Distribution of nerve endings in human thumb interphalangeal joint.

This study aims to quantitatively analyze the distribution of encapsulated nerve endings in the human thumb interphalangeal (IP) joint capsule. There are three types of nerve endings. Type-I nerve endings (Ruffini-like ending) sense pressure changes, Type II (Pacini-like ending) nerve endings contribute to the kinesthetic sense, and Type III (Golgi-like ending) nerve ending provides proprioceptive information. We dissected five right thumbs IP joints from freshly frozen cadavers (5 men). The mean age of the cadavers at the time of death was 63.4 years (55-73). Sections were stained with the hematoxylin-eosin and antiprotein gene product 9.5 (PGP9.5) to identify encapsulated nerve endings. Transverse sections were cut and divided into volar, dorsal, and then into two equal parts, proximal and distal. The density of encapsulated nerve endings compared to volar versus dorsal and proximal versus distal regions was examined. This study showed that type 1 nerve endings were more common in the distal parts of the IP joint (p < 0.05). Also, type 3 nerve endings were observed in the thumb IP joint. There was no difference between regions in type II and type III nerve endings. The current study demonstrates that the distribution of encapsulated nerve endings in the IP joint is different from the PIP and DIP joints. Moreover, further studies are required to understand the thumb's physiology.

Base of the Third Metacarpal as a Palpable and Reliable Landmark for Identifying the Median Nerve's Thenar Branch.

PURPOSE: The objective of this study was to investigate whether the base of the third metacarpal can predict the location of the thenar branch (TB) of the median nerve and the accuracy of palpating the base of the third metacarpal. METHODS: In 15 patients with ulnar nerve lesions around the elbow, we transferred the opponens motor branch to repair the deep terminal division of the ulnar nerve (DTDUN). Before surgery, we located the TB by palpating the base of the third metacarpal volarly. During surgery, we placed three needles at the following places: one at the entrance of the TB into the abductor pollicis brevis, another at the point where the TB contacted the thenar muscles, and third at the DTDUN's trajectory over the third metacarpal. We obtained fluoroscopic images and measured distances between the needles and structures with image software. We also examined the relationship between the TB, DTDUN, and the volar tubercle of the base of the third metacarpal in cadaver hands. Finally, we invited 22 surgeons to palpate the base of the third metacarpal on volunteer hands and verified their accuracy using fluoroscopy. RESULTS: During surgery, after dissection and palpation of the TB, under fluoroscopy, we confirmed that the palpable bone prominence was the base of the third metacarpal. In cadaver dissections, we observed the TB crossing the volar tubercle of the base of the third metacarpal superficially from proximal to distal and from ulnar to radial. The DTDUN was, on average, 14 mm distal to the base of the third metacarpal distal limit. In total, 19 of the 22 surgeons correctly identified the base of the third metacarpal and consequently the trajectory of the TB. CONCLUSIONS: The palpable base of the third metacarpal can be used to determine the trajectory of both the TB and DTDUN. TYPE OF STUDY/LEVEL OF EVIDENCE: Diagnostic II.

Anterior interosseous nerve syndrome following infection with COVID-19: a case report.

BACKGROUND: Various neurological manifestations associated with coronavirus disease 2019 have been increasingly reported. Herein, we report a rare case of anterior interosseous nerve syndrome, which occurred 5 days after the onset of coronavirus disease 2019. CASE PRESENTATION: A 62-year-old Asian woman with a history of coronavirus disease 2019 who developed a complete motor deficit in the left flexor pollicis longus and pronator quadratus without sensory deficits. The symptoms appeared as a sudden onset fatigue and severe pain of the left arm, 5 days after the onset of coronavirus disease 2019. She noticed paralysis of the left thumb at 2 weeks after the onset of coronavirus disease 2019. Electromyography assessment of the anterior interosseous nerve-dominated muscles revealed neurogenic changes such as positive sharp wave and fibrillation in flexor pollicis longus and pronator quadratus, confirming the diagnosis of anterior interosseous nerve syndrome. There were no other diseases that could have resulted in peripheral nerve palsy. We performed a functional reconstruction surgery of the thumb by tendon transfer from the extensor carpi radialis longus to the flexor pollicis longus. The patient reported a good patient-reported outcome (2.27 points in QuickDASH Disability/Symptom scoring and 5 points in Hand20 scoring) at final follow-up (1 year after the surgery). CONCLUSION: This case highlights the need for vigilance regarding the possible development of anterior interosseous nerve syndrome in patients with coronavirus disease 2019. Tendon transfer from extensor carpi radialis longus to flexor pollicis longus can provide good functional recovery for unrecovered motor paralysis after anterior interosseous nerve syndrome.

