Lever-Out Resistance of Constrained Hip Liners is Sensitive to Changes in Opening Radius and Liner Design.

The constrained liner is an important tool for the treatment of recurrent dislocation, which continues to represent an important challenge in total hip arthroplasty. In constrained liner design, there is a tradeoff between dislocation resistance and range of motion. However, studies investigating their sensitivity to design parameters are scant. Given the relatively high rate of failure of constrained devices, this information is critical to improving their design. This study aimed to use finite element analysis to explore the sensitivity of constrained liner-dislocation resistance to variations in liner opening radius, for two different constraining design features found in contemporary devices. Results showed that a smaller opening radius leads to increased lever-out moment. It was also observed that in liners with localized constraint, lever-out resistance is more sensitive to changes in opening radius than those with circumferential constraint. (c) 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 37:1590-1595, 2019.