Standard and special liner in primary hip arthroplasty : Current study and survey results from the German Arthroplasty Registry (EPRD)

Abstract

Instability constitutes the main reason for revision hip arthroplasties. Modified polyethylene liners are designed to improve the stability of ahip replacement. In July 2022 The Bone & Joint Journal published astudy with data of the German Arthroplasty Registry (EPRD). The study investigated mechanical failure of standard and modified liner designs in primary, cementless total hip arthroplasty. Following the study, the EPRD conducted asurvey of German clinics to research the utilization of lipped liners in primary total hip replacement. The liner study included 151,096 primary, elective, cementless total hip arthroplasties. Data from November 2012 to November 2020 were obtained from the EPRD. Standard polyethylene liners were compared with lipped, angulated, offset and angulated/offset inlays. Cumulative incidences for endpoint revision due to mechanical complication were calculated with acompeting risk analysis. The influence of other variables was investigated with amultivariate Cox regression. In the following online survey, 237 out of 789 hospitals completed aform. In our analysis, only offset liners were, compared to standard liners, associated with areduced risk of mechanical failure in ashort to medium follow up. However, the resultant joint reaction force is increased with offset liners due to the lateralization of the hip center of rotation. Thus, the long-term performance of offset liners needs to be observed. Our survey indicated that lipped liners were implanted more often if the posterior approach was used. Moreover, lipped liners were mostly positioned with the elevated rim in the biomechanically less optimal posterior-superior quadrant. To improve stability it is suggested to position the elevated rim in the posterior-inferior quadrant.