Forearm and Hand

Forearm & Hand Bones & Joints - Framework Finesse

• Distal Forearm Bones:
  • Radius: Styloid process, Lister’s tubercle.
  • Ulna: Head, styloid process.
• Carpal Bones (8): 📌 'So Long To Pinky, Here Comes The Thumb'
  • Proximal: Scaphoid, Lunate, Triquetrum, Pisiform.
  • Distal: Trapezium, Trapezoid, Capitate, Hamate.

  ⭐ Scaphoid: Most fractured carpal; FOOSH injury; risk of avascular necrosis (retrograde supply).

• Hand Skeleton:
  • Metacarpals (5): Base, shaft, head.
  • Phalanges (14): Proximal, middle (II-V), distal.
• Key Joints:
  • Distal Radioulnar (DRUJ).
  • Radiocarpal (Wrist).
  • Midcarpal.
  • Carpometacarpal (CMC); Thumb (saddle).
  • Metacarpophalangeal (MCP).
  • Interphalangeal (PIP, DIP). oka

Forearm Muscle Compartments - Movers & Shakers

• Anterior (Flexor-Pronator): Origin: Common Flexor Origin (CFO) from medial epicondyle.
  • Innervation: Median N. (most); Ulnar N. (FCU, medial FDP).
  • Superficial: Pronator Teres, FCR, Palmaris Longus, FCU, FDS. 📌 Mnemonic: "Pass Fail Pass Fail Students".
  • Deep: FDP, FPL, Pronator Quadratus.
• Posterior (Extensor-Supinator): Origin: Common Extensor Origin (CEO) from lateral epicondyle.
  • Innervation: Radial N. (all).
  • Superficial: Brachioradialis, ECRL, ECRB, ED, EDM, ECU.
  • Deep: Supinator, APL, EPB, EPL, EI.
• Retinacula: Flexor & Extensor (bind tendons).

⭐ All muscles of the posterior compartment of the forearm are supplied by the radial nerve or its branches.

Intrinsic Hand Muscles - Dexterity Drivers

• Thenar (Median N.): APB, FPB, Opponens Pollicis (thumb opposition).
• Hypothenar (Ulnar N.): ADM, FDM, Opponens Digiti Minimi (5th digit movement).
• Lumbricals: 1&2 (Median N.), 3&4 (Ulnar N.); Flex MCP, extend IP joints.
• Interossei (Ulnar N.): Palmar ADduct (📌PAD), Dorsal ABduct (📌DAB).
• Adductor Pollicis (Ulnar N.): Thumb adduction. 📌 LOAF (Median N. hand muscles): Lumbricals 1&2, Opponens Pollicis, Abductor Pollicis Brevis, Flexor Pollicis Brevis (superficial head).

⭐ The ulnar nerve supplies most intrinsic muscles of the hand (except LOAF muscles & often FPB deep head).

Forearm & Hand Nerves - Command Central

• Median Nerve: Travels through carpal tunnel; supplies thenar muscles (recurrent branch) & lateral 2 lumbricals. Sensory to lateral 3.5 digits. Injury: Carpal Tunnel Syndrome, Ape Hand deformity.
• Ulnar Nerve: Passes posterior to medial epicondyle, through Guyon's canal. Supplies most intrinsic hand muscles, FCU, medial FDP. Sensory to medial 1.5 digits. Injury: Claw Hand, Ulnar paradox.
• Radial Nerve: In spiral groove; deep branch (PIN) for extensors, superficial for sensation. Injury: Wrist Drop, Saturday Night Palsy.

📌 Mnemonic: DR CUMA (Drop wrist-Radial, Ape hand-Median, Ulnar-Claw hand).

⭐ Sensory innervation of the nail beds of the index finger is by the median nerve, and the little finger by the ulnar nerve.

Forearm & Hand Vasculature & Spaces - Lifelines & Landmarks

• Arteries: Radial & Ulnar a. supply forearm/hand.
  • Superficial Palmar Arch (Ulnar a. > Radial a.)
  • Deep Palmar Arch (Radial a. > Ulnar a.)
  • Digital arteries.
• Veins: Cephalic (lateral), Basilic (medial), Dorsal venous network.
• Key Spaces & Contents:

  Space	Boundaries/Floor	Contents
  Anatomical Snuffbox	EPL, EPB/APL; Flr: Scaphoid, Trap.	Radial a.
  Carpal Tunnel	Flexor retinaculum (roof)	Median n., 9 flex tendons

• Fascial Spaces: Thenar, Midpalmar, Parona's.
• Allen's Test: Tests ulnar/radial patency.

⭐ The radial artery is found in the floor of the anatomical snuffbox.

High‑Yield Points - ⚡ Biggest Takeaways

• Median nerve injury at wrist causes Ape Hand deformity; at elbow, Point of Benediction.
• Ulnar nerve injury leads to Claw Hand; vulnerable at medial epicondyle or Guyon's canal.
• Radial nerve injury in spiral groove results in Wrist Drop (e.g., Saturday night palsy).
• Scaphoid fracture is the most common carpal bone fracture, risking avascular necrosis.
• Anatomical snuffbox (EPL, EPB, APL) contains radial artery and scaphoid bone.
• Carpal Tunnel Syndrome involves median nerve compression, with positive Phalen's/Tinel's signs.
• Colles' fracture (distal radius) causes dinner fork deformity; Smith's is reverse Colles'.