Wrist Retinacula & Anat. Snuff Box

8/3/2019 Wrist Retinacula & Anat. Snuff Box

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FLEXOR RETINACULUM

This is the thickened part of the deep fascia of the forearm located on the anterior aspect

of the wrist. It overlies the flexor tendons in their synovial sheaths.

It is also called the transverse carpal ligament and measures about 2-3 cm in length and

width.

This dense fibrous band unites the ends of the arch of carpal bones and thus converts the archinto an osteofibrous tunnel called the carpal tunnel, with the retinaculum being the roof of

the tunnel.

ATTACHMENTS

- Medial Attachment: pisiform and hook of hamate

- Lateral Attachment is by two laminae or layers. Superficial lamina attaches to the

tubercle of the scaphoid and tubercle of trapezium. Deep lamina attaches to the

trapezium posterior to the groove for the flexor carpi radialis.

RELATIONS

- SUPERFICIAL RELATIONS:

Thenar and hypothenar muscles: which gain partial origin from the flexor

retinaculum.

Ulnar nerve

Ulnar blood vessels

Palmar cutaneous branches of median and ulnar nerves

Tendon of Palmaris longus.

- DEEP RELATIONS: These are structures passing through the carpal tunnel.

Tendon of flexor digitorum superficialis and flexor digitorum profundus and their

common synovial sheath (ulnar bursa).

Tendon of flexor pollicis longus and its synovial sheath (radial bursa)

Median nerve

Tendon of flexor carpi radialis and its synovial sheath

PROXIMALLY, the flexor retinaculum is continuous with the deep fascia of the forearm.

DISTALLY, the retinaculum is continuous with the palmar aponeurosis of the hand. Laterally and

medially, it is continuous with the extensor retinaculum on the dorsum of the wrist.

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FUNCTIONS OF THE FLEXOR RETINACULUM

It maintains the arch of the carpus, thus maintaining the anterior concavity of the palm.

Acts as a pulley due to the presence of the synovial sheaths. That is, together with the

synovial sheaths, the flexor retinaculum aids in the lubricating the movement of the

tendons during flexion.

It acts as a restraining band holding the flexor tendons in place and preventing them

from bowing out during flexion of the wrist joint.

It protects the median nerve.

CLINICAL CORRELATIONS

Carpal Tunnel Syndrome

- A common disorder that causes pain and interferes with the use of the hand.

- Caused by pressure on the median nerve in the carpal tunnel due to (i) reduction in the

size of the carpal tunnel or (ii) more commonly, increase in size of some of the structures

(or their coverings) that pass through the tunnel (e.g., inflammation of the synovial

sheaths).

- Compression on the median nerve will lead to pain, weakness in the action and wasting

of the thenar muscles and there will also be loss of sensation around the radial two-third

digits.

- The pressure caused by inflammation of the synovial sheaths can be relieved by incision

of the flexor retinaculum.

- It should be noted that during carpal tunnel syndrome there is no loss of sensation over

the skin of the thenar eminence, this is due to the fact that the median nerve has already

given off a palmar cutaneous branch before entering the carpal tunnel.

EXTENSORRETINACULUM

It is a thickened part of the deep fascia of the forearm located on the dorsal aspect of the

wrist. It overlies the extensor tendons in their synovial sheaths.

It is also called the dorsal carpal ligament.

ATTACHMENTS

- Laterally, the retinaculum is attached to the anterolateral border of the radius. From here

the fibers run medially and distally to be attached to the styloid process of the ulna and

to the triquetral and pisiform bones.

PROXIMALLY, the extensor retinaculum is continuous with the deep fascia of the forearm.

DISTALLY, it is continuous with the deep fascia on the dorsum of the hand. Medially andlaterally it is continuous with the flexor retinaculum on the ventral aspect of the wrist.

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The fibres of the retinaculum also send deep septa between the group of extensor tendons to

attach to the 4 ridges on the distal end of the radius and to the head of the ulna.

These septa divide the space between the extensor retinaculum and the underlying bones

(radius and ulna) into 6 compartments for the passage of the extensor tendons in their synovial

sheaths. The compartments are numbered in lateral to medial sequence.

