2007 IFSSH committee report of wrist biomechanics committee: biomechanics of the so-called dart-throwing motion of the wrist

Evaluation of a cadaveric wrist motion simulator using marker-based X-ray reconstruction of moving morphology

Surgical intervention is a common option for the treatment of wrist joint arthritis and traumatic wrist injury. Whether this surgery is arthrodesis or a motion preserving procedure such as arthroplasty, wrist joint biomechanics are inevitably altered. To evaluate effects of surgery on parameters such as range of motion, efficiency and carpal kinematics, repeatable and controlled motion of cadaveric specimens is required. This study describes the development of a device that enables cadaveric wrist motion to be simulated before and after motion preserving surgery in a highly controlled manner. The simulator achieves joint motion through the application of predetermined displacements to the five major tendons of the wrist, and records tendon forces. A pilot experiment using six wrists aimed to evaluate its accuracy and reproducibility. Biplanar X-ray videoradiography (BPVR) and X-Ray Reconstruction of Moving Morphology (XROMM) were used to measure overall wrist angles before and after total wrist arthroplasty. The simulator was able to produce flexion, extension, radioulnar deviation, dart thrower's motion and circumduction within previously reported functional ranges of motion. Pre- and post-surgical wrist angles did not significantly differ. Intra-specimen motion trials were repeatable; root mean square errors between individual trials and average wrist angle and tendon force profiles were below 1° and 2 N respectively. Inter-specimen variation was higher, likely due to anatomical variation and lack of wrist position feedback. In conclusion, combining repeatable intra-specimen cadaveric motion simulation with BPVR and XROMM can be used to determine potential effects of motion preserving surgeries on wrist range of motion and biomechanics.

Outcomes after radioscapholunate arthrodesis for intra-articular malunion of distal radius fractures

PURPOSE

To study the clinical, radiological, and functional outcomes after of radioscapholunate (RSL) fusion for intra-articular malunion of the distal radius.

METHODS

This retrospective study included 26 patients (17 males and 9 females) with intra-articular malunion of distal radius fractures who underwent RSL arthrodesis using locked miniplates (without distal scaphoid excision) between 2012 and 2020. Their mean age was 43 years (range, 32-56). Patients were assessed radiographically for union and clinically for range of motion, grip strength, and pain (assessed by Visual Analogue Scale (VAS) for pain). Functional evaluation was performed by using the Mayo modified wrist score (MMWS) and the Disabilities for the Arm, Shoulder, and Hand (DASH) questionnaire.

RESULTS

All patients showed complete healing at the fusion site after a mean of 8.7 weeks (range, 8-12). The mean follow-up period was 72 months (range, 60-84). The pinch strength improved from a mean of 6.2 kg (range, 3-12) to a mean of 9.8 kg (range, 5-18) which represents 80% of the contralateral side. The mean pinch strength was 7 kg (range, 5-18) which presents 80% of the other side. VAS for pain showed a mean improvement of 72.6%. The DASH score improved to a mean of 19.2 (range, 14-24). The MMWS improved to a mean of 68 (range, 45-86). At the final follow-up period, no degenerative changes were detected in the midcarpal joint.

CONCLUSION

RSL arthrodesis (using locked miniplates without distal scaphoid excision) is a reliable surgical procedure to manage cases of radiocarpal OA after intra-articular malunion of distal radius fractures with good clinical and radiological outcomes.

LEVEL OF EVIDENCE

Level IV- therapeutic.

Biomechanical requirements of meat cutting tasks: A pilot study quantifying tasks sustainability and assistance required at the wrist

The meat processing industry is particularly affected by distal upper limb musculoskeletal disorders. This pilot study aims at proposing a methodology able to quantify biomechanical requirements of meat cutting tasks at butchers' dominant wrist and, when necessary, at estimating the assistance needed to reach sustainability. Six professional butchers repeatedly cut pieces of pork. Joint angles were recorded using a motion capture system, cutting forces using an instrumented knife. Sustainability was computed by the maximal acceptable effort method. Assistance requirements were computed for isolated stressful exertions and for overall work cycle sustainability. Five butchers exceeded the sustainability threshold for wrist flexion. Ulnar or radial deviation torques were excessive for 2 and 3 of them, respectively. Extension torques were sustainable. The peak assistive torque for isolated exertions was at most 1.1Nm, 1.6Nm and 1.1Nm, and the percentage of assistance for overall sustainability was at most 60%, 56% and 56% for wrist flexion, ulnar and radial deviation, respectively.

Clinical measurement of functional dart thrower's motion in patients with unilateral wrist conditions undergoing nonoperative or postoperative hand therapy

STUDY DESIGN

Cross-sectional and descriptive study BACKGROUND: Functional dart thrower's motion (F-DTM) is an obliquely oriented wrist motion that occurs in activities such as throwing and drinking from a cup. There is limited data on clinical measurement of F-DTM.

PURPOSE OF THE STUDY

The purpose of this study was to 1) describe and establish reference scores for F-DTM measurement for nonoperative and postoperative wrist patients 2) compare F-DTM between the affected and nonaffected sides and 3) determine F-DTM score agreement across three consecutive trials.

METHODS

Two certified hand therapists evaluated F-DTM in consecutive adult patients with a unilateral wrist condition undergoing nonoperative or postoperative therapy. Three trials of goniometer measurements for radial extension (RE) and ulnar flexion (UF) were assessed on the nonaffected and affected wrists. A total arc F-DTM was computed. Mean, 95% confidence intervals (CI), and Cohen's d effect size described side-to-side differences in RE, UF, and total arc F-DTM. Agreement in scores across trials was assessed with an intraclass correlation coefficient (ICC).

RESULTS

Thirty-one nonoperative (mean ± SD age = 40.0 ± 13.9 years, 74% female, 94% right hand dominant) and 44 postoperative patients (mean ± SD age = 44.9 ± 14.9 years, 66% female, 84% right hand dominant) were enrolled. The average side-to-side difference, in degrees, in the nonoperative group was -6.4 (95% CI: -9.4 to -3.4, Cohen's d = 0.8) for RE, -10.4 (-16.7 to -4.0, d = 0.6) for UF, and -16.8 (-24.3 to -9.2, d = 0.8) for total arc F-DTM. The average side-to-side difference in the postoperative group was -33.6 (-38.8 to -28.3, d = 1.9) for RE, -34.7 (-40.6 to -28.7, d = 1.8) for UF, and -68.2 (-77.9 to -58.5, d = 2.1) for total arc F-DTM. The range of ICCs for F-DTM measurements was 0.82-0.96.

CONCLUSIONS

Goniometer measurement of F-DTM is a clinically feasible method to quantify functional motion loss in an injured wrist population, particularly patients with postoperatively managed wrist conditions.

Understanding the biomechanics of the forearm during the dart thrower's motion

This study investigated the contribution of different forearm muscles, namely the flexor carpi ulnaris, extensor carpi radialis longus and brevis, extensor carpi ulnaris and flexor carpi radialis, during the dart thrower's motion. Thirteen healthy participants were recruited. The forearm muscle activation patterns during the dart thrower's motion were measured using surface electromyography. The average root mean square for the extensor carpi ulnaris was found to be the highest during the dart thrower's motion. Muscle activations during the dart thrower's motion were heterogeneous among the participants. The results suggest the rehabilitation protocol for patients with wrist injuries should be reconsidered.

Wrist Arthritis and Arthrodesis: Preserving Function, Minimizing Problems

Wrist arthritis is a common condition with numerous causes and presentations. Several management options exist, and treatment should be individualized based on patient age, comorbidities, occupation, duration of symptoms, and failed treatment modalities. Arthroscopy and denervation are appealing because of shorter recovery time and preservation of motion, but duration of effectiveness varies between patients. Patients who fail these smaller procedures or those with pancarpal arthrosis are treated effectively with total wrist arthrodesis or total wrist arthroplasty in lower-demand patients. This article reviews causes and patterns of wrist arthritis and discusses treatment strategies aimed at preserving function and minimizing complications.

