Anatomy

The TFCC is a cartilaginous and ligamentous structure interposed between the ulnar carpus and the distal ulna (Fig. 26-1). It arises from the distal aspect of the sigmoid notch of the radius and inserts into the base of the ulnar styloid. The TFCC attaches to the ulnar carpus via the ulnocarpal ligament complex (ulnolunate, ulnotriquetral, and ulnar collateral ligaments).^1–3 The radioulnar ligaments stabilize the DRUJ, limiting rotational as well as axial migration.⁴ The dorsal and volar radioulnar ligaments (Fig. 26-2) are fibrous thickenings within the substance of the TFCC. As a result of this anatomical configuration, they function as a unit rather than as independent ligaments. The central, horizontal portion of the TFCC is the thinnest portion, composed of interwoven obliquely oriented sheets of collagen fibers⁵ for the resistance of multidirectional stress.

FIGURE 26-1 Anatomical coronal section demonstrating the TFCC and relation to the lunate (L), triquetrum (T), scaphoid (S), and distal ulna and radius.

(From Palmer AK, Werner FW: The triangular fibrocartilage complex of the wrist—anatomy and function. J Hand Surg. 1981; 6A:154.)

FIGURE 26-2 Dorsally disarticulated wrist demonstrating the TFCC and its volar ulnocarpal ligaments: ulnolunate ligament (ull), ulnotriquetral ligament (utl), and the dorsal radioulnar ligament (four circles). T, triquetrum; L, lunate; S, scaphoid.

(From Palmer AK: Triangular fibrocartilage complex lesions: a classification. J Hand Surg. 1989; 14A:595.)

The vascularity of the TFCC has been carefully studied.^5–7 The TFCC receives its blood supply from the ulnar artery through its radiocarpal branches and the dorsal and palmar branches of the anterior interosseous artery (Fig. 26-3). These vessels supply the TFCC in a radial fashion. Histologic sections demonstrate that these vessels penetrate only the peripheral 10% to 40% of the TFCC. The central section and radial attachment is avascular (Fig. 26-4). This vascular anatomy supports the concept that peripheral injuries possess the ability to heal if injured and treated appropriately, whereas the tears of the central portion do not heal if sutured and are usually débrided.

FIGURE 26-3 Arterial anatomy of the TFCC.

(Adapted from Thiru-Pathi RG, Ferlic DC, Clayton ML, et al: Arterial anatomy of the triangular fibrocartilage of the wrist and its surgical significance. J Hand Surg. 1986; 11A:261.)

FIGURE 26-4 Axial view of the TFCC demonstrating the vascular supply to the periphery and avascular radial attachment (arrows).

(From Bednar MS, Arnoczky SP, Weiland AJ: The microvasculature of the triangular fibrocartilage complex: its clinical significance. J Hand Surg. 1991; 16A:1103.)

Biomechanics

The TFCC has several important biomechanical functions. It transmits 20% of an axially applied load from the ulnar carpus to the distal ulna, it is the major stabilizer of the DRUJ, and it is a stabilizer of the ulnar carpus.^3,8–12

The amount of the load transferred to the distal ulna varies with ulnar variance. A greater amount is transferred in ulnar-positive variance than ulnar-negative variance. This results in a corresponding decreased thickness of the central portion of the TFCC in ulnar-positive wrists.¹⁰ In addition, there is a variable load placed on the TFCC with forearm rotation. Supination causes ulnar-negative variance owing to the proximal migration of the ulna. This is reversed with pronation as the ulna moves distally, causing it to become ulnar positive.¹³ The ulnar head also moves within the sigmoid notch in a dorsal direction with pronation and volar with supination.⁸ The dorsal and volar radioulnar ligaments that form the peripheral portion of the TFCC become tight with forearm rotation, serving as major stabilizers of the DRUJ, which control this translation during rotation.⁹

Mechanism of Injury

Traumatic injuries of the TFCC result from the application of an extension/pronation force to the axially loaded wrist or by a distraction force to the ulnar aspect of the wrist.^1,14 This will most commonly occur with a fall on the outstretched hand. The lesions are more common with ulnar-positive and ulnar-neutral patients and are commonly found in those patients being treated for fractures of the distal radius.

Several authors have examined the incidence of intracarpal soft tissue injuries associated with distal radial fractures. Geissler and coworkers¹⁵ studied 60 patients, finding a TFCC injury in 26 (43%). In Lindau and colleagues’ series of 51 patients,¹⁶ a TFCC injury was found in 43 (84%): 24 had a peripheral tear, 10 had a central perforation, and 9 had a combined central and peripheral tear. Richards and associates in their series of 118 patients¹⁷ reported a TFCC injury in 35% of the patients with intra-articular fractures and 53% of those with extra-articular fractures.

Classification

The classification system described by Palmer¹ is the most useful for describing TFCC injuries that are both traumatic and degenerative. Only traumatic lesions are discussed here.

