Wrist anatomy and biomechanics

Bilateral greater arc Perilunate injury: A case report

INTRODUCTION

Perilunate injuries are rare and are frequently missed during initial examinations. These injuries are missed upon primary evaluation in approximately 25 % of cases, which can result in catastrophic outcomes. Early diagnosis is essential to avoid chronic wrist pain and limited range of motion.

IMPORTANCE

We reported rare finding & our approach in management which represents a significant contribution to the field and we believe it would be of great interest to your readers.

CASE PRESENTATION

We report the case of a 25-year-old man who presented with a bilateral Perilunate fracture-dislocation injury. He underwent bilateral definitive open reduction using a dorsal approach. Headless screws were used for the internal fixation of the bilateral scaphoids, and Kirschner wires were used to secure the left distal radius and for bilateral intercarpal fixation. Aggressive physiotherapy was initiated 8 weeks after the open reduction. After 1 year, the patient showed a satisfactory outcome with an excellent bilateral Mayo wrist score.

CLINICAL DISCUSSION

Perilunate dislocations and fracture-dislocations are considered orthopedic emergencies with close reduction being the initial treatment of choice. Early diagnosis and treatment of such injuries are essential to achieve optimal outcomes, which may be achieved with open reduction and internal fixation through a combined volar and dorsal approach.

CONCLUSION

Perilunate injuries should be considered as one of the differential diagnoses in wrist injuries. All Perilunate injuries should undergo emergency close reduction, typically followed by open reduction and reconstruction.

A self-managed exercise therapy program for wrist osteoarthritis: study protocol for a randomized controlled trial

BACKGROUND

Post-traumatic wrist osteoarthritis (OA) can eventually lead to pain, muscular weakness, and stiffness of the wrist, which can affect the function of the entire upper limb and reduce the quality of life. Although there is strong evidence that all patients with OA should be offered adequate education and exercises as a first-line treatment, an effective self-management program, including structured education and therapeutic exercises, has not yet been introduced for individuals with wrist OA. This trial aims to evaluate the effectiveness of an exercise therapy program with joint protective strategies to improve neuromuscular control (intervention group) compared to a training program with range of motion exercises (control group).

METHODS

This is a single-blinded randomized controlled trial (RCT) with two treatment arms in patients with symptomatic and radiographically confirmed wrist OA. The trial will be conducted at a hand surgery department. The participants will be randomly assigned either to a neuromuscular exercise therapy program or to a training program with range of motion exercises only. Participants in both groups will receive a wrist orthosis and structured education on wrist anatomy, pathophysiology, and joint protective self-management strategies. The programs consist of home exercises that will be performed twice a day for 12 weeks. The Patient-Rated Wrist Evaluation (PRWE) is the primary outcome measure of pain and function. Wrist range of motion (ROM), grip strength, the Numeric Pain Rating scale (NPRS), Disabilities of the Arm, Shoulder, and Hand (DASH), the General Self-Efficacy Scale (GSES), Global Rating of Change (GROC), and conversion to surgery are the secondary measures of outcome. Assessments will be performed at baseline and at 3, 6, and 12 months after baseline by a blinded assessor.

DISCUSSION

The upcoming results from this trial may add new knowledge about the effectiveness of a self-managed exercise therapy program on pain and function for individuals with wrist OA. If the present self-management program proves to be effective, it can redefine current treatment strategies and may be implemented in wrist OA treatment protocols.

TRIAL REGISTRATION

ClinicalTrials.gov, NCT05367817. Retrospectively registered on 27 April 2022. https://clinicaltrials.gov .

Load Distribution in Dorsally-Angulated Distal Radius Deformity Using Finite Element Analysis

PURPOSE

The load axis of the carpals is located on the volar side of the normal distal radius. A volar lunate facet fracture (VLFF) is exposed to volar-shearing stress, which can cause volar displacement of the carpus. A previous biomechanical study reported that the load at the scaphoid fossa was located more dorsally and the pressure at the lunate fossa decreased in a dorsally-angulated model. However, the distal radius load distribution for various volar tilts remains unclear. We speculate that if the volar tilt decreases, the load distribution moves dorsally and decreases the stress on the VLFF. Therefore, we analyzed a dorsally-angulated distal radius model to evaluate changes in the load distribution using finite element analysis.

METHODS

A 3-dimensional finite element wrist model was developed using computed tomography images. The ligaments were modeled as tension-only spring elements. We considered the intact wrist model for a volar tilt of 15° and created 5 additional models for volar tilts of 10°, 5°, 0°, -5°, and -10°.

RESULTS

As the dorsal angulation increased, the stress distribution moved from volar to dorsal and from the lunate fossa toward the scaphoid fossa. The maximum stress on the volar lunate facet was reduced as volar tilt decreased. The maximum stress was higher on the lunate fossa for volar tilts from 15° to 5°. In contrast, the maximum stress was higher on the scaphoid fossa for volar tilts of ≤0°.

CONCLUSIONS

Load transmission moved from volar to dorsal and from the lunate fossa to the scaphoid fossa when the volar tilt decreased. Therefore, a decrease in the volar tilt would reduce the load on the VLFF.

CLINICAL RELEVANCE

This study provides surgeons accurate knowledge regarding load distribution of the distal radius for various volar tilts that could be helpful in treating patients with VLFFs.

Management of giant cell tumors of the distal radius

Background

The distal radius is the most common location for giant cell tumors (GCT) in the upper extremity. Treatment should balance the goals of maximizing function and minimizing recurrence and other complications. Given the complexity in surgical treatment, various techniques have been described without clear standards of treatment.

Objectives

The purpose of this review is to provide an overview of evaluation of patients presenting with GCT of the distal radius, discuss management, and provide an updated summary on outcomes of treatment options.