Coronal translation of the forearm, proximal capitate, and ulnar styloid predict radial inclination in distal radius fractures in older female patients

Aims

The aims of this study were to identify means to quantify coronal plane displacement associated with distal radius fractures (DRFs), and to understand their relationship to radial inclination (RI).

Methods

From posteroanterior digital radiographs of healed DRFs in 398 female patients aged 70 years or older, and 32 unfractured control wrists, the relationships of RI, quantifiably, to four linear measurements made perpendicular to reference distal radial shaft (DRS) and ulnar shaft (DUS) axes were analyzed: 1) DRS to radial aspect of ulnar head (DRS-U); 2) DUS to volar-ulnar corner of distal radius (DUS-R); 3) DRS to proximal capitate (DRS-PC); and 4) DRS to DUS (interaxis distance, IAD); and, qualitatively, to the distal ulnar fracture, and its intersection with the DUS axis.

Results

In the study (fracture) and control groups, respectively, the mean values were: RI, 17.2° (SD 7.2°; -7° to 35°) and 25.6° (SD 2.6°; 21° to 30°); DRS-U, 13.5 mm (SD 1.7; 4.9 to 20.8) and 15.3 mm (SD 0.72; 13.8 to 16.3); DUS-R, 13.4 mm (SD 2.1; 4.8 to 18.5) and 12.0 mm (SD 0.99; 9.7 to 13.9); DRS-PC (positive value radial to DRS, negative value ulnar), 0.14 mm (SD 5.4; -10.9 to 22.7) and -6.1 mm (SD 1.6; -10.6 to -2.3); and IAD, 25.3 mm (SD 2.5; 17.6 to 31.1) and 27.1 mm (SD 1.5; 24.5 to 31.0). All means were significantly different between the study and control groups. RI correlated strongly with DRS-PC. Ulnar styloid fracture intersection with the DUS axis, reflective of ulnar translation of both radial and ulnar shafts, was associated with significantly lower RI.

Conclusion

After DRF, the relationship of the proximal capitate to the DRS axis in the coronal plane correlates with the final radial inclination. Additionally, ulnar styloid intersection with the DUS axis is associated with even lower radial inclination. DRF reduction should seek to restore the normal coronal relationship of both radial and ulnar shafts to their distal counterparts.

A Musculoskeletal Model of the Hand and Wrist Capable of Simulating Functional Tasks

OBJECTIVE

The purpose of this work was to develop an open-source musculoskeletal model of the hand and wrist and to evaluate its performance during simulations of functional tasks.

METHODS

The current model was developed by adapting and expanding upon existing models. An optimal control theory framework that combines forward-dynamics simulations with a simulated-annealing optimization was used to simulate maximum grip and pinch force. Active and passive hand opening were simulated to evaluate coordinated kinematic hand movements.

RESULTS

The model's maximum grip force production matched experimental measures of grip force, force distribution amongst the digits, and displayed sensitivity to wrist flexion. Simulated lateral pinch strength replicated in vivo palmar pinch strength data. Additionally, predicted activations for 7 of 8 muscles fell within variability of EMG data during palmar pinch. The active and passive hand opening simulations predicted reasonable activations and demonstrated passive motion mimicking tenodesis, respectively.

CONCLUSION

This work advances simulation capabilities of hand and wrist models and provides a foundation for future work to build upon.

SIGNIFICANCE

This is the first open-source musculoskeletal model of the hand and wrist to be implemented during both functional kinetic and kinematic tasks. We provide a novel simulation framework to predict maximal grip and pinch force which can be used to evaluate how potential surgical and rehabilitation interventions influence these functional outcomes while requiring minimal experimental data.

Proximal row carpectomy generates better mid- to long-term outcomes than four-corner arthrodesis for post-traumatic wrist arthritis: A meta-analysis

INTRODUCTION

In posttraumatic wrist arthritis of intermediate severity, two main palliative procedures are used to preserve some mobility in the wrist: proximal row carpectomy (PRC) and scaphoid excision followed by four corner arthrodesis (4CA). Despite satisfactory overall results, the debate continues about which one provides the best results and long-term outcomes, particularly prevention of arthritis progression. Recent comparative studies now provide us with information about mid- and long-term results. The aim of this study was to compare the clinical results, complications, conversion rate to total wrist arthrodesis and progression to osteoarthritis of PRC versus 4CA in the medium and long term.

HYPOTHESIS

The null hypothesis was that there is no significant difference between PRC and 4CA in the clinical results, complications, conversion to total wrist arthrodesis and arthritis progression.

MATERIALS AND METHODS

A systematic literature review was carried out by following the PRISMA guidelines. Included were studies comparing 4CA and PRC for the treatment of post-traumatic wrist arthritis secondary to scapholunate dissociation (SLAC) and scaphoid nonunion (SNAC) with a mean follow-up of 5 years. A search was performed of the MEDLINE, EMBASE and Cochrane databases that identified 831 articles. After removing 230 duplicates and excluding 595 articles based on their title and/or abstract, and then adding 1 article manually, 7 articles were included in our analysis. Parameters analyzed were range of motion (ROM), pain, grip strength, functional scores, complications, conversion to total wrist arthrodesis, and arthritis progression.

RESULTS

In the 7 articles, 1059 wrists - 582 PRC and 477 4CA - were analyzed with follow-up ranging from 5.2 to 18 years. PRC produced significantly better ROM in flexion (weighted mean difference [WMD]=10.0°; p<0.01) and in ulnar deviation (WMD=8.7°; p<0.01) along with significantly lower complication rates (OR=0.3; p<0.01) and reoperation rates (OR=0.1; p<0.01). There was no significant difference in the conversion rate, grip strength, extension, radial deviation, pain, DASH and PRWE scores. The progression of osteoarthritis could not be analyzed due to lack of data.

DISCUSSION

This meta-analysis was the first to include recently published mid- and long-term studies comparing PRC and 4CA. The main finding is that PRC is superior overall with better ROM and a lower complication rate. Another important finding was the absence of differences in grip strength and the conversion rate to total wrist arthrodesis. Unfortunately, the lack of systematic studies on arthritis progression leaves this question unanswered. Our findings must be interpreted cautiously because it was impossible to stratify the cases by etiology and osteoarthritis stage.

LEVEL OF EVIDENCE

III; systematic review and meta-analysis.

Effect of Various Wrist and Forearm Motions on Distal Radius Forces

Background  Dart throw motions are frequently used during rehabilitation but the ideal orientation of a dart throw motion is unknown. Questions/Purposes  The purpose of this study was to measure the axial force on the distal radius during different dart throw motions with the wrist and forearm in various positions. Our hypothesis was that there would be a significant difference on the axial force between various forearm positions and different dart throw orientations. Methods  Eight fresh frozen cadaver wrists were moved through 10 different orientations of a dart throw motion with the forearm in neutral, in pronation, and during a dynamic forearm rotation motion while the axial force was measured. Results  Significantly smaller axial force occurred with the forearm in pronation than during the dynamic forearm motion. The shorter dart throw motions which were oriented equally toward the flexion/extension and radioulnar deviation axes had significantly smaller distal radius forces than nearly all of the other dart throw motions. Conclusion/Clinical Relevance  Rehabilitation protocols incorporating a dart throw motion may be of benefit after injury or surgery. To minimize the axial force transmitted through a healing distal radius fracture, short dart throw motions, oriented at 45 degrees from the sagittal and coronal planes, with the forearm in pronation, might be preferable for range of motion activities during rehabilitation.

Prosthetic and robotic wrists comparing with the intelligently evolved human wrist: A review

Both prosthetic and robotic research communities have tended to focus on hand/gripper development. However, the wrist unit could enable higher mobility of the end effector and thus more efficient and dexterous manipulation. The current state of the art in both prosthetic and robotic wrists is reviewed systematically, mainly concerning their kinematic structures and resultant capabilities. Further, by considering the biomechanical advantages of the human wrist, an evaluation including the mobility, stability, output capability, load capacity and flexibility of the current artificial wrists is conducted. With the pentagonal capability radar charts, the major limitations and challenges in the current development of artificial wrists are derived. This paper hence provides some useful insights for better robotic wrist design and development.

