Pérez-Blanca A, Prado M, Ezquerro F, Montañéz E, Espejo A
Department of Mechanical Engineering, Campus El Ejido, University of Málaga, 29013 Málaga, Spain.
Clin Biomech (Bristol). 2008 May;23(4):483-92. doi: 10.1016/j.clinbiomech.2007.11.012. Epub 2008 Jan 2.
Short central extensions which do not enter the tibial medullary canal are incorporated to cemented tibial components to increase initial stability in primary total knee arthroplasty. Their role in tibiae of differing preoperative mechanical quality has been little studied.
Twelve embalmed cadaveric tibiae were paired and divided into two groups, receiving a similar cemented tibial component with or without a non-cemented short central extension (10 mm diameter, 35 mm length). The specimens were subjected to 6000 cycles of a medially applied 1350 N load. Relative bone-tray displacements were measured and the evolution of inducible and permanent micromotions were computed. The apparent density of the cancellous bone under the tibial tray and at the area to support the extension was computed from computed tomography images of each specimen.
No significant differences between groups were detected for any parameters. For the group with extension, a significant negative linear correlation (P = 0.009, r(2) = 0.849) was found between the inducible tilt of the tray and the bone density at the zone of the extension. Also a trend towards a negative linear relation (P = 0.07, r(2) = 0.59) was observed for the same group between maximum subsidence and apparent density at the zone of the extension.
The study did not find that the addition of a non-cemented short central extension provides any overall improvement of the initial fixation stability. However, it was found that short extensions may enhance tilting stiffness of the bone-implant construct if bone of sufficient mechanical quality is located around its supporting area.
在初次全膝关节置换术中，不进入胫骨髓腔的短中央延伸部分被用于骨水泥固定的胫骨组件，以增加初始稳定性。它们在术前机械质量不同的胫骨中的作用鲜有研究。
将12具防腐处理的尸体胫骨配对并分为两组，分别植入带有或不带有非骨水泥短中央延伸部分（直径10毫米，长度35毫米）的类似骨水泥固定胫骨组件。对标本施加6000次内侧1350牛负荷循环。测量相对骨托位移，并计算诱导性和永久性微动的演变。根据每个标本的计算机断层扫描图像计算胫骨托下方和支撑延伸部分区域的松质骨表观密度。
两组之间在任何参数上均未检测到显著差异。对于有延伸部分的组，发现骨托的诱导性倾斜与延伸部分区域的骨密度之间存在显著的负线性相关性（P = 0.009，r² = 0.849）。在同一组中，还观察到最大下沉与延伸部分区域的表观密度之间有负线性关系的趋势（P = 0.07，r² = 0.59）。
该研究未发现添加非骨水泥短中央延伸部分能总体改善初始固定稳定性。然而，发现如果在其支撑区域周围存在机械质量足够的骨，短延伸部分可能会增强骨-植入物结构的倾斜刚度。
