In a high radial nerve palsy at the level of the spiral groove of the humerus, which function is typically preserved compared to a radial nerve injury at the axillary level?

• A Wrist extension by extensor carpi radialis longus
• B Finger extension by extensor digitorum
• C Thumb abduction by abductor pollicis longus
• D Elbow extension by triceps (long and medial heads) and anconeus ✓

Explanation

The branches to the long and medial heads of triceps arise from the radial nerve in the axilla or proximal arm, before the nerve enters the spiral groove. Therefore, a lesion at the spiral groove level spares triceps function (elbow extension preserved) and anconeus. The branches to the lateral and medial heads of triceps arise at variable levels but the contribution to elbow extension is largely preserved. In contrast, an axillary-level radial nerve injury (e.g., crutch palsy) causes complete triceps paralysis in addition to wrist drop. Wrist extension, finger extension, and thumb abduction are all lost with spiral groove injuries.

Reference: BD Chaurasia's Human Anatomy, 8th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.