L13 UL Bones and Muscles

Question 1

Features of the human hand

Answer 1

• not weight bearing
• for power and precision grips
• palm to pad interactions
• gripping action - use of tools
• opposable thumb

Question 2

carpal bones

Answer 2

• proximal row (from radial to ulna)
  
  1. scaphoid - contact with radius
  2. lunate - contact with radius
  3. triquetrum - no contact with ulna
  4. pisiform - no contact with ulna but sits on top of triquetrum

cartilaginous disc b/w 3./4. and ulna

• distal row (from radial to ulna)
  
  1. trapezium
  2. trapezoid
  3. capitate
  4. hamate

Question 3

scaphoid bone

Answer 3

“wasting” in the centre - weak point ⇒ FOOSH weakness

• convex part of scaphoid and lunate - connect to radius
• concave part of scaphoid and lunate - join with distal row of carpal bones

Question 4

lunate bone

Answer 4

semilunar shape

• convex part of scaphoid and lunate - connect to radius
• concave part of scaphoid and lunate - join with distal row of carpal bones

Question 5

triquetrum bone

Answer 5

pyramidal shape

Question 6

pisiform bone

Answer 6

sesamoid bone that is embedded in flexor calpi ulnaris

Question 7

trapezium bone

Answer 7

articular facet with first metacarpal - saddle joint

• saddle joint is key for thumb opposition
• has tubercle and grooves (2x flexor retinaculum attachments)

Question 8

trapezoid bone

Answer 8

triangular and “just inzoid” - just inside the trapezium

Question 9

capitate bone

Answer 9

largest carpal bone and centrally placed

• contact with 3rd metacarpal (axis of the hand - 3rd metacarpal)

Question 10

hamate bone

Answer 10

distinctive hook on palmar side - “Hook of Hamate”

• hook of hamate connects to pisiform via pisohamate ligament
  
  • ulnar nerve and artery passes here

Question 11

scaphoid fracture

Answer 11

• most susceptible carpal bone to fracture - commonly fractures at wasting area
• can get necrotic and die
  
  • compromised blood supply to proximal half

Question 12

fracture of hook of hamate

Answer 12

• hook of hamate can be easily palpated
• when hook is compressed ⇒ handlebar neuropathy → press on ulnar nerve
• ulnar nerve innervates only flexor carpi ulnaris and 1/2 of flexor digitorum profundus in forearm
  
  • but innervates a lot in hand → pain detected via muscles of hand

Question 13

metacarpals

Answer 13

• base articulates proximally
• body long stick part
• head articulates distally

above also applies to phalanges

• most robust metacarpal = 1st metacarpal - shortest & fattest

Question 14

phalanges

Answer 14

• base articulates proximally
• body long stick part
• head articulates distally

usually three parts

• proximal phalanx
• middle phalanx
• distal phalanx

thumb only has proximal and distal phalanges

Question 15

fascia in the hand

Answer 15

• deep antebrachial fascia → retinacula
  
  • flexor retinaculum - aka transverse carpal ligament
    
    • forms pyramid shaped palmar aponeurosis - apex is at flexor retinaculum
  • extensor retinaculum

Question 16

fascial compartments

Answer 16

• hypothenar: pinky
• thenar: thumb
• central: middle
• adductor: below thenar - but also technically part of thenar
  
  • is just the adductor pollicis muscle
• interosseous: most dorsal - between bones

Question 17

hypothenar fascial compartment

Answer 17

• medial fibrous septum
  
  • from medial of hand to 5th metacarpal - separates little finger compartment
• little finger compartment

Question 18

thenar fascial compartment

Answer 18

• lateral fibrous septum: from lateral border of palmar aponeurosis to 3rd metacarpal, another fibrous tissue goes beyond this septum and attaches onto the 1st metacarpal
• thumb compartment

Question 19

central fascial compartment

Answer 19

• b/w medial and lateral fibrous septa
• muscles that work on main fingers

Question 20

thenar space

Answer 20

deep to thenar compartment

adductor pollicis muscle is deeper than thenar space

Question 21

palmar aponeurosis

Answer 21

• palmaris brevis: small muscle - attaches to palmar aponeurosis
  
  • when flexed - helps make fist
• palmar aponeurosis - main function = make fist

Question 22

contracture of palmar fascia

Answer 22

thickening and shrinking of the palmar fascia, usually affecting ring and little finger - no known aetiology, but believed to be hereditary

