Finger Flexor Activity Research Articles

Peripheral nerve blocks of wrist and finger flexors can increase hand opening in chronic hemiparetic stroke.

Hand opening is reduced by abnormal wrist and finger flexor activity in many individuals with stroke. This flexor activity also limits hand opening produced by functional electrical stimulation (FES) of finger and wrist extensor muscles. Recent advances in electrical nerve block technologies have the potential to mitigate this abnormal flexor behavior, but the actual impact of nerve block on hand opening in stroke has not yet been investigated. In this study, we applied the local anesthetic ropivacaine to the median and ulnar nerve to induce a complete motor block in 9 individuals with stroke and observed the impact of this block on hand opening as measured by hand pentagonal area. Volitional hand opening and FES-driven hand opening were measured, both while the arm was fully supported on a haptic table (Unloaded) and while lifting against gravity (Loaded). Linear mixed effect regression (LMER) modeling was used to determine the effect of Block. The ropivacaine block allowed increased hand opening, both volitional and FES-driven, and for both unloaded and loaded conditions. Notably, only the FES-driven and Loaded condition's improvement in hand opening with the block was statistically significant. Hand opening in the FES and Loaded condition improved following nerve block by nearly 20%. Our results suggest that many individuals with stroke would see improved hand-opening with wrist and finger flexor activity curtailed by nerve block, especially when FES is used to drive the typically paretic finger and wrist extensor muscles. Such a nerve block (potentially produced by aforementioned emerging electrical nerve block technologies) could thus significantly address prior observed shortcomings of FES interventions for individuals with stroke.

An investigation of tendon strains in jersey finger injury load cases using a finite element neuromuscular human body model.

Introduction: A common hand injury in American football, rugby and basketball is the so-called jersey finger injury (JFI), in which an eccentric overextension of the distal interphalangeal joint leads to an avulsion of the connected musculus flexor digitorum profundus (FDP) tendon. In the field of automotive safety assessment, finite element (FE) neuromuscular human body models (NHBMs) have been validated and are employed to evaluate different injury types related to car crash scenarios. The goal of this study is to show, how such a model can be modified to assess JFIs by adapting the hand of an FE-NHBM for the computational analysis of tendon strains during a generalized JFI load case. Methods: A jersey finger injury criterion (JFIC) covering the injury mechanisms of tendon straining and avulsion was defined based on biomechanical experiments found in the literature. The hand of the Total Human Model for Safety (THUMS) version 3.0 was combined with the musculature of THUMS version 5.03 to create a model with appropriate finger mobility. Muscle routing paths of FDP and musculus flexor digitorum superficialis (FDS) as well as tendon material parameters were optimized using literature data. A simplified JFI load case was simulated as the gripping of a cylindrical rod with finger flexor activation levels between 0% and 100%, which was then retracted with the velocity of a sprinting college football player to forcefully open the closed hand. Results: The optimization of the muscle routing node positions and tendon material parameters yielded good results with minimum normalized mean absolute error values of 0.79% and 7.16% respectively. Tendon avulsion injuries were detected in the middle and little finger for muscle activation levels of 80% and above, while no tendon or muscle strain injuries of any kind occurred. Discussion: The presented work outlines the steps necessary to adapt the hand model of a FE-NHBM for the assessment of JFIs using a newly defined injury criterion called the JFIC. The injury assessment results are in good agreement with documented JFI symptoms. At the same time, the need to rethink commonly asserted paradigms concerning the choice of muscle material parameters is highlighted.

Teaching Video NeuroImages: Acquired focal neuromyotonia in LGI-1 autoimmunity

An 81-year-old woman was diagnosed with corticobasal degeneration (cognitive decline and left hand posturing). Hyponatremia and bilateral faciobrachial dystonic seizures (FBDS) ensued. Neurologic examination (figure, A; video) revealed persistent involuntary continuous left 3rd and 4th finger flexor activation and delayed relaxation. EMG revealed high-frequency spontaneous discharges, including neuromyotonia and fast myokymia of the left flexor digitorum superficialis and pronator teres (figure, B). LGI1 immunoglobulin G (IgG)1 was detected, but not CASPR2-IgG (figure, C–E). Oncologic evaluation revealed breast ductal carcinoma in situ. Encephalopathy and FBDS resolved after IV immunoglobulin. Encephalopathy coexisting with peripheral nerve hyperexcitability can mimic neurodegeneration, and should prompt exclusion of LGI1/CASPR2 autoimmunity.2

Kinematic and dynamic aspects of chimpanzee knuckle walking: finger flexors likely do not buffer ground impact forces.

