Hand: Bones and muscles Flashcards
What are some evolutionary adaptations of the human hand?
- Power grip: Use palm and fingers to manipulate objects
- Precision grip: Put thumb and finger in opposition
- Thumb is rotated in relation to fingers
- Prehensile fingers but not toes
- Thumb is relatively long in humans in comparison to other primates
- Can carry out many fine muscular movements
What are the carpal bones?
These are the most proximal bones of the hand. There are 8 bones arranged into two rows, bridged by the flexor retinaculum.
Bones (Prox-dist/Lat-med):
- Scaphoid (Some)
- Lunate (Lovers)
- Triquetrum (Try)
- Pisiform (Positions)
- Trapezoid ( They)
- Capitate (Can’t)
- Hamate (Handle)
What fractures are the carpal bones subject to?
The scaphoid is most vulnerable to dislocation/fracture - blood supply to proximal half of the carpals is compromised.
The hook of hamate is also susceptible to fracture - ulnar canal syndrome or handlebar neuropathy
Describe the metacarpal bones.
Each is made up of a base, body and a head.
Numbered from I-V (thumb to pinky).
Articulate with carpal bones
Fracture usually occurs at I or V metacarpal
Describe the phalanges.
Each finger is made up of a proximal, middle and distal phalanx, except thumb, which is made of a proximal and distal phalanx.
Each is made of a base, body and head
What are the fascial compartments of the hand?
- Hypothenar fascia
- Thenar fascia
- Central fascia
- Adductor fascia
- Interosseous fascia
At the wrist is the flexor retinaculum
There is a fibrous septum between each compartment
If there is infection/sepsis, it is compartmentalised to one fascial compartment
Palmar aponeurosis
A tightening of the fascia of the palmar surface, which allows the palm to be divided into compartments. Mostly found in the central part of the palmar surface.
Most superficial: Palmaris brevis and palmar aponeurosis.
Contracture of palmar fascia - thickening and shrinking of palmar fascia, typically affecting ring and little finger - hand of benediction
What is the flexor retinaculum?
Also known as the transverse carpal ligament
Connects the two bones on the medial side to the two bones on the lateral side.
Forms fibro-osseus roof of the carpal tunnel
What is the carpal tunnel?
Roof: Flexor retinaculum
Floor: Carpal bones
Proximal end identified by distal wrist crease
Contains flexor tendons, synovial sheaths and median nerve
Tendons run smoothly through the region, facilitated by synovial fluid form the synovial sheaths.
What structures pass superficial to the flexor retinaculum?
- PL tenon
- Ulnar artery and nerve
- Superficial branch of radial artery
- Palmar cutaneous branch of median nerve
- FCU tendon lies medial to FR
What structures pass deep to the flexor retinaculum?
- FDS (x4 tendons)
- FDP (x4 tendons)
- FPL
- Median nerve - recurrent thenar branch and lateral and medial branch
- FCR (within roof of carpal tunnel)
- Synovial sheaths
What is the extensor retinaculum?
Attachments:
- Radius laterally
- Triquetrum, pisiform, FCU tendon medially
Contents:
- Six tunnels
- Nine tendons: 11 in total, 2 don’t go all the way through - Brachiradialis and supinator
- Synovial sheaths
Tendons:
- APL + EPB
- ECRL +ECRB
- EPL
- ED + EI
- EDM
- ECU
Describe the anatomical snuffbox.
Boundaries:
- Anteriorly: Tendons of APL and EPB
- Posteriorly: Tendon of EPL
Roof: Skin, subcutaneous tissue, cephalic vein, superficial branch of radial nerve
Floor: Scaphoid and trapezium
Contains the radial artery.
Which intrinsic muscle of the hand are present in layer 1?
Thenar muscles:
- Abductor pollicis brevis (AbdPB)
- Flexor pollicis brevis (FPB)
Hypothenar muscles:
- Abductor digiti minimi (AbdDM)
- Flexor digiti minimi (FDM)
Arise from edges of flexor retinaculum
Insert into base of proximal phalanx
Which intrinsic muscles of the hand are present in layer 2?
Lumbricals (x4)
Arise from FDP tendons
Pass to lateral sid eof digit
Insert dorsally into extensor expansion of digits 1-4
Flex at IP joints but not MCP joints (remains straight)