Traumatic lesions are classified according to the location of the tear within the TFCC. The traumatic class has been designated by Palmer as class 1 with subclasses of A, B, C, and D assigned to anatomical lesions within the TFCC.

A class 1A lesion represents a tear in the horizontal or central portion of the TFCC (Fig. 26-5A). The tear is 2 to 3 mm medial to the radial attachment of the cartilage. It is usually oriented from dorsal to volar.

FIGURE 26-5 A, Palmer classification for acute TFCC injuries. Class 1A lesion involves a tear in the central, horizontal portion of the TFCC. B, Class 1B lesion is a tear of the TFCC from the distal ulna with or without an ulnar styloid fracture. C, Class 1C lesion is a tear of the TFCC distal attachment to the lunate and triquetrum through the ulnolunate and ulnotriquetral ligaments. D, Class 1D lesion is a detachment of the TFCC from its insertion onto the radius at the distal sigmoid notch.

(Adapted from Palmer AK: Triangular fibrocartilage complex lesions: a classification. J Hand Surg. 1989; 14A:601.)

A class 1B lesion (see Fig. 26-5B) is an avulsion of the peripheral aspect of the TFCC from its insertion onto the distal ulna. This can occur either with a fracture of the ulnar styloid or as a pure avulsion from its bony attachment. This type of injury disrupts the stabilizing effect of the TFCC on the DRUJ, resulting in clinical instability.

A class 1C lesion (see Fig. 26-5C) is an avulsion of the TFCC attachment to the ulnar carpus by disruption of the ulnocarpal ligaments. This lesion will result in ulnar carpal instability with volar translocation of the carpus.

A class 1D lesion (see Fig. 26-5D) is an avulsion of the TFCC from its radial attachment. Involvement of the dorsal and or volar radioulnar ligaments will result in instability of the DRUJ.

Diagnosis

Clinical symptoms consist of ulnar-sided wrist pain frequently with clicking and typically occur after a fall. The initial physical examination reveals swelling over the ulnar aspect of the wrist with inflammation of the tendon of the extensor carpi ulnaris. Point tenderness is present over the TFCC and distal ulna. Ulnar deviation and axial loading of the wrist (TFCC compression test) (Fig. 26-6) will elicit a painful response. A click is frequently present with forearm rotation. The DRUJ must be assessed for instability. Instability is best assessed with the forearm in neutral rotation, but it is also checked in full supination and full pronation. The examiner stabilizes the distal radius with one hand and applies a force to the distal ulna, moving it dorsal and volar in a search for increased motion or subluxation of the distal ulna relative to the radius compared with the opposite uninjured wrist. Significant instability would present as laxity of the distal ulna with a positive “piano key“ sign and dorsal prominence of the distal ulna. This would represent a significant tear or detachment of the dorsal or volar radioulnar ligaments.

FIGURE 26-6 TFCC compression test: ulnar deviation and axial load applied to wrist produces a painful response.

TFCC injuries do not occur in isolation but are a component of a spectrum of injury to the ulnar side of the wrist.¹⁸ The examiner must therefore evaluate all of the commonly injured structures on the ulnar side of the wrist. The lunatotriquetral joint must be assessed for instability due to a lunatotriquetral ligament tear. This would cause tenderness over the lunatotriquetral interval with a positive shuck test. The dorsal radial carpal ligament complex should be examined to determine if traumatic midcarpal instability is present.

The differential diagnosis for ulnar-sided wrist pain consistent with a TFCC tear would include extensor carpi ulnaris subluxation, lunatotriquetral ligament injury, triquetral avulsion fracture, pisotriquetral arthritis, ulnar artery thrombosis, neuritis of the dorsal ulnar sensory nerve, and ulnar neuropathy at Guyon’s canal. It is a common finding that one or more of these diagnoses are present in addition to the TFCC injury.

Imaging

The diagnostic workup should include plain radiography to include a neutral rotation posteroanterior and a lateral view. This will allow assessment for fracture, ligament instability resulting in carpal malalignment, as well as determination of ulnar variance. The determination of ulnar variance is important in that it will influence treatment options. The DRUJ must also be examined radiographically to determine if subluxation, arthritis, or ulnar styloid abnormalities such as an acute or chronic nonunited fracture fragment are present.

Magnetic resonance imaging (MRI) is useful in the diagnosis of TFCC tears, especially the class 1A and D lesions.^19,20 T2-weighted MR images in the coronal plane are of the greatest diagnostic value (Fig. 26-7). The TFCC has a homogeneous low signal intensity. The synovial fluid of the joint appears as a bright image on T2-weighted images and will outline tears in the TFCC. The addition of a gadolinium arthrogram enhances the visualization of TFCC tears.

FIGURE 26-7 Coronal T2-weighted MR image of the wrist. High signal of the joint fluid outlines the low signal substance of the TFCC. Tears will show as high signal intensity within the TFCC periphery or central region.

The series in the literature reviewing the sensitivity and specificity of MRI in diagnosing injuries of the TFCC show significant variation in the reported results. Golimbu and coworkers¹⁹

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