SEVEN YEARS EXPERIENCE WITH SYNTHETIC CERAMIC MATERIAL FOR REVISION TOTAL HIP ARTHROPLASTY

Abstract

Purpose: Revision surgery for total hip arthroplasty (THA) is frequent and defect filling has become a daily problem. Morbidity and insufficient graft supply complicate the problem. Worry about the long-term outcome of certain allografts together with the nearly complete disappearance of xenografts has led to wide development of the use of synthetic ceramic materials.

Material and methods: We have used two biphasic calcium phosphate (BCP) synthetic ceramics for revision THA since October 1996. The first is supplied in quadrangular granules measuring a few mm on a side. It is composed of 55% hydroxyapatite (HA) and 45% tri-calcium phosphate (TCP). It presents pores of approximately 400 microns in diameter, total porosity, total interconnection of 60%. It is indicated for filling bony defects. The second BCP is composed of 65% HA and 35% TCP with smaller pores (200 mm) and a non-totally interconnected porosity so the compression resistance is 20–30 MPa. This material is indicated for mechanical support more than filling. Sixty-six femurs and 75 acetabula were reconstructed with these materials and reviewed at three to seven years. Granules were used alone for cavitary bone defects, both for acetabular defects and femoral defects as well as for reconstruction along osteotomy borders or fractures. For stage II ace-tabular bone loss, and some stage III cases, we preferred large-sized press fit cups on the residual bone. When this was not possible for greater stage III and IV segmentary bone loss, reconstruction was achieved with supporting rings anchored in the obturator foramen and applied to disks or other shapes of the second more dense ceramic material which allows greater loading. This second BCP was also very useful when the femoral cortical was too thin to support fixation alone by transfemoral cerclage. The material provided supplementary compression resistance.

Results and discussion: There were no biological problems. There were two mechanical acetabular failures and five femoral failures which were secondary to technique errors or poorly adapted implants. Radiographic controls visualised substitute integration in contact with the recipient site. The granules resorbed progressively. The central more dense zone of the ceramic retained its density unchanged at five years while the material was resorbed progressively on the periphery. Histologically, integration of both BCP ceramics was proven on examination of biopsies.

Conclusion: Despite this still mid-term follow-up of seven years, we can confirm that BCP ceramics are an attractive alternative for revision THA. In our experience, these ceramic materials are safe and efficient if classical indications and techniques for revision surgery are respected.