Denervation of the Joints of the Hand and Wrist: Surgical Techniques and a Systematic Review with Meta-Analysis.

BACKGROUND: Joint denervation of the wrist, basal joint of the thumb, and the finger is an option for patients with chronic pain. Compared with other surgical treatment options, function is preserved and the rehabilitation time is limited. A systematic review and meta-analysis were performed for each joint to determine whether the choice of technique and choice of denervation of specific articular sensory branches lead to a different outcome. METHODS: Embase, MEDLINE (OvidSP), Web of Science, Scopus, PubMed publisher, Cochrane, and Google Scholar database searches yielded 17 studies with reported outcome on denervation of the wrist, eight on the basal joint of the thumb, and five on finger joints. RESULTS: Overall, the level of evidence was low; only two studies included a control group, and none was randomized. Meta-analysis for pain showed a 3.3 decrease in visual analogue scale score for wrist pain. No difference was found between techniques (total versus partial denervation), nor did different approaches influence outcome. The first carpometacarpal joint showed a decrease for visual analogue scale score for pain of 5.4. Patient satisfaction with the treatment result was 83 percent and 82 percent, respectively. Reported pain in finger joints decreased 96 percent in the metacarpophalangeal joints, 81 percent in the proximal interphalangeal joint, and 100 percent in the distal interphalangeal joint. The only reported case in the metacarpophalangeal joint of the thumb reported an increase of 37 percent. CONCLUSIONS: Only denervation of the metacarpophalangeal joint of the thumb reported an increase in pain; however, this was a single patient. Wrist and first carpometacarpal joint and finger joint denervation have a high satisfaction rate and decrease the pain. There was no difference between techniques.

Pediatric Trigger Thumb with Metacarpophalangeal Joint Hyperextension or Instability.

BACKGROUND The aim of this study was to provide the first on report on the mechanism and the different treatment measures of metacarpophalangeal joint hyperextension (MCPH) or metacarpophalangeal joint instability (MCPI) in cases of pediatric trigger thumb. Some pediatric trigger thumb patients have disease combined with excessive extension of metacarpophalangeal (MCP) joint or instability of MCP joint. MATERIAL AND METHODS A total of 1083 children with trigger thumb surgery were divided into 2 groups (the MCPH group and the MCPI group) by the extension degree of the MCP joint. After tendon sheath released, the MCPH group was treated by a cast and the MCPI group was treated by a cast and a brace. We compared the differences in baseline data and the further functional activities of interphalangeal (IP) and MCP joint between the 2 groups. RESULTS Among the 1083 cases, 154 cases (185 thumbs) were trigger thumb with MCPH or MCPI, of which 167 thumbs were placed in the MCPH group and 18 thumbs were placed in the MCPI group. The average age of the MCPH group was 2.8 years, with an average duration of disease of 13 months. The average age of the MCPI group was 6.6 years, with an average duration of disease of 33 months. MCPH still existed after cast removal. In the MCPI group, 12 out of 18 thumbs recovered; 6 thumbs relapsed at 2-4 months after brace removal. CONCLUSIONS Trigger thumb with MCPH and MCPI in children is significantly associated with multi-joint laxity. While there was still MCPH after cast treatment, there was no need for further treatment during the short-term follow-up. Cast and brace treatment after surgery was a simple, easy method for treatment of MCPI and had a good effect.

Predictive value of metacarpophalangeal stabilization tests for simulated ulnar nerve lesion measured by a sensor glove.