First dorsal metacarpal artery flap with dorsal digital nerve with or without dorsal branch of the proper digital nerve produces comparable short-term sensory outcomes.

BACKGROUND: The first dorsal metacarpal artery flap, including dorsal digital nerves with or without dorsal branches of the proper digital nerves, can be used to reconstruct thumb pulp defects with good results. However, it is still unclear whether there are differences in the sensory outcomes between preserving or not preserving the dorsal branches of the proper digital nerves. METHODS: This retrospective cohort study included 137 thumb pulp defect patients who underwent first dorsal metacarpal artery flap reconstruction procedure from October 2015 to June 2019. Patients were divided into two groups according to whether the dorsal branches of the proper digital nerves were preserved. In the non-preservation group (n = 80), the dorsal digital nerves were included in the flap for sensory reconstruction. In the preservation group (n = 57), the dorsal digital nerves and the dorsal branches of the proper digital nerves of the index finger were included in the flap. The stump of the proper digital nerves in the defect was coaptated to the donor nerves of the flap using the end-to-end fashion. At the last follow-up, static two-point discrimination, Semmes-Weinstein monofilament scores, pain, cold intolerance of the reconstructed finger, and patient satisfaction in both groups were compared. RESULTS: All patients were followed up for at least 17 months. No significant differences were found regarding pain of thumb pulp, static two-point discrimination, Semmes-Weinstein monofilament score, cold intolerance in the injured finger, and patient satisfaction. The non-preservation group presented slightly shorter operative times (p < 0.05). CONCLUSION: There are no differences at 2 years in postoperative clinical outcomes when dorsal digital nerves are used to reconstruct flap sensation regardless of preservation of the dorsal branches of the proper digital nerves in the first dorsal metacarpal artery flap. LEVEL OF EVIDENCE: Level III, retrospective comparative study.

Emerging of new bioartificial corticospinal motor synergies using a robotic additional thumb.

It is likely that when using an artificially augmented hand with six fingers, the natural five plus a robotic one, corticospinal motor synergies controlling grasping actions might be different. However, no direct neurophysiological evidence for this reasonable assumption is available yet. We used transcranial magnetic stimulation of the primary motor cortex to directly address this issue during motor imagery of objects' grasping actions performed with or without the Soft Sixth Finger (SSF). The SSF is a wearable robotic additional thumb patented for helping patients with hand paresis and inherent loss of thumb opposition abilities. To this aim, we capitalized from the solid notion that neural circuits and mechanisms underlying motor imagery overlap those of physiological voluntary actions. After a few minutes of training, healthy humans wearing the SSF rapidly reshaped the pattern of corticospinal outputs towards forearm and hand muscles governing imagined grasping actions of different objects, suggesting the possibility that the extra finger might rapidly be encoded into the user's body schema, which is integral part of the frontal-parietal grasping network. Such neural signatures might explain how the motor system of human beings is open to very quickly welcoming emerging augmentative bioartificial corticospinal grasping strategies. Such an ability might represent the functional substrate of a final common pathway the brain might count on towards new interactions with the surrounding objects within the peripersonal space. Findings provide a neurophysiological framework for implementing augmentative robotic tools in humans and for the exploitation of the SSF in conceptually new rehabilitation settings.

Comparison of the on-line effects of different motor simulation conditions on corticospinal excitability in healthy participants.

