A 40-year-old lorry driver develops paraesthesia over the lateral three and a half fingers of the right hand that worsens at night. He also notices weakness and wasting of the thenar eminence. Surface anatomy for carpal tunnel release would place the skin incision along which landmark?

• A Ulnar side of the palmaris longus tendon, in line with the ring finger
• B Radial side of the palmaris longus tendon, in line with the index finger
• C Ulnar border of the thenar crease, in line with the ring finger ray ✓
• D Directly over the flexor carpi radialis tendon

Explanation

The standard open carpal tunnel release incision runs along the ulnar border of the thenar eminence (in line with the axis of the ring finger) to avoid the palmar cutaneous branch of the median nerve (which takes off proximal to the flexor retinaculum and crosses radial to this line) and the recurrent (motor) branch of the median nerve (which turns back radially just distal to the retinaculum). Placing the incision ulnar to the thenar crease protects both these branches while still allowing complete division of the flexor retinaculum.

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

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Written and medically reviewed by the StethoPrep medical team.