STUDY DESIGN: A within-subject research design was used in this study. The difference of the range of motion (ROM) with and without ulnar nerve block was analyzed. INTRODUCTION: For the clinical evaluation of the functional effects of ulnar nerve palsy at the hand the relevance of clinical tests is in discussion. PURPOSE OF THE STUDY: The aim of the study was to evaluate the predictive value of 2 clinical tests for a simulated ulnar nerve lesion by motion analysis with a sensor glove. METHODS: In 28 healthy subjects, dynamic measurements of the finger joints were performed by a sensor glove with and without ulnar nerve block at the wrist. In the 0° metacarpophalangeal (MCP) stabilization test, the subjects were asked to stabilize the MCP joints actively in 0° while moving the interphalangeal joints, whereas at the 90° MCP stabilization test, the subjects stabilized the MCP joints actively in the 90° position. RESULTS: In the 0° MCP stabilization test, no remarkable changes of the ROM were found at the MCP joints; at the proximal interphalangeal joints 2-5, the ROM decreased with ulnar nerve block, significantly at the index, middle, and ring fingers (P < .05). In the 90° MCP stabilization test, the average ROM of the MCP joints 2-5 significantly increased with ulnar nerve block (P < .05), whereas at the PIP joints, the average ROM decreased (P < .05). DISCUSSION: The 90° MCP stabilization test had a high predictive value for the discrimination between healthy subjects and subjects with a simulated peripheral ulnar nerve lesion. CONCLUSIONS: The results could be relevant for the determination of the functional effect of ulnar nerve palsy and the quantification of clawing in hand rehabilitation. LEVEL OF EVIDENCE: II.

Seguridad de los portales metacarpofalángicos. Estudio anatómico / Metacarpophalangeal portal safety. An anatomical study

Objetivo: Cuantificar el riesgo de lesión de la inervación dorsal al realizar portales directos de la articulación metacarpofalángica del segundo al quinto dedo. Material y método: Se realizó un estudio anatómico de 11 extremidades superiores de cadáveres frescos. Tras colocarlos en torre de tracción, se realizaron los portales metacarpofalángicos a ambos lados del tendón extensor. Se disecaron las ramas sensitivas dorsales y se midieron las distancias entre el portal y el nervio más cercano mediante un calibrador digital. Se compararon de forma global los portales de todos los dedos para valorar el dedo más seguro y se compararon dos a dos los portales radial y ulnar en cada uno de los dedos, para valorar el portal más seguro dentro de cada dedo. Resultados: La comparación global de todos los portales y dedos mostró que el tercer dedo es el más seguro en cualquiera de sus portales, mientras que el lado ulnar del segundo y radial del cuarto son los que tienen riesgo más alto de lesión nerviosa (p=8,96·10-5). La comparación dos a dos de los portales radial y ulnar en cada uno de los dedos mostró que el portal ulnar en más seguro que el radial en el cuarto dedo (p=0,042), mientras que el radial es más seguro que el ulnar en el quinto dedo (p=0,003). Conclusiones: El tercer dedo fue el más seguro para la realización de los portales metacarpofalángicos, mientras que el lado ulnar del segundo dedo y el lado radial del cuarto son los de más alto riesgo de lesión nerviosa

Aim: To quantify the risk of dorsal innervation injury when performing direct metacarpophalangeal joint portals of the second to fifth fingers. Material and method: An anatomical study of 11 upper limbs of fresh corpses was carried out. After placing them in a traction tower, the metacarpophalangeal portals were developed on both sides of the extensor tendon. The dorsal sensory branches were dissected and the distances between the portal and the nearest nerve were measured by a digital caliper. The portals of all the fingers were compared globally to assess the safest finger and two to two radial and ulnar portals were compared in each of the fingers to assess the safest portal within each finger. Results: The overall comparison of all portals and fingers showed that the third finger is the safest in any of its portals, while the ulnar side of the second and radial of the fourth are the portals with the highest risk of nerve injury (P=8.96·10-5). Comparing two to two of the radial and ulnar portals in each of the fingers showed that the ulnar portal is safer than the radial on the fourth finger (P=.042), while the radial is safer than the ulnar on the fifth finger (P=.003). Conclusions: The third finger was the safest to perform metacarpophalangeal portals, while the ulnar side of the second finger and radial side of the fourth had the highest risk of nerve injury

Metacarpophalangeal portal safety. An anatomical study. / Seguridad de los portales metacarpofalángicos. Estudio anatómico.

