The Digits

Question 1

Classify the Carpometacarpal Joint

Answer 1

synovial, plane joints
2nd & 4th - compound
3rd & 5th - simple

Question 2

Describe the articular surfaces of the carpometacarpal joints

Answer 2

Articular surfaces are flat.
2nd metacarpal articulates with:
- trapezium
- trapezoid
- capitate

3rd metacarpal articulates with:
- capitate

4th & 5th metacarpals articulate with:
- hamate and capitate

Question 3

Describe the joint capsule of the carpometacarpal joint

Answer 3

Fibrous capsule - thickened by palmar and dorsal carpometacarpal ligaments

Extends between the distal carpal bones and bases of 4 medial metacarpals

extends between the metacarpal bases

Question 4

Describe the synovial membrane of the carpometacarpal joint

Answer 4

lines all non-articular surfaces of the joint

Question 5

What ligaments support the carpometacarpal joint?

Answer 5

palmar and dorsal carpometacarpal ligaments - thickenings of the JC (pass proximally to distally)

interossesous ligaments - passing between adjacent carpal bones (transversely)

Question 6

What movements can occur at the carpometacarpal joint?

Answer 6

small amounts of gliding - freer at 5th MC.

2nd & 3rd CMC joints almost immobile.

Question 7

Classify the intermetacarpal joint

Answer 7

Simple, biaxial, synovial plane joint

Question 8

Describe the joint capsule of the intermetacarpal joint?

Answer 8

Formed by extensions of the palmar and dorsal carpometacarpal ligaments and the interosseous ligaments.

Joint space is continuous with CMC joint

Question 9

What movements occur at the intermetacarpal joint?

Answer 9

gliding between adjacent metacarpals - accompanies movements at CMC joint

Question 10

Classify the metacarpophalengeal joint

Answer 10

synovial, biaxial, simple condyloid joint

Question 11

describe the articular surfaces of the metacarpophalengeal joint

Answer 11

Biconvex metacarpal head - broader anteriorly than posteriorly
- coated in hyaline cartilage which extends further proximally on anterior surface

biconcave base of proximal phalanx has smaller articular surface

• relatively incongruent
• SA increased by palmar ligament on anterior surface

Question 12

Describe the joint capsule of the metacarpophalengeal joint

Answer 12

loose capsule attached to the joint margins

• strengthened by collateral ligaments
• replaced anteriorly by palmar ligament
• replaced posteriorly by dorsal digital expansion

Question 13

Describe the synovial membrane of the metacarpophalengeal joint

Answer 13

lies the capsule and covers all non-articular surfaces

- lines anterior and posterior recesses to increase ROM in flexion

Question 14

What are the attachments of the collateral ligaments of the metacarpophalengeal joint?

Answer 14

O: tubercle and depression on side of metacarpal head

I: palmar aspect of the base of the proximal phalanx

Question 15

What is the shape and DOF of the collateral ligaments of the metacarpophalengeal joint?

Answer 15

strong and fan shaped - run inferiorly

anteriorly - blend with palmar ligament
posteriorly - blend with dorsal digital expansion

Question 16

What is the function of the collateral ligaments of the metacarpophalengeal joint?

Answer 16

limit abduction and adduction

taut in flexion

Question 17

What are the attachments of the palmar ligament?

Answer 17

O: firmly attached to anterior base of proximal phalanx

I: loosely attached to neck of metacarpal via JC

Question 18

What is the shape and DOF of the palmar ligament?

Answer 18

dense fibrocartilagenous plate

Runs superiorly

Question 19

what is the function of the palmar ligament?

Answer 19

Limits extension

Provides a mobile joint surface to increase flexion

Question 20

What are the attachments of the deep transverse metacarpal ligaments?

Answer 20

short ligaments connecting the palmar ligament on the four MCP joints together

continuous with the palmar fascia

Question 21

What is the function of the deep transverse metacarpal ligament?

Answer 21

Bind the heads of the metacarpals together - limit abduction

Question 22

Classify the interphalangeal joints (PIP/DIP)

Answer 22

synovial, simple, uniaxial, hinge joint

Question 23

Describe the articular surfaces of the interphalangeal joints

Answer 23

pulley shaped head on proximal phalanx
- larger anteriorly

articulates with two shallow facets separated by a ridge on base of distal phalanx

lined in articular cartilage
palmar ligament acts as mobile joint surface

Question 24

Describe the joint capsule of the interphalengeal joint

Answer 24

loose fibrous capsule

• strengthened by collateral ligaments medially and laterally
• replaced anteriorly by palmar ligament
• replaced posteriorly by dorsal digital expansion

Synovial membrane lines all non-articular surfaces and anterior/posterior recesses

Question 25

What is the nerve supply to the carpometacarpal joint?

Answer 25

Ulnar nerve C7, C8

Question 26

What is the nerve supply to the intermetacarpal joint?

Answer 26

ulnar nerve C7, C8

Question 27

What is the nerve supply to the metacarpophalengeal joint?

Answer 27

twigs of Median nerve - C7

Question 28

what is the nerve supply to the interphalengeal joints?

Answer 28

twigs of median nerve - C7

Question 29

What is the dorsal digital expansion?

Answer 29

An expansion of the tendons from extensor digitorum - forming an aponeurosis

Question 30

what is the structure of the dorsal digital expansion?

Answer 30

Base lies proximally over base of metacarpal

At the phalanx, divides into three parts:

• central slip - inserts to posterior aspect base of middle phalanx
• two lateral slips - wrap around the sides of the middle phalanx (as a ‘hood’) –> reunite and insert onto posterior aspect of base of distal phalanx

Question 31

what is the role of the dorsal digital expansion?

Answer 31

Allows coordinated flexion and extension of the IP joints

Supports the IP joint capsules