The document discusses the anatomy and biomechanics of the wrist and hand complex, detailing the structure and function of various joints such as the radiocarpal and midcarpal joints, as well as the ligaments and muscles associated with wrist movement. It covers the ranges of motion, the impact of different joint alignments on function, and distinct patterns of instability that may arise due to ligament injuries. Additionally, the document describes the mechanics of finger flexion and extension, including the roles of extrinsic and intrinsic muscles in fine motor tasks and grasping movements.

1. WRIST AND HAND
COMPLEX
By
SOMA BALAJI PT
MPT MSK & SPORTS

2. INTRODUCTION
• The wrist consists of two compound joints: the radiocarpal and the
midcarpal joints.
• The shoulder serves as a dynamic base of support.
• The elbow allows the hand to approach or extend away from the body.
• The forearm adjusts the approach of the hand to an object.
• Unlike the more proximal joints, wrist serves placement of the hand in
space to only a minor degree.
• Wrist complex contributes to control the Length-Tension relationships
in multiarticular hand muscles and allows fine adjustments in
movements.

3. • Wrist complex is biaxial motions of extension/flexion around a coronal
axis and ulnar deviation/radial deviation around an antero posterior axis.
MOVEMENT ROM
Flexion 65-85
Extension 60-85
Radial deviation 15-21
Ulnar deviation 20-45

4. Radiocarpal Joint Structure
• The radiocarpal joint is formed by the radius and radioulnar disc as part of the triangular
fibrocartilage complex (TFCC) proximally and by the scaphoid, lunate, and triquetrum distally

5. Proximal and Distal Segments of the Radiocarpal Joint
• The distal radius has a single, continuous, biconcave
curvature that is long and shallow from side to side
(in the frontal plane) and shorter and sharper antero-
posteriorly.
• 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.
3. The triangular fibrocartilage complex.
The average inclination of the distal radius is 23°.

6. • The triangular fibrocartilage complex consists of the radioulnar disc
and the various fibrous attachments that provide the primary support
for the distal radioulnar joint.

7. • Ulnar negative variance is described as a short ulna in comparison
with the radius at the distal end, whereas in ulnar positive variance, the
distal ulna is long in relation to the distal radius.
• Ulnar positive variance, there is a potential for impingement of the
triangular fibrocartilage complex structures between the distal ulna
and the triquetrum.
• Ulnar negative variance may result in abnormal force distribution
across the radiocarpal joint with potential degeneration at the
radiocarpal joint.

9. • Avascular necrosis of the lunate,
Kienbock’s disease, has been associated
with ulnar negative variance.

10. Midcarpal Joint Structure
• The midcarpal joint is the articulation between the scaphoid, lunate,
and triquetrum proximally and the distal carpal row composed of the
trapezium, trapezoid, capitate, and hamate.
• Distal row move as an almost fixed unit.
• Capitate and hamate are most strongly bound together.
• Union of the distal carpals also results in nearly equal distribution of
loads across the scaphoid trapezium-trapezoid, the scaphoid-capitate,
the lunate capitate, and the triquetrum-hamate articulations.

11. WRIST LIGAMENTS

12. Function of the Wrist Complex
Movements of the Radiocarpal and Midcarpal Joints
Motions at the radiocarpal and midcarpal joints are caused by a rather unique
combination of active muscular and passive ligamentous and joint reaction forces.
FLEXION / EXTENSION
• During flexion/extension of the wrist, the scaphoid shows the greatest motion of
the three proximal carpal bones, whereas the lunate moves the least.
• Flexion and extension of the radiocarpal joint occurs almost exclusively as
isolated flexion and extension of the proximal carpal row simultaneous but
lesser amounts of radial/ulnar deviation and pronation/supination of two or all
three proximal carpal bones.

13. Conceptual Framework
1. Motion in this conceptual framework begins with the wrist in full flexion.
• Active extension is initiated at the distal carpal row. The distal carpals glide on the relatively
fixed proximal bones.
• The distal carpal row effectively glides in the same direction as motion of the hand.
• When the wrist complex reaches neutral the ligaments spanning the capitate and scaphoid
draw the capitate and scaphoid together into a close-packed position.
2. Continued extensor force now moves the combined unit of the distal carpal row
and the scaphoid on the relatively fixed lunate and triquetrum.
• At 45° of extension of the wrist complex, the scapholunate interosseous ligament brings the
scaphoid and lunate into close-packed position.
3. Completion of wrist complex extension occurs as the proximal articular surface of
the carpals move as a relatively solid unit on the radius and triangular
fibrocartilage complex.
Wrist motion from full extension to full flexion occurs vice versa

15. Radial/Ulnar Deviation of the Wrist
• The proximal carpal row displays a unique “reciprocal” motion with radial and ulnar
deviation.
• In radial deviation, the carpals slide ulnarly on the radius.
• Carpal motion not only produces reciprocal deviation of the proximal and distal
carpals with radial deviation, but simultaneous flexion of the proximal carpals and
extension of the distal carpals.
• The opposite motions of the proximal and distal carpals occur with ulnar deviation.
• In full radial deviation, both the radiocarpal and midcarpal joints are in close-packed
position.
• The ranges of wrist complex radial and ulnar deviation are greatest when the wrist is
in neutral flexion/extension.

17. Wrist Instability
Dorsal intercalated segmental instability
• Scapholunate ligament injury removes synergetic stabilization.
• Scaphoid collapses into flexion- sublaxation(static & dymanic).
• Lunate and triquetrum –extend –follow natural tendency all act like
unconstrained segment.
• Carpals move in to flexion.
• Zigzag pattern of all three segments.
• Contact pressure between radius and scaphoid increases.
• Capitate can migrate between scaphoid and lunate – degeneration.
• Scapholunate advanced collapse (prolonged/long term).

