Review Question - QID 4556

Wear rates of highly cross-linked UHMW polyethylene liners are independent of femoral head size between 22 and 46 mm in diameter.

While the wear rates of old polyethylene liners increased with increasing femoral head size, wear rates of the new highly cross-linked UHMW polyethylene liners have shown to be independent of head size. This is extremely advantageous, as increasing the femoral head size improves range of motion and increases jump distance, thereby decreasing dislocation rates.

Geller et al. report a prospective series of 42 patients that had a total hip arthroplasty with a highly cross-linked UHMW polyethylene liner and a femoral head >32 mm in diameter. After three years, there were no cases of osteolysis or failure due to aseptic loosening.

Muratoglu et al. studied the wear rates of several polyethylene liners with varying femoral head sizes. In the highly cross-linked UHMW polyethylene group, wear rates were independent of femoral head size.

Illustration A shows how increasing femoral head size increases the jump distance required for dislocation.

Incorrect Answers:
Answer 1: Increasing femoral head size decreases the risk of dislocation.
Answer 2: Increasing femoral head size increases range of motion.
Answer 3: Increasing femoral head size has not been shown to affect rates of osteolysis.
Answer 5: Increasing femoral head size has not been shown to increase the rate of periprosthetic fracture.