Miranda Jane Miocevic MBCHB, Presenter: Nothing to Disclose

Frank Malara MD, Abstract Co-Author: Nothing to Disclose

David Connell, Abstract Co-Author: Nothing to Disclose

John Pike MD, Abstract Co-Author: Nothing to Disclose

David Young, Abstract Co-Author: Nothing to Disclose

To describe the MR findings in a group of symptomatic patients with acetabular dysplasia.

25 patients (27 hips) with radiographic confirmation of acetabular dysplasia (centre edge angle There were 16 males and 9 females (mean age 31.2 years) with an average symptom duration of 16.2 months.A high resolution, non arthrographic technique was used to assess the labrum for signal and morphological abnormality. Separate lesions at the labral-chondral transitional zone termed acetabular RIM lesion were graded from I (thinning/irregularity), II (clefts /focal defect) , III ( acetabular chondral deficiency) to IV ( subcortical cyst formation/bone oedema).Comparison with hips of ten non dysplastic volunteers was also made.

The acetabular labra in the dysplastic hips demonstrated abnormal signal, were elongated and presumably assumed more weight bearing stress than in the nondysplastic group ( mean length 10.9mm v 6.4mm).Morphological appearances of the labra included fissures,clefts and globular change.MRI demonstrated 11 hips with Grade I lesions, 13 hips with Grade II lesions, 2 hips with Grade III lesions and 1 hip with a Grade IV lesion.In 24 of 27 hips (89%) MR and arthroscopic findings were consistent.Imaging and surgical gradings differed in 3 of the 27 hips (11%). In 2 cases MR described Grade II RIM lesions with no abnormality detected at arthroscopy.In one case MRI demonstrated a Grade I RIM lesion and avascular necrosis (AVN). The latter was confirmed at surgery however no RIM lesion was identified.

MRI shows that patients with acetabular dysplasia have elongated labra with focal abnormalities at the labral-chondral transitional zone (termed acetabular RIM lesion). These findings correlate well with those found at arthroscopy.

Miocevic, M, Malara, F, Connell, D, Pike, J, Young, D, MR Imaging of the Dysplastic Hip: The Acetabular Rim Lesion.  Radiological Society of North America 2004 Scientific Assembly and Annual Meeting, November 28 - December 3, 2004 ,Chicago IL. http://archive.rsna.org/2004/4410236.html