Conclusion

Surgical treatment should consider tumor Grade, involvement of the articular surface, and patient-specific factors. Options include intralesional curettage and en bloc resection with reconstruction. Within reconstruction techniques, radiocarpal joint preserving and sparing procedures can be considered. Campanacci Grade 1 tumors can be successfully treated with joint preserving procedures, whereas for Campanacci Grade 3 tumors consideration should be given to joint resection to prevent recurrence. Treatment of Campanacci Grade 2 tumors is debated in the literature. Intralesional curettage and adjuvants can successfully treat cases where the articular surface can be preserved, while en-bloc resection should be used in cases where the articular surface cannot undergo aggressive curettage. A variety of reconstructive techniques are used for cases needing resection, with no clear gold standard. Joint sparing procedures preserve motion at the wrist joint, whereas joint sacrificing procedures preserve grip strength. Choice of reconstructive procedure should be made based on patient-specific factors, considering relative functional outcomes, complications, and recurrence rates.

Pathomechanism of Triangular Fibrocartilage Complex Injuries in Patients with Distal-Radius Fractures: A Magnetic-Resonance Imaging Study

Injury to the triangular fibrocartilage complex (TFCC) is one of the most common complications following a fracture of the distal radius. In this study, an examination of TFCC injuries in patients with distal-radius fractures was conducted using magnetic-resonance imaging (MRI); the aim of the study was to analyze the prevalence of TFCC injury as well as to suggest acceptable radiologic parameters for use in prediction of the injury pattern. Fifty-eight patients with distal-radius fractures who underwent MRI prior to undergoing open-reduction surgery between April 2020 and July 2021 were included in this study. An analysis of various radiologic parameters, the fracture type, and the MRI classification of TFCC injuries was performed. Radiologic parameters were used in the evaluation of distal radioulnar joint (DRUJ), radial shortening, and the dorsal angularity of the fracture. All of the patients in this study had definite traumatic TFCC injuries. A statistical relationship was observed between the radial length gap between the intact wrist and the injured wrist, which represents relative radial shortening, and the pattern of TFCC injury. In conclusion, the shortening of the distal radius, causing peripheral soft tissue of the ulnar side to become tauter, is highly relevant with regard to the pattern of TFCC injury. However, because no data on the clinical outcome were utilized in this study, it is lacking in clinical perspective. The conduct of further studies on patients’ clinical outcome will be necessary.

Perilunate Dislocations: Current Treatment Options

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Approximately 25% of all patients who sustain perilunate dislocations present in a delayed fashion.

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While management of acute injuries is relatively well-described, treatment of chronic injuries can be complex and there is a paucity of scientific evidence to guide management.

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Treatment options include open reduction internal fixation, proximal row carpectomy, scaphoid or lunate excision with or without arthrodesis, and total wrist arthrodesis, although indications vary based on chronicity of injury and patient factors.

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The purpose of this article was to determine the quality of evidence supporting surgical options for the treatment of these injuries.

Anatomy and Biomechanics of the Thumb Carpometacarpal Joint

This review discusses the anatomy and biomechanics of the thumb carpometacarpal (CMC) joint. This articulation between the trapezium and first metacarpal is integral for opposition and other complex movements necessary for pinch and grasp maneuvers. Fortunately, this joint is well equipped to handle the extreme forces imposed by these movements, as it is stabilized by an elaborate arrangement of ligaments and muscles. Without this stability, thumb subluxation would occur with loading during pinch and grasp, and human prehension would be impossible. Understanding the interactions occurring within this joint is essential for adequately treating pathology arising in this crucial joint.

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.

How Close Are the Volar Wrist Ligaments to the Distal Edge of the Pronator Quadratus? An Anatomical Study

Background: This cadaveric study defines the interval distance between the proximal insertion of the volar wrist ligaments and the distal edge of the pronator quadratus on the distal radius. It is important to be aware of this distance during surgical dissection for placement of volar locking plates for wrist fractures. Disruption of the volar wrist ligament insertion may have adverse biomechanical consequences such as carpal instability, which can lead to pain and eventually wrist arthritis. Methods: Thirteen cadaveric wrists were dissected using the trans-flexor carpi radialis volar approach to identify relevant anatomy. The distance between the distal border of the pronator quadratus and the most proximal insertion of the volar wrist ligaments was measured. Results: The average distance between the pronator quadratus and the proximal insertion of the volar wrist ligaments was 5 mm, with a standard deviation of 2 mm. Conclusions: The volar wrist ligaments insert quite near the distal end of the pronator quadratus. Surgeons should be cognizant of the proximity of the volar wrist ligaments and be judicious with subperiosteal stripping of the distal fragment during volar plating procedures.

The influence of fracture location and comminution on acute scaphoid fracture displacement: three-dimensional CT analysis

We aimed to assess the influence of fracture location and comminution on acute scaphoid fracture displacement using three-dimensional CT. CT scans of 51 adults with an acute scaphoid fracture were included. Three-dimensional CT was used to assess fracture location, comminution and displacement. Fracture location was expressed as the height of the cortical breach on the volar and dorsal side of the scaphoid relative to total scaphoid length (%), corresponding to the fracture's entry and exit point, respectively. We found a near-linear relation between dorsal fracture location and displacement. As dorsal fracture location became more distal, translation (ulnar, proximal, volar) and angulation (flexion, pronation) of the distal fragment relative to the proximal fragment increased. Comminuted fractures had more displacement. Dorsal fracture location predictably dictates the direction of translation and angulation in displaced scaphoid fractures. Surgeon attention to dorsal fracture location can help identify displacement patterns and provide guidance in adequately reducing a displaced scaphoid fracture.Level of evidence: III.

Predictors of joint damage in patients with rheumatoid arthritis: focus on short- and long-term effects of intra-articular glucocorticoid injections

BACKGROUND/AIMS

To investigate the short- and long-term efficacy of intra-articular glucocorticoid injections (IAGI) in patients with rheumatoid arthritis (RA).

