Comparing In Vivo Performance of Two Highly Cross-Linked Polyethylene Thermal Treatments: Remelting vs Annealing in Acetabular Liners.

BACKGROUND

The introduction of highly cross-linked polyethylene (HXLPE) acetabular liners has greatly improved the wear performance of metal-on-PE bearing surfaces used in total hip arthroplasty. Changing the sterilization environment and adding thermal treatments, such as remelting or annealing, were introduced to limit on-shelf and in vivo oxidation of cross-linked liners. This study compares the wear properties of the remelted A-CLASS (MicroPort) HXLPE liner to a sequentially annealed HXLPE.

METHODS

This retrospective study assessed linear and volumetric wear rates using Martell Hip Analysis Suite, and clinical performance through incidences of revision surgeries. A total of 80 remelted and 53 annealed liners were included in the wear analysis. All hips were reviewed for revisions.

RESULTS

There were no significant differences in steady-state linear or volumetric wear rates for remelted and annealed liners, 0.01 (-0.07 to 0.14) vs -0.01 (-0.11 to 0.1) mm/y (P = .28) and -1.03 (-30.99 to 45.43) vs -1.31 (-32.23 to 23.70) mm/y (P = .30), respectively. Both cohorts were below the 0.1 mm/y linear wear threshold. The wear rates for patients with femoral head sizes ≥36 mm were not significantly different than those with 32 and 28 mm femoral head sizes (P = .60). Similarly, wear rates for patients with an excessively vertical acetabular component (>50°) were not significantly different than those with standard acetabular component orientations (P = .97). No hips were revised due to liner-related complications.

CONCLUSION

The wear rates of the A-CLASS remelted HXLPE acetabular liner wear rates were comparable to those of a sequentially annealed HXLPE. Further long-term studies are required to ensure acceptable resistance to fatigue and in vivo oxidation.