What is the triangular fibrocartilage complex (TFCC) of the wrist joint? There have been many descriptions of the TFCC to date. It includes the articular disc, the meniscal homologue, the palmar and dorsal ulnar radial ligaments, the inferior ulnar extensor carpi radialis tendon sheath, the ulnar capsule, and the ulnar lunar and ulnar deltoid ligaments. The palmar and dorsal ulnar radial ligaments consist of superficial and deep fibers that converge at the radial attachment. The superficial portion wraps around the articular disc and ends at the ulnar styloid process, but does not have a well-defined end point. The palmar and dorsal fibers of the deeper layer converge and interlock near the proximal stop to form a joint tendon that ends at the basal recess of the ulnar styloid process, which is also the ulnar attachment point of the ulnar head ligament. The deep fibers play a greater role in maintaining the rotational stability of the distal ulnar radial joint than the superficial fibers, and if broken can lead to instability of the distal ulnar radial joint. Even if the ligamentous attachment structure of the ulnar head recess is intact, patients can still experience a peripheral tear of the TFCC, but these patients do not necessarily have the kind of instability caused by a complete tear of the ulnar ligamentous attachment. This instability can be seen in patients with avulsion fractures of the entire ulnar styloid process. Mechanism and Classification of Injury TFCC injuries can occur during a fall with the hand propped on the ground, when the wrist is subjected to axial stress in the extended, rotated anterior position. Other mechanisms of injury include injury from greater rotational or distraction violence. lindau and colleagues found that 39 of 51 patients with displaced distal radius fractures had a combined TFCC tear and that distal ulnar radial instability was common at 1-year post-injury follow-up. palmer classified traumatic TFCC injuries into 4 types. type IA injuries are isolated tears of the central portion of the articular disc. Type IB is a peripheral tear of the TFCC that may be combined with distal ulnar radial instability. type IC is a partial tear of the palmar ulnar carpal extrinsic ligament of the TFCC that may result in a posterior rotation deformity of the carpal bone relative to the ulna. type ID is an avulsion of the TFCC from its sigmoid notch attachment to the radius and is commonly seen in patients with distal radius fractures. Diagnosis and nonoperative treatment Patients usually present with pain and popping on the ulnar side of the wrist, which are exacerbated by carpal ulnar deviation and forceful rotation of the forearm. tay and colleagues found that pressure pain in the ulnar head recess was 95% and 86% sensitive and specific for the diagnosis of ulnar head recess discontinuity and/or ulnar deltoid ligament tear, respectively. the TFCC compression test (TFCC compression test) may Positive, i.e., pain with axial stress applied during wrist ulnar deviation. The stability of the distal ulnar radial joint should be checked in the anterior and posterior forearm rotation positions, and the piano key sign of the ulnar head should be checked for positivity. If combined with a lunotriquetral ligament tear, the injury may be associated with localized tenderness and a positive LT shear test. A subluxation of the ulnar extensor carpi radialis must be excluded. Most acute tears heal or resolve with 4-6 weeks of rest. The use of hormonal injections in the subacute phase also has a role. Anteroposterior and lateral radiographs should be taken in all patients, along with a rotational anterior grip position to determine ulnar varus. For many years, double- or triple-row arthrography has been the standard of care, especially with digital subtraction techniques. MRI arthrography does not significantly increase the diagnostic yield of central TFCC injuries, with reported sensitivities and specificities of 74% and 80%, respectively. CT arthrography is highly sensitive for diagnosing central tears, but is not accurate for diagnosing peripheral tears. Arthroscopy remains the gold standard for the diagnosis and treatment of TFCC tears. Surgical indications for TFCC injuries Unless combined with distal ulnar radial instability, TFCC injuries that have failed to respond to conservative treatment for 3 months are indicated for arthroscopic surgery. Arthroscopically repairable peripheral TFCC tears include IB and IC injuries. In symptomatic radial TFCC tears, they can be treated with simple debridement if the distal ulnar radial joint is stable, whereas repair is required if combined with distal ulnar radial instability.