Week 11 Hand and fingers Flashcards
function of CMC joints: fingers
- allow small amounts of flexion coupled with slight rotation (10-20 degrees)
- enhances 增強 opposition of ulnar side of hand for power grip 以獲得力量握力
movement of CMC joint thumb
1. flexion/ extension, abduction/ adduction
conjunct rotation:
flexion accompanied by medial rotation
extension accompanied by lateral rotation
2. opposition
- metacarpal abducts, then flexes and adducts
- muscular and ligamentous forces help to guide metacarpal
- conjunct medial rotation (at least 45-60 degrees)
full opposition/ abduction = close packed position
bone stability of MCP joints
- poor stability, good movement (large convex MC head 180 degrees, shallow concave surface of proximal phalanx 20 degrees)
- MCPs form distal transverse arch of the hand
stability is vital to hand function
movements of MCP joint
- flexion
- approx 90 degrees
- range increases towards the ulnar side of hand
- concave phalanx on convex MC hand = rolls and slides in same direction - extension
- variable, around 0 degrees
- significance of hyperextension
ligaments of MCP joints
- collateral ligaments
- proper: cord-like 繩狀
- accessory: fan shape
- tension in collateral ligaments increases with F due to curvature 彎曲 of metacarpal head
- flexion: prevents unwanted abduction of fingers during gripping
- extension: collateral ligs are lax –> permit abduction of fingers by interossei - volar plate
- fibrocartilage
- blends with capsule
- increases congruency 一致性
- prevents hyperextension
why IP joints are more stability than MCP joints
- due to congruent articular surface - median ridge
- strong three ligaments system: proper collateral ligaments, accessory collateral ligaments, volar plate
ROM of IP joints
- flexion
- 0-130 degrees flexion (PIPs)
- 70-90 degrees flexion (DIPs)
- flexion ROM increases toward ulnar side - extension
- volar plate and accessory ligaments are taut - prevent hyperextension
position of safe immobilisation (POSI)
wrist 0-30 degrees E
MCP joint 70-90 degrees F
IP joints 0 degrees E = full extension
extrinsic muscles: flexors
-
powerful ‘motors’ of the fingers & thumb (FDS, FDP, FPL)
**- dependent on: - wrist extensors (length/ tension)
- intrinsic muscles of hand (modify finger F)
- intact flexor gliding mechanism**
flexor gliding mechanism
- retinaculae - anchor long flexor tendons to the hand (將long flexor tendons固定在手上)
- bursae - friction free excursion 遊覽 between tendon and retinaculum
- fibro-osseous tunnels; pulleys
- digital tendon sheaths - reduce friction
what are the functions of digital synovial sheaths
- reduce friction
- nutritional support to tendon
implications: 影響
may heal with adhesions –> therefore, inhibit free gliding of tendon within sheath 可能會因沾黏而癒合 –> 因此，抑制腱鞘內肌腱的自由滑動
extrinsic muscles: extensors
- no digital sheath or pulley system
- extensor expansion: central band, lateral bands: insets into base of sdistal phalanx
- actions: MCP extension
- intrinsics:
lumbricals; IP E > MCP F
interossei; MCP F > IP E
intrinsic and extrinsic interaction 內在和外在的相互作用
allow fine motor function
two types of prehension
抓握力
1. power grip
- cylindrical: handles of tools, racquets (most common)
- spherical: gripping around door knobs
- hook grip: shopping bags, holding cases (thumb not invloved)
- lateral prehension: cigarette (static hold of object between fingers)
2. precision handling
- an object is held between the pads of the thumb and fingers, such as pen, needle and fork
- pad-to-pad, tip-to-tip, pad-to-side
management of skier’s thumb
grade 1 and 2 tears:
- immobilise in thermoplastic splint in slight MCP flexion for 6/52
- physiotherapy: increase ROM and strength
- protective splinting for RTS
grade 3: surgery
- immobilisation for 1/12