AIM: To quantify the risk of dorsal innervation injury when performing direct metacarpophalangeal joint portals of the second to fifth fingers. MATERIAL AND METHOD: An anatomical study of 11 upper limbs of fresh corpses was carried out. After placing them in a traction tower, the metacarpophalangeal portals were developed on both sides of the extensor tendon. The dorsal sensory branches were dissected and the distances between the portal and the nearest nerve were measured by a digital caliper. The portals of all the fingers were compared globally to assess the safest finger and two to two radial and ulnar portals were compared in each of the fingers to assess the safest portal within each finger. RESULTS: The overall comparison of all portals and fingers showed that the third finger is the safest in any of its portals, while the ulnar side of the second and radial of the fourth are the portals with the highest risk of nerve injury (P=8.96·10-5). Comparing two to two of the radial and ulnar portals in each of the fingers showed that the ulnar portal is safer than the radial on the fourth finger (P=.042), while the radial is safer than the ulnar on the fifth finger (P=.003). CONCLUSIONS: The third finger was the safest to perform metacarpophalangeal portals, while the ulnar side of the second finger and radial side of the fourth had the highest risk of nerve injury.

Denervation of the metacarpophalangeal joint.

Metacarpophalangeal joint osteoarthritis is a relatively common condition that hand surgeons have to deal with. When daily activities are impaired by pain and all conservative measures have failed, surgical treatments such as arthrodesis or joint replacement are indicated. In this article, a technique for joint denervation is presented as a treatment for painful degenerative or posttraumatic osteoarthritis. Its preliminary results, potential complications, and contraindications are also discussed.

[Permanent abduction of the little finger without ulnar nerve palsy: a case report]. / Abduction permanente isolée du cinquième doigt sans paralysie ulnaire. À propos d'un cas.

Wartenberg's sign, or permanent abduction of the little finger, occurs in the context of sequelae of ulnar nerve palsy. Its presence alone is rarely reported in the literature and is due to avulsion of the insertion of the third volar interosseous muscle. Several surgical techniques to correct this sign are reported in the literature. The authors report the case of a Wartenberg's sign without ulnar nerve palsy due to traumatic avulsion of the third volar interosseous muscle that was treated by a transfer of the extensor digiti minimi onto the radial side of the extensor digitorium communis according to technique of Bellan et al. After 1-year follow-up, result was good with no recurrence of any deformities and a normal active extension.

Effect of sensory feedback from the proximal upper limb on voluntary isometric finger flexion and extension in hemiparetic stroke subjects.

This study investigated the potential influence of proximal sensory feedback on voluntary distal motor activity in the paretic upper limb of hemiparetic stroke survivors and the potential effect of voluntary distal motor activity on proximal muscle activity. Ten stroke subjects and 10 neurologically intact control subjects performed maximum voluntary isometric flexion and extension, respectively, at the metacarpophalangeal (MCP) joints of the fingers in two static arm postures and under three conditions of electrical stimulation of the arm. The tasks were quantified in terms of maximum MCP torque [MCP flexion (MCP(flex)) or MCP extension (MCP(ext))] and activity of targeted (flexor digitorum superficialis or extensor digitorum communis) and nontargeted upper limb muscles. From a previous study on the MCP stretch reflex poststroke, we expected stroke subjects to exhibit a modulation of voluntary MCP torque production by arm posture and electrical stimulation and increased nontargeted muscle activity. Posture 1 (flexed elbow, neutral shoulder) led to greater MCP(flex) in stroke subjects than posture 2 (extended elbow, flexed shoulder). Electrical stimulation did not influence MCP(flex) or MCP(ext) in either subject group. In stroke subjects, posture 1 led to greater nontargeted upper limb flexor activity during MCP(flex) and to greater elbow flexor and extensor activity during MCP(ext). Stroke subjects exhibited greater elbow flexor activity during MCP(flex) and greater elbow flexor and extensor activity during MCP(ext) than control subjects. The results suggest that static arm posture can modulate voluntary distal motor activity and accompanying muscle activity in the paretic upper limb poststroke.

Neuroma of the radial digital nerve of the middle finger following trigger release.