Grip strength, functional range and anthropometric dimensions, and indication on fulfilling occupations in the home and workplace: A cross-sectional study

Introduction

Little is known about the relationship between the types of grip strength, functional range, anthropometric measures, and function in the home and workplace. The study aimed to determine their relationships and explore their contributions to performing usual work duties and overall function in participants with and without hand and wrist injury.

Method

Forty-four participants were measured on Maximal Voluntary Isometric Grip Strength, Rapid Exchange Grip Contractions and Isometric Endurance, Forearm Length and Volumetry, and the Dart Thrower’s Motion (DTM) measure. They completed the Patient Rated Wrist and Hand Evaluation and the Disabilities of the Arm, Shoulder and Hand Work Module.

Results

The grip measures significantly correlated with Volumetry (r = 0.62–0.74) in participants with and without hand and wrist injury. The Isometric Endurance and DTM measure of the non-injured hand were found to be contributing factors for participants with hand and wrist injury when returning to usual work duties and overall function.

Conclusion

The non-injured hand function plays a role in the overall function for participants with hand and wrist injuries. Isometric Endurance and DTM measure could assist clinicians in determining suitable rehabilitation targets, resulting in a better function required for occupations in the home or workplace.

Post-arthrolysis rehabilitation in a patient with wrist stiffness secondary to distal radio-ulnar fracture: A case report

BACKGROUND

Arthrolysis is usually performed when stiffness has a disabling effect on quality of life and in cases where physiotherapy has not been effective. This report describes one patient with a chronic stiff wrist who underwent open arthrolysis. The purpose of this case report is to describe the rehabilitation following arthrolysis, in order to illustrate the effects of intensive physiotherapy for this patient.

CASE DESCRIPTION

A 54-year-old woman with chronic wrist stiffness secondary to a radio-ulnar fracture was described. The patient presented severe pain and unsatisfactory wrist range of motion and muscle strength almost 2 years after the traumatic event.

INTERVENTION

Post-arthrolysis rehabilitation was based on edema control, manual therapy, transcutaneous electrical nerve stimulation (TENS), static splinting and strengthening exercises. In addition, graded motor imagery and proprioceptive rehabilitation were included to address impaired motor control. Outcome measures of passive range of motion (PROM), active range of motion (AROM), grip and pinch strength, numeric rating scale (NRS), disability of the arm, shoulder and hand (DASH) and patient-rated wrist/hand evaluation (PRWHE) were recorded.

CONCLUSIONS

The outcomes of this case report suggest that arthrolysis combined with immediate and intensive physiotherapy were a suitable option for the treatment of post-traumatic wrist stiffness in this patient. The passive motion measured intraoperatively was maintained, while pain, functional active motion and strength were improved allowing for social reintegration.

Biomechanical Comparison of Dart-Throw Motions after Partial Wrist Fusions

Background  Multiple partial wrist fusions exist for the management of arthritic disease. Limited information is available on their effect on wrist range of motion in the dart-throwing direction of wrist motion, even though it is used in most activities of daily living. Purpose  The purpose of this study was to measure the retained motion for different orientations of dart-throwing motion for seven different partial wrist fusions and proximal row carpectomy (PRC). Methods  Eight fresh frozen right cadavers were tested with the wrist intact and followed simulated fusions. Fusions were performed using an external fixation technique and included scaphocapitate, scapholunate (SL), capitolunate, radiolunate, radioscapholunate, scaphotrapeziotrapezoid, 4 corner fusion, and PRC. Results  In the intact wrist, the average arc of wrist motion with the wrist oriented at 20 degrees away from the flexion-extension axis was significantly larger than at any other orientation of motion. All partial wrist fusions and the PRC had significantly smaller average dart-throw arc of motion compared with intact at an orientation 20 and 25 degrees away from flexion-extension. The SL fusion provided a significantly larger arc of motion than most of the other fusions at most orientations. Conclusion/Clinical Relevance  This study provides a comprehensive compilation of the range of motion in a functional plane, "the dart-throw motion," for limited wrist fusions and PRC. These data provide the clinician with important information that can be used to educate patients regarding expectations after surgery.

Home exercise in the dart-throwing motion plane after distal radius fractures: A pilot randomized controlled trial

INTRODUCTION

During daily functions, our wrist moves through an oblique plane, named the dart-throwing motion (DTM) plane. This plane is considered a more stable plane because the proximal carpal row remains relatively immobile. However, rehabilitation programs that incorporate exercising in the DTM plane have yet to be explored.

PURPOSE OF THE STUDY

The purpose of this study was to evaluate the rehabilitation outcomes after treatment in the DTM plane compared with outcomes after treatment in the sagittal plane after distal radius fracture.

STUDY DESIGN

This is a pilot randomized controlled trial.

METHODS

Subjects after open reduction internal fixation were assigned into a research group (N = 12; ages 48.7 ± 7.3) and a control group (N = 12; ages 50.8 ± 15). The control group activated the wrist in the sagittal plane, whereas the research group activated the wrist in the DTM plane. Range of motion, pain levels, functional hand motor skills tests, and satisfaction from self-training exercise were measured before and after a 12-session intervention.

RESULTS

The outcome measures were similar between the treatment groups. The research group reported significantly higher satisfaction rates than the control group on topics such as general satisfaction (research group: 3.4 ± 0.7, control group: 2. 5 ± 1.2, P = .030), motivation to exert oneself (research group: 2.8 ± 1.0, control group: 2.3 ± 1.2, P = .009), progressed function (research group: 3.4 ± 0.7, control group: 2.4 ± 1.1, P = .012), and self-training contribution to the daily function (research group: 3.4 ± 0.7, control group: 2.5 ± 1.2, P = .030).

DISCUSSION AND CONCLUSION

Pilot results do not favor one treatment method over the other. However, exercising in the DTM plane may contribute to the satisfaction of the client and increase self-training motivation.

Clinical evaluation of a wrist sensorimotor rehabilitation program for triangular fibrocartilage complex injuries

Introduction

Triangular fibrocartilage complex (TFCC) injuries are associated with distal radioulnar joint (DRUJ) instability and impaired wrist proprioception. Sensorimotor training of extensor carpi ulnaris (ECU) and pronator quadratus (PQ) can enhance DRUJ stability. With limited evidence on effectiveness of TFCC sensorimotor rehabilitation, this study aimed to evaluate the effects and feasibility of a novel wrist sensorimotor rehabilitation program (WSRP) for TFCC injuries.

Methods

Patients diagnosed with TFCC injuries were recruited from May 2018 to January 2020 at an outpatient hand clinic in Singapore General Hospital. There are four stages in WSRP: (1) pain control, (2) muscle re-education and joint awareness, (3) neuromuscular rehabilitation, and (4) movement normalization and function. WSRP also incorporated dart throwing motion and proprioceptive neuromuscular facilitation. Outcome measures included grip strength measured with grip dynamometer, numerical pain rating scale, joint position sense (JPS) measurement, weight bearing measured with the 'push-off' test, and wrist function reported on the Patient Rated Wrist Hand Evaluation.

Results

Ten patients completed the WSRP. Mean changes were compared with minimal clinically important differences (MCID) for outcomes. All patients achieved MCID on pain, 70% of patients achieved MCID on grip strength, weight bearing and wrist function. Paired t-tests and Cohen's D for outcome measures were calculated. There were large effect sizes of 2.47, 1.35, and 2.81 for function, grip strength and pain respectively, and moderate effect sizes of 0.72 and 0.39 for axial loading and JPS respectively.

Discussion

WSRP presents a potential treatment approach in TFCC rehabilitation. There is a need for future prospective clinical trials with control groups.

