Forearm Anatomy and Joints

Forearm Anatomy

• Radial Head and Ulnar Head: Important for understanding forearm rotation and structure.
• Interosseous Membrane: Connects radius and ulna, providing stability and support.

Bones of Wrist and Hand

• Phalanges Naming: Understanding how phalanges are categorized is crucial for anatomy identification.
• Joint Naming:
  • Wrist Joint: Articulation between radius and carpal bones.
  • MCP Joints: Metacarpophalangeal joints for finger movements.
  • PIP and DIP Joints: Proximal and distal interphalangeal joints, critical for finger flexion.

Fascia and Compartments

• Antebrachial Fascia: Encloses forearm muscles, segregating anterior and posterior compartments.
• Anterior Compartment: Contains flexor and pronator muscles, organized into layers.

Flexor Muscles of Anterior Compartment

• First Layer Muscles: Include pronator teres, flexor carpi radialis (FCR), and flexor carpi ulnaris (FCU).
• Second Layer Muscle: Flexor digitorum superficialis (FDS) - splits at middle phalanges, important for flexing fingers.
• Third Layer Muscle: Flexor digitorum profundus (FDP) - innervates distal phalanges, does not cross elbow.
• Flexor Pollicis Longus (FPL): Important for thumb flexion, travels through carpal tunnel.

Carpal Tunnel

• Contents: Various flexor tendons and median nerve; vital for forearm function.
• Clinical Testing: Evaluates FDS and FDP integrity through movements.

Extensor Muscles of Posterior Compartment

• Layer Orientation: Grouped into superficial and deep layers.
• Key Muscles:
  • Brachioradialis: More visible laterally.
  • Anconeus: Located near the elbow, often concealed.
  • Extensors of the wrist and fingers surround these primary muscles.

Extensor Mechanisms

• Extensor Retinaculum: Stabilizes tendons in the posterior compartment, prevents bowstringing.
• Extensor Hoods: Facilitate extension of fingers via expansions.

Nerve Overview

• Median Nerve: Primarily innervates all anterior forearm muscles, courses between pronator teres heads and carpal tunnel.
• Ulnar Nerve: Innervates 1.5 forearm muscles; courses around medial epicondyle before reaching the hand.
• Radial Nerve: Innervates posterior muscles, divides into superficial and deep branches for cutaneous and muscular functions.

Arterial Supply

• Radial Artery: Supplies lateral muscles of the anterior compartment; courses under the brachioradialis.
• Ulnar Artery: Supplies medial and deep muscles; travels under flexor digitorum superficialis.
• Interosseous Arteries: Anterior and posterior branches, supporting both compartments.

Venous System

• Venae Commitantes: Accompany named arteries, critical for venous return.
• Superficial Veins: Important for drainage and clinical assessment.