Amélioration et évaluation d'une prothèse d'essai acétabulaire à diamètre variable

Abstract

Total hip arthroplasty (THA) is indicated for patients with severe hip degradation in arder to recover mobility and to reduce pain. With intent to reduce cleaning, sterilisation, storing and purchase costs of surgical instruments used during THA, a new variable diameter trial liner (VDTL) has been designed. This tool consists of a deployment mechanism and interchangeable bearing parts allowing the modification of its own dimension. This way, it can replace 66 of the currently used trial liners (TL). The main objective of this thesis is to improve and to evaluate the design of a previously proposed solution. Three specifie objectives are proposed to reach the main objective: 1- to improve VDTL design in arder to improve its functionality, 2- to evaluate the range of motion (ROM) allowed by the VDTL and 3- to evaluate the mechanical strength of the VDTL. Improvements of the VDTL allow increasing its mechanical strength by a factor of 2, increasing the deployment mechanism functionality and precision and obtaining an efficient bearing parts locking system. ROM was estimated with kinematic simulations and validated from experimental testing. Results show constant VDTL ROM while TLs present a variable ROM in function of femoral head size. Also, VDTL ROM is, on average, 5 % less than conventional TLs ROM. Evaluation of the VDTL mechanical strength was performed with finite element models where three loading conditions were reproduced. The numerical models were validated with experimental mechanical testing on a prototype of the VDTL. Results of this study suggest an insufficient mechanical strength of the VDTL. The weakest part of the VDTL shows bending stresses, under hypothesis of linear material behavior, of 1117 MPa while the established threshold is 750 MPa. Furthermore, the analysis of VDTL displacements during loading revealed the existence of a loading condition more critical than the ones simulated in this project. The analysis of results leads to the establishment of new design criteria which will manage the upcoming optimisation process of the VDTL. Moreover, this project allowed development of an evaluation method for the VDTL ROM and mechanical strength. Recommendations of this project concern the improvement of this method for the validation of the next generation of DVTL. Lastly, this project underlines the potential of the VDTL and the relevance to continue its development in arder to bring to an end this cutting edge technology.

Date	9 Mar 2010
Original language	French
Awarding Institution	École de technologie supérieure
Supervisor	Yvan Petit (Supervisor) & Julio Fernandes (Co-supervisor)