Abstract
Wear debris in total hip arthroplasty is one of the main causes of loosening and failure, and the optimal acetabular fixation for primary total hip arthroplasty is still controversial because there is no significant difference between cemented and uncemented types for long-term clinical and functional outcome. To assess and predict, from a theoretical viewpoint, the risk of wear with two types of polyethylene liners, cemented and uncemented, a simulation using the finite element (FE) method was carried out. The risk of wear was analyzed according to different variables: the polyethylene acetabular component’s position with respect to the center of rotation of the hip; the thickness of the polyethylene insert; the material of the femoral head; and the relationship of the cervical–diaphyseal morphology of the proximal end of the femur to the restoration of the femoral offset. In all 72 simulations studied, a difference was observed in favour of a cemented solution with respect to the risk of wear. With regard to the other variables, the acetabular fixation, the thickness of the polyethylene, and the acetabular component positioning were statistically significant. The highest values for the risk of wear corresponded to a smaller thickness (5.3 mm), and super-lateral positioning at 25 mm reached the highest value of the von Mises stress. According to our results, for the reconstruction of the acetabular side, a cemented insert with a thickness of at least 5 mm should be used at the center of rotation.
Highlights
The purpose of this study was (1) to evaluate, based on finite element analysis (FEA), the performance of the cemented and uncemented fixation of the polyethylene in order to determine the risk of wear according to different variables, both surgeon-dependent and surgeon-independent, during simulated gait and (2) to define which variables could minimize the risk of wear in
Other recent studies have developed an analysis method using an analytical model of contact pressure as a predictor of risk of wear [26], we believe that modeling many different variables using FEA provides a more reliable order-of-magnitude estimation
Our results clearly indicate that cemented fixation of the acetabular component offers the lowest risk of wear, with a statistically significant result
Summary
On basis of data from 2000 to 2014, the frequency of THAs in the United States is projected to grow to 635,000 procedures per year by 2030 [2]. Since THAs were introduced, there has been a steady improvement in the associated technology and surgical procedure, leading to better implant survivorship [3]. The true revolution in hip surgery was introduced by Professor Sir John Charnley with his low-friction cemented polyethylene liners [4]. Initial clinical results were excellent for 10 years, but extended follow-up revealed increasing rates of failure, mostly caused by implant designs and cementing techniques [5,6]. Some hip arthroplasty registers have shown inferior survival of uncemented cups [8]
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