Radial-ulnar Deviation Research Articles

Control of redundant pointing movements involving the wrist and forearm.

The musculoskeletal system can move in more ways than are strictly necessary, allowing many tasks to be accomplished with a variety of limb configurations. Why some configurations are preferred has been a focus of motor control research, but most studies have focused on shoulder-elbow or whole arm movements. This study focuses on movements involving forearm pronation-supination (PS), wrist flexion-extension (FE), and wrist radial-ulnar deviation (RUD) and elucidates how these three degrees of freedom (DOF) combine to perform the common task of pointing, which only requires two DOF. Although pointing is more sensitive to FE and RUD than to PS and could be easily accomplished with FE and RUD alone, subjects tend to involve a small amount of PS. However, why we choose this behavior has been unknown and is the focus of this paper. With the use of a second-order model with lumped parameters, we tested a number of plausible control strategies involving minimization of work, potential energy, torque, and path length. None of these control schemes robustly predicted the observed behavior. However, an alternative control scheme, hypothesized to control the DOF that were most important to the task (FE and RUD) and ignore the less important DOF (PS), matched the observed behavior well. In particular, the behavior observed in PS appears to be a mechanical side effect caused by unopposed interaction torques. We conclude that moderately sized pointing movements involving the wrist and forearm are controlled by ignoring forearm rotation even though this strategy does not robustly minimize work, potential energy, torque, or path length. NEW & NOTEWORTHY Many activities require us to point our hands in a given direction using wrist and forearm rotations. Although there are infinitely many ways to do this, we tend to follow a stereotyped pattern. Why we choose this pattern has been unknown and is the focus of this paper. After testing a variety of hypotheses, we conclude that the pattern results from a simplifying strategy in which we focus on wrist rotations and ignore forearm rotation.

Clinical measurement of the dart throwing motion of the wrist: variability, accuracy and correction.

Despite being functionally important, the dart throwing motion is difficult to assess accurately through goniometry. The objectives of this study were to describe a method for reliably quantifying the dart throwing motion using goniometric measurements within a healthy population. Wrist kinematics of 24 healthy participants were assessed using goniometry and optical motion tracking. Three wrist angles were measured at the starting and ending points of the motion: flexion–extension, radial–ulnar deviation and dart throwing motion angle. The orientation of the dart throwing motion plane relative to the flexion–extension axis ranged between 28° and 57° among the tested population. Plane orientations derived from optical motion capture differed from those calculated through goniometry by 25°. An equation to correct the estimation of the plane from goniometry measurements was derived. This was applied and differences in the orientation of the plane were reduced to non-significant levels, enabling the dart throwing motion to be measured using goniometry alone.

Divide-and-conquer muscle synergies: A new feature space decomposition approach for simultaneous multifunction myoelectric control

Abstract Simultaneous multifunctional control based on surface electromyography (sEMG) is a key issue for natural and intuitive use of upper-limb prostheses in clinical and commercial applications. However, muscle synergies make simultaneous multifunctional control technologically challenging. In this study, we proposed a new feature space decomposition approach to alleviate the difficulty brought by muscle synergies for simultaneous control of hand and wrist movements. In the feature space decomposition approach, Gaussian mixture modeling (GMM) clustering is used to split the whole feature space into a set of Gaussian clusters, each consisting of samples with similar characteristics, to “divide-and-conquer” the complex muscle synergies. Then, a hybrid simultaneous control strategy, which consists of switch control of hand movements and proportional control of wrist movements, is performed in each cluster, instead of in the whole feature space. In the experimental study, sEMG signals were recorded during static and dynamic muscle contraction involving 2-dimensional wrist rotation (flexion-extension and radial-ulnar deviation) and 3 basic hand movement patterns (relaxing, fisting and grasping). Results show that, the new feature space decomposition approach can increase the accuracy for switch control of hand movement patterns from 90.10% to 96.62%, and can improve the correlation between true and predicted values of wrist rotation angular velocity from 0.71 to 0.84 (for wrist flexion-extension) and from 0.67 to 0.82 (for wrist radial-ulnar deviation) for proportional control of wrist. The proposed feature space decomposition approach has the potential to yield simultaneous multifunctional control for sEMG-based upper-limb prosthesis.

