Radiographic Features Associated With Differing Impinging Hip Morphologies With Special Attention to Coxa Profunda

Department of Orthopedics, Mayo Clinic, 200 First Street SW, Rochester, MN, 55905, USA.
Clinical Orthopaedics and Related Research (Impact Factor: 2.77). 08/2012; 470(12). DOI: 10.1007/s11999-012-2539-5
Source: PubMed


BACKGROUND: Combined with clinical examination and MRI, radiographs have been mainstays in the management femoroacetabular impingement (FAI). Because hip morphology often portends intraoperative damage, radiographic features should inform surgical management. QUESTIONS/PURPOSES: We determined (1) the radiographic features of the various hip morphologies; (2) the prevalence of radiographic coxa profunda in each group; (3) the radiographic differences between hips with and without coxa profunda; and (4) its sensitivity and specificity as a measure of global acetabular overcoverage. METHODS: We reviewed preoperative radiographs and operative notes of 144 hips that underwent surgical dislocation and correction for FAI between August 2002 and February 2011. Hips were divided into four FAI subtypes by radiographic analysis (cam, global overcoverage, retroversion, and combined) and three subtypes (cam, pincer, or combined) by intraarticular pathology. Standard radiographic measurements were performed, and we introduce a novel measurement that assesses femoral head coverage. RESULTS: We found differences in median Angle of Sharp, femoral head-neck angle, and median roof length (and its subset) among the FAI morphologies. The prevalence of radiographic coxa profunda was 48% in cam hips, 85% in global overcoverage hips, 66% in retroverted hips, and 32% in combined hips. The sensitivity and specificity of radiographic coxa profunda as a measure of global overcoverage was 75% (95% CI, 0.62-0.85) and 62% (95% CI, 0.51-0.73), respectively. CONCLUSIONS: We found major differences in radiographic measurements between FAI morphologies. Radiographic coxa profunda was poorly specific for global overcoverage. Measurement of roof length and ratio should be used to determine the morphology of the impinging hip. LEVEL OF EVIDENCE: Level II, prognostic study. See Guidelines for Authors for a complete description of levels of evidence.

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    ABSTRACT: Orthopaedic surgeons have accepted various radiological signs to be representative of acetabular retroversion, which is the main characteristic of focal over-coverage in patients with femoroacetabular impingement (FAI). Using a validated method for radiological analysis, we assessed the relevance of these signs to predict intra-articular lesions in 93 patients undergoing surgery for FAI. A logistic regression model to predict chondral damage showed that an acetabular retroversion index (ARI) > 20%, a derivative of the well-known cross-over sign, was an independent predictor (p = 0.036). However, ARI was less significant than the Tönnis classification (p = 0.019) and age (p = 0.031) in the same model. ARI was unable to discriminate between grades of chondral lesions, while the type of cam lesion (p = 0.004) and age (p = 0.047) were able to. Other widely recognised signs of acetabular retroversion, such as the ischial spine sign, the posterior wall sign or the cross-over sign were irrelevant according to our analysis. Regardless of its secondary predictive role, an ARI > 20% appears to be the most clinically relevant radiological sign of acetabular retroversion in symptomatic patients with FAI. Cite this article: Bone Joint J 2013;95-B:893-9.
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    ABSTRACT: Although radiographic coxa profunda has been considered an indicator of acetabular overcoverage, recent studies suggest that radiographic coxa profunda is a nonspecific finding seen even in hip dysplasia. The morphologic features of coxa profunda in hip dysplasia and the frequency with which the two overlap are not well defined. We determined (1) the prevalence of radiographic coxa profunda in patients with hip dysplasia; (2) the morphologic differences of the acetabulum and pelvis between patients with hip dysplasia and control subjects; and (3) the morphologic differences between hip dysplasia with and without coxa profunda. We retrospectively reviewed the pelvic radiographs and CT scans of 70 patients (70 hips) with hip dysplasia. Forty normal hips were used as controls. Normal hips were defined as those with a lateral center-edge angle between 25° and 40°. Coxa profunda was defined as present when the acetabular fossa was observed to touch or was medial to the ilioischial line on an AP pelvic radiograph. CT measurements included acetabular version, acetabular coverage, acetabular depth, and rotational alignment of the innominate bone. The prevalence of coxa profunda was 44% (31 of 70 hips) in dysplastic hips and 73% (29 of 40 hips) in the control hips (odds ratio, 3.32; 95% CI, 1.43-7.68). Dysplastic hips had a more anteverted and globally shallow acetabulum with inwardly rotated innominate bone compared with the control hips (p < 0.001). Dysplastic hips with coxa profunda had a more anteverted acetabulum (p < 0.001) and inwardly rotated innominate bone (p < 0.002) compared with those without coxa profunda, whereas the acetabular coverage and depth did not differ between the two groups, with the numbers available. Radiographic coxa profunda was not a sign of increased acetabular coverage and depth in patients with hip dysplasia, but rather indicates classic acetabular dysplasia, defined by an anteverted acetabulum with anterolateral acetabular deficiency and an inwardly rotated pelvis. Thus, the presence of coxa profunda does not indicate a disease in addition to hip dysplasia, and the conventional maneuvers during periacetabular osteotomy are adequate for these patients. Level IV, diagnostic study.
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