Abstract
Background: High stress developed in the cement mantle of a total hip replacement is reported to contribute to premature failure of acetabular components. We postulate that stress level is influenced by cement mantle thickness, acetabular size, bone quality and body mass index. Methods: Finite element models of reconstructed hemi pelves of different sizes and acetabular diameters (46, 52 and 58 mm) were created from CT-Scan data. We investigated the effects of cement mantle thickness (1, 2, 3 and 4 mm), acetabular size, body mass index (BMI = 20, 25 and 30 kg/m2) and bone quality on stress level developed in the cement mantle. Findings: Peak tensile stresses in the cement mantle increased with a decrease in cement mantle thickness, acetabular size and bone quality and an increase in BMI. Interpretation: Our results indicate that a 4-mm-thick cement mantle is required in small reconstructed acetabulae of ≤ 50-mm diameters, while a 1-mm thick cement mantle can be used on larger reconstructed acetabulae of ≥ 58 mm diameter. Patients with poor bone quality require at least a 4-mm-thick cement mantle to reduce the risk failure caused by high stress level in the cement mantle.
Highlights
Cemented hip replacement, as a means to help people suffering from hip disorders to regain mobility, is used in one third of the 76,448 primary total hip replacements (THRs) carried out in the UK in 2012 [1]
Peak von Mises and shear stress developed in the acetabular components decreased with an increase in cement mantle thickness
Our study shows that the patient’s bone quality, acetabular size and body mass index (BMI) should be taken into consideration when surgically reconstructing the acetabulum
Summary
As a means to help people suffering from hip disorders to regain mobility, is used in one third of the 76,448 primary total hip replacements (THRs) carried out in the UK in 2012 [1]. The rate of revision due to aseptic loosening could be as high as 75.4% 20 years postoperatively [3]; In addition to bone resorption [4,5,6,7,8], poor cementing techniques can lead to premature failure of the acetabular components caused by improper mechanical interlock between the cement and the bone, as can be detected by radiolucencies [9,10,11]. If the stress level in the cement mantle is too high, the mechanical interlock between the bone and cement can be disrupted and contribute to the loosening process. High stress developed in the cement mantle of a total hip replacement is reported to contribute to premature failure of acetabular components. We postulate that stress level is influenced by cement mantle thickness, acetabular size, bone quality and body mass index
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