Hand

what is the palmar surface of the hand also called?

volar surface

what does a ray describe?

decribes on metacaral bone and its associated phalanges

how many bones are in the hand?

The hand consists of 27 bones, including the carpals (8), metacarpals (5), and phalanges (14).

how is the thumb labeled in its anatomical position?

the dorsal surface (where the thumbnail reisdes) faces laterally, the palmar surface faces medially, the radial surface faces anteriorly, and the ulnar surface posteriorly

which arches support the natural concavity of the hand?

three arches- the proximal and distal arches. and the longitudinal arch

what forms the proximal transverse arch of the hand?

the distal row of carpal bones, is static and rigid and forms the carpal tunnel, the keystone is the capitate

what forms the distal transverse arch?

the distal ends of the MCP joints, the distal arch is mobile compared to the proximal end, keystone is the MCP joints of the central metacarpals (2-3)

what forms the longitudinal arch?

follows the general shape of the second and third rays, the keystone is the 2nd and 3rd MCP joints

what is the function of the CMC joints?

to allow the concavity of the palm to fit around many objects

which digits form the most stable and fixed central pillar in the hand?

the second and third digits

which is the most mobile CMC joint?

the thumb CMC joint, followed by the fifth, then the fourth, allowing them to “fold” around the hand’s central pillar

what kind of joints are the CMC joints of the second and third digits?

planar to complex saddle joints with interlocking surfaces that create the central pillar of the hand

what motions create the “cupping” motion of the CMC joints of the 4th and 5th digit?

flexion and “internal” rotation of the ulnar metacarpals toward the middle digit to deepen the palmar concavity

how many degrees of flexion and extension do the 4th and 5th CMC joint have when the other is constrained?

approx 20 degrees

how many degrees of flexion/extension does the fifth digit have when the fourth is unconstrained?

about 44

what does the mobility of the fourth and fifth CMC joint provide while clenching a fist?

improves the effectiveness of a grasp, enhances interaction with thumb

which is the most complex CMC joint?

the thumb- its saddle shape allows thumb opposition which allows the encircling of objects help within the thumb, as well as greatly enhances the dexterity of human precision

what is the shape of the longitudinal diameter of the proximal articular surface of the thumb metacarpal?

convex (allowing rolling and sliding in opposite directions during abduction and adduction)

what is the shape of the tranverse diameter of the the proximal articular surface of the thumb metacarpal?

concave (allowing rolling and sliding in the same direction during flexion and extension)

what plane does abduction/adduction of the CMC joint of the thumb occur in?

sagittal plane around a medial lateral axis

what plane does flexion and extension of the CMC joint of the thumb occur in?

frontal plane around an anteroposterior axis

what are the phases of opposition of the thumb?

first phase is abduction, next is the flexion and medial rotation, and reposition involves adduction adn extension-lateral rotation

is the capsule of the CMC joint of the thumb loose or tight?

loose to accommodate a large and circular ROM

what is the function of the ligaments of the CMC joint of the thumb?

help control extent and direction of joint motion, maintain alignment and stability, and dissipate forces produced by activated muscles

what motions do the anterior (palmar) oblique ligament resist (and which are they slack in?)

a thin and weak ligament, is slack and opposition, flexion, and abduction, taut in full extension

ulnar collateral ligament (of thumb)

part of the transverse carpal ligament, is taut in abduction and extension

which motions are the intermetacarpal ligament of the thumb taut in?

taut in opposition, flexion, and extension

radial collateral and posterior oblique

relatively thick and strong, densley populated with sensory fibers, taut in opposition, flexion, and abduction

what are the ligaments within the capsule of each MCP joint that provide stability?

radial and ulnar collateral ligaments, palmar (volar) plate which is a dense and thick fibrocartilage

what is the primary function of the palmar plates?

to strengthen the strucutre of the MCP joints and limit the extremes of extension

how many degrees of freedom are there in the MCP joints?

2- flexion/extension and abduction/adduction

accessory motions of the MCP joints

are motions that occur passively (passive mobility), include distraction-compression, translation, and axial rotation which allows the fingers to better conform to shapes of held objects and increase control of grasp

how many degrees of freedom are there in the MCP of the thumb?

just one- allows flexion/extension in the frontal plane around an anterior-lateral axis of rotation, abduction/adduction is super limited and considered accessory motion

how many degrees of freedom do the PIP and DIPs have?

