athletes along with designing new means to prevent these injuries.

Four-dimensional computed tomographic imaging in the wrist: proof of feasibility in a cadaveric model

OBJECTIVE

High-resolution real-time three-dimensional (3D) imaging of the moving wrist may provide novel insights into the pathophysiology of joint instability. The purpose of this work was to assess the feasibility of using retrospectively gated spiral computed tomography (CT) to perform four-dimensional (4D) imaging of the moving wrist joint.

MATERIALS AND METHODS

A cadaver forearm from below the elbow was mounted on a motion simulator which performed radioulnar deviation of the wrist at 30 cycles per minute. An electronic trigger from the simulator provided the "electrocardiogram" (ECG) signal required for gated reconstructions. Four-dimensional and 3D images were compared by a blinded observer for image quality and presence of artifacts.

RESULTS

Image quality of 4D images was found to be excellent at the extremes of radial and ulnar deviation (end-motion phases). Some artifacts were seen in mid-motion phases.

CONCLUSION

4D CT musculoskeletal imaging is feasible. Four-dimensional CT may allow clinicians to assess functional (dynamic) instabilities of the wrist joint.

The "ulnar fovea sign" for defining ulnar wrist pain: an analysis of sensitivity and specificity

PURPOSE

Eliciting tenderness in the region of the ulnar fovea is a possibly useful clinical test for defining the source of ulnar-sided wrist pain. Until now, no reports of the clinical sensitivity and specificity of this test have been available. Based on anecdotal observations, a hypothesis was developed stating that ulnar fovea tenderness (positive "ulnar fovea sign") is sensitive and specific in detecting two ulnar-sided wrist conditions: foveal disruption of the distal radioulnar ligaments and ulnotriquetral (UT) ligament injuries.

METHODS

The clinical records of 272 consecutive patients with wrist arthroscopy performed by the senior author from 1998 through to 2005 were reviewed. Relevant clinical and surgical data were abstracted. The ulnar fovea sign test is executed by pressing the examiner's thumb distally into the interval between the ulnar styloid process and flexor carpi ulnaris tendon, between the volar surface of the ulnar head and the pisiform. A positive ulnar fovea sign is designated when there is exquisite tenderness that the patient claims replicates their pain, with comparisons made with the contralateral side.

RESULTS

There were a total of 90 foveal disruptions and 68 UT ligament injuries diagnosed during wrist arthroscopy. The ulnar fovea sign was positive in 156 patients. The sensitivity of the fovea sign in detecting foveal disruptions and/or UT ligament injuries was 95.2%. Its specificity was 86.5%.

CONCLUSIONS

The hypothesis stating that the ulnar fovea sign is a useful clinical maneuver to detect foveal disruptions and UT ligament tears is supported. The conditions represent 2 common sources of ulnar-sided wrist pain. The differentiation between the 2 conditions may be made clinically, where UT ligament tears are typically associated with a stable distal radioulnar joint and foveal disruptions are typically associated with an unstable distal radioulnar joint.

TYPE OF STUDY/LEVEL OF EVIDENCE

Diagnostic II.

Mechanical properties of the scapholunate ligament correlate with bone mineral density measurements of the hand

The mechanical properties of the scapholunate ligament have been previously examined in small sample sizes, with ultimate load and occasionally stiffness reported. The present study examined 16 scapholunate ligaments in uniaxial extension at two rates and determined stiffness, ultimate load, and stress relaxation properties. Mean stiffness values of 66.4+/-28.6 N/mm at an elongation rate of 50 mm/min and 94.5+/-44.4 N/mm at an elongation rate of 100 mm/min were found. Relaxation behavior, determined by the percent load remaining after 100 s, was found to be 68.1+/-12%. Mean ligament ultimate loads were 357+/-110 N (n = 8). In eight specimens, failure occurred in bone. Positive correlations were observed between bone mineral density of the hand and ligament stiffness, ligament ultimate load, and bone ultimate load. No correlation was observed between bone mineral density and ligament load relaxation behavior. The results provide a comprehensive understanding of scapholunate ligament biomechanics and demonstrate a relationship between bone and ligament properties.

Splint satisfaction in the treatment of traumatic radial nerve injuries

Between the years 1986-2001, 135 patients who have had traumatic radial nerve injury, were supplied with dynamic wrist-hand orthoses (WHOs). The aim of this study is to examine the applied splints, considering aspects such as apperance, practicality of use, function, comfort and endurance. The author's assessments show that the biggest problem was due to the unaesthetic appearance of the finger extensor spring of the splints. For this reason, modification of these finger extensor outriggers has been attempted. Also, aspects of the splints such as the problems faced and regeneration of the nerve, have been considered and modifications made in order to eliminate any disfunction. This study reflects the reactions and satisfaction of 83 patients concerning the splints they have used. Conventional wire springs have been used in the splints of 71 patients, and 12 had modifications done on their outriggers. In terms of appearance, there were significant differences between modified outriggers and conventional outrigger (p < 0.05). Also, when the modified outriggers were compared in terms of appearance and durability, there was a statistically significant opinion in favour of them (p < 0.01).

Communicating defects of the triangular fibrocartilage complex without disruption of the triangular fibrocartilage: a report of two cases

Perforations or communicating defects of the triangular fibrocartilage complex have been more commonly identified after Palmer published his classification system (J Hand Surg 1989;14A:594-606). To his variants of class 1B (traumatic) ulnar avulsion with or without distal ulnar fracture, a third category may be added: defects of the ulnar collateral ligament without any associated disruption of the triangular fibrocartilage. The ulnar collateral ligament can be defined as an ulnar capsular structure between the more discrete elements of the triangular fibrocartilage and the ulnar ligaments, with the defect or perforation being distal to the intact triangular fibrocartilage and exiting into the floor of the extensor carpi ulnaris sheath. We present 2 cases that illustrate the diagnosis, the use of both magnetic resonance imaging and arthrography to confirm the diagnosis, the associated dorsal ulnar cutaneous nerve pain distribution, and the open direct and retinacular flap repair.