The Biomechanical Effects of Simulated Radioscapholunate Fusion With Distal Scaphoidectomy, 4-Corner Fusion With Complete Scaphoidectomy, and Proximal Row Carpectomy Compared to the Native Wrist

PURPOSE

To determine the effect of simulated radioscapholunate fusion with distal scaphoid excision (RSLF+DSE), 4-corner fusion with scaphoidectomy (4-CF), and proximal row carpectomy (PRC) on the wrist's range of motion (ROM), contact pressure, and contact force in a cadaveric model.

METHODS

Ten freshly frozen cadaveric wrists were tested under 4 sequential conditions: native wrist, RSLF+DSE, 4-CF, and PRC. The simulated fusions were performed using two 1.6-mm Kirschner wires. The ROM in the flexion-extension and radioulnar deviation planes was evaluated. Contact area, contact pressure, and contact force were measured at the scaphocapitolunate joint for the RSLF+DSE simulation and radiocarpal joint for the 4-CF and PRC simulations. Mechanical testing was performed using a 35-N uniaxial load and pressure-sensitive film.

RESULTS

The RSLF+DSE and 4-CF groups had a decreased wrist arc ROM compared with the native wrist. The PRC group had a greater wrist arc ROM compared with the RSLF+DSE and 4-CF groups, but compared to the native wrist, it demonstrated a mildly decreased wrist arc ROM. The carpal pressure and contact force were significantly increased in the RSLF+DSE, 4-CF, and PRC groups compared with those in the native wrist. The RSLF+DSE group had the smallest increase in the carpal pressure and contact force, whereas the PRC group had the greatest increase.

CONCLUSIONS

Our study validates previous findings that PRC is motion-conserving but has the greatest contact force, whereas RSLF-DSE and 4-CF may cause a decrease in the ROM but have lower contact forces.

CLINICAL RELEVANCE

Understanding the underlying native wrist biomechanics and alterations following different surgical treatments may assist hand surgeons in their clinical decision making for the treatment of stage II scapholunate advanced collapse.

An in vitro hand simulator for simultaneous control of hand and wrist movements

A human hand is a complex biomechanical system, in which bones, ligaments, and musculotendon units dynamically interact to produce seemingly simple motions. A new physiological hand simulator has been developed, in which electromechanical actuators apply load to the tendons of extrinsic hand and wrist muscles to recreate movements in cadaveric specimens in a biofidelic way. This novel simulator simultaneously and independently controls the movements of the wrist (flexion/extension and radio-ulnar deviation) and flexion/extension of the fingers and thumb. Control of these four degrees of freedom (DOF) is made possible by actuating eleven extrinsic muscles of the hand. The coupled dynamics of the wrist, fingers, and thumb, and the over-actuated nature of the human musculoskeletal system make feedback control of hand movements challenging. Two control algorithms were developed and tested. The optimal controller relies on an optimization algorithm to calculate the required tendon tensions using the collective error in all DOFs, and the action-based controller loads the tendons solely based on their actions on the controlled DOFs (e.g., activating all flexors if a flexing moment is required). Both controllers resulted in hand movements with small errors from the reference trajectories (<3.4); however, the optimal controller achieved this with 16% lower total force. Owing to its simpler structure, the action-based controller was extended to enable feedback control of grip force. This simulator has been shown to be a highly repeatable tool (<0.25 N and <0.2 variations in force and kinematics, respectively) for in vitro analyses of human hand biomechanics.

SMoC-Wrist: a sensorimotor control-based exercise program for patients with chronic wrist pain

STUDY DESIGN

This is a narrative review.

INTRODUCTION

Chronic wrist pain is a common disorder that can lead to considerable disability in performing activities in daily living and at work. Patients with nonspecific chronic wrist pain are regularly referred to a physiotherapist/hand therapist. Immobilization, avoiding excessive wrist load, steroid injections, and various physical therapy methods predominantly focus on the pain itself. However, these methods often do not result in a satisfactory long-term pain relief.

PURPOSE OF THE STUDY

In this article, we will describe the principles behind and content of a sensorimotor control-based exercise program as introduced by Videler et al., modified and substantiated by current insights into sensorimotor control training and wrist kinetics.

METHODS

Both structure and content of the modified exercise program (SMoC-wrist) are substantiated by recent scientific literature.

RESULTS

A clear 4-level exercise model based on sensorimotor principles is presented, that is, proprioceptive level, conscious static/isometric level, conscious dynamic level, and unconscious dynamic level. The content of each level and the transition toward the next level are described in detail.

DISCUSSION

Besides the substantiation of the exercise program, possible outcome measures for joint position sense and kinesthesia of the wrist are discussed.

CONCLUSION

We modified and substantiated a widely used exercise program for patients with nonspecific chronic wrist pain based on recent insights into sensorimotor control principles and wrist kinematics. The presented exercise program (SMoC-wrist) is not primarily focused on reducing pain but on functional reeducation and strengthening of the neuromusculoskeletal system on the basis of sensorimotor control principles.

A Reference Range of Dart-Thrower's Motion at the Wrist in a Healthy Adult Population

PURPOSE

Dart-thrower's motion (DTM) is a functional wrist movement from maximum radial extension to maximum ulnar flexion. This study defines a reference range of DTM in a healthy population.

METHODS

Goniometric measurements were collected from both wrists of 200 healthy volunteers. Mean age was 21.1 years (range, 18-25 years), 126 volunteers (63%) were female, and 177 (89%) were right-handed. Volunteers also reported perceived difficulty of performing DTM.

RESULTS

For male subjects, the mean arc of motion was 126° (range, 83°-166°) for dominant and 114° (range, 62°-148°) for nondominant wrists. For female subjects, the mean values were 129° (range, 79°-170°) and 126° (range, 70°-167°), respectively. On multiple regression analysis, female subjects had a significantly increased range of dominant and nondominant arc of motion compared with males. Older subjects had significantly increased dominant but reduced nondominant arc of motion. High inter- and intrarater reliability was observed for goniometric measurement of DTM (intraclass correlation coefficients, 0.93-0.98).

CONCLUSIONS

This study quantified a reference range of DTM in normal individuals.

CLINICAL RELEVANCE

This study provides a reference range for DTM in a young adult population, which may aid clinical comparison of measurements of wrist movement and evaluation of conditions and treatments that impact DTM.

Dart thrower's motion and the injured scapholunate interosseous ligament: A scoping review of studies examining motion, orthoses, and rehabilitation

STUDY DESIGN

Scoping review.

INTRODUCTION

Dart thrower's motion (DTM) of the wrist primarily arises from the midcarpal joint, and minimizes stress to the scapholunate interosseous ligament (SLIL). After SLIL injury or surgery, early controlled DTM may reduce the effects of prolonged immobilization, while protecting SLIL integrity.

PURPOSE OF THE STUDY

To summarize the literature on the effects of DTM on the injured and surgically repaired SLIL and the extent to which various DTM orthotic designs promote SLIL recovery.

METHODS

A systematic literature search was conducted within 6 databases for articles published between 2003 and March 2018. Eligible studies examined DTM in the context of SLIL injury or repair. Relevant data were extracted by 2 independent reviewers.

RESULTS

Of 425 identified articles, 15 were eligible for inclusion. Five biomechanical studies examined the influence of DTM on the injured SLIL, whereas 5 articles described DTM orthotic designs. Also included were five articles that reported outcomes when DTM was used in the rehabilitation protocol.

DISCUSSION

The included studies suggest limiting end ranges of DTM in the injured/repaired SLIL, while blocking orthogonal plane movements. Custom orthotic designs may accomplish this goal. DTM has been used in comprehensive therapy programs in small case studies reporting short-term and intermediate clinical outcomes.

CONCLUSIONS

Caution should be exercised with using DTM on the torn SLIL as gap increases, particularly at the end-range motion. Orthosis designs have potential to limit this motion to midrange, while allowing early movement. Further high-level research is needed to understand the influence of DTM on injured and postsurgical populations.

