Hand Outline/Lecture

amount of bones and joints distal to the carpal bones

- 19 bones

- 19 joints

thenar crease corresponding joint

CMC joint of the thumb

proximal palmar crease corresponding joint

index MP joint

distal palmar crease corresponding joints

middle, ring, and little finger MP joints

digital creases corresponding joints

PIP and DIP joints

the hand has several arches which allows the

hand to conform to the shape of the held object

Flexible arches

- metacarpal palmar arch

- longitudinal palmar arch

fixed arches

- carpal arch

bony structure as well as ligament and flexor retinaculum contribute to

the formation of these arches, shape of the flexible ones are also influences by muscular contractions

2nd metacarpal primarily articulates w/

trapezoid

2nd metacarpal secondarily articulates w/

- trapezium

- capitate

- 3rd metacarpal

3rd metacarpal primarily articulates w/

capitate

3rd metacarpal secondarily articulates w/

- 2nd metacarpals

- 4th metacarpals

4th metacarpal primarily articulates w/

hamate

4th metacarpal secondarily articulates w/

- capitate

- 3rd metacarpals

- 5th metacarpals

5th metacarpal primarily articulates w/

hamate

5th metacarpal secondarily articulates w/

4th metacarpal

"Fixed Articulations" - 2nd metacarpal on trapezoid

need stability for pinch

"Fixed Articulations" - 3rd metacarpal on capitate

need stability for central pillar

ECRB, ECRL, and FCR inser on their respective bases of metacarpals so these CMC joints

need to be stable so that forces from these muscles can create wrist motion

mobile articulations - 4th metacarpal on hamate

has about 15 degrees of palmar rotation as well as some flexion and extension

mobile articulations - 5th on hamate

- considered a saddle joint

- has about 30 degrees of palmar rotation as well as some flexion and extension

mobile articulations - mobility necessary

to allow the palm to conform to held objects

Metacarpal phalangeal joints (MCP or MP) arthrokinematics

- conVEX metacarpal head

- conCAVE base of proximal phalanx

MCP metacarpal head is

very large and has a great deal of articular surface for sagittal plane motion

MCP joint classification

condyloid joints

MCP condyloid joints Osteokinematics

- 2 DOF

- flex/ext / abd/add

- some passive rotation is acknowledged that assists the finger in "turning" toward the thumb

MCP ROM: Index and middle finger

0 extension to 90 flexion

MCP ROM: Ring and small finger

0 extension to 100 flexion

MCP ROM hyperextension

some may be present in all 4 (less in 3/4 and more in 2/5

MCP ROM abd/add

20-30 degrees of abd/add when the MP joint is extended, much less when MP joints are flexed

dorsal capsule is

thin and relatively weak, easily penetrated, especially by teeth

Volar Capsule reinforcement

much thicker than dorsal capsule, reinforced by Volar plate

What is the volar plate?

A fibrocartilage structure that is an extension of the base of the proximal phalanx.

What is the function of the volar plate in a joint?

It improves congruency of the joint by increasing contact area.

How does the volar plate protect the joint?

It protects the volar surface of the joint during grip.

What does the volar plate restrict?

It restricts hyperextension.

What does the volar plate prevent in the joint?

It prevents pinching of long finger flexors in the joint.

Volar Plate potential problems

- adhesions- joint contractures

- rupture- hyperextension injuries

Collateral ligament portions

cord and fan portions

Collateral ligaments both parts relatively slack in extensions which allows for

Abduction/Adduction

Loss of ABD/ADD in MP flexion related to

the collateral ligaments as well as boney configuration

tension in cord and fan ligaments

in extension but more tension in flexion

Collateral ligaments - Closed Pack Position is

full flexion

Closed pack position, full flexion improves

stability during grip

Collateral Ligaments: Potential Problems

- adhesions- joint contractures

- Sprains- joint deformity/stability

Immobilization - Position of preference is determined by

collateral ligament characteristics

If pt. has to be immobilized what position is preffered

MP flexion is preferred over extension

MP flexion is clinically referred to as

the position of function

Interphalangeal joints (PIP,DIP) joint classification

hinge joints

PIP, DIP joints DOF

1 DOF

PIP, DIP Arthrokinematics

- Proximal phalanx conVEX

- distal phalanx conCAVE

PIP, DIP capsule is similar to

MP joint (thin dorsal side, volar plates)

