ANATOMIC REVISION OF THE FEMORAL STEM WITH COMPLETE HYDROXYAPATITE COATING: 75 HIPS WITH MEDIAN FOUR YEAR FOLLOW-UP

Abstract

Purpose: The aim of this work was to assess retrospectively osteofixation and survival of a long custom-made femoral stem with complete hydroxyapatite coating and without locking for replacement of the femoral implant.

Material and methods: From 1990 to 1999, 89 stems were implanted for revision total hip arthroplasty. Seventy-five hips were reviewed at one to ten years (mean four years). Radiographic analysis searched for bone damage, osteofixation and implant migration. All measures were taken on the AP views postoperatively and at last follow-up.

Results: Revision was performed for aseptic loosening in 75%, for septic loosening in 12%, for fracture in 11% and for instability in 2%. Destruction was SOFCOT stage I in 36%, stage II in 44%, stage III in 17% and could not be assessed in 3%. The femorotomy approach was used in 60% and trochanterotomy in 32% and endofemoral assess in 8%. There were 18% intraoperative fractures, 4.8% postoperative infections and 2.4% dislocations. At last follow-up, the Postel Merle d’Aubigné score was 15.3 and the Harris Hip Score was 77.9. Thigh pain was present in 4%. Bone fixation was considered good in 48%, partial but better than 50% contact in 36% and could not be interpreted in 16%. Complete metaphyseal reconstruction was present in 8%. A piecemeal allograft was used in 89%. Between the postoperative and last follow-up films, 16% of the stems descended a mean 11 mm. Five percent of the stems were removed for infection and one (1.3%) for non-fixation. At five years, 95% of the stems was still in place and 80% at ten years, including removals for infection. All revisions for septic loosening had comparable clinical and radiological results in this series and did not develop secondary infection.

Discussion: These results demonstrate the usefulness of the uncemented stems for replacement compared with cemented stems which have a 10% revision rate at five years (SOFCOT 1999). The complete hydroxyapatite coating improves distal fixation of the stem in a healthy zone without compromising secondary proximal fixation and authorising spontaneous metaphyseal bone reconstructions. This may explain the low rate of painful thighs. Modularity and locking could improve the primary fixation and limit descent.