The effects of wrist distraction on carpal kinematics

Clinical Outcomes of Total Wrist Arthroplasty in Patients With Rheumatoid Arthritis: Minimum 10-Year Follow-Up Study

PURPOSE

We developed a semiconstrained total wrist prosthesis that was used in a series of patients with rheumatoid arthritis. We previously reported favorable clinical outcomes for up to 5 years after surgery; however, the longer-term outcomes remain unclear. The objective of this study was to evaluate the clinical outcomes of this wrist prosthesis for the treatment of severe wrist rheumatoid arthritis during a minimum 10 years of follow-up.

METHODS

From 2010 through 2012, total wrist arthroplasty using the semiconstrained total wrist arthroplasty device was performed in 20 wrists in 20 patients with rheumatoid arthritis (five men and 15 women). The mean patient age was 64 years (range, 50-84 years). Preoperative radiographs showed Larsen grade IV changes in 16 wrists and grade V changes in four wrists. Patients were evaluated clinically and radiologically before surgery, 5 years after surgery, and 10 years or more after surgery. Evaluated parameters were the visual analog scale for pain, range of motion, Figgie score, and Disabilities of the Arm, Shoulder, and Hand score.

RESULTS

The minimum 10-year follow-up clinical results (mean, 11.3 years) were available for all 14 surviving patients (three men and 11 women). Significant improvements in the mean visual analog scale for pain, Figgie score, and Disabilities of the Arm, Shoulder, and Hand score, compared with those before surgery, were maintained from 5 years after surgery to the final follow-up. The mean wrist flexion angle tended to slightly decrease at 5 years after surgery compared with that before surgery but remained similar from 5 years after surgery to the final follow-up. The increase in the mean wrist extension angle, compared with that before surgery, was maintained from 5 years after surgery to the final follow-up. Radiographic evaluation had already revealed implant loosening in five of the 19 wrists at 5 years after surgery, but there were no new cases of component loosening identified at the final follow-up.

CONCLUSIONS

Total wrist arthroplasty using the semiconstrained arthroplasty system achieves favorable clinical outcomes with no serious complications requiring revision for 10 years after surgery.

TYPE OF STUDY/LEVEL OF EVIDENCE

Therapeutic IV.

Correlation between carpal rotational alignment and postoperative wrist range of motion following total wrist arthroplasty

BACKGROUND

Although total wrist arthroplasty (TWA) has become a common treatment option for wrists with damage due to rheumatoid arthritis (RA), the optimal implant axial alignment for TWA has been inadequately studied. This study was performed to investigate the relationships between implant alignment and carpal rotational alignment and the wrist range of motion (ROM) following TWA.

METHODS

This study included 18 patients who underwent TWA using a DARTS® Total Wrist System (Teijin Nakashima Medical, Okayama, Japan) for wrist RA. Pre- and 6-month postoperative computed tomography scans were performed, including the radial volar line (Rv), capitohamate axis (CH), and Rv-CH angle in axial scans. The wrist ROM was also measured. The relationship between the Rv-CH angle and ROM was examined.

RESULTS

The mean Rv-CH angle showed significant wrist pronation from 73.0° to 83.4° postoperatively. We observed a significant positive correlation (0.58) between the postoperative Rv-CH angle and extension and a significant negative correlation (- 0.56) between the postoperative Rv-CH angle and flexion.

CONCLUSIONS

Implantation of the DARTS® TWA prosthesis resulted in pronation of the carpal axial alignment, which was correlated with postoperative wrist extension. The volar cortex of the distal radius can be a novel reference axis for adequate implant placement.

Comparison of Wrist Motion and Grip Strength between Normal Caucasian, Southern Chinese and Japanese Populations

Background: Differences in structure and function of the hand and wrist between distinct populations affect our approach to treatment, expectations and functional outcomes. The aim of this study is to compare wrist motion and grip strength in Caucasian, Chinese and Japanese populations. Methods: A total of 424 normal wrists were evaluated that included 99 Japanese, 139 Caucasian and 186 Southern Chinese. Demographic information collected included age, gender, hand dominance and occupation. Evaluation included measurement of active motion and grip strength. Motion was measured using a goniometer. Grip strength was evaluated using a JAMAR dynamometer. Demographic information and evaluation was compared among the three cohorts using statistical tests. Multivariate mixed-effect model was further used to assess the racial impact on each evaluation controlling for demographic factors as well as two-hand measurements of everyone. Results: There was no difference in global wrist motion between the cohorts. We did find significant differences between the cohorts in all discrete measurements. Conclusions: Differences in wrist motion and grip strength between normal Japanese, Chinese and Caucasian populations may be due to bony structure rather than soft tissue properties. Knowledge of these disparities can provide references for personalised wrist examination, diagnosis, treatment and comparison of outcomes between different cohorts. Level of Evidence: Level III (Diagnostic).

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.

A Minimum 5-Year Longitudinal Study of a New Total Wrist Arthroplasty in Patients With Rheumatoid Arthritis

PURPOSE

To evaluate the longitudinal clinical outcomes using a new semiconstrained wrist prosthesis for the treatment of severe rheumatoid arthritis of the wrist.