Demystifying Palmar Midcarpal Instability

Palmar midcarpal instability is an uncommon condition diagnosed clinically with a painful pathognomonic clunk on terminal ulnar deviation of the wrist. Various causes have been described, but congenital laxity of the carpal ligaments is thought to be a key contributor. Treatment commences with conservative measures. This includes proprioceptive training based on more recent concepts on the sensorimotor function of the wrist. When these measures plateau, surgery is considered. The lack of high-level evidence and consensus on its cause continue to hamper our understanding and knowledge of this condition. The purpose of this review is to examine the current evidence to conceptualize this mysterious, yet infrequent phenomenon, and to provide an algorithm on its management.

Motion and Strength Analysis of 2-Tine Staple and K-Wire Fixation in Scapholunate Ligament Stabilization in a Cadaver Model

Purpose

Previous studies have demonstrated the benefits of 2- and 4-tine staple fixation in scapholunate interosseous ligament (SLIL) reconstruction, including improved rotational control and avoidance of the articular surface. This study compared scaphoid and lunate kinematics after SLIL fixation with traditional Kirschner wire (K-wire) fixation or 2-tine staple fixation.

Methods

Eight fresh frozen cadaver arms with normal scapholunate (SL) intervals were included. Infrared motion capture was used to assess kinematics between the scaphoid and lunate as the wrists were moved through a simulated dart-throw motion. Kinematic data were recorded for each wrist in 4 states: SLIL intact, SLIL sectioned, K-wire fixation across SL interval and scaphocapitate joint, and 2-tine Nitinol staple fixation across SL interval. Strength of the SL staple fixation was evaluated using an axial load machine to assess load to failure of the staple construct.

Results

Range of motion of the scaphoid and lunate with SLIL intact and SLIL sectioned were similar. K-wire fixation across the SL interval significantly decreased the overall wrist range of motion as well as scaphoid and lunate motion in all planes except for scaphoid flexion. Conversely, scaphoid and lunate motion after staple fixation was similar to that in normal wrists, except for a significant decrease in scaphoid extension. Under axial load simulating a ground-level fall, 3 of 8 arms demonstrated no failure, and none of the failures was due to direct failure of the 2-tine staple.

Conclusions

This study demonstrates 2-tine staple fixation across the SL interval is effective in providing initial stability and maintaining physiologic motion of the scaphoid and lunate compared with K-wire fixation after SLIL injury.

Clinical relevance

This study demonstrates an alternate technique for the stabilization of the SL interval in repair of acute SLIL injuries using 2-tine staple fixation, which maintains near physiologic motion of the scaphoid and lunate after SLIL injury.

Dimensionality Reduction and Motion Clustering During Activities of Daily Living: Three-, Four-, and Seven-Degree-of-Freedom Arm Movements

This paper is the first in a two-part series analyzing human arm and hand motion during a wide range of unstructured tasks. The wide variety of motions performed by the human arm during daily tasks makes it desirable to find representative subsets to reduce the dimensionality of these movements for a variety of applications, including the design and control of robotic and prosthetic devices. This paper presents a novel method and the results of an extensive human subjects study to obtain representative arm joint angle trajectories that span naturalistic motions during Activities of Daily Living (ADLs). In particular, we seek to identify sets of useful motion trajectories of the upper limb that are functions of a single variable, allowing, for instance, an entire prosthetic or robotic arm to be controlled with a single input from a user, along with a means to select between motions for different tasks. Data driven approaches are used to discover clusters and representative motion averages for the wrist 3 degree of freedom (DOF), elbow-wrist 4 DOF, and full-arm 7 DOF motions. The proposed method makes use of well-known techniques such as dynamic time warping (DTW) to obtain a divergence measure between motion segments, Ward's distance criterion to build hierarchical trees, and functional principal component analysis (fPCA) to evaluate cluster variability. The emerging clusters associate various recorded motions into primarily hand start and end location for the full-arm system, motion direction for the wrist-only system, and an intermediate between the two qualities for the elbow-wrist system.

Importance of Wrist Movement Direction in Performing Activities of Daily Living Efficiently

The wrist is an essential component in performing the activities of daily living (ADLs) associated with a high quality of life. After a neurological disorder, motor function of the hand and wrist can be affected, reducing quality of life. Many experiments have illustrated that more wrist flexion/extension is required than radial/ulnar deviation when performing ADLs; however, how this result translates to efficiency in performing ADLs has not been investigated. Motivated by clinical assessment during neurorehabilitation, in this paper we investigate with able-bodied participants how performing tasks representative of the Jebsen-Taylor Hand Function Test are impacted when a splint constrains the user to a single rotational degree of freedom of the wrist. Twenty participants enrolled in the study, performing five tasks under five conditions, including constraint to pure flexion/extension and radial/ulnar deviation. The importance of wrist movement direction in performing ADLs efficiently found in this study could shape clinical wrist rehabilitation paradigms and wrist rehabilitation robot designs.

Proposal for a Method to Measure the Range of Dart-Throwing Motion

Purpose

To examine the reliability of a novel technique to measure the range of the dart-throwing motion.

Methods

Two raters measured the range of the dart-throwing motion in 40 healthy subjects. For the measurement, subjects were asked to perform a simulated hammering motion using various experimental tools (a real hammer, a thick wooden rod, and a thin wooden rod). The inclination angle of the tool in the vertical plane was measured with a manual goniometer at the maximal position of radial extension and ulnar flexion. The sum of these angles was defined as the range of the dart-throwing motion. To evaluate relative interrater reliability, intraclass correlation coefficients were calculated. To account for absolute reliability, Bland-Altman analysis was performed.

Results

Intraclass correlation coefficients ranged 0.72 to 0.86. Bland-Altman analysis revealed that some systematic errors existed when the measurement was carried out with the real hammer or the thin rod, but not the thick rod. The 95% confidence intervals of minimal detectable change for the thick rod were 36.0° and 35.8° for the dominant and nondominant sides, respectively. Measured values between the experimental tools were similar.

Conclusions

Relative reliability was shown to be good or moderate for each set of measurements. Some refinements are required to reduce measurement error. Accuracy of measurement should also be confirmed.

Clinical relevance

No standardized methods for measuring the range of the dart-throwing motion have yet been established. Our technique can be performed rapidly and with easily available materials, producing reliable measurements for the range of the dart-throwing motion.

In-vivo three-dimensional motion analysis of the wrist during dart-throwing motion after midcarpal fusion and radioscapholunate fusion

We recorded the dart-throwing motion and basic motion tasks in patients following radioscapholunate fusion and midcarpal fusion with a three-dimensional motion capture system in vivo, using digital infrared cameras to track the movement of reflective skin markers on the hand and forearm. During the dart-throwing motion, 20 healthy volunteers showed a median range of motion of 107°. As expected, patients had significantly reduced wrist range of motion during basic motion tasks and dart-throwing motion compared with the healthy controls, except for ulnar flexion occurring in the dart-throwing motion in patients treated by midcarpal fusion and radial deviation after midcarpal fusion or radioscapholunate fusion. In addition, patients who had undergone radioscapholunate fusion had significantly reduced range of motion during dart-throwing motion compared with patients after midcarpal fusion.

The effect of surgery for basal osteoarthritis of the thumb on dart thrower's motion

This study aimed to identify the effects of basal thumb surgery on the range of dart thrower's motion. Thirteen fresh-frozen cadaveric specimens were placed in a customized jig. Simulated scaphotrapeziotrapezoid joint fusion was carried out on all specimens. Half the specimens then underwent trapeziectomy and the rest had excision of the distal pole of the scaphoid. Simulated scaphotrapeziotrapezoid fusion reduced the range of dart thrower's motion to 89% of the range in the intact wrists, from a mean of 117° to 104°. Although this reduction is not large, it was statistically significant. Simulated trapeziectomy caused a very small increase in dart thrower's motion range compared with the range in the intact wrists. Simulated distal pole of scaphoid excision did not change the range of dart thrower's motion. These results may inform preoperative decisions for surgical management of basal osteoarthritis of the thumb.