METHODS

This was a retrospective study of RA patients who had active arthritis in the hand or wrist joints and who received IAGI (or not) as an adjunct to disease-modifying antirheumatic drugs (DMARDs). Short-term efficacy was assessed based on changes in the disease activity score in 28 joints (DAS28) after 3 months and long-term efficacy was assessed based on changes in the van der Heijde Sharp score (HSS) of hand radiographs over 2 years. Radiographic progression was defined as ΔHSS/year ≥ 2. Logistic regression analysis identified predictors of early achievement of low disease activity (LDA) and radiographic progression.

RESULTS

Overall, 126 RA patients received IAGI into the hand or wrist joints and 107 were IAGI-naive. After 3 months, 67% of IAGI-treated patients and 48% of IAGI-naive patients achieved LDA (p = 0.002). Over the next 2 years, 35% of patients treated with IAGI showed radiographic progression compared with 27% of IAGI-naive patients (p = 0.2). IAGI plus biologic DMARDs was associated with achievement of LDA in 3 months. Achieving LDA in 3 months (odds ratio [OR], 0.403; 95% confidence interval [CI], 0.192 to 0.847), wrist arthritis (OR, 2.408; 95% CI, 1.184 to 4.897), and baseline HSS (OR, 1.021; 95% CI, 1.003 to 1.039) were associated with radiographic progression.

CONCLUSION

IAGI was associated with early achievement of LDA. LDA was associated with slower radiographic progression. The wrist is more vulnerable to joint damage and requires more aggressive treatment.

Cortical and trabecular bone structure of the hominoid capitate

Morphological variation in the hominoid capitate has been linked to differences in habitual locomotor activity due to its importance in movement and load transfer at the midcarpal joint proximally and carpometacarpal joints distally. Although the shape of bones and their articulations are linked to joint mobility, the internal structure of bones has been shown experimentally to reflect, at least in part, the loading direction and magnitude experienced by the bone. To date, it is uncertain whether locomotor differences among hominoids are reflected in the bone microarchitecture of the capitate. Here, we apply a whole‐bone methodology to quantify the cortical and trabecular architecture (separately and combined) of the capitate across bipedal (modern Homo sapiens), knuckle‐walking (Pan paniscus, Pan troglodytes, Gorilla sp.), and suspensory (Pongo sp.) hominoids (n = 69). It is hypothesized that variation in bone microarchitecture will differentiate these locomotor groups, reflecting differences in habitual postures and presumed loading force and direction. Additionally, it is hypothesized that trabecular and cortical architecture in the proximal and distal regions, as a result of being part of mechanically divergent joints proximally and distally, will differ across these portions of the capitate. Results indicate that the capitate of knuckle‐walking and suspensory hominoids is differentiated from bipedal Homo primarily by significantly thicker distal cortical bone. Knuckle‐walking taxa are further differentiated from suspensory and bipedal taxa by more isotropic trabeculae in the proximal capitate. An allometric analysis indicates that size is not a significant determinate of bone variation across hominoids, although sexual dimorphism may influence some parameters within Gorilla. Results suggest that internal trabecular and cortical bone is subjected to different forces and functional adaptation responses across the capitate (and possibly other short bones). Additionally, while separating trabecular and cortical bone is normal protocol of current whole‐bone methodologies, this study shows that when applied to carpals, removing or studying the cortical bone separately potentially obfuscates functionally relevant signals in bone structure.

3T Magnetic Resonance Imaging of the Wrist Tendons

Magnetic resonance imaging (MRI) is frequently used in the imaging evaluation of wrist pain. The complex anatomy of the wrist can be demonstrated by MRI. Three tesla (3 T) MRI offers increased signal-to-noise ratio relative to 1.5 T MRI allowing for higher soft tissue contrast and better spatial resolution. The resulting increase in conspicuity of fine anatomic detail may improve the detection and characterization of wrist pathology. In this article, we will review the anatomy, normal variants, and common pathologies of the wrist tendons as evaluated on 3 T MRI.

A Study on the Incidence of Hand or Wrist Injuries in CrossFit Athletes

Purpose

The purpose of this study was to investigate the reported rates and characteristics of injuries among CrossFit athletes with specific attention to the hand and wrist. We further sought to identify trends and associations of these injuries by examining demographic data.

Methods

A questionnaire was created to capture self-reported information on the incidence of hand or wrist injuries and their associations in CrossFit athletes. It was distributed between April 2020 and July 2020 to athletes training at CrossFit affiliated gyms in the New York and Pennsylvania regions. Bivariate logistic regression analysis was used to identify factors correlated with an injury.

Results

A total of 270 responses (97.5% response rate) were available for final analysis. The median age of respondents was 34 years and 72.2% had been participating in CrossFit for at least two years. CrossFit athletes reported injury rates of 62.2% while engaged in CrossFit training and 20.4% reported an injury specific to the hand or wrist. The majority of hand or wrist injuries occurred after one year of CrossFit training (65.4%). The majority of reported initial injuries occurred to the wrist (75.4%); subsequently, 29.1% reported reinjuring the same region. While 58.2% reported not yet having healed or taking longer than one month to feel fully healed, 72.8% reported returning to unmodified training within one month. Only 15 respondents reported seeking medical attention from a physician for their injury. Physicians generally recommended a training break of over one month, but only two patients reported taking a break this long. Male sex and length of participation in CrossFit were associated with an increased risk of developing a hand or wrist injury.

Discussion

Hand and wrist injuries represent a significant proportion of injuries among CrossFit athletes. CrossFit practitioners are potentially returning to unmodified training too early following injury, leaving them susceptible to further injury. Physicians and therapists must consider these findings and address both therapies and preventative measures for these types of injuries with their patients.

Mechanical performance comparison of two surgical constructs for wrist four-corner arthrodesis via dorsal and radial approaches

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.