METHODS

Twenty patients with rheumatoid arthritis (20 wrists) underwent total wrist arthroplasty with the prosthesis in a clinical trial. The preoperative Larsen classification was grade IV in 16 wrists and grade V in 4 wrists. Assessments were performed before surgery, 1.5 years after surgery, and at final follow-up (≥ 5 years after surgery) using the visual analog scale for pain, Figgie wrist score, Japanese version of the Disabilities of the Arm, Shoulder, and Hand (DASH) questionnaire, and plain radiographs.

RESULTS

At final follow-up, no patient had wrist pain. The preoperative flexion-extension arc at final follow-up was similar to the preoperative range. The mean 1.5-year postoperative Figgie score was significantly improved and was unchanged at final follow-up. The DASH score significantly improved from before surgery to 1.5 years after surgery; the DASH score was improved further at final follow-up, but not significantly. Five of the 19 wrists evaluated had radiographic findings indicating carpal component loosening at final follow-up; however, all patients with the loosening were asymptomatic and had not undergone revision surgery.

CONCLUSIONS

Total wrist arthroplasty using this wrist prosthesis leads to favorable clinical outcomes regarding pain relief and retained range of wrist motion.

TYPE OF STUDY/LEVEL OF EVIDENCE

Therapeutic IV.

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.

Optimal management of scapholunate ligament injuries

Scapholunate ligament (SLL) injuries are a common cause of wrist pain and instability. Treatment of SLL injuries requires intricate understanding of wrist anatomy and biomechanics. Mindful physical exam and appropriate diagnostic studies can orient the surgeon to the defined stage of injury. Review of the literature on each treatment by stage can prepare the upper extremity surgeon to provide the best evidence-based care. The optimal management of SLL injuries should result in a stable, painless wrist.

Motion-plane dependency of the range of dart throw motion and the effects of tendon action due to finger extrinsic muscles during the motion

[Purpose] To clarify the motion-plane dependency of the range of dart throw motion and the effects of tendon action due to long finger flexors and extensors during the motion. [Subjects and Methods] Forty healthy subjects attended the experiment, and the active range of wrist motion in seven motion planes was measured with an originally designed apparatus. [Results] The reliability of the measurement was acceptable. The range of dart throw motion depended on the motion planes, with a maximum at around the motion plane of 45° from the sagittal plane (45° of pronation). The tendon action of long finger muscles was shown in dart throw motion except in 45° of pronation. [Conclusion] Motion-plane dependency of the range of dart throw motion exists in healthy subjects. The absence of tendon action due to finger extrinsic muscles in dart throw motion at 45° might be one of the causes of the advantage of dart throw motion.

Biomechanical Evaluation of Carpal Kinematics during Simulated Wrist Motion

Background Flexion and extension of the wrist is achieved primarily at the radiocarpal and midcarpal joints. Carpal kinematics have been investigated, although there remains no consensus regarding the relative contribution of each bone to wrist motion. Purpose To determine the kinematics of the scaphoid, lunate, and capitate during unconstrained simulated wrist flexion/extension and to examine the effect of motion direction on the contribution of each bone. Materials and Methods Seven cadaveric upper extremities were tested in a passive wrist simulator with 10N tone loads applied to the wrist flexors/extensors. Scaphoid, lunate, and capitate kinematics were captured using optical tracking and analyzed with respect to the radius. Results Scaphoid and lunate motion correlated linearly with wrist motion (R² = 0.99, 0.97). In extension, the scaphoid and lunate extended 83 ± 19% and 37 ± 18% relative to total wrist extension (p = 0.03, 0.001), respectively. In flexion, the scaphoid and lunate flexed 95 ± 20% and 70 ± 12% relative to total wrist flexion (p = 1.0,0.01) , respectively. The lunate rotated 46 ± 25% less than the capitate and 35 ± 31% less than the scaphoid. The intercarpal motion between the scaphoid and lunate was 25 ± 17% of wrist flexion. Conclusion The scaphoid, lunate, and capitate move synergistically throughout planar wrist motion. The scaphoid and lunate contributed at a greater degree during flexion, suggesting that the radiocarpal joint plays a more critical role in wrist flexion. Clinical Relevance The large magnitude of differential rotation between the scaphoid and lunate may be responsible for the high incidence of scapholunate ligament injuries. An understanding of normal carpal kinematics may assist in positioning carpal bones during partial wrist fusions and in developing more durable wrist arthroplasty designs.

Electrogoniometer measurement and directional analysis of wrist angles and movements during the Sollerman hand function test

STUDY DESIGN

Clinical measurement.

INTRODUCTION

To investigate the characteristics of wrist motion (area, axis, and location) during activities of daily living (ADL) using electrogoniometry.

METHODS

A sample of 83 normal volunteers performed the Sollerman hand function test (SHFT) with a flexible biaxial electrogoniometer applied to their wrists. This technique is accurate and reliable and has been used before for assessment of wrist circumduction in normal volunteers. A software package was used to overlay an ellipse of best fit around the 2-dimensional trace of the electrogoniometer mathematically computing the area, location, and axis angle of the ellipse.

RESULTS

Most ADL could be completed within 20% of the total area of circumduction (3686°° ± 1575°°) of a normal wrist. An oblique plane in radial extension and ulnar flexion (dart-throwing motion plane) was used for rotation (-14° ± 32°) and power grip tasks (-29° ± 25°) during ADL; however, precision tasks (4° ± 28°), like writing, were performed more often in the flexion extension plane. In the dominant hand, only 2 power tasks were located in flexion region (cutting play dough [ulnar] and pouring carton [radial]), precision tasks were located centrally, and rotation and other power tasks were located in extension region.

