Biomechanics of wrist complex

DR NEETI CHRISTIAN (PT)
MPT (Musculoskeletal & Sports)
1

 The wrist is the distal joint of the upper limb
and allows the hand to assume the optimal
position for prehension.
DR NEETI CHRISTIAN (PT) 2

 The articular complex of the wrist contain
two joints:
 The radio-carpal joint between the distal
radius and the proximal row of carpal bones.
 The mid-carpal joint between the proximal
and distal rows of carpal bones.

 Type of Joint
 Proximal and Distal articulating surfaces
 Basic Anatomy: Capsule
Ligaments
Muscles
 Kinematics: Axis of Motion
Osteo and Arthrokinematics
Normal ROM
End feel
 Synergistic and stabilizing action

 Radio-carpal joint is an ellipsoidal joint and
the carpal aspect presents two convexities
transverse convexity and antero-posterior
convexity.

 The distal radius has a
single continuous,
biconcave curvature that
is long and shallow side to
side (frontal plane) and
shorter and sharper
anteroposteriorly (sagittal
plane).

 The proximal joint surface is composed of
(1) the lateral radial facet, which
articulates with the scaphoid;
(2) the medial radial facet, which
articulates with the lunate; and
(3) the TFCC, which articulates with the
triquetrum, also with the lunate in the
neutral wrist.

•The radiocarpal joint is formed by the radius and radioulnar
disk as part of the triangular fibrocartilage complex (TFCC)
proximally and by the scaphoid, lunate,and triquetrum
distally.
The TFCC consists of the radioulnar disk and the various fibrous
attachments that provide the primary support for the distal
radioulnar joint.

 The radiocarpal joint is enclosed by a strong
but somewhat loose capsule and is reinforced
by capsular and intracapsular ligaments.

The ligaments of the radio-carpal joint are,,,,
1. collateral ligaments (lateral and medial)
2. The anterior ligaments [attached to the
anterior edge of the distal surface of the radius and
neck of the capitates]
3. Posterior ligament [forms a strap posteriorly].

Action of the ligaments:
 During adduction-abduction the medial and
lateral ligaments are active. Starting from
the rest position .
 Adduction  lateral ligament is stretched,
medial slackened
 Abduction  vice versa
 During flexion-extension the anterior and
posterior ligaments are most active.
 Flexion  posterior ligament stretched
 Extension  anterior ligament stretched

 Wrist Flexion: Flexor Carpi Ulnaris
Flexor Carpi Radialis
Palmaris Longus
 Wrist Extension:
Extensor Carpi Radialis Longus
Extensor Carpi Radialis Brevis
Extensor Carpi Ulnaris

 Radial Deviation: Flexor Carpi Radialis
Extensor Carpi Radialis Longus
 Ulnar Deviation: Flexor Carpi Ulnaris
Extensor Carpi Ulnaris

 The articular complex of the wrist has
basically two degree of freedom.

 Transverse axis takes place in the sagittal
plane with movement:
 Flexion the anterior palmar surface of the
hand moves towards the anterior aspect of
the forearm
 Extension the posterior dorsal surface of
the hand moves towards the posterior aspect
of the forearm.

 Antero-posterior axis takes place in the
frontal plane with movements:
 Adduction or ulnar deviation: the hand
moves toward the body and its medial (ulnar)
border forms an angle with the medial
border of the forearm.
 Abduction or radial deviation: the hand
moves away from the body and its lateral
(radial) border forms an angle with the
lateral border of the forearm.

