Influence of post-cam design on stresses on posterior-stabilized tibial posts.
Polyethylene wear and fracture at the tibial post of posterior- stabilized knee prostheses are common complications. Analyzing the stresses on various designs of tibial posts should predict the risk of damage. The post-cam of knee prostheses generally are designed either as flat-on-flat or curve-on- curve contact surfaces. We investigated stress on such tibial posts using a finite element method. We applied a 500-N anteroposterior shear force to the knee at neutral contact and 10 degrees tibial internal rotation when the knee was flexed at 60 degrees , 90 degrees , 120 degrees , and 150 degrees . There was more stress during tibial rotation compared with during neutral contact. The greatest increments of maximum von Mises stress and contact stress in the flat-on-flat model were from 20.4 to 46.1 MPa (126.3%) and from 22.2 to 55.7 MPa (151%), respectively, whereas in the curve-on-curve design they were from 20.5 to 22.7 MPa (10.7%) and from 33.0 to 35.4 MPa (7.2%), respectively. Increased stress concentration at the tibial post occurred at increased flexion angles along with axial tibial rotation. The curve-on-curve design reduced stress concentration when the knee sustained an anteroposterior shear force with tibial rotation.
Huang
Chang-Hung
CH
Institute of Biomedical Engineering, National Yang Ming University, No. 155 Section 2 Li-Nung Street, Shih-Pai, Taipei 11221, Taiwan.
Liau
Jiann-Jong
JJ
Huang
Chun-Hsiung
CH
Cheng
Cheng-Kung
CK
D020342:Finite Element Analysis; D006801:Humans; D007719:Knee Joint / Q000503:physiopathology; D011474:Prosthesis Design; D012399:Rotation; D013314:Stress, Mechanical