DISCUSSION

This study has identified that wrist motion during the ADL requires varying degrees of movement in oblique planes. Using electrogoniometry, we could visualize the area, location, and plane of motion during ADL. This could assist future researchers to compare procedures leading to loss of motion in specific quadrants of wrist motion and its impact on patient's ability in performing particular ADL. It could guide hand therapists to specifically focus on retraining the ADL that may be affected when wrist range of motion is lost after injury.

LEVEL OF EVIDENCE

Diagnostic level III.

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.

Scaphoid tuberosity excursion is minimized during a dart-throwing motion: A biomechanical study

PURPOSE

The purpose of this study was to determine whether the excursion of the scaphoid tuberosity and therefore scaphoid motion is minimized during a dart-throwing motion.

METHODS

Scaphoid tuberosity excursion was studied as an indicator of scaphoid motion in 29 cadaver wrists as they were moved through wrist flexion-extension, radioulnar deviation, and a dart-throwing motion.

RESULTS

Study results demonstrate that excursion was significantly less during the dart-throwing motion than during either wrist flexion-extension or radioulnar deviation.

CONCLUSION

If the goal of early wrist motion after carpal ligament or distal radius injury and reconstruction is to minimize loading of the healing structures, a wrist motion in which scaphoid motion is minimal should reduce length changes in associated ligamentous structures. Therefore, during rehabilitation, if a patient uses a dart-throwing motion that minimizes his or her scaphoid tuberosity excursion, there should be minimal changes in ligament loading while still allowing wrist motion.

STUDY DESIGN

Bench research, biomechanics, and cross-sectional.

LEVEL OF EVIDENCE

Not applicable. The study was laboratory based.

Chronic Scapholunate Ligament Injury: Techniques in Repair and Reconstruction

Although the true incidence of scapholunate interosseous ligament (SLIL) injury is unknown, a study found that 35% of cadaveric wrists had some degree of scapholunate tear. Of those wrists with SLIL injury, 29% had evidence of arthrosis. Early recognition and treatment of these injuries can delay or prevent the onset of arthritis. This article details treatment options for SLIL injury across the spectrum of pathology with a particular emphasis on chronic scapholunate repair and reconstruction. New techniques and outcomes data also are presented.

A technique for quantifying wrist motion using four-dimensional computed tomography: approach and validation

Accurate quantification of subtle wrist motion changes resulting from ligament injuries is crucial for diagnosis and prescription of the most effective interventions for preventing progression to osteoarthritis. Current imaging techniques are unable to detect injuries reliably and are static in nature, thereby capturing bone position information rather than motion which is indicative of ligament injury. A recently developed technique, 4D (three dimensions + time) computed tomography (CT) enables three-dimensional volume sequences to be obtained during wrist motion. The next step in successful clinical implementation of the tool is quantification and validation of imaging biomarkers obtained from the four-dimensional computed tomography (4DCT) image sequences. Measures of bone motion and joint proximities are obtained by: segmenting bone volumes in each frame of the dynamic sequence, registering their positions relative to a known static posture, and generating surface polygonal meshes from which minimum distance (proximity) measures can be quantified. Method accuracy was assessed during in vitro simulated wrist movement by comparing a fiducial bead-based determination of bone orientation to a bone-based approach. The reported errors for the 4DCT technique were: 0.00-0.68 deg in rotation; 0.02-0.30 mm in translation. Results are on the order of the reported accuracy of other image-based kinematic techniques.

An anatomic and kinematic analysis of a new total wrist arthroplasty design

Background Total wrist arthroplasty (TWA) is a viable surgical treatment for disabling wrist arthritis. While current designs are a notable improvement from prior generations, radiographic loosening and failures remain a concern. Purpose The purpose of this investigation is to evaluate a new total wrist arthroplasty design kinematically. The kinematic function of a native, intact cadaveric wrist was compared with that of the same wrist following TWA. Method Six, fresh-frozen wrist cadaveric specimens were utilized. Each wrist was fixed to an experimental table and its range of motion, axis of rotation, and muscle moment arms were calculated. The following tendons were attached to the apparatus to drive motion: extensor carpi radialis longus (ECRL), extensor carpi radialis brevis (ECRB), extensor carpi ulnaris (ECU), flexor carpi radialis (FCR), flexor carpi ulnaris (FCU), and abductor pollicis longus (APL). The wrist was then manually moved along a guide by an experimenter through a series of motions including flexion-extension, radial-ulnar deviation, and circumduction. The experiment was then performed on the specimen following implantation of the TWA. Results Following the TWA procedure, there were statistically significant decreases in the ulnar deviation and the flexion/ulnar deviation component of dart throw ranges of motion. There were no statistically significant changes in flexion, extension, radial deviation, the extension/radial deviation component of the dart thrower motion, or the circumduction range of motion. Conclusions Kinematic analysis of the new TWA suggests that a stable, functional wrist is achievable with this design. Clinical Relevance While appreciating the limitations of a cadaveric study, this investigation indicates that the TWA design studied merits study in human populations.

An in vivo study of dynamic effects of wrist traction on the radiolunate and capitolunate joints

Introduction

We described the dynamic effects of traction on the radiolunate and capitolunate joints in a living body to explore the possibility of range of motion exercise of the wrist joint under traction as a new method of exercise.

