Cartilage thickness in the hip joint measured by MRI and stereology--a methodological study.

OBJECTIVE The purpose of this study was to develop a precise and efficient method for estimating the thickness of the articular cartilage in the hip joint and hence three different stereologic methods were tested based on Magnetic Resonance Imaging. DESIGN Twenty two females and four males with hip dysplasia underwent MRI. The thickness of the femoral and acetabular cartilage was estimated. RESULTS The results for all three methods showed that the observed total variance on cartilage thickness is small. The mean thickness of the acetabular cartilage measured by the three different methods ranged between 1.15 mm and 1.46 mm. The mean thickness for the femoral cartilage measured by the three different methods ranged between 1.18 mm and 1.78 mm. The measurements took 15-20 min per hip to carry out. CONCLUSION Methods 1 and 3 are as precise but we favour method 3 because the measurements are done on images obtained through the center of the femoral head which means that the cartilage surface is intersected perpendicular and partial volume effect avoided. We suggest that this method can be advantageous for assessing the progression of osteoarthritis in dysplastic hips after periacetabular osteotomy.