BACKGROUND AND PURPOSE Dual-mobility hip arthroplasty utilizes a freely rotating polyethylene acetabular liner to protect against dislocation. As liner motion has not been confirmed in vivo, we undertook this using dynamic radiostereometry (RSA). PATIENTS AND METHODS 6 patients with Anatomical Dual Mobility acetabular components were included. Markers were implanted in the liners using a drill guide. Static RSA recordings and patient-reported outcome measures were obtained postoperatively and at 1-year follow-up. Dynamic RSA recordings were obtained at 1-year follow-up during passive hip movement: abduction/external rotation, adduction/internal rotation (modified FABER-FADIR), to end-range and at 45° hip flexion. Liner and neck movements were described as anteversion, inclination, and rotation. RESULTS Liner movement during modified FABER-FADIR was detected in 12 of 16 patients. Median (range) absolute liner movements were: anteversion 10° (5-20), inclination 6° (2-12), and rotation 11° (5-48) relative to the cup. Median absolute change in the resulting liner/neck angle (small articulation) was 28° (12-46) and in liner/cup angle (larger articulation) was 6° (4-21). Static RSA showed changes in median liner anteversion from 7° (-12 to 23) postoperatively to 10° (-3 to 16) at 1-year follow-up and inclination from 42° (35-66) postoperatively to 59° (46-80) at 1-year follow-up. Liner/neck contact was associated with high initial liner anteversion (p = 0.01). INTERPRETATION The polyethylene liner moves over time. 1 year after surgery the liner can move with or without liner/neck contact. The majority of movement is in the smaller articulation between head and liner.

中文翻译：

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双活动髋关节假体中的聚乙烯衬垫运动：16 名患者术后 1 年的静态和动态放射立体测量法。

背景和目的 双活动髋关节置换术利用可自由旋转的聚乙烯髋臼衬垫来防止脱位。由于线性运动尚未在体内得到证实，我们使用动态放射立体测量法 (RSA) 进行了这项研究。患者和方法 包括 6 名使用解剖学双活动髋臼假体的患者。使用导钻器将标记植入衬里。静态 RSA 记录和患者报告的结果测量在术后和 1 年随访时获得。动态 RSA 记录在 1 年随访期间的被动髋关节运动中获得：外展/外旋、内收/内旋（改良 FABER-FADIR）、最终范围和 45° 髋屈曲。衬垫和颈部运动被描述为前倾、倾斜和旋转。结果 16 名患者中有 12 名在改良 FABER-FADIR 期间检测到衬垫移动。中值（范围）绝对线性运动为：相对于杯子前倾 10° (5-20)，倾斜 6° (2-12)，旋转 11° (5-48)。产生的内衬/颈角（小关节）的中值绝对变化为 28° (12-46)，内衬/杯角（大关节）的绝对变化为 6° (4-21)。静态 RSA 显示中线前倾角从术后 7°（-12 到 23）变化到 1 年随访时的 10°（-3 到 16），倾斜度从术后 42°（35-66）到 59°（46 -80) 在 1 年的随访中。内衬/颈部接触与高初始内衬前倾相关 (p = 0.01)。解释 聚乙烯衬里随时间移动。手术后 1 年，衬垫可以在有或没有衬垫/颈部接触的情况下移动。