Comparison of Polyethylene Wear before and after Hip Revision with Liner Exchange Fixed with the Original Locking Mechanism

Isolated Liner Exchange and Bone Grafting for the Management of Periacetabular Osteolysis in Well-Fixed Cups with an Intact Locking Mechanism at Short-Term to Medium-Term Follow-Up: A Systematic Review

Background: Polyethylene liner exchange and bone grafting is an effective surgical option for the management of periacetabular osteolysis following total hip arthroplasty with well-fixed cups and intact liner locking mechanisms. Purpose: We aimed to evaluate the revision-free survivorship and radiographic lesion progression after polyethylene liner exchange and bone grafting is performed for periacetabular osteolysis. Methods: A systematic review of the literature was performed. We queried Medline, EMBASE, and Cochrane Library for articles published from January 1999 to January 2023 using the following keywords: "osteolysis" AND "well-fixed," "osteolysis" AND "retro-acetabular," "bone graft" AND ("retention" OR "retained" OR "stable") AND "cup," and "uncemented liner" AND "well-fixed." Results: Of 596 articles found, 9 articles were selected for final inclusion (227 cases, mean follow-up time 43.6 months). The overall cup revision rate after liner exchange was 6.6% (15 hips) due to progressive osteolysis (5 hips), aseptic loosening of the acetabular component (5 hips), dislocation (4 hips), and periprosthetic infection (1 hip). There was either radiographic resolution or regression of periacetabular osteolysis in all reported cases that provided measurements (52 hips) except 1 (1.9%) requiring revision. All studies reporting clinical outcomes indicated improved pain and functional scores. Conclusion: This systematic review found that isolated liner exchange with bone grafting for the management of periacetabular osteolysis was associated with a high revision-free survival rate (93.4%) and minimal radiographic progression (1.9%) of osteolytic lesions at short-term to medium-term follow-up. Liner exchange with bone grafting is recommended for the management of large periacetabular osteolytic lesions (> 450 mm2) in well-fixed acetabular cups. We encourage future studies to develop a grading scale for lesions to guide clinical management and risk stratification for patients.

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

Backgroud

No study has compared flat and elevated-rim polyethylene liners in terms of stress distribution on the bearing surface. The purpose of this study was to investigate the difference in stress distribution between flat and elevated-rim polyethylene liners.

Methods

A stress analysis was performed by using the 3-dimensional finite element method. The cup was placed at an open angle of 20°, the flat liner and the liner with a 10° elevation was placed at inclination angles of 80°, 70°, and 60°.

Results

Compared with the 60° flat liner, the 80° and 70° flat liners showed higher stress at the liner edge. In the elevated-rim liner, the stress was high at the liner edge along the cup edge. When the von Mises equivalent stress was applied to each element of the liner, the high stress area (volume) was the largest for the 80° flat liner, second largest for the 80° elevated-rim liner, and third largest for the 70° flat liner. The average contact pressure also followed the same order.

Conclusions

Elevated-rim liners affect the stress distribution by increasing the area of contact. However, since elevated-rim liners exhibit high stress at the cup edge, they are likely to result in new problems including liner failure. These findings could aid surgeons in the selection of liners and determination of revision methods such as isolated liner exchange vs. acetabular cup revision for a well-fixed metal cup with a higher inclination angle in revision total hip arthroplasty.