In healthy participants, corticospinal excitability is known to increase during motor simulations such as motor imagery (MI), action observation (AO) and mirror therapy (MT), suggesting their interest to promote plasticity in neurorehabilitation. Further comparing these methods and investigating their combination may potentially provide clues to optimize their use in patients. To this end, we compared in 18 healthy participants abductor pollicis brevis (APB) corticospinal excitability during MI, AO or MT, as well as MI combined with either AO or MT. In each condition, 15 motor-evoked potentials (MEPs) and three maximal M-wave were elicited in the right APB. Compared to the control condition, mean normalized MEP amplitude (i.e. MEP/M) increased during MI (P = .003), MT (P < .001) and MT + MI (P < .001), without any difference between the three conditions. No MEP modulation was evidenced during AO or AO + MI. Because MI provided no additional influence when combined with AO or MT, our results may suggest that, in healthy subjects, visual feedback and unilateral movement with a mirror may provide the greatest effects among all the tested motor simulations.

Marinacci anastomosis (reverse Martin-Gruber anastomosis): A case report.

RATIONALE: The incidence of Martin-Gruber anastomosis ranges from 5% to 34%, which is characterized by crossing over from the median to the ulnar nerve and innervating the first dorsal interosseous, thenar or hypothenar muscles. However, the reverse Martin-Gruber anastomosis, or Marinacci anastomosis, is far less discussed and appears in recent literature. PATIENT CONCERNS: A 56-year-old man presented to the clinic of a university hospital because of left neck soreness with numbness radiating to the left lateral shoulder. The neck discomfort was aggravated while the neck rotated or tilted to the right. DIAGNOSIS: Higher compound muscle action potential over the abductor pollicis brevis on elbow stimulation than on the wrist was found during upper limb nerve conduction velocity study. Ulnar to median anastomosis was identified. INTERVENTION: We performed cervical spine X-ray and electrophysiological examinations and monitored the patient. OUTCOMES: We identified that this patient had left C5 and C6 subacute radiculopathy with active denervation and left subclinical ulnar sensory neuropathy, and verified the existence of ulnar-to-median anastomosis. LESSONS: We demonstrated a pure motor ulnar-to-median anastomosis without sensory correspondence and higher CMAP over the abductor pollicis brevis on elbow stimulation of the ulnar nerve than on the wrist. The prevalence might be underestimated in a Chinese population-based published study.

Surgical denervation of the thumb CMC joint: anatomy, technique.

Surgical denervation of the thumb carpometacarpal (CMC) joint is a theoretical surgical option for thumb CMC arthritis. Some authors have described the nerve branches of thumb CMC joint. We present the innervation of the thumb CMC joint (thenar - recurrent - branch of median nerve, palmar branch of median nerve, superficial branch of radial nerve, lateral cutaneous nerve of forearm, deep branch of ulnar nerve) and the surgical techniques to achieve optimal denervation of this joint. While the results have been disappointing, this technique may be combined with conservative surgical procedures (synovectomy, ligament reconstruction) and it allows more invasive surgery in the future if necessary.

Effect of a Novel Perturbation-Based Pinch Task Training on Sensorimotor Performance of Upper Extremity for Patients With Chronic Stroke: A Pilot Randomized Controlled Trial.

OBJECTIVE: To investigate the effects of perturbation-based pinch task training on the sensorimotor performance of the upper extremities of patients with chronic stroke via a novel vibrotactile therapy system. DESIGN: A single-blinded randomized controlled trial. SETTING: A university hospital. PARTICIPANTS: Patients with chronic stroke (N=19) randomly assigned into either an experimental group or a control group completed the study. INTERVENTIONS: In addition to 10 minutes of traditional sensorimotor facilitation, each participant in the experimental group received 20 minutes of perturbation-based pinch task training in each treatment session, and the controls received 20 minutes of task-specific motor training twice a week for 6 weeks. MAIN OUTCOME MEASURES: The scores for the primary outcome, Semmes-Weinstein monofilament (SWM), and those for the secondary outcomes, Fugl-Meyer Assessment (FMA), amount of use, quality of movement (QOM) on the Motor Activity Log (MAL) scale, and box and block test (BBT), were recorded. All outcome measures were recorded at pretreatment, post treatment, and 12-week follow-up. RESULTS: There were statistically significant between-group differences in the training-induced improvements revealed in the SWM results (P=.04) immediately after training and in the BBT results (P=.05) at the 12-week follow-up. The changes in muscle tone and in the QOM, SWM, and BBT scores indicated statistically significant improvements after 12 sessions of treatment for the experimental group. For the control group, a significant statistical improvement was found in the wrist (P<.001) and coordination (P=.01) component of the FMA score. CONCLUSIONS: This study indicated that the perturbation-based pinch task training has beneficial effects on sensory restoration of the affected thumb in patients with chronic stroke.