Chimpanzees are knuckle walkers, with forelimbs contacting the ground by the dorsum of the finger's middle phalanges. As these muscular apes are given to high-velocity motions, the question arises of how the ground reaction forces are buffered so that no damage ensues in the load-bearing fingers. In the literature, it was hypothesized that the finger flexors help buffer impacts because in knuckle stance the metacarpophalangeal joints (MCPJs) are strongly hyperextended, which would elongate the finger flexors. This stretching of the finger flexor muscle-tendon units would absorb impact energy. However, EMG studies did not report significant finger flexor activity in knuckle walking. Although these data by themselves question the finger flexor impact buffering hypothesis, the present study aimed to critically investigate the hypothesis from a biomechanical point of view. Therefore, various aspects of knuckle walking were modeled and the finger flexor tendon displacements in the load-bearing fingers were measured in a chimpanzee cadaver hand, of which also an MRI was taken in knuckle stance. The biomechanics do not support the finger flexor impact buffering hypothesis. In knuckle walking, the finger flexors are not elongated to lengths where passive strain forces would become important. Impact buffering by large flexion moments at the MCPJs from active finger flexors would result in impacts at the knuckles themselves, which is dysfunctional for various biomechanical reasons and does not occur in real knuckle walking. In conclusion, the current biomechanical analysis in accumulation of previous EMG findings suggests that finger flexors play no role in impact buffering in knuckle walking.

25487 Timing and strength of hand grasp that are affected by abnormal coupling between arm muscles following stroke: A pilot study

ABSTRACT IMPACT: Impaired neuromuscular control could lead to the failure in activation and deactivation of the target muscles in a timely manner, with the concurrence of activities of non-targeted muscles. OBJECTIVES/GOALS: Stroke leads to impaired capacity to manipulate objects with the hand in terms of timing and strength of grasp. The influence of abnormal coupling across more proximal arm muscles post stroke on the failure in normal functioning of finger flexor muscle activity is of interest to investigate. METHODS/STUDY POPULATION: We have recruited 12 participants with stroke hemiparesis in the sub-acute or chronic stage. Motor impairment of the arm was assessed using electromyography (EMG) and the Fugl-Meyer Upper Extremity (FMUE) assessment. Participants were requested to flex and relax the metacarpophalangeal (MCP) joints against motorized resistance in response to audible tones to determine timing and strength during flexion. They were asked to flex maximally, as quickly as possible, in response to the first of a pair of tones, and relax as quickly as possible after the second tone. Delays in initiation and termination were evaluated using EMG responses versus a predefined threshold. RESULTS/ANTICIPATED RESULTS: We anticipate greater delays in grasp initiation as well as in grasp termination in participants with a greater extent of abnormal coupling across more proximal muscles of the upper extremity in comparison to participants with a less extent, using the results of the FMUE assessment. Also it is expected that participants with a greater extent of the flexion synergy produce a less extent of force generation. The EMG results will show that activities of more proximal arm muscles precede the initiation of MCP flexion and their activity termination precedes that of MCP flexion, significantly more in participants with a greater extent of the flexion synergy. DISCUSSION/SIGNIFICANCE OF FINDINGS: The flexion synergy over the arm following stroke affects the timing and strength of hand grasp. Impaired neuromuscular control could lead to the failure in activation and deactivation of the target muscles in a timely manner, with the concurrence of activities of non-targeted muscles.

Neuromodulatory Inputs to Motoneurons Contribute to the Loss of Independent Joint Control in Chronic Moderate to Severe Hemiparetic Stroke.

