Background
We report on the midterm linear and volumetric wear of highly cross-linked polyethylene (HXLPE) and survivorship of two prospective young THA cohorts that differed by the size of ceramic femoral head used: 28 vs. 32 millimeters.
Methods
We prospectively analyzed 220 consecutive primary THAs in patients ≤50 years who received a cementless THA with a ceramic femoral head on HXLPE liner (C-HXLPE). There were 101 patients (46%) with 28mm heads and 119 patients (54%) who received 32mm heads at a mean follow-up of 5.5 years (range 60–109 months). Wear was calculated using Martell Software.
Results
The 28mm C-HXLPE cohort demonstrated average linear and volumetric wear of 0.020 mm/year (SD 0.074, 95% CI [0.003, 0.037]) and 18.775 mm3/yr (SD 21.743, 95% CI [13.773, 23.778]) compared to 0.032 mm/yr (SD 0.087, 95% CI [0.013, 0.050]) and 29.847 mm3/yr (SD 35.441, 95% CI [22.294, 37.401]) in the 32mm C-HXLPE group. Subgroup analysis by gender and head size discovered significantly greater wear in females with 32mm compared to 28mm heads in both linear (0.01, 95% CI [−0.014, 0.033] vs. 0.048, 95% CI [0.022, 0.074] mm/y, p=0.004) and volumetric wear (14.11, 95% CI [8.957, 19.271] vs. 29.71, 95% CI [17.584, 41.840] mm3/yr, p=0.009). We found a 96% (95% CI [92.30%, 97.94%]) survivorship by Kaplan-Meier analysis at minimum 5-years with no failures due to osteolysis.
Conclusions
Ceramic-on-HXLPE demonstrates extremely low wear properties in young patients at midterm follow-up. We identified a gender-dependent difference in wear based on head size, with 32mm heads being associated with increased wear in females.