Flexor retinaculum of hand is a fibrous band that is present in the flexor aspect of wrist and flexor aspect of the ankle.
Flexor retinaculum of the hand is also called transverse carpal ligament or anterior annular ligament.
It is a strong, fibrous band, that arches over the wrist region and converts the deep groove on the front of the carpal bones into a tunnel. This tunnel is also called as the carpal tunnel.
Flexor retinaculum attached to the scaphoid tubercle and the ridge of the trapezium on radial aspect and to the pisiform and the hook of the hamate on the ulnar side.
Widthwise, it from the distal aspect of the radius to the distal aspect of the base of the third metacarpal.
The retinaculum forms the roof of the carpal tunnel. The ulnar aspect of the flexor retinaculum forms the floor of Guyon’s canal.
Flexor retinaculum has superficial and deep layers. These layers are separated on the radial aspect. The separation contains tendon of flexor carpi radialis.
Note-Guyon canal is also known as the ulnar canal or ulnar tunnel. It allows passage of the ulnar artery and ulnar nerve into the hand. The flexor retinaculum forms the floor of this canal along with hypothenar muscles.
Superficial palmar carpal ligament forms the roof. The space is medially bounded by the pisiform and pisohamate ligament, and laterally by the hook of the hamate more distally
The retinaculum is proximally attached to the deep fascia of the forearm and distally to the palmar aponeurosis
The retinaculum forms the roof of the carpal tunnel. Flexor tendons and the median nerve pass through the canal.
Following tendons pass through this canal
- 4 tendons of Flexor digitorum profundus (four tendons)
- 4 tendons of Flexor digitorum superficialis (four tendons)
- Single tendon of flexor pollicis longus (one tendon)
- Single tendon of flexor carpi radialis
Relations of Flexor Retinaculum
- Inferiorly: contents of the carpal tunnel
- Ulnar artery and nerve (in Guyon’s canal)
- Palmar cutaneous branch of the median and ulnar nerves
- Palmaris longus tendon
- Superficial palmar branch of the radial artery
- Origins of thenar and hypothenar muscles
- Between superficial and deep layers
- flexor carpi radialis
As an anatomical variation, the radial aspect of the flexor retinaculum may be pierced by the median nerve.
Flexor Retinaculum of The Foot
Flexor retinaculum of the foot is also known as laciniate ligament or internal annular ligament.
It extends from the tibial malleolus above to the margin of the calcaneus below as shown in the image. It converts a series of bony grooves into canals for passage of the tendons of the flexor muscles, posterior tibial vessels, and posterior tibial nerve.
The flexor tendons are from the medial side to lateral
- Tendon of the tibialis posterior
- Tendon of the flexor digitorum longus
- Tendon of the Flexor hallucis longus.
Just like its hand counterpart, it is continuous with the deep fascia of the leg proximally and plantar aponeurosis distally.