3.2 Hand: Bones and muscles Flashcards
Scaphoid fracture
Waist of bone is narrow and is the weakest part, susceptible to fracture, and scaphoid is the most freq fractured of carpal bones.
Blood supply to the proximal half of bone is compromised.
Carpal bones
Proximal to distal, medial to lateral:
Scaphoid, lunate, triquetrum, pisiform*
Trapezium, trapezoid, capitate, hamate
*sesamoid bone - works as a ball-bearing so that bone doesn’t rub against bone
Fracture of hook of hamate
Deep to the hook of hamate is the ulnar nerve, which is susceptible when HoH is fractured.
If there is damage to a nerve, the muscles it innervates distal to that point are compromised.
Fascial compartments of the hand
- hypothenar
- thenar
- central
- adductor
- interosseous
Contracture of palmar fascia
Aka Dupuytrens.
Thickening & shrinking of palmar fascia, typically affecting ring and little fingers. No known aetiology but thought to be inherited condition.
Flexor retinaculum
Aka transverse carpal ligaments
Attachments to 4 bones
- medial side: pisiform and hamate
- lateral side: tubercles of scaphoid and trapezium
What lines the roof and floor of the carpal tunnel and what lies within it?
Roof: flexor retinaculum
Floor: carpal bones
Proximal end identified by distal wrist crease
Contents: flexor tendons, synovial sheaths (synovial fluid allows smooth action/lubrication for tendons to flex/extend the hand) and median nerve
What structures pass superficial to the flexor retinaculum?
PL tendon
Ulnar artery and nerve
Superficial branch of the radial artery
Palmar cutaneous branch of median nerve
*FCU tendon lies well medial
What structures pass deep to flexor retinaculum?
4 tendons of FDS 4 tendons of FDP FPL Median nerve: recurrent thenar branch, lateral & medial branches FCR (within roof of carpal tunnel) Synovial sheaths
What are the attachments and contents of the extensor retinaculum?
Attachments:
- radius laterally
- triquetrum, pisiform, FCU tendon medially
Contents:
- six tunnels
- nine tendons
- synovial sheaths
**11 extensor muscles and 9 go through the wrist
(supinator and brachioradialis do not go through wrist)
What are the boundaries and contents of the anatomical snuffbox?
Boundaries:
- anteriorly tendons of APL and EPB
- posteriorly tendon of EPL
Roof:
-skin, subcutaneous tissue, cephalic vein (comes off dorsal venous arch), superficial branch of radial nerve
Floor:
- scaphoid
- trapezium
Contents:
-radial artery
What are the intrinsic muscles of the hand in the layer 1?
Arise from edges of flexor retinaculum and insert into base of proximal phalanges
Thenar muscles:
- abductor pollicis brevis (AbdPB)
- flexor pollicis brevis (FPB)
Hypothenar muscles:
- abductor digit minimi (AbdDM)
- flexor digiti minimi (FDM)
What are the intrinsic muscles of the hand in layer 2?
Lumbricals x4:
- arise from FDP tendons
- pass to lateral side of digit
- insert dorsally into ext expansion (digits 1-4)
**Note action on MCP vs IP joints due to E expansion
What are the intrinsic muscles of the hand in layer 3?
Thenar muscles:
- opponens pollicis (OP)
- adductor pollicis (AddP) = fan shaped muscle in 1st web space
Hypothenar muscles:
-opponens digiti minimi (ODM) = arise from edges of flexor retinaculum and insert along borders of MC (5)
What are the intrinsic muscles of the hand in layer 4?
Interossei: 3 palmar (adduct; pAd) 4 dorsal (abduct; dAb)
- arise from MC’s
- pass to lateral side of digit
- insert into extensor retinaculum (digits 1-4)
