MECHANICS & PATHOMECHANICS OF HAND

By : Amrita TomarGuided By: Dr.Manisha Rathi

Hand consist of :

•4 fingers

•1 thumb

Creases of hand:

Joints of hand :

Total 19 bones&19 articulationsby29 muscles

sL

TP

HCpTm Tz

CMC JOINT OF FINGERS

2nd to 4th CMC joints

•Plain synovial joint•Articular surfaces: 1) distal carpal row 2) proximal surface

of base of 2nd to 4th metacarpal row

•Ligaments

1) deep transverse metacarpal ligament - It tethers the metacarpal heads together and provides CMC joint stability.

2) volar & dorsal longitudinal ligaments

5th CMC joint•saddle joint

•2 degrees of freedom -flexion -extension -abduction -adduction

•CMC Joints of 2nd 3rd 4th digits–plane

uniaxial joints.

•CMC Joint of 5th digit-biaxial joint.

•Flex of CMC and additional adduction of

the 5th MC improves the ability of the

hand to grasp the objects of various sizes.

where as extn of MC helps to release

those objects.

Palmar arches : 1) Proximal transverse

arch2) Distal transverse arch3) Longitudinal arch

• Proximal transverse

arch is formed by

trapezium, trapezoid,

capitate and hamate.

• Curve shape of the arch

is still maintained when

the hand is open by the

lig.; i.e. transverse

carpal lig. and

intercarpal lig.

• Distal transverse arch is present transversely across

the arch.

The adjustable position of 1st 4th and 5th MC heads

around the relatively fixed 2nd and 43rd MC forms a

mobile distal transverse arch at the level of MC heads

that augments the fixed proximal transverse arch of

the distal carpal rows.

• Longitudinal arch extends the length of digits from

proximal to distal.

Functions of palmar arches :-

• It allow the palm and the digits to

confirm optimally to the shape of the

object being held.

•It maximizes amount of surface contact,

enhancing stability as well as sensory

feedback

MCP JOINT OF FINGERS• Articular surfaces:

Proximally-

convex metacarpal head

Distally-

concave base of

the 1st phalanx

• Joint is incongruent due to inappropriate articular surface

• Type of joint: synovial joint of condylar variety

• 2 degrees of freedom-

flex/ext

abd/add

• Flexion and extension increases from radially to

ulnarly

• ROM: 1) index flexion- 90 degree

2) little finger flexion- 110 degree

• Ligaments :

1) Radial Collateral ligament

2) Ulnar Collateral ligament

• Each composed of two parts –

collateral ligament proper &

accessory collateral ligament

•They provide stability through out the

MCP jt ROM with part of fibres taut at

various points in the range

• Volar plate : It is an accessory joint

structure to enhance the joint stability

by increasing the joint congruency.

INTERPHALANGEAL JOINTS OF FINGERS•True synovial hinge joint

•Articular surfaces: Proximally- pulley shaped head of

phalanx (large) Distally- base of phalanx having 2 shallow

concave facets with a central ridge.(small)

• Ligaments- radial collateral ligament

- ulnar collateral ligament

• Lig. Remains taut and Provide stability and support to PIP and DIP Joint throughout.

• Volar plates- reinforce each joint capsule and enhance stability and limit hyperextention.

• ROM- 1 degree freedom (flexion- extention)

ROM for PIP and DIP flexion increases from radially to ulnarly.

• index PIP joint flexion - 100 degree

index DIP joint flexion - 80 degree

• 5th PIP joint flexion – 135 degree

5th DIP joint flexion – 90 degree

Muscles:

extrinsic- the finger muscles having proximal attachment above the wrist (radiocarpal jt)

intrinsic- the finger muscles having attachment distal to the wrist (radiocarpal jt).