Trigger digit release is a common surgical procedure with a low complication rate. One of the potential complications is digital nerve injury. Though uncommon, digital nerve injury can be significantly symptomatic to the patient. We report a case of radial digital nerve neuroma formation following trigger release of the middle finger, which is considered to be safe, in terms of risk of digital nerve injury. We discuss our management of the complication, possible pitfalls which may have resulted in the complication in our case and offer possible means of overcoming these pitfalls.

Preserving the superficial branch of the radial nerve during carpometacarpal and metacarpophalangeal joint arthroscopy: an anatomical study.

BACKGROUND: The superficial branch of the radial nerve (SBRN) is potentially at risk during thumb carpometacarpal (TCM) or thumb metacarpophalangeal (TMP) joint arthroscopy. The aim of this anatomical study was to describe the different branching patterns of the SBRN and to optimize positioning of portals during TCM and TMP arthroscopy. METHODS: The SBRN was dissected in 30 forearms. Three branches of the nerve (SR1, SR2, and SR3) were recorded and distances between SBRN branches and portals used for carpometacarpal (TCM) and metacarpophalangeal (TMP) joints of the thumb arthroscopy were measured. Three main portals were used for TCM joint arthroscopy. These portals were an ulnar portal (1-U), a radial portal (1-R), and an accessory portal (D-2). A radial metacarpophalangeal (MCP-rad) and an ulnar metacarpophalangeal (MCP-uln) portal were used for TMP joint arthroscopy. RESULTS: In 24 cases (80%), the 1-R portal was inserted radially (volar) to SR3 at a mean distance of 4.8 mm (0-8). In the remaining six cases (20%) when 1-R portal was inserted ulnar (dorsal) to SR3, the distance was less than 2 mm in all cases. SR3 was always far from the 1-U portal at a mean 13 mm (7-22). The D-2 portal was always close to SR2-D1 at a mean distance of 1.7 mm (0-6). The distance from SR2-D2 and D-2 portal was also inferior by 5 mm. At the level of the metacarphalangeal joint of the thumb, the MCP-rad portal was always situated dorsally and very close to SR3, at a mean distance of 1 mm (0-5). The MCP-uln portal was also situated dorsal to SR2-D1 at a mean distance of 3.7 mm (1.5-6.5). CONCLUSION: The results of this anatomical study confirm actual reported findings about the SR2 and SR3 branches. These two branches of the SBRN are the most at risk of injury during TCM and TMP joint arthroscopy. According to our measurements, the 1-U portal is a safer portal than 1-R and D-2 portal for TCM arthroscopy and should be preferred for surgery necessitating only one portal. Concerning TMP arthroscopy, the SBRN appears less at risk of injury when using a MCP-uln portal and safer than MCP-rad which is at risk at less than 5 mm from the extensor pollicis longus tendon.

Stretch reflexes and joint dynamics in rheumatoid arthritis.

In clinically diagnosed rheumatoid arthritis (RA), studies were conducted to investigate the reflex and passive tissue contribution to measured increases in joint stiffness in the resting upper limb and during constant contractions of an attached muscle. The tonic stretch reflex was induced by a servo-controlled sinusoidal stretch perturbation of the metacarpophalangeal joint of RA patients, and age- and sex-matched controls. The resulting reflexes and mechanical changes in the RA affected joint were explored. Surface electromyographic (EMG) measurements were obtained from first dorsal interosseus muscle. Reflex gain (EMG/joint angle amplitude ratio), phase difference (reflex delay after stretch), coherence square (proportion of EMG variance accounted for by joint angle changes), joint mechanical gain (torque-joint angle amplitude ratio) and mechanical phase difference (torque response delay after stretch) were determined. RA patients showed decreased reflex gain that was partly due to coexistent severe muscle weakness, as determined from maximum voluntary contraction and grip pressure estimates. The decreased reflex gain was most evident at high stretch frequency suggesting a disproportionate loss of the large diameter afferent response and also increased reflex delay in the patients. These changes ensemble suggest significant loss of neural drive to the motor unit population. Patients also showed increased joint stiffness (measured as torque gain) in the contracting muscle, but there was no evidence of reflex activity or increased stiffness at rest. This suggests that the increased joint stiffness in RA was due to changes in the mechanical properties of the active muscle-joint system rather than changes in reflex properties.