FUNCTIONAL AND KINEMATIC ANALYSIS OF A WRIST RADIAL HEMIARTHROPLASTY DESIGN

Purpose: A biomechanical functional assessment was performed on a newly designed wrist hemiarthroplasty implant with aimed to identifying differences between the native wrist and wrist following the hemiarthroplasty procedure with [Formula: see text] and without a proximal row carpectomy (Hemi). Methods: Six cadaveric wrists were mounted on a custom testing fixture and underwent a series of functional tests to investigate differences in range of motion, muscles moment arms, and axis of rotation between the intact and post-operative wrists. The tested movements included manually-driven flexion-extension, radial-ulnar deviation, dart throwers motion, and circumduction. Results: The only significant change in range of motion was a decrease in flexion between the intact [Formula: see text] and both the Hemi [Formula: see text] and [Formula: see text] [Formula: see text] conditions. Minor differences in the mean position and variability of the axis of rotation’s piercing point were identified. A statistically significant decrease in the flexion moment arm of the flexor carpi radialis was identified between the intact ([Formula: see text][Formula: see text]mm) and [Formula: see text] ([Formula: see text][Formula: see text]mm) conditions. Statistically significant decreases were also identified in the radial deviation moment arms of the extensor carpi radialis brevis’ between the intact ([Formula: see text][Formula: see text]mm) and [Formula: see text] ([Formula: see text][Formula: see text]mm) conditions and the flexor carpi radialis’ between the intact ([Formula: see text][Formula: see text]mm) and Hemi ([Formula: see text][Formula: see text]mm) conditions as well as in the ulnar deviation moment arm of the extensor carpi ulnaris between the intact ([Formula: see text][Formula: see text]mm) and Hemi ([Formula: see text][Formula: see text]mm) conditions. Conclusions: While some statistically significant functional changes were identified between the native and hemiarthroplasty wrist, the findings suggest that post-operative function is equally acceptable in hemiarthroplasty with and without resection of the proximal carpal row.

Distal Scaphoid Excision in Treatment of Symptomatic Scaphoid Nonunion: Systematic Review and Meta-analysis.

Background: Current treatment options for persistent scaphoid nonunion are limited to salvage procedures such as proximal row carpectomy (PRC) or 4-corner fusion (4CF). Several small studies have demonstrated that distal scaphoid excision may provide a simpler alternative with faster recovery. The purpose of this study was to determine the efficacy of distal scaphoid excision as a treatment option for symptomatic scaphoid nonunion. Methods: The MEDLINE and PubMed databases were searched for the use of distal scaphoid excision in scaphoid nonunions. Studies included reported on either the functional or patient-centered outcomes following distal scaphoid excision for symptomatic scaphoid nonunion. Results: Six articles described the outcomes of 70 patients with an average of 11.7 patients per study. Functional outcomes including flexion-extension arc, radial-ulnar deviation, and grip strength improved by an average of 98.95%, 58.96%, and 131.08%, respectively. Patient-derived outcomes included the Modified Mayo Wrist Score, which improved by 92.6%, and the Disabilities of the Arm, Shoulder and Hand, which improved by 137.17%. An average of 68.75% of patients experience complete relief of pain with 20.83% of patients experiencing pain with strenuous activity. The average postoperative visual analog scale (0-10) was 0.71. On average, 93.33% of patients returned to work with an average time of return being 6.89 weeks. Complete satisfaction was reported by 87.80% of patients. Complications included progression into 4CF or PRC and newly developed midcarpal arthritis. Conclusions: Given favorable outcomes, our analysis suggests that distal scaphoid excision may be a favorable, low-risk treatment for scaphoid nonunion without eliminating more extensive options such as 4CF and wrist arthrodesis.

Does Wrist Laxity Influence Three-Dimensional Carpal Bone Motion?

