Finite Element Analysis of Stress Distribution in Flat and Elevated-Rim Polyethylene Acetabular Liners

Abstract

Unlike in cemented total hip arthroplasty (THA), several types of polyethylene liners can be used in cementless THA. Selection of the appropriate polyethylene liner affects the long-term stability after THA. 1,2) One of the main causes for revision surgery is postoperative dislocation, and the use of elevated polyethylene liners can effectively correct the inclination of metal cups, thereby preventing future dislocations. In cementless THA revision, there are some cases where the metal cup has no looseness, but the polyethylene liner is worn down and progressive osteolysis is seen. Significant malalignment of the metal cup requires removal of the metal cup, adjustment of the angle, and reinstallation. However, in cases of mild malalignment of the metal cup, the polyethylene insert may be changed from flat to elevated, with the metal cup preserved, to reduce polyethylene wear and prevent postoperative dislocation; this procedure is also less invasive for patients. 3-5) Nevertheless, no studies have compared flat and elevated-rim polyethylene liners in terms of stress distributions on the bearing surface of the liners. Our hypothesis was that the high stress area on the bearing surface would decrease when an elevated-rim polyethylene liner is used rather than a flat liner. By identifying the differences in stress distributions of the two types of liners, it may be possible to determine whether the elevated-rim liner is useful for reducing polyethylene wear. Furthermore, this could reveal other valuable practices for the use of elevated-rim liners.

Average 22-Year Results of Total Hip Arthroplasty Using Harris-Galante Prosthesis in Patients under 50 Years

“… 27) In addition, we speculate that the liner rim elevated over the margin of the acetabular cup might increase the risk of impingement with the stem trunnion damaging the locking mechanism, particularly in young, active Asian men with a cultural habit of squatting. 28) …”

Studies on Stress Analysis of Hip Prosthesis Implant

“…Furthermore, stainless steel has a modulus of roughly 200 GPa, which is significantly more than bone [16] having a modulus in the range of 11-20 GPa. Materials and their properties considered in this study are [21], [22]:…”

“…The design and assembly are done in the Fusion 360 software. Acetabular shell has an outside diameter of 52 mm and an inside diameter of 38 mm, an outer diameter of both flat and elevated liner is considered as 28 mm and outer diameter as 38 mm, the elevation of the elevated liner is kept as 10° [21]. The diameter of the femoral head is 28 mm, and the length of the femoral stem is taken as 120 mm [22].…”

“…So, different assemblies were done by changing the neck angle by 120°, 130°, and 140° [22]. Dimensions for the design are taken from [21]. The assembly file is then exported into .iges format for further analysis.…”

Comparative Finite Element Analysis of Osseointegration System in Trans-Radial Amputation: A Proposal of New Design

“…The average intramedullary canal diameter of the humerus is 14.5 mm(range : 9.4 ~ 20.5 mm) 9 , while the average diameter of the medullary cavity of the distal shaft of the radius is 6.7 mm(range : 6.1 ~ 7.3 mm) and the minimum diameter of the ulna medullary cavity is 4.2 mm(range : 2 ~ 6.7 mm). 10,11 In a review of the literature, no biomechanical study about osseointegrated implants for the trans-radial amputee was found. Because major upper-extremity amputees account for only 8% of the 1.5 million individuals living with limb loss 3 and upper-extremity loss does not affect weight-bearing, 11 therefore, the importance of upper-extremity amputation is lowered.…”