POLYETHYLENE LINER PREPARATION FOR CEMENT FIXATION: OPTIMIZING THE STABILITY OF A POLYETHYLENE LINER-CEMENT INTERFACE

Abstract

This study assesses a method of optimizing the polyethylene-cement interface when cementing a constrained liner into a pre-existing acetabular shell. We tested several configurations of liner modification including random roughening, 2mm and 4mm wide grooves Statistical analysis showed that the grooved liners had significantly higher moment to failure than both the unmodified and roughened liners. There was no difference between the 2 and 4mm grooved liners.

The purpose of this study was to answer the question: what liner preparation will provide the most stable polyethylene – cement interface?

Two and 4mm circumferential grooves and meticulous cementing technique can significantly increase the strength of the polyethylene-cement interface.

All samples failed at the polyethylene – cement interface. Statistically significant differences were found between the following groups: unmodified vs. 2mm (p=0.005) and 4mm groove (p=0.012) and roughened vs. 4mm groove (p=0.011).

Modification of a constrained liner with circumferential grooves may improve the stability of the cement interface enough to make this a more reliable technique in revision hip surgery.

Polyethylene was machined into 50mm diameter liners. These were cemented using PMMA into aluminum acetabular shells ensuring a 3mm cement mantle. Lever-out testing was performed on four groups; no modification, random roughening, 2mm and 4mm grooves.

When an acetabular component is well fixed/positioned, the option of cementing a constrained liner into the fixed shell is an option. Experience has shown that the most common mode of failure in this technique is the polyethylene-cement interface.

Funding: This study was funded by the Division of Orthopedics, Department of Surgery, and the Department of Mechanical Engineering, University of Saskatchewan.