MCP & IP joints of thumb are structurally and functionally

identical to the MCP & IP joint of the finger

MCP joint of thumb differs in that it is reinforced by the 2

sesamoid bones which improve the leverage of

flexor pollucis brevis

CMC JOINT-THUMB

• Articulation between trapezium and the base of 1st metacarpal

• Articular surfaces - Trapezium - saddle shaped portion

spherical portion

Saddle shaped portion is concave in sagittal plane and convex in frontal plane

Spherical portion-convex in all direction Base of 1st metacarpal has a reciprocal

shape to that of trapezium

Flexion /extension and abduction/adduction are proposed to occur on saddle shape surfaces whereas axial rotation of the metacarpal that accompanies opposition is proposed to occur in the spherical surface

•TYPE OF JOINT -biaxial , saddle •Two degrees of freedom Flexion/ extension-around AP axis- 53 d Abd /add-around coronal axis- 42 d Rotation 17 d

•Flexion /extension and

abduction/adduction are proposed to

occur on saddle shape surfaces whereas

axial rotation of the metacarpal that

accompanies opposition is proposed to

occur in the spherical surface

•Type of joint:

-biaxial , saddle

•Two degrees of freedom:

Flexion/ extension-around AP axis- 53 d

Abd /add-around coronal axis- 42 d

Rotation 17 d

•Capsule: Relatively lax, but it is

reinforced by following ligaments.

• These ligaments are important stabilizers of the CMC

joint. As a group they resist the tendency of CMC to

dislocate

• The large functional demands placed on the CMC joint

of thumb results in a painful condition called BASILAR

JOINT ARTHRITIS

• When the ligaments are weakened by arthritis, the

joint often dislocates laterally relative to the

trapezium.

Functions of the CMC joint

•It has a unique range & direction of

motion that produces opposition (abd+

flex+add+ simultaneous rot.) of thumb

•This opposition occurs in all forms of

prehensions

EXTRINSIC MUSCLES

FLEXORS OF THE DIGITS..

FLEXOR DIGITORUM SUPERFICIALIS..• O

▫ Medial epicondyle of humerus

▫ Coronoid process▫ Middle ½ anterior radius

• I▫ Four tendons separating

into two parts that insert into sides of bases of middle 2-5 phalanx

• N▫ Median

• A▫ MCP flexion digits 2-5▫ PIP flexion digits 2-5

FLEXOR DIGITORUM PROFUNDUS..• O

▫ Antero-medial surface of ulna

▫ Interosseus membrane• I

▫ Four tendons inserting into distal phalanxes of digits

2-5• N

▫ Median 2-3 digits▫ Ulna 4-5 digits

• A▫ DIP flexion of 2-5 digits

FLEXOR POLLICIS LONGUS..• O

▫ Anterior middle ½ of radius

▫ Interosseus membrane• I

▫ Palmar surface of base of distal 1st phalanx

• N▫ Median

• A▫ IP Flexion of thumb

EXTENSORS OF THE FINGERS..

EXTENSOR DIGITORUM COMMUNIS..• O: Common extensor tendon from lat.epicondyle of humerus, and

deep antebrachial fascia.• I: By 4 tendons, each penetrating a membranous expansion of the

dorsum of the 2-5 digits and dividing over the proximal phalanx into a medial and 2 lateral bands. The medial band inserts into the base of the middle phalanx while the lateral bands reunite over the middle phalanx and insert into the base of the distal phalanx.

• N: Radial, C6, 7, 8• A: Extends the MCP joints and, in conjunction with the lumbricals

and interossei, extends the IP joints of the 2-5digits. Assists in abd of the index, ring, and little fingers; and assists in ext and abd of the wrist.

EXTENSOR INDICIS..

• O▫ Dorsal surface lower

½ body of ulna▫ Interosseus

membrane• I

▫ Ulnar side of index finger’s EDC tendon

• N▫ Radial (posterior

interosseus)• A

▫ MCP and IP Ext of 2nd digit

EXTENSOR DIGITI MINIMI..

• O▫ Lateral epicondyle of

humerus• I

▫ Extensor expansion of 5th digit

• N▫ Radial (posteior

interosseus)• F

▫ MCP and IP extension of 5th digit

EXTENSORS OF THUMB..

EXTENSOR POLLICIS LONGUS..

• O▫ Posterior 1/3 ulna▫ Interosseus

membrane• I

▫ Posterior surface of base of thumb distal phalanx

• N ▫ Radial (posterior

interosseus)• A

▫ CMC, MCP and IP Ext of 1st digit

EXTENSOR POLLICIS BREVIS..

