Clinical History: A 35 year-old female presents with ulnar-sided wrist pain. (1a) A fat-suppressed T2-weighted 3D gradient-echo coronal image is provided. What are the findings? What is your diagnosis?
1a
Figure 1:
(1a) A fat-suppressed T2-weighted 3D gradient-echo coronal image
Findings
2a
Figure 2:
(2a) A small central perforation (arrow) is seen within the central portion of the articular disc of the triangular fibrocartilage complex. An additional, partial thickness undersurface tear (arrowhead) is also present at the articular disc.
Diagnosis
Complex tear of the articular disc of the triangular fibrocartilage complex (TFCC).
Discussion
The term “triangular fibrocartilage complex of the wrist” was first coined by Palmer and Werner in 1981,1 who described the cartilaginous and ligamentous structures that bridge the distal radius and ulna, providing articulation with the adjacent lunate and triquetrum.
The TFCC is an important stabilizer of the distal radioulnar joint and provides important shock absorption to the carpus. The components of the TFCC include:
- The articular disc
- The dorsal and volar radioulnar ligaments
- The meniscus homologue
- The extensor carpi ulnaris tendon sheath
- The ulnocarpal ligaments
Although all of the components of the TFCC are structurally important, from a radiologic and an orthopaedic perspective, it is the articular disc and the radioulnar ligaments that are the most important to evaluate. The articular disc, or the triangular fibrocartilage proper (TFC) is appropriately named, as it has a characteristic triangular shape (3a, 4a). The articular disc may be only 1-2 millimeters thick within its central portion, but the TFC thickens considerably at its dorsal and volar aspects, as well as at the ulnar attachments. The thickened dorsal and volar components are what comprise the dorsal and volar radioulnar ligaments. A healthy articular disc is relatively firm and unyielding at arthroscopy, having a somewhat trampoline-like feel upon arthroscopic probing. The articular disc attaches broadly at its radial side, and tapers to its ulnar attachment, where separate foveal and styloid attachments can be seen both arthroscopically and with MR imaging.
3a
Figure 3:
(3a) A 3D depiction of the TFC (arrow) demonstrates its triangular shape and relatively thin central region.
4a
Figure 4:
(4a) Viewed from above, the thickened peripheral components that represent the dorsal and volar radioulnar ligaments (arrows) are readily apparent.
On MR images, the TFC demonstrates low signal intensity with all imaging sequences. However, it is normal for the TFC to demonstrate areas of increased signal intensity near its ulnar insertion because of the presence of loose connective tissue (5a).2 In addition, the interface with normal articular cartilage creates a linear region of intermediate signal intensity at the radial insertion. This appearance should not be mistaken for a tear.
5a
Figure 5:
(5a) A T1-weighted coronal image demonstrates a normal TFC. Normal intermediate signal intensity is evident at the ulnar attachment (arrow). The normal interface with articular cartilage at the radial side is also apparent (arrowhead), and should not be mistaken for a vertical tear.
Injuries to the TFCC may be traumatic or degenerative in nature. The most common abnormality is a central perforation, typically degenerative in origin. This abnormality is often present as an asymptomatic finding in middle-aged or older individuals.3 Such tears usually involve the central TFC near the radial attachment (6a). Because of the frequency of degenerative central perforations, which are virtually ubiquitous in elderly patients, the importance of such findings on MR is dependent upon careful clinical correlation.
6a
Figure 6:
(6a) A typical degenerative central tear (arrow) is noted on this fat-suppressed proton density weighted coronal image of the wrist.
In (1a), the original image from today’s discussion, both a degenerative central tear and an undersurface partial tear are apparent. Interestingly, studies have shown that in many patients, partial undersurface tears are more likely to be symptomatic than complete central perforations.4 This distinction is important, as central perforations are seen with high sensitivity via arthrography, but MRI is better able to both identify and characterize the partial TFC tears that are more likely to be symptomatic.
In evaluating TFCC tears using MRI, another very important distinction to make is whether the dorsal or volar radioulnar ligaments are involved with the tear. Indeed, in many cases the central articular disc of the TFCC may appear normal, and the casual MR reader may then move on to evaluate other areas of the wrist. One must carefully follow coronal and sagittal images to their periphery in order to identify the clinically important tears of the dorsal or volar radioulnar ligaments (7a,7b). Such tears are more likely to result in distal radioulnar joint instability than central tears, and because the periphery of the TFCC remains vascularized in adults, these tears are frequently amenable to arthroscopic repair.
7a
7b
Figure 7:
(7a) A T1-weighted coronal image through the central disc of the TFCC (arrow) is relatively unremarkable. (7b) A 3D gradient echo coronal image, however, reveals a discrete vertical tear (arrow) involving the thicker, volar radioulnar ligament component of the TFCC.
The ulnar attachments of the TFCC are also relatively vascular and thus amenable to surgical repair, particularly when the tears are traumatic in nature. In such cases, MR provides a valuable pre-operative roadmap (8a), not only identifying the sites of tearing but also providing evaluation for possible coexisting abnormalities such as chondral lesions or positive ulnar variance (9a). The latter abnormality is a risk factor for degenerative or traumatic TFCC tears, and if surgical repair of a TFCC abnormality is contemplated in the setting of positive ulnar variance, an ulnar shortening procedure is often indicated at the time of repair.5
8a
Figure 8:
(8a) Following trauma, a T2*-weighted gradient echo coronal image reveals avulsion of the ulnar styloid attachment of the TFC (arrow). The foveal attachment (arrowhead) remains intact.
9a
Figure 9:
(9a) A T1-weighted coronal image from a 14 year-old with severe positive ulnar variance reveals a large central tear (arrow) along the radial aspect of the articular disc of the TFCC. Associated subchondral degenerative changes are evident within the proximal lunate (arrowhead).
Conclusion
Injuries to the TFCC are a frequent cause of ulnar sided wrist pain. MRI allows accurate pre-treatment evaluation of patients with suspected TFCC pathology, and with proper technique and interpretation, provides excellent characterization of TFCC tears and their associated wrist pathology. Because the operative and non-operative approaches to TFCC pathology vary widely depending upon the tear type and location, such information is invaluable for the proper management of patients with TFCC tears.
References
1 Palmer AK, Werner FW: The triangular fibrocartilage complex of the wrist–anatomy and function. J Hand Surg [Am] 1981 Mar; 6(2): 153-62.
2 Sugimoto H, Shinozaki T, Ohsawa T. Triangular fibrocartilage in asymptomatic subjects: investigation of abnormal MR signal intensity. Radiology 1994; 191:193-197
3 Yin YM, Evanoff B, Gilula LA, Pilgram TK. Evaluation of selective wrist arthrography of contralateral asymptomatic wrists for symmetric ligamentous defects. AJR Am J Roentgenol 1996; 166:1067-1073.
4 Zanetti M, Linkous DL, Gilula LA, Hodler J. Characteristics of triangular fibrocartilage defects in symptomatic and contralateral asymptomatic wrists. Radiology 2000; 216:840-845.
5 Trumble TE, Gilbert M, Vedder H. Ulnar shortening combined with arthroscopic repairs in the delayed management of triangular fibrocartilage complex tears. Journal of Hand Surgery 1997; 22(5):807-13.