A novel reverse total hip arthroplasty (RTHA) design has been developed with enhanced mechanical stability at extremes of motion in all planes by reversing the articulating surfaces using a femoral cup and acetabular ball. The purpose of this study was to assess the implant-bone fixation using radiostereometric analysis, assess the linear wear of the cross-linked polyethylene insert and monitor the clinical safety and efficacy of this novel design as a hip arthroplasty device. Twenty two subjects with end-stage osteoarthritis of the hip were enrolled at a single center in this regulator-approved investigational device trial. All patients underwent a RTHA utilizing at least 1 acetabular screw for augmented fixation with the Reverse Hip Replacement System. RSA markers were inserted into the innominate bone and proximal femur prior to implant insertion. Model-Based RSA was used to assess migration between the implants and bone and the polyethylene linear wear with assessments at six weeks (baseline), six, 12, 24 and 60 months from surgery. Patient reported outcome metrics were collected pre-operatively and at each post-operative visit including Oxford Hip Score-12, Harris Hip Score (HHS), European Quailty of Life (EQ-5D), HOOS and SF-36. Analysis was performed using one-sided and paired t-tests. The cohort consisted of 11 females and 11 males with mean age of 70.8 years and body mass index 31.3 kg/m2. Mean femoral subsidence from baseline at 6, 12, 24 and 60 months was 0.01±0.12mm, −0.00±0.19mm, −0.00±0.19mm and −0.06±0.21mm, all below the published critical threshold of 1.5mm (p The femoral and acetabular components both appeared well fixed at 5 years as assessed with RSA suggesting a low-risk of long-term aseptic loosening. Polyethylene linear wear was approaching the detection limit for assessment and within accepted limits. The results indicate acceptable radiographic safety and clinical efficacy of this novel reverse total hip arthroplasty design.
Turgeon et al. (Wed,) studied this question.