The triangular fibrocartilage complex (TFCC) is, as the name implies, a complex, three-dimensional confluence of multiple ligamentous structures, a fibrocartilaginous disk, and several bony insertion sites located at the ulnar side of the carpus. Derangement of this complex may result in significant ulnar-sided wrist pain and dysfunction, distal radioulnar joint (DRUJ) instability, and impedance of activities of daily living and performance of sporting activities, both competitive and recreational.
Ulnar-sided wrist pain is the most common presenting symptom in patients with a TFCC injury. The differential diagnosis of ulnar-sided wrist pain is extensive, however. Common ulnar-sided pathology (often occurring with concomitant TFCC injury) that must be considered includes fractures of the ulnar styloid, pisiform, triquetrum, hamate, and sigmoid notch of the distal radius; other ligamentous injuries, such as injury of the lunotriquetral ligament; tendinopathy or instability of the extensor carpi ulnaris (ECU); tendinopathy of the flexor carpi ulnaris; joint arthritides, either inflammatory (e.g., rheumatoid arthritis and crystalline arthropathy) or noninflammatory (e.g., osteoarthritis of the DRUJ or pisotriquetral joint); peripheral compression neuropathy, such as the ulnar nerve at Guyon’s canal; vasoocclusive disease, such as hypothenar hammer syndrome; idiopathic osteonecrosis, such as Kienböck disease involving the lunate; and osseous tumors (e.g., a giant cell tumor or osteoid osteoma) or soft tissue tumors (e.g., a ganglion cyst or lipoma).
Such a vast differential diagnosis requires a good understanding of the ulnar wrist anatomy combined with a thorough history, a focused physical examination, and appropriate imaging to reach a working diagnosis of TFCC pathology and render appropriate treatment.
Components of the TFCC
The TFCC consists of the central articular disk, dorsal and volar radioulnar ligaments, ulnolunate ligament, ulnotriquetral ligament, meniscal homologue, and the subsheath of the ECU tendon ( Fig. 76-1 ). The primary purpose of this intricate soft tissue complex is to confer stability between the ulna and radius at the DRUJ. Because the radius of curvature of the sigmoid notch of the radius is larger than the radius of curvature of the distal ulnar head, the osseous articulation provides only approximately 20% of the total stability of the joint. In this regard, soft tissue stability is paramount at the DRUJ.
The main static soft tissue stabilizers of the DRUJ are the dorsal and volar radioulnar ligaments. These ligaments form the dorsal and volar margins of the TFCC and insert into the fovea of the ulnar head at the base of the ulnar styloid; the deeper fibers are known classically as the ligamentum subcruentum ( Fig. 76-2 ). The dorsal and volar radioulnar ligaments originate from the dorsal and volar ulnar corners of the distal radius. When viewed from a distal perspective, the arrangement of these ligaments is triangular, hence the nomenclature of the TFCC. It is thought that the dorsal radioulnar ligament may become taut in pronation, whereas the volar radioulnar ligament may become taut in supination ; however, this supposition continues to be a contentious issue in the literature. Nonetheless, it is agreed that the tension inherent in these ligaments varies with forearm position.
The central articular disk, which consists mainly of fibrocartilage, is bounded by the dorsal and volar radioulnar ligaments and the most ulnar aspect of the distal radius. It serves as a cushion between the distal end of the ulna and the proximal carpal row but does not itself confer considerable stability to the DRUJ. Consequently, many central disk tears may be simply debrided or left untreated without resulting clinical DRUJ instability.
The ulnolunate and ulnotriquetral ligaments are extrinsic structures that represent thickenings of the volar capsule. Although the name implies that the ligaments arise from the ulna and attach to the lunate and triquetrum, respectively, histologic studies have shown otherwise. These ligaments emanate from the volar portion of the volar radioulnar ligament and the central articular disk, not directly from the ulna. These ligaments add to the dorsal stability of the DRUJ and prevent excessive dorsal translation of the distal ulna relative to the carpus.
The meniscal homologue refers to a broad expansion of tissue traversing in a radioulnar direction from the central articular disk to the ulnar styloid and the surrounding joint capsule. This expansion of tissue is composed of loose connective tissue and is itself not a major contributor to structural integrity of the TFCC. A nearby opening in the meniscal homologue is known as the prestyloid recess, which may be confused with a peripheral tear by novice wrist arthroscopists. It is not uncommon to see synovitis in the region of the prestyloid recess, which makes this distinction difficult at times.
Open approaches to the TFCC are often made via the sixth dorsal compartment, which contains the ECU tendon. The floor of this compartment is the ECU subsheath, which provides a landmark and window into the deeper TFCC structures. The ECU subsheath is intimately involved and continuous with the dorsal radioulnar ligament and meniscal homologue. Nonanatomic repairs of the TFCC are often repaired to this stout investing tissue; details are provided later in this chapter.
