Hand anatomy

Question 1

Drawing and name a transverse section through the finger?

Answer 1

See diagram but name

• terminal slip
• Lateral band
• Central band
• Sagital Band
• Lumbricals
• Flexor digitorium profundus
• Flexor digitorium superificialis

Question 2

What causes MCP Flexion?

Answer 2

• 70% Interosseous
  
  • 3 Palmar inerosseous- adductors
  • 4 Dorsal Interosseous-abduct
  • origin mc shaft to base of prox phalanx+ extensor expansion
  • supply deep branch of ulnar nerve
• 30% Lumbricals- attach to FDP distal and extensor proximally
  
  • lumbricals 1/2 =2/3 rd digit= median nerve- unipennate, from radial side FDP2/FDP 3
  • lumbricals 3/4= 4/5 digit= ulna nerve- bipennate, from radial side fdp3/4 (lumbrical3 ) and fdp 4/5 (lumbrical 4)

Question 3

What causes PIPJ and DIPJ extension?

Answer 3

PIPJ

• Lumbricals ( via lateral band)
• EDC Central slip
• Dorsal interossei

DIPJ

• EDC terminal tendon
• Lumbricals via lateral bands

Question 4

What causes extension at MCPJ?

Answer 4

Extensor digitorium communis (sagittal band)

• Origin- lat epicondyle of humerus
• Inserts- extensor expansions 4 digits- index-ring
• also extends hand at wrist joint + MCPJ extension
• innervation: PIN ( radial N)
• blood s= Interosseous arteries

Question 5

What flexes the PIPJ and DIPJ?

Describe their origin/insertion/Nerve and blood supplyDI?

Answer 5

PIPJ

Flexor digitorium superificalis (FDS)

Flexor digitorium profundus (FDP)

DIPJ

Flexor digitorium profundus (FDP)

FDP

origin- ant 3/4 proximal ulna, interosseous membrane,deep fascia of forearm. Thru carpal tunnel with FDS

Inserts: thru fds inserts distal phalanx

innervation: 4/5 th digitis ulna, 2/3rd AIN ( medial)

FDS
origin- medial epicondyle humerus(common flexor origin)

inserts:ant margins of base of middle phalanges 2-4 fingers

Innervation : Median Nerve

Question 6

What does the retinacular ligament do ?

Answer 6

• Retain and position the extensor mechanism during DIPj adn PIPJ flexion
• Similar to sagittal band function

Question 7

Describe the components of retinacular ligament and their function?

Answer 7

• Oblique Band- links motion of DIPJ and PIPJ from lateral volar proximal phalanx->dorsal terminal phalanx. when PIPJ flexes-> DIPJ flexes vis versa
  
  • Contracture-> volar displacment of lateral band-> Bountonniere
• Transverse Band- with pipj flexion pulls lateral bands volarly over pip
  
  • attenuation lead to dorsal translation of lateral bands-> swan neck deformity

Question 8

Name the digital cutaneous ligaments?

Answer 8

• Cleland’s- ‘Ceiling’
  
  • Dorsal to digital nerves, NOT involved in Dupytren’s
• Grayson’s- ‘Ground’-
  
  • Volar to digital nerves, involved in Dupytrens

Question 9

What is the funciton of digitial cutaneous ligaments?

Answer 9

• Tether skin to deeper layers of fascia and bone to prevent excess movement of skin and improve grip
• It also stabilses the NV bundle during flexion and extension

Question 10

What is the function of the extension hood?

Answer 10

Allow extension of the PIPJ and DIPJ

Question 11

What are the components of the extension hood?

Answer 11

• Central slip- extends PIPJ- inserts base of middle phalanx
• Lateral band- extends DIPJ-inserts distal phalanx formed from deep head of dorsal interossei and volar interossei combining

Question 12

What inserts into the lateral band?

Answer 12

• Interossei- dorsal /palmar
• lumbricals
• Extensor incidis

Question 13

What is the function of MCPJ collaterals?

Answer 13

• Stabilise MCPJ during motion
• Collaterals tight in flexion, loose in extension- as MCP flexes PIPJ further away so tightening ligaments

Question 14

Describe the MCPJ collaterals?

Answer 14

• Radial Collateral ligaments more horizontal than Ulnar Collateral ligaments
• Each collateral has an accessory and proper ligaments
• Accessory - more volar, tight in extension- add/abduction stress in extension
• Proper- more dorsal, tight in 30^o of flexion- add/abduction stress in 30^o flexion

Question 15

What is the function of deep transverse metacarpal ligaments?

Where does it insert?

Answer 15

• Prevents MC heads from splaying apart
• Connects 2-5th MC heads together at volar plate

Question 16

What is the role of the Natatory ligament?

Answer 16

• Resists abduction
• Most superifical MC ligaments
• origin- MC/MCPJ
• inserts- prox phalanx of all 5 fingers
• Involved in Dupytrens

Question 17

What is the function of the sagittal bands?

What is its orgin/ insertions?

Answer 17

• Keep extensor mechanism tracking in midline during flexion of MCPJ
• Origin- Palmar plate
• inserts- dorsal extensor mechanism

Question 18

What is the traingular ligament’s function?

Answer 18

• counteracts pull of oblique ligament-preventing lateral subluxation of common extensor mechanism
• located on dorsal side of extensor mechanism, distal to PIPJ
• Triangular in shape

Question 19

what is the functon of the volar plate?

Answer 19

• Prevent hyperextension
• thickening of joint caspule at MC head and inserts into proximal phlanax via checkrein ligaments
• tight in extension, loose in flexion