• Christian W A Pfirrmann, Hubert P Notzli, Claudio Dora, Juerg Hodler, and Marco Zanetti.
• Department of Radiology, University Hospital Balgrist, Forchstrasse 340, CH-8008 Zurich, Switzerland. christian@pfirrmann.ch
• Radiology. 2005 Jun 1; 235 (3): 969-76.

PurposeTo prospectively evaluate magnetic resonance (MR) imaging findings of abductor tendons and muscles in asymptomatic and symptomatic patients after lateral transgluteal total hip arthroplasty (THA).Materials And MethodsThe institutional review board approved the study, and all patients provided informed consent. Two musculoskeletal radiologists blinded to clinical information analyzed triplanar MR images of the greater trochanter obtained in 25 patients without and 39 patients with trochanteric pain and abductor weakness after THA. Tendon defects, diameter, signal intensity, and ossification; fatty atrophy; and bursal fluid collections were assessed. In 14 symptomatic patients, MR imaging and surgical findings were correlated. Differences in the frequencies of findings between the two groups were tested for significance by using chi2 analysis.ResultsTendon defects were uncommon in asymptomatic patients and significantly more frequent in symptomatic patients: Two asymptomatic versus 22 symptomatic patients had gluteus minimus defects (P < .001); four asymptomatic versus 24 symptomatic patients, lateral gluteus medius defects (P < .001); and no asymptomatic versus seven symptomatic patients, posterior gluteus medius defects (P = .025). In both patient groups, tendon signal intensity changes were frequent, with the exception of those in the posterior gluteus medius tendon, which demonstrated these changes more frequently in symptomatic patients (in 23 vs five asymptomatic patients, P = .002). Tendon diameter changes were frequent in both groups but significantly (P = .001 to P = .009) more frequent in symptomatic patients (all tendon parts). Fatty atrophy was evident in the anterior two-thirds of the gluteus minimus muscle in both groups, without significant differences. In the posterosuperior third of the gluteus minimus muscle, however, differences in fatty atrophy between the two groups were significant (P = .026). Fatty atrophy of the gluteus medius muscle was present in symptomatic patients only, with significant differences among all muscle parts. Bursal fluid collections were more frequent in symptomatic patients (n = 24) than in asymptomatic patients (n = 8, P = .021). The MR imaging-based diagnosis was confirmed in all 14 patients who underwent revision surgery.ConclusionAbductor tendon defects and fatty atrophy of the gluteus medius muscle and the posterior part of the gluteus minimus muscle are uncommon in asymptomatic patients after THA.Copyright RSNA, 2005.

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