The midterm and long-term effects of acetabular roof ring and Burch-Schneider anti-protusio cages in acetabular revisions for patients with acetabular bone deficiency.

OBJECTIVE: The purpose of this study was to investigate the mid-term and long-term effects of the acetabular roof ring (ARR) and Burch-Schneider anti-protrusio cage (BSAPC) in acetabular revision for patients with acetabular bone deficiency and acetabular component loosening.

METHODS: Between 1988 and 2007, ARR revisions were performed in 51 patients (25 women; average age: 46.9 years) and BSAPC in 18 patients (16 women; average age: 62.1 years). Grafts were used in all revisions. The patients were evaluated retrospectively. The bone defects were classified according to the classification of the American Academy of Orthopaedic Surgeons (AAOS). Harris Hip Score (HHS) was used for clinical evaluation. Radiolucent lines, implant sizes, osseointegration, and heterotopic ossification in the 3 regions defined by DeLee and Charnley were evaluated radiologically.

RESULTS: The success rate of ARR revisions after an average follow-up of 8.93±4.10 years (range: 4-23 years) was 87.9%, and the cumulative survival rate at year 10 postoperatively was 91%. Average HHS score increased to 83.70±8.98 postoperatively, from 40.10±2.49 preoperatively (p<0.01). The success rate of BSAPC revisions after an average follow-up of 7.06±2.39 years (range: 4-12 years) was 83.3%, and the cumulative survival rate was 78%. Average HHS score increased from 42.55 preoperatively to 73.86 postoperatively (p<0.01). All failures of ARR revisions occurred in type 3 defects (p<0.05). In 40 of the 47 patients in which an allograft was used, osseointegration occurred. No statistically significant difference was found between the increase in HHS scores of patients who underwent femoral component revision with acetabular revision and those who did not (p=0.06). Patients who underwent more than 1 revision had statistically significantly higher failure rates in comparison to patients undergoing revision for the first time (p=0.008).

CONCLUSION: The mid-term and long-term results of the use of ARR and BSAPC with allografts in bone deficient acetabular revisions are satisfactory. The implants facilitate graft osseointegration, increase the bone stock, and make future revisions easier. ARR should be preferred in type 1 and type 2 acetabular bone defects, while BSAPC should be preferred in type 3 and 4 defects.