Donor nerve graft assessment for covering thumb nerve defects: a cadaveric study.

BACKGROUND: Even though several studies reported donor autologous nerve grafts for digital nerve defects, there is no report in the literature regarding acceptable graft for thumb nerves. The purpose of this study is to provide guidelines for autologous nerve graft selection by detecting similarities between thumb nerve zones and donor nerve with regard to the number of fascicles and cross-sectional area. MATERIALS AND METHODS: Five cadavers were used in this study. An anatomical zoning system was defined for thumb nerves (zones 1, 2, 3). Sural nerve (SN), medial antebrachial cutaneous nerve (MABCN), lateral antebrachial cutaneous nerve (LABCN), posterior interosseous nerve (PIN), and anterior interosseous nerve (AIN) were selected as donor nerve grafts. The number of fascicles and surface area (mm2) was defined. RESULTS: The mean of the fascicle number in zone 1, zone 2, zone 3, AIN, PIN, LABCN, MABCN, and SN were 3.8, 4.7, 6.1, 2.2, 1.8, 4.5, 3.1, and 6.4, respectively. The mean of the surface area in zone 1, zone 2, zone 3, AIN, PIN, LABCN, MABCN, and SN were 2.19, 6.26, 4.04, 1.58, 0.71, 5.00, 3.01, and 8.06, respectively. CONCLUSIONS: LABCN is the best choice for all zones that has fascicular matching with all three zones of thumb nerves and caliber matching with zones 2 and 3. In zone 1, the best nerve graft is MABCN which has both suitable caliber and fascicle count.

Reliability of the thumb localizing test and its validity against quantitative measures with a robotic device in patients with hemiparetic stroke.

OBJECTIVES: To examine the inter-rater reliability of the thumb localizing test (TLT) and its validity against quantitative measures of proprioception. METHODS: The TLT was assessed by two raters in a standardized manner in 40 individuals with hemiparetic stroke. Inter-rater reliability was examined with weighted Kappa. For the quantitative measures, a bimanual matching task in a planar robotic device was performed. Without vision, each participant moved the unaffected hand to the perceived mirrored location of the affected hand, which was passively moved by the robot. Three measures were taken after 54 trials: Variability, trial-to-trial variability of the mirrored-matched locations; Area, the ratio of the area enclosed by the active hand relative to the passive hand; and Shift, systematic shifts between the passive and active hands. The correlation between the TLT and each robotic measure was examined with Spearman's rank correlation coefficient. RESULTS: The overall weighted kappa of the TLT was 0.84 (P<0.001). The TLT correlated highly with Area (r = -0.71, P<0.001) and moderately with Variability (r = 0.40, P = 0.011). No significant correlation was found between the TLT and Shift. CONCLUSIONS: The TLT had a high inter-rater reliability, and was validated against quantitative measures of proprioception reflecting the perceived area of movement and variability of the limb location.

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.

[Transplantation of compound tissue flap of toe to reconstruct the thumb with necrosis caused by electric burns in four patients].

