Chapter 8 - muscle and joint interaction

radial nerve innervates

primarily extensors (needed for grip strength)

radial nerve sensory innervation

dorsal web-space

median nerve innervates

primarily flexors, some thumb

median nerve sensory innervation

pointer finger

ulnar nerve innervates

flexor carpi ulnaris, 1/2 of flexor digitorum profundus, hypothenar area and hand intrinsics

ulnar nerve sensory innervation

pinky finger

extrinisic hand muscles

start outside the hand and go to the hand

intrinsic hand muscles

all parts of muscle are in the hand

flexor pollicis longus OI

middle anterior adius and interosseous membrane to palmar aspect of distal phalanx

flexor pollicis longus action

flex thumb

flexor digitorum superficialis OI

medial epicondyle of humerus and medial side of coronoid process of ulna and radius to sides of middle phalanges 2-4

flexor digitorum superficialis action

flex proximal IP joint

flexor digitorum profundus OI

proximal 3/4 anterior, medial ulna and interosseous membrane to distal phalanges

flexor digitorum profundus action

flex distal IP joints

flexor digitorum profundus is

dual innervated by median n and ulnar n

all finger flexor tends go through

carpal tunnel

ulnar and radial synovial sheaths

surround flexor tendons in carpal tunnel and palms - lubricate and guide tendons, digit 5 is fully sheathed

digital synocial sheaths

surround flexor tendons throughout fingers

what goes through the carpal tunnel

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

carpal tunnel can be irritated with

flexion, extension, typing, gripping, etc..

pulleys are attached to

palmar plates to guide the tendon, then wrapped by a digital sheath

the sheaths allow for

lots of flexion at PIP with little shortening due to short IMA

with a ruptured pulley

bowstringing of tendons occurs to take the path of least resistance, IMA is big and cannot move load nearly as much

role of proximal stabilizers

when you activate finger flexors, you want to flex the wrist too so you must activate extensors to counteract

simply PIP flexion causes

flexion torque forces on wrist and MCP joints too - must offset with extension to isolate PIP flexion

tenodesis

with active wrist extension, you get passive finger flexion

if you injure C6

you are able to flex biceps and wrist extensors, but not finger flexors - put wrist in extension and allow for some passive finger flexion for a more functional position

how to use tenodesis with C6 injury

flex wrist first then activate wrist extensors to cause passive finger flexion and allow for grip, shorter and tighter finger flexor tendons will allow for better grip (claw hand is good)

extensor digiti minimi OI

ulnar side of belly of extensor digitorum to extensor mechanism and dorsal distal phalanx

extensor digiti minimi action

extends pinky

extensor digitorum OI

lateral epicondyle to extensor mechanism and dorsal distal phalanx 2-5

extensor digitorum action

extends digits 2-5

extensor inidicis OI

posterior surface of middle distal ulna and interosseous membrane to ulnar side of tendon to index finger

extensor inidicis action

extends index finger

extensor retinaculum

sheaths and compartments for muscle tendons to prevent bowstringing

extensor indicis has a slight ability to

supinate

extensor tendons go under

extensor retinaculum in sheaths

juncturae tendinae

connective tissue that connects extensor tendons, stabilizes and keeps them in one place (deformity if they slip out_