Abstract
Management of massive acetabular defects in revision hip arthroplasty is challenging. The current generation reconstruction cages in combination with either morcellised or structural allograft bone have given promising results. However, a significant number fail due to failure of biological fixation of the cage, resulting in fatigue fracture of the cage. Trabecular metal has the potential to enhance biologic fixation. The purpose of this paper is to introduce this new surgical technique of combining a cage with a shell of trabecular metal and present the early results.
Fourteen patients (mean age 63, range 45 to 82 years) with massive contained defects underwent revision arthroplasty with a cup cage by the senior author (AEG). Complications, functional status (WOMAC, Oxford hip score and SF36) and radiographs were assessed. Post operative radiographs were assessed for evidence of construct migration, resorption and or remodelling of allograft bone. Remodelling was defined by the presence of bony trabeculae crossing the allograft host junction. Lucent lines were assessed. Allograft resorption was defined as loss of graft height on comparable radiographic views. An implant was defined as loose if there was evidence of construct migration or component fracture.
The mean follow up was 21 months (range one to 38 months). Complications included one death and one recurrent dislocation requiring revision to a capture liner. Average pre and post operative WOMAC scores were 61 and 17 points respectively. Oxford hip scores were an average of 45 pre-operatively and 24 post-operatively. SF-36 averaged 351 pre-op and 601 post-op. All implants were stable. Minor radiolucent lines were found around the inferior flange of the cage in six patients. Minor graft resorption occurred in two patients. All but one showed graft remodelling. All patients were ambulant.
The early results of this new technique for treating a complex problem show excellent rates of initial implant stability and bone graft remodelling.
Correspondence should be addressed to Associate Professor N. Susan Stott at Orthopaedic Department, Starship Children’s Hospital, Private Bag 92024, Auckland, New Zealand