 Range of movement of the wrist, range of
abduction does not exceed 15 , of adduction
is 45, of flexion is 85, and range of
extension is also 85.
 Movement of circumduction [combination of
the movement of flexion, extension,
adduction and abduction] takes place in two
axes of the wrist.
 End feel : Flexion ;Ext. ;UD: Firm
RD : Hard

OSTEOKINEMATICS ARTHROKINEMATICS
(Sliding Motion
of Proximal
Row of
Carpals)
(Rolling Motion of
Proximal Row of
Carpals)
Flexion Dorsal Volar
Extension Volar Dorsal
Ulnar Deviation Radial Ulnar
Radial Deviation Ulnar Radial

 Close packed Position: Full extension
 Loose packed Position: Neutral with slight
Ulnar deviation

 Extensor muscles of the wrist act
synergistically with the flexors of the fingers.
E.g. during extension of the wrist the fingers
are automatically flexes and, to extend the
fingers in this position, a voluntary
movement is required.
 Flexor muscles of the wrist act
synergistically with the extensors of the
fingers. When the wrist is flexed, extension
of the proximal phalanx follows
automatically.

•The compound proximal radiocarpal
joint surface is oblique, angled
slightly volarly and ulnarly.
• The average inclination of the distal
radius is 23 degrees.
•This inclination occurs because the
radial length (height) is greater
(approx.12 mm ) on the radial side
than on the ulnar side.
•The distal radius is also tilted volarly
with the posterior radius slightly
longer than the anterior (volar)
radius.

 The curvature of the distal radiocarpal joint
surface is sharper than the proximal joint
surface, which makes the joint somewhat
incongruent.
 Joint incongruence and the angulation of the
proximal joint surface result in a greater range
of flexion than extension and in greater ulnar
deviation than radial deviation for the
radiocarpal joint.

 The length of the ulna in relation to the
radius is also a factor which affects the
functions of wrist joint.
 Ulnar negative variance is described as a
short ulna in comparison with the radius at
their distal ends,
 ulnar positive variance, the distal ulna is
long in relation to the distal radius.

 The midcarpal joint is a functional rather
than anatomic unit because it does not form
a single uninterrupted articular surface.

 The extrinsic ligaments are those that
connect the carpals to the radius or ulna
proximally or to the metacarpals distally.
 The intrinsic ligaments are those that
interconnect the carpals themselves and are
also known as intercarpal or interosseous
ligaments.

 Volar Ligament includes Three bands:
1) The radioscaphocapitate (radiocapitate),
2) Radiolunate (radiolunotriquetral), and
3) Radioscapholunate
 The radial collateral ligament may be
considered an extension of the volar
radiocarpal ligament and capsule.
 The two intrinsic ligaments (scapholunate and
lunotriquetral) are maintains the scaphoid
stability.

•Dorsal Radiocarpal ligaments
•Dorsal Intercarpal Ligaments
•These ligaments forms a horizontal V
shape , adding to radiocarpal
stability.

 It is a unique combination of active muscular
and passive ligamentous and joint reaction
forces.
1. Flexion/Extension of the Wrist
2. Radial/Ulnar Deviation of the Wrist

 During flexion/extension of the wrist, the
scaphoid seems to show the greatest motion
of the three proximal carpal bones, whereas
the lunate moves least.
 As wrist extension is initiated from full
flexion,
(1) the distal carpal row moves on the
proximal carpal row;
(2) the scaphoid and distal row move on
the lunate/triquetrum;
(3) the carpals move as a unit on the
radius and TFCC to achieve.

 Wrist motion from full extension to full
flexion occurs in the reverse sequence.
 In the context of this conceptual framework,
the scaphoid participates at different times
in scaphoid-capitate, scaphoid-lunate, or
radioscaphoid motion.

 More Complex.
 The proximal carpal row displays a unique
“reciprocal” motion with radial and ulnar
deviation.
 In radial deviation, the carpals slide medially on
the radius, The carpal motion not only produces
deviation of the proximal and distal carpals
radially, but simultaneous flexion of the proximal
carpals and extension of the distal carpals.
 The Opposite motion occurs at Ulnar deviation.

 In full radial deviation, both the radiocarpal
and midcarpal joints are in close-packed
position.
 The ranges of wrist radial and ulnar deviation
are greatest when the wrist is in neutral.