Methods

Dynamic radiography was conducted while creating wrist passive movements by using manual traction and machinery traction with a measurement device. Subjects were 20 healthy men. The change in the percentage of contribution of the radiolunate and capitolunate joints with or without traction was calculated.

Results

Manual traction: During palmar flexion, the percentage of contribution of the radiolunate angle was increased from 39.4% to 49.9%, and the capitolunate angle was decreased from 60.6% to 50.1% with traction. During dorsiflexion, the radiolunate angle was increased from 60.2% to 70.0%, and the capitolunate angle was decreased from 39.8% to 30.0% with traction. Machinery traction: During palmar flexion, the radiolunate angle was increased from 46.1% to 56.4%, and the capitolunate angle was decreased from 53.9% to 43.6% with traction. During dorsiflexion, the radiolunate angle was increased from 68.7% to 72.0%, and the capitolunate angle was decreased from 31.3% to 28.0% with traction.

Conclusions

The movement of the radiolunate joint was increased and that of the capitolunate joint decreased with the addition of traction. Range of motion exercise with traction has the potential to be applied to an advanced rehabilitation program targeting the radiolunate joint under specific pathological conditions.

Joint preservation of the wrist using articulated distraction arthroplasty: a case report of a novel technique

Distraction arthroplasty of the ankle, elbow, and hip has become widely accepted and used within the orthopaedic community with excellent initial results which appear sustained. To date it has not been applied to the wrist in the same manner. A novel technique, drawn upon past success of articulated ankle distraction and static wrist distraction, was devised and evaluated by application of articulated wrist distraction performed over a 12-week period in a patient with poor functional outcome following limited wrist fusion. Posttreatment results showed improvement in range of motion (100-degree arc), subjective pain, and functional outcome measures (DASH 21.7, Mayo Wrist Score 80) comparable or better than either limited wrist fusion or proximal row carpectomy. Articulated wrist distraction initially appears to be a promising therapeutic option for the management of the stiff and painful wrist to maintain maximal function for which formal wrist arthrodesis may be the only alternative.

International Federation of Societies for Surgery of the Hand 2013 Committee's report on wrist dart-throwing motion

This report updates information on wrist dart-throwing (DT) motion, based on the most recent research published on the kinematics, kinetics, and clinical applications of DT motion. A wide range of DT planes exists. "Pure" DT motion is done along an oblique plane that intercepts the coronal and sagittal planes at the zero position, and occurs almost exclusively at the midcarpal joint with near zero scaphoid and lunate motion. "Functional" DT motion such as a hammering is done along an oblique plane that is almost parallel to the pure DT plane, but that has an offset toward the dorsal side. Functional DT rotation has greater scaphoid and lunate motion compared with pure DT motion. Midcarpal arthrodesis adversely affects DT motion compared with radiocarpal arthrodesis. During a DT motion, the mean and peak tendon forces of the flexor carpi ulnaris and the extensor carpi radialis longus were the greatest among wrist motors. By performing a task along the plane of DT motion, the scapholunate (SL) joint was stable and SL ligament elongation was minimal in healthy subjects. However, a more recent study of patients with SL dissociation revealed that DT exercises applied tensile forces on the SL ligament and induced an SL gap.

Dynamic motion analysis of dart throwers motion visualized through computerized tomography and calculation of the axis of rotation

We used a dynamic three-dimensional (3D) mapping method to model the wrist in dynamic unrestricted dart throwers motion in three men and four women. With the aid of precision landmark identification, a 3D coordinate system was applied to the distal radius and the movement of the carpus was described. Subsequently, with dynamic 3D reconstructions and freedom to position the camera viewpoint anywhere in space, we observed the motion pathways of all carpal bones in dart throwers motion and calculated its axis of rotation. This was calculated to lie in 27° of anteversion from the coronal plane and 44° of varus angulation relative to the transverse plane. This technique is a safe and a feasible carpal imaging method to gain key information for decision making in future hand surgical and rehabilitative practices.

A novel method to replicate the kinematics of the carpus using a six degree-of-freedom robot

Understanding the kinematics of the carpus is essential to the understanding and treatment of wrist pathologies. However, many of the previous techniques presented are limited by non-functional motion or the interpolation of points from static images at different postures. We present a method that has the capability of replicating the kinematics of the wrist during activities of daily living using a unique mechanical testing system. To quantify the kinematics of the carpal bones, we used bone pin-mounted markers and optical motion capture methods. In this paper, we present a hammering motion as an example of an activity of daily living. However, the method can be applied to a wide variety of movements. Our method showed good accuracy (1.0-2.6°) of in vivo movement reproduction in our ex vivo model. Most carpal motion during wrist flexion-extension occurs at the radiocarpal level while in ulnar deviation the motion is more equally shared between radiocarpal and midcarpal joints, and in radial deviation the motion happens mainly at the midcarpal joint. For all rotations, there was more rotation of the midcarpal row relative to the lunate than relative to the scaphoid or triquetrum. For the functional motion studied (hammering), there was more midcarpal motion in wrist extension compared to pure wrist extension while radioulnar deviation patterns were similar to those observed in pure wrist radioulnar deviation. Finally, it was found that for the amplitudes studied the amount of carpal rotations was proportional to global wrist rotations.