From January 2010 to December 2017, 4 patients of thumb with necrosis caused by electric burns (all male, aged from 31 to 58 years) were admitted to our hospital, with 1 patient of second degree injury of right thumb, 2 patients of third degree injury of right thumb, and 1 patient of third degree injury of left thumb. Routine debridement under general anesthesia was performed within 7 days after injury. The compound tissue flap of contralateral second toe was transplanted to reconstruct the thumb with third degree defect, and compound tissue flap of ipsilateral distal hallex was transplanted to reconstruct the thumb with second degree defect. Dorsalis pedics artery was anastomosed with radial artery, saphenous vein or dorsalis pedics vein was anastomosed with cephalic vein. The donor site was transplanted with split-thickness skin graft from autologous thigh. All the tissue flaps and skin grafts survived in 2 weeks after surgery. Within 1 year of follow-up, the reconstructed thumbs can achieve radial abduction and palmar abduction with good function. Reconstruction of thumb with free transplantation of compound tissue flap of toe is a good method to repair thumb with necrosis caused by electric burn.

Thumb and finger movement is reduced after stroke: An observational study.

Hand motor impairment is common after stroke but there are few comprehensive data on amount of hand movement. This study aimed to compare the amount of thumb and finger movement over an extended period of time in people with stroke and able-bodied people. Fifteen stroke subjects and 15 able-bodied control subjects participated. Stroke subjects had impaired hand function. Movement of the thumb and index finger was recorded using stretch sensors worn on the affected hand (stroke subjects) or the left or right hand (control subjects) for ∼4 hours during the day. A digit movement was defined as a monotonic increase or decrease in consecutive sensor values. Instantaneous digit position was expressed as a percentage of maximal digit flexion. Mixed linear models were used to compare the following outcomes between groups: (1) average amplitude of digit movement, (2) digit cadence and average digit velocity, (3) percentage of digit idle time and longest idle time. Amplitude of digit movement was not different between groups. Cadence at the thumb (between-group mean difference, 95% CI, p value: -0.6 movements/sec, -1.0 to -0.2 movements/sec, p = 0.003) and finger (-0.5 movements/sec, -0.7 to -0.3 movements/sec, p<0.001) was lower in stroke than control subjects. Digit velocity was not different between groups. Thumb idle time was not different between groups, but finger idle time was greater in stroke than control subjects (percentage of idle time: 6%, 1 to 11%, p = 0.02; longest idle time: 375 sec, 29 to 721 sec, p = 0.04). Rehabilitation after stroke should encourage the performance of functional tasks that involve movements at faster cadences, and encourage more frequent movement of the digits with shorter periods of inactivity.

Effect of sleep restriction on somatosensory sensitivity in the oro-facial area: An experimental controlled study.

BACKGROUND: No studies have addressed the effect of SR on somatosensory function in the oro-facial area. OBJECTIVES: The aim of this study was to investigate the effect of sleep restriction (SR) on the somatosensory perception of the tip of the tongue. MATERIALS AND METHODS: Using a crossover study design, 13 healthy participants took part in a random order, to a two arms experiments: the SR and control/no SR-arms. For all participants, the Epworth Sleepiness Scale (ESS) was used to assess sleepiness and mechanical sensitivity, and pain detection threshold was estimated at the tongue tip and right thumb (as a body area control site). In the SR-arm of the study, on day one, we estimated sensory baseline perception and repeated tests on day two, after a night of voluntary SR, and on day 3, after a recovery night. In the second arm, same sensory tests were done but no SR was requested. RESULTS: Significantly more sleepiness was observed after SR in comparison with baseline and recovery testing days (P < 0.05). After SR, mechanical pain threshold on the tip of the tongue was significantly lower on day after SR (day 2) and a rebound, higher values, were observed on the third day (P < 0.05); no difference on thumb site. In the control arm, no SR and no significant differences between days were observed for all the variables of interest. CONCLUSIONS: The present results suggest that SR may affect somatosensory perception in the oro-facial area.

Selective Thumb Carpometacarpal Joint Denervation for Painful Arthritis: Clinical Outcomes and Cadaveric Study.

