单髁置换术平台下钉孔影响平台应力的有限元分析

Finite element analysis of effects of nail holes on tibial plateau stress distribution in unicompartmental knee arthroplasty

目的探讨单髁置换术截骨导板固定钉孔位置对胫骨平台应力分布的影响。方法收集广东省第二中医院影像中心10例行下肢血管造影检查且无骨质病变的成年胫骨全长CT扫描Dicom数据,所有患者均为行下肢血管造影检查且排除骨质病变及畸形。利用Mimics 20.0行三维重建,得到正常的胫骨全长模型,导入Abaqus进行固定平台单髁置换胫骨部分的手术模拟。在胫骨截骨面下15 mm水平的不同位置设置直径为3 mm的克氏针临时固定孔模拟术中钉孔残留,根据钉孔位置将模型分为4组,分别是:A组(无钉孔);B组(钉孔位于垂直截骨线正下方);C组(钉孔位于龙骨槽正下方);D组(钉孔位于龙骨槽外侧3 mm)。设置感兴趣区(ROI)2个:ROI 1为胫骨垂直截骨与水平面截骨拐角处,ROI 2为龙骨槽底部。分析不同情况下胫骨平台应力分布情况。采用单因素方差分析对四组间的差异情况进行比较,采用SNK或Dunnett’s T3法对组间均数进行两两比较。结果与无钉孔组相比,B组的ROI 1最大应力增大,且有统计学意义(P<0.05),应力为(22.31±0.79)MPa(增幅达12.3%);C组的ROI 1(P<0.05)及ROI 2(t=-8.09,P<0.05)最大应力均有增大,且有统计学意义,应力分别为(20.76±0.86)MPa(增幅5.7%)、(0.69±0.03)MPa(增幅13.1%);D组ROI 1与无钉孔相比差异无统计学意义(P>0.05),ROI 2最大应力较无钉孔稍有降低,差异有统计学意义(t=0.34,P<0.05)。结论单髁置换术中,胫骨平台下钉孔残留会影响平台应力的分布,当钉孔位置位于垂直截骨以及龙骨槽下方时会引起ROI 1及ROI 2处最大应力明显增大,增加胫骨平台骨折的风险。术中操作时截骨模板固定钉需注意避开危险区域。

Objective To investigate the effect of different nail holes of osteotomy guide plate on the tibial plateau stress distribution.Methods Dicom data of 10 full-length CT scans of adult tibia with lower extremity angiography and no bone disease were collected from the Imaging Center of Guangdong Second Hospital of Traditional Chinese Medicine.A three-dimensional reconstruction of Mimics 20.0 was performed to obtain a normal full-length humeral model,then import the model into the Abaqus for simulated surgery.The nail holes remains after the temporary fixation of the K-wire with a diameter of 3 mm at different positions 15 mm below the tibial osteotomy surface.The model is divided into four groups according to the position of the nail holes,namely:group A(no nail hole)group B(the nail hole was located directly below the vertical osteotomy line);group C(the nail hole was located directly below the keel groove);group D(the nail hole was located 3 mm outside the keel groove).Two regions of interest(ROI)were set:ROI1 was the corner of the vertical osteotomy and the plane osteotomy,and ROI2 was the bottom of the keel.Analyze the stress distribution of the tibial plateau under different conditions.One-way ANOVA was used to compare the differences between four groups,and SNK or Dunnett’s T3 was used to compare means between groups in pairs.Results Compared with group A,the maximum stress of ROI1 in group B increased,and the difference was statistically significant(P<0.05),the stress was(22.31±0.79)MPa(increased by 12.3%).The maximum stress of ROI1(P<0.05)and ROI2(t=-8.09,P<0.05)in group C also increased with statistical significance.The stresses were(20.76±0.86)MPa(5.7%increase)and(0.69±0.03)MPa(up 13.1%)respectively.There was no significant difference in the maximum stress of ROI1 between group D and group A(P>0.05).The maximum stress of ROI2 in group D was slightly lower than that without nail hole,and the difference was statistically significant(t=0.34,P<0.05).Conclusions In UKA,the nail hole under the tibial plateau will affect the distribution of platform stress.When the position of the nail hole is located under the vertical osteotomy and the keel groove,the maximum stress at ROI1 and ROI2 will increase significantly,and the risk of tibial plateau fracture will be increased.During the operation,the osteotomy template fixation nails should be avoided to avoid dangerous areas.