In vivo kinematics of the scaphoid, lunate, capitate, and third metacarpal in extreme wrist flexion and extension

PURPOSE

Insights into the complexity of active in vivo carpal motion have recently been gained using 3-dimensional imaging; however, kinematics during extremes of motion has not been elucidated. The purpose of this study was to determine motion of the carpus during extremes of wrist flexion and extension.

METHODS

We obtained computed tomography scans of 12 healthy wrists in neutral grip, extreme loaded flexion, and extreme loaded extension. We obtained 3-dimensional bone surfaces and 6-degree-of-freedom kinematics for the radius and carpals. The flexion and extension rotation from neutral grip to extreme flexion and extreme extension of the scaphoid and lunate was expressed as a percentage of capitate flexion and extension and then compared with previous studies of active wrist flexion and extension. We also tested the hypothesis that the capitate and third metacarpal function as a single rigid body. Finally, we used joint space metrics at the radiocarpal and midcarpal joints to describe arthrokinematics.

RESULTS

In extreme flexion, the scaphoid and lunate flexed 70% and 46% of the amount the capitate flexed, respectively. In extreme extension, the scaphoid extended 74% and the lunate extended 42% of the amount the capitates extended, respectively. The third metacarpal extended 4° farther than the capitate in extreme extension. The joint contact area decreased at the radiocarpal joint during extreme flexion. The radioscaphoid joint contact center moved onto the radial styloid and volar ridge of the radius in extreme flexion from a more proximal and ulnar location in neutral.

CONCLUSIONS

The contributions of the scaphoid and lunate to capitate rotation were approximately 25% less in extreme extension compared with wrist motion through an active range of motion. More than half the motion of the carpus when the wrist was loaded in extension occurred at the midcarpal joint.

CLINICAL RELEVANCE

These findings highlight the difference in kinematics of the carpus at the extremes of wrist motion, which occur during activities and injuries, and give insight into the possible etiologies of the scaphoid fractures, interosseous ligament injuries, and carpometacarpal bossing.

The mechanical axes of the wrist are oriented obliquely to the anatomical axes

BACKGROUND

the complex motions of the wrist are described in terms of four anatomical directions that are accomplished through the multiple articulations of the carpus. With minimal tendinous insertions, the carpus is primarily a passive structure. This emphasizes the importance of its mechanical properties, which few studies have examined to date. The purpose of the present study was to determine the mechanical properties of the wrist in twenty-four different directions of wrist motion.

METHODS

the moment-rotation mechanical behavior of six fresh-frozen cadaver wrists was determined in four directions: flexion, extension, ulnar deviation, and radial deviation. Twenty other directions that were a combination of these anatomical directions were also studied. A custom-designed jig was interfaced with a standard materials testing system to apply unconstrained moments. Moments of ± 2 Nm were applied, and the moment-rotation data were recorded and analyzed to determine the neutral zone, range of motion, and stiffness values as well as the orientation of the envelope of these values.

RESULTS

the envelope of wrist range-of-motion values was ellipsoidal in shape and was oriented obliquely (p < 0.001) to the direction of pure flexion-extension by a mean (and standard deviation) of 26.6° ± 4.4°. The largest wrist range of motion was a mean of 111.5° ± 10.2°, in the direction of ulnar flexion, 30° from pure flexion. The largest stiffness (mean, 0.4 Nm/deg) was in the direction of radial flexion, while the smallest stiffness (mean, 0.15 Nm/deg) was in the direction of ulnar flexion.

CONCLUSIONS

the mechanical axes of the wrist are oriented obliquely to the anatomical axes. The primary mechanical direction is one of radial extension and ulnar flexion, a direction along a path of the dart thrower's wrist motion.

CLINICAL RELEVANCE

understanding the mechanical function of the wrist can aid clinical treatment decisions, arthroplasty, and implant designs. The findings of this study provide new evidence that the mechanical axes of the wrist are not collinear with the anatomical axes.

Carpal and forearm kinematics during a simulated hammering task

PURPOSE

Hammering is a functional task in which the wrist generally follows a path of motion from a position of combined radial deviation and extension to combined ulnar deviation and flexion, colloquially referred to as a dart thrower's motion. The purpose of this study was to measure wrist and forearm motion and scaphoid and lunate kinematics during a simulated hammering task. We hypothesized that the wrist follows an oblique path from radial extension to ulnar flexion and that there would be minimal radiocarpal motion during the hammering task.

METHODS

Thirteen healthy volunteers consented to have their wrist and distal forearm imaged with computed tomography at 5 positions while performing a simulated hammering task. The kinematics of the carpus and distal radioulnar joint were calculated using established markerless bone registration methods. The path of wrist motion was described relative to the sagittal plane. Forearm rotation and radioscaphoid and radiolunate motion were computed as a function of wrist position.

RESULTS

All volunteers performed the simulated hammering task using a path of wrist motion from radial extension to ulnar flexion that was oriented an average of 41 degrees +/- 3 degrees from the sagittal plane. These paths did not pass through the anatomic neutral wrist position; rather, they passed through a neutral hammering position, which was offset by 36 degrees +/- 8 degrees in extension. Rotations of the scaphoid and lunate were not minimal but averaged 40% and 41%, respectively, of total wrist motion. The range of forearm pronation-supination during the task averaged 12 degrees +/- 8 degrees .