Previous two-dimensional (2D) studies have shown that there is a spectrum of carpal mechanics that varies between row-type motion and column-type motion as a function of wrist laxity. More recent three-dimensional (3D) studies have suggested instead that carpal bone motion is consistent across individuals. The purpose of this study was to use 3D methods to determine whether carpal kinematics differ between stiffer wrists and wrists with higher laxity. Wrist laxity was quantified using a goniometer in ten subjects by measuring passive wrist flexion-extension (FE) range of motion (ROM). In vivo kinematics of subjects' scaphoid and lunate with respect to the radius were computed from computed tomography (CT) volume images in wrist radial and ulnar deviation positions. Scaphoid and lunate motion was defined as "column-type" if the bones flexed and extended during wrist radial-ulnar deviation (RUD), and "row-type" if the bones radial-ulnar deviated during wrist RUD. We found that through wrist RUD, the scaphoid primarily flexed and extended, but the scaphoids of subjects with decreased laxity had a larger component of RUD (R2 = 0.48, P < 0.05). We also determined that the posture of the scaphoid in the neutral wrist position predicts wrist radial deviation (RD) ROM (R2 = 0.46, P < 0.05). These results suggest that ligament laxity plays a role in affecting carpal bone motion of the proximal row throughout radial and ulnar deviation motions; however, other factors such as bone position may also affect motion. By developing a better understanding of normal carpal kinematics and how they are affected, this will help physicians provide patient-specific approaches to different wrist pathologies.

Exosomes secreted by mice adipose-derived stem cells after low-level laser irradiation treatment reduce apoptosis of osteocyte induced by hypoxia.

Kienböck's disease is a commonly seen posttraumatic avascular necrosis characterized by avascular necrosis of the lunate bone of the wrist which involves the dominant hand. In our study, we aimed to present midterm outcomes of 12 cases treated with radial metaphyseal core decompression. In our clinic, 12 patients who applied to our outpatient clinic with intractable pain despite at least six weeks of conservative treatment were previously diagnosed and evaluated as Kienböck's disease between the years 2006 and 2014. Patients at early stage received radial metaphyseal core decompression. The patients were evaluated as postoperative grip strength, flexion-extension gap, ulnar-radial deviation gap, VAS, Quick DASH and MAYO wrist scoring and patient satisfaction. We determined that interventions performed for Kienböck's disease cannot halt radiological progression. We are of the opinion that radial metaphyseal core decompression, aiming at increasing blood perfusion, improve early diagnosis and treatment of Kienböck's disease, increasing the patient satisfaction.

Mid term results of radial metaphyseal core decompression on Kienböck's disease.

Kienböck's disease is a commonly seen posttraumatic avascular necrosis characterized by avascular necrosis of the lunate bone of the wrist which involves the dominant hand. In our study, we aimed to present midterm outcomes of 12 cases treated with radial metaphyseal core decompression. In our clinic, 12 patients who applied to our outpatient clinic with intractable pain despite at least six weeks of conservative treatment were previously diagnosed and evaluated as Kienböck's disease between the years 2006 and 2014. Patients at early stage received radial metaphyseal core decompression. The patients were evaluated as postoperative grip strength, flexion-extension gap, ulnar-radial deviation gap, VAS, Quick DASH and MAYO wrist scoring and patient satisfaction. We determined that interventions performed for Kienböck's disease cannot halt radiological progression. We are of the opinion that radial metaphyseal core decompression, aiming at increasing blood perfusion, improve early diagnosis and treatment of Kienböck's disease, increasing the patient satisfaction.

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

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

Biomechanics of an Articulated Screw in Acute Scapholunate Ligament Disruption.

Background An injury to the scapholunate interosseous ligament (SLIL) leads to instability in the scapholunate joint. Temporary fixation is used to protect the ligament during reconstruction or healing of the repair. Rigid screw fixation-by blocking relative physiological motion between the scaphoid and lunate-can lead to screw loosening, pullout, and fracture. Purpose This study aims to evaluate changes in scaphoid and lunate kinematics following SLIL injury and the effectiveness of an articulating screw at restoring preinjury motion. Materials and Methods The kinematics of the scaphoid and lunate were measured in 10 cadaver wrists through three motions driven by a motion simulator. The specimens were tested intact, immediately following SLIL injury, after subsequent cycling, and after fixation with a screw. Results Significant changes in scaphoid and lunate motion occurred following SLIL injury. Postinjury cycling increased motion changes in flexion-extension and radial-ulnar deviation. The motion was not significantly different from the intact scapholunate joint after placement of the articulating screw. Conclusion In agreement with other studies, sectioning of the SLIL led to significant kinematic changes of the scaphoid and lunate in all motions tested. Compared with intact scapholunate joint, no significant difference in kinematics was found after placement of the screw indicating a correction of some of the changes produced by SLIL transection. These findings suggest that the articulating screw may be effective for protecting a SLIL repair while allowing the physiological rotation to occur between the scaphoid and lunate. Clinical Relevance A less rigid construct, such as the articulating screw, may allow earlier wrist rehabilitation with less screw pullout or failure.