An Approach to Robotic Testing of the Wrist Using Three-Dimensional Imaging and a Hybrid Testing Methodology

Robotic technology is increasingly used for sophisticated in vitro testing designed to understand the subtleties of joint biomechanics. Typically, the joint coordinate systems in these studies are established via palpation and digitization of anatomic landmarks. We are interested in wrist mechanics in which overlying soft tissues and indistinct bony features can introduce considerable variation in landmark localization, leading to descriptions of kinematics and kinetics that may not appropriately align with the bony anatomy. In the wrist, testing is often performed using either load or displacement control with standard material testers. However, these control modes either do not consider all six degrees-of-freedom (DOF) or reflect the nonlinear mechanical properties of the wrist joint. The development of an appropriate protocol to investigate complexities of wrist mechanics would potentially advance our understanding of normal, pathological, and artificial wrist function. In this study, we report a novel methodology for using CT imaging to generate anatomically aligned coordinate systems and a new methodology for robotic testing of wrist. The methodology is demonstrated with the testing of 9 intact cadaver specimens in 24 unique directions of wrist motion to a resultant torque of 2.0 N·m. The mean orientation of the major principal axis of range of motion (ROM) envelope was oriented 12.1 ± 2.7 deg toward ulnar flexion, which was significantly different (p < 0.001) from the anatomical flexion/extension axis. The largest wrist ROM was 98 ± 9.3 deg in the direction of ulnar flexion, 15 deg ulnar from pure flexion, consistent with previous studies [1,2]. Interestingly, the radial and ulnar components of the resultant torque were the most dominant across all directions of wrist motion. The results of this study showed that we can efficiently register anatomical coordinate systems from CT imaging space to robotic test space adaptable to any cadaveric joint experiments and demonstrated a combined load-position strategy for robotic testing of wrist.

A novel staged wrist sensorimotor rehabilitation program for a patient with triangular fibrocartilage complex injury: A case report

STUDY DESIGN

Case report.

INTRODUCTION

Studies have highlighted the sensory innervations and stabilizing role of forearm muscles on wrist joint and implications to wrist sensorimotor rehabilitation. This case explored the novel incorporation of dart-throwing motion and proprioceptive neuromuscular facilitation in wrist sensorimotor rehabilitation.

PURPOSE OF THE STUDY

To describe and evaluate a staged wrist sensorimotor rehabilitation program for a patient with triangular fibrocartilage complex (TFCC) injury.

METHODS

The patient participated in the staged program for 9 sessions over a 3-month period. Treatment involved neuromuscular strengthening at the wrist and movement normalization of the upper extremity. Outcome measures were grip strength, visual analog scale, joint position sense, Quick Disabilities of the Arm, Shoulder and Hand, and patient-rated wrist evaluation.

RESULTS

The patient showed improvement in all outcome measures. Most outcomes exceeded the established minimal clinically important difference values.

DISCUSSION

The results suggest that dart-throwing motion and proprioceptive neuromuscular facilitation are beneficial in rehabilitation of TFCC injury.

CONCLUSIONS

This is the first study that incorporated dart-throwing motion and proprioceptive neuromuscular facilitation in the sensorimotor rehabilitation of TFCC injury and yielded promising results. There is a need to further evaluate the program in prospective randomized controlled trial recruiting a larger group of patients with TFCC injury.

Predicting Carpal Bone Kinematics Using an Expanded Digital Database of Wrist Carpal Bone Anatomy and Kinematics

The wrist can be considered a 2 degrees-of-freedom joint with all movements reflecting the combination of flexion-extension and radial-ulnar deviation. Wrist motions are accomplished by the kinematic reduction of the 42 degrees-of-freedom of the individual carpal bones. While previous studies have demonstrated the minimal motion of the scaphoid and lunate as the wrist moves along the dart-thrower's path or small relative motion between hamate-capitate-trapezoid, an understanding of the kinematics of the complete carpus across all wrist motions remains lacking. To address this, we assembled an open-source database of in vivo carpal motions and developed mathematical models of the carpal kinematics as a function of wrist motion. Quadratic surfaces were trained for each of the 42-carpal bone degrees-of-freedom and the goodness of fits were evaluated. Using the models, paths of wrist motion that generated minimal carpal rotations or translations were determined. Model predictions were best for flexion-extension, radial-ulnar deviation, and volar-dorsal translations for all carpal bones with R ²  > 0.8, while the estimates were least effective for supination-pronation with R ²  < 0.6. The wrist path of motion's analysis indicated that the distal row of carpal bones moves rigidly together (<3° motion), along the anatomical axis of wrist motion, while the bones in the proximal row undergo minimal motion when the wrist moves in a path oblique to the main axes. The open-source dataset along with its graphical user interface and mathematical models should facilitate clinical visualization and enable new studies of carpal kinematics and function. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 37:2661-2670, 2019.

Qualification of Wrist Functional Performance During Dart Thrower's Movement

Recently, numerous comprehensive studies have been concentrating on the intricate kinematics of the wrist joint functionality captured with dart thrower's movement. It is envisaged that the wrist capability in performing daily activities can be more accurately characterized or encapsulated in the dart thrower's movement. This study examines the characteristic function of wrist movements during dart-throwing motion using only gyroscopic data measured from inertial sensors. A multi-dimensional form of dart throwing trajectory is described using quaternion representation associated with distance metric to quantitatively validate the functional wrist performance between two cohorts; healthy controls and patients. Eight normal subjects and eight patients engaged in a series of clinical trials conducted after undergoing post-surgical reconstructive procedures of the wrist joint. The discriminative results in terms of silhouette clustering evaluation show that the use of distance metric values based quaternion trajectory is well-matched consistently with subjective expert assessments. Our proposed approach captures the relative motions underpinning the wrist joint instead of relying on the traditional measure based on the range of motion measure. Therefore, this paper proposes a reliable approach to dynamically capture the wrist functionality during dart thrower's movement; a movement envisaged to describe the ability to engage in daily life activities. These quantitative outcomes in terms of measurement consistency will provide insightful information in understanding the significant changes in wrist joint signatures associated with various scenarios.

Coordination of human movements resulting in motor strategies exploited by skilled players during a throwing task

In this study, we investigated the underlying mechanisms of a motor system that affects skills and strategies of expert dart throwers. Eight experts participated in our experiment and each subject performed 42 throws. Kinematics of the shoulder, elbow, wrist, and dart were recorded by six high-speed cameras (200 Hz). The vertical error curve over time was calculated based on both hand and dart trajectories to clarify their relationship and interaction, which could attribute to their skills. Moreover, the kinematics of the dart (speed and direction) and angular kinematics of the elbow and wrist at the time of release were investigated to elucidate which parameters constitute the throwing strategies of experts. Experimental results showed that expert's throwing can be classified into two strategies, i.e., reducing timing sensitivity and reducing timing error. These strategies were derived from the spatial and temporal controls of the hand trajectory. Moreover, we confirmed that the speed of the dart and angular acceleration of the wrist joint at the time of release were highly correlated with the time-window for successful release. These results imply that the two strategies are characterized not only by a spatiotemporal relationship between the hand and dart trajectories, but also by relationships with release kinematic parameters of the proximal joint and the dart. Understanding characteristics which lead to strategies of skilled throwers would provide effective training methodology for beginners.

An In Vitro Study to Determine the Effect of Ulnar Shortening on Distal Forearm Loading During Wrist and Forearm Motion: Implications in the Treatment of Ulnocarpal Impaction

PURPOSE

To evaluate the effect of ulnar shortening on distal forearm loading following simulated dynamic motion.

METHODS

Ulnar shortening was simulated using a custom-built adjustable implant to simulate up to 4 mm of ulnar shortening (-4 mm) in 9 cadaveric extremities. Load cells were placed in the distal ulna and radius to quantify axial loading. Using a wrist and forearm motion simulator, absolute and percentage loads were measured during dynamic flexion, ulnar deviation (UD), flexion dart throw (DT), and pronation.