In chronic hemiparetic stroke, increased shoulder abductor activity causes involuntary increases in elbow, wrist, and finger flexor activation, an abnormal muscle coactivation pattern known as the flexion synergy. Recent evidence suggests that flexion synergy expression may reflect recruitment of contralesional cortico-reticulospinal motor pathways following damage to the ipsilesional corticospinal tract. However, because reticulospinal motor pathways produce relatively weak post-synaptic potentials in motoneurons, it is unknown how preferential use of these pathways could lead to robust muscle activation. Here, we hypothesize that the descending neuromodulatory component of the ponto-medullary reticular formation, which uses the monoaminergic neurotransmitters norepinephrine and serotonin, serves as a gain control mechanism to facilitate motoneuron responses to reticulospinal motor commands. Thus, inhibition of the neuromodulatory component would reduce flexion synergy expression by disfacilitating spinal motoneurons. To test this hypothesis, we conducted a pre-clinical study utilizing two targeted neuropharmacological probes and inert placebo in a cohort of 16 individuals with chronic hemiparetic stroke. Test compounds included Tizanidine (TIZ), a noradrenergic α2 agonist and imidazoline ligand selected for its ability to reduce descending noradrenergic drive, and Isradipine, a dihyropyridine calcium-channel antagonist selected for its ability to post-synaptically mitigate a portion of the excitatory effects of monoamines on motoneurons. We used a previously validated robotic measure to quantify flexion synergy expression. We found that Tizanidine significantly reduced expression of the flexion synergy. A predominantly spinal action for this effect is unlikely because Tizanidine is an agonist acting on a baseline of spinal noradrenergic drive that is likely to be pathologically enhanced post-stroke due to increased reliance on cortico-reticulospinal motor pathways. Although spinal actions of TIZ cannot be excluded, particularly from Group II pathways, our finding is consistent with a supraspinal action of Tizanidine to reduce descending noradrenergic drive and disfacilitate motoneurons. The effects of Isradipine were not different from placebo, likely related to poor central bioavailability. These results support the hypothesis that the descending monoaminergic component of the ponto-medullary reticular formation plays a key role in flexion synergy expression in chronic hemiparetic stroke. These results may provide the basis for new therapeutic strategies to complement physical rehabilitation.

Medial Elbow Joint Space Increases With Valgus Stress and Decreases When Cued to Perform A Maximal Grip Contraction

Background: Previous research indicates that the amount of valgus torque placed on the elbow joint during overhead throwing is higher than the medial ulnar collateral ligament (UCL) can tolerate. Wrist and finger flexor muscle activity is hypothesized to make up for this difference, and in vitro studies that simulated activity of upper extremity musculature, specifically the flexor digitorum superficialis and flexor carpi ulnaris, support this hypothesis. Purpose: To assess the medial elbow joint space at rest, under valgus stress, and under valgus stress with finger and forearm flexor contraction by use of ultrasonography in vivo. Study Design: Controlled laboratory study. Methods: Participants were 22 healthy males with no history of elbow dislocation or UCL injury (age, 21.25 ± 1.58 years; height, 1.80 ± 0.08 m; weight, 79.43 ± 18.50 kg). Medial elbow joint space was measured by use of ultrasonography during 3 separate conditions: at rest (unloaded), under valgus load (loaded), and with a maximal grip contraction under a valgus load (loaded-contracted) in both limbs. Participants lay supine with their arm abducted 90° and elbow flexed 30° with the forearm in full supination. A handgrip dynamometer was placed in the participants’ hand to grip against during the contracted condition. Images were reduced in ImageJ to assess medial elbow joint space. A 2-way (condition × limb) repeated-measures analysis of variance and Cohen’s d effect sizes were used to assess changes in medial elbow joint space. Post hoc testing was performed with a Bonferroni adjustment to assess changes within limb and condition. Results: The medial elbow joint space was significantly larger in the loaded condition (4.91 ± 1.16 mm) compared with the unloaded condition (4.26 ± 1.23 mm, P < .001, d = 0.712) and the loaded-contracted condition (3.88 ± 0.94 mm, P < .001, d = 1.149). No significant change was found between the unloaded and loaded-contracted conditions (P = .137). Conclusion: Medial elbow joint space increases under a valgus load and then decreases when a maximal grip contraction is performed. This indicates that wrist and finger flexor muscle contraction may assist in limiting medial elbow joint space, a result similar to findings of previous research in vitro. Clinical Relevance: Muscle activation of the upper extremity limits the medial elbow joint space, suggesting that injury prevention programs for throwing athletes should incorporate exercises for the elbow, wrist, and hand to limit excessive medial elbow joint space gapping during activities that create high valgus load.

