Synergy between vitamin E and D-sorbitol in enhancing oxidation stability of highly crosslinked ultrahigh molecular weight polyethylene.

Oxidative stability of radiation crosslinked ultrahigh molecular weight polyethylene (UHMWPE) artificial joints is significantly improved by vitamin E (VE), but there is a dilemma that VE hinders crosslinking and thus jeopardizes the wear of UHMWPE. In this effort, we proposed an efficient strategy to stabilize UHMWPE under limited antioxidant contents, where VE and D-sorbitol (DS) were used as the primary antioxidant and the secondary antioxidant respectively. For non-irradiated blends with fixed antioxidant contents, oxidative stability accessed by oxidation induction time (OIT) of VE/DS/UHMWPE blends was superior to that of VE/UHMWPE blends, while DS/UHMWPE blends showed no increase in OIT. The cooperation between DS and VE exhibited a synergistic effect on enhancing the oxidative stability of UHMWPE. Interestingly, the irradiated VE/DS/UHMWPE blends showed comparable OIT but a significantly higher crosslink density than the irradiated VE/UHMWPE blends. The crystallinity, melting point, and in vitro biocompatibility of the blends were not affected by VE and DS. The quantitative relationships of mechanical properties, oxidation stability, crystallinity and crosslink density were established to unveil the correlation of these key factors. The overall properties of VE/UHMWPE and VE/DS/UHMWPE blends were compared to elucidate the superiority of the antioxidant compounding strategy. These findings provide a paradigm to break the trade-off between oxidative stability, crosslink density and mechanical properties, which is constructive to develop UHMWPE bearings with upgraded performance for total joint replacements. STATEMENT OF SIGNIFICANCE: VE-stabilized UHMWPE is the most commonly used material in total joint replacements at present. However, oxidation and wear resistance of VE/UHMWPE implants cannot be unified since VE reduces the efficiency of radiation crosslinking. It limits the use of VE. Herein, we proposed a compounding stabilization by the synergy between VE and DS. The antioxidation capability of VE was revived by DS, thus enhancing the oxidation stability of unirradiated UHMWPE. The irradiated VE/DS/UHMWPE exhibited similar oxidation stability but higher crosslink density than irradiated VE/UHMWPE, which is beneficial to combat wear of UHMWPE and to inhibit the occurrence of osteolysis. This synergistic antioxidation strategy endows the UHMWPE joint material with good overall performance, which is of clinical significance.

[Epidemiology Study and Risk Factors Analysis of Hyperuricemia in Tibetan Monks of Sichuan Province].

OBJECTIVE: To investigate the prevalence and risk factors of hyperuricemia (HUA) in Tibetan monks of Sichuan province. METHODS: 755 adult Tibetan monks (more than 18 years old) in Ganzi Tibetan Autonomous Prefecture of Sichuan Province were included in this study for health examination. Residents of Kangding City who received health examination were selected as controls. We measured the height, body mass, waist circumference, hip circumference, blood pressure and detected liver and renal function, serum lipid and blood routine exam. Then HUA prevalence in different genders and ages, and risk factors of HUA were analyzed. RESULTS: The serum uric acid (SUA) level of Tibetan monks was (318. 03±107. 70) µmol/L with the total HUA prevalence of 21. 46%. The prevalence of male was higher than that of female (25. 44% vs. 19. 02%, P<0. 05). The overall HUA prevalence of residents in Kangding City was 30. 70%, which was higher than that of the monks (P<0. 01). Prevalence of HUA in male monks was lower than the entire male population (25. 44% vs. 41. 65%) and male Tibetan ones (25. 44% vs. 32. 23%) in Kangding city. Among female population, however, we found that the HUA prevalence of monk (19. 02%) was higher than that of overall female population (14. 07%) and Tibetan residents (14. 72%) in Kangding (P<0. 05). Peak prevalence of HUA in Tibetan monks was between 30 and 40 years old. Gender, waist circumference, waist-to-height ratio (WHtR), fasting plasma glucose (FPG), serum creatinine (SCr), hemoglobin (Hb) levels and the consumption of meat were all independent risk factors for the occurrence of HUA in Tibetan monks according to Logistic regression analysis. CONCLUSION: The prevalence of HUA in male Tibetan monks is lower than that of local urban Tibetan population, but the result in female monks is opposite. Gender, waist circumference, WHtR, FPG, SCr, Hb levels and the consumption of meat were all independent risk factors for HUA.