299. CLINICAL AND RADIOGRAPHIC RESULTS OF A LONG LOCKED TOTALLY HYDROXYAPATITE-COATED STEM FOR COMPLEX AND REVISION HIP SURGERY

Abstract

Purpose of the study: The pertinence of locking for major femoral revision remains a controversial issue. We conducted a retrospective multicentric study to assess the benefit and potential clinical and radiographic complications after using a long locked stem entirely coated with hydroxyapatite.

Material and methods: Our series included 77 patients (42 women, 35 men), mean age 71 years (range 34–90) reviewed at minimum one year. A modular implant was used; the long curved stem allowed total integration. Screws guaranteed distal locking. There were 71 revision THA on trochanteric-shaft fractures, three shaft nonunions, 34 aseptic loosenings, 9 septic loosening, 21 fractures on prosthesis, 6 implant failures and one instability. Seventy percent of patients had stage 3 and 4 bone lesions. Mean follow-up was 60 months.

Results: At last follow-up, 90% of patients were satisfied or very satisfied. The mean Harris function score improved from 32 to 83 and the PMA from 7 to 15. Sixty-four patients were pain free and 22% had pain solely under stress. There were 15 bone complications: dislocation (n=3), early infection (n=3 including 2 recurrences), implant failure (n=2), secondary femur fracture (n=5). Stem survival was 94% at nine years. Radiographically, total stem stability was noted in 73 patients (95%); instability was noted in four cases of fracture. Undeniable metaphyseal improvement was noted in 20% of cases, more modest improvement in 32%; the situation was considered unchanged in 31%. Locking was successful in all cases; cortical bone in contact with the locking screw was unchanged in 59 cases, slightly thickened in 16, including one case with a context of septic recurrence. The locking was dismantled in two cases (one empirically and one for pain), but the stem remained stable.

Discussion: Major damage to the femur can compromise stabilisation of the proximal or diaphyseal implants. Distal locking contributes to the initial mechanical stability, indispensable for secondary osteointegration of the implant. However, with total hydroxyapatite coating, rapid fixation in healthy zones is also crucial. Reconstruction of metaphyseal bone is not easy to quantify, but the absence of bone absorption is noteworthy.