{'fraction_non_alphanumeric': 0.03646144650328751, 'fraction_numerical': 0.03646144650328751, 'mean_word_length': 4.58, 'pattern_counts': {'":': 0, '<': 2, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
201 IN VIVO WEAR OF LARGE FEMORAL HEADS ON HIGHLY CROSS-LINKED POLYETHYLENE.

Introduction Highly cross-linked polyethylene has been shown in hip simulator studies to reduce wear by 80% to 90% when compared to conventional polyethylene. The goal of this study was to evaluate the in vivo wear of a highly cross-linked polyethylene against femoral head sizes larger than 32 mm. Materials and Methods Volumetric and linear wear rates were measured in two groups of patients with femoral heads larger than 32 mm. Thirteen hips received a highly cross-linked polyethylene liner and 13 hips received a conventional polyethylene liner. Volumetric and linear wear rates were measured on radiographs with use of a validated computer-assisted technique (Hip Analysis Suite, version 7.0). Results The highly cross-linked polyethylene had a mean volumetric and linear wear rate of 117.5 ± 103.8 mm3 and 0.15 ± 0.10 mm per year, respectively. The conventional polyethylene had a mean volumetric and linear wear rate of 375.7 ± 153.8 mm3 and 0.36 ± 0.16 mm per year, respectively. The volumetric and linear wear rates in the group with the highly cross-linked polyethylene liner were 69% (p < .0009) and 58% (p < .0007) lower, respectively. There was no significant difference in gender, age, weight, femoral head size, abduction angle, or UCLA activity score between the two groups. Discussion While hip simulator studies predict a 80% to 90% reduction in wear, the difference between the in vitro and in vivo results could be a result of bedding-in-effect and creep. These are promising initial results that will improve the long-term survival of surface and total hip arthroplasties.