Effects of tibial stem on tibiae stress distribution in high BMI patients received total knee arthroplasty

QIANG Shuo; GAO Zong-yan; XU Kui-xue; ZHANG Jian-peng; ZHENG Jia

doi:10.3969/j.issn.2095-252X.2017.04.009

Abstract：Objective Using finite element ( FE ) analysis to explore the influence of the tibial base plate with different length of stemming of total knee arthroplasty ( TKA ) in obese patients on the tibial stress distribution and variation of tibial plateau stress with varus plateau. Methods A healthy female volunteer was enrolled in the present study. First 3D FE models of the knee joint were reconstrusted on the basis of the spiral CT scans of the volunteer. Four FE models were constructed of the tibia plateau ( standard tibial base plate, tibial plate + 60 mm-long stem, tibial plate + 100 mm-long stem, standard tibial base plate with 5° varus ) to analyze the biomechanical variation in full-length tibia stress pattern. Results There were significant differences ( P < 0.05 ) in tibia stress pattern between standard tibial base plate ( 42.3 MPa ) and tibia plateau with stem of 60 mm ( 66.3 MPa ) and 100 mm ( 67.2 MPa ). Using 60 mm stem to make the posterior stress of tibia plateau much lower than other groups, but there were no significant differences between 60 mm and 100 mm. In the model of 100 mm stem, the stress of medial tibia plateau was significantly lower than the standard tibial plate and 60mm stem ( P < 0.01 ). There were no significant differences among these 3 different lengths of stems in the anterior and lateral tibia plateau. Stress of medial tibia plateau was much higher in 5°varus standard tibial base plate. Conclusions Tibia plateau vatus would increase medial stress of plateau, and using stem could transmit proximal stress to distal of tibia. The 60 mm stem is availiable for the posterior tibia bone defect, and can reduce the posterior stress. And 100 mm stem could lower the medial stress distribution of tibial plateau. Increasing the length of stem would not dismiss stress, on the contrary, long stem may cause significant stress shielding in the proximal tibia.