Midterm results (5.5-10 years) of acetabular allograft reconstruction with the acetabular reinforcement ring during total hip revision.

Acetabular reconstructions using frozen femoral head allografts and the acetabular reinforcement ring of M. E. Müeller (Protek AG, Bern) have been analyzed after an average follow-up period of 7.2 years (range, 5.5-10 years) in 27 patients/hips. The deficiencies, according to the American Academy of Orthopaedic Surgeons classification, were 1 segmental, 14 cavitary, and 12 combined cavity and segmental. Twenty-two (82%) of the reconstructions were classified as adequate and five (18%) as inadequate based on the operative report and radiographic assessment, including anteroposterior, oblique, and lateral views. Reconstructions were considered adequate if an appropriate sized ring had been used in accordance with the recommendations of the authors (contact on host pelvic bone cranially, posteriorly, and inferomedially). Radiographic evaluation revealed acetabular component migration of more than 2 mm in 12 reconstructions (44%). Of these, cranial migration averaged 4 mm (range, 2-9 mm) in inadequate reconstructions, whereas it averaged only 2 mm (range, 1-4 mm) in adequate reconstructions. The incidence of migration in adequate reconstructions for segmental only and combined cavitary and segmental defects was 6 of 12 (50%), whereas it was 1 of 10 in reconstructions of cavitary deficiencies. Kaplan-Meier survivorship analysis revealed a 79.6% probability of survival at 10 years with revision as the endpoint for failure. It is concluded that durability of the reconstruction can be expected if support of the metallic reinforcement device is provided by host-bone. Segmental and combined deficiencies may require additional internal fixation by plates and screws.