Four-Year Outcomes of Midcarpal Hemiarthroplasty for Wrist Arthritis

The purpose of this study was to review the average 4-year outcomes of a cohort of patients with wrist arthritis, treated by a single surgeon with a novel prosthetic hemiarthroplasty of the midcarpal joint. We hypothesized that midcarpal hemiarthroplasty would improve range of motion and grip strength of patients with wrist arthritis, with a complication profile comparable with that of alternative solutions for wrist arthritis. We reviewed a series of 20 patients treated with a midcarpal hemiarthroplasty at an average of 4 years following surgery. Patients were evaluated objectively with grip strength, wrist range of motion, serial radiographs, and subjectively surveyed with Disabilities of the Arm, Shoulder, and Hand (DASH) and Mayo scores. Range of motion increased by a mean 33° in flexion-extension and 10° in radial-ulnar deviation compared with preoperative range of motion. Mean grip strength improved to 20.8 kg from 14.1 kg, and Mayo and DASH scores also significantly improved. Three patients had a manipulation under anesthesia for stiffness. One patient required open reduction internal fixation of an unstable fourth carpometacarpal joint after falling. Two patients were revised to a total wrist arthroplasty and 1 to a wrist fusion. Midcarpal hemiarthroplasty provides improved wrist range of motion, grip strength, and patient-reported outcome scores compared with preoperative values, with a complication profile comparable with that of other surgical options for patients with wrist arthritis. Advantages of midcarpal arthroplasty include retention of the native distal carpal row, preservation of midcarpal motion, as well as the option for conversion to a total wrist arthroplasty should revision be required. Therapeutic IV.

A musculoskeletal model to estimate the relative changes in wrist strength due to interacting wrist and forearm postures

Wrist rotations about one wrist axis (e.g. flexion/extension) can affect the strength about another wrist axis (e.g. radial/ulnar deviation). This study used a musculoskeletal model of the distal upper extremity, and an optimization approach, to quantify the interaction effects of wrist flexion/extension (FE), radial/ulnar deviation (RUD) and forearm pronation/supination (PS) on wrist strength. Regression equations were developed to predict the relative changes in strength from the neutral posture, so that the changes in strength, due to complex and interacting wrist and forearm rotation postures, can be incorporated within future ergonomics assessments of wrist strength.

Dorsoradial Instability of the Thumb Metacarpophalangeal Joint: A Biomechanical Investigation.

To define the role of the dorsal capsule and associated dorsal fibrocartilage (DFC) and their interactions with the radial collateral ligament (RCL) as a thumb metacarpophalangeal (MCP) joint stabilizer. Eight cadaveric thumbs were mounted onto a custom jig with 20 N of muscle load applied. The thumb position in space was digitized to measure ulnar-radial, pronation-supination, and volar-dorsal laxity at 0°, 30°, and 60° MCP joint flexion. Serial sectioning was performed and measurements were repeated for the intact state, proper RCL insufficiency, proper and accessory (complete) RCL insufficiency, complete RCL with 50% DFC (radial) insufficiency, and complete RCL with complete DFC insufficiency. Ulnar-radial deviation, pronation-supination, and volar-dorsal translation significantly changed at 30° and 60° MCP joint flexion when comparing complete RCL insufficiency with complete RCL with 50% DFC insufficiency. At 30° flexion, significant increases were found in ulnar deviation, pronation, and volar translation, and there was a decrease in supination. At 60° flexion, ulnar deviation, pronation, and volar translation increased and radial deviation decreased significantly. At 30° flexion, the resting position significantly pronated and translated volarly. At 60° flexion, the resting position significantly shifted ulnarly, pronated, and translated volarly. The DFC acts as a secondary stabilizer of the thumb MCP joint, working in tandem with the RCL. It acts by stabilizing the MCP joint dorsoradially when external forces are applied across the joint. This cadaveric study shows that RCL insufficiency with a concomitant DFC injury is less likely to be stable than RCL injuries alone, and that this effect is more pronounced with MCP joint flexion. Increasing incompetence of the secondary stabilizers of the RCL, such as the DFC, will likely result in increased clinical instability upon physical examination. The results of this study also suggest the need to consider repair of the DFC at the time of RCL repair.

