Acetabular UHMWPE survival and wear changes with different manufacturing techniques.

BACKGROUND: Polyethylene wear may be affected by the type of polyethylene resin, manufacturing technique, degree of thermal stabilization, and sterilization technique. QUESTIONS/PURPOSES: We therefore compared femoral head penetration into the PE and cup survival using the same cup system with different PE resins, manufacturing, and sterilization techniques.
METHODS: Our study group consisted of 1912 THAs performed using the same uncemented cup and identical 28-mm cobalt-chrome heads. The polyethylene varied as follows: Group 1 (94 cups), GUR 4150 resin, ram-extruded, sterilized in air, no barrier packaging; Group 2 (74 cups), same as Group 1 but sterilized in argon; Group 3 (75 cups), Himont 1900 resin, compression-molded bar stock, sterilized in argon, no barrier packaging; Group 4 (620 cups), same as Group 3 except with barrier packing; Group 5 (711 cups), GUR 1050 resin, compression-molded bar stock, sterilized in argon gas with barrier packaging; and Group 6 (338 cups), GUR 1050 resin, compression-molded bar stock, sterilized in argon with barrier packaging, irradiated with 50 kGy, heated below melting temperature, machined, and finally placed in nonbarrier packaging with gas plasma sterilization. Minimum followup was 2 years (average, 7 years; range, 2-17 years).
RESULTS: Femoral head penetration averaged 0.05 mm per year for Groups 5 and 6 and was substantially lower than for Groups 1 to 4. Cup survival was higher at seven years in Groups 3, 4, and 5, and at 10 years in group 4 when compared to groups 1, 2, and 3.
CONCLUSIONS: We observed lower FHP rates and higher cup survival with polyethylene machined from direct compression-molded bar stock, sterilized in argon gas, with barrier packaging. LEVEL OF EVIDENCE: Level III Therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.