X-alt™ crosslinking parameters provide an optimized balance between wear reduction and material strength.^{7 9 10 24} Lower wear means less chance for particle-induced osteolysis and subsequent implant loosening.

Melt-annealed for consistent material properties over time.²⁴ If not removed, free radicals can bond with oxygen, causing the material to degrade. The annealing step removes free radicals, providing stability against oxidation.¹¹

Larger diameter heads increase range of motion and head “jump distance”, enhancing joint stability and helping to avoid dislocation.^{18 19 20 21 25}

Balancing Wear Reduction and Material Integrity

The goal of crosslinking is to reduce wear compared to standard UHMWPE. However, too much crosslinking can affect other properties of the material. X-alt is irradiated to 7.5 Mrad, the “point of diminishing returns”, where increasing the dose no longer provides a steep reduction in wear rate. Thus, X-alt strikes an important balance between minimizing wear and maintaining material integrity.

Balancing Larger Heads and Liner Thickness

The low wear of highly crosslinked polyethylene has driven some manufacturers to liner designs that are very thin. There have been reports of failure of these thin liners since their introduction. A paper in JBJS reports on four cases of these failures—all had a thickness at the locking mechanism less than 4 mm. ²³ The X-alt system includes larger heads, but also maintains a thickness of at least 4.8 mm at the dome.