Single-stage reconstruction of high-voltage electric burns sequelae of volar forearm using nerve grafts, short tendon grafts and microvascular flap

Introduction: A total of 10 patients underwent single-stage reconstruction of high-voltage electrical burn sequelae at the distal forearm and volar wrist, in patients with complete loss of motor and sensory function of the hand; all 10 were operated using interposition tendon grafts for the flexor digitorum profundus, nerve grafts for the median and ulnar nerves and the anterolateral thigh flap (ALT) for coverage; in addition, the fascial component of the flap was used to wrap the repaired finger flexors. Materials and Methods: All the flaps survived, and eight of the 10 patients had S3 or S4 recovery of median nerve sensation. Results: The final outcome measurement was done by adopting a variant of the abbreviated upper extremity functional index. The mean value for this was 19 of a possible 40 points (range in 10 patients −7 to 28). Discussion: Single-stage reconstruction using short tendon grafts and nerve grafts is a useful procedure in high-voltage electrical burns. Conclusion: The use of the ALT with vascularised fascia permits early finger flexor activity suitable for activities of daily living.

Hand rehabilitation after stroke using a wearable, high DOF, spring powered exoskeleton.

Stroke patients often have inappropriate finger flexor activation and finger extensor weakness, which makes it difficult to open their affected hand for functional grasp. The goal was to develop a passive, lightweight, wearable device to enable improved hand function during performance of activities of daily living. The device, HandSOME II, assists with opening the patient's hand using 11 elastic actuators that apply extension torques to finger and thumb joints. Device design and initial testing are described. A novel mechanical design applies forces orthogonal to the finger segments despite the fact that all of the device DOFs are not aligned with human joint DOF. In initial testing with seven stroke subjects with impaired hand function, use of HandSOME II significantly increased maximum extension angles and range of motion in all of the index finger joints (P<;0.05). HandSOME II allows performance of all the grip patterns used in daily activities and can be used as part of home-based therapy programs.

The Effects on Shoulder Stabilizer Activation of Finger Flexor Activation during the Push-up Plus Exercise

[Purpose] We investigated the effect of the finger flexor muscles activation on the stabilizer muscle of the shoulder joint during push-up exercise using a push up grip to increase the muscle activation of the finger flexor, had a distal part. [Subjects] The subjects were 18 healthy male adults in their 20s who normal ROM and no musculoskeletal disease of the shoulder complex and the upper limbs. [Methods] The subjects performed push-ups (vertical and transverse grips, and on flat ground) three times. The muscle activity was measured three times when performing the exercise using the push-up grip (vertical and transverse grips) and on flat ground, and the mean values were used for the analysis. To prevent the effect of muscle fatigue of the shoulder stabilizer muscles, the three different exercise positions were randomly performed. [Results] The muscle activations induced under the three different conditions were compared and the results showed that there were significant differences among the wrist flexor bundle, wrist extensor bundle, biceps brachii, triceps brachii, pectoralis major, deltoid, serratus anterior muscles. [Conclusion] It is possible that finger flexor and extensor muscle activation elevated to increase stability in performing the exercise on the push-up grip as it is ales stable position than the push-up plus exercise on flat ground. We assume that the distal part muscle activation affected the muscle activation of the shoulder stabilizer, proximal part, muscles.

Delays in Grip Initiation and Termination in Persons With Stroke: Effects of Arm Support and Active Muscle Stretch Exercise

Stroke survivors' difficulty in releasing grasped objects may be attributable not only to impaired finger extension but also to delays in terminating activity in the gripping flexor muscles. This study was undertaken 1) to quantify the time needed to initiate and terminate grip muscular activity following stroke and 2) to examine effects of arm support, grip location, and active muscle stretch on the delays recorded in the paretic hand. Delays in initiation and termination of finger flexor muscle activity in response to an auditory stimulus were measured for both paretic and nonparetic hands of ten stroke survivors with chronic hemiparesis and the dominant hand of five neurologically intact subjects. Additionally, the delays for the paretic hand were recorded while an external arm support was used and after 30 min of active muscle stretch. We found that delays in grip initiation and termination were greatest for the paretic hand (1.9 and 5.0 s), followed by the nonparetic hand (0.5 and 1.6 s), and least for the control hand (0.2 and 0.4 s). Arm support reduced delay in grip termination 37% for the paretic hand. Repeated active muscle stretch resulted in 24% reduced delay in grip initiation and 32% increased delay in grip termination for the paretic hand. Therapies and interventions reducing these delays may improve the ability to grasp and release objects and thus increase functional independence for stroke survivors.

