Anatomy of Back of fore arm and dorsum of hand

Back of forearm and dorsum of hand

Dr. Laxman Khanal

Assistant Professor

Department of Human Anatomy

11-11-2016

Objectives

• Learn the skeletal components of posterior forearm and dorsum of hand.

• Identify the seven superficial and five deep muscles of posterior forearm.

• Find the posterior interosseous nerve and artery.

• Find extensor retinaculum and identify thestructures on the dorsal aspect of the wrist.

• Know the boundaries and content of anatomicalsnuff box.

• Different components of dorsum of hand.

Q. Posterior interosseous artery is the branch of.a. Radial artery b. Ulnar arteryc. Brachial artery d. Axillary artery

Q. How many muscles are found on back of forearm?a. 8 b. 10c. 12 d. 7

Q. Posterior interosseous nerve is the branch of.a. Radial nerve b. Ulnar nervec. Median artery d. Axillary nerve

Q. Identify the bone.a.Trapeziumb.Scaphoidc. Triquetral d.Lunate

Q. Which is not true for the marked triangular space?a. It contain radial arteryb. Floor is formed by scaphoidc. Roof contain cephalic veind. Skin area is supplied by ulnar nerve

A

B

C

A

B

C

Median nerve

Ulnar nerve

Axillary nerve

Radial nerve

Musculocutaneous nerve

Introduction

• Forearm is divided into two compartments (flexorand the extensor) by the partition formed byradius, ulna and interosseous membrane.

• Posterior interosseous nerve and artery are chief neurovascular structures of back of forearm.

• Seven superficial and 5 deep group of muscles are present in this compartment.

• Wrist drop is the common sign in paralysis of these muscles.

SLTP

Fracture of distal end of radius

Distal end displaces dorsally

Distal end displaces ventrally

Colle’s or Smith ???

Muscles of extensor compartment of forearm

Superficial group- seven muscles1. Brachioradialis2. Extensor carpi radialis longus3. Extensor carpi radialis brevis4. Extensor digitorum5. Extensor digiti minimi6. Extensor carpi ulnaris7. Anconeus

All the superficial muscles (except three)takes origin fromcommon extensor origin of lat epicondyle.

BR

Ex D

igi

Ex D

igi m

iEx

C U

Superficial muscles1. Brachioradialis2. Ex carpi radialis longus3. Ex carpi radialis brevis4. Ex digitorum5. Ex digiti minimi6. Ex carpi ulnaris7. Anconeus

Extensor retinaculum



Deep group of muscles- 5 in number1. Abductor pollicis longus2. Extensor pollicis longus3. Extensor pollicis brevis4. Extensor indicis5. supinator

None of these muscles cross elbow joint.

1. Abductor pollicis longus

2. Extensor pollicis brevis

3. Extensor pollicis longus

4. Extensor indicis

5. Supinator

Anatomical snuff box

Common interosseous artery

Anterior interosseous arteryposterior interosseous artery

Ulnar artery

• Posterior interosseous nervecomes to the posteriorcompartment through the gapbetween two layers of supinatormuscle.

• Posterior interosseous arterycomes to the posteriorcompartment through the gap inproximal part of IOM.

Anatomical snuff boxThe anatomical snuff box is a surface anatomy feature. Itappears as a triangular depression on the lateral surface ofthe wrist on full extension of the thumb.

Medial boundary- EPLLateral boundary- AbPL +EPBRoof- Cephalic vein and superficial b/o radial nerve.Floor- Scaphoid boneContent- radial artery

Tenderness in the box signifies fracture of scaphoid bone.

Anatomical snuff box, remember !!1 bone- scaphoid1 artery- radial artery1 veincephalic vein1 nerve- superficial b/o radial nerve3 tendons- APL+EPB and EPL

UR

Compartment 1= lat boundary of anatomical snuff box

Compartment 3= medial boundary of anatomical snuff box

Compartment 4= four structures

Extensor retinaculum and its compartments

5th compartment for little finger

Nerve supply of posterior compartment

•All the muscles on the back offorearm are supplied by theposterior interosseous nerve exceptbrachioradialis, extensor carpiradialis longus, and anconeus,which are supplied by the radialnerve directly.

These three muscles ????

Superficial muscle

Common interosseous artery

Post interosseous artery

Ant interosseous artery

Wrist drop: This condition iscaused by a radial nerve injurythat results in paralysis of theextensor muscles in the forearm.

De Quervain’s tenosynovitis:caused by repetitive movementand involve abductor pollicislongus and extensor pollicisbrevis. Movements of the thumbare painful.

Dorsum of hand

Dorsum of hand• Skin• Superficial fascia- contain dorsal venous arch• Superficial branch of radial nerve• Dorsal branch of ulnar nerve• Deep fascia• Extensor tendons

Median nerve

Superficial veins on the dorsalaspect of the hand are oftenvisible and can be accessed fornumerous procedures.

Basilic veinCephalic vein

Cutaneous innervation of dorsum of hand

Radial NerveUlnar Nerve

Median Nerve

Extensor tendons and Dorsal digital expansion

Expansion of tendon of Ext Digitorum over the MP joint which covers dorsal and lateral side of proximal phalanx like a hood.

Dorsal digital expansion

• It is triangular flat sheet of aponeurosis relatedwith the tendon of extensor digitorum (Expansion)Found in dorsum (Dorsal) of proximal phalanx(Digital).

• Also called as extensor hood.

• Provides the insertion of the lumbrical andinterosseous muscles and the extensor indicis andextensor digiti minimi muscles.

• Mallet finger• Baseball finger• Cricketer’s finger

Insertion of extensor tendon to the distal phalanx is torn by forceful blow to the tip of finger.

Conclusion

• Muscles: 7+5

• Nerve: post interosseous nerve

• Artery: post interosseous artery

• Extensor retinaculum: 6 compartment with 9 muscles+1 artery +1 nerve.

• Anatomical snuff box : boundaries and contents.

• Formation of dorsal digital expansion.

Health & Medicine

Anatomy of Back of fore arm and dorsum of hand