Abstract
Introduction: Several techniques have been described for revision of acetabulum associated with severe superior bony defects. An Oblong cup inserted without bone cement has the advantage of restoration of the centre of hip rotation and maintenance of bone stock. The aim of this study was to analyse the medium-term results of acetabular revision using Oblong cup for severe superior bony defects.
Methods: Thirty-five acetabular revisions using porous coated Oblong cups (S-Rom, Depuy) in 34 patients were performed by the senior author between 1998–2001. All patients were followed-up clinically and thirty-one hips were analysed radiologically for a mean duration of 39.6 months (range 18 to 60). The clinical assessment was performed using Harris hip score and subjective patient’s satisfaction. The acetabular defects were classified according to the method described by Paprosky et al. The position of the acetabular implant, restoration of the centre of hip rotation and the extent of osseo-integration of the acetabular shell were assessed in the post-operative radiographs.
Results: The mean Harris hip score has improved from a preoperative value of 40.6 to 69.4 post-operatively. According to the Leprosy’s method, two acetabula were classified as type 2B, 12 as type 3A and 17 as 3B. The post-operative radiographs showed a mean abduction angle of the Oblong cups of 54.2 degrees (range 40–80). Osseointegration was achieved in 29(94%) of cups. Three cups showed early migration, of which two eventually stabilised and osseointegrated by 12 months. The centre of rotation of hip improved from a mean lateral migration of 8.3 mm and superior migration of 23.5 mm in the pre-operative radiographs to 2.8 mm and 4.3 mm respectively post-operatively.
Discussion: Acetabular revision using porous coated oblong cup for severe superior acetabular defects provides satisfactory medium-term results with predictable restoration of hip centre of rotation.
Correspondence should be addressed to The Secretary, BHS, c/o BOA, The Royal College of Surgeons, 35–43 Lincoln’s Inn Fields, London WC2A 3PE.
