Double Cup Replacement of Hip Joint

Double cup replacement of the hip joint is a newly developed technique which preserves the femoral head and neck, and only the injured bony and cartilagenous surfaces of the joint are removed. Since Mar. to Nov. 1979 we have used this technique in a total of 21 cases. Femoral metallic cup was made of titanium alloy, the outer diameter of the cup being 40, 42, 44 and 46 mm. The acetabulum cup was made of nylon-6, its inner diameter being the same as the outer diameter of the metallic cup. The prosthesis was fixed to the bony structures by means of indigenously produced bone cement. The indication for this operation was bony ankylosis of the hip joint in 6 cases, among whom rheumatoid ankylosis was the cause for 5, and purulent infection for another. Osteoarthritis, either primary or secondary, was the indication for operation in 5 cases. There were 8 cases of vascular necrosis of femoral head due to administration of large doses of cortison for a long period, or following fracture of the neck of femur. The other two cases had, respectively, fracture of acetabulum and healed tuberculosis of the hip joint. If flexion deformity is present, Smith-Peterson incision is preferred, and sometimes adductor tenotomy is performed as an additional procedure before or after the main incision is made. In 19 cases of this series, the lesions were exposed by anterolateral incision, while posterolateral Gibson incision was used in only two cases. There was no post-operative infection. Because patients have only been followed up for a short period, it might be too early to evaluate the operation. The advantages of the operation are: 1. painless joint is obtained; 2. the hip joint regains a very good motion; 3. stable joint with negative Trendelenberg sign is provided; 4. absence of shortening of the operated limb; 5. less bleeding during operation; and 6. total replacement of hip can be performed again if necessary. However, it is hard to tell at present how long can the prosthesis be tolerated until more observation is made.