18. Volar intercalated segmental instability
• Lunotriquetral ligament injury.
• Lunate and scaphoid fall in to flexion and triquetrum is unable to join
lunate to counter balance the movement of scaphoid.
• Ulnar perilunate instability also know as VISI.
• Triquetrum extends with other distal carpals, hence proximal carpal
stability is important for wrist function.

19. Volar wrist muscles (Flexors)
• Six muscles cross volar aspect that helps in wrist flexion.
1. Flexor carpi radialis
2. Flexor carpi ulnaris
3. Flexor digitorum profundus.
4. Flexor digitorum superficialis
5. Flexor pollicis longus
6. Palmaris longus

20. Dorsal wrist muscles
• Total of 9 muscles, 3 are primary and remaining are secondary
Primary
1. Extensor carpi radialis longus
2. Extensor carpi radialis brevis
3. Extensor carpi ulnaris
Secondary
1. Extensor digitorum communis
2. Extensor indicis proprius
3. Extensor digiti minimi
4. Extensor pollicis longus
5. Extensor pollicic brevis
6. Abductor pollicis longus

22. Hand Complex
• Hand consist of 5 digits (4 finger + 1 thumb).
• Each digit has a carpometacarpal joint and metacarpophalangeal
joint.
• The fingers each have 2 inter phalangeal joints.
-proximal inter phalangeal joint (PIP).
-distal inter phalangeal joint(DIP).
There are 19 bones and 19 joints distal to the carpals that make up the hand
complex.

23. Carpometacarpal joints of the fingers
• Composed of the articulations between the distal carpals row and the
bases of 2nd
to 5th
metacarpal joints.
• 2nd
metacarpal joint articulates with primarily - trapezoid,
secondarily – trapezium and capitate.
• 3rd
– capitate.
• 4th
– capitate and hamate.
• 5th
– hamate.
• Carpometacarpal joints are supported by strong transverse and weak
longitudinal ligaments volar and dorsally.

25. • Deep transverse metacarpal ligaments spans the head of the 2nd
through 4th
metacarpal volarly.
• Proximal transverse arch is formed by the trapezoid, trapezium,
capitate and hamate.
• Ligaments that maintain the arch are – transverse carpal ligament,
transversely oriented intercarpal ligaments.
ROM of carpometacarpal joint
2nd
to 4th
– 1 degree freedom - flexion/extension(plane synovial).
2nd
and 3rd
– immobile.
4th
– flexion/extension.
5th
– 2 degree freedom – flexion/extension, abduction/adduction

26. Metacarpophalangeal joints of finger
• Articulation between convex metacarpal head proximally and concave metacarpal
base distally.
• Condyloid joint – 2 degree freedom – flex/exte, abd/add.
• Joint is surrounded by capsule that is lax in extension.
• Collateral ligament proper, accessory collateral ligament enhance stability of
joints(radial and ulnar collateral lig).
• Flexion/extension increases radially and ulnarly with index finger – 90deg flexion,
little finger – 110deg flexion.
• Hyperextension varies among individuals based on this flexibility.
• The range of abduction/adduction is maximal in metacarpophalaneal joint
extension.

28. Interphalangeal joints of fingers
• PIP and DIP joints composed of head of phalanx(proximal) and the
base of phalanx (distal).
• Synovial joint with 1deg of freedom – flex/ext.
• Total range of flexion and extension available to the index finger is
greater at the proximal interphalangeal joint(100-110), distal
interphalangeal joint(80).

29. Extrinsic finger flexors
• Extrinsic muscles – proximal attachments of wrist(muscles of fingers
and thumb).
• Intrinsic muscles – distal attachments of wrist.
• Extrinsic (flexion of fingers)
- Flexor digitorum superficialis – flex PIP and MCP joints.
- Flexor digitorum profundus – flex MCP, PIP & DIP joints.

30. Mechanism of finger flexion
• Flexor digitorum superficialis & flexor digitorum profundus helps in
flexor gliding mechanism.
• Gliding mechanism consist of the flexor retinacula bursae and digital
tendon sheath.
• Consist of 5 transversely oriented annular pulleys(A1-A5) and 3
cruciate pulleys(C1-C3).
• Function and location as :
- Keep the flexor tendon close to bone
- Allowing only minimum amount of bowstringing
- Migration volarly from its axis

32. Finger Extension
• Muscles that pass from forearm to hand beneath extensor
retinaculum.
• Extensor digitorum communis, extensor indicus propius, extendor
digiti minimi.
• Junctura tendinae – one to another finger tendons interconnected.
• The dorsal interossei or volar interossei and lumbrical muscles are the
active component of the extensor mechanism.

34. Structure of the Thumb
• Carpometacarpal /trapeziometacarpal joint of the thumb is the
articulation between the trapezium and base of first metacarpal.
• It is a saddle variety allows 2 degree of ROM – flex/ext,
Abd/Add.,Circumduction(opposition).
Intrinsic Thumb Muscles (5 thenar muscles)
1. Oppones pollicis
2. Abductor pollicis brevis
3. Flexor pollicis brevis
4. Adductor pollicis
5. 1st
volar interossci muscles
Extrinsic Thumb Muscles
1. Flexor pollicis longus
2. Extensor pollicis brevis
3. Extensor pollicis longus
4. Abductor pollicis longus

35. • PREHENSION – refers to grasping or holding.
• Different types of power grips,Cylindrical, spherical, hook grip and
lateral prehension.

36. Precision Handling
• Require much motor control and they are more dependent on intact
sensation.
• 3types of precision handling.
1. Pad to pad
2. Tip to tip
3. Pad to side

38. • Tenodesis – phenomena of using active wrist extension to passively
close the fingers & passive wrist flexion to passively open the fingers.