Surface Markings of retinacula of Upper Limb

Topic Overview

Flexor Retinaculum

The flexor retinaculum forms the roof of the carpal tunnel, converting the concavity of the carpus into a canal for tendons and the median nerve.

Marking Points

1. Pisiform bone

2. Tubercle of the scaphoid bone

3. Hook of the hamate bone

4. Crest of the trapezium

• The upper border is drawn by joining points (1) and (2); the lower border, by joining points (3) and (4).

• The upper border is concave upwards, and the lower border concave downwards.

• This marking corresponds to the anterior aspect of the wrist where the median nerve passes beneath the retinaculum and can be involved in carpal tunnel syndrome.

Extensor Retinaculum

The extensor retinaculum is an oblique fibrous band, about 2 cm broad, directed downwards and medially across the back of the wrist.

Attachments

• Laterally: To the lower salient part of the anterior border of the radius.

• Medially: To the pisiform and triquetral bones, and to the styloid process of the ulna.

It holds the extensor tendons in position as they cross the wrist and divides them into six compartments. Knowledge of its surface marking helps locate ganglia, tendon pathologies, or sites for synovial sheath injections.