Topic Overview

Back of Forearm and Hand

Surface Landmarks

• Olecranon Process:

  • Prominent bony point of elbow; attachment of triceps tendon.

  • In extension → lies in line with medial and lateral epicondyles.

• Posterior Border of Ulna:

  • Subcutaneous throughout; forms a palpable ridge along medial side of back of forearm.

• Styloid Processes:

  • Radial styloid – more distal and lateral; palpable at base of anatomical snuffbox.

  • Ulnar styloid – smaller and lies higher.

• Dorsal Venous Network:

  • Clearly visible superficial veins on dorsum of hand → drains into cephalic (lateral) and basilic (medial) veins.

• Tendons at Wrist During Extension:

  • Seen as distinct ridges:

    • Lateral: Extensor pollicis brevis and abductor pollicis longus.

    • Middle: Extensor digitorum and extensor indicis.

    • Medial: Extensor carpi ulnaris.

Dorsum of the Hand

Skin and Superficial Fascia

• Skin → thin, loose, and freely movable → allows expansion during grip.

• Contains dorsal venous arch, cutaneous nerves, and superficial lymphatics.

Deep Fascia

• Thinner than in palm.

• Sends septa between extensor tendons forming dorsal compartments beneath the extensor retinaculum.

Extensor Tendons

• Spread out into dorsal digital expansions (extensor hoods) over the MCP joints.

• Each expansion receives slips from lumbricals and interossei → coordinates finger extension.

Clinical Note

• Synovial sheath infections on dorsum are rare but may follow traumatic punctures.

• Tenosynovitis in these sheaths restricts wrist and finger extension.

🩻 Anatomical Snuffbox

Definition

A triangular depression on the lateral side of wrist seen when thumb is fully extended.

Boundaries

Clinical Anatomy of Snuffbox

• Radial pulse felt here (in distal part).

• Tenderness in scaphoid fracture (classical sign).

• Radial artery puncture or cannulation site.

• Superficial branch of radial nerve lies superficially → can be injured in snuffbox trauma or surgery.

🩹 Extensor Retinaculum

Definition

A thickened part of deep fascia that holds extensor tendons in place at the back of wrist — prevents “bow-stringing” during extension.

Attachments

• Lateral: Lower end of radius.

• Medial: Pisiform and triquetral bones.

Compartments Beneath Extensor Retinaculum

Relations

• Superficial: Skin and superficial fascia with dorsal veins.

• Deep: Carpal bones.

• Each tendon is enclosed in a synovial sheath for frictionless movement.

Functions

• Maintains alignment of extensor tendons during wrist motion.

• Prevents tendon displacement during extension and abduction.

Clinical Anatomy

• Tenosynovitis: Common in first dorsal compartment → De Quervain’s disease.

  • Pain and tenderness near lateral wrist.

  • Involves tendons of abductor pollicis longus and extensor pollicis brevis.

• Triggering or snapping may occur due to stenosis of tendon sheath.

• Ganglion cysts may arise from dorsal tendon sheaths.

🧠 Dissection of Back of Forearm and Hand

Steps

1. Place limb prone (palm down). Make longitudinal incisions along the midline of posterior forearm and dorsum of hand.

2. Reflect skin and superficial fascia → identify superficial veins (cephalic, basilic) and cutaneous nerves (posterior & lateral cutaneous nerves of forearm).

3. Remove deep fascia → identify extensor retinaculum near wrist.

4. Under it, locate six dorsal compartments and their tendons:

   • Compartment 1 (lateral): Abductor pollicis longus, Extensor pollicis brevis.

   • Compartment 2: ECRL, ECRB.

   • Compartment 3: EPL (forms medial boundary of snuffbox).

   • Compartment 4: Extensor digitorum, Extensor indicis.

   • Compartment 5: Extensor digiti minimi.

   • Compartment 6: Extensor carpi ulnaris.

5. Identify radial artery in anatomical snuffbox and superficial branch of radial nerve.

6. Trace extensor tendons to their expansions over MCP joints and phalanges