• O▫ Dorsal 2/3 of radius

• I▫ Dorsal surface of base

of proximal 1st phalanx• N

▫ Radial (posterior interosseus)

• A▫ CMC & MCP Ext of

thumb▫ CMC ABD of thumb

ABDUCTOR POLLICIS LONGUS..• O

▫ Posterior distal 2/3 of ulna▫ Posterior middle 1/3 of radius▫ Interosseus membrane

• I▫ Radial side of base of 1st

metacarpal• N

▫ Radial (posterior interosseus)• A

▫ CMC ABD & Ext of thumb

INTRINSIC MUSCLES

THENAR EMINENCE..

ABDUCTOR POLLICIS BREVIS..

• O▫ Scaphoid tuberosity▫ Trapezium ridge▫ Transverse carpal

ligament• I

▫ Lateral base f proximal 1st phalanx

• N▫ Median

• A▫ CMC & MCP ABD of

thumb

FLEXOR POLLICIS BREVIS..

• O▫ Superficial head –

trapezium▫ Deep head – trapezoid,

capitate and palmar ligaments of distal carpal bones

• I▫ Base of prximal 1st

phalanx on radial side▫ Extensor expansion

• N▫ Superficial – median▫ Deep – Ulnar

• A▫ CMC & MCP Flexion of

thumb

OPPONENS POLLICIS..

• O▫ Trapezium▫ Transverse Carpal

Ligament• I

▫ Radial side of 1st metacarpal shaft

• N▫ Median

• F▫ Opposition

HYPOTHENAR EMINENCE..

Abductor Digiti Minimi..

•O▫Pisiform

•I▫Ulnar side base of 5th

proximal phalanx•N

▫Ulnar•A

▫MCP ABD of 5th digit

Flexor Digiti Minimi..

•O▫Hamate bone▫Transverse carpal

ligament•I

▫Ulnar side of proximal 5th phalanx

•N▫Ulnar

•A▫MCP Flexion of 5th

digit

Opponence Digiti Minimi..

• O▫ Hook of hamate▫ Transverse carpal

ligament

• I▫ Ulnar border of entire

5th metacarpal bone

• N▫ Ulnar

• A▫ MCP flexion & rotation

of 5th digit

Palmaris Brevis..

•O▫Flexor retinaculum

•I▫Palmar surface skin

on ulnar side of hand

•N▫Ulnar

•A▫Wrinkles skin of

hand on ulnar side

Adductor Pollicis..• O

▫ 1.Oblique Head Capitate bone Bases of 2-3

metacarpals▫ 2.Transverse Head

Proximal 2/3 of palmar surface of 3rd metacarpal

• I▫ Ulnar side of base of 1st

proximal phalanx• N

▫ Ulnar• A

▫ CMC ADD of thumb

Lumbricals..

• O▫ Tendons of FDP

• I▫ Extensor expansion on

dorsal aspect of each digits radial side

• N▫ 1 and 2 – median▫ 3 and 4 – ulnar

• A▫ MCP flexion 2-5 digits▫ DIP & PIP ext 2-5

digits

Palmar Interossei..

• O▫ 1st – ulnar side base of 1st

metacarpal bone▫ 2nd – ulnar side of 2nd MC

bone▫ 3rd – radial side of 4th MC

bone▫ 4th – radial side of 5th MC

bone• I

▫ Extensor expansion of 2,4 and 5th digits

• N▫ Ulnar

• A▫ ADD of 1st, 2nd, 4th and 5th

digits towards midline of hand

Dorsal Interossei..• O

▫ 1st lateral head – ulnar side of 1st metacarpal bone

▫ 1st medial head – radial side of 2nd metacarpal bone

▫ 2nd, 3rd, 4th space between metacarpal bones

• I▫ 1st – radial side 2nd

proximal phalanx▫ 2nd – radial side of 3rd

▫ 3rd – Ulnar side of 3rd

▫ 4th – ulnar side of 4th

• N▫ Ulnar

• A▫ ABD of 2nd, 3rd, and 5th

finger from midline

To learn..

PULLEYS

5 ANNULAR & 3 CRUCIATE

•A1 -MINOR C1•A2 -MAJOR C2•A3 -MINOR C3•A4 -MAJOR•A5 -MINOR

ZONES OF THE HAND

Dorsum of the hand, wrist, and forearm are divided into 8 anatomic zones to facilitate classification and treatment of extensor tendon injuries

•Zone 1 (distal interphalangeal [DIP] joint)•Zone 2 (middle phalanx)•Zone 3 (proximal interphalangeal [PIP] joint)•Zone 4 (proximal phalanx)•Zone 5 (metacarpophalangeal [MCP] joint)•Zone 6 (dorsum of hand)•Zone 7 (wrist)•Zone 8 (dorsal forearm)

Extensor tendon zones; dorsal aspect of the hand and wrist

flexor tendon zones; volar aspect of the hand and wrist.