3D mapping of scaphoid fractures and comminution

OBJECTIVE

Acute and subacute scaphoid fractures were assessed using 3D computer tomography (CT). The aims were to describe fracture morphology, to map fractures onto a 3D scaphoid model and to correlate this to scaphoid anatomy.

MATERIALS AND METHODS

A retrospective, multicentre database search was performed to identify CT studies of acute and subacute scaphoid fractures. CT scans of scaphoid fractures less than 6 weeks from time of injury were included in this retrospective, multicentre study. CTs were segmented and converted into three-dimensional models. Following virtual fracture reduction, fractures were mapped onto a three-dimensional scaphoid model.

RESULTS

Seventy-five CT scans were included. The median delay from injury to CT was 29 days. Most studies were in male patients (89%). Most fractures were comminuted (52%) or displaced (64%). A total of 73% of displaced fractures had concomitant comminution. Waist fractures had higher rates of comminution and displacement when compared with all other fractures. Comminution was located along the dorsal ridge and the volar scaphoid waist.

CONCLUSION

Our study is the first to describe acute fracture morphology using 3D CT and to correlate comminution and displacement to fracture types. The dorsal ridge and volar waist need prudent assessment, especially in waist fractures.

Imaging of Carpal Instabilities

Background The term “carpal instability” describes different debilitating wrist conditions, in which the carpus is unable to maintain its physiological range of motion and load transfer. Depending on the cause and location of the dysfunction, four groups can be defined: dissociative, non-dissociative, complex, and adaptive carpal instability. As the most common form by far, dissociative carpal instability can further be categorized as dorsal or palmar intercalated segment instability, contingent on the afflicted interosseous ligament.

Method This review article outlines the different entities of carpal instability, their pathophysiology, and their clinical presentation. It further discusses the diagnostic significance of different imaging methods as well as the established treatment options for each form of instability in context with the current literature.

Results and Conclusion Early detection and treatment of carpal instability are essential for preventing carpal osteoarthritis. Traumatic lesions of the scapholunate interosseous ligament are the most frequent cause of instability. They can occur in an isolated fashion or in context with other carpal injuries. While stress imaging and fluoroscopy facilitate the differentiation between dynamic and static forms of carpal instability, only MRI and CT/MR arthrography can directly reveal the extent of ligament discontinuity.

Key Points:

Citation Format

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.

Design of Shape Memory Alloy-Based Soft Wearable Robot for Assisting Wrist Motion

In this paper, we propose a shape memory alloy (SMA)-based wearable robot that assists the wrist motion for patients who have difficulties in manipulating the lower arm. Since SMA shows high contraction strain when it is designed as a form of coil spring shape, the proposed muscle-like actuator was designed after optimizing the spring parameters. The fabricated actuator shows a maximum force of 10 N and a maximum contraction ratio of 40%. The SMA-based wearable robot, named soft wrist assist (SWA), assists 2 degrees of freedom (DOF) wrist motions. In addition, the robot is totally flexible and weighs 151g for the wearable parts. A maximum torque of 1.32 Nm was measured for wrist flexion, and a torque of larger than 0.5 Nm was measured for the other motions. The robot showed the average range of motion (ROM) with 33.8, 30.4, 15.4, and 21.4 degrees for flexion, extension, ulnar, and radial deviation, respectively. Thanks to the soft feature of the SWA, time cost for wearing the device is shorter than 2 min as was also the case for patients when putting it on by themselves. From the experimental results, the SWA is expected to support wrist motion for diverse activities of daily living (ADL) routinely for patients.

Therapeutic interventions for osteoarthritis of the wrist: a systematic review and meta-analysis

Background: In order to evaluate the effectiveness of interventions for osteoarthritis of the wrist in adults we performed a systematic review and meta-analysis. Methods: The MEDLINE and EMBASE via OVID, CINAHL and SPORTDiscus via EBSCO databases were searched from inception to 25 th April  2018.All randomised controlled clinical trials (RCTs) and any prospective studies of adults with wrist osteoarthritis investigating any intervention with a comparator were included.  Data were extracted and checked for accuracy and completeness by pairs of reviewers. Primary outcomes were pain and function. Comparative treatment effects were analysed by random effects at all time points. Results: Three RCTs were identified for inclusion after screening and all had a high risk of bias. Two compared proximal row carpectomy (PRC) with four corner fusion (4CF) for post-traumatic osteoarthritis, while the other compared leather with commercial wrist splints in patients with chronic wrist pain, of which a small group had wrist osteoarthritis.  Conclusion: There is no prospective study comparing operative to non-operative treatment for wrist osteoarthritis, while there is a paucity of prospective studies assessing the effectiveness of both non-operative and operative interventions.  Further research is necessary in order to better define which patients benefit from which specific interventions. Registration: The review protocol was registered with PROSPERO under the registration number CRD42018094799.

Therapeutic interventions for osteoarthritis of the wrist: a systematic review and meta-analysis

Background: In order to evaluate the effectiveness of interventions for osteoarthritis of the wrist in adults we performed a systematic review and meta-analysis. Methods: The MEDLINE and EMBASE via OVID, CINAHL and SPORTDiscus via EBSCO databases were searched from inception to 25 th April  2018.All randomised controlled clinical trials (RCTs) and any prospective studies of adults with wrist osteoarthritis investigating any intervention with a comparator were included.  Data were extracted and checked for accuracy and completeness by pairs of reviewers. Primary outcomes were pain and function. Comparative treatment effects were analysed by random effects at all time points. Results: Three RCTs were identified for inclusion after screening and all had a high risk of bias. Two compared proximal row carpectomy (PRC) with four corner fusion (4CF) for post-traumatic osteoarthritis, while the other compared leather with commercial wrist splints in patients with chronic wrist pain, of which a small group had wrist osteoarthritis.  Conclusion: There is no prospective study comparing operative to non-operative treatment for wrist osteoarthritis, while there is a paucity of prospective studies assessing the effectiveness of both non-operative and operative interventions.  Further research is necessary in order to better define which patients benefit from which specific interventions. Registration: The review protocol was registered with PROSPERO under the registration number CRD42018094799.

