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Original Research |
1 Department of Radiology, Balgrist University Hospital, Forchstrasse 340,
CH-8008 Zurich, Switzerland.
2 Department of Orthopedic Surgery, Balgrist University Hospital, CH-8008
Zurich, Switzerland.
3 Mallinckrodt Institute of Radiology, Washington University Medical Center,
Barnes Jewish Hospital, St. Louis, MO 63110.
Received November 24, 2005;
accepted after revision February 1, 2006.
Address correspondence to M. Zanetti
(marco.zanetti{at}balgrist.ch).
Abstract
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MATERIALS AND METHODS. Forty-one patients (18 women, 23 men; mean age, 38 years; age range, 18-60 years) underwent MR arthrography and wrist arthroscopy. For MR arthrography, iopamidol (300 mg I/mL) and gadopentetate dimeglumine (4 mmol/L) were injected into the distal radioulnar joint. Consensus review of both MR arthrograms and conventional arthrograms was performed by two experienced musculoskeletal radiologists. Presence or absence of communicating and noncommunicating tears of the ulnar attachment of the triangular fibrocartilage was recorded. Arthroscopy was used as the standard of reference for determining sensitivity, specificity, and accuracy in detection of tears of the ulnar attachment.
RESULTS. At MR arthrography, communicating tear of the ulnar attachment was diagnosed in three patients, noncommunicating tear in 19 patients, and normal attachment in 19 patients. Arthroscopy revealed peripheral tear of the triangular fibrocartilage in all three patients with communicating tear, in 14 of 19 patients with noncommunicating tear, and in three of 19 patients with normal attachment. The sensitivity was 85% (17/20), specificity was 76% (16/21), and accuracy was 80% (33/41).
CONCLUSION. MR arthrography of the distal radioulnar joint is accurate in depiction of peripheral tears of the ulnar attachment of the triangular fibrocartilage. These tears often appear as noncommunicating tears extending from the distal radioulnar joint into the triangular fibrocartilage.
Keywords: extremities • MRI • musculoskeletal imaging • orthopedic surgery • wrist
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Injection Technique
All patients underwent routine MR arthrography, which consisted of
injection of 0.5 mL of iodinated contrast medium (300 mg I/mL iopamidol,
Iopamiro 300, Bracco) and 0.5 mL of MR contrast material (4 mmol/L
gadopentetate dimeglumine, Magnevist, Schering) into the DRUJ. Higher volumes
(up to a total of 4 mL) were used when contrast material entered the
radiocarpal joint from the DRUJ. A second contrast injection into the
midcarpal joint was performed immediately when contrast material did not enter
the radiocarpal joint. This approach of double injection into the DRUJ and
midcarpal joint is the routine MR arthrographic protocol at our institution
for all patients with suspected triangular fibrocartilage lesions or
intercarpal ligament lesions. All injections were performed under fluoroscopic
guidance with a 24-gauge needle. Serial fluoroscopic spot radiographs were
obtained to document placement of contrast material for MR arthrography and
served as the conventional wrist arthrogram. The wrist was not exercised after
the injections.
MRI
MR arthrography was performed after contrast injection. A 1.5-T MR system
(Symphony, Siemens Medical Solutions) with a dedicated quadrature wrist coil
was used. The following MR sequences were used: coronal T1-weighted
fat-suppressed spin-echo (TR/TE, 525/15; section thickness, 3 mm; intersection
gap, 0.3 mm; field of view, 81 x 100 mm; matrix size, 416 x 512;
number of excitations [NEX], 2); coronal proton density-weighted
fat-suppressed turbo spin-echo (2,430/34; section thickness, 3 mm;
intersection gap, 0.3 mm; field of view, 100 x 100 mm; matrix size, 512
x 512; turbo factor, 7; NEX, 3); sagittal T1-weighted spin-echo (475/20;
section thickness, 3 mm; intersection gap, 0.6 mm; field of view, 81 x
100 mm; matrix size, 416 x 512; NEX, 2); and axial proton
density-weighted turbo spin-echo (3,120/30; section thickness, 2.2 mm;
intersection gap, 0.6 mm; field of view, 100 x 109 mm; matrix size, 512
x 464; turbo factor, 7; NEX, 2).
Image Analysis
A consensus review of both MR arthrograms and conventional arthrograms was
performed by two radiologists with 12 and 32 years of experience in
musculoskeletal radiology. No other images were available for evaluation. Both
radiologists were blinded to the clinical data, including the findings in the
surgery reports. The results of this analysis were not compared with the
original examination report because the original imaging interpretations did
not address all of the features of this study.
