Thenar and Hypothenar Muscle Coverage on the Transverse Carpal Ligament

Background The purpose of the study was to examine the coverage of thenar and hypothenar muscles on the transverse carpal ligament (TCL) in the radioulnar direction through in vivo ultrasound imaging of the carpal tunnel. We hypothesized that the TCL distance covered by the thenar muscle would be greater than that by the hypothenar muscle, and that total muscle coverage on the TCL would be greater than the TCL-alone region. Methods Ultrasound videos of human wrist were collected on 20 healthy subjects. Automated algorithms were used to extract the distal cross-sectional image of the trapezium-hamate level. Manual tracing of the anatomical features was conducted. Results Thenar muscles covered a significantly larger distance (11.9 ± 1.8 mm) as compared with hypothenar muscles (1.7 ± 0.8 mm) (p < 0.001). The TCL covered by thenar and hypothenar muscles was greater than the TCL-alone length (p < 0.001). The thenar and hypothenar muscle coverage on the TCL, as normalized to the total TCL length, was 61.0 ± 7.5%. Conclusions More than 50% of the TCL at the distal carpal tunnel is covered by thenar and hypothenar muscles. Knowledge of muscular attachments to the TCL improves our understanding of carpal tunnel syndrome etiology and can guide carpal tunnel release surgery.

Compression Neuropathy of the Ulnar Nerve due to the Accessory Abductor Digiti Minimi at Guyon’s Canal: A Case Report

Guyon’s canal syndrome is a compression neuropathy of the ulnar nerve that occurs at the wrist. Compression can be caused by many conditions, such as benign tumors, repeated occupational trauma, vascular lesions, fractures of the carpal bones, rheumatoid arthritis and anomalous hypothenar muscle at Guyon's canal. Here, the authors report a case of compression neuropathy of the ulnar nerve by the accessory abductor digiti minimi muscle (AADM), one of the anomalous hypothenar muscles, at Guyon's canal. The case report is accompanied by a literature review.

ABERRANT ABDUCTOR DIGITI MINIMI MUSCLE FOUND DURING OPEN SURGICAL DECOMPRESSION OF THE CARPAL TUNNEL: CASE REPORT. Músculo abductor digiti minimi aberrante hallado durante una cirugía abierta descompresiva del tunel carpiano: reporte de caso

En este artículo reportamos un caso interesante de músculo hipotenar aberrante encontrado durante una descompresión del túnel carpiano. La variante muscular surgía de la fascia antebraquial voloradial, y pasaba sobre la arteria y el nervio ulnar en el canal de Guyón, y se insertaba en la cara ulnar hipotenar. La tensión en el vientre muscular produjo ligera abducción de la quinta articulación metacarpofa-lángica, lo que confirmó que el músculo era abductor digiti minimi aberrante. Observamos asimismo las diferentes variaciones de este músculo y ponemos énfasis en su potencial implicancia clínica. Herein, we present an interesting case of an aberrant hypothenar muscle found during carpal tunnel decompression. The variant muscle arised from the voloradial antebrachial fascia and coursed over the ulnar artery and nerve in the Guyon canal, and inserted into the ulnar aspect of the hypothenar. Tension on the muscle belly provided slight abduction of the fifth metacarpophalangeal joint, which confirmed it to be an aberrant abductor digiti minimi muscle. We also discuss different variations of this muscle and emphasize its potential clinical implications.

Schwannomas of the Upper Extremity

This study presented the clinical characteristics, MRI features and postoperative results of 20 schwannomas in the arms of 13 patients. Twelve tumours had a positive Tinel’s sign, one caused weakness of the wrist and another in Guyon’s canal caused hypothenar muscle atrophy. Of the nine cases which underwent magnetic resonance imaging preoperatively, six were correctly diagnosed as schwannomas. All masses were excised using microsurgical techniques and two transient neurological complications occurred.

Guyon’s Canal Syndrome

An atypical case of Guyon’s canal syndrome is reported. A 40-year-old woman with hypoaesthesia and claw-finger deformity of the little finger, hypothenar muscle atrophy but no first dorsal interosseous muscle atrophy, underwent release of a fibrous band to decompress the ulnar nerve at the deep branch just proximal to the branch to the abductor digiti minimi muscle. The claw-finger deformity recovered 1 week after surgery.