e posters of 2023-24 batch- cubital fossa

 CHAPTER 9

BACK OF FOREARM

Back of forearm (extensor) muscles are arranged in to superficial and deep groups:

Superficial group:

1. Brachioradialis
2. Extensor carpi radialis longus
3. Extensor carpi radialis brevis
4. Extensor digitorum
5. Extensor digiti minimi
6. Extensor carpi ulnaris
7. Anconeus

Brachio radialis & Extensor carpi radialis longus :

Common origin:

From lateral epicondyle of humerus

Lateral supracondylar ridge

Lateral intermuscular septum

Insertion of brachioradialis:

Styloid process of radius

Extensor carpi radialis longus – Insertion:

Dorsal surface of base of 2^nd metacarpal bone

Extensor carpi radialis brevis:

Origin:

Lateral  epicondyle of humerus

Radial collateral ligament of elbow joint

Insertion:

Dorsal surface of the bases of 2,3 metacarpal bones

Extensor digitorum:

Origin:

From lateral epicondyle of humerus

Insertion:

Divides into 4 digital tendons for medial 4 fingers, and inserted into the dorsal digital expansion.

Extensor digiti minimi:

Origin:

Common extensor origin

Insertion:

Dorsal digital expansion of little figure.

Extensor carpi ulnaris:

Origin: from common extensor origin and from the posterior border of ulna.

Insertion: Base of fifth metacarpal bone

Anconeus:

Origin: 

From lateral epicondyle of humerus

Insertion:

Lateral surface of the olecranon process

upper ¾ of the posterior surface of the ulna

Supinator:

Origin:

Superficial fibres take origin from:

• lateral epicondyle
• radial collateral ligament
• annular ligament

Deep fibres from:

Anterior part of lateral surface of radius

In between anterior and posterior oblique line

Nerve supply of superficial group:

Brachioradialis, extensor carpi radialis longus – Radial nerve

All the other muscles – Posterior interosseous nerve

Deep Group:

1. Abductor Pollicis Longus

Origin:

Posterior surface of both radius and ulna

From intervening interosseous membrane

Insertion:

Radial side of the base of metacarpal bone

Extensor pollicis brevis:

Origin:

Posterior surface of radius below the abductor pollicis longus

Insertion: Dorsal surface of the base of the proximal phalanx of thumb

Extensor pollicis longus:

Origin: Posterior surface of shaft of ulna below the abductor pollicis longus.

Insertion: Base of distal phalanx of thumb

Extensor indicis:

Origin: Posterior surface of ulna distal to extensor pollicis longus

Insertion: Dorsal digital expansion of index finger

Nerve Supply of Deep group: Posterior interosseous nerve

Anatomical snuff box:

It is a triangular depression on the radial side of the wrist

Boundaries:

Laterally – tendons of abductor pollicis longus and extensor pollicis brevis

Medially – tendon of extensor pollicis longus

Roof – skin and fasciae

          Beginning of cephalic vein

          Superficial branch of radial nerve

Floor – styloid process of radius, scaphoid, trapezium, base of 1 metacarpal bone.

Content – Radial artery

Extensor Retinaculum:

It is the thickening of deep fascia

Situation – Dorsal surface of the wrist, obliquely placed

Attachments:

Laterally – anterior border of the radius above the styloid process

Medially – pisiform and triquetral bones

Structures beneath the extensor retinaculum:

Beneath the retinaculum, six osseo fascial compartments for nine tendons are present

From lateral to medial side following tendons :

1st  Compartment:

 Abductor pollicis longus

Extensor pollicis brevis

2^nd Compartment:

          Extensor carpi radialis longus

Extensor carpi radialis brevis

3^rd compartment:

Extensor pollicis longus

4th compartment:

          Four tendons of extensor digitorum and the tendon of extensor indicis

5^th compartment:

Extensor digiti minimi

6th Compartment:

Extensor carpi ulnaris