TENODESIS

As the wrist is extended , the thumb & fingers automatically flex due to the stretch placed on the extrinsic digital flexors. The flexion occurs passively, without effort from the subject..

A person with c6 level qudriplegia using tenodysis action to grasp a cup of water.

SWAN NECK DEFORMITY• Commonly seen in Rheumatoid arthritis• It causes PIP joint hyperextension and DIP joint flexion• It can be a result of musculotendinous imbalance or joint laxity• It can originate from abnormalities at the DIP jt, PIP jt.

MALLET FINGERAt DIP jointRupture of the terminal

extensor tendon attachment causes flexion at the DIP joint

Because of which there is inadequate extensor force at DIP jt, causing flexion at the joint.

The extensor force concentrates more proximally causing PIP joint hyperextension

• It has got three components

flexion of PIP jt

and

hyperextension of DIP jt

Boutonniere’s deformity

• This is because of Syonovial proliferation within the PIP jtContracture of the oblique retinacular ligament

The central band ruptures and the lateral band slips into the palmar direction.. To the PIP joint ,thus proximal

interphalangel joint looses its only means of extension.. Any tension in lateral bands produces flexion at the PIP…and

hyperextention at DIP

• It is caused by rupture of the ulnar collateral

ligament

• It is characterised by radial deviation deformity

of the MCP joint with secondary adduction of the

thumb at the metacarpal

GAMEKEEPER’S THUMB

ZIG-ZAG DEFORMITY OF THUMB

Commonly seen in RA.The thumb metacarpal

dislocates laterally at the CMC jt. Causing

hyperextention at MCP jt. The IP jt. Remains

partially flexed owing to the passive tension in the stretched and taut flexor

pollicis longus.The bow string of the

tendon of the EPL across the MCP jt creates a large

extensor moment arm,thereby magnifying

the mechanics of the deformity.

• It leads to ulnar deviation of the digits at the metacarpo-phalangeal joint.

•Mainly due to weakning of the capsuloligamentous structures as seen in RA.

Ulnar Drift

• caused due to injury to ulnar nerve.

• It causes MCP joint hyperextension and PIP jt and DIP jt flexion

• Ulnar nerve injury can be at the wrist or

elbow levelAt the wrist level the muscles

that may be affected are hypothenar muscles,

dorsal and palmar interrosei, ulnar two

lumbricals, adductor pollicis, deep head of flexor pollicis brevis

ULNAR CLAW HAND

If these muscles are paralysed the ulnar two fingers have no intrinsic support

And the extrisic muscle pull predominates. The extensor digitorum has a larger moment arm at MCP

joint and consequently pulls the joint in hyperextension. As a result FDP is stretched and results in PIP and DIP jt

flexion.

At the elbow level injury The muscles affected are flexor carpi ulnaris, flexor

digitorum profundus to ring and little finger This causes slight alteration in the claw hand deformity,

where DIP joint remains in extension due to paralysis of flexor digitorum profundus.

Due to injury to the median nerve CMC jt of the thumb goes in to ext. and

add. And MCP jts and IP jts in to flex. Injury at the wrist causes paralysis of the

thenar muscles and lumbricals of the index and ring fingers.

Hence there is insufficient balance to the extrisic muscles of the thumb

And the EPL has a large adductor moment arm at the CMC joint causing adduction and extension.

Consequently the FPL is stretched , causing MCP & IP joint flexion.

APE THUMB

PALMAR DISLOCATION OF MCP JOINT

Advanced stages of osteoarthritis in the hands of an 86-yearoldpianist. Note the carpometacarpal joint subluxation at the base of

eachthumb. Atrophy of the first dorsal interossei as well as nodules and

jointenlargements are apparent, but the individual is still functional.

Click below to know what your hands can do…

REFERENCES..

•CAROL OATIS•ELIZABETH KENDALL•DONALD NEUMANN•CYNTHIA NORKIN•CALLIET•www.googleimages.com

THANK YOU