Extensor retinaculum of wrist

The extensor retinaculum of wrist is a thick, transverse fibrous band located on the dorsal (back) aspect of the wrist. It represents a direct distal specialization and condensation of the antebrachial fascia.

Attachments

• Laterally, it is firmly anchored to the distal part of the anterior border of the radius.

• Medially, its attachments are to the ulnar styloid process, triquetrum, and pisiform bones. Notably, unlike its radial attachment, the extensor retinaculum does not attach to the main shaft of the distal ulna, only to its styloid process.

Compartments and contents

The extensor retinaculum plays a crucial role in organizing the extensor tendons. It sends fibrous septal partitions deep to attach to the periosteum of the underlying bones, thereby creating six distinct fibro-osseous compartments over the dorsal wrist. Each compartment houses specific extensor tendons along with their synovial sheaths.

Function

Functionally, the extensor retinaculum is essential for the efficient action of the extensor tendons. By holding these tendons closely apposed to the carpal bones, it prevents their bowstringing during wrist and finger extension. This mechanism allows the extensor tendons to glide smoothly underneath it, effectively acting as a dynamic trochlea (pulley system), which optimizes force transmission, particularly during wrist dorsiflexion, while preventing undesirable tendon displacement.