Do Impairments Predict Hand Dexterity After Distal Radius Fractures? A 6-Month Prospective Cohort Study.

The relationship of routinely measured grip and motion measures may be related to hand dexterity. This has not yet been thoroughly examined following a distal radius fracture (DRF). The purpose of this study was to investigate if impairments in range of motion (ROM) and grip strength predict hand dexterity 6 months following a DRF. Patients with DRFs were recruited from a specialized hand clinic. Hand grip was assessed with a J-Tech dynamometer; ROM was measured using standard landmarks and a manual goniometer. Multiple regression analyses were performed to identify whether potential predictors (grip, ROM, age, hand dominance, and sex) were associated with 3-month or 6-month outcomes in large- and small-object subtests of the NK dexterity test in the affected hand. Age, sex, and arc motion for radial-ulnar deviation were significant predictors of large-object hand dexterity explaining the 23% of the variation. For small-object hand dexterity, age and flexion-extension arc motion were significant predictors explaining 11% of the variation at 3 month after the fracture (n = 391). At 6 months post injury (n = 319), grip strength, arc motion for flexion-extension, and age were found to be significant predictors of large-object dexterity explaining 34% of the variance. For the small objects, age, grip strength, sex, and arc motion of radial-ulnar deviation explained 25% of the variation. Although this confirms that the impairments in ROM and grip that occur after a DRF can explain almost one-third of the variation in hand dexterity, it also suggests the need for dexterity testing to provide more accurate assessment.

Universal 2 Wrist Arthroplasty in Rheumatoid Arthritis.

Purpose The aim of this study was to evaluate the mid- to long-term outcomes and complications in patients affected by rheumatic diseases treated with the Universal 2 (U2) total wrist arthroplasty (TWA). Methods We reviewed, in a retrospective, noncontrolled cohort study, 22 patients affected by rheumatoid arthritis (RA), who underwent U2 total wrist replacement between March 2003 and January 2014 for the treatment of 23 rheumatoid wrists with the aim of obtaining the remission of pain and a range of motion (ROM) useful for daily activities, according to the patients' demands, as an alternative to total wrist arthrodesis. The cohort of patients included 20 females and 2 males, with a mean age of 54.9 years. Residual pain, preoperative ROM, postoperative ROM increases, grip strength, radiographic changes, long-term complications, and reasons for revision or failures were evaluated. Results In this study, 22 patients were evaluated at a mean follow-up of 82.3 months (range: 2-12 years). All patients had good or complete pain relief, the mean visual analogue scale pain score was 0.82. The mean grip strength improved and postoperatively was 11 kg (Jamar). The mean total ROM of flexion-extension was 72.3 degrees; radial-ulnar deviation 24.9 degrees. The mean QuickDASH score of 49 and patient rate wrist/hand evaluation of 41.7 a revision surgical procedure in six cases (26%): in two cases, a carpal component revision procedure and in four cases, total implant failures requiring either conversion to a Swanson spacer or wrist joint fusion. Conclusion TWA provides pain relief, preserves motion, and improves function in severe degenerative RA. Our results at a mid- to long-term follow-up with the U2 prosthesis were encouraging and represent, when indicated, a valid alternative to fusion which is less appealing for RA patients. Level of Evidence Level of evidence is therapeutic IV.