Analysis of tenodesis techniques for treatment of scapholunate instability using the finite element method

Chronic scapholunate ligament (SL) injury is a common disorder affecting the wrist. Despite advances in surgical techniques used to treat this injury, SL gap re-emergence may occur postoperatively. This paper presents an investigation into the performance of the Corella, schapolunate axis (SLAM), and modified Brunelli tenodesis (MBT) surgical reconstruction techniques used to treat scapholunate instability. Finite element (FE) models were used to undertake virtual surgery, and the resulting scapholunate (SL) gap and angle obtained using the 3 techniques were compared. The Corella technique was found to achieve the SL gap and angle closest to the intact (ligament) wrist, restoring SL gap and angle to within 5.6% and 0.6%, respectively. The MBT method resulted in an SL gap least close to the intact. The results of our study indicate that the contribution of volar scapholunate interosseous ligament to scapholunate stability could be important.

Evaluation of the performance of three tenodesis techniques for the treatment of scapholunate instability: flexion-extension and radial-ulnar deviation

Chronic scapholunate ligament (SL) injuries are difficult to treat and can lead to wrist dysfunction. Whilst several tendon reconstruction techniques have been employed in the management of SL instability, SL gap reappearance after surgery has been reported. Using a finite element model and cadaveric study data, we investigated the performance of the Corella, scapholunate axis (SLAM) and modified Brunelli tenodesis (MBT) techniques. Scapholunate dorsal and volar gap and angle were obtained following virtual surgery undertaken using each of the three reconstruction methods with the wrist positioned in flexion, extension, ulnar deviation and radial deviation, in addition to the ulnar-deviated clenched fist and neutral positions. From the study, it was found that, following simulated scapholunate interosseous ligament rupture, the Corella technique was better able to restore the SL gap and angle close to the intact ligament for all wrist positions investigated, followed by SLAM and MBT. The results suggest that for the tendon reconstruction techniques, the use of multiple junction points between scaphoid and lunate may be of benefit.

Graphical abstract

[Anatomy and biomechanics of the scaphoid]

The scaphoid is biomechanically and clinically of great importance for function of the wrist. In the literature, its anatomy and biomechanics are clearly underrepresented as well as underestimated. In the following review the scaphoid will be presented in more detail, according to recent information and findings. Not only will the origin of the name and the history of previous names, such as cotyloid or navicular, be introduced, but also for the first time in medical literature the significant phylogeny and ontogeny of the scaphoid will be shown. Moreover, the clinically very important blood supply, the ligaments of the scaphoid and relevant biomechanical details will be described.

Evaluation of midcarpal capitate contact mechanics in normal, injured and post-operative wrists

BACKGROUND

Scapholunate ligament injury is a commonly occurring carpal ligament injury. Pathology associated with scapholunate ligament injury depends on several factors such as the time after injury, type of injury (instability) and the development of osteoarthritis. The aim of this study was to investigate and compare contact mechanics in the lunocapitate and scaphocapitate joints in the normal, injured (scapholunate dissociation) and repaired (postoperative) wrist.

METHODS

Four human subjects with scapholunate ligament dissociation participated in this study. MR images of normal (contralateral), injured and postoperative wrists were obtained during relaxed condition and during active light grasp. Relaxed MR images were used to construct model geometry (bones with cartilage) for the capitate, lunate and scaphoid. Kinematic transformations were obtained by using image registration between the unloaded and functionally loaded image sets. Joint surface contact mechanics were then calculated.

FINDINGS

All contact measures (contact force, pressure, mean pressure and area) tended to increase with injury in both articulations. A significantly higher contact area was found in the injured scaphocapitate joint compared to normal. A significant increase in peak pressure was observed in the postoperative state compared to normal.

INTERPRETATION

Injury to the scapholunate ligament increased contact measures, suggesting a risk for onset of osteoarthritis in both the scaphocapitate and lunocapitate joints. Surgical repair appeared to restore most measures of contact mechanics to near normal values, more so for the lunocapitate joint when compared to scaphocapitate joint. The elevated postoperative peak pressures indicate the difficulty to fully restore joint mechanics.

Effect of Low-Level Laser Therapy and Strength Training Protocol on Hand Grip by Dynamometry

Introduction: The purpose of this study was to investigate the effect of low-level laser therapy (LLLT) - 660 nm and 904 nm - before grip strength protocol in healthy subjects. Methods: The study included 45 healthy volunteers with an average age of 22.7 (±1.4) years, subdivided into the following groups, control group: grip strength training associated with placebo LLLT; 660 nm group: LLLT (660 nm, 20 J/cm², power of 30 mW, and beam area of 0.06 cm², continuous, energy 1.2 J, and exposure time 40 seconds per point) before grip strength training and 904 nm group: LLLT (904 nm, 10 J/cm², peak power of 70 W and 0.13 cm² beam area, with pulsed beam 9.500 Hz and 30 seconds of exposure time per point and emitted energy 1.2 J) before grip strength training. The LLLT was timed to contact 10 points located in the region of the superficial and deep flexor muscles of the fingers, with a total energy of 12.0 J per session. For the strength training protocol, the volunteer exercised their fingers with the dominant hand on a small table, elbow flexed at 90°, forearm in neutral, using a light extension handle. The Oxford protocol was performed during four weeks. The grip strength was assessed using a dynamometer (Jamar™). The data were evaluated by the analysis of variance (ANOVA) statistical method. Results: In the comparison of intragroup evaluation, only the 904 nm group showed a difference compared to the baseline assessment after 4 weeks (P < 0.05), in the final intergroup evaluation, a difference was observed in the comparison between the control and 904 nm groups Conclusion: In conclusion, LLLT (904 nm) applied before resistance training was effective in gaining grip strength when compared to LLLT (660 nm) and isolated strength training after 4 weeks.

