Abstract
OBJECTIVE: This retrospective study aimed to compare radiodensity measurements and Goutallier grading systems for the evaluation of fatty infiltration in hip abductors. METHODS: The radiodensity of the gluteus minimus and medius muscles was measured in 80 hips of 40 patients. These muscles were graded for fatty infiltration using three five-grade classification systems: the original Goutallier classification on both computed tomography (CT) and magnetic resonance imaging (MRI), and a new objective classification based on the percentage of the functional muscle area (defined as 30-100 Hounsfield units). After measuring and grading the abductors, correlation coefficients between them were analyzed. RESULTS: Spearman's rank correlation coefficients (ρ) between radiodensity measurements of abductors and the Goutallier classification on CT and MRI were -0.701 and -0.552 for the gluteus minimus and -0.832 and -0.740 for the gluteus medius, respectively. Our new classification had correlation coefficients of -0.844 and -0.926 for the gluteus minimus and gluteus medius, respectively. CONCLUSIONS: Radiodensity measurements showed a strong correlation with the grading systems, particularly with the new classification based on the percentage of the functional muscle area. Considering the subjective nature of the original Goutallier grading systems, we conclude that radiodensity assessment is feasible and more objective for evaluating fatty infiltration in hip abductors.