CONCLUSIONS

The simulated hammering task was performed using a wrist motion that followed a coupled path of motion, from extension and radial deviation to flexion and ulnar deviation. Scaphoid and lunate rotations were greatly reduced, but not minimized, compared with rotations during pure wrist flexion/extension. This is likely because an extended wrist position was maintained throughout the entire task studied.

Conformational changes in the carpus during finger trap distraction

PURPOSE

Wrist distraction is a common treatment maneuver used clinically for the reduction of distal radial fractures and midcarpal dislocations. Wrist distraction is also required during wrist arthroscopy to access the radiocarpal joint and has been used as a test for scapholunate ligament injury. However, the effect of a distraction load on the normal wrist has not been well studied. The purpose of this study was to measure the three-dimensional conformational changes of the carpal bones in the normal wrist as a result of a static distractive load.

METHODS

Using computed tomography, the dominant wrists of 14 healthy volunteers were scanned at rest and during application of 98 N of distraction. Load was applied using finger traps, and volunteers were encouraged to relax their forearm muscles and to allow distraction of the wrist. The motions of the bones in the wrist were tracked between the unloaded and loaded trial using markerless bone registration. The average displacement vector of each bone relative to the radius was calculated, as were the interbone distances for 20 bone-bone interactions. Joint separation was estimated at the radiocarpal, midcarpal, and carpometacarpal joints in the direction of loading using the radius, lunate, capitate, and third metacarpal.

RESULTS

With loading, the distance between the radius and third metacarpal increased an average of 3.3 mm +/- 3.1 in the direction of loading. This separation was primarily in the axial direction at the radiocarpal (1.0 mm +/- 1.0) and midcarpal (2.0 mm +/- 1.7) joints. There were minimal changes in the transverse direction within the distal row, although the proximal row narrowed by 0.98 mm +/- 0.7. Distraction between the radius and scaphoid (2.5 mm +/- 2.2) was 2.4 times greater than that between the radius and lunate (1.0 mm +/- 1.0).

CONCLUSIONS

Carpal distraction has a significant (p < .01) effect on the conformation of the carpus, especially at the radiocarpal and midcarpal joints. In the normal wrist, external traction causes twice as much distraction at the lunocapitate joint than at the radiolunate joint.

Clinical study of the factors affecting radioulnar deviation of the wrist joint

Background

The radioulnar carpal joint is critical for hand and wrist function. Radioulnar deviation indicates distal radioulnar joint flexibility and reflects the structure and function of the carpal bones, ulna, radius and ligaments. The present study examined whether radioulnar deviation is affected by gender, manual labor, playing a musical instrument, playing sport, handedness, previous fracture or prior inflammation. The study used clinical findings based on anatomical landmarks

Methods

The ulnar, radial and total deviations for both left and right hands were measured in 300 subjects (157 men and 143 women) of mean age 21.7 years. Measurements were made with the forearm in a fixed pronated position using a novel specially designed goniometer. The gender of each subject was recorded, and information on playing of sport, playing a musical instrument, manual labor, handedness, and history of fracture or inflammation was sought. Data were analyzed using a multifactor ANOVA test.

Results

No statistically significant difference (p-value > 0.05) was found between those comparing groups except the total deviation of athletes' left hand versus the total deviation of non athletes' left hand (p-value 0.041 < 0.05) and the radial deviation of manual workers' left hand and non manual workers' left hand (p-value 0.002 < 0.05).

Conclusions

This study was based on clinical findings using anatomical landmarks. We found that manual workers and athletes showed greater left hand flexibility. This suggests that activities that place chronic stress on the radiocarpal joint can independently affect radioulnar deviation.

The advantage of throwing the first stone: how understanding the evolutionary demands of Homo sapiens is helping us understand carpal motion

Unlike any other diarthrodial joint in the human body, the "wrist joint" is composed of numerous articulations between eight carpal bones, the distal radius, the distal ulna, and five metacarpal bones. The carpal bones articulate with each other as well as with the distal radius, distal ulna, and the metacarpal bases. Multiple theories explaining intercarpal motion have been proposed; however, controversy exists concerning the degree and direction of motion of the individual carpal bones within the two carpal rows during different planes of motion. Recent investigations have suggested that traditional explanations of carpal bone motion may not entirely account for carpal motion in all planes. Better understanding of the complexities of carpal motion through the use of advanced imaging techniques and simultaneous appreciation of human anatomic and functional evolution have led to the hypothesis that the "dart thrower's motion" of the wrist is uniquely human. Carpal kinematic research and current developments in both orthopaedic surgery and anthropology underscore the importance of the dart thrower's motion in human functional activities and the clinical implications of these concepts for orthopaedic surgery and rehabilitation.

The non-dissociative clunking wrist: a personal view

Clunking of the wrist is often the result of a combined radiocarpal and midcarpal ligament insufficiency, coupled with inadequate neuromuscular coordination. When symptomatic, these wrists may benefit from splinting, isometric exercising of specific muscles and advice on activity modification. Failing this, different surgical strategies have been proposed, depending on the location of dysfunction. When the clunking derives from an isolated injury of one joint, reconstruction of its inadequate ligaments may be an effective solution. However, soft tissue procedures tend to fail when clunking results from multilevel instability. In these cases, partial carpal arthrodesis is an alternative. Although effective in eliminating the clunking, midcarpal fusion is associated with alteration of the so-called "dart-throwing" motion, the most common rotation in daily activities, and hence is not recommended. Radiolunate fusion, by contrast, appears to be a less morbid alternative, with the benefit of eliminating the painful clunking while preserving a good range of dart-throwing motion.