ROM: PIP

- 0-100 - 135 of flexion

- increases from lateral to medial side of hand

ROM: DIP

- 0-70 - 90 of flexion

- increases from lateral to medial side of hand

PIP, DIP Collateral ligaments tautness

- portion taut in extension

- portion taut in flexion

PIP, DIP Immobilization: position of preference

determined by the muscle characteristics

PIP, DIP Immobilization: preferred position

extension is preferred over flexion

PIP, DIP Immobilization: position of function for hand

- MP flexion

- PIP and DIP extension

CMC joint classification

saddle joint

CMC joint allows for

- flex/ext

- abd/add

- opposition

What brings the thumb out of the plane of the hand

trapezium is set in about 35 degrees of palmar tilt

CMC joint: Flexion/Extension

- frontal plane movement

- concave metacarpal moving on convex trapezium

CMC joint: Abduction/Adduction

- sagittal plane movement

- convex metacarpal moving on a concave trapezium

CMC joint, APL

inserts on the base of the metacarpal, more of a radial deviator than a thumb abductor

CMC joint, during typical hand activities

high loads pass through this joint, common place for OA to develop

Thumb MP joint

- similar to other MP joints

- no true "average" ROM

Thumb MP joint, volar plate contains

2 sesamoid bones in adults

Thumb MP joint, volar plate job

these further reduce friction and pressure on tendons crossing the joint

Thumb IP joint

similar to other IP joints

position of function for immobilization of the thumb is in

abduction and slight opposition

Palmar Aponeurosis extends

from flexor retinaculum at wrist into palm and the divides into bands which pass up the lateral sides of the digits

Palmar Aponeurosis protects

- structures in the palm

- neurovascular structures of the fingers

Palmar Aponeurosis tethers

skin to palm for grip

Palmar Aponeurosis assists in

maintaining moving parts in their appropriate position

Palmar Aponeurosis: Potential Clinical Problems

- contracture due to scar or burns

- Dupuytren- connective tissue disorder where contractures develop in the palmar aponeurosis

Dorsal Aponeurosis

thin, loose, very flexible

Extrinsic Finger Flexors: Flexor Digitorum Superficialis

- crosses the wrist

- MP and PIP joints to insert on the middle phalanx

- splits at its insertion to allow the other finger flexor tendon to continue to the distal phalanx

Extrinsic Finger Flexors: Flexor Digitorum Profoundus

- crosses the wrist

- MP, PIP, DIP joints to insert on the distal phalanx

During finger flexion which muscle is generally more active

Flexor Digitorum Profoundus

FDS can create flexion at

- wrist

- MP

- PIP

FDP can create flexion at

- wrist

- MP

- PIP

- DIP

Wrist flexion decreases

finger flexion strength to about 1/4 of finger flexion strength w/ wrist in extension

strong grip requires

counterbalancing contractions from ECRB and EDC

For MP flexion to be created by the extrinsic finger flexors

intrinsic hand muscles must be intact

Bursae/Sheaths

reduce friction (contain synovial fluid for lubrication and nutrition)

As FDS and FDP tendons enter the wrist they are

encased in by the ulnar sheath/bursa which generally ends by the DPC

from the DPC to the DIP joint the tendons are

enclosed by the volar digital sheath

in theses sheathes the FDS and FDP

glide differientially

clinically related problems with bursae/sheath

- inflammation and thickening of sheath can restrict tendon glide

- synovial autoimmune diseases like RA can destroy the tendons

Pulleys features

- normal thickenings in the sheath

- annular and cruciate

- hold tendons to the bone and prevent bowstringing

Pulleys clinical problems

- rupture allows for bowstringing of flexor tendons which means during a contraction the muscle shortens more than it should thus a reduction in force due to ?

- adhesions lead to restriction in tendon gliding

- tendon triggering - inflamed tendon gets stuck in the pulley

Tendon glide, also referreed to as

excursion, is the ability of the tendon to move within the stealth

Tendon Glide: FDS and FDP must

be able to glide differientaly

Tendon Glide: FDP can glide

about 7 cm actively (only 1-2cm passively)

Tendon Glide: FDS can glide

about 6 cm actively (only 1-2 cm passively)

adhesions between FDS and FDP tendons reduce

flexor function

a big goal in rehab is to maintain differential gliding can only really do this with

AROM

testing long flexors

- if have active DIP flexion, FDP must be intact (generally tested by holding PIP in extension)

- if can actively flex the PIP with the DIP held in extension the FDS is intact (generally done by holding other fingers in extension)

Extrinsic Finger Flexors

- Extensor Digitorum Communis (EDC or ED)

- Extensor Indicis (EI)

- Extensor Digiti Minimi (EDM)