 Carpometacarpal Joints of the Fingers
 Meta carpophalangeal joints
 Interphalangeal joints

 They have articulations between the distal
carpal row and the bases of the second
through fifth metacarpal joints.
 2nd metacarpal articulates primarily with the
trapezoid and secondarily with the trapezium
and capitate.
 3rd metacarpal articulates primarily with the
capitate,
 4th metacarpal articulates with the capitate
and hamate.
 5th metacarpal articulates with the hamate.

 All finger CMC joints are supported by strong
transverse and weaker longitudinal ligaments
volarly and dorsally.
 The ligamentous structure is primarily
responsible for controlling the total ROM
available at each CMC joint.

TCL
Intercarpal ligaments
•The proximal transverse arch, or carpal
arch,
forms the tunnel through which the
median nerve and long finger flexors
travel.
•The transverse carpal ligament and
intercarpal ligaments assist in maintaining
this concavity.

 The second through fourth CMC joints are
plane synovial joints with one degree of
freedom: flexion/extension.
 2nd and 3rd CMC joints are not mobile and
sometimes they have zero degrees of
freedom, but 3rd and 4th CMC joints are most
mobile.

•Three arches balance stability and mobility in
the hand.
1. Proximal transverse arch
2. Distal transverse arch
3. Longitudinal arch
•The proximal transverse arch is rigid, but the
other two arches are flexible, and are
maintained by activity in the hand's intrinsic
muscles.

 PROXIMAL TRANSVERSE ARCH
 A stable bony arch that forms the posterior
border of the carpal tunnel.
 The arch's integrity is maintained by a soft
tissue "strut" formed by the flexor retinaculum
or transverse carpal ligament (also called the
volar carpal ligament).
 This ligamentous strut connects the scaphoid
and trapezium on the arch's radial side with
the hamate on its ulnar side, and forms the
anterior border of the carpal tunnel.

2) DISTAL TRANSVERSE ARCH
 Hertling and Kessler (p. 257) call this the
metacarpal arch, because it is formed by the
metacarpal heads; metacarpals 2 and 3 are stable
while 4 and 5 are relatively mobile.
 You can observe the arch's combination of "radial"
stability and "ulnar" mobility by loosely closing your
fist, then squeezing more tightly, when you will
observe movement in the more mobile fourth and
fifth metacarpals.
3) LONGITUDINAL ARCH
 Observe this arch's behavior as you loosely close
your fist. Tighten the fist and watch the fourth and
fifth metacarpals.

 The arches provide a balance between
stability and mobility for grasping.
 For instance, we produce the so-called
"chuck grasp" by using the more stable
second and third metacarpals, instead of
the more mobile fourth and fifth
metacarpals.
 Therapeutic splints must support these
three arches.

 The convex metacarpal head proximally and
the concave base of the first phalanx distally.
 The MP joint is condyloid with two degrees of
freedom: 1)flexion/extension
2)abduction/adduction.

Metacarpophalangeal (MP)
 condyloid, biaxial joints
 joint's palmar aspect is palpable at level of distal palmar
crease
 proximal joint surface is convex and distal surface is concave
 roll and glide occur in same direction
 anterior with flexion
 posterior with extension.
 large metacarpal joint surface
 a fibrocartilaginous volar plate is lined with hyaline cartilage
so that it augments or enlarges the proximal phalanx' relatively
small articular surface.
 superficial to volar plate is the transverse metacarpal ligament
 joint capsule supported by two collateral ligaments
 close-packed position:
 MP joints of digits 2 through 5: close-packed in flexion; you cannot
abduct or adduct these joints when they are flexed.
 MP joint of thumb: close-packed in extension

 The MP joint is surrounded by a capsule that is generally
considered to be lax in extension.
 Given the incongruent articular surfaces, capsular laxity in
extension allows some passive axial rotation of the
proximal phalanx.
 Two collateral ligaments at the volarly located transverse
metacarpal ligament enhance joint stability.

