What is the flexor retinaculum?

The flexor retinaculum is a strong fibrous band on the palmar aspect of the wrist that converts the carpal groove into the carpal tunnel and holds flexor tendons and the median nerve in place.

Where is the flexor retinaculum located?

It is located on the anterior (palmar) surface of the wrist, stretching between the carpal bones on the radial and ulnar sides.

What are the attachments of the flexor retinaculum?

Laterally it attaches to the tubercle of scaphoid and crest of trapezium, and medially to the pisiform and hook of hamate.

Which structures pass deep to the flexor retinaculum?

The median nerve and nine flexor tendons (four flexor digitorum superficialis, four flexor digitorum profundus, and one flexor pollicis longus) pass deep to it.

Which structures pass superficial to the flexor retinaculum?

The ulnar nerve, ulnar artery, and palmar cutaneous branch of the median nerve pass superficial to the flexor retinaculum.

What is the main function of the flexor retinaculum?

Its main function is to prevent bowstringing of flexor tendons during wrist and finger flexion and to maintain mechanical efficiency.

How is the flexor retinaculum related to carpal tunnel syndrome?

Thickening or increased pressure beneath the flexor retinaculum compresses the median nerve, leading to carpal tunnel syndrome.

Why is palmar skin sensation spared in carpal tunnel syndrome?

Because the palmar cutaneous branch of the median nerve passes superficial to the flexor retinaculum and is not compressed.

Does the ulnar nerve pass through the carpal tunnel?

No, the ulnar nerve passes superficial to the flexor retinaculum through Guyon’s canal.

What happens during surgical release of the flexor retinaculum?

The retinaculum is cut to increase the volume of the carpal tunnel and relieve pressure on the median nerve.

Flexor Retinaculum Anatomy Structure Attachments Functions and Clinical Importance

Flexor Retinaculum (Transverse Carpal Ligament) — Detailed Anatomy

Definition

The flexor retinaculum is a strong fibrous band on the palmar aspect of the wrist. It spans the concavity of the carpal bones and converts the carpal groove into the carpal tunnel, retaining the long flexor tendons and neurovascular structures in position.

Location & Extent

Situated across the anterior (palmar) wrist
Forms the roof of the carpal tunnel
Lies superficial to the carpal bones and deep to palmar skin and fascia

Attachments

Medial (ulnar) side

Pisiform
Hook of hamate

Lateral (radial) side

Tubercle of scaphoid
Crest/tubercle of trapezium

Structure & Relations

Thickened part of deep fascia of the forearm
Continuous proximally with deep fascia
Gives attachment to thenar and hypothenar muscles
Superficial to flexor tendons and median nerve
Palmar aponeurosis lies superficial to it

Contents Beneath the Flexor Retinaculum (Carpal Tunnel Contents)

Within the carpal tunnel (deep to retinaculum):

Median nerve
9 flexor tendons:

* 4 tendons of flexor digitorum superficialis

* 4 tendons of flexor digitorum profundus

* 1 tendon of flexor pollicis longus

Outside the tunnel but related:

Flexor carpi radialis tendon (in its own compartment)
Ulnar nerve and ulnar artery (pass superficial to retinaculum through Guyon’s canal)
Palmar cutaneous branch of median nerve (superficial)

Functions

Prevents bowstringing of flexor tendons during wrist flexion
Maintains mechanical efficiency of finger flexors
Forms a protective fibro-osseous tunnel for median nerve and tendons

Clinical Importance

Carpal Tunnel Syndrome

Compression of median nerve beneath flexor retinaculum
Symptoms: pain, numbness, tingling in thumb, index, middle, and lateral half of ring finger; thenar muscle weakness

Surgical Relevance

Flexor retinaculum release relieves median nerve compression
Care taken to avoid injury to:

* Recurrent branch of median nerve

* Superficial palmar arch

Applied Anatomy Points (Exam-Oriented)

Median nerve lies deep to retinaculum, palmar cutaneous branch is superficial
Ulnar nerve is not compressed in carpal tunnel syndrome
Thickening or edema of retinaculum worsens tunnel pressure