Development of a biomechanical model of the wrist joint for patient-specific model guided surgical therapy planning: Part 1

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.

Microstructural study of the lunate in stage III Kienböck's disease with micro-computed tomography imaging

Seventeen fresh lunates with stage III Kienböck's disease were scanned with micro-computed tomography. Four regions of interest were selected to measure trabecular parameters, which were compared with those from normal lunates. Within the three regions in the distal surface, there was more compact trabecular bone in the middle region when compared with the palmar and dorsal regions. In the central part, the trabeculae of the Kienböck's lunates were much thicker than those in normal lunates. The diameters of the palmar nutrient foramina of the Kienböck's lunates were significantly smaller than those in normal lunates. In affected lunates, the bony disruptions were mostly located in the palmar or dorsal areas, which were shown from trabecular bone structure analysis to be structurally weaker. This leads to separation of the distal part of the fractured bone, disruption of the blood supply, poor bone remodelling and proneness to secondary fracture and eventual collapse.

Carpal Kinematics and Kinetics

The complex interaction of the carpal bones, their intrinsic and extrinsic ligaments, and the forces in the normal wrist continue to be studied. Factors that influence kinematics, such as carpal bone morphology and clinical laxity, continue to be identified. As imaging technology improves, so does our ability to better understand and identify these factors. In this review, we describe advances in our understanding of carpal kinematics and kinetics. We use scapholunate ligament tears as an example of the disconnect that exists between our knowledge of carpal instability and limitations in current reconstruction techniques.

Analysis of wrist bone motion before and after SL-ligament resection

The analysis of the three-dimensional motion of wrist joint components in the physiological and injured wrist is of high clinical interest. Therefore, the purpose of this in vitro study was to compare the motion of scaphoid, lunate and triquetrum during physiological wrist motion in flexion and extension, and in radial- and ulnar-deviation, with those motion patterns after complete resection of the scapho-lunate-ligament. Eight fresh frozen cadaver wrists were carefully thawed and prepared for the investigation with an electromagnetic tracking system by implantation of measurement coils with 6 degrees of freedom. Electromagnetic tracking enabled the motion analysis of the scaphoid, lunate, and triquetrum bones with respect to the fixed radius in three planes of passive motion. After scapho-lunate-ligament injury changes in the translational and rotational motion pattern especially of the scaphoid bone occurred in dorsal-volar directions during flexion and extension, radial- and ulnar-deviation, and during rotation around the radio-ulnar- and longitudinal-axis of the wrist.

The Functional Anatomy of the Carpometacarpal Complex in Anthropoids and Its Implications for the Evolution of the Hominoid Hand

Previously, we described several features of the carpometacarpal joints in extant large-bodied apes that are likely adaptations to the functional demands of vertical climbing and suspension. We observed that all hominids, including modern humans and the 4.4-million-year-old hominid Ardipithecus ramidus, lacked these features. Here, we assess the uniqueness of these features in a large sample of monkey, ape, and human hands. These new data provide additional insights into the functional adaptations and evolution of the anthropoid hand. Our survey highlights a series of anatomical adaptations that restrict motion between the second and third metacarpals (MC2 and MC3) and their associated carpals in extant apes, achieved via joint reorganization and novel energy dissipation mechanisms. Their hamate-MC4 and -MC5 joint surface morphologies suggest limited mobility, at least in Pan. Gibbons and spider monkeys have several characters (angled MC3, complex capitate-MC3 joint topography, variably present capitate-MC3 ligaments) that suggest functional convergence in response to suspensory locomotion. Baboons have carpometacarpal morphology suggesting flexion/extension at these joints beyond that observed in most other Old World monkeys, probably as an energy dissipating mechanism minimizing collision forces during terrestrial locomotion. All hominids lack these specializations of the extant great apes, suggesting that vertical climbing was never a central feature of our ancestral locomotor repertoire. Furthermore, the reinforced carpometacarpus of vertically climbing African apes was likely appropriated for knuckle-walking in concert with other novel potential energy dissipating mechanisms. The most parsimonious explanation of the structural similarity of these carpometacarpal specializations in great apes is that they evolved independently.

A biomechanical model of the wrist joint for patient-specific model guided surgical therapy: Part 2

An enhanced musculoskeletal biomechanical model of the wrist joint is presented in this article. The computational model is based on the multi-body simulation software AnyBody. Multi body dynamic musculoskeletal models capable of predicting muscle forces and joint contact pressures simultaneously would be valuable for studying clinical issues related to wrist joint degeneration and restoration. In this study, the simulation model of the wrist joint was used for investigating deeper the biomechanical function of the wrist joint. In representative physiological scenarios, the joint behavior and muscle forces were computed. Furthermore, the load transmission of the proximal wrist joint was investigated. The model was able to calculate the parameters of interest that are not easily obtainable experimentally, such as muscle forces and proximal wrist joint forces. In the case of muscle force investigation, the computational model was able to accurately predict the computational outcome for flexion and extension motion. In the case of force distribution of the proximal wrist joint, the model was able to predict accurately the computational outcome for an axial load of 140 N. The presented model and approach of using a multi-body simulation model 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. Therefore, patient-specific multi-body simulation models are potentially valuable tools for surgeons in pre- and intraoperative planning of implant placement and orientation.

De Quervain’s syndrome: It may not be an isolated pathology

Introduction

This paper details a retrospective review of patients’ records diagnosed with de Quervain’s syndrome following a traumatic event but no history of repetitive strain.

Methods

Data analysis of 41 patients was performed. The inclusion criteria were pain over first dorsal compartment, pain on resisted extensor pollicis brevis and/or abductor pollicis longus, and a positive Finkelstein’s test. The assessment included a subjective history to establish a repetitive activity or a traumatic incident and diagnostic tests to establish possible instability or osteoarthritis.