The blood supply to the TFCC originates from the terminal extents of the anterior and posterior interosseous arteries. The TFCC has similarities with the meniscus of the knee in this regard. The perfusion of the volar, ulnar, and dorsal portions of the TFCC, which is derived from their capsular attachments, is excellent, but the central and radial portions of the articular disk have relatively poor vascularity. Thus, similar to the knee, peripheral injuries have greater healing potential with surgical repair. Conversely, the central articular disk and its radial attachment lack robust healing potential.
Classification of Injury
A relatively straightforward classification system was described by Palmer based on the anatomy and etiology of the TFCC tear ( Table 76-1 ). Tears are divided into traumatic class 1 and degenerative class 2 injuries. However, not all TFCC tears fall neatly into these categories. For instance, a tear that appears to be degenerative may follow a traumatic event, resulting in an injury that does not perfectly match the classification scheme. These tears are considered “complex.”
|IA||Central perforation of articular disk|
|IB||Foveal insertional tear, with or without ulnar styloid fracture|
|IC||Tear of ulnocarpal ligaments (ulnolunate and ulnotriquetral)|
|ID||Radial-sided insertional tear|
|IIA||Central wear of TFCC|
|IIB||Wear with chondromalacia of the lunate or ulnar head|
|IIC||TFCC perforation with chondromalacia|
|IID||TFCC perforation with chondromalacia and wear or tear of the LT ligament|
|IIE||TFCC perforation with chondromalacia and wear or tear of the LT ligament, with ulnocarpal arthritis|
Class 1 Tears (Traumatic)
Class 1 tears are traumatic in nature and are subdivided into four groups (A through D). Class 1A lesions are most common and involve a traumatic perforation of the central articular disk. These lesions are often located near the radial insertion of the articular disk but do not involve the dorsal or volar radioulnar ligaments. Clinical DRUJ instability is unlikely. Class 1B lesions involve the ulnar insertion of the TFCC into the fovea of the distal ulna. The ulnar styloid may be fractured with this category of injury as well. DRUJ instability is more likely but variable. Class 1C injuries involve either the ulnolunate or ulnotriquetral ligaments, with potential ulnocarpal instability. Finally, class 1D injuries involve radial-sided avulsions of the TFCC from the distal radius. The origin of the dorsal and volar radioulnar ligaments, as well as the central articular disk, are detached. All of these injuries may or may not accompany certain distal radius fracture patterns.
Class 2 Tears (Degenerative)
Class 2 tears are degenerative in nature and are further subclassified into five groups (A through E), generally implying increasing progression of the degenerative pathology. Class 2A tears show wear or thinning of the central portion of the TFCC articular disk without frank perforation. Beyond central disk wear, Class 2B tears reveal early chondromalacia of the ulnocarpal joint. Class 2C tears are distinguished by complete central disk perforation and accompanying chondromalacia. Class 2D injuries show all the signs of class 2C injuries, with additional partial or complete involvement of the lunotriquetral (LT) ligament. Finally, class 2E tears show global ligament disruption and degenerative joint disease.
Any significant compressive or twisting injury at the wrist may produce a TFCC injury. When ulnar neutral variance is present, the ulnocarpal joint bears approximately 20% of axial load. A greater percentage of force is transmitted to the TFCC with increasing ulnar positivity. Forceful gripping and maximal forearm pronation effectively increase ulnar positivity, and therefore additional axial load in such circumstances may predispose a person to a TFCC injury. Ulnar-sided wrist pain is the chief complaint after TFCC injury. Some patients report a specific traumatic injury, whereas others describe pain that is more insidious in onset. Patients typically localize the pain to the ulnar side of the wrist, which is often worsened by pronation, supination, or wrist circumduction. A clicking or popping may be reproduced with these actions. Additionally, the pain may escalate with either gripping activities or when the wrist is held in maximal extension, ulnar deviation, and relative pronation. In patients without an acute injury, a history of repetitive motion may be elicited. Sports and/or activities that involve repetitive provocative positions, such as swinging a baseball bat, tennis racquet, or golf club, may produce degenerative lesions of the TFCC, especially in the setting of chronic ulnar positive variance. Chronic ulnar positive variance may stem from congenital wrist differences, previous wrist trauma (e.g., a malunited distal radius fracture), or an idiopathic etiology. A final possibility is an acute-on-chronic presentation. In the setting of a degenerative TFCC lesion, patients may be asymptomatic, minimally symptomatic, or even tolerant of chronic symptoms. A new traumatic incident may exacerbate the pain or lead to additional clicking, popping, or subjective wrist instability that prompts evaluation.
As with any injury process, a well-performed history includes the duration and intensity of symptoms, alleviating factors, prior treatment, vocational and avocational activities, and comorbidities that may have implications for determining the diagnosis and developing a treatment plan.