Gender differences in capitate kinematics are eliminated after accounting for variation in carpal size

Previous studies have found gender differences in carpal kinematics, and there are discrepancies in the literature on the location of the flexionextension and radio-ulnar deviation rotation axes of the wrist. It has been postulated that these differences are due to carpal bone size differences rather than gender and that they may be resolved by normalizing the kinematics by carpal size. The purpose of this study was to determine if differences in radio-capitate kinematics are a function of size or gender. We also sought to determine if a best-fit pivot point (PvP) describes the radio-capitate joint as a ball-and-socket articulation. By using an in vivo markerless bone registration technique applied to computed tomography scans of 26 male and 28 female wrists, we applied scaling derived from capitate length to radio-capitate kinematics, characterized by a best-fit PvP. We determined if radio-capitate kinematics behave as a ball-and-socket articulation by examining the error in the best-fit PvP. Scaling PvP location completely removed gender differences (P=0.3). This verifies that differences in radio-capitate kinematics are due to size and not gender. The radio-capitate joint did not behave as a perfect ball and socket because helical axes representing anatomical motions such as flexion-extension, radio-ulnar deviation, dart throwers, and antidart throwers, were located at distances up to 4.5 mm from the PvP. Although the best-fit PvP did not yield a single center of rotation, it was still consistently found within the proximal pole of the capitate, and rms errors of the best-fit PvP calculation were on the order of 2 mm. Therefore, the ball-and-socket model of the wrist joint center using the best-fit PvP is appropriate when considering gross motion of the hand with respect to the forearm such as in optical motion capture models. However, the ball-and-socket model of the wrist is an insufficient description of the complex motion of the capitate with respect to the radius. These findings may aid in the design of wrist external fixation and orthotics.

Simulated radioscapholunate fusion alters carpal kinematics while preserving dart-thrower's motion

PURPOSE

Midcarpal degeneration is well documented after radioscapholunate fusion. This study tested the hypothesis that radioscapholunate fusion alters the kinematic behavior of the remaining lunotriquetral and midcarpal joints, with specific focus on the dart-thrower's motion.

METHODS

Simulated radioscapholunate fusions were performed on 6 cadaveric wrists in an anatomically neutral posture. Two 0.060-in. carbon fiber pins were placed from proximal to distal across the radiolunate and radioscaphoid joints, respectively. The wrists were passively positioned in a custom jig toward a full range of motion along the orthogonal axes as well as oblique motions, with additional intermediate positions along the dart-thrower's path. Using a computed tomography-based markerless bone registration technique, each carpal bone's three-dimensional rotation was defined as a function of wrist flexion/extension from the pinned neutral position. Kinematic data was analyzed against data collected on the same wrist prior to fixation using hierarchical linear regression analysis and paired Student's t-tests.

RESULTS

After simulated fusion, wrist motion was restricted to an average flexion-extension arc of 48 degrees , reduced from 77 degrees , and radial-ulnar deviation arc of 19 degrees , reduced from 33 degrees . The remaining motion was maximally preserved along the dart-thrower's path from radial-extension toward ulnar-flexion. The simulated fusion significantly increased rotation through the scaphotrapezial joint, scaphocapitate joint, triquetrohamate joint, and lunotriquetral joint. For example, in the pinned wrist, the rotation of the hamate relative to the triquetrum increased 85%. Therefore, during every 10 degrees of total wrist motion, the hamate rotated an average of nearly 8 degrees relative to the triquetrum after pinning versus 4 degrees in the normal state.

CONCLUSIONS

Simulated radioscapholunate fusion altered midcarpal and lunotriquetral kinematics. The increased rotations across these remaining joints provide one potential explanation for midcarpal degeneration after radioscapholunate fusion. Additionally, this fusion model confirms the dart-thrower's hypothesis, as wrist motion after simulated radioscapholunate fusion was primarily preserved from radial-extension toward ulnar-flexion.

Motion analysis of the wrist joints in patients with rheumatoid arthritis

We investigated the characteristics of the wrist joint motion in patients with rheumatoid arthritis (RA), using a biaxial flexible goniometer. Wrist joint range of motion and velocity were measured on the dominant hand in RA patients (n = 22) and normal individuals (n = 5). We investigated flexion-extension (FE) task, radial-ulnar deviation (RUD) task, and functional motion tasks, such as writing letters or unscrewing the lid of a jar. In normal individuals, there was cooperative coupling of FE and RUD during wrist movement, and this coupling motion was essential for normal wrist movements. On the other hand, in RA patients, wrist joint range of motion was restricted at various degrees, with reduced joint motion velocity that was severe on RUD. Functional wrist motion tasks indicated circumductive movement with both FE and RUD in normal individuals, whereas the direction of movement was limited in RA patients, and results revealed failure of cooperative coupling of FE and RUD. Our results indicate that disturbed coupling of FE and RUD results in difficulties in the cooperative movements and have great influence on the daily activities in RA wrist joint.

Carpal kinematics

The motion of the eight carpal bones is extremely complex, and their accurate measurement has been hampered by their multiplanar rotations and translations, the irregularity of their shape, and the small magnitudes of movements. However, an accurate three-dimensional understanding of carpal motion is critical for academic and clinical purposes, and may play an important role in assessing surgical procedures or rehabilitation protocols.

