The accuracy of T1-, proton-density-, and T2-weighted magnetic resonance (MR) imaging sequences and gadolinium-enhanced MR arthrography in evaluation of the triangular fibro-cartilage complex (TFCC) and the scapholunate (SL) and lunotriquetral (LT) ligaments was studied in 15 patients with chronic wrist pain. Arthrography and arthroscopy were used as standards of reference. Twelve patients also underwent imaging with short tau inversion recovery (STIR) sequences. MR imaging was more reliable in evaluation of the morphology of the TFCC and SL ligament than in that of the LT ligament. With arthrography as the standard, sensitivity was 0.721, specificity was 0.947, and accuracy was 0.887 for the TFCC; these values were 0.500, 0.864, and 0.765 for the SL ligament and 0.519, 0.455, and 0.490 for the LT ligament. No visualization of the SL ligament indicated a tear, but this sign was not helpful in evaluation of the LT ligament. Fluid in the distal radioulnar joint had a high association with TFCC tears. Accuracy with MR arthrography was higher than with the other sequences. STIR images were effective in evaluation of the TFCC. The combination of proton-density-and T2-weighted images appears to be useful because morphologic characteristics and the presence of fluid can be evaluated.

Spontaneous osteonecrosis about the knee typically is a disease of the elderly characterized by an acute onset of pain. The exact cause of this condition has long been debated, although a causative relationship between meniscal tears and spontaneous osteonecrosis about the knee has been postulated. Seven patients with knee pain, meniscal tears, and chondromalacia without initial evidence of osteonecrosis at magnetic resonance (MR) imaging underwent arthroscopic surgery with meniscal recontouring or repair and cartilage shaving. These patients returned within 2-14 months with recurrent pain in the treated knee. MR imaging then demonstrated abnormalities consistent with osteonecrosis. Osteonecrosis of the femoral condyle or tibial plateau may be a late sequela of meniscal injury in association with chondromalacia and arthroscopic surgery. This diagnosis should be suspected in patients with recurrent knee pain after arthroscopic repair of meniscal tears. The precise relationship of this pattern of osteonecrosis to that previously described as spontaneous requires further investigation.

Insufficiency fractures of the sacrum are a commonly recognized form of stress fracture typically occurring in elderly patients. As such patients usually present with low back pain, MR imaging is often performed initially as a means of evaluation. We present 5 patients with sacral insufficiency fractures imaged with MR. Metastatic disease was a leading clinical suspicion as all patients were elderly and three had known primary neoplasms. T1-weighted sequences demonstrated bands of decreased signal intensity, usually paralleling the sacral aspect of the sacroiliac joints and occasionally occurring as a horizontal band across the sacral body. Four of five patients underwent further evaluation with computed tomography (CT) or nuclear bone scanning, which confirmed the diagnosis of sacral insufficiency fracture. We conclude that MRI is sensitive but not specific in detecting sacral insufficiency fractures. As MR imaging is rapidly becoming the method of choice for evaluating back pain, it is important to consider this diagnosis in elderly persons.

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To provide further understanding of the magnetic resonance (MR) signal intensities in the triangular fibrocartilage (TFC) and interosseous ligaments of the wrist, the authors performed MR imaging with gross pathologic and histologic analysis in 10 cadaveric wrists. Spin-echo T1- and T2-weighted coronal images were obtained, and 3-mm coronal sections of the specimens were then made that correlated precisely with the MR images. Normal portions of the TFC showed asymmetrical bow tie-like low signal intensity, except near the radial and ulnar attachments. Degeneration of the TFC, present in all cases, was more severe on the proximal surface and was characterized by high signal intensity on T1-weighted images and less high signal intensity on T2-weighted images. These findings differed from those in TFC perforation, which showed high signal intensity on T2-weighted images. Similar signal intensity characteristics could allow differentiation of degeneration and perforation of the scapholunate and lunotriquetral ligaments. These findings suggest that in vivo MR imaging may accurately delineate degeneration and perforation of the TFC and intercarpal ligaments.

Sensitivities and specificities of the six MR criteria were 90.5-100%, and 6.7-86.7%, respectively, both before and after exercise. Likelihood ratios proved statistically significant differences between the symptomatic and asymptomatic wrists (P < 0.0001-0.0002) for the prevalence of all MR criteria with the exception of fluid within the carpal joints and/or carpal tunnel. Changes of the MR appearance after exercise had a low sensitivity (4.8-71.4%) but high specificity (86.7-100%) for dynamic carpal tunnel syndrome. In conclusion, MR imaging contributes to the diagnosis of carpal tunnel syndrome when clinical signs are confusing and electrodiagnostic studies are negative. Dynamic examinations improve specificity of MR imaging for such diagnosis.

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