The effect of cup outer sizes on the contact mechanics and cement fixation of cemented total hip replacements.
One important loosening mechanism of the cemented total hip arthroplasty is the mechanical overload at the bone-cement interface and consequent failure of the cement fixation. Clinical studies have revealed that the outer diameter of the acetabular component is a key factor in influencing aseptic loosening of the hip arthroplasty. The aim of the present study was to investigate the influence of the cup outer diameter on the contact mechanics and cement fixation of a cemented total hip replacement (THR) with different wear penetration depths and under different cup inclination angles using finite element (FE) method. A three-dimensional FE model was developed based on a typical Charnley hip prosthesis. Two acetabular cup designs with outer diameters of 40 and 43 mm were modelled and the effect of cup outer diameter, penetration depth and cup inclination angle on the contact mechanics and cement fixation stresses in the cemented THR were studied. The results showed that for all penetration depths and cup inclination angles considered, the contact mechanics in terms of peak von Mises stress in the acetabular cup and peak contact pressure at the bearing surface for the two cup designs were similar (within 5%). However, the peak von Mises stress, the peak maximum principal stress and peak shear stress in the cement mantle at the bone-cement interface for the 43 mm diameter cup design were predicted to be lower compared to those for the 40 mm diameter cup design. The differences were predicted to be 15-19%, 15-22% and 18-20% respectively for different cup penetration depths and inclination angles, which compares to the clinical difference of aseptic loosening incidence of about 20% between the two cup designs.
Institute of Medical and Biological Engineering, School of Mechanical Engineering, University of Leeds, Leeds LS2 9JT, United Kingdom. Electronic address: xijinhua@outlook.com.
Xijin
X
Hua
School of Science and Technology, Middlesex University, London HA0 1EH, UK.
Junyan
J
Li
School of Mechanical Engineering, Xi'an Jiaotong University, Xi'an 710049, Shanxi, China.
Ling
L
Wang
Institute of Medical and Biological Engineering, School of Mechanical Engineering, University of Leeds, Leeds LS2 9JT, United Kingdom.
Ruth
R
Wilcox
Institute of Medical and Biological Engineering, School of Mechanical Engineering, University of Leeds, Leeds LS2 9JT, United Kingdom.
John
J
Fisher
Institute of Medical and Biological Engineering, School of Mechanical Engineering, University of Leeds, Leeds LS2 9JT, United Kingdom; School of Mechanical Engineering, Xi'an Jiaotong University, Xi'an 710049, Shanxi, China.
Zhongmin
Z
Jin
D019644:Arthroplasty, Replacement, Hip / Q000379:methods; D001843:Bone Cements; D020342:Finite Element Analysis; D006622:Hip Prosthesis; D006801:Humans; D008962:Models, Theoretical; D020959:Polyethylene; D011312:Pressure; D011474:Prosthesis Design; D011475:Prosthesis Failure; D013314:Stress, Mechanical
D001843:Bone Cements; D020959:Polyethylene
Cement fixation; Contact mechanics; Cup outer diameter; Inclination angle; Penetration; Total hip replacement