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Low-Field-Strength MR Imaging of Failed Hip Arthroplasty: Association of Femoral Periprosthetic Signal Intensity with Radiographic, Surgical, and Pathologic Findings¹

¹ From the Department of Radiology, Showa University Fujigaoka Hospital, Yokohama, Kanagawa, Japan (H.S., A.F., Y.K., W.Y.); Department of Orthopedics, Showa University Fujigaoka Rehabilitation Hospital, Yokohama, Kanagawa, Japan (I.H., Y.I.); and Department of Science, Tokyo University of Science, Japan (E.M.). Received August 29, 2002; revision requested October 24; final revision received April 25, 2003; accepted May 19. Address correspondence to H.S., Department of Radiology, Jichi Medical School, 3311 Yakushiji, Minamikawachimachi, Kawachi-gun, Tochigi-ken 329-0431, Japan (e-mail: sugimoto@jichi.ac.jp).

PURPOSE: To investigate the association between periprosthetic signal intensity at low-field-strength magnetic resonance (MR) imaging after failed hip arthroplasty and radiographic, surgical, and pathologic findings.

MATERIALS AND METHODS: The study group comprised 22 consecutive women who underwent hip arthroplasty (mean age, 62 years; age range, 35–74 years). All patients underwent MR imaging prior to revision surgery. Coronal fast short inversion time inversion-recovery (STIR) images and spin-echo T1-weighted images were obtained with a 0.5-T MR imaging unit before and after administration of contrast material. The periprosthetic region was divided into the seven femoral Gruen zones. Two observers retrospectively analyzed signal intensity patterns. Association of signal intensity patterns with radiographic, surgical, and pathologic findings was determined with ² analysis and generalized estimating equations.

RESULTS: Diagnostic-quality images were obtained for 150 zones. Periprosthetic signal intensity was greater than that of bone marrow in the distal femur on the fast STIR images, and no contrast enhancement was seen on the T1-weighted images (type I signal intensity pattern) in 11 zones. Signal intensity was greater than that of bone marrow on the fast STIR images, and contrast enhancement was seen on the T1-weighted images (type II signal intensity pattern) in 45 zones. Signal intensity was less than or equal to that of bone marrow on the fast STIR images, and no contrast enhancement was seen on the T1-weighted images (type III signal intensity pattern) in 94 zones. Type I and II patterns were associated with focal or nonfocal lucency, an unstable stem, and fibrosis or granuloma. A type III pattern was associated with a normal radiographic appearance, a stable stem, and normal bone tissue. Significant association was demonstrated between periprosthetic signal intensity and radiographic (P < .001, ² test and generalized estimating equations), surgical (P < .05, Mantel-Haenszel ² test and generalized estimating equations), and pathologic findings (P < .05, ² test).

CONCLUSION: Low-field-strength MR imaging depicted periprosthetic tissue signal intensity that was significantly associated with radiographic, surgical, and pathologic findings.

© RSNA, 2003

Index terms: Hip, MR, 442.121411 • Hip, prostheses, 442.454 • Magnetic resonance (MR), low-field-strength imaging, 442.121411, 442.121413 • Hip, surgery, 442.458

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