PURPOSE: To determine the innervation pattern to the thumb carpometacarpal (CMC) joint and assess the safety and efficacy of selective joint denervation for the treatment of pain and impairment associated with thumb CMC arthritis. METHODS: Cadaveric dissections were performed in 10 fresh upper extremities to better define the innervation patterns to the CMC joint and guide the surgical approach for CMC joint denervation. Histologic confirmation of candidate nerves was performed with hematoxylin and eosin staining. Results from a series of 12 patients with symptomatic thumb CMC arthritis who underwent selective denervation were retrospectively evaluated to determine the safety and efficacy of this treatment approach. Differences in preoperative and postoperative measurements of grip and key-pinch strength as well as subjective reporting of symptoms were compared. RESULTS: Nerve branches to the thumb CMC joint were found to arise from the lateral antebrachial cutaneous nerve (10 of 10 specimens), the palmar cutaneous branch of the median nerve (7 of 10 specimens), and the radial sensory nerve (4 of 10 specimens). With an average follow-up time of 15 months, 11 of 12 patients (92%) reported complete or near-complete relief of pain. Average improvements in grip and lateral key-pinch strength were 4.1 ± 3.0 kg (18% ± 12% from baseline) and 1.7 ± 0.5 kg (37% ± 11% from baseline), respectively. One patient experienced the onset of new pain consistent with a neuroma that resolved with steroid injection. All patients were released to light activity at 1 week after surgery, and all activity restrictions were lifted by 6 weeks after surgery. CONCLUSIONS: Selective denervation of the CMC joint is an effective approach to treat pain and alleviate impairment associated with CMC arthritis. The procedure is well tolerated, with faster recovery as compared with trapeziectomy. Branches arising from the lateral antebrachial cutaneous nerve, palmar cutaneous branch of the median nerve, and radial sensory nerve can be identified and resected with a single-incision Wagner approach. TYPE OF STUDY/LEVEL OF EVIDENCE: Therapeutic V.

Resting-State Functional Magnetic Resonance Imaging and Probabilistic Diffusion Tensor Imaging Demonstrate That the Greatest Functional and Structural Connectivity in the Hand Motor Homunculus Occurs in the Area of the Thumb.

The primary hand motor region is classically believed to be in the "hand knob" area in the precentral gyrus (PCG). However, hand motor task-based activation is often localized outside this area. The purpose of this study is to investigate the structural and functional connectivity driven by different seed locations corresponding to the little, index, and thumb in the PCG using probabilistic diffusion tractography (PDT) and resting-state functional magnetic resonance imaging (rfMRI). Twelve healthy subjects had three regions of interest (ROIs) placed in the left PCG: lateral to the hand knob (thumb area), within the hand knob (index finger area), and medial to the hand knob (little finger area). Connectivity maps were generated using PDT and rfMRI. Individual and group level analyses were performed. Results show that the greatest hand motor connectivity between both hemispheres was obtained using the ROI positioned just lateral to the hand knob in the PCG (the thumb area). The number of connected voxels in the PCG between the two hemispheres was greatest in the lateral-most ROI (the thumb area): 279 compared with 13 for the medial-most ROI and 9 for the central hand knob ROI. Similarly, the highest white matter connectivity between the two hemispheres resulted from the ROI placed in the lateral portion of PCG (p < 0.003). The maximal functional and structural connectivity of the hand motor area between hemispheres occurs in the thumb area, located laterally at the "hand knob." Thus, this location appears maximal for rfMRI and PDT seeding of the motor area.

Innervation of the interphalangeal joint of the thumb: anatomical study.

We dissected 30 cadaveric thumb interphalangeal joints to delineate the sensory nerve anatomy of its capsule. Four articular branches supplying the interphalangeal joint capsule of the thumb were found in all specimens. Ulnar and radial proper digital nerves provide one palmar capsular nerve branch on their respective sides. Of the two dorsal branches of the radial nerve at the dorsum of the thumb, we observed that each nerve provided one branch to the interphalangeal dorsal capsule. Our findings demonstrate a consistent pattern of innervation and may provide the anatomical basis to the treating surgeon for an effective and safe denervation of the interphalangeal joint of the thumb.