Transfer of supinator motor branches to the posterior interosseous nerve in C7-T1 brachial plexus palsy.

OBJECT: In C7-T1 palsies of the brachial plexus, shoulder and elbow function are preserved, but finger motion is absent. Finger flexion has been reconstructed by tendon or nerve transfers. Finger extension has been restored ineffectively by attaching the extensor tendons to the distal aspect of the dorsal radius (termed tenodesis) or by tendon transfers. In these palsies, supinator muscle function is preserved, because innervation stems from the C-6 root. The feasibility of transferring supinator branches to the posterior interosseous nerve has been documented in a previous anatomical study. In this paper, the authors report the clinical results of supinator motor nerve transfer to the posterior interosseous nerve in 4 patients with a C7-T1 root lesion. METHODS: Four adult patients with C7-T1 root lesions underwent surgery between 5 and 7 months postinjury. The patients had preserved motion of the shoulder, elbow, and wrist, but they had complete palsy of finger motion. They underwent finger flexion reconstruction via transfer of the brachialis muscle, and finger and thumb extension were restored by transferring the supinator motor branches to the posterior interosseous nerve. This nerve transfer was performed through an incision over the proximal third of the radius. Dissection was carried out between the extensor carpi radialis brevis and the extensor digitorum communis. The patients were followed up as per regular protocol and underwent a final evaluation 12 months after surgery. To document the extent of recovery, the authors assessed the degree of active metacarpophalangeal joint extension of the long fingers. The thumb span was evaluated by measuring the distance between the thumb pulp and the lateral aspect of the index finger. RESULTS: Surgery to transfer the supinator motor branches to the posterior interosseous nerve was straightforward. Twelve months after surgery, all patients were capable of opening their hand and could fully extend their metacarpophalangeal joints. The distance of thumb abduction improved from 0 to 5 cm from the lateral aspect of the index finger. CONCLUSIONS: Transferring supinator motor nerves directly to the posterior interosseous nerve is effective in at least partially restoring thumb and finger extension in patients with lower-type injuries of the brachial plexus.

Clinical implications of cerebral reorganisation after primary digital flexor tendon repair.

After flexor tendon injury, most attention is given to the quality of the tendon repair and postoperative early passive dynamic mobilisation. Schemes for active mobilisation have been developed to prevent tendon adhesions and joint stiffness. This paper describes five patients to demonstrate the cerebral consequences of immobilisation allowing only passive movements, which implies a prolonged absence of actual motor commands. At the end of such immobilisation, PET imaging revealed reduced blood flow in specific motor areas, associated with temporary loss of efficient motor control. Effective motor control was regained after active flexion exercises which was reflected in normalised cerebral activations. This suggests that temporary, reversible cerebral dysfunction may affect the outcome of flexor tendon injuries.

Endpoint force fluctuations reveal flexible rather than synergistic patterns of muscle cooperation.

We developed a new approach to investigate how the nervous system activates multiple redundant muscles by studying the endpoint force fluctuations during isometric force generation at a multi-degree-of-freedom joint. We hypothesized that, due to signal-dependent muscle force noise, endpoint force fluctuations would depend on the target direction of index finger force and that this dependence could be used to distinguish flexible from synergistic activation of the musculature. We made high-gain measurements of isometric forces generated to different target magnitudes and directions, in the plane of index finger metacarpophalangeal joint abduction-adduction/flexion-extension. Force fluctuations from each target were used to calculate a covariance ellipse, the shape of which varied as a function of target direction. Directions with narrow ellipses were approximately aligned with the estimated mechanical actions of key muscles. For example, targets directed along the mechanical action of the first dorsal interosseous (FDI) yielded narrow ellipses, with 88% of the variance directed along those target directions. It follows the FDI is likely a prime mover in this target direction and that, at most, 12% of the force variance could be explained by synergistic coupling with other muscles. In contrast, other target directions exhibited broader covariance ellipses with as little as 30% of force variance directed along those target directions. This is the result of cooperation among multiple muscles, based on independent electromyographic recordings. However, the pattern of cooperation across target directions indicates that muscles are recruited flexibly in accordance with their mechanical action, rather than in fixed groupings.

