Sala M, Taylor M, Tanner K E
Charing Cross Hospital, London, United Kingdom.
J Arthroplasty. 1999 Aug;14(5):610-5. doi: 10.1016/s0883-5403(99)90085-2.
The significance of torsional loads on the tibial component of total knee replacement prostheses is not clearly established. This study investigated the micromotion induced by torsion, under physiologic loads. Three forms of fixation were sequentially tested in cadaveric tibiae: press-fit, press-fit plus 4 peripheral corticocancellous screws, and horizontally cemented. The implanted tibia was loaded with an axial force between 0.5 and 2.2 kN and a cyclic torque of +/- 5 Nm. The relative motion between the prosthesis and the bone was measured. Our results show little difference between the 3 methods of fixation at high axial loads. At low axial loads, however, the press-fit prosthesis may permit micromotions high enough to interfere (theoretically) with bone ingrowth. Motion is reduced when the same prosthesis is augmented with screws. The cemented prosthesis produces the lowest average micromotion. Our study indicates that rotational micromotion is unlikely to contribute to the failure of ingrowth into the uncemented tibial prosthesis under normal physiologic loads. At low axial loads, which may be encountered in the immediate postoperative period, ingrowth may be compromised. Thus, initial rotational stability is an important consideration in uncemented total knee replacement design and postoperative management. In poor-quality tibiae, cementation may be the only method of fixation to provide sufficient torsional stability.
全膝关节置换假体胫骨部件上的扭转负荷的意义尚未明确确立。本研究调查了在生理负荷下扭转所引发的微动情况。在尸体胫骨上依次测试了三种固定方式：压配、压配加4枚周边皮质骨松质螺钉以及水平骨水泥固定。给植入的胫骨施加0.5至2.2 kN的轴向力以及±5 Nm的周期性扭矩。测量假体与骨之间的相对运动。我们的结果显示，在高轴向负荷下，这三种固定方法之间差异不大。然而，在低轴向负荷下，压配假体可能会允许足以（理论上）干扰骨长入的微动。当用螺钉增强同一假体时，运动减少。骨水泥固定假体产生的平均微动最低。我们的研究表明，在正常生理负荷下，旋转微动不太可能导致非骨水泥固定胫骨假体骨长入失败。在术后早期可能会遇到的低轴向负荷下，骨长入可能会受到影响。因此，初始旋转稳定性是无骨水泥全膝关节置换设计和术后管理中的一个重要考虑因素。在质量较差的胫骨中，骨水泥固定可能是提供足够扭转稳定性的唯一固定方法。