 It is a unique structure at MCP joint.
 It improves joint congruency.
 It also provides stability to the MP joint by
limiting hyperextension.
 It also provides indirect support to the
longitudinal arch.
 The volar plate is composed of
fibrocartilage.

Volar
plateMC
P1
•The volar plate attaches to the base of
the proximal phalanx.
•The plate lies deep to the MP joint
capsule and the deep transverse
metacarpal ligament volarly.
In MP joint flexion, the flexible
attachments of the plate allow the
plate to slide proximally on the
metacarpal head without preventing
motion.
The collateral ligament proper is
loose in MP joint extension, The
reverse occurs in MP joint flexion.

 The four volar plates and their respective
capsules of the MP joints of the fingers also
interconnected superficially by the deep
transverse metacarpal ligament.

•Dorsal to the deep transverse metacarpal ligament are sagittal
bands on each side of the metacarpal head that connect each
volar plate (via the capsule and deep transverse metacarpal
ligament) to the ED tendon and extensor expansion.
• The sagittal bands help stabilize the volar plates over the four
metacarpal heads.

Annular pullies
Deep transverse
metacarpal
ligament

 Each IP joint is a true synovial hinge joint
with one degree of freedom
(flexion/extension), a joint capsule, a volar
plate, and two collateral ligament.

 uniaxial hinge joints
 supported by two collateral ligaments, and by
smaller versions of a volar plate.
 Like MP joint, proximal joint surface is convex
and distal surface is concave
 roll and glide occur in same direction
 anterior with flexion
 posterior with extension
 close-packed in extension

 The muscles of the fingers and thumb that
have proximal attachments above the wrist
(radiocarpal joint) are known as extrinsic
muscles.
 whereas those with all attachments distal to
the radiocarpal joint are known as intrinsic
muscles.

Two muscles:
 FDS- primarily flexes the PIP joint, but it also
contributes to MP joint flexion.
 FDP- flex the MP, PIP, and the DIP joints and
is considered to be the more active of the
two muscles.

 Optimal function of the FDS and FDP muscles
depends not only on stabilization by the wrist
musculature but also on intact flexor gliding
mechanisms.
 The gliding mechanisms consist of the flexor
retinaculae, bursae, and digital tendon
sheaths.

 As the tendons of the FDS and FDP muscles
cross the wrist to enter the hand, they first
pass beneath the proximal flexor
retinaculum and through the carpal tunnel.
 The radial and ulnar bursae contain a
synovial-like fluid that minimizes frictional
forces.
 The FDS and FDP tendons of each finger pass
through a fibro-osseous tunnel that
comprises five transversely oriented annular
pulleys as well as three obliquely oriented
cruciate pulleys.

Ulnar
bursa
Radial bursaFlexor retinaculum
and TCL
Digital tendon
sheath

Flexor pulley system consists of following
• Palmar Aponeurosis Pulley
• 5 Annular Pulleys
• 3 Cruciform Culleys.
Together, these form a fibro-osseous tunnel on the palmar aspect of
the hand through which passes the deep and superficial
flexor tendons.

 We can extend the PIP and DIP joints without
also extending the MP joints.
 But we can't extend the PIP joint without
extending the DIP joint at the same time.
 Flexing only the DIP joint without also flexing
the PIP joint is difficult.
 Full (active or passive) flexion of the PIP
joint prevents active extension of the DIP
joint.

 The extensor mechanism is an elaboration of
the extensor digitorum (ED) tendon on the
dorsum of each phalanx.
 The extensor indicis (EI) and the extensor
digiti minimi (EDM) insert into the extensor
mechanisms of the second and fifth digits,
respectively.

The ED tendon attaches by a tendinous slip to the
proximal phalanx, through which it extends the MP joint.
The central tendon (or "slip") proceeds dorsally to
attach to base of middle phalanx, where tension can
extend the PIP joint.