Digital nerve reconstruction by multiple Y-shaped nerve grafts at the metacarpophalangeal joint level.

Digital nerve injuries are common; injuries of the common digital nerves are less frequent than those involving the proper digital nerves. Traditional techniques used to reconstruct peripheral nerves are: direct suture, autologous nerve grafts, autologous vein grafts, vascularised nerve graft and alloplastic nerve grafts. Autologous nerve grafts remain the most common conduits for segmental defects. Difficulties can arise when attempting to repair complex nerve gaps, particularly when joining the proximal stump of the common digital nerve with two distal stumps of proper digital nerves as in lesions involving the web space. We present below a case of such a lesion. We describe the use of the lateral antebrachial cutaneous nerve (LABCN) as donor nerve, by exploiting its natural branchings.

[Anatomical study of the nerve supply of the trapeziometacarpal joint. Fifteen dissections]. / Etude anatomique de l'innervation de l'articulation trapézo-métacarpienne. A propos de 15 dissections.

PURPOSE OF THE STUDY: When the radiological signs are minimal in patients with a painful carpal syndrome involving the trapeziometacarpal joint (TMCJ), selective articular denervation can be proposed as an alternative after failure of conservative treatment. Results have been variable, sometimes disappointing, suggesting the anatomic basis of denervation should be revisited. The purpose of this work was to study the nerve supply to the TMCJ in order to acquire the indispensable elements necessary for performing effective selective articular denervation. MATERIAL AND METHODS: This anatomical study was performed by dissection under magnification (4.5-x350) of 15 upper limb cadaver specimens. The median nerve, its thenar and volar cutaneous branches and the terminal sensorial branches of the radial nerve were dissected. Articular branches to the TMCJ were carefully identified. Histological samples were taken to verify the neurological nature of the elements dissected. RESULTS: All TMCJs dissected exhibited radial and median nerve supply. Branches of the median nerve predominated in number and caliber. The volar cutaneous branch gave rise to articular branches in eleven dissections and the thenar branch gave rise to articular branches via a retrograde arciform trajectory between the short abductor and the opponens digiti pollicis in thirteen. For five dissections, the TMCJ branches arose directly from the median nerve within the carpal tunnel. At histological analysis the dissected elements were identified as nerves. DISCUSSION: There have been few anatomic studies concerning the nerve supply of the TMCJ. Unlike the findings reported by Cozzi in 1960, we did not find the dorsal sensorial branch of the radial nerve to play an exclusive or preponderant role in the innervation of the TMCJ. The median nerve supply to the TMCJ appeared to be more significant, particularly for the volar cutaneous and especially thenar branches. CONCLUSION: Total and definitive selective denervation of the TMCJ appears to be a most difficult procedure which would require a very wide access and extensive dissection, including the thenar branch which would raise the risk of significant complications.

[Innervation of metacarpophalangeal joint and distal interphalangeal joint: an anatomical and histological study].

