Background 

The introduction of crosslinked ultra-high molecular weight polyethylene (XLPE) acetabular liners has been very successful, with decreased wear and reduction in the rates of revision hip arthroplasties. XLPE is the preferred articulation for most surgeons; however, there are concerns about the long-term performance of XLPE liners created with different manufacturing processes, which may lead to time-dependent failure, including accelerated wear, after several years.

Questions/purposes 

(1) What is the amount and rate of wear during the first 10 years using radiostereometric analysis (RSA) measurements of patients who had THAs that included a second-generation XLPE bearing? (2) Does the rate of wear change after 5 years in situ?

Methods 

This is a brief follow-up of a previous RSA study. In that study, we prospectively enrolled 21 patients with osteoarthritis who underwent primary cementless THA with an XLPE acetabular liner (three cycles of 3Mrad annealed) and 32-mm articulation. That group represented 44% of the 48 THAs performed by the surgeon at the hospital where RSA was available; 16 had cemented hips, leaving 32 who were invited to participate in this study. Of those, 11 lived rurally and declined to participate, leaving 21 patients who were included in the initial study. Since then, three patients died, one developed dementia and could not participate, and one had revision THA for reasons other than wear, leaving 16 patients available for analysis at 10 years. Tantalum markers were inserted during surgery, and all patients had RSA radiographs taken at 1 week, 6 months, and 1, 2, 5, and 10 years postoperatively. Femoral head penetration into the acetabular component was measured with RSA, including bedding-in during the first year and annual wear thereafter.

Results 

The median medial, proximal, anterior, two-dimensional (2D), and three-dimensional (3D) wear rates between 1 and 10 years were -0.001, 0.004, -0.012, 0.000, and 0.002 mm/year, respectively. No patient in this cohort had a proximal or 2D wear rate greater than 0.025 mm/year. The median proximal wear rate between 5 and 10 years (0.002 mm/year) was not greater than wear at 1 to 5 years (0.004 mm/year).

Conclusion 

Femoral head penetration in this second-generation XLPE liner remained very low at 10 years and accelerated wear after 5 years in situ did not occur. Concerns about late-onset wear from oxidation of irradiated-annealed XLPE were not observed. The low level of wear remains encouraging for the future clinical performance of this material.

Level of Evidence 

Level II, therapeutic study.

中文翻译：

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高度交联的聚乙烯内衬 10 年磨损可忽略不计：放射立体分析研究

背景 

交联超高分子量聚乙烯 (XLPE) 髋臼衬垫的引入非常成功，减少了磨损并降低了髋关节翻修率。XLPE 是大多数外科医生的首选关节；然而，人们担心采用不同制造工艺制造的 XLPE 衬里的长期性能可能会导致与时间相关的故障，包括几年后加速磨损。

问题/目的 

(1) 对于接受了包含第二代 XLPE 轴承的 THA 的患者，使用放射立体测量分析 (RSA) 测量，头 10 年的磨损量和磨损率是多少？(2)原位5年后磨损率有变化吗？

方法 

这是之前 RSA 研究的简短后续研究。在该研究中，我们前瞻性地招募了 21 名骨关节炎患者，他们接受了初次非骨水泥全髋关节置换术，使用 XLPE 髋臼内衬（三个周期的 3Mrad 退火）和 32 毫米关节。该组占 RSA 医院外科医生实施的 48 例 THA 的 44%；其中 16 人接受了髋关节骨水泥固定，剩下 32 人被邀请参加这项研究。其中 11 名居住在农村的患者拒绝参与，剩下 21 名患者被纳入最初的研究。此后，三名患者死亡，一名患者出现痴呆症而无法参与，一名患者因磨损以外的原因进行了全髋关节置换术翻修，留下 16 名患者在 10 年时可供分析。手术期间植入钽标记物，所有患者均在术后 1 周、6 个月以及术后 1、2、5 和 10 年拍摄 RSA X 线照片。使用 RSA 测量股骨头对髋臼假体的渗透情况，包括第一年的磨合情况和此后的每年磨损情况。

结果 

1 年至 10 年的中位内侧、近端、前侧、二维 (2D) 和三维 (3D) 磨损率分别为 -0.001、0.004、-0.012、0.000 和 0.002 毫米/年。该队列中没有患者的近端磨损率或二维磨损率大于 0.025 毫米/年。5 至 10 年的中位近端磨损率（0.002 毫米/年）不大于 1 至 5 年的磨损率（0.004 毫米/年）。

结论 

第二代 XLPE 衬里的股骨头穿透力在 10 年内仍然非常低，并且在原位 5 年后没有发生加速磨损。没有观察到对辐照退火 XLPE 氧化引起的迟发磨损的担忧。低磨损水平对于这种材料未来的临床性能仍然令人鼓舞。

证据水平 

第二级，治疗研究。