As stated previously, ulnar-sided wrist pain has multiple etiologies. The history will often narrow the differential diagnosis, but the physical examination must correlate with the practitioner’s suspicions. Examination begins with inspection for the presence and location of skin disruption, edema, and ecchymosis. Significant bruising and swelling are typically uncommon with TFCC injury unless accompanied by fracture. Range of motion is evaluated in all planes and compared with the contralateral uninjured limb. The TFCC is best palpated in the soft spot between the ECU and flexor carpi ulnaris tendons or between the ulnar styloid and the pisiform. This test of “foveal” tenderness has been shown to have an approximate sensitivity of 95% and specificity of 87%.
Certain provocative tests can be used to help distinguish TFCC injury from other causes of ulnar-sided wrist pain. The ulnocarpal stress test involves a combination of axial loading and ulnar deviation, with subsequent pronation and supination. A positive test will reproduce the patient’s pain. This test is quite sensitive but not very specific, because it may be positive in patients with LT injuries, ulnocarpal impingement, and arthritis. Alternatively, we have consistently used the “lift-off test” for suspected TFCC injury. In this test, the patient is asked to place both hands under an examination table and then lift the table with the forearms parallel to the table surface. This maneuver typically results in forceful wrist extension and hypersupination, reproducing the patient’s pain. This mechanism has been specifically observed in professional hockey players, particularly goalies, who report pain when shuffling pucks forward from their gloved hand.
The DRUJ should be thoroughly examined and compared with the uninjured side in a patient with a suspected TFCC injury. This examination is performed with the wrist in a neutral position and in pronation and supination. It is important to appreciate that the ulna is the fixed, stable unit of the forearm axis. The distal ulna and distal radius are each grasped separately by the examiner and translated in opposite directions in an attempt to subluxate or dislocate the radius from the ulna. Although some translational displacement (<50%) may be normal, determining side-to-side differences is paramount and must be documented accordingly. Significant variation in radius translation may be seen depending on whether the patient makes a fist to activate dynamic muscle stabilizers across the wrist. Significant DRUJ instability suggests a massive TFCC disruption. Admittedly, this aspect of wrist examinations is one of the most challenging for the novice and expert alike.
Standard posteroanterior, oblique, and lateral radiographs should be obtained for evaluation of an ulnar-sided wrist injury in all patients. Fractures of the ulnar styloid or subtle DRUJ malalignment suggest TFCC injury. Wrist position is key to proper interpretation. The forearm must be in neutral rotation to ensure proper radioulnar alignment and to determine ulnar variance ( Fig. 76-3 ). Radiographs taken with an overpronated forearm will misjudge the degree of ulnar positivity. Conversely, radiographs obtained with an oversupinated forearm may underestimate the ulnar variance. In cases of suspected ulnar impaction syndrome, a special pronated grip view may be helpful.
Other etiologies of symptoms may be apparent from a radiographic review. Ulnar styloid fractures are often seen in conjunction with distal radius fractures. Other injuries such as triquetrum, hamate hook, and pisiform fractures also may present with ulnar-sided wrist pain. Dorsal triquetral avulsion fractures are often visible on lateral wrist radiographs. A pisotriquetral view, taken with the wrist supinated 30 degrees from neutral, is often helpful to evaluate fractures or arthritis affecting this articulation.
Computed tomography (CT) is a powerful tool for DRUJ assessment but has a limited role for evaluating the details of TFCC pathology. The bony morphology and alignment of the DRUJ may be characterized in detail. When they are used for evaluating acute or chronic DRUJ instability, CT scans of the wrist in varying positions of pronosupination and additional testing of the contralateral wrist provide valuable image data for scrutiny of subtle abnormalities otherwise difficult to detect by physical examination or a plain radiograph alone.
Isolated wrist arthrography is rarely performed with the advent of magnetic resonance imaging (MRI). Arthrography is most useful in diagnosing scapholunate and central TFCC perforations (class 1A and 2C injuries) and is less sensitive for LT and peripheral TFCC tears. It has never been shown to be as sensitive as wrist arthroscopy, which is considered to be the gold standard. CT arthrography is occasionally used in patients with a suspected TFCC injury who have a contraindication to other forms of advanced imaging.
Magnetic Resonance Imaging
MRI serves an important adjunctive role in diagnosing TFCC injury ( Fig. 76-4 ). Its value is in revealing pathologic edema, joint effusion, and soft tissue disruption, which cannot be easily manifested by any other imaging technique. Because of the high sensitivity of MRI for detecting soft tissue and osseous abnormalities, caution must be observed when interpreting the findings. A recent study has shown that TFCC abnormalities detected by MRI increase with age and are quite common in asymptomatic wrists. The importance of clinical correlation, especially with regard to injury chronicity and localization of symptoms, cannot be overstated. For optimal imaging quality, the MRI must be performed with a dedicated wrist coil. Open MRI and evaluations performed with alternative coils produce poor quality images that obfuscate their overall value. A 3.0-tesla magnet may have higher diagnostic accuracy than a 1.5-tesla magnet, but its availability is not essential for evaluation of TFCC injuries. A 1.5-tesla magnet with a dedicated wrist coil will produce images of sufficient quality in the majority of cases.