Horsager Kristian, Kaptein Bart L, Rømer Lone, Jørgensen Peter B, Stilling Maiken
a Department of Orthopedics , Aarhus University Hospital , Aarhus , Denmark.
b Department of Orthopedic Surgery, Biomechanics and Imaging Group , Leiden University Medical Center , Leiden , the Netherlands.
Acta Orthop. 2017 Jun;88(3):275-281. doi: 10.1080/17453674.2016.1274592. Epub 2017 Jan 9.
Background and purpose - Implant inducible micromotions have been suggested to reflect the quality of the fixation interface. We investigated the usability of dynamic RSA for evaluation of inducible micromotions of the Oxford Unicompartmental Knee Arthroplasty (UKA) tibial component, and evaluated factors that have been suggested to compromise the fixation, such as fixation method, component alignment, and radiolucent lines (RLLs). Patients and methods - 15 patients (12 men) with a mean age of 69 (55-86) years, with an Oxford UKA (7 cemented), were studied after a mean time in situ of 4.4 (3.6-5.1) years. 4 had tibial RLLs. Each patient was recorded with dynamic RSA (10 frames/second) during a step-up/step-down motion. Inducible micromotions were calculated for the tibial component with respect to the tibia bone. Postoperative component alignment was measured with model-based RSA and RLLs were measured on screened radiographs. Results - All tibial components showed inducible micromotions as a function of the step-cycle motion with a mean subsidence of up to -0.06 mm (95% CI: -0.10 to -0.03). Tibial component inducible micromotions were similar for cemented fixation and cementless fixation. Patients with tibial RLLs had 0.5° (95% CI: 0.18-0.81) greater inducible medio-lateral tilt of the tibial component. There was a correlation between postoperative posterior slope of the tibial plateau and inducible anterior-posterior tilt. Interpretation - All patients had inducible micromotions of the tibial component during step-cycle motion. RLLs and a high posterior slope increased the magnitude of inducible micromotions. This suggests that dynamic RSA is a valuable clinical tool for the evaluation of functional implant fixation.
背景与目的——植入物诱导的微动已被认为可反映固定界面的质量。我们研究了动态RSA在评估牛津单髁膝关节置换术（UKA）胫骨组件诱导微动方面的实用性，并评估了那些被认为会影响固定的因素，如固定方法、组件对线和透光线（RLLs）。患者与方法——对15例患者（12例男性）进行研究，平均年龄69岁（55 - 86岁），均接受牛津UKA手术（7例为骨水泥固定），平均植入时间为4.4年（3.6 - 5.1年）。4例患者胫骨出现RLLs。在患者进行上/下台阶运动时，通过动态RSA（每秒10帧）对每位患者进行记录。计算胫骨组件相对于胫骨骨的诱导微动。使用基于模型的RSA测量术后组件对线，并在筛选的X线片上测量RLLs。结果——所有胫骨组件均显示出与步态周期运动相关的诱导微动，平均下沉量高达 -0.06毫米（95%置信区间：-0.10至 -0.03）。骨水泥固定和非骨水泥固定的胫骨组件诱导微动相似。出现胫骨RLLs的患者胫骨组件诱导的内外侧倾斜度大0.5°（95%置信区间：0.18 - 0.81）。胫骨平台术后后倾角度与诱导的前后倾斜之间存在相关性。解读——所有患者在步态周期运动期间胫骨组件均存在诱导微动。RLLs和高后倾角度会增加诱导微动的幅度。这表明动态RSA是评估功能性植入物固定的一种有价值的临床工具。
