Triangular fibrocartilage

, showing the synovial cavities. (Articular disc labeled at center right.) Triangular fibrocartilage disc The triangular fibrocartilage disc (TFC) is an articular discus that lies on the pole of the distal ulna. It has a triangular shape and a biconcave body; the periphery is thicker than its center. The central portion of the TFC is thin and consists of chondroid fibrocartilage; this type of tissue is often seen in structures that can bear compressive loads. This central area is often so thin that it is translucent and in some cases it is even absent. The peripheral portion of the TFC is well vascularized, while the central portion has no blood supply. This discus is attached by thick tissue to the base of the ulnar styloid and by thinner tissue to the edge of the radius just proximal to the radiocarpal articular surface. Ulnocarpal ligaments The ulnocarpal ligaments (UCLs) consist of the ulnolunate and the ulnotriquetral ligaments. They originate from the ulnar styloid and insert into the carpal bones of the wrist: the ulnolunate ligament inserts into the lunate bone and the ulnotriquetral ligament into the triquetrum bone. These ligaments prevent dorsal migration of the distal ulna. They are more taut during supination, because in supination ulnar styloid moves away from the carpal bones volar side. ==Function==

The primary functions of the TFCC: • To cover the ulna head by extending the articular surface of the distal radius. • Load transmission across the ulnocarpal joint and partially load absorbing • Allows forearm rotation by giving a strong but flexible connection between the distal radius and ulna. It also supports the ulnar portion of the carpus. Load transmission The TFCC is important in load transmission across the ulnar aspect of the wrist. The TFC transmits and absorbs compressive forces. The ulnar variance influences the amount of load that is transmitted through the distal ulna. The load transmission is directly proportional to this ulnar variance. In neutral ulnar variance, approximately 20 percent of the load is transmitted. With negative ulnar variance, the load across the TFC is decreased. This occurs during supination, because the radius moves distally on the ulna and creates a negative ulnar variance. With positive ulnar variance it is reversed. The load that is transmitted across the TFC is then increased. This positive ulnar variance occurs during pronation. Rotation The TFCC is a major stabilizer of the DRUJ. To control the forearm rotation the DRUJ acts in concert with the proximal radioulnar joint. The connection between the distal radius and the distal ulna, maintain the congruency of the DRUJ. This attachment is mainly created by the RULs of the TFCC. These ligaments support the joint through its arc of rotation. The role of the TFCC in supination and in pronation is a matter of dispute. Some authors (Schuind et al.) concluded that the dorsal fibers of the TFCC tighten in pronation, and the palmar fibers in supination. These conclusions are opposite of those published by Af Ekenstam and Hagert. Both parties are in fact right, as the RULs consists of two ligaments each made of another two components: the superficial and the deep ligaments. During supination, the superficial palmar and the deep dorsal ligaments are tightened, preventing palmar translation of the ulna. In pronation, this is reversed: the superficial dorsal and the deep palmar ligaments are tightened and prevent dorsal translation of the ulna. ==Clinical significance==

The TFCC has a substantial risk for injury and degeneration because of its anatomic complexity and multiple functions. Application of an extension-pronation force to an axial-load wrist, such as in a fall on an outstretched hand, causes most of the traumatic injuries of the TFCC. Dorsal rotation injury, such as when a drill binds and rotates the wrist instead of the bit, can also cause traumatic injuries. Injury may also occur from a distraction force applied to the volar forearm or wrist. Finally, tears of the TFCC are frequently found by patients with distal radius fractures. Diagnosis ;Anamnesis Injuries to the TFCC may be preceded by a fall on a pronated outstretched arm; a rotational injury to the forearm; an axial load trauma to the wrist; or a distraction injury of the wrist in ulnar direction. • Ulnar grind test: The forearm is fixated and the wrist is held in dorsiflexion. The physician then applies axial load, while he rotates and deviates the wrist in ulnar direction. Pain and crepitations during this provocation maneuver suggest DRUJ instability or arthritis. Imaging • X-ray: X-rays of the wrist are made in two directions: posterior-anterior (PA) and lateral. Radiographs are useful to diagnose or rule out possible bone fractures, a positive ulnar variance or osteoarthritis. The TFCC is not visible on an X-ray, regardless of its condition. • MRI: is, together with the findings of a careful physical examination, a helpful diagnostic tool to assess the condition of the TFCC. Nevertheless, the incidence of false-positive and false-negative MRI results is high. Note: Imaging techniques can only be relevant together with the clinical findings of a carefully performed physical examination. Other than a TFCC injury, there are many possible causes for ulnar-sided wrist pain. Differential diagnosis of TFCC injuries :* Tendinopathy of the ECU :* Ulnar styloid fracture :* Distal radius fracture :* DRUJ arthritis :* Pisiform bone fractures :* Hamate bone fractures :* Carpal instability :* Midcarpal instability :* Hypothenar hammer syndrome (ulnar artery thrombosis) Treatment The initial treatment for both traumatic and degenerative TFCC lesions, with a stable DRUJ, is conservative (nonsurgical) therapy. Patients may be advised to wear a temporary splint or cast to immobilize the wrist and forearm for four to six weeks. The immobilization allows scar tissue to develop which can help heal the TFCC. In addition, oral NSAIDs and corticosteroid joint injections can be prescribed for pain relief. Physiotherapy and occupational therapy can help patients recover after immobilization or surgery. Wrist support straps used in sports can also be used in mild cases to compress and minimize movement of the area. Indications for acute TFCC surgery are: a clearly unstable DRUJ, or the existence of additional unstable or displaced fractures. TFCC surgery is also indicated when conservative treatment proves insufficient in about 8–12 weeks. Fractures of the radius bone are often associated by TFCC damage. If the fracture is treated surgically it is recommended to evaluate and if necessary repair the TFCC as well. Closed fractures (where the skin is still intact) of the radius bone are treated non-surgically with cast; the immobilization can also help heal the TFCC. Surgical ;Arthroscopic debridement of TFC discus tissue The central part of the TFC has no blood supply and therefore has no healing capacity. When a tear occurs in this area of the TFC, it typically creates an unstable flap of tissue that is likely to catch on other joint surfaces. Removing the damaged tissue (debridement) is then indicated. Arthroscopic debridement as a treatment for degenerative TFC tears associated with positive ulnar variance, unfortunately, show poor results. :* Shortening of the ulnar bone. Patients with a positive ulnar variance are more susceptible to TFCC damage. Shortening the ulnar bone may help relieve the excess pressure to the TFCC and prevent further degeneration. == References ==