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Radiostereometric analysis and clinical outcomes of a novel reverse total hip system at two years

Thomas R. Turgeon

David R. Hedden

Eric R. Bohm

Colin D. Burnell


Instability is a common cause of failure after total hip arthroplasty. A novel reverse total hip has been developed, with a femoral cup and acetabular ball, creating enhanced mechanical stability. The purpose of this study was to assess the implant fixation using radiostereometric analysis (RSA), and the clinical safety and efficacy of this novel design.

Despite the success of total hip arthroplasty (THA), instability continues to be a concern for surgeons and patients alike. Registry data suggest revision for instability to be the most common reason for revision in the first year and in the top two reasons for revision long-term for primary hip arthroplasties, demonstrating that this continues to be an area for ongoing need for improvement in joint arthroplasty care. While the use of increased femoral head diameter implants does demonstrate an improvement in stability, other currently available implant strategies to improve stability such as constrained liners and dual-mobility articulations are generally not favoured in the routine primary setting due to some drawbacks around their use.

Radiostereometric analysis demonstrates excellent fixation with a predicted low risk of revision at ten years of this novel reverse total hip system.

Clinical outcomes were consistent with safe and effective hip arthroplasty prostheses.

Reverse geometry articulations of the shoulder have been used with the articulation sphere mounted to the axial skeleton with a cup articulation mounted to the limb. These have seen increased use and success in recent years. A novel design of a reverse geometry THA has been created that uses this same principal. The benefits of the design are that load forces are maintained perpendicular to the polyethylene-lined cup throughout the entire flexion arc, resulting in stability that is far less dependent on the positioning of the acetabular and femoral components. The novel implant system had undergone comprehensive biomechanical and cadaveric testing, meeting or exceeding published standards. With the modifications to the mechanics of the THA, and the higher loads seen in the hip than in the shoulder, formal assessment of this novel device was undertaken in a multiphase clinical study. The first phase was initiated to characterize and assess the fixation stability of the femoral component and acetabular component with screw augmentation using radiostereometric analysis (RSA), as well as the clinical outcomes to ensure the safe introduction of this technology into hip arthroplasty.

Bone Jt Open 2023;4(5):385–392.

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