Department of Orthopaedics, Traumatology and Sports Medicine, Lyon-South Hospital Center, chemin du Grand Revoyet, 69495 Pierre-Bénite cedex, France.
Orthop Traumatol Surg Res. 2009 Jun;95(4):254-9. doi: 10.1016/j.otsr.2009.03.012. Epub 2009 May 12.
Total knee prostheses with a mobile-bearing insert were developed to provide nonconstrained joint range of motion while reducing friction forces. The purpose of this study was, based on weightbearing X-rays, to evaluate the mobility of the polyethylene tibial insert in relation to the femoral and tibial components. We studied the results of a cementless total knee arthroplasty (TKA) retaining the posterior cruciate ligament (PCL), with a mobile-bearing platform in rotation and anteroposterior translation (Innex Anterior-Posterior Glide, Zimmer) with a mean 23-month follow-up duration after surgery.
Both anterior-posterior tibiofemoral translation and intraprosthetic axial rotation occur between the mobile polyethylene insert and the tibial endplate.
In a series of 51 primary TKA, the three-dimensional (3D) kinematics of the femoral, tibial, and mobile insert components were determined using a computerized matching system between the prosthetic 3D models and the radiographic images of the implants on three lateral follow-up weightbearing knee X-rays: films were taken in full extension, at 45 degrees flexion, and at maximum flexion.
There was a statistically significant increase in the internal rotation of the mobile tray with flexion, (up to a mean -3+/-3 degrees between the femoral box and the mobile tray [p<0.0001] and up to a mean -5+/-7 degrees between the tibial tray and the mobile tray [p<0.0001]). The mobile tray did not translate in relation to the tibial endplate from extension to 45 degrees flexion (0+/-2 mm [range: -5 to 6 mm]). However, from 45 degrees to maximum flexion, a statistically significant mean 1+/-2 mm (range: -2 to 9 mm) of anterior translation (p<0.0001) was found.
The extent of insert mobility varies from one study to another. Some have reported relatively limited mobility stemming from a superior surface that is not highly congruent, (thus allowing anterior-posterior and mediolateral translation through gliding of the femur in contact with the insert). Other studies have reported mobile-bearing tray mobility in relation to the tibial endplate and minimal rotation at the femoral component level. In this series of PCL retaining TKA with a mobile-bearing platform, the mobile-bearing platform showed a progressive increase in internal rotation during flexion. Most of this rotational mobility occurred between the mobile platform and the tibial endplate, confirming our hypothesis. However, with flexion, the femoral component increased its mobility relatively to the platform. During flexion, an anterior-posterior translation occurred between the femoral implant and the tibial insert, and between the tibial insert and the tibial endplate, but the direction of the mobile tibial insert translation remained unpredictable with this nonconstrained implant design used.
Level IV. Prospective non-controlled therapeutic study.
为了提供非约束性的关节活动范围并减少摩擦阻力，开发了带有活动衬垫的全膝关节假体。本研究的目的是基于负重 X 射线评估聚乙烯胫骨衬垫相对于股骨和胫骨部件的活动度。我们研究了保留后交叉韧带（PCL）的非骨水泥全膝关节置换术（TKA）的结果，该置换术采用旋转和前后平移的活动平台（Innex 前后滑动，Zimmer），术后平均随访 23 个月。
活动聚乙烯衬垫与胫骨基板之间会发生前-后胫骨股骨平移和关节内轴向旋转。
在一系列 51 例初次 TKA 中，使用计算机匹配系统确定了股骨、胫骨和活动衬垫组件的三维（3D）运动学，该系统将假体 3D 模型与植入物的 X 射线图像进行匹配，这些 X 射线图像来自三次外侧负重膝关节 X 射线随访：在完全伸展、45 度屈曲和最大屈曲时拍摄胶片。
随着屈曲，活动托盘的内旋转呈统计学显著增加（股骨盒和活动托盘之间最大平均-3+/-3 度[p<0.0001]，胫骨托盘和活动托盘之间最大平均-5+/-7 度[p<0.0001]）。从伸展到 45 度屈曲，活动托盘相对于胫骨基板没有发生平移（0+/-2 毫米[范围：-5 至 6 毫米]）。然而，从 45 度到最大屈曲，发现统计学上显著的平均 1+/-2 毫米（范围：-2 至 9 毫米）的前向平移（p<0.0001）。
衬垫的活动程度因研究而异。有些研究报告说，由于上表面不太一致，因此活动范围相对有限（从而允许股骨通过与衬垫接触在滑动过程中发生前-后和内-外侧平移）。其他研究报告了与胫骨基板有关的活动衬垫托盘的活动度和股骨组件水平的最小旋转。在这个保留 PCL 的带有活动平台的 TKA 系列中，活动平台在屈曲过程中表现出逐渐增加的内旋转。这种旋转活动度主要发生在活动平台和胫骨基板之间，证实了我们的假设。然而，随着屈曲，股骨组件相对于平台增加了其活动度。在屈曲过程中，股骨植入物和胫骨衬垫之间以及胫骨衬垫和胫骨基板之间发生了前-后平移，但在这种非约束性植入物设计下，活动胫骨衬垫的平移方向仍然不可预测。
IV 级。前瞻性非对照治疗研究。