RESULTS

There was a significant decrease in absolute and percentage distal ulnar loads at each interval of ulnar shortening during flexion, UD, DT, and pronation. The distal ulna bore no compressive loads, and in fact, tensile loads were measured in the ulna at 2 mm of ulnar shortening during DT and pronation, at 3 mm during flexion, and at 4 mm during UD.

CONCLUSIONS

A progressive decrease in distal ulnar loads with generation of tensile loads was observed with sequential ulnar shortening.

CLINICAL RELEVANCE

Ulnar shortening greater than 2 mm can result in tensile loading in the distal ulna. When managing ulnar impaction syndrome, excessive shortening may not be required to provide relief of symptoms.

Does Object Height Affect the Dart Throwing Motion Angle during Seated Activities of Daily Living?

Complex wrist motions are needed to complete various daily activities. Analyzing the multidimensional motion of the wrist is crucial for understanding our functional movement. Several studies have shown that numerous activities of daily livings (ADLs) are performed using an oblique plane of wrist motion from radial-extension to ulnar-flexion, named the Dart Throwing Motion (DTM) plane. To the best of our knowledge, the DTM plane angle performed during ADLs has not been compared between different heights (e.g. table, shoulder and head height), as is common when performing day-to-day tasks. In this study, we compared DTM plane angles when performing different ADLs at three different heights and examined the relationship between DTM plane angles and limb position. We found that height had a significant effect on the DTM plane angles - the mean DTM plane angle was greater at the lower level compared to the mid and higher levels. A significant effect of shoulder orientation on mean DTM plane angles was shown in the sagittal and coronal planes. Our findings support the importance of training daily tasks at different heights during rehabilitation following wrist injuries, in order to explore a large range of DTM angles, to accommodate needs of common ADLs.

The Effect of Radioscapholunate Fusion With and Without Distal Scaphoid and Triquetrum Excision on Capitolunate Contact Pressures

PURPOSE

To determine the effects of motion-increasing modifications to radioscapholunate (RSL) arthrodesis on capitolunate contact pressure in cadaveric wrist specimens.

METHODS

Ten fresh-frozen cadaveric wrists were dissected of all superficial soft tissue, potted in polymethyl-methacrylate, and the carpus exposed via a ligament-sparing capsulotomy. An RSL arthrodesis was simulated using 2 2.4-mm distal radius plates with locking screws. The distal scaphoid pole and triquetrum were removed with an osteotome and rongeur, respectively. Contact area, pressure, and force were measured in the capitolunate joint during the application of a 35-N uniaxial load using pressure-sensitive film. Measurements were obtained before and after simulated RSL fusion, following distal scaphoidectomy and after triquetrectomy.

RESULTS

The combination of RSL fusion with distal scaphoid excision (DSE) increased contact forces in the capitolunate joint by 50% over controls. An RSL fusion, and RSL fusion with DSE and triquetrum excision (TE), exhibited intermediate levels of contact force between controls and RSL fusion with DSE. Capitolunate contact pressures were similar between all experimental groups. Contact area in the capitolunate joint increased by 43% after RSL fusion with DSE over intact specimen controls. Lastly, contact area in wrists with RSL fusion, and RSL fusion with DSE and TE, were elevated, but not significantly different from intact controls.

CONCLUSIONS

A DSE performed at the time of RSL fusion results in increased midcarpal joint contact force and area, with resultant contact pressures unchanged. Triquetrectomy, which has been previously shown to improve range of motion, did not increase contact forces in the capitolunate joint.

CLINICAL RELEVANCE

If a surgeon is contemplating performing an RSL arthrodesis with DSE, we recommend adding a triquetrectomy to improve motion because this does not add to the potentially deleterious effects of increased midcarpal contact force.

Test-retest reliability of goniometric measurements of the range of dart-throwing motion

[Purpose] To examine the reliability of using a manual goniometer for measuring the range of dart-throwing motion. [Participants and Methods] The range of dart-throwing motion in 24 healthy participants was measured by three raters on the same day, and one rater repeated the measurement on another day of the same week. The stationary arm of the goniometer was placed along the radius, and the moveable arm was placed along the shaft of the second metacarpal, approximately 45° supinated from Lister's tubercle. All of the participants performed the dart-throwing motion on a plane that passed through the anatomical neutral wrist position, inclined 45° to the orthogonal anatomical plane. [Results] The intra-rater reliability was moderate (0.5-0.75) only for some parameters of the radial extension, and the intraclass correlation coefficients (ICCs) of all other parameters were <0.5. For the inter-rater reliability, the ICCs of all parameters were <0.5. Brand-Altman analysis revealed some fixed biases between the raters, although no proportional bias was observed. [Conclusion] The goniometric measurement procedure examined in this study appeared to be unsuitable for clinical use because of its poor reliability.

A composite 3D printed model of the midcarpal joint

Three-dimensional (3D) printing has recently been developed as a resource for teaching human anatomy through the accurate reproduction of anatomical specimens. Using a composite 3D printed model with the incorporation of metal and magnets, we were able to demonstrate and analyse movements at the midcarpal joint during the 'dart thrower's motion', which is an important motion in daily activities involving the use of the hand. The hand component with the distal row of carpal bones was subjected to flexion and extension at the midcarpal joint and observed for simultaneous abduction/adduction. Notable adduction was observed in the flexed position as compared to the extended position. Moreover, while the primary movements at the midcarpal joint were taking place in the medial part of the joint, the lateral part of the joint (which is ellipsoid) served to accommodate the arc of movement. We suggest that such composite 3D printed models are useful teaching tools for enhancing the understanding of complex joint movements.

Wrist Plane of Motion and Range During Daily Activities

OBJECTIVE. The dart-throwing motion (DTM) is a multiplane wrist motion that is needed for many daily occupations. Mobilization along the DTM plane may be essential for rehabilitation after wrist injury, but DTM angles are reported for the dominant hand alone, so their relevance to injury in the nondominant hand cannot be surmised. The aim of this study was to quantify the DTM plane angles for both hands during different activities of daily living (ADLs).

METHOD. Forty-three healthy participants wore a twin-axis electrogoniometer during ADLs.

RESULTS. No significant differences were found between the DTM plane angles of the dominant (20°–45°) and nondominant (15°–40°) hands. These angles varied by task and across participants.

CONCLUSION. The DTM plane is a functional motion used by both hands during ADLs. Because the DTM plane angle differs among hands, tasks, and individual clients, wrist rehabilitation involving the DTM plane should not be limited to a singular DTM plane angle.

A blinded, randomized trial comparing bicolumnar arthrodesis to radioscapholunate arthrodesis in scapholunate advanced collapse II arthritis: a pilot study

The purpose of this study was to compare the outcome of scaphoid excision with capitolunate and triquetrohamate arthrodesis (bicolumnar arthrodesis) to radioscapholunate arthrodesis in patients with scapholunate advanced collapse (SLAC) II wrist arthritis. Twelve patients with symptomatic SLAC II arthritis were recruited and randomized to receive either bicolumnar arthrodesis or radioscapholunate arthrodesis. The primary outcome was wrist function as assessed by the patient rated wrist evaluation. Secondary outcomes included range of motion, grip strength and the Mayo wrist score. A linear mixed-effects model was used to evaluate the effects of bicolumnar arthrodesis and radioscapholunate arthrodesis in treating SLAC II arthritis. Patients receiving bicolumnar arthrodesis had more improvement in their wrist function compared with patients receiving radioscapholunate arthrodesis. A high rate of re-operation was observed in patients receiving radioscapholunate arthrodesis. In SLAC II arthritis, the expected benefit of preserving the midcarpal joint was not observed. Scapholunate ligament disruption makes radioscapholunate arthrodesis a technically challenging operation.

LEVEL OF EVIDENCE

I.

Force Required to Maintain Reduction of a Preexisting Scapholunate Dissociation

PURPOSE

To determine the force required to maintain reduction of Geissler grade 4 scapholunate dissociations during physiological wrist motions.