Proximal-distal differences in movement smoothness reflect differences in biomechanics

Smoothness is a hallmark of healthy movement. Past research indicates that smoothness may be a side product of a control strategy that minimizes error. However, this is not the only reason for smooth movements. Our musculoskeletal system itself contributes to movement smoothness: the mechanical impedance (inertia, damping, and stiffness) of our limbs and joints resists sudden change, resulting in a natural smoothing effect. How the biomechanics and neural control interact to result in an observed level of smoothness is not clear. The purpose of this study is to 1) characterize the smoothness of wrist rotations, 2) compare it with the smoothness of planar shoulder-elbow (reaching) movements, and 3) determine the cause of observed differences in smoothness. Ten healthy subjects performed wrist and reaching movements involving different targets, directions, and speeds. We found wrist movements to be significantly less smooth than reaching movements and to vary in smoothness with movement direction. To identify the causes underlying these observations, we tested a number of hypotheses involving differences in bandwidth, signal-dependent noise, speed, impedance anisotropy, and movement duration. Our simulations revealed that proximal-distal differences in smoothness reflect proximal-distal differences in biomechanics: the greater impedance of the shoulder-elbow filters neural noise more than the wrist. In contrast, differences in signal-dependent noise and speed were not sufficiently large to recreate the observed differences in smoothness. We also found that the variation in wrist movement smoothness with direction appear to be caused by, or at least correlated with, differences in movement duration, not impedance anisotropy.NEW & NOTEWORTHY This article presents the first thorough characterization of the smoothness of wrist rotations (flexion-extension and radial-ulnar deviation) and comparison with the smoothness of reaching (shoulder-elbow) movements. We found wrist rotations to be significantly less smooth than reaching movements and determined that this difference reflects proximal-distal differences in biomechanics: the greater impedance (inertia, damping, stiffness) of the shoulder-elbow filters noise in the command signal more than the impedance of the wrist.

Effect of hammer mass on upper extremity joint moments

This study used an OpenSim inverse-dynamics musculoskeletal model scaled to subject-specific anthropometrics to calculate three-dimensional intersegmental moments at the shoulder, elbow and wrist while 10 subjects used 1 and 2 lb hammers to drive nails. Motion data were collected via an optoelectronic system and the interaction of the hammer with nails was recorded with a force plate. The larger hammer caused substantial increases (50–150%) in moments, although increases differed by joint, anatomical component, and significance of the effect. Moment increases were greater in cocking and strike/follow-through phases as opposed to swinging and may indicate greater potential for injury. Compared to shoulder, absolute increases in peak moments were smaller for elbow and wrist, but there was a trend toward larger relative increases for distal joints. Shoulder rotation, elbow varus-valgus and pronation-supination, and wrist radial-ulnar deviation and rotation demonstrated large relative moment increases. Trial and phase durations were greater for the larger hammer. Changes in moments and timing indicate greater loads on musculoskeletal tissues for an extended period with the larger hammer. Additionally, greater variability in timing with the larger hammer, particularly for cocking phase, suggests differences in control of the motion. Increased relative moments for distal joints may be particularly important for understanding disorders of the elbow and wrist associated with hammer use.

Decoupling the Wrist: A Cadaveric Experiment Examining Wrist Kinematics Following Midcarpal Fusion and Scaphoid Excision.

At the wrist, kinematic coupling (the relationship between flexion-extension and radial-ulnar deviation) facilitates function. Although the midcarpal joint is critical for kinematic coupling, many surgeries, such as 4-corner fusion (4CF) and scaphoidexcision 4-corner fusion (SE4CF), modify the midcarpal joint. This study examines how 4CF and SE4CF influence kinematic coupling by quantifying wrist axes of rotation. Wrist axes of rotation were quantified in 8 cadaveric specimens using an optimization algorithm, which fit a 2-revolute joint model to experimental data. In each specimen, data measuring the motion of the third metacarpal relative to the radius was collected for 3 conditions (nonimpaired, 4CF, SE4CF). The calculated axes of rotation were compared using spherical statistics. The angle between the axes of rotation was used to assess coupling, as the nonimpaired wrist has skew axes (ie, angle between axes approximately 60°). Following 4CF and SE4CF, the axes are closer to orthogonal than those of the nonimpaired wrist. The mean angle (±95% confidence interval) between the axes was 92.6° ± 25.2° and 99.8° ± 22.0° for 4CF and SE4CF, respectively. The axes of rotation defined in this study can be used to define joint models, which will facilitate more accurate computational and experimental studies of these procedures.