The presence or absence of communicating and noncommunicating triangular fibrocartilage tears was recorded. A communicating tear was defined as a tear in the triangular fibrocartilage that allowed passage of contrast material from the DRUJ into the radiocarpal compartment. A noncommunicating tear was defined as localized leakage of contrast material within the triangular fibrocartilage without communication to the adjacent compartment. The location of a tear was characterized either as a central tear including the radial attachment or as a tear at the ulnar attachment. For this study, only the ulnar attachment tears were further analyzed.
Analysis of Surgical Reports
All surgical reports were reviewed by a hand surgeon with 12 years of
experience in wrist arthroscopy. The surgical reports were categorized as
normal or ulnar attachment tear. An ulnar attachment tear was assumed in cases
in which the surgeon had no direct view of the ulnar attachment but diagnosed
a tear on the basis of absence of the so-called trampoline effect
[9]. The trampoline effect is
an important diagnostic finding at arthroscopy when the DRUJ is not accessible
and arthroscopic assessment involves the radiocarpal joint only. Normal
attachment causes a trampoline effect when the triangular fibrocartilage is
pushed with an arthroscopic probe. A tear causes a softness or sponginess of
the usually tense, resilient triangular fibrocartilage.
Data Analysis
Sensitivity, specificity, and accuracy were determined for ulnar attachment
tears. A true-positive result was accepted only when the pathologic condition
(communicating or noncommunicating tear) and location corresponded between
imaging and surgery. Error analysis was performed for all false-negative and
false-positive results. SPSS software for Windows version 11.5.0, 2002 (SPSS)
was used for statistical analysis.
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Diagnostic Accuracy
At MR arthrography, communicating tear (Figs.
1A and
1B) was diagnosed at the ulnar
attachment in three patients, noncommunicating tear (Figs.
2A,
2B,
3A,
3B,
4A, and
4B) in 19 patients, and normal
attachment (Figs. 5A and
5B) in 19 patients.
Arthroscopy revealed a tear in all three patients with a diagnosed
communicating tear on MR arthrography, in 14 of 19 patients with a
noncommunicating tear, and in three of 19 patients with a normal attachment
(Table 1). The sensitivity was
85% (17/20), specificity was 76% (16/21), and accuracy was 80% (33/41).
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Error Analysis
False-negative findings (three cases)—In a 30-year-old
patient, a complete tear was seen at the ulnar attachment at arthroscopy, but
MR arthrography did not depict a tear. A subtle increase in signal intensity
at the ulnar attachment was interpreted prospectively by the consensus
reviewers as physiologic signal intensity. In a 55-year-old patient, ulnar
detachment tear in the most dorsal aspect of the triangular fibrocartilage was
recognized retrospectively; this finding corresponded to the surgical report.
In the more palmar aspects of the triangular fibrocartilage, imaging and
arthroscopic findings were normal (Figs.
6A and
6B). In an 18-year-old
patient, a tiny linear increase in signal intensity on a T1-weighted
fat-suppressed image was not recognized prospectively.
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Peripheral tears of the ulnar attachment of the triangular fibrocartilage have been an imaging enigma on both conventional arthrography and MRI. Although tears of the triangular fibrocartilage in the radial or central aspect are easily seen, tears at the ulnar attachment are frequently missed [2, 5]. Trumble et al. [6] correlated 23 preoperative conventional arthrograms with arthroscopic findings in the triangular fibrocartilage. Twelve of the patients with abnormal arthrographic findings had avulsion of the triangular fibrocartilage from the sigmoid notch at the radius [10]. Eight of the 11 patients with normal arthrograms had tears at the ulnar styloid capsular attachment of the triangular fibrocartilage, and three had volar tears. Trumble et al. did not specify whether radiocarpal or DRUJ arthrography was performed.
Standard MRI has been of limited utility in the evaluation of peripheral tears at the ulnar attachment of the triangular fibrocartilage [1, 2, 5]. Totterman et al. [1] used high-quality standard MR images that allowed detection of 11 of 12 communicating triangular fibrocartilage tears. On the other hand, lesions of the ulnar attachments were often overstaged. Haims and colleagues [5] identified a sensitivity of 17% and specificity of 79% in the diagnosis of 20 surgically confirmed peripheral tears of the ulnar attachment. Although we had no direct comparison between standard MRI and MR arthrography, our results (sensitivity, 85%; specificity, 76%) indicate that MR arthrography with contrast injection into the DRUJ is an adequate way to resolve the diagnostic problem of peripheral triangular fibrocartilage tears, especially noncommunicating tears involving only the proximal surface of the triangular fibrocartilage, which usually are not depicted on radiocarpal MR arthrography. Further studies are needed to compare standard MRI with MR arthrography in the evaluation of peripheral triangular fibrocartilage tears. One can speculate that the use of 3-T MRI rather than 1.5-T MRI may overcome the shortcomings of 1.5-T MRI [11]. Further studies are needed to determine whether improved depiction with 3-T standard MRI is associated with higher diagnostic accuracy in the detection of peripheral triangular fibrocartilage tears.
