[The Osaka concept. "Dome osteotomy" with of without labrum resection].

: Acetabular dysplasia represents the most common aetiology for secondary osteoarthritis of the hip joint in Japan. On radiographs progress of the disease can be classified in four stages (I to IV). Labral lesions are common accompanying findings in acetabular dysplasia, representing an important prognostic factor. Therefore we routinely use conventional arthrography to classify labral lesions in three types (normal, torn and detached). From 1978 to 1983 a modified Chiari osteotomy of the pelvis (dome osteotomy) was performed in 64 hip joints without arthrotomy. The preoperative radiography showed labral lesions in 66%. After an average follow-up of 4 years, 43 of the 44 patients with a normal or torn labrum showed excellent or good results. On contrast, 50% of the 20 patients with a detached labrum showed fair and poor results only. From 1984 to 1989 an arthrotomy was combined with dome osteotomy in 29 hip joints and labral lesions had to be resected in 16 cases. The results were generally good in patients with arthrosis grade I and II, but in stage III they were only fair. Thus, the success of labral surgery can only be achieved in early stages of dysplasia. Based on our findings dome osteotomy combined with arthrotomy and labral surgery can be recommended in patients with labral lesions and hip dysplasia grade I and II.