Lecture Details[]
John Crock; Week 4 MED1022; Anatomy
Lecture Content[]
Palmar aponeurosis is triangular sheet of fibrous tissue, apex attached to palmaris longus. Four slips split to merge with fibrous flexor sheets of 4 digits. Deep slips pass to metacarpals. Gaps between slips are tunnels where neurovascular bundles enter the digits and are important for nerve block injections. Dupuytren's contracture is fixed flexion of the hand due to thickening of the fibrous fascia, common in older men, alcoholics, diabetes and epilepsy.
Flexor retinaculum forms the roof of the carpal tunnel, attached to the bony prominences of the carpals (pisiform, hook of hamate, tubercle of trapezium and tubercle of scaphoid. Through the tunnel is the 4 deep and superficial tendons and the 1 thumb tendon as well as median nerve. Carpal tunnel syndrome is common, there is parasthesia in median nerve distribution, weakness of muscles supplied by the median nerve.
Tendinous and synovial sheaths of the hand extend into wrist, variable communication with thumb sheath, continuous with little finger sheath. Sheaths are not continuous with 2-4 because lumbricals occur at junction. There are equivalents for extensor tendons.
Intrinsic muscles of the hands are thenar (abductor, flexor and opponens; deep adductor (two heads). Median nerve supplies these muscles, ulnar supplies the adductor. Froment's test tests the ulnar nerve by holding paper against the hand against resistance. Hypothenar abductor, flexor, opponens have same pattern as thenars (from attachment of retinaculum/retinaculum itself.
Lumbricals are slender muscles arising from FDP in the palm, 1+2 are median nerve, 3+4 are ulnar nerve. They pass around the radial side of each digit into the dorsal digital expansion. They extend at the IP joints due to insertion of digital expansion of extensor tendon, if the IP joints are extended the flex the MP joints.
Palmar interossei are small unipennate muscles which arise from only 1 metacarpal, are adductors. Dorsal interossei are larger, bipennate from two adjacent metacarpals. They are dorsal abductors and first to waste in T1 lesions. Both also flex MP joints and extend IP joints. They act in synergy with long tendons of extensor digitorum to extend IP joints fully. Supplied by deep branch of ulnar nerve.
Wrist is articulated with radius and articular disc (not ulna directly), scaphoid and lunate with radius, triquetrial with disc. 1st CMC joint is saddle- range of movement, lax capsule, several planes of movement. 2-5th has joints held together with deep transverse metacarpal ligaments- dorsal, palmar and interosseous ligmaent. Slight gliding of joint but a lot less that 1st. More gliding in 4/5th. MCP joints have only flex/ext, abd/add, cannot abduct in flexion due to collateral ligaments being taut and interosseous muscles are disadvantaged.
Sensory- median nerve supplies up to 1/2 of 3rd digit, ulnar the rest on palmar surface. On dorsum, ulnar supplies up to 2nd digit, median same from tip to IP joint then radial the rest.
Power grip is firm- long flexors, slight extension at wrist, hand is one unit, skill in wrist and forearm. Precision is with tips of fingers/thumb and intrinsic muscles. Hook is used for carrying objects.