Opponens Digiti Minimi
Original Editor - Agoro Bukola Zainab
DescriptionOpponens digit minimi (ODM) is an intrinsic muscle of the hand. It's a triangular muscle that extends between the hamate bone (carpal bone) and the 5th metacarpal bone. It forms the hypothenar muscle group together with the abductor digiti minimi and flexor digit minimi brevis, based on the medial side of the palm (hypothenar eminence). These muscles act together in moving the little finger. The opponens digiti minimi is responsible for flexion, lateral rotation and opposition of the little finger.
Hook of hamate and flexor retinaculum
Inserts into the medial border of 5th metacarpal bone
Blood supply is by the deep palmar branch of ulnar artery and deep palmar arch, which is the terminal branch of the radial artery
Opponens digiti minimi acts to oppose the little finger to the thumb by:
- Flexion of the fifth metacarpal
- Lateral rotation of the carpometacarpal joint of the fifth digit
- Lateral rotation of the metacarpophalangeal joint of the fifth digit
The oponones digiti minimi which forms part of the intrinsic muscles provides fine motor movement of the hand. This is usually seen when trying to grip round or irregular objects such as a ball. The ulnar nerve which supplies the hypothenar muscles including opponens digiti minimi passes through the hook of hamate and pisiform bone (Guyon's canal), compromise to the nerve at this point leads to atrophy of the ODM with a resulting weakness in moving the 5th finger. There's also numbness, tingling, and pain in the 4th and 5th finger that comes with ulnar nerve entrapment. See also Cyclist palsy.
Assessment is done by palpating for abnormal tenderness at the base of the thenar eminence. Check for muscle weakness by asking the patient to oppose the 5th finger to the thumb with added resistance.
- Moore KL, Dalley AF. Clinically oriented anatomy. Wolters kluwer india Pvt Ltd; 2018 Jul 12.
- Adrian R. Opponens digiti minimi muscle of hand [Internet]. 2020. Available from: https://www.kenhub.com/en/library/anatomy/opponens-digiti-minimi-muscle
- Nguyen J, Duong H. Anatomy, Shoulder and Upper Limb, Hand Hypothenar Eminence. StatPearls [Internet]. 2020 Aug 13.
- Muscle Testing: Opponens Digiti Minimi. Available from: https://www.youtube.com/watch?v=SUDsq7iqsAc [last accessed 23/10/2020]