Wrist Complex1

Wrist and Hand complex  Entire upper limb is subservient to the hand  Any loss of function in the upper limb regardless of

the segment translates into diminished function of its most distal joints  There is a symbiotic relation between the hand and the brain  Hand cannot function without the brain to control it and the brain needs the hand as a primary tool of expression

Wrist Complex Wrist (carpus) consists of : b. Radio carpal c. Mid carpal joint • Two articulations are collectively referred to as the wrist complex • Each joint proximal to the wrist serves to broaden the placement of the hand in space and to increase the degrees of freedom available to the hand •

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Shoulder acts as the dynamic base of support for the upper limb Elbow allows the hand to approach or extend away from t he body Forearm adjusts the approach of the hand to an object Wrist serves for placement of the hand in space but to a minor degree Major contribution of wrist complex is to control length-tension relationship in the multiarticular hand muscles and to allow fine adjustment of grip

Wrist is considered to be the most complicated joint of human body • Wrist complex is biaxial joint iii. Flexion/Extension- Coronal axis iv. Radial/Ulnar deviation – AP axis • ROM of the wrist is variable and reflect the differences in carpal kinematics due to factors such as ligamentous laxity, shape of articular surfaces and constraining effects of muscles •

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Flexion - 78 - 85° Extension - 60 - 85° Radial deviation - 15 - 21° Ulnar deviation - 38 - 45° Functional Range: 10°of wrist flexion to 35 °of wrist extension

Structural Components of Wrist Complex: Radiocarpal joint Structure: • Proximal joint surface is formed by d. Lateral Radial facet with scaphoid e. Medial Radial facet with lunate f. TFCC with triquetrum • Ulna doesn't participate in the radio carpal joint

Distal joint surface if formed by the scaphoid, lunate & triquetrum • Pisiform which,anatomically is part of the proximal row doesn't participate in the radio carpal articulation •

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Pisiform functions as a sesamoid bone to increase MA of Flexor carpi ulnaris FCU is the only muscle that crosses the radio carpal joint and attaches to any of the bones of the proximal carpal row Pisiform is loosely connected to triquetrum below, hence forces applied on pisiform by FCU are translated not to the triquetrum on which it sits but to the hamate and fifth metacarpal via pisiform ligaments This helps to increase the moment arm of the muscle thereby increasing its efficiency as an ulnar deviator

Radio carpal joint is enclosed by a strong but loose capsule and reinforced by capsular and intracarpal ligaments • Curvature of distal radiocarpal joint surface is sharper than proximal surface • Joint incongruence and angulation of proximal joint surface result in greater flexion range then extension and in greater ulnar deviation than radial deviation •

Midcarpal joint Structure: • Articulation between scaphoid, lunate and triquetrum proximally and the trapezium, trapezoid,capitate and hamate distally • Midcarpal joint is a functional rather than anatomic joint • Midcarpal joint surfaces are complex with an overall reciprocally concave-convex configuration

The distal carpal row and the metacarpals behave as one unit • This helps in equal distribution of load across the proximal and distal carpal rows • The joint has two degrees of freedom of movement: flexion/extension, radial/ulnar deviation • Functional union of the distal carpals with each other and with their contiguous metacarpals not only serve the wrist complex but also are the foundation for transverse and longitudinal arches of hand •

Ligaments of Wrist Complex Ligaments help in articular stability, guide and check motion between and among the carpals • They can be divided into C. Extrinsic (ligaments connecting carpus to the radius, ulna or metacarpals) D. Intrinsic (connecting the carpals among themselves) •

Volar Carpal Ligaments : II. EXTRINSIC : • Radio carpal ligament : d. Radio Scaphoid e. Radio triquetral f. Radio capitate • Ulnocarpal ligament : h. Ulnolunate i. Ulnocapitate (Ulnotriquetral) 10) Radial Collateral ligament 11) Ulnar Collateral ligament

