Abstract
Lesions of the acetabular rim have been implicated as a cause of hip pain in various pathologic conditions and are considered to predispose the hip to development of accelerated degenerative disease. In developmental dysplasia of the hip (DDH) and anterior femoroacetabular impingement (FAI), intrinsically normal intraarticular soft tissue structures are exposed to joint loading forces that physically exceed their tolerance level posing these pathomorphologies as precursors of osteoarthritis. In DDH, the deficient acetabular coverage of the femoral head has been related to osteoarthrosis, while the orientation of the femoral head is considered to play a less important role. The resulting instability and anterolateral migration tendency of the femoral head leads to chronic shear stresses at the acetabular margin. In FAI, repetitive peak contact pressures occur when the femoral head-neck junction abuts against the acetabular rim during joint flexion. Predisposing morphologies are femoral abnormalities such as an insufficient femoral head-neck offset seen in head tilt or pistol grip deformities, slipped capital femoral epiphysis, or malunited femoral neck fractures with the orientation and shape of the acetabulum contributing to this pathology. In classical DDH and FAI, diagnosis is primarily based on clinical signs and symptoms and conventional radiography. However, in cases of clinical and radiographic borderline disease establishment of the correct diagnosis is sometimes difficult. This presentation reports how the MRarthrographic appearance of acetabular rim pathologies can be used to differentiate both conditions. In DDH and FAI, labral pathologies localize identically with a predilection to the anterosuperior quadrant of the acetabulum. Labral tears are found in 64% in both groups. The volume of the labrum is increased in 86% DDH hips but in none of the FAI hips. Ganglion formation in the periacetabular area is seen in 71% DDH and 21% FAI hips. These findings provide evidence that the anterosuperior acetabular rim represents the initial fatiguing site of the hip under both DDH and FAI. The capability of MR-arthrography to depict differences in labral pathologies suggests this method as a helpful diagnostic tool to define the most appropriate treatment strategy specifically in borderline cases.
Theses abstracts were prepared by Professor Roger Lemaire. Correspondence should be addressed to EFORT Central Office, Freihofstrasse 22, CH-8700 Küsnacht, Switzerland.
