Stable fixation of an ultra-short femoral neck-preserving hip prosthesis: a 5-year RSA, DXA, and clinical prospective outcome study of 48 patients.

BACKGROUND AND PURPOSE: We previously showed promising primary stability and preservation of bone stock with the ultra-short neck-loading hip implant in total hip arthroplasty (THA). The aim of this study was to evaluate clinical outcome, implant stability, and bone mineral density (BMD). METHODS: 50 patients were treated with the ultra-short neck Primoris hip implant at baseline and 48 were available for evaluation at 5-year follow-up. 5 different patient-reported outcome measures (PROMs) including hip-specific scores, disease-specific and generic quality of life outcome measures, and an activity score were used. Furthermore, implant stability using radiostereometric analysis (RSA) and assessment of periprosthetic BMD using dual-energy X-ray absorptiometry (DXA) were applied. RESULTS: By 1-year follow-up, all PROMs showed improvements and remained high at 5-year follow-up. After initial distal translation (subsidence) and negative rotation around the z-axis (varus tilt) the implant showed stable fixation at 5-year follow-up with no further migration beyond 12 months. In the regions of interest (ROI) 3 and 4, BMD remained stable. In ROI 2, further bone loss of 12% was found at 5-year follow-up. CONCLUSION: Clinical outcome including PROMs was satisfying throughout the 5-year follow-up period. The hip implant remains stable with both bone preservation and loss 5 years after surgery.

An Ultra-Short Femoral Neck-Preserving Hip Prosthesis: A 2-Year Follow-up Study with Radiostereometric Analysis and Dual X-Ray Absorptiometry in a Stepwise Introduction.

BACKGROUND: Total hip arthroplasty (THA) with a diaphyseal stem may risk bone loss. In order to save proximal bone stock in young patients with a high activity level and a long life expectancy, the interest in short stems has evolved. The purpose of this prospective observational cohort study was to evaluate the fixation of, and bone remodeling around, the Primoris femoral neck-preserving hip implant. METHODS: Fifty younger patients with end-stage osteoarthritis were managed with the Primoris hip implant. We evaluated bone mineral density (BMD) using dual x-ray absorptiometry (DXA) and implant migration using radiostereometric analysis (RSA). A region-of-interest (ROI) protocol for 4 ROIs was applied to assess BMD. The association between BMD and migration was evaluated to determine the fixation of the Primoris implant and bone remodeling in the proximal part of the femur. Follow-up evaluation was performed at regular intervals from day 1 (baseline) until 24 months after surgery. RESULTS: The major stem migrations were subsidence (Y axis; mean, 0.38 mm) at 6 weeks and varus tilt (rotation) (Z axis; mean, 0.93°) at 6 to 12 months. In ROI4 (the calcar area), a significant gain in bone was found with a mean difference of 4.1% (95% confidence interval [CI], 0.8% to 7.4%; p < 0.02) at 24 months postoperatively. Significant bone loss was found in ROI1 and ROI2, with a mean difference of -4.9% (95% CI, -7.4% to -2.4%; p = 0.0003) and -8.9% (95% CI, -11.5% to -6.2%; p = 0.0001), respectively. Linear regression and multivariate regression analysis showed a significant negative association between maximal total point motion and BMD (p = 0.02, R = 15%; and p < 0.05, R = 26%, respectively). CONCLUSIONS: The Primoris component showed satisfactory primary stability with promising results at the 24-month follow-up. DXA scans showed limited stress-shielding with the proximal loading pattern of the Primoris. Better bone quality was associated with less implant migration. LEVEL OF EVIDENCE: Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Bone remodelling of the proximal femur after total hip arthroplasty with 2 different hip implant designs: 15 years follow-up of the thrust plate prosthesis and the Bi-Metric stem.

INTRODUCTION: The thrust plate prosthesis (TPP) was introduced to preserve bone in patients undergoing total hip arthroplasty. We assessed the long-term results of hip arthroplasty in patients who received the TPP compared to a traditional intramedullary stem (Bi-Metric). METHODS: In this prospective observational cohort study, we evaluated bone mineral density (BMD) using dual-energy X-ray absorptiometry (DXA), radiological imaging and clinical outcome using Harris Hip Score (HHS). Twenty patients received the TPP (group A) and 18 patients received the Bi-Metric stem (group B). Baseline was the 1st postoperative day, and subsequent follow-up was performed at 6 months, 1, 2, 8, 12 and 15 years after surgery. A four regions of interest (ROI) protocol was developed to assess BMD. RESULTS: In ROI1, bone resorption was significantly higher for group A at 6 months with a mean difference of 10% (95% confidence interval [CI], 4-16; p = 0.003) and 8% (95% CI, 1-15; p = 0.03) at 8 years. Regarding ROI4, group A had a lesser decrease in general compared to group B. The radiological findings did not reveal any subsidence or detectable implant migration. HHS improved from 53 (23-69) to 93 (55-100) in group A and from 51 (24-72) to 94 (78-100) in group B. CONCLUSION: The TPP was not found to be inferior to the Bi-Metric stem regarding bone preservation. The decrease in BMD in ROI4 was greater in group B. Clinical and radiological results also revealed that the TPP was not inferior to the Bi-Metric stem.