Wrist strength is dependent on simultaneous power grip intensity

The effect of grip activities on wrist flexion/extension strength was examined. Twelve healthy subjects performed maximum wrist flexion/extension exertions with one of five levels of simultaneous grip effort: minimum effort; preferred effort; 30%, 60% and 100% maximum voluntary contraction. As grip force increased from the minimum to the maximum effort, average wrist flexion strength increased 34% and average wrist extension strength decreased 10%. It appears that the finger flexor tendons on the volar aspect of the wrist act agonistically in wrist flexion and act antagonistically to wrist extension. When an object gripped by the hand is fragile or uncomfortable, the reduced finger flexor activity will limit wrist flexion strength. Gripping a slippery object that requires high grip effort will result in reduced wrist extension strength. Grip force should be controlled during measurement of wrist flexion or extension strength. When analysing a task that involves both grip and wrist exertions, use of grip/wrist strength values that were measured during grip exertions only, or wrist exertions only, may incorrectly estimate the true grip/wrist strength, as grip and wrist activities significantly interact with each other as demonstrated in this paper.

Physical exposure differences between children and adults when using standard and small computer input devices

By the age of five years, 75% of the children in the USA are using computers and at this age they are only one-half to two-thirds the size of and about one-fifth as strong as their adult counterparts. Fourteen children between five and eight years of age and their same-gender biological parents (giving a total of 28 subjects) were evaluated using both a standard and a smaller, child-proportional input device during standardised mouse and keyboard tasks. Typing and computer mouse performance were measured with tracking software, wrist posture was measured with an electrogoniometer and electromyography was used to measure finger flexor and extensor muscle activity in the right arm. With the small mouse, both children and adults performed the mouse task significantly faster and made significantly fewer errors. When using the standard-sized mouse and keyboard, children worked with significantly greater ulnar deviation and significantly less extension than their adult counterparts. When children used the smaller mouse, finger flexor muscle activity, finger extensor muscle activity and ulnar deviation significantly decreased, with little change in wrist extension compared to the standard mouse. No significant differences were observed between the standard and small keyboards for children or their parents. Compared to their adult counterparts, children had to apply twice the relative force, as a percentage of their maximum capacity, to activate the buttons and keys on the input devices. These measured differences may have application in the design of computer input devices for children.

Muscle activity and cardiovascular response during computer-mouse work with and without memory demands

Computer-mouse work is characterized by repetitive movements combined with mental demands. The present purpose was to study how the body responded to simulated Computer Aided Design (CAD) work without memory demand and when a high short-term memory demand was introduced. Nine female subjects repetitively performed a task which involved 15 s of elevation of the right index and middle fingers followed by 6 s of rest. Every second time the fingers rested, the left index finger was required to type a six-figure number, either ‘123456’ (without memory demand) or a random number shown half a minute before (with memory demand). After 7 min of performing the task without memory demand, the memory demand was introduced and continued for 1 h. Introduction of memory demand resulted in increased heart rate (77 ← 84 beats/min), blood pressure (systolic 129 ← 140 mmHg; diastolic 72 ← 79 mmHg) and forearm extensor muscle activity (wrist, 2.7 ← 4.5% EMGmax; finger, 5.6 ← 7.5% EMGmax) and finger flexor muscle activity (0.7 1.2% EMGmax) indicating increased co-contraction. Hereafter, muscle activity and cardiovascular response tended to decrease. Self-reported stress and rating of perceived exertion (RPE) for the right shoulder increased throughout the period. Two additional sub-studies were inlcuded, which focused on adaptation to the physical load, showing a decrease in muscle activity and arousal, and reintroduction of the memory load, showing a lower response as compared to the initial response. The practical consequences of the findings suggest that job content should have variable mental demands.

A Comparative Evaluation of Job Techniques in the Tree Nursery Industry

A pilot study was conducted as part of a larger project to assist a labor/management ergonomics team at a bareroot tree nursery in Washington State in developing potential solutions for reducing or eliminating risk factors for work-related musculoskeletal disorders (WMSDs). Measurements were collected of employees performing the jobs of Bin Unloading, Grading/Counting and Bag Closing using two different work techniques and workstation settings. Muscle activity (electromyography) of the distal upper extremity and back motion (Lumbar Motion Monitor) on three axes were recorded to determine differences in the WMSD risk factors between techniques. Bin unloading was performed with a bin flat on the stand and with the bin raised and tilted towards the worker. For grading/counting, the conveyor belts used to move trees were arranged in a stacked configuration and a side-by-side configuration. Closing the bags was performed by rolling the bag with two people and by folding the bags with one person. Paired t-tests were used to compare EMG data between methods and a mixed model was used to analyze LMM data. In general, grading/counting trees from a side-by-side conveyor configuration appeared to have slightly higher levels of finger flexor muscle activity, higher deltoid EMG static levels and back velocity and acceleration than grading from an over-under configuration. However, the differences were significant only for acceleration on the side bending and rotational axis and velocity on the sagittal and rotational axis. Workers unloading seedlings from bins that were raised and tilted forward experienced higher static, median and peak muscle levels, but slightly lower back velocity and acceleration. However, these results were not statistically significant. Bag folding appeared to have significantly higher levels of musculoskeletal risk factors, including higher deltoid, flexor and extensor muscle activity and higher ranges of movement, velocities and accelerations of the back. However, the number of workers exposed is less than for bag rolling.