Question 23

Dupuytrens contracture

Answer 23

ring and little finger go into palmar flexion, difficult for movement - needs to be surgically corrected and relieved

Question 24

flexor retinaculum

Answer 24

• forms roof of carpal tunnel - fibro-osseous
• contains median nerve, tendons etc.
• attachments: tubercle of Scaphoid, tubercle of Trapezium, hOok of hamate, Pisiform bone - STOP

Question 25

carpal tunnel

Answer 25

hollow shape w/ tendons, synovail sheaths and median n. * **floor:** carpal bones * **proximal end:** distal wrist crease carpal tunnel syndrome = inflammation

Question 26

structures passing superficial to flexor retinaculum

Answer 26

* **palmaris longus tendon:** inserts onto palmar aponeurosis * **ulnar artery, ulnar nerve:** deep to pisohamate ligament * **superficial branch of radial nerve:** travels past wrist and goes posteriorly * ulnar and radial a. from brachial a. * **cutaneous branch of median nerve** - doesn't go via tunnel * **flexor carpi ulnaris:** placed very medially

Question 27

structures passing deep to flexor retinaculum

Answer 27

* **flexor digitiorum superficialis tendons:** attaches to base of middle metacarpal, bunches up at carpal tunnel * **flexor digitorum profundus tendons** * **median nerve:** recurrent thenar branch - lateral and medial branch * **flexor carpi radialis:** trapezium has groove - 2 places of attachement for flexor retinaculum = FCR place * **flexor pollicis longus** **​​**also synovial sheaths - these can get inflammed

Question 28

extensor retinaculum

Answer 28

* posterior side * don't typically have many problems * attachments: * laterally → radius * medially: triquetrum, pisiform, FCU tendon (extensor retinaculum wraps around this)

Question 29

contents of extensor retinaculum

Answer 29

six tunnels 1. APL, EPB (outcropping) 2. ECRL, ECRB 3. EPL (also outcropping) 4. ED, EI 5. EDM 6. ECU

Question 30

anatomical snuff box

Answer 30

* found by extending the thumb * b/w EPL (medial) and EPB (lateral) * **roof structures:** skin, cutaneous tissue, _cephalic vein, radial nerve_ * **floor structures:** scaphoid and trapezium * **most important structure:** radial artery - scaphoid fracture in snuff box = damaged radial artery

Question 31

intrinsic muscles of the hand (layer 1)

Answer 31

* originates: edges of flexor retinaculum * inserts: base of proximal phalanx

Question 32

intrinsic muscles of the hand (layer 2)

Answer 32

* lumbricals (x4) - because they're "worm-like" * no bony origins * originates: FDP tendons * goes to lateral side of digit * inserts dorsally to external expandion * helps with finger flexion

Question 33

intrinsic muscles of the hand (layer 3)

Answer 33

* opponens pollics: starts from scaphoid and trapezium - inserts at first metacarpal * opponens digiti minimi: from edges of flexor retinaculum - inserts at 5th metacarpal * adductor pollicis: only on thumb - quite large and deep * 2 heads: base of 2nd and 3rd metacarpal + body of 3rd metacarpal * inserts: proximal phalanx of thumb

Question 34

intrinsic muscles of the hand (layer 4)

Answer 34

interossei muscles * lie b/w metacarpals * 3 x palmar - unipennate - **adduction (pAd)** * 4 x dorsal - bipennate - **abduction (dAb)** * from metacarpals (similar to lumbricals)

Question 35

nerve supply of intrinsic hand muscles

Answer 35

* **median nerve:** most of forearm * thenar compartment - recurrent branch of median n. * AbdPB, FPB, OP * lateral branch of median n.: 1st and 2nd lumbrical * **ulnar nerve:** * **​**hypothenar compartment: AbdDM, FDM, ODM, AddP * 3rd and 4th lumbrical * interossei muscles