Prediction of Bone Damage Formation in Resurfacing Hip Arthroplasty

Resurfacing Hip Arthroplasty (RHA) is a hip replacement method that is widely known nowadays. However, the complication on femoral bone fracture often happens in this hip replacement method which associated with the implant positioning. The objective of this study is to predict the damage formation on the bone which resulting from the RHA pin malposition. Finite element analysis was conducted in order to predict the damage formation on the bone model based on the computed tomography (CT) image of a patient. A 3D inhomogeneous bone model was developed from a 47 year old patient with an osteoarthritis disease located on the left femur. The material used for the RHA implant model is cobalt chromium and the implant is then being inserted into the femoral bone. Straight implant position with angle 130° was selected as a reference in the analysis while another three position of varus (> 130°) and valgus (<130°) were selected and known as the pin malposition. The simulation was conducted on each of the selected angles in order to predict the damage formation towards the bone model. The damage formation obtained was from the results of elements failure which occurred after applying the load. Physiological loading of a human which focusing on the normal walking condition was selected as the loading and boundary condition in this study. The femoral bone model experienced the highest damage formation when the implant located at the varus position while reduced significantly when the implant placed at the valgus position.

Rehabilitation after resurfacing hip arthroplasty: cost-utility analysis alongside a randomized controlled trial

Objective: To assess the costs, effects, and cost-utility of an accelerated physiotherapy programme versus a standard physiotherapy programme following resurfacing hip arthroplasty. Design: A cost-utility analysis alongside a randomized controlled trial. Setting: A UK National Health Service hospital and patients’ homes. Subjects: A total of 80 male resurfacing hip arthroplasty patients randomized post procedure to one of the two programmes. Interventions: The accelerated physiotherapy programme commenced in hospital with patients being fully weight bearing, without hip precautions, and following a range of exercises facilitating gait re-education, balance, and lower limb strength. Standard physiotherapy commenced in hospital, but hip precautions were used and exercises were only partially weight bearing. In both groups, patients continued with their exercises at home for an eight-week period. Main measures: Data on healthcare contacts were collected from patients to 12 months and costed using unit costs from national sources. Information was also collected on patients’ costs. Health-related quality of life was measured using the EuroQol EQ-5D questionnaire and used to estimate quality-adjusted life years (QALYs) to 12 months. Mean costs and QALYs for each trial arm were compared. Results: On average, the accelerated physiotherapy programme was less expensive (mean cost difference −£200; 95% confidence interval: −£656 to £255) and more effective (mean QALY difference 0.13; 95% confidence interval: 0.05 to 0.21) than standard physiotherapy and had a high probability of being cost-effective. Conclusion: From the National Health Service perspective, an accelerated physiotherapy programme for male patients undergoing revision of total hip arthroplasty (RHA) is very likely to be cost-effective when compared to a standard physiotherapy programme.

Changes in periacetabular bone mineral density five years after resurfacing hip arthroplasty versus conventional total hip arthroplasty

Introduction: We studied whether acetabular bone mineral density (BMD) is better preserved after resurfacing hip arthroplasty (RHA) versus small diameter metal-on-metal total hip arthroplasty (THA). Methods: This randomised controlled trial included 82 patients. BMD was measured in 5 periprosthetic regions of interest (ROI) with dual-energy absorptiometry (DEXA) preoperatively, at 3 and 6 months, 1, 2, 3 and 5 years postoperative. 34 RHA and 26 THA had a complete 5 years follow-up. 1 RHA and 1 THA were revised due to pseudotumour formation, 2 THA were revised because of recurrent dislocations and 1 RHA for avascular necrosis. Results: Overall an initial decrease in BMD was observed for both implants, stabilising after 2 years. 5 years after RHA a BMD change of +1% in upper cranial, –4% ( p < 0.01) in cranial, –8% ( p < 0.01) in craniomedial, –7% ( p < 0.01) in medial and +4% in caudal ROI compared to baseline values was seen. 5 years after THA a BMD change of –3% ( p = 0.01), –13% ( p < 0.01), –21% ( p < 0.01), –11% ( p < 0.01) and –2% for each respective ROI. The observed BMD decrease in different regions was structurally favouring the RHA-cup, with significantly higher levels in the cranial and craniomedial ROI. Conclusion: Acetabular BMD is better preserved behind a rigid press-fit convex cup in RHA compared to a titanium threaded cup in conventional THA in the cranial and craniomedial ROI. Despite of a theoretical higher stress-shielding behind the stiff acetabular component in RHA, compared to the more elastic threaded titanium THA-cup, bone depletion behind the RHA component does not seem to be of major concern. Registration: EudraCT (2006-005610-12)