The effect of keyboard keyswitch make force on applied force and finger flexor muscle activity

The design of the force-displacement characteristics or ‘feel’ of keyboard keyswitches has been guided by preference and performance data; there has been very little information on how switch ‘feel’ alters muscle activity or applied force. This is a laboratory-based repeated measures design experiment to evaluate the effect of computer keyboard keyswitch design on applied finger force and muscle activity during a typing task. Ten experienced typists typed on three keyboards which differed in keyswitch make force (0·34, 0·47 and 1·02 N) while applied fingertip force and finger flexor electromyograms were recorded. The keyboard testing order was randomized and subjects typed on each keyboard for three trials, while data was collected for a minimum of 80 keystrokes per trial. No differences in applied fingertip force or finger flexor EMG were observed during typing on keyboards with switch make force of 0·34 or 0·47 N. However, applied fingertip force increased by approximately 40% (p < 0·05) and EMG activity increased by approximately 20% (p < 0·05) when the keyswitch make force was increased from 0·47 to 1·02 N. These results suggest that, in order to minimize the biomechanical loads to forearm tendons and muscles of keyboard users, keyswitches with a make force of 0·47 N or less should be considered over switches with a make force of 1·02 N.

Restoration of key grip and release in the C6 tetraplegic patient through functional electrical stimulation

Electrical stimulation of selected paralyzed forearm and hand muscles in C6 spinal cord injury patients provides control of lateral pinch (key grip) and release. The movement augments tenodesis grip or the grip achieved through tendon transfer procedures. Chronically indwelling percutaneous coiled wire electrodes were implanted with hypodermic needles into thenar (adductor pollicis and/or opponens pollicis), finger flexor (flexor digitorum superficialis and profundus), and thumb extensor (extensor pollicis longus) muscles. The strength of contraction is controlled by changing the stimulus pulse width and frequency, which determine the number of active muscle fibers and their rate of activation, respectively. Finger flexor activation always precedes thumb adduction /opposition to provide a stable platform for lateral pinch; release is provided by stimulation of the thumb extensor. The patient controls the timing and the strength of the contraction from a single control signal. This control signal is a myoelectric signal (MES) from a muscle which retains voluntary function, e.g., sternocleidomastoid. Electrical activity from the muscle is processed (rectified and averaged) and used to activate the stimulator. Each command to control the muscle is proportional in time, i.e., once a lower threshold bound is exceeded with the MES, the command increases (or decreases) linearly until the MES falls below threshold again. A zero level MES maintains the stimulus; exceeding the upper bound reverses the direction of stimulus change or deactivates stimulation if the level is held long enough. Five subjects have been involved in the development of this system for periods of up to 2 years, and three are presently involved in its evaluation. The function the electrical stimulation provides has been beneficial in performing tonic tasks such as eating and writing.

Biomechanics of the Wrist

The wrist joint is a complex linkage between forearm and hand which is capable of an impressive arc of motion yet retaining a remarkable degree of stability. Carpal stability is derived from numerous intra-and intercarpal ligaments in addition to closely approximated wrist flexors and extensors. Motion occurring at the carpus is predominantly biplane--radial ulnar deviation and palmar flexion and extension. The center of motion for these planes of movement is located within the proximal and palmar pole of the capitate. When painful conditions arise at the wrist, a loss of wrist motion usually follows. Occasionally a loss of volitional control over wrist extensors is noted with the abnormal recruitment of wrist flexors with finger flexor activity. When instability and pain co-exist at the wrist, deformity can arise as a result of the inherent motor imbalance noted between the 6 wrist motors. Vector force analyses disclose that the flexor carpi ulnaris is the dominant wrist motor with the least significant force being supplied by the extensor carpi radialis longus. Although wrist motion is not essential for most activities of daily living, the preservation of wrist motion is for some individuals essential for the performance of specific occupational or recreational activities.