Finite Element Analysis of Mobile-bearing Unicompartmental Knee Arthroplasty: The Influence of Tibial Component Coronal Alignment

Background:

Controversies about the rational positioning of the tibial component in unicompartmental knee arthroplasty (UKA) still exist. Previous finite element (FE) studies were rare, and the results varied. This FE study aimed to analyze the influence of the tibial component coronal alignment on knee biomechanics in mobile-bearing UKA and find a ration range of inclination angles.

Methods:

A three-dimensional FE model of the intact knee was constructed from image data of one normal subject. A 1000 N compressive load was applied to the intact knee model for validating. Then a set of eleven UKA FE models was developed with the coronal inclination angles of the tibial tray ranging from 10° valgus to 10° varus. Tibial bone stresses and strains, contact pressures and load distribution in all UKA models were calculated and analyzed under the unified loading and boundary conditions.

Results:

Load distribution, contact pressures, and contact areas in intact knee model were validated. In UKA models, von Mises stress and compressive strain at proximal medial cortical bone increased significantly as the tibial tray was in valgus inclination >4°, which may increase the risk of residual pain. Compressive strains at tibial keel slot were above the high threshold with varus inclination >4°, which may result in greater risk of component migration. Tibial bone resection corner acted as a strain-raiser regardless of the inclination angles. Compressive strains at the resected surface slightly changed with the varying inclinations and were not supposed to induce bone resorption and component loosening. Contact pressures and load percentage in lateral compartment increased with the more varus inclination, which may lead to osteoarthritis progression.

Conclusions:

Static knee biomechanics after UKA can be greatly affected by tibial component coronal alignment. A range from 4° valgus to 4° varus inclination of tibial component can be recommended in mobile-bearing UKA.     

人股骨头骨微血管内皮细胞的分离培养方法

目的:探讨培养人股骨头骨微血管内皮细胞分离培养方法.方法:2013年10月至2014年1月15例行髋关节置换患者切除的内部无病变的股骨头,男2例,女13例;年龄38～92岁,平均71.2岁.无菌条件下将股骨头内松质骨咬成碎骨粒,放入培养基.采用酶消化法,密度梯度离心法分离细胞;差速贴壁法,选择性培养基法纯化细胞.倒置显微镜观察细胞特点,并采用vWF、CD31免疫荧光进行细胞鉴定.结果:原代培养24 h后倒置显微镜下观察细胞数量与患者年龄呈正相关,年龄越大细胞越少.培养4～5 d细胞呈短梭形、多角形或“鹩卵石”状.培养7～10d细胞生长密集,细胞融合呈漩涡状,接触抑制明显.vWF、CD31免疫荧光检测阳性率100％,表明细胞为骨微血管内皮细胞.结论:人股骨头骨微血管内皮细胞分离培养方法简单、稳定、有效、可重复性好,可以获得纯度较高的股骨头骨微血管内皮细胞.     

活动平台单髁膝关节置换胫骨后倾的有限元分析

背景：目前单髁膝关节置换中胫骨假体后倾角度的选择存在较多争议,相关的生物力学研究较少。 目的：通过有限元分析结果寻求活动平台单髁膝关节置换中合理胫骨后倾的角度。 方法：运用三维重建技术及有限元前处理技术建立正常膝关节有限元模型,并进行验证,在此基础上建立不同胫骨假体后倾角度的单髁膝关节置换有限元模型,统一边界条件和载荷,行有限元分析。 结果与结论：成功建立了不同胫骨后倾角度的单髁膝关节置换有限元模型,分析结果发现增大胫骨假体后倾可使胫骨后内侧皮质及松质骨应力逐渐增加,且增大了外侧间室载荷和软骨接触应力,而胫骨前倾使胫骨前内侧皮质应力明显增加。推荐活动平台单髁膝关节置换中选择0°-7°胫骨假体后倾。 中国组织工程研究杂志出版内容重点：人工关节;骨植入物;脊柱;骨折;内固定;数字化骨科;组织工程