Shape suitability and mechanical safety of customised hip implants: Three-dimensional printed acetabular cup for hip arthroplasty

Abstract

Background: Owing to an increase in the number of hip arthroplasty surgeries, the number of implant replacement surgeries is increasing rapidly as well. This necessitates the study of hip joint conditions. Therefore, Paprosky defined a classification system to indicate the degree of damage to the hip joint. In this study, a customised hip implant suitable for Paprosky classification Type ⅡC and over was designed. The shape, suitability, and mechanical safety of the worst-case model for the implant were evaluated.

Materials and methods: To identify the implant size depending on states over Type ⅡC acetabulum bone loss, a size range was selected and a customised implant was designed according to the computed tomography data within the size range. The implant was designed for the flange, hook, and flattened model types. The worst-case selection test was conducted using finite element analysis. The von Mises stresses of the flange, hook, and flattened models were found as 76.223, 136.99, and 80.791 MPa, respectively. Therefore, the hook-type model was selected as the worst case for the mechanical performance test.

Results: A bending test was conducted on the hook-type model without fracture and failure at 5344.56 N. The proposed customised implant was found suitable for Type ⅢA acetabulum bone loss, whereas the shape suitability and mechanical safety were verified for the worst case.

Conclusion: The shape of a customised implant suitable for Paprosky ⅢA type was designed. The shape suitability and mechanical safety were evaluated using finite element method analysis and bending tests. Clinical validation is required through subsequent clinical evaluation.