Results

There were 13 men and 28 women with an age range from 20 to 72 years. Statistical analysis was undertaken using Fisher’s Exact tests. 46.3% ( n = 19) of 41 patients had a ligament injury diagnosed after the de Quervain’s. 94.7% ( n = 18) of 19 patients with ligament instability had a history of trauma, and this was statistically significant. Clinically significant was that 82.9% ( n = 34) of 41 patients demonstrated extensor carpi ulnaris (ECU) muscle weakness, but there was no statistical significant correlation between ECU weakness and ligament instability. Patients could have ECU weakness without ligament instability; however, patients with ligament instability appeared more likely to have ECU weakness.

Conclusions

The results would suggest that de Quervain’s syndrome, in a proportion of patients, could be secondary to underlying wrist pathology due to previous trauma. If the patient does not report a true repetitive strain history, a more thorough assessment may need to be undertaken to establish if there is any underlying pathology.

A finite element analysis of two novel screw designs for scaphoid waist fractures

The scaphoid is the most often fractured carpal bone. Scaphoid fracture repair with a headless compression screw allows for early functional recovery. The rotational stability of a single screw may be limited, having a potential negative impact on the healing process. Two novel screws have been designed to provide improved rotational stability compared to the existing ones. Using a computational finite element model of a scaphoid osteotomy, we compared the efficacy of one simple screw and the two new screws in restricting inter-fragmentary motion (IFM) in three functional positions of the wrist and as a function of inter-fragmentary compression force. The in-plane IFM was primary rotational and was better restricted by the new screws compared to the conventional one when the inter-fragmentary compression force was below 15-20 N, but provided no clear benefit in total flexion independently of the compression force. To better understand the differences in the non-compressed case, we analyzed the acting moments and investigated the effects of the bending and torsional screw stiffness on IFM. By efficiently restricting the inter-fragmentary shear, the new screws may be clinically advantageous when the inter-fragmentary compression force is partially or completely lost and may provide further benefits toward earlier and better healing of transverse waist fractures of the scaphoid.

Anticipatory and Reactive Response to Falls: Muscle Synergy Activation of Forearm Muscles

We investigated the surface electromyogram response of six forearm muscles to falls onto the outstretched hand. The extensor carpi radialis longus, extensor carpi radialis brevis, extensor carpi ulnaris, abductor pollicis longus, flexor carpi radialis and flexor carpi ulnaris muscles were sampled from eight volunteers who underwent ten self-initiated falls. All muscles initiated prior to impact. Co-contraction is the most obvious surface electromyogram feature. The predominant response is in the radial deviators. The surface electromyogram timing we recorded would appear to be a complex anticipatory response to falling modified by the effect on the forearm muscles following impact. The mitigation of the force of impact is probably more importantly through shoulder abduction and extension and elbow flexion rather than action of the forearm muscles.

Pathomechanics of the wrist following fractures of the distal radius

Introduction

The wrist positions the hand in space and allows load transmission from the hand to the forearm. This research study aimed to explain the biomechanical changes that occur at the wrist following a fracture of the distal radius and to explore the effect of this fracture on wrist and hand range of motion and muscle strength. It was hypothesised that a fracture of the distal radius interferes with the biomechanical integrity of the wrist limiting the available wrist and hand range of motion. This in turn affects hand muscle strength.

Methods

This prospective research study adopted a quantitative quasi-experimental time-series design where 109 patients followed an occupational therapy programme for 12 weeks. Measurements of forearm, wrist and hand range of motion and hand muscle strength were taken on the initial assessment, and on the 6th and 12th weeks of intervention. A standard evaluation procedure was followed to ensure reliability of the results. Data were analysed using SPSS (PASW version 18).

Results

Forearm and wrist range of motion and muscle strength were significantly impaired. Hand range of motion was also affected even though the hand itself was not directly involved in the injury. Improvements in range of motion were accompanied by an increase in hand muscle strength. Patients with intra-articular fractures experienced greater limitations compared to their counterparts.

Conclusions

These results supported the initial hypothesis. Clinically, this highlights the need for orthopaedic management and rehabilitation to be based on a sound knowledge of the biomechanical interaction of the different structures involved.

[Isolated capitate fractures in the frontal plane]

Isolated fractures of the capitate in the frontal plane are both very rare and most of the time very discreet. There is a great risk to miss such fractures with potential longterm consequences. The following report of two independent patients highlights the importance of computed tomography in order to verify fractures and initiate adequate treatment.

In vivo length changes of wrist ligaments at full wrist extension

The aim of this study was to investigate the length changes of carpal ligaments when loaded in full extension in vivo. We obtained computed tomography scans of the right wrists in three positions for six volunteers: neutral; 75° extension; and 75° extension with a further 10° of radial deviation. Nine ligaments were measured and analysed with computer modelling. The results showed that the radioscaphocapitate, long radiolunate, and ulnolunate ligaments lengthened the most at full wrist extension, suggesting that they were under greatest load. The radioscapholunate, ulnocapitate, and ulnotriquetral ligaments lengthened further with the addition of wrist radial deviation. At full extension, the dorsal intercarpal ligament inserting on the scaphoid was lengthened. The dorsal radiocarpal and dorsal intercarpal ligaments inserting on the trapezoid were shortened, suggesting reduced loading. In conclusion, a number of volar carpal ligaments lengthened significantly in full wrist extension and the ulnar carpal ligaments were further lengthened at wrist radial deviation.

Skeletal anatomy of the hand

The skeletal anatomy of the hand is composed of phalanges, metacarpal bones, and carpal bones. Its function is a product of the complex interactions between the power provided by the intrinsic and extrinsic musculature, the stability provided by the ligaments, and the structure provided by the bones, which serve as insertion and attachment sites for the muscles and ligaments. This article provides a detailed description of the skeletal anatomy of the human hand.

