Lynch Joseph T, Perriman Diana M, Scarvell Jennie M, Pickering Mark R, Galvin Catherine R, Neeman Teresa, Smith Paul N
Trauma and Orthopaedic Research Unit, Medical School, Australian National University, Canberra, Australia.
Faculty of Health, University of Canberra, Canberra, Australia.
Bone Joint J. 2021 Jan;103-B(1):105-112. doi: 10.1302/0301-620X.103B1.BJJ-2020-0958.R1.
Modern total knee arthroplasty (TKA) prostheses are designed to restore near normal kinematics including high flexion. Kneeling is a high flexion, kinematically demanding activity after TKA. The debate about design choice has not yet been informed by six-degrees-of-freedom in vivo kinematics. This prospective randomized clinical trial compared kneeling kinematics in three TKA designs.
In total, 68 patients were randomized to either a posterior stabilized (PS-FB), cruciate-retaining (CR-FB), or rotating platform (CR-RP) design. Of these patients, 64 completed a minimum one year follow-up. Patients completed full-flexion kneeling while being imaged using single-plane fluoroscopy. Kinematics were calculated by registering the 3D implant models onto 2D-dynamic fluoroscopic images and exported for analysis.
CR-FB designs had significantly lower maximal flexion (mean 116° (SD 2.1°)) compared to CR-RP (123° (SD 1.6°)) and PS-FB (125° (SD 2.1°)). The PS-FB design displayed a more posteriorly positioned femur throughout flexion. Furthermore, the CR-RP femur was more externally rotated throughout kneeling. Finally, individual patient kinematics showed high degrees of variability within all designs.
The increased maximal flexion found in the PS-FB and CR-RP designs were likely achieved in different ways. The PS-FB design uses a cam-post to hold the femur more posteriorly preventing posterior impingement. The external rotation within the CR-RP design was surprising and hasn't previously been reported. It is likely due to the polyethylene bearing being decoupled from flexion. The findings of this study provide insights into the function of different knee arthroplasty designs in the context during deep kneeling and provide clinicians with a more kinematically informed choice for implant selection and may allow improved management of patients' functional expectations. Cite this article: 2021;103-B(1):105-112.
现代全膝关节置换术（TKA）假体旨在恢复接近正常的运动学，包括高屈曲度。跪姿是TKA术后一种高屈曲度且对运动学要求较高的活动。关于设计选择的争论尚未有体内六自由度运动学的相关依据。这项前瞻性随机临床试验比较了三种TKA设计中的跪姿运动学。
总共68例患者被随机分为后稳定型（PS-FB）、保留交叉韧带型（CR-FB）或旋转平台型（CR-RP）设计。其中，64例患者完成了至少一年的随访。患者在进行单平面荧光透视成像时完成全屈曲跪姿。通过将3D植入物模型注册到2D动态荧光透视图像上计算运动学，并导出进行分析。
与CR-RP（123°（标准差1.6°））和PS-FB（125°（标准差2.1°））相比，CR-FB设计的最大屈曲度显著更低（平均116°（标准差2.1°））。PS-FB设计在整个屈曲过程中显示股骨位置更靠后。此外，CR-RP股骨在整个跪姿过程中外旋更多。最后，个体患者的运动学在所有设计中都显示出高度的变异性。
PS-FB和CR-RP设计中增加的最大屈曲度可能是以不同方式实现的。PS-FB设计使用凸轮柱使股骨更靠后，防止后方撞击。CR-RP设计中的外旋令人惊讶，此前未见报道。这可能是由于聚乙烯衬垫与屈曲解耦。本研究结果为不同膝关节置换设计在深度跪姿情况下的功能提供了见解，并为临床医生在植入物选择上提供了更具运动学依据的选择，可能有助于改善患者功能预期的管理。引用本文：2021;103-B(1):105-112。
