Osseous Anatomy Essay

Radiological anatomy of the Wrist
Osseous Anatomy
The osseous structures of the wrist are the distal portions of the radius and ulna, the proximal and distal rows of carpal bones, and the bases of the metacarpals (Fig. 1). The proximal row of carpal bones consists of the scaphoid, lunate, triquetrum, and the pisiform. The distal row of carpal bones contains the trapezium, trapezoid, capitate, and hamate bones. The distal row of bones articulates with the metacarpal bases. The bases of the metacarpals articulate with the distal row of carpal bones and with each other. The proximal carpal row is termed an intercalated segment because forces acting on its proximal and distal articulations determine its position.

Figure.1 Gross anatomic section

a–d Normal carpal anatomy in axial CT source images. a Through the distal radioulnar joint. b Through the proximal carpal row at the level of the head of the capitate. c At the transition of the two carpal rows. d Through the distal carpal row.

Figure.4. a, b Normal carpal anatomy in coronal MPR images. a Through the middle of the carpus. b Through the palmar section of the carpal tunnel.

Figure.5. a–d Normal carpal anatomy in sagittal MPR images. a Through the scaphoid and the caphotrapeziotrapezoid joints. b Through the lunate. c At the level of the hook of the hamate. d At the level of the pisotriquetral joint. Triangular fibrocartilage complex(TFCC)
In 1981, Palmer and Werner introduced the term ‘‘triangular fibrocartilage complex’’ to describe the complex of soft tissues interposed between the distal part of the ulna and the ulnar carpus.

In most descriptions the TFCC is composed of the;
1. TFC proper,
2. Meniscus homologue,
3. Ulnar collateral ligament (UCL),
4. Dorsal and volar radioulnar ligaments,
5. Subsheath of the extensor carpi ulnaris tendon .
6. The ulnocarpal ligaments (ulno-lunate and ulno-triquetral) (Fig. 6).
TFC

Well-vascularized connective tissue lies between the two ulnar fascicles. A less common insertion is a broad-based striated fascicle attachment along the entire length of the ulnar styloid.
In an axial cross section, the TFC appears as an equilateral triangle. In the periphery (limbus), which consists of lamellar collagen fibers, the triangular fibrocartilage is thicker (up to5mm) than in the center. This difference in thickness causes a biconcave disk-shaped appearance in sagittal and coronal cross-sections. The relative length of the ulna must be considered when assessing the average thickness of the TFC. A short ulna (minus variant) is accompanied by a relatively thick TFC, and a long ulna (plus variant) by a relatively thin TFC.4
The blood supply of the TFCC originates from the ulnar artery (UA)(through the radiocarpal branches) and the anterior interosseous artery through the dorsal (DAIA)and palmar branches(PAIA). These vessels only peripheraly penetrate 10% to 40% of the TFCC, and the central and radial portions are avascular. This pattern of supply has direct implications to the healing potential following injury of the TFC and the radioulnar ligaments, with peripheral ulnar-sided detachments demonstrating a superior healing capacity following repair when compared with radial sided detachments.