Abstract
Introduction: The objectives of this study were to evaluate acetabular bone deficiency in revision THA with a simple classification on the anteroposterior pelvis radiograph and correlate the results of cementless hemispherical porous coated cup and cancellous bone graft reconstruction.
Methods: 70 acetabular revisions reconstructed employing large ‘jumbo’ porous coated cups with cancellous allo-grafting were evaluated at a mean follow-up of 5 years (range 2 – 10 years). During this time period 7 additional acetabular reconstructions required impaction grafting, cage reinforcement and cemented cups. Pre- and postoperative measurements of acetabular bone loss and the position of the revision component were performed with respect to a previously described triangle defining the placement and size of an idealcup. Impaction bone allo-grafting techniques were employed to fill defects. A minimum of 40% implant contact to host bone, especially in the weight-bearing dome region was attained in all cases and a minimum of 2 screws supplemented fixation to the ilium. Clinical evaluation comprised the HSS score and a patient assessment questionnaire (PAQ). Radiographically, cups were examined for filling of defects, ingrowth, graft consolidation, and stability.
Results: The mean HSS score improved from 18 to 33 out of a maximum of 40. The mean superior bone defect was 18 mm (range 10 – 25mm) and the mean medial bone defect was 7 mm (range 0 – 22mm). All the cement-less acetabular components were bone ingrown with the exception of one stable fibrous union. Allograft incorporation occurred at a mean of 7 months after surgery. Neither the status of Kohler’s line nor the Paprosky class correlated with eventual radiographic or clinical results.
Discussion: We present a simple method of evaluation of acetabular bone deficiency on the A-P pelvis radiograph employing a triangle that locates the ideal center of rotation of the hip. Superior bone loss upto 25 mm and medial migration as much as 22 mm has been successfully reconstructed employing impacted, cancellous allograft, large porous coated hemispherical Cementless acetabular components and screw fixation with excellent outcomes at intermediate-follow-up. Larger defects necessitate complex reinforced cage reconstruction.
The abstracts were prepared by Nico Verdonschot. Correspondence should be addressed to him at Orthopaedic Research Laboratory, University Medical Centre, PO Box 9101, 6500 HB Nijmegen, The Netherlands.
