The Wrist Joint
The wrist joint unites the hand with the forearm and is a complex articulation which affords two degrees of freedom to the hand: antero-posterior and transverse. These movements, together with those of pronation-supination of the forearm, position the han
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The Wrist Joint
The wrist joint unites the hand with the forearm and is a complex articulation which affords two degrees of freedom to the hand: antero-posterior and transverse. These movements, together with those of pronation-supination of the forearm, position the hand for its delicate prehensile function. The wrist associates mechanically the radiocarpal joint and the midcarpal joint.
6.1
The Radiocarpal Joint
The radiocarpal joint is the most important component of the wrist joint complex. It is ellipsoid and includes one special feature, the articular disc which functions as an articular surface as well as a ligament at the inferior radio-ulnar joint. The socket of the radiocarpal joint is formed by the articular surface at the lower end of the radius and by the attached articular disc which separates the wrist joint from the head of the ulna. The opposing convex surfaces of the scaphoid, lunate, and triquetral form one continuous egg-shaped surface. The ligamentous apparatus of the wrist joint is complex and its dissection difficult; there is a tendency to systematise the structures arbitrarily. Nevertheless, palmar, dorsal, and collateral ligaments can usually be distinguished. The palmar ligament comprises two reinforcements to the capsule, namely, the palmar radiocarpal ligament and the palmar ulnocarpal ligament. The palmar ligament is fan-shaped and includes six capsular bands which stabilise the bones in both rows of the carpus and the proximal pole of the scaphoid. The ligament has been described by Mayfield et al. (1976). There are two collateral ligaments associated with the radiocarpal joint. The radial collateral ligament extends from the styloid process of the radius to
the lateral face of the scaphoid with an extension to the trapezium; the ulnar collateral ligament attaches to the styloid process of the ulna and divides into two parts, one extending to the triquetral and the other to the pisiform.
6.2
The Midcarpal Joint
This joint lies between the two rows of carpal bones and is divided conventionally into two portions. The medial portion forms a saddle joint confronting the capitate and the hamate with the concavity formed by the scaphoid, the lunate and the triquetral. The lateral portion forms a plane joint confronting the scaphoid with the trapezoid and the trapezium. Volar or palmar ligaments of the midcarpal joint center on the head of the capitate constituting the radiate carpal ligament. The dorsal ligament reinforces the posterior ligament of the radiocarpal joint. The collateral ligaments, radial and ulnar unite laterally the scaphoid and the trapezium and medially the triquetral and the hamate. This complex ligamentous apparatus achieves two objectives: firstly, it anchors the other carpal bones around the capitate which becomes the centre of the carpal movements achieving the close-packed position; secondly, it synchronises the respective movements of the various components of the articulation. The wrist appears thus as a chain: the isolated and independent movements of the
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