Patient Specific Component Alignment in Total Hip Arthroplasty

Appropriate component alignment is critical for reducing instability, maximising bearing performance and restoring native anatomy after Total Hip Replacement (THR). Due to the large variation in patient kinematics between functional activities, current technologies lack definition of what constitutes correct target alignment. Analysis of a large series of symptomatic THR patients confirm that apparently well-orientated components on standard radiographs can still fail due to functional component malalignment. Evidently, previously defined “safe zones” are not appropriate for all patients as they don’t consider the dynamic behaviour of the hip joint. The Optimized Positioning System TM (OPS TM ) comprises preoperative planning based on a patient-specific dynamic analysis, and patient-specific instrumentation for delivery of the target component alignment. This paper presents the application of OPS TM in three case studies.