Using 131 fingers for the metacarpophalangeal (MP) joint and 124 fingers for the distal interphalangeal (DIP) joint obtained from 30 hands of human cadavers, the innervation of the MP and DIP joints was investigated anatomically in detail. Two articular branches developing from a dorsal branch of the ulnar nerve and a superficial branch of the radial nerve, and entering the dorsal side of the MP joint from the ulnar side and radial side, respectively, were found in every finger. In addition, articular branches from the deep branch of the ulnar nerve were found in every middle, ring and little finger. However, articular branches from the proper palmar digital nerve were found to exist in 62.7% of the fingers. Articular branches developing from the proper palmar digital nerve and going towards the DIP joint were found in every case, and 97.3% of 244 branches developed directly from the proper palmar digital nerve, while some of the remaining branches were from a dorsal branch of the proper palmar digital nerve and others developed neural loop penetration. Articular branches ran parallel to the distal transverse artery and entered the joint, and some of them went towards the volar plate, dorsal joint capsule, and tendon sheath. Many nerve endings existed in the surface layer of the articular capsule and arthrosynovial membranes in the form of Pacinian corpuscles and corpuscles of Ruffini. The existence of a neural loop in the finger should be taken notice of during somatoscopy in patients with neurovascular symptoms in the fingertip or surgical operation on a vascular pedicular island flap. Further, it was suggested that injury of the articular branch of the DIP joint could induce Heberden nodes due to its anatomical characteristics.

Sensory integration in the perception of movements at the human metacarpophalangeal joint.

These experiments were designed to investigate illusions of movements of the fingers produced by combined feedback from muscle spindle receptors and receptors located in different regions of the skin of the hand. Vibration (100 Hz) applied in cyclic bursts (4 s 'on', 4 s 'off') over the tendons of the finger extensors of the right wrist produced illusions of flexion-extension of the fingers. Cutaneous receptors were activated by local skin stretch and electrical stimulation. Illusory movements at the metacarpophalangeal (MCP) joints were measured from voluntary matching movements made with the left hand. Localised stretch of the dorsal skin over specific MCP joints altered vibration-induced illusions in 8/10 subjects. For the group, this combined stimulation produced movement illusions at MCP joints under, adjacent to, and two joints away from the stretched region of skin that were 176 +/- 33, 122 +/- 9 and 67 +/- 11 % of the size of those from vibration alone, respectively. Innocuous electrical stimulation over the same skin regions, but not at the digit tips, also 'focused' the sensation of movement to the stimulated digit. Stretch of the dorsal skin and compression of the ventral skin around one MCP joint altered the vibration-induced illusions in all subjects. The illusions became more focused, being 295 +/- 57, 116 +/- 18 and 65 +/- 7 % of the corresponding vibration-induced illusions at MCP joints that were under, adjacent to, and two joints away from the stimulated regions of skin, respectively. These results show that feedback from cutaneous and muscle spindle receptors is continuously integrated for the perception of finger movements. The contribution from the skin was not simply a general facilitation of sensations produced by muscle receptors but, when the appropriate regions of skin were stimulated, movement illusions were focused to the joint under the stimulated skin. One role for cutaneous feedback from the hand may be to help identify which finger joint is moving.

Innervation of the metacarpophalangeal and interphalangeal joints: a microanatomic and histologic study of the nerve endings.

Six pairs of fresh human cadaver hands were dissected under the surgical microscope at x28 to x32 and selectively silver stained. In addition, 18 proximal interphalangeal and metacarpophalangeal joints of fresh cadaver hands were processed with protein gene product 9.5 for measurement and analysis of nerve endings in those joints. The results demonstrated that the proximal interphalangeal joints are innervated by 2 palmar articular nerves (mean diameter, 0.21-0.53 mm). Each metacarpophalangeal joint of the second through fifth fingers is predominantly supplied by 1 palmar articular nerve (mean diameter, 0.41-0.59 mm), which comes from the deep branches of the ulnar nerve, as well as by 2 dorsal articular nerves (mean diameter, 0.11-0.24 mm). The metacarpophalangeal joint of the thumb also had 2 dorsal articular nerves (mean diameter, 0.18-0.24 mm) and 2 palmar joint nerves (mean diameter, 0.29-0.31 mm). The mean densities of the type IV free nerve endings and the mean numbers of the encapsulated endings in the palmar capsules were consistently much greater than in the dorsal or lateral capsules. The majority of encapsulated endings were pacinian corpuscles. The anatomic and histologic information may help the surgeon avoid damaging these small joint nerves during operative procedures and to reconstruct or de-innervate them if necessary. (J Hand Surg 2000; 25A:128-133.