A follow-up study on bipolar endoprosthesis for patients under 60 years old was made on 3 6 hip joints in 3 4 patients (osteoarthritis: 13 joints; avascular necrosis of the femoral head: 15 joints; and femoral neck fracture: 8 joints) . The average age was 52. The clinical results assessed by the JOA score and roentgenographical study of migration and sinking of the prosthesis were followed during periods ranging from 2 years to 9 years and 7 months. Twenty-eight joints were satisfactory. Sinking only and migration only were seen in 3 joints: both sinking and migration were observed in 4.
