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Short-Term Results with a Constrained Acetabular Liner in Patients at High Risk of Dislocation after Primary Total Hip Arthroplasty

Background Dislocation following primary total hip arthroplasty (THA) is a complication with an incidence of 2%-5%. This study examines the clinical and radiological outcome of a constrained acetabular implant used in primary THA in high-risk patients to prevent dislocation. Methods 54 patients with 55 constrained implants for primary THA were reviewed clinically and radiologically. Oxford, Harris Hip and Charlson scores were recorded. Results 54 patients, with an average age of 83.2 years, were followed up at a mean of 44.9 (20-74) months. 38 had an hydroxyapatite- (HA) coated acetabular shell with a constrained insert and 17 had a cemented constrained implant. The median Charlson score at surgery was 5 (4-10). There were significant improvements in Oxford, Harris hip pain and function scores and Charnley pain after surgery. 2 patients had radiolucent lines on the most recent radiograph. Neither was symptomatic and the acetabular components had not migrated. 3 patients developed postoperative infection, 1 deep requiring a 2-stage revision. Of the 29 patients who died, 1 required revision 2 months following surgery for dislocation of the constrained liner. This patient died 26 months later from unrelated causes having had no further complications from her surgery. There have been no further revisions or reoperations for dislocation in any of the other cases. Conclusions The use of a constrained acetabular liner at primary THA in high risk patients for dislocation can successfully prevent this complication without increasing component loosening. In this series of 55 constrained implants we have a postoperative dislocation rate of 1.8%.