Baré J V, Gill H S, Beard D J, Murray D W
OOEC/Nuffield Department of Orthopaedic Surgery, University of Oxford, Nuffield Orthopaedic Centre, Oxford, UK.
Knee. 2006 Mar;13(2):122-6. doi: 10.1016/j.knee.2005.09.001. Epub 2006 Jan 5.
Unicompartmental knee replacements have not performed as well in the lateral compartment as in the medial. This may be because the tibial components have flat or slightly concave surfaces which match the medial plateau but not the convex lateral plateau. The aim of this study was to find the optimal radius for a convex lateral tibial component. Twelve normal lateral tibial plateau were retrieved at knee replacement, and their surface contour in their mid sagittal plane was determined. The optimal circle was fitted and its radius measured. A series of different shaped tibial components were superimposed. From published information about the position of the femoral condyle relative to the tibia in different degrees of flexion, the flexion gap at these angles was determined. The average radius of the lateral tibial plateau was 40 mm. However, as the surface was polyradial it was not clear if this average radius would be optimal. In full flexion, a flat tibial plateau distracted the knee by 8 mm (p<0.001). A 75 mm radius spherical tibial plateau did not alter the knee kinematics significantly and gave rise to a change in joint distraction of 1.5 mm. Spherical tibial plateau of 50 mm and 25 mm radii significantly altered knee kinematics (p<0.001) and resulted in changes in distraction of 3 mm and 4 mm respectively. The optimal shape for a unicompartmental lateral tibial plateau is likely to be a spherical dome with radius of about 75 mm. The incorporation of this shape in the lateral side of a total knee replacement might improve its flexion.
单髁膝关节置换术在外侧间室的效果不如在内侧间室。这可能是因为胫骨假体的表面是平的或略呈凹形，与内侧平台匹配，但与外侧凸形平台不匹配。本研究的目的是找到外侧胫骨假体的最佳半径。在膝关节置换术中获取了12个正常的外侧胫骨平台，并确定了它们在矢状面中部的表面轮廓。拟合出最佳圆并测量其半径。叠加了一系列不同形状的胫骨假体。根据已发表的关于不同屈曲程度时股骨髁相对于胫骨位置的信息，确定了这些角度下的屈曲间隙。外侧胫骨平台的平均半径为40mm。然而，由于表面是多半径的，不清楚这个平均半径是否最佳。在完全屈曲时，平坦的胫骨平台使膝关节分离8mm（p<0.001）。半径为75mm的球形胫骨平台对膝关节运动学没有显著影响，关节分离变化为1.5mm。半径为50mm和25mm的球形胫骨平台显著改变了膝关节运动学（p<0.001），分别导致分离变化3mm和4mm。单髁外侧胫骨平台的最佳形状可能是半径约为75mm的球形穹顶。在全膝关节置换术的外侧采用这种形状可能会改善其屈曲功能。
