Acetabular bone defects in THA revision: Reconstruction using morsellised virus-inactivated bone allograft and reinforcement ring. Seven-year outcomes in 95 patients.

BACKGROUND: Acetabular cup loosening is among the main reasons for revision total hip arthroplasty (THA). The implantation of a cryopreserved morsellised bone allograft is a reference method for filling bone defects. However, the outcomes of bone grafts treated with viral inactivation and secured into the host bone (notably using a reinforcement device) are unclear. We therefore retrospectively reviewed cases of acetabular revision with morsellised bone allograft implanted into a reinforcement ring for acetabular revision to assess: (1) clinical survival of the acetabular implant (time to new revision with acetabular component removal), (2) radiological implant survival, (3) and bone graft osseointegration evaluated using Oswestry's criteria.

HYPOTHESIS: Virus-inactivated bone allografts provide similar outcomes to cryopreserved allografts.

MATERIAL AND METHODS: From 2004 to 2009, 95 patients underwent acetabular revision. There were 60 (63%) females and 35 (37%) males with a mean age of 71.7 years (range: 44.2-90 years). Over 90% of patients had bone defects type 2 or higher in the AAOS classification. Each patient was evaluated after at least 5 years, by an examiner who had not been involved in the revision and who determined the Postel-Merle d'Aubigné (PMA) score and patient satisfaction. We assessed the clinical survival of the acetabular implant (time to new revision with acetabular implant removal), radiological implant survival (migration>5mm, active radiolucent line, failure of graft osseointegration, or reinforcement ring failure), and allograft osteointegration evaluated using Oswestry's criteria.

RESULTS: After a mean follow-up of 7years (range: 5.2-10years), 7 (7.4%) patients had been lost to follow-up and 3 (3.4%) had required surgical revision, after 3 to 73 months (for aseptic loosening in 2 cases and infection in 1 case). The estimated 10-year survival rate was 96.2% (95% confidence interval [95%CI]: 88.2-98.7). The mean PMA score at last follow-up had increased significantly, by 2.8 points (p<0.05), to 13.8 (95%CI: 78.4-88.1). Of the 88 re-evaluated patients, 78 (89%) were satisfied or very satisfied. The overall radiological survival rate was 84.5% (95%CI: 78.4-88.1) after a mean of 5.9 years (range: 0.5-10). Allograft osseointegration was satisfactory (Oswestry score≥2) in 95.8% of patients.

DISCUSSION: In our population, allografts previously subjected to virus inactivation and implanted into a reinforcement ring produced outcomes similar to those reported previously with cryopreserved allografts.

LEVEL OF EVIDENCE: IV, retrospective case-series study.