The strength of MR arthrography with contrast injection into the DRUJ can be explained by the fact that this technique allows better differentiation of a tear from the physiologic high signal intensity caused by the vascularized ligamentum subcruentum. Our results confirm that tears at the ulnar attachment often appear on images as noncommunicating tears extending from the DRUJ into the triangular fibrocartilage [8]. Therefore, noncommunicating tears of the proximal surface of the triangular fibrocartilage may not be depicted with MR arthrography in which only the radiocarpal joint is injected. The location of these noncommunicating tears extending from the DRUJ into the triangular fibrocartilage may be explained by the histologic findings in this region. Benjamin and colleagues [7] described the ulnar part of the triangular fibrocartilage as split into two laminae. Strands of collagen from the more proximal lamina run through a region of vascular connective tissue toward the ulna. This vascularized connective tissue is looser than that of the more distal lamina, which extends beyond the ulna and blends with the dense fibrous connective tissue of the prominent sheath of the extensor carpi ulnaris tendon. This dense distally located fibrous connective tissue seems less likely to undergo degeneration or tearing than does the proximal cartilage of the triangular fibrocartilage and the more proximal lamina [12].
Zanetti et al. [8] found that on conventional arthrography, noncommunicating tears of the ulnar attachment of the triangular fibrocartilage have a more reliable association with symptoms than do communicating tears in the radial or central aspect of the triangular fibrocartilage. In patients with unilateral wrist pain, 69% of radial or central triangular fibrocartilage tears were present bilaterally, whereas noncommunicating triangular fibrocartilage tears were bilateral in only 39% of patients [8]. In that study, there was no surgical confirmation of the arthrographic findings. The present study confirmed that such noncommunicating tears of the ulnar attachment of the triangular fibrocartilage correlate with tears found at arthroscopy. Fourteen of 19 noncommunicating tears of the ulnar attachment of the triangular fibrocartilage diagnosed on MR arthrography correlated positively with arthroscopic findings. Although the hand surgeon did not consistently discriminate between communicating and noncommunicating tears, we had examples (Figs. 2A, 2B, 3A, 3B, 4A, and 4B) in which the hand surgeon insisted that the tear involved the full thickness of the ulnar insertion although the MR report described only a noncommunicating tear. These experiences emphasize that noncommunicating triangular fibrocartilage tears are worthwhile to note in MR reports.
Peripheral tears of the triangular fibrocartilage ulnar attachment are clinically important because they can be associated with instability of the DRUJ [10, 13]. Moreover, peripheral and central lesions of the triangular fibrocartilage must be differentiated because the therapeutic strategies are radically different. Peripheral tears have a good vascular supply and are repaired; central lesions are avascular and are commonly managed with débridement [14, 15]. In accordance with this experience, in our study repair with reattachment of the triangular fibrocartilage was the most common surgical procedure for peripheral tears.
Arthroscopy reveals most tears of the ulnar attachment of the triangular fibrocartilage. However, in the usual case, the ulnar attachment cannot be seen from the radiocarpal joint. Arthroscopists advocate use of the so-called trampoline effect to resolve this diagnostic problem, but the presence of this sign is indirect confirmation of the diagnosis [9]. Whether arthroscopy or MR arthrography is more accurate when no direct view of the triangular fibrocartilage along both its proximal and distal surfaces is available at arthroscopy is a topic for continued discussion. Another shortcoming of this study is that there was a delay of up to 16 weeks between MR arthrography and arthroscopy. During such a delay an incomplete tear can become complete, and a tear seen at MR arthrography can fill in with tissue as a healing reaction, rendering such a tear not detectable at arthroscopy.
In conclusion, MR arthrography performed after injection of iodine- and gadolinium-containing contrast agents into the DRUJ in evaluation of ulnar-sided wrist symptoms is an adequate imaging tool for assessment of peripheral tears of the ulnar attachment of the triangular fibrocartilage. These lesions often appear as noncommunicating tears extending from the DRUJ into the triangular fibrocartilage. Failure to inject contrast medium separately into the DRUJ can obscure the diagnosis of noncommunicating ulnar-sided tear of the proximal surface of the triangular fibrocartilage.
Acknowledgments
We thank the following orthopedic hand surgeons for referring their
patients and providing the surgical reports: Madleine Bardola, Zurich; Peter
E. Bleuler, Rueti; Charles E. Dumont, Zurich; Simone Feurer, Wetzikon; Markus
Hilty-Haab; Zurich, and Karl Mueller, Schlieren, Switzerland.
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