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Wrist Complex
Wrist Complex
The entire upper limb is subservient to the hand:
Shoulder provides a dynamic base of support
Elbow allows hand to move toward and away from body
Forearm adjusts the approach of the hand to an object
Any loss of function in these areas reduces the function of he wrist and hand
The wrist provides minimal assistance of placing the hand in space (unlike the proximal joints).
This means that the primary functions of the wrist have little redundancy with the proximal joints
and cannot be replaced by compensation from the proximal joints.
Major Functions of the Wrist Complex
Control of length-tension relationships in the multiarticular hand huscles and in the fine
adjustment of grip. This occurs by the two compound joints: Radiocarpal (RC) and Midcarpal
(MC). The RC and MC joints are known as the Wrist Complex. They act to mediate fine
muscular control of the hand.
Radiocarpal
Structure:
Radius and radioulnar disc (proximal with the scaphoid, lunate
and distal, triquetrum -disc is part of articulation). The disc is interposed between
the ulna and carpals, therefore the ulna is not part of the articulation (the head of
the ulna can be removed without impairing wrist function).
The proximal row: scaphoid, lunate and triquetrum (pisiform not part of the
articulation) are connected by numberous interosseous ligaments resulting in a
sindle biconvex joint surface. The joint allows more flexion and ulnar deviation
than extension and radial deviation.
The joint is enclosed by a strong somewhat loose capsule reinforced by capsular
and intracapsular ingaments that are shared with the midcarpal (MC) joint.
Muscles cross both RC and MC. The pisiform is the only proximal carpal with a
muscular attachment (FCU).
Ligamentous Support
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Wrist Complex
Radial (lateral) collateral - attachment from the styloid process of the radius to the
scaphoid tubercle. AKA Radial Collateral Carpal Ligament. Stronger than the
Ulnar Collateral ligament
Ulnar Collateral lgament - attachment from the styloid process of the ulna to the
medial surface of the triquetrum. AKA Unlar Collateral Carpal Ligament. Weaker
of the two.
Other Ligaments - There are many other small igaments including palmar
radiocarpal, palmar ulnocarpal and dorsal radiocarpal.
Midcarpal - AKA Intercarpal. These are gliding joints
Structure:
Scaphoid, lunate and triquetrum (proximal row) with trapexium,
trapszoid, catpitate and hamate (distal row). This is a functional versus anatomical
joint. It does not have a joint capsule nor a single uninterrupted articular surface.
The joint capsule is continuous with each intercarpal articulation. Surfaces have a
reciprocal concave-convex configuration classified by some as a hinge (flexion/
extension) and others as condyloid (flexion/extension and deviation).
Allows more extension and radial deviation than flexion and ulnar (opposite the
RC).
Primary support from ligaments not capsule. Has many shared ligaments with RC.
Ligaments:
Ulnar collateral, Radial collateral, Dorsal radiocarpal, Palmar radiocarpal and
Ulnocarpal. Other intercarpal and interosseous ligaments serve to bind carpals
together and add little to function.
The joint capsule is formed by the dorsal and palmar intercarpal
ligaments as well as the radial and ulnar collateral ligaments.
Dorsal RC - bones of proximal to bones of distal
Palmar RC - scaphoid, lunate, triquetrum and pisiform to capatate
Radial Collateral - scaphoid to trapezium
Ulnar Collateral - triquetrum to hamate
The Radial and Ulnar give medial/lateral support
Despite extensive study and research, there are divergent conclusions regarding the
functions of the wrist complex.
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