Natural Polyphenols Enhance Stability of Crosslinked UHMWPE for Joint Implants

Background

Radiation-crosslinked UHMWPE has been used for joint implants since the 1990s. Postirradiation remelting enhances oxidative stability, but with some loss in strength and toughness. Vitamin E-stabilized crosslinked UHMWPE has shown improved strength and stability as compared with irradiated and remelted UHMWPE. With more active phenolic hydroxyl groups, natural polyphenols are widely used in the food and pharmaceutical industries as potent stabilizers and could be useful for oxidative stability in crosslinked UHMWPE.

Questions/purposes

We asked whether UHMWPE blended with polyphenols would (1) show higher oxidation resistance after radiation crosslinking; (2) preserve the mechanical properties of UHMWPE after accelerated aging; and (3) alter the wear resistance of radiation-crosslinked UHMWPE.

Methods

The polyphenols, gallic acid and dodecyl gallate, were blended with medical-grade UHMWPE followed by consolidation and electron beam irradiation at 100 kGy. Radiation-crosslinked virgin and vitamin E-blended UHMWPEs were used as reference materials. The UHMWPEs were aged at 120 °C in air with oxidation levels analyzed by infrared spectroscopy. Tensile (n = 5 per group) and impact (n = 3 per group) properties before and after aging as per ASTM F2003 were evaluated. The wear rates were examined by pin-on-disc testing (n = 3 per group). The data were reported as mean ± SDs. Statistical analysis was performed by using Student’s t-test for a two-tailed distribution with unequal variance for tensile and impact data obtained with n ≥ 3. A significant difference is defined with p < 0.05.

Results

The oxidation induction time of 100 kGy UHMWPE was prolonged to 144 hours with 0.05 wt% dodecyl gallate and 192 hours with 0.05 wt% gallic acid compared with 48 hours for 0.05 wt% vitamin E-blended UHMWPE. Accelerated aging of these polyphenol-blended UHMWPEs resulted in ultimate tensile strength of 50.4 ± 1.4 MPa and impact strength of 53 ± 5 kJ/m² for 100 kGy-irradiated UHMWPE with 0.05 wt% dodecyl gallate, for example, in comparison to 51.2 ± 0.7 MPa (p = 0.75) and 58 ± 5 kJ/m² (p = 0.29) before aging. The pin-on-disc wear rates of 100 kGy-irradiated UHMWPE with 0.05 wt% dodecyl gallate and 0.05 wt% gallic acid were 2.29 ± 0.31 and 1.65 ± 0.32 mg/million cycles, comparable to 1.68 ± 0.25 and 2.05 ± 0.22 mg/million cycles for 100 kGy-irradiated virgin and 0.05 wt% vitamin E-blended UHMWPE.

Conclusions

Based on the sample numbers tested in this study, polyphenols appear to effectively enhance the oxidation stability without altering the mechanical properties or pin-on-disc wear rate of radiation-crosslinked UHMWPE.

Clinical Relevance

Crosslinked UHMWPE with natural polyphenols with improved oxidative stability and low wear may find clinical application in joint implants.     

偏心髋臼旋转截骨术的生物力学机制及初步临床疗效

 目的 探讨偏心髋臼旋转截骨术治疗髋关节发育不良的生物力学机制及其初步临床疗效。方法 取6具经福尔马林防腐处理的女性尸体骨盆标本,建立髋关节生物力学模型,在模型上模拟偏心髋臼旋转截骨术。对骨盆缓慢施加连续纵向压力0~500 N,测量术前和术后载荷100、200、300、400、500 N时的股骨头承重区应变值,计算应力值。2007年7月至2014年10月应用偏心髋臼旋转截骨术治疗髋关节发育不良25例（26髋）,男6例,女19例;年龄11~57岁,平均31岁。术后以Harris髋关节评分评价髋关节功能,摄骨盆正位X线片测量头臼指数、中心边缘角（center-edge-angle,CE角）及Sharp角。结果-随着脊柱纵向压力加大,股骨头上的应力值随之增加。偏心髋臼旋转截骨术后应力值在载荷超过300 N后由上升趋势转变为下降趋势,总体呈抛物线状。100~500 N载荷下偏心髋臼旋转截骨术后的应力值与术前差异均无统计学意义。临床随访18例（19髋）,随访率72%。随访时间7~85个月,平均40个月。Harris髋关节评分由术前（64.3±7.2）分提高至末次随访时（85.6±5.3）分;头臼指数平均增加36.5%、CE角平均增加33.1°、Sharp角平均减少12.3°,与术前比较差异均有统计学意义。结论-偏心髋臼旋转截骨术具有较好的矫正髋臼畸形的能力,可增大股骨头的髋臼覆盖面和降低承重区压力。     

小干扰RNA特异性沉默c-myc基因对人胰腺癌SW1990细胞生物学影响

目的 观察小干扰RNA(siRNA)沉默c-myc基因的表达对人胰腺癌细胞株SW1990细胞生物学影响.方法 用siRNA沉默胰腺癌SW1990细胞中c-myc基因,用实时定量反转录聚合酶链反应(RT-qPCR)及Western blot技术检测c-myc mRNA及蛋白的表达量;噻唑蓝(MTT)法检测siRNA沉默c-myc基因对SW1990细胞增殖的影响;膜联蛋白V/碘化丙锭(Annexin V/PI)双染流式细胞术检测沉默c-myc基因细胞凋亡水平;Transwell细胞迁移实验检测siRNA沉默c-myc基因对SW1990细胞迁移能力的影响.结果 靶向c-myc的特异性siRNA可以高效抑制人胰腺癌SW1990细胞c-myc基因表达,在mRNA水平(0.263±0.048)较转染对照质粒组(0.970±0.012)明显降低,c-myc蛋白质表达量及细胞增值率均较转染对照质粒组明显降低;转染后48 h c-myc siRNA组细胞凋亡率为(19.90±2.09)％,明显高于siRNA阴性对照组(4.93±0.25)％和空白对照组(4.40±0.34)％;Transwell实验结果示细胞穿膜数c-myc siRNA组[(34.3±1.2)个]较siRNA-NC组[(68.3±5.8)个]和空白组[(72.3±1.2)个]均明显降低.结论 c-myc siRNA能够显著抑制c-myc基因在人胰腺癌SW1990细胞中的表达,降低细胞的增殖和迁移能力,促进细胞的凋亡.     

单孔腹腔镜与传统腹腔镜胆囊切除术治疗效果比较

目的 探讨单孔腹腔镜(SILC)与传统腹腔镜两种术式的安全性和可行性.方法 选取胆囊疾病患者54例随机分为SILC组(n=26)和三通道腹腔镜胆囊切除术(3PLC)组(n=28).收集患者年龄、体质量、身高、体质量指数(BMI)、手术时间、疼痛分数、中途转换手术率、切口满意度评分等临床资料,并进行了12个月的随访.结果 两组患者在性别、年龄、体质量、身高和BMI方面比较差异无统计学意义(P＞0.05).SILC组手术时间长于3PLC组[(56.9 ±15.8) min比(35.2±8.7) min,P＜0.01].应用相同的麻醉药品后SILC组在术后第1天较3PLC组疼痛分数更高,总的疼痛分数两者相似,差异无统计学意义(P＞0.05).SILC组患者术后伤口并发症发生率更高,但术后疝发生率相同.SILC组切口满意度评分分数更高[(11.7±0.8)分比(10.1±1.2)分,P＜0.05].结论 SILC较3PLC治疗单纯胆道疾病安全、有效.