INTRINSIC : Scapholunate ligamentprovides stability of the scaphoid and wrist. • Lunotriquetral ligamentinjury to this ligament leads to lunate instability Dorsal Carpal Ligaments : • Dorsal radiocarpal ligament: attaches to the triquetrum • Dorsal intercarpal ligament: attaches from the triquetrum to the scaphoid, lunate and trapezium I. •

Ulnar variance: • Negative ulnar variance -ulna is normally shorter than radius distally,allowing ulnar deviation of wrist

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Positive ulnar variance -shortening of radius which occurs in comminuted colle’s fracture limiting ulnar deviation

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Kienbock's Disease Osteonecrosis of lunate bone,due to avascular necrosis Cause is unknown Single or repetitive traumatic micro fractures that result rupture of the ligaments and vessels around the lunate leading to vascular compromise Recurrent compression of lunate between capitate & distal radius which disrupts intraosseous structures Extreme wrist positions and/or repetitive compression loading

Function of the wrist complex. Movement at Radiocarpal & Midcarpal joints: • Motion at these joints are caused by a combination of active muscular and passive ligamentous and joint reaction forces • No muscular forces are applied to the proximal carpal row as there are no muscular attachments • FCU inserts into the pisiform but the force is transmitted to the distal bone • There are abundant passive forces

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Proximal carpals therefore, are effectively a mechanical “link” between the radius and the distal carpals and the metacarpals to which muscular forces are applied Proximal carpal row acts as a intercalated segment, a relatively unattached middle segment of a three segment linkage The function of this link is to collapse and move in the opposite direction as compared to the segments above and below

When compressive forces are applied across the wrist joint, e.g., as in wrist extension, it is believed that the proximal carpal row(scaphoid, lunate and triquetrum)moves into flexion and pronation and the distal carpals move into extension • This helps to increase co-aptation of the mid carpal articular surfaces •

Flexion/Extension of the wrist : • During flexion and extension scaphoid shows the greatest motion of the three proximal carpals while the lunate shows the least • When extension is initiated by the extensor muscles from flexed position the distal carpal row along with the metacarpals glide on the relatively fixed proximal bones (scaphoid, lunate and triquetrum) • The distal carpal row glides in the same direction as the movement of the hand (Capitate on scaphoid)

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When the wrist reaches a neutral position, the ligaments spanning the capitate and scaphoid draw these bones into a close packed position Continued extensor force, moves the distal carpal row and the scaphoid on a relatively fixed lunate and triquetrum (Scaphoid on lunate) At about 45° of wrist hyperextension, the scapholunate interosseous ligament brings the scaphoid and the lunate into close-packed position This unites all carpals and causes all carpals function as a single unit (Scaphoid on radius) Wrist complex extension is completed as the proximal articular surface move as a solid unit on the radius and radio ulnar disk

In this whole activity scaphoid participates at different times in scaphoid-capitate, scaphoid-lunate or radio scaphoid motion • All ligaments become taut as full extension is reached and the entire wrist complex is close packed • Wrist flexion from full extension, the reverse movement occurs •

Radial/Ulnar Deviation of the Wrist: • Radial Deviation involves deviation of proximal and distal carpals radially and a simultaneous flexion of the proximal carpals and extension of the distal carpals • During these movements distal carpals move as a relatively fixed unit • Magnitude of the scaphoid flexion depends upon ligament laxity with women having greater laxity than males • The maximum range of deviation is possible when the wrist is in neutral position • In complete extension all the carpals are locked and it is the close packed position for the joint hence little movement is possible

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In flexion all the carpals have completed their ROM and hence it is a loose packed joint position with little movement available In full radial deviation, both the radio carpal and mid carpal joints are locked Functional wrist motions of 60° extension, 54° flexion, 40° of ulnar deviation, and 17° of radial deviation are required Opposite movements of the proximal and distal carpals occur in ulnar deviation Wrist extension and ulnar deviation is the position of maximum scapholunate contact