1- allows flexion/extnesion

what is the approximate ROM of the PIP?

flexion of 100-120, minimal extension with flexion greater in ulnar digits

what is the approx ROM of the DIPS

flexion of 70-90, extension 0-30

what is the appoximate ROM of the IP of the thumb?

active flexion: 70, passive extension: beyond neutral to 20 degrees

how can contractures be limited if immobilization is necessary>?

position the wrist and hand into a position of function- 20-30 degrees of extension with slight ulnar deviation, 35-45 of MCP flexion, 15-30 of PIP and DIP flexion, and 35-45 of thumb abduction

what position does the position of function create?

a slightly opened and cupped hand, with the wirst in the position to maintain optial length of the finger flexor muscles

what are the extrinsic flexor muscles of the digits?

flexor digitorum superficialis, flexor pollicis longus, and flexor digitorum profundus

what do the distal attachments of the extrinsic finger flexor muscles travel through on their way to their distal attachment?

fibrous digital sheaths aka the protective fibro-osseus tunnels

what are the structures found within the digital sheaths that prevent bowstringing of the tendons called?

flexor pulleys

how are the major pulleys classified compared to the minor pulleys

major (A2 and A4) attach to the shafts of the proximal and distal phalanx, and minor (A1, A3, A5) attach to the palmar plate at each of the three joints within a finger

which ligaments of the thumb act as pulleys for the passage of the tendon of the flexor pollicis longus?

annular and oblique ligaments

how can extrinsic digital flexors isolate flexion at one joint despite crossing muscle joints?

other muscles contract synergistically with the digital flexors to prevent flexion across all the joitns

what is tenodesis action?

refers to the passive flexion of the fingers and thumb that occurs as the wrist is extended, occurs due to stretch on the extrinsic digital flexors

what are the extrinsic extensors of the fingers?

extensor digitorum, extensor indicis, extensor digiti minimi

what is the function of the extensor mechanism (extensor expansion) of the fingers?

transfers extensor force distally throughout the entire finger

how does the extensor mechanism form?

the extensor digitorum’s tendon splits into three parts, creating a hood-like structure over the proximal phalanx (the central band), which attaches to the dorsal base of teh middle phalanx and diverges into two lateral bands that run to the distal phalanx.

what occurs when the central band of the extensor mechanism ruptures?

boutonniere deformity as the PIP is no longer held into extension and falls into flexion, with the lateral band intact and pulling the DIP into hyperextension

what occurs when the lateral band of the extensor mechanism ruptures?

swan neck deformity as the DIP falls into flexion as the lateral band is slackened, and the central band intact continues to pull the PIP into hyperextension

based on the figure, which muscle is capable of adduction?

extensor pollicis longus

based on the figure, which muscle has the greatest moment arm for flexion of the MCP joint of the index finger?

lumbrical

what is the extrinsic plus position?

with the MCP extended and the PIP and DIP flexed- all the extrinsic muscles are activated (ED, FDS, FDP)

what is teh intrinsic plus position?

with the MCP flexed and the DIP and PIP extended- all instrinsics are activated (lumbricals adn interossei)

how does finger extension progress (phases)?

early phase: extensor digitorum extend MCP joint, middle phase: intrinsic muscles assist ED with extension of PIP and DIP joints. late phase: muscle activation continues through full finger extension

how does finger flexion progress (phases)?

early phase: flexor muscles activley flex the joints of finger, late phase: muscle activation continues (ED helps to decelerate flexion of the MCP joint)

which muscles are activated when flexing the fingers against resistance or at relatively high speed?

FDP , FDS, and interosseus muscles to some extent

types of grip

includes teh power grip, the precision grip, teh power (key) pinch, the precision pinch, and the hook grip

what are the primary extensors of the fingers?

the extensor digitorum and intrinsic muscles (lumbricals and interossei)

what is the arthrokinematics of the CMC joints?

the irregular surfaces of the CMC joints prohibit standard roll adn slide arthrokinematic descriptions

what do the MTP joints serve as in terms of the mobile arches of the hand?

serve as keystones