• Two lateral bands proceed on either side of dorsal
midline and rejoin before attaching to the distal
phalanx. Tension in the lateral bands extends the DIP
joint.
• The extensor hood surrounds the MP joint laterally,
medially, and dorsally, and receives tendinous fibers
from the lumbricales and interossei.

 Dorsal interossei (DI)
 The dorsal interossei attach proximally
between adjacent metacarpals.
 Abduction is stronger at the second MP
joint because the most of the first DI's
muscle fibers attach directly to the
second proximal phalanx.
 Abduction of the fourth MP joint is
relatively weak because the fourth DI
attaches largely to the extensor
mechanism itself.
• The dorsal interossei produce MP
abduction and, in certain instances, MP
flexion.

 Palmar interossei (PI):
 palmar interossei attach
proximally to a
metacarpal, and distally to
the same digit's proximal
phalanx and/or its extensor
mechanism.
 They produce MP adduction
and, in certain instances,
MP flexion.
 They also produce PIP and
DIP extension when they
introduce tension into the
extensor mechanism.

 Lumbricales:
 The four lumbricales attach proximally to the
tendons of the flexor digitorum profundus, and
distally to the extensor mechanism on its radial
side at the level of the lateral bands.
 If they act alone, they produce MP flexion. They
also produce PIP and DIP extension when they
introduce tension into the extensor mechanism.
 They permit a dynamic interaction between
flexors and extensors.
 Their attachments transmit their force to both
the Flexor and the extensor mechanism.
 Specifically, lumbrical activity:
 increases passive tension in the extensor mechanism.
 decreases passive tension in FDP tendon's distal
portion.

 Prehension activities of the hand involve the
grasping or taking hold of an object between
any two surfaces in the hand; the thumb
participates in most but not all prehension
tasks.

 Two types of grasp are differentiated according
to the position and mobility of the thumb's CMC
and MP joints. (Smith, Weiss, & Lehmkuhl, 1995, pp.
216-219; Hertling & Kessler, 1996,pp.259-260)
1. Power grip
2. Precision grip

 The fingers in power grip usually function in
concert to clamp on and hold an object into
the palm.
 The palm is likely to contour to the object as
the palmar arches form around it. The thumb
may serve as an additional surface to the
finger-palm vise by adducting against the
object, or it may be removed from the
object.
 In this, the hand's position is static.

A. Cylindrical grip
 It may orient the finger tips toward the
thumb. This is accomplished by ulnarly
deviating the MP joints using the interossei
muscles.
 eg: Holding a glass or any object.

B. spherical grip (Hand curves to hold a round or
sphere shaped object)
 eg: Holding a ball, Grasping a jar when twisting
the lid open.

C. Hook grip (MP extended with flattening of
transverse arch; the person may or may include
the thumb in this grasp)
 eg: Holding a bag, barbell

D. Lateral prehension is a rather unique form of
grasp. Contact occurs between two adjacent
fingers.The MP and IP joints are usually
maintained in extension.

 Muscles are active that abduct or oppose the
thumb; the hand's position is dynamic.
 The three varieties of precision grasp:
 pad-to-pad prehension, tip-to-tip
prehension, and pad-to-side prehension.
 Each tends to be a dynamic function with
relatively little static holding.

 Wrist
 extended 20 degrees
 ulnarly deviated 10 degrees
 Digits 2 through 5
 MP joints flexed 45degrees
 PIP joints flexed 30-45 degrees
 DIP joints flexed 10-20 degrees
 Thumb
 first CMC joint partially abducted and opposed
 MP joint flexed 10 degrees
 IP joint flexed 5 degrees

 When therapists immobilize a patient's hand,
they often position it this way.
 During a period of immobilization, the resting
lengths of the hand's ligaments and muscles
change.
 This hand position provides the best balance of
resting length and force production so the hand
can function when the patient mobilizes it again.
 In making splints for the hand, a normal
transverse arch is maintained and the thumb is
in abduction and aligned with pads of all four
fingers.

