In revision THA, the solid acetabular reconstruction in the true acetabulum is often challenging. We are using the Kerboull acetabular reinforcement devices after packing hydroxyapatite granules for acetabular bone defects. We report our 3–7 year clinical and roentgenographical results.

Twenty-one acetabuli in 20 patients were reconstructed in the true acetabuli with Kerboull-type acetabular reinforcement devices and porous hydroxyapatite granules (Sumitomo Pharmaceutical Co. Ltd.). The mean age of the patients at operation was 68 years. The mean follow-up period was 5 years and 3 months (38–88 months). Acetabular bone deficiencies were evaluated according to AAOS classification (type II: 5 hips, type III: 16 hips). Porous hydroxyapatite granules (20–60 grams) were grafted to all the acetabuli. Autologous cortico-cancellous bone grafts or hydroxyapatite blocks were used to reconstruct the segmental defects in 6 hips. All the acetabuli were reinforced with Ker-boull-type reinforcement devices and Charnley-type cemented prostheses were implanted. Clinical and roent-genographical results were evaluated using Japanese Orthopaedic Association hip score and Hodgkinson classification. Average hip score was improved from 42 points to 75 points. No re-revision was done. No infection was noted. The roentgenograms showed neither migration nor loosening of the acetabular components.

Porous hydroxyapatite granules are one of the best bone substitutes because of their mechanical and biochemical properties. Oonishi reported very good results of his acetabular reconstruction using this material. The Kerboull-type acetabular devices are very effective to the reconstruction in the true acetabulum. Excellent results of these devices were reported by Kerboull. Ace-tabular reconstrution using both of them showed very good clinical and roentgenographical results during 3 to 7 post-operative years in our series.

We prepared a prosthesis for the replacement of the lumbar vertebrae of sheep, using apatite- and wollastonite-containing glass-ceramic. The material is stronger than human cortical bone and has the special feature of chemical bonding to bone. Ten sheep underwent replacement of L3 and L4 vertebrae, without bone grafting. The animals were killed at intervals from three months to 27 months after operation, and the interface between the prosthesis and bone was examined radiologically, histologically and crystallographically. Bone bonding with the prosthesis had occurred in half the implants. It took at least one year for bonding to be complete, but an apatite layer on the surface of the prosthesis was observed as early as three months after the operation, suggesting the possibility of much earlier bone bonding if more rigid fixation of the prosthesis had been provided.

Ultrasound can be used to outline the spinous processes and the laminae, and thus to measure axial rotation. Using our own technique, we measured vertebral rotation in 47 patients with idiopathic scoliosis. There was a strong linear relationship between the Cobb angle and the rotation of the apical vertebra in untreated patients, but this relationship was lost in patients who had had brace treatment. Vertebral rotation can easily be measured by ultrasound. This is a harmless and fairly rapid investigation which can be used at routine follow-up examination of patients with idiopathic scoliosis.