METHODS

Fresh-frozen cadaveric wrists with Geissler grade 4 scapholunate dissociations were identified by arthroscopy. Following reduction, a load cell was attached to measure the force across the scapholunate joint at a neutral position and during 4 different wrist motions re-created using a servohydraulic wrist simulator, including a large flexion-extension motion (FEM), small and large dart-thrower's motions (DTMs), and a large DTM with ulnar offset.

RESULTS

Five wrists with isolated preexisting scapholunate interosseous ligament (SLIL) tears were analyzed. The force required to maintain reduction was significantly greater in extension than in flexion during the large FEM and large DTM with ulnar offset. The forces were significantly larger in this study of preexisting SLIL dissociations compared with results from a prior study of acutely sectioned SLILs. In addition, forces to maintain reduction during DTMs were significantly less than forces during FEMs. Finally, a set of 3 wrists with preexisting scapholunate and lunotriquetral interosseous ligament (LTIL) tears were identified and had significantly decreased forces to maintain reduction at maximum extension and had decreased maximal forces during a cycle of motion compared with the wrists with isolated SLIL tears.

CONCLUSIONS

The forces required to maintain reduction of a Geissler grade 4 wrist are higher than forces after acutely sectioned SLIL. The forces are greater in extension than in flexion and less during the DTM compared with the FEM. Wrists with both SLIL and LTIL tears required less force to maintain reduction than those with isolated SLIL tears.

CLINICAL RELEVANCE

This study helps determine the strength of reconstruction required to maintain reduction of a Geissler grade 4 scapholunate dissociation.

Forces in the Distal Radius During a Pushup or Active Wrist Motions

PURPOSE

To determine the 6 degrees of freedom forces and moments in the distal radius that occur during a pushup or other active wrist motions.

METHODS

Eight fresh-frozen cadaveric wrists were moved through 6 physiological motions and held at 1 static pushup position while the force through the distal radius was measured with a 6 degrees of freedom load cell. Three levels of compressive force were applied at the pushup position.

RESULTS

Active wrist motions caused axial forces up to 283 N and moments up to 0.7 N-m. Those motions with a smaller range had significantly smaller axial forces than the larger flexion-extension or dart-thrower's motions. With an 89-N pushup force applied, the average maximum axial force was 69 N, the radially directed force was 12 N, and the moment about the radioulnar axis was 2.3 N-m. Linear extrapolation of the forces to 100% body weight indicate that the axial force going through the distal radius would be 663 N, the radial force would be 147 N, and the moment about the radioulnar axis would be 18.6 N-m.

CONCLUSIONS

Large distal radius forces and moments can occur during pushup and active wrist motions. There are not only large axial compressive forces but also nontrivial radially directed forces.

CLINICAL RELEVANCE

This study may help surgeons and therapists better treat complicated distal radius fractures as well as provide for better comparisons of existing or new distal radius plates and constructs that are designed to treat these complicated loading patterns.

A comparison of dart thrower's range of motion following radioscapholunate fusion, four-corner fusion and proximal row carpectomy

Dart thrower's motion is the functional coupled movement of the wrist from radial extension to ulnar flexion. The aim of this study was to evaluate dart thrower's motion following three surgeries: radioscapholunate fusion, four-corner fusion and proximal row carpectomy. Six fresh-frozen cadaver forearms were dissected. Sequential loading of tendons resulted in radial extension and ulnar flexion allowing dart thrower's motion measurements at end range before and then again after each surgery. After radioscapholunate fusion, 74% of both radial extension and ulnar flexion were maintained. After four-corner fusion, radial extension decreased to 53% and ulnar flexion to 84% of control motion. Proximal row carpectomy did not statistically significantly alter radial extension, but decreased ulnar flexion to 87%. We found that dart thrower's motion is well maintained in three of these commonly used surgical treatments. These results may aid surgeons in managing patients by providing comparative functional movement following these procedures.

Association of wrist and forearm range of motion measures with self-reported functional scores amongst patients with distal radius fractures: a longitudinal study

Background

Patients with distal radius fractures (DRF) often have limited range-of-motion (ROM) in multiple planes of movement. No studies have comprehensively examined the impact of various ROM limitations on physical function.

Methods

We performed a multi-center, longitudinal study of 138 patients with conservatively managed DRF. ROM measures were taken at initial evaluation, and at 4 and 8 weeks later. Self-reported physical function was indexed by the Quick Disabilities of the Arm, Shoulder and Hand (QuickDASH).

Results

Wrist extension, active thumb opposition and a full composite grip were amongst the strongest ROM measures associated with functional scores over time. However, wrist radial deviation and forearm pronation were non-significantly associated with functional scores.

Conclusion

Given that ROM is potentially modifiable, the identification of important ROM measures associated with QuickDASH scores can potentially facilitate patient education and refine interventions to optimize functional recovery. Well-designed randomized intervention studies are however needed to confirm these association findings.

Psychometric properties of the goniometric assessment of the Dart Thrower’s Motion

Introduction

The Dart Thrower’s Motion is an important movement for hand function. A goniometric clinical measure of Dart Thrower’s Motion has been developed. However, its validity and reliability in people with wrist and hand injury is not known. This study investigated the inter-rater and test–retest reliability and criterion validity of the Dart Thrower’s Motion measure.

Methods

A cross-sectional design was used. Thirty-five participants with hand or wrist injury completed the goniometric assessment of the Dart Thrower’s Motion and goniometric wrist active range of motion assessment three times in a hand clinic. Two assessors and a reader to record the results were involved. Participants also completed the patient-rated wrist and hand evaluation.

Results

The intraclass correlation coefficients were 0.70–0.83 and 0.91–0.92, respectively for inter-rater and test–retest reliability in the injured hands indicating moderate to high reliability. The Pearson correlation coefficients between the Dart Thrower’s Motion measure and wrist active range of motion assessment ranged from 0.45 to 0.73, and with patient-rated wrist and hand evaluation ranged from −0.36 to −0.53. The results indicate that goniometric assessment of the Dart Thrower’s Motion has acceptable criterion validity.

Conclusion

The goniometric assessment of Dart Thrower’s Motion can be considered a valid and reliable clinical measure for measuring the impact of the injury to one’s hand and wrist range of motion and function. It shows its clinical utility in people with hand and wrist injury. It is hoped this simple measure can be eventually implemented in clinical settings, allowing for an increased understanding of an individual’s functional use of the hand and wrist.

Biomechanical Analysis of Palmar Midcarpal Instability and Treatment by Partial Wrist Arthrodesis

PURPOSE

To create a biomechanical model of palmar midcarpal instability by selective ligament sectioning and to analyze treatment by simulated partial wrist arthrodesis.

METHODS

Nine fresh-frozen cadaver arms were moved through 3 servohydraulic actuated motions and 2 passive wrist mobilizations. The dorsal radiocarpal, triquetrohamate, scaphocapitate, and scaphotrapeziotrapezoid ligaments were sectioned to replicate palmar midcarpal instability. Kinematic data for the scaphoid, lunate, and triquetrum were recorded before and after ligament sectioning and again after simulated triquetrohamate arthrodesis (TqHA) and radiolunate arthrodesis (RLA).

RESULTS

Following ligament sectioning, the model we created for palmar midcarpal instability was characterized by significant increases in (1) lunate angular velocity, (2) lunate flexion-extension, and (3) dorsal/volar motion of the capitate during dorsal/volar mobilizations. Simulated TqHA caused significantly more scaphoid flexion and less extension during the wrist radioulnar deviation motion. It also increased the amount of lunate and triquetral extension during wrist flexion-extension. Simulated RLA significantly reduced scaphoid flexion during both wrist radioulnar deviation and flexion-extension.

CONCLUSIONS

Both simulated arthrodeses eliminate wrist clunking and may be of value in treating palmar midcarpal instability. However, simulated RLA reduces proximal row motion whereas simulated TqHA alters how the proximal row moves. Long-term clinical studies are needed to determine if these changes are detrimental.

CLINICAL RELEVANCE

Palmar midcarpal instability is poorly understood, with most treatments based on pathomechanical assumptions. This study provides information that clinicians can use to design better treatment strategies for this unsolved condition.