Hand and Wrist anatomy II Flashcards
Carpal tunnel
flexor retinaculum comprises the roof
palmar radiocarpal ligament on the floor
carpal bones comprise the lateral and medial borders
Carpometacarpal (CMC) joints
composed of articulation between the distal row and the bases of the 2-5 metacarpals
the distal row also has a volar concavity or carpal arch which is maintained by the transverse carpal ligament
allow only gliding motion to occur
progress in mobility from 2nd to 5th MCP
movement contributes to mobility of distal transverse arch
stability is provided by palmar and dorsal ligaments
Metacarpophalangeal joints of the 2-5 fingers (MCP)
convex metacarpal head and concave base first phalanx
conyloid with 2 deg freedom: flx/ext and abd/add
surrounded by a capsule tha is lax in EXT
incongruous jt needs accessory structure to enhance stability-volar plate
Collateral ligaments at MCP joint
collateral lig: dorsolateral metacarpal to palmar-lateral proximal phalanx
loose in EXT
Tight in flexion
MCP joints of the fingers: Volar Plate
thick and fibrocartilaginous
is loosely attached to metacarpal and firmly attached to proximal phalanx and slides proximally during flexion
its fibrocartilaginous structure adds surface area to the base of the prox phalanx, to more closely approx the larger metacarpal head
MCP and IP joints
the volar plate arrangement, along with collateral ig promote stability and allow circumduction and increased extension at MCP
together with transverse metacarpal arch, the passive movements at the MCP joints enhance the plasticity of the hand
capsular, volar, and collateral lig arrangement are very similar at MCP and IP joints
Interphalangeal joints of the fingers
true for fx/ext hinge joints with 1 deg of freedom
heads of middle and distal phalanx are convex and bases are concave
colateral lig is a true collateral (pass directly through axis or rotation as they cross the joints) and maintain their tension during both flx and ext contributing to increased flexibility
PIP
capsule surrounding the joint is composed of a volar plate, lateral and accessory collateral ligaments and extensor expansion
volar plate a) functions as a static restraint to hyperext, b) increases surface area of joint
DIP
similar to PIP except less stability and allows some hyperext
CMC joint of the thumb
CMC is an articulation between trapezium and base of first metacarpal
saddle joint with 2 deg of motion-flx/ext and abd/add; also permits circumduction or opposition
capsule is lax but reinforced with radial, unar, volar, and dorsal ligaments
loose capsular structure permits 55 deg ext, 50 deg abd, 17 deg axial rotation
the extensive range and repetitive motion subject the joint to degenerative changes
MCP of the thumb
semicondyloid articulation between the head of the first metacarpal and the base of the proximal phalanx
allows flx/ ext and abd/add
two sesamoid bones are extracapsular to the volar surface
mainfunction is to provide additional ROM to thumb pad in opposition, and to allow contour of thumb to objects
joint capsue and volar plate are imilar to other MCP joints
IP joint of the thumb
articulation between the head of the proximal phalanx and base of distal phalanx
structurally and functionally it is the same of IPs of the fingers
muscles of the wrist and forearm
extrinsic muscles join with intrinsic muscles to act on the hand without excessive bulkiness
the extrinsic tendons enhance wrist stability by balance flexor and extensor forces and compressing carpals
Extensor tendons differ from flexor tendons
innervation comes from 3 peripheral nerves:
ED-radial
Interossei- ulnar
Lumbricals- ulnar and median
extensors flatter, more superficial,a nd more vulnerable (easier to repair)
flexor tendons can become stuck under pulleys; but extensor tendons often heal with a lag
extensor mechanism
made up of ED tendon, it’s connect tissue expansion, and the central tendon bands
extensor hood has bands that connect to the volar plate
more complex then FLX