 Median:
 Often due to carpal tunnel sd.
 Wasting of thenar eminence
 Decreased thumb function, especially opposition.

 Ulnar:
 Damage to ulnar nerve can occur with trauma to
elbow region. Ulnar neuropathy is a frequent
complication of diabetes mellitus
 Wasting of web space and interosseous spaces.
 Affects strength of intrinsic muscles of hand, so
person can't hold a piece of paper between
extended but adducted fingers

 Radial:
 Associated with gunshot or stab wounds, fracture
of humerus, "Saturday night palsy."
 person demonstrates a "dropped wrist," and
cannot reposition thumb.
 lack of wrist extension may cause hand grip to be
weak.

 Carpal tunnel syndrome (CTS) is an entrapment
neuropathy caused by compression of
the median nerve as it travels through the wrist's
carpal tunnel.
 It is the most common nerve
entrapment neuropathy, accounting for 90% of
all neuropathies.
 Early symptoms of carpal tunnel syndrome
include pain, numbness, and paresthesias.
 Pain also can radiate up the affected arm. With
further progression, hand weakness, decreased
fine motor coordination, clumsiness, and thenar
atrophy can occur.

 De Quervain's Tenosynovitis is a painful inflammation
of tendons on the side of the wrist at the base of the
thumb.
 These tendons include the extensor pollicis brevis
(EPB) and the abductor pollicis longus (APL).
 The pain, which is the main complaint, gets worse
with abduction of the thumb, grasping action of the
hand and an ulnar deviation of the wrist. Thickening
and swelling can also be present.

 A wrist sprain is an injury to the ligaments of the
wrist region.
There are three grades:
1. A mild overstretching of the ligaments, without
joint instability.
2. A partial rupture of the ligaments, with no or
mild joint instability.
3. A complete rupture of a ligament with severe
joint instability.

HAND AND WRIST OSTEOARTHRITIS:
 Hand osteoarthritis(OA) is a common chronic
condition involving one or more joints of the thumb
and fingers. It is associated with pain, reduced grip
strength, loss of range of motion (ROM), and joint
stiffness, leading to impaired hand function and
difficulty with daily activities.
 Estimates of the prevalence of symptomatic hand OA
range from 13% to 26% and are greater in women.

Rheumatoid arthritis (RA) :
 It is a systemic autoimmune disease characterized by
inflammatory arthritis and extra-articular involvement.
 C/F : Polyarthritis of small joints of hands: proximal
interphalangeal (PIP), metacarpophalangeal (MCP) joints
and wrist.
 Stiffness in the joints in the morning may last up to several
hours, usually greater than an hour. The patient may have
a "trigger finger" due to flexor tenosynovitis.

 Complex regional pain syndrome (CRPS) is a
term for a variety of clinical conditions
characterized by chronic persistent pain and
are subdivided into Type I and Type II CRPS.
 It is a condition that can develop after a limb
trauma and appears mostly in one or more
limbs.

 Colles fracture
 Smith s fracture
 Scaphoid fracture
 Lunate Instability
 Hamate frcture
 Metacarpal fracture

 Ape thumb :Paralysis of thenar muscles due
to Median nerve injury or polio or leprosy.
 Claw hand : Inability to extend fingers from
IP joints due to ulnar nerve injury.
 Deformities of RA

 Dupuytren contracture is a progressive disease of the palmar
fascia which results in shortening, thickening and fibrosis of
the fascia and aponeurosis of the palm.
 The most commonly affected digits are the third and fourth
digits.
 The disease begins in the palm as painless nodules that form
along longitudinal lines of tension.
 The nodules form cords that produce contracture deformities
within fascial bands and tissues of the hand.

 A crush injury is defined as compression of the
extremities causing muscular and neurological
disturbance and in the upper limb is sustained
when the fingers, hand or wrist are caught
between two surfaces (sharp, blunt, smooth or
irregular) forcibly producing damage to the skin.

Biomechanics of wrist complex

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