Distal radius attachments of the radiocarpal ligaments: an anatomical study

Background Understanding the anatomy of the ligaments of the distal radius aids in the surgical repair of ligamentous injuries and the prediction of intraarticular fracture patterns. Purposes (1) to measure the horizontal and vertical distances of the origins of the radiocarpal ligaments from the most ulnar corner of the sigmoid notch and the joint line, respectively; and (2) to express them as a percentile of the total width of the bony distal radius. Methods We dissected 8 cadaveric specimens and identified the dorsal radiocarpal, radioscaphocapitate, and the long and short radiolunate ligaments. Results The dorsal radiocarpal ligament attached from the 16th to the 52nd percentile of the radial width. The radioscaphocapitate ligament attached around the radial styloid from the 86th percentile volarly to the 87th percentile dorsally. The long radiolunate ligament attached from the 59th to the 85th percentile, and the short radiolunate ligament attached from the 14th to the 41st percentile. Discussion There was a positive correlation between the radial width and the horizontal distance of the ligaments from the sigmoid notch. These findings may aid individualized surgical repair or reconstruction adjusted to patient size and enable further standardized research on distal radial fractures and their relationship with radiocarpal ligaments.

Scapholunate ligament injury adversely alters in vivo wrist joint mechanics: an MRI-based modeling study

We investigated the effects of scapholunate ligament injury on in vivo radiocarpal joint mechanics using image-based surface contact modeling. Magnetic resonance images of 10 injured and contralateral normal wrists were acquired at high resolution (hand relaxed) and during functional grasp. Three-dimensional surface models of the radioscaphoid and radiolunate articulations were constructed from the relaxed images, and image registration between the relaxed and grasp images provided kinematics. The displacement driven models were implemented in contact modeling software. Contact parameters were determined from interpenetration of interacting bodies and a linear contact rule. Peak and mean contact pressures, contact forces and contact areas were compared between the normal and injured wrists. Also measured were effective (direct) contact areas and intercentroid distances from the grasp images. Means of the model contact areas were within 10 mm(2) of the direct contact areas for both articulations. With injury, all contact parameters significantly increased in the radioscaphoid articulation, while only peak contact pressure and contact force significantly increased in the radiolunate articulation. Intercentroid distances also increased significantly with injury. This study provides novel in vivo contact mechanics data from scapholunate ligament injury and confirms detrimental alterations as a result of injury.

Effectiveness of surgical reconstruction to restore radiocarpal joint mechanics after scapholunate ligament injury: an in vivo modeling study

Disruption of the scapholunate ligament can cause a loss of normal scapholunate mechanics and eventually lead to osteoarthritis. Surgical reconstruction attempts to restore scapholunate relationship show improvement in functional outcomes, but postoperative effectiveness in restoring normal radiocarpal mechanics still remains a question. The objective of this study was to investigate the benefits of surgical repair by observing changes in contact mechanics on the cartilage surface before and after surgical treatment. Six patients with unilateral scapholunate dissociation were enrolled in the study, and displacement driven magnetic resonance image-based surface contact modeling was used to investigate normal, injured and postoperative radiocarpal mechanics. Model geometry was acquired from images of wrists taken in a relaxed position. Kinematics were acquired from image registration between the relaxed images, and images taken during functional loading. Results showed a trend for increase in radiocarpal contact parameters with injury. Peak and mean contact pressures significantly decreased after surgery in the radiolunate articulation and there were no significant differences between normal and postoperative wrists. Results indicated that surgical repair improves contact mechanics after injury and that contact mechanics can be surgically restored to be similar to normal. This study provides novel contact mechanics data on the effects of surgical repair after scapholunate ligament injury. With further work, it may be possible to more effectively differentiate between treatments and degenerative changes based on in vivo contact mechanics data.

High-resolution ultrasound of the extrinsic carpal ligaments

Thanks to its intrinsic high spatial resolution, ultrasound is an ideal imaging modality for examining very thin, superficial structures, and this makes it very helpful in the evaluation of extrinsic carpal ligaments. These structures, which arise from the radius and ulna and insert on the carpal bones, are extremely important for wrist stability. Previous studies have assessed the use of ultrasound to study the extrinsic carpal ligaments in cadavers, healthy asymptomatic subjects, and patients with rheumatoid arthritis. In the present report, we review the normal anatomy, biomechanics, and ultrasound appearance of these ligaments.

Immunohistochemical composition of the human lunotriquetral interosseous ligament

PURPOSE

The human lunotriquetral ligament (LTL) is a functionally important intrinsic hand ligament, which is assumedly subjected to insertion angle changes at the entheses during movement. To clarify whether the current model of the ligament's mechanical environment is reflected in its structural composition, we determined the regional distribution of extracellular matrix-related antigens.

METHODS

The extracellular matrix was immunohistochemically investigated in 12 LTLs from both wrists of 6 human donors (Mean age: 60 y).

RESULTS

The dorsal, proximal, and volar portions of the ligament immunolabeled for type I, III collagen and versican. Both entheses labeled strongly for type II collagen, aggrecan, and link protein and were distinctly cartilaginous. The ligament midsubstance was positive for collagen II in 30%, for aggrecan in 40%, and for keratocan and lumican in 100% of specimens. In contrast, keratocan and lumican were absent from the fibrocartilaginous entheses and the articular cartilage. Ligament insertion at a carpal bone occurs either directly through fibrocartilage or indirectly through a bilayered configuration of fibrocartilage and hyaline-like cartilage. The hyaline-like cartilage is continuous with the neighboring articular cartilage.

CONCLUSIONS

The LTL has an extracellular matrix comparable with that of ligaments experiencing a combination of tensile and shear/compressive load at the attachment sites. All regions of the LTL exhibit fibrocartilaginous entheses; purely fibrous attachment sites are rare. The ligament midsubstance shows a more fibrous phenotype than the entheses and expresses keratocan and lumican, which previously have not been recorded in any human hand ligament.