The dart-throwing motion of the wrist: is it unique to humans?

Kinematic analysis has shown a near-stationary proximal carpal row during the dart-thrower's motion, which is believed to provide a stable platform for the generation of force and accuracy during certain power and precision grip activities. This finding is consistent with evidence in the human hand of adaptations that enabled effective manipulation of stones, cylindric wood, and bone tools for throwing and clubbing. There are at least two possible explanations for the observed human proximal carpal row kinematics. One is that it is retained from a previous common ancestor with great apes and previously adapted to some form of foraging or locomotor behavior involving the hands, but was recruited for tool use after we diverged from the apes. The second is that it evolved after our divergence from apes, in synchrony with adaptations in the human hand to the manipulation of tools, and central to the development of the human's unique ability to aim and accelerate tools and weapons.

Changes in patterns of scaphoid and lunate motion during functional arcs of wrist motion induced by ligament division

PURPOSE

To determine the in vitro motion of the scaphoid and lunate during wrist circumduction and wrist dart-throw motions and to see how these motions change after the ligamentous stabilizers of the scaphoid and lunate are sectioned in a manner simulating scapholunate instability.

METHODS

Twenty-one fresh-frozen cadaver forearms were moved through a dart-throw motion and a circumduction motion using a wrist joint simulator. Scaphoid and lunate motion were measured with the wrist ligaments intact and after sectioning of the scapholunate interosseous ligament, the scaphotrapezium ligament, and the radioscaphocapitate ligament.

RESULTS

In the intact wrist the scaphoid and lunate moved more during circumduction than during the dart-throw motion. With ligamentous sectioning the scaphoid flexed more and the lunate extended more during both the circumduction and dart-throw motions. During the circumduction motion both before and after sectioning the global motion of the scaphoid was greater than that of the lunate. After sectioning the scaphoid motion increased and the lunate motion decreased.

CONCLUSIONS

The scaphoid and lunate motions were observed to change remarkably after ligamentous sectioning. The observed changes in carpal motion correlate with the clinical observation that after ligamentous injury arthritic changes occur in the radioscaphoid joint and not in the radiolunate joint. Analysis of the injured wrist in positions that combine flexion-extension and radial-ulnar deviation may allow noninvasive diagnosis of specific wrist ligament injuries.

In vivo three-dimensional wrist motion analysis using magnetic resonance imaging and volume-based registration

This study represents a new attempt to non-invasively analyze three-dimensional motions of the wrist in vivo. A volume-based registration method using magnetic resonance imaging (MRI) was developed to avoid radiation exposure. The primary aim was to evaluate the accuracy of volume-based registration and compare it with surface-based registration. The secondary aim was to evaluate contributions of the scaphoid and lunate to global wrist motion during flexion-extension motion (FEM), radio-ulnar deviation (RUD) and radial-extension/ulnoflexion, "dart-throwing" motion (DTM) in the right wrists of 12 healthy volunteers. Volume-based registration displayed a mean rotation error of 1.29 degrees +/-1.03 degrees and a mean translation error of 0.21+/-0.25 mm and was significantly more accurate than surface-based registration in rotation. Different patterns of contribution of the scaphoid and lunate were identified for FEM, RUD, and DTM. The scaphoid contributes predominantly in the radiocarpal joint during FEM, in the midcarpal joint during RUD and almost equally between these joints during DTM. The lunate contributes almost equally in both joints during FEM and predominantly in the midcarpal joint during RUD and DTM.

Coupling between wrist flexion-extension and radial-ulnar deviation

BACKGROUND

Conventional wrist joint goniometry evaluates range of motion in isolated directions. The coupling between wrist flexion-extension and radial-ulnar deviation was investigated.

METHODS

Ten healthy young male subjects performed wrist flexion-extension, radial-ulnar deviation, and circumduction motions. Flexion-extension and radial-ulnar deviation angles were computed from the coordinates of surface markers attached to the forearm and hand. A motion analysis system recorded marker motion.

FINDINGS

During radial-ulnar deviation, the amount of accompanying flexion-extension movement was linearly related to the amount of radial-ulnar deviation. The secondary (flexion-extension) range of motion (48.3 degrees) was about 75% of the primary (radial-ulnar deviation) range of motion (55.1 degrees). During the flexion-extension task, the coupling was less linear. The motion range in radial-ulnar deviation (21.2 degrees) was about 20% of the primary (flexion-extension) range of motion (108.3 degrees). The radial-ulnar deviation and flexion-extension motions combined extension with radial deviation, and flexion with ulnar deviation. The convex hull of the flexion-extension and radial-ulnar deviation angles during circumduction was "egg-shaped" and asymmetric with respect to the anatomically defined flexion-extension and radial-ulnar deviation axes. Wrist position in one direction strongly influenced the range of motion in the other. Maximum range of motion in flexion-extension occurred with the wrist near the neutral radial-ulnar deviation position, and vice versa. Wrist deviation from neutral position in one direction diminished wrist range of motion in the other.

INTERPRETATION

Wrist movements in flexion-extension and radial-ulnar deviation are coupled. Maximal wrist range of motion is near the neutral position. To account for the naturally coupled wrist motion in work station design and rehabilitation, the wrist should be placed at a neutral position.