Forearm and Hand

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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). Labeled bones of the forearm and handoka

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). Forearm cross-section: muscles, nerves, and vessels

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

Intrinsic Hand Muscles - Dexterity Drivers

Palmar view of intrinsic hand muscles

  • 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).

Cutaneous innervation of forearm and 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:
    SpaceBoundaries/FloorContents
    Anatomical SnuffboxEPL, EPB/APL; Flr: Scaphoid, Trap.Radial a.
    Carpal TunnelFlexor retinaculum (roof)Median n., 9 flex tendons
  • Fascial Spaces: Thenar, Midpalmar, Parona's.
  • Allen's Test: Tests ulnar/radial patency. Palmar Arches and Arteries of Hand Diagram

⭐ 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'.

Practice Questions: Forearm and Hand

Test your understanding with these related questions

All of the following muscles have dual nerve supply, EXCEPT?

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Flashcards: Forearm and Hand

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In the elbow there are three joints, these being:- _____ Joint- Ulnohumeral Joint- Proximal Radioulnar Joint

TAP TO REVEAL ANSWER

In the elbow there are three joints, these being:- _____ Joint- Ulnohumeral Joint- Proximal Radioulnar Joint

Radiocapitellar

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