RELATIONS (COMPARTMENTS)

COMPARTMENT STRUCTURES

I Abductor pollicis longus

Extensor pollicis brevis

II Extensor carpi radialis longus

Extensor carpi radilis brevis

III Extensor pollicis longus

IV Extensor digitorum

Extensor indicis

Posterior interosseus nerve

Anterior interosseus artery

V Extensor digiti minimi

VI Extensor carpi ulnaris

FUNCTIONS

- Acts as a pulley due to the presence of the synovial sheaths.

- Hold the extensor tendons in place.

CLINICAL CORRELATIONS

- Extensor Retinaculm Graft for Chronic Boxers Knuckle: Boxer's knuckle is a tear of

the metacarpophalangeal (MCP) joint capsule that occurs while punching. Because of the

nature of boxing, boxer's knuckle tends to be a chronic condition and often is associated

with disruption of the sagittal fibres of the extensor retinaculum. Upon healing/repair of

the damaged capsule (of the MCP joint) and sagittal bands, scars are formed which

impairs flexion of the MCP joint and causes pain to the suferer. Surgical treatment

involves removal of the scar tissue and suturing an oval-shaped part of the extensor

retinaculum in the defect of the capsule/sagittal band.

ANATOMICALSNUFFBOX

It is a triangular depression on the dorsal aspect of the root of the thumb especially when the

thumb is fully extended.

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BOUNDARIES

Anterior Abductor pollicis longus and extensor pollicis brevismuscles

Posterior Extensor pollicis longus muscle

Proximal Styloid process ofradius

Distal Base of 1stmetacarpal bone and part of the trapezium

Floor Scaphoid and trapezium

STRUCTURES CROSSING THE ANATOMICAL SNUFF BOX

- Radial artery: the radial pulse can be detected here

- Extensor carpi radialis longus

- The cephalic vein: arises within the anatomical snuffbox,

- Dorsal cutaneous branch of the radial nerve: can be palpated by stroking along the

extensor pollicis longus with the dorsal aspect of a fingernail.

CLINICAL CORRELATION

- Fracture of the scaphoid: more frequent in the event of a fall. This is understandable

as the scaphoid is a small, oddly shaped bone whose purpose is to facilitate mobility

rather than confer stability to the wrist joint.

Blood enters the scaphoid distally. Consequently, in the event of a fracture the proximal

segment of the scaphoid will be devoid of a vascular supply, and willif action is not

takenavascularly necrose within a sufferer's snuffbox.

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http://download.videohelp.com/vitualis/med/mmforarm.htm#Abductor_pollicis_longus_musclehttp://download.videohelp.com/vitualis/med/mmforarm.htm#Extensor_pollicis_brevis_musclehttp://download.videohelp.com/vitualis/med/mmforarm.htm#Extensor_pollicis_longus_musclehttp://download.videohelp.com/vitualis/med/uppbone.htm#Radiushttp://download.videohelp.com/vitualis/med/uppbone.htm#Metacarpushttp://download.videohelp.com/vitualis/med/uppbone.htm#Carpushttp://download.videohelp.com/vitualis/med/uppbone.htm#Carpushttp://download.videohelp.com/vitualis/med/uppbone.htm#Carpushttp://en.wikipedia.org/wiki/Cephalic_veinhttp://en.wikipedia.org/wiki/Necrosishttp://download.videohelp.com/vitualis/med/mmforarm.htm#Extensor_pollicis_brevis_musclehttp://download.videohelp.com/vitualis/med/mmforarm.htm#Extensor_pollicis_longus_musclehttp://download.videohelp.com/vitualis/med/uppbone.htm#Radiushttp://download.videohelp.com/vitualis/med/uppbone.htm#Metacarpushttp://download.videohelp.com/vitualis/med/uppbone.htm#Carpushttp://download.videohelp.com/vitualis/med/uppbone.htm#Carpushttp://download.videohelp.com/vitualis/med/uppbone.htm#Carpushttp://en.wikipedia.org/wiki/Cephalic_veinhttp://en.wikipedia.org/wiki/Necrosishttp://download.videohelp.com/vitualis/med/mmforarm.htm#Abductor_pollicis_longus_muscle

Wrist Retinacula & Anat. Snuff Box

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