An accessory abductor digiti minimi as possible risk factor of the median and ulnar nerves compression / Músculo abductor digiti minimi accesorio como posible factor de riesgo de la compresión de los nervios mediano y ulnar

SUMMARY: During routine dissection of a left upper limb of a 68-year-old male human cadaver, an unusual muscle was observed originating from the radius and flexor retinaculum, and continued in the hypothenar region with the muscle belly of the abductor digiti minimi. We checked that it was an accessory abductor digiti minimi (ADM). Its muscular belly was in close relation to the median and ulnar nerves. We review the literature regarding such muscle variations and discuss the potential for compression of the median and ulnar nerves. Although the accessory ADM is usually asymptomatic and only rarely results in nerve compression, it should be taken into account by surgeons when establishing a differential diagnosis in the compression neuropathies of the median and ulnar nerves. An ultrasound scanning can help establish the differential diagnosis.

RESUMEN: Durante la disección de rutina de un miembro superior izquierdo de un cadáver humano masculino de 68 años, se observó un músculo inusual que se originaba en el radio y el retináculo flexor del carpo, y continuuaba en la región hipotenar con el vientre muscular del abductor digiti minimi manus. Verificamos que se trataba del músculo abductor digiti minimi accessorius (ADMA). Su vientre muscular se encontraba en estrecha relación con los nervios mediano y ulnar. Revisamos la literatura sobre variaciones musculares y discutimos la potencial compresión de los nervios mediano y ulnar. Aunque el ADMA suele ser asintomático y rara vez produce compresión nerviosa, los cirujanos deben tenerlo en cuenta al establecer un diagnóstico diferencial en las neuropatías de compresión de los nervios mediano y ulnar. Una ecografía puede ayudar a establecer el diagnóstico diferencial.

An Anatomic Variation of the Accessory Abductor Digiti Minimi Muscle / 체질인류학회지

Accessory muscles passing through Guyon's canal are common; the most common anomalous muscle at Guyon's canal is the accessory abductor digiti minimi muscle (AADM). The aim of this study was to demonstrate and describe the gross anatomy of an anatomic variant of the AADM relative to the surrounding structures. The AADM was found in the left forearm and hand of a 61-year-old male cadaver during dissection in a gross anatomy course. It was observed by focusing on the shape, the course, and its relationship with the surrounding structures. The AADM originated as muscle fibers from the antebrachial fascia. It coursed downward in the distal forearm and crossed the ulnar nerve and artery obliquely at Guyon's canal. The AADM narrowed and became a long tendon in the hypothenar region. The abductor digiti minimi muscle was partly attached to the tendon of the AADM, running along the tendon. The tendon of the AADM inserted into the ulnar side of head of the fifth metacarpal bone. The AADM was innervated by several twigs from the ulnar nerve. We reported herein another variant of the AADM at Guyon's canal, which may be helpful to surgeons performing diagnoses and surgical procedures.