Long-term Results of the Thrust Plate Prosthesis, 21-year Follow-up: A Case Report and Literature Review

Introduction: The thrust plate prosthesis (TPP) is a type of cementless hip replacement. Aimed to preserve femoral diaphyseal bone, it was favored by some orthopedic surgeons in younger patients as they could potentially undergo multiple revision arthroplasties during their lifetime. Of particular note, the preserved diaphyseal bone allows for the implantation of a subsequent primary total hip arthroplasty (THA). Case Report: We reported on a 64-year-old male patient who underwent thrust plate prosthesis (TPP) implantation 21 years ago (1999) for the treatment of primary osteoarthritis (OA) of the right hip joint. At 21-year follow-up, he had not developed any post-operative complications, and he reported a SF12 score of 32 and Oxford hip score of 47/48. Conclusion: TPP proved to be successful clinically and radiologically, especially in the young patient. It loads directly to the cortex of the proximal femoral metaphysis as in a native hip joint. It is a bone preserving prosthesis which allows for good bone stock in the case of revision surgery that was a victim of commercial considerations. Keywords: Thrust plate prosthesis, thrust plate prosthesis, arthroplasty.

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.

Evaluation of Stress Shielding for Three Types of Implanted Femurs Based on Stress Distribution

This research investigates the stress distribution of the three types of implanted femurs using the finite element method analysis. The comparisons of the stress distribution between the implanted femursand the healthy femur were performed and the characteristics in the stress shielding of each casewere clarified. Since the load is transferred on the contact surface between the implant and the inner surface of the femur in the case of the total hip arthroplasty, the stress in the intertrochanteric zone (Gruen zone 7) become very small, and the phenomenon of the stress shielding is confirmed obviously. The stress distributions of the femurs afterthe resurfacing hiparthroplasty and the thrust plate prosthesis are about the same with that of the healthy femur, so, the possibility of the stress shielding is considered lower compared with the femur after the total hip arthroplasty. However, considering the stress concentration thatwill increase the risk of femoral fracture caused by the screws for the fixation of the implant in the thrust plate prosthesis, the resurfacing hiparthroplastymay beconcluded as the best method among these three types of implants to avoid stress shielding.