Restoration of Pronation and Radial Deviation in “The Beggar’s Hand” Deformity by Switch Technique

Objective/Hypothesis: In this study, our aim is to present our results with the “switch technique” in the dynamic restoration of forearm pronation and wrist radial deviation in patients with “the beggar’s hand” caused by obstetric brachial plexus palsy. In the “switch technique,” the tendons of two functional muscles are sectioned at two different levels, and the proximal muscular units are transposed to the presectioned distal tendon ends in a cross fashion. This technique enables the dynamic restoration of the paralytic and complex deformity. Materials and Methods: Eleven obstetric palsy patients (6 male, 5 female) with ages ranging between 5 and 10 years (mean age of 7.6 years) were operated for the correction of supination deformity and ulnar deviation of the wrist. Soft tissue releases were performed at the forearm and the wrist. Extensor carpi ulnaris (ECU), brachioradialis (BR), abductor pollicis longus (APL), and the flexor carpi ulnaris (FCU) muscles were prepared. The ECU tendon was sectioned and disinserted from its insertion whereas the BR tendon was sectioned just distal to the myotendinous junction. The distal end of the BR tendon was rotated around the radius from the dorsal to the volar, and then, it was advanced proximally along the interosseous membrane after being passed through a pulley that was prepared from the distal end of the FCU tendon. The ECU tendon was advanced from the dorsal to the volar, and it was sutured to the BR tendon as a pronator. The APL tendon was sectioned from a proximal level, and the distal end of this tendon was sutured to the proximal end of the BR tendon as a wrist radial deviator. The mean follow-up time was 14 months (4-31 months). Forearm pronosupination, wrist flexion-extension, and ulnar-radial deviation were assessed by goniometric measurements. Results: Mean active forearm pronation was −42.5° preoperatively. After the surgery, 38.75° degrees of active forearm pronation was achieved. Preoperative and postoperative mean active radial deviation values were −7.5° and 10.75°, respectively. All patients reported that they became more capable in activities such as turning pages and holding a mug. Conclusions: The tendons that are used in the “switch technique” are not paralytic, and they are functional. In fact, this is a major difference with classic tendon transfers. With this technique, the original muscle bellies and the routes of the tendons are switched. They are used for impaired targets, and they are reorganized for the restoration of insufficient functions. Correction of the deformity improves the appearance of the limb and the self-confidence of the child and allows the patients to integrate well into the society. These results suggest that selected cases may benefit from restoration of “the beggar’s hand” deformity with the “switch technique” that may produce a critical improvement in functional capabilities.

Principal components of wrist circumduction from electromagnetic surgical tracking.

An electromagnetic (EM) surgical tracking system was used for a functionally calibrated kinematic analysis of wrist motion. Circumduction motions were tested for differences in subject gender and for differences in the sense of the circumduction as clockwise or counter-clockwise motion. Twenty subjects were instrumented for EM tracking. Flexion-extension motion was used to identify the functional axis. Subjects performed unconstrained wrist circumduction in a clockwise and counter-clockwise sense. Data were decomposed into orthogonal flexion-extension motions and radial-ulnar deviation motions. PCA was used to concisely represent motions. Nonparametric Wilcoxon tests were used to distinguish the groups. Flexion-extension motions were projected onto a direction axis with a root-mean-square error of [Formula: see text]. Using the first three principal components, there was no statistically significant difference in gender (all [Formula: see text]). For motion sense, radial-ulnar deviation distinguished the sense of circumduction in the first principal component ([Formula: see text]) and in the third principal component ([Formula: see text]); flexion-extension distinguished the sense in the second principal component ([Formula: see text]). The clockwise sense of circumduction could be distinguished by a multifactorial combination of components; there were no gender differences in this small population. These data constitute a baseline for normal wrist circumduction. The multifactorial PCA findings suggest that a higher-dimensional method, such as manifold analysis, may be a more concise way of representing circumduction in human joints.