title: Efficient computational method for assessing the effects of implant positioning in cementless total hip replacements.
abstract: The present work describes a statistical investigation into the effects of implant positioning on the initial stability of a cementless total hip replacement (THR). Mesh morphing was combined with design of computer experiments to automatically construct Finite Element (FE) meshes for a range of pre-defined femur-implant configurations and to predict implant micromotions under joint contact and muscle loading. Computed micromotions, in turn, are postprocessed using a Bayesian approach to: (a) compute the main effects of implant orientation angles, (b) predict the sensitivities of the considered implant performance metrics with respect to implant ante-retroversion, varus-valgus and antero-posterior orientation angles and (c) identify implant positions that maximise and minimise each metric. It is found that the percentage of implant area with micromotion greater than 50 μm, average and maximum micromotions are all more sensitive to antero-posterior orientation than ante-retroversion and varus-valgus orientation. Sensitivities, combined with the main effect results, suggest that bone is less likely to grow if the implant is increasingly moved from the neutral position towards the anterior part of the femur, where the highest micromotions occur. The computed implant best position leads to a percentage of implant area with micromotion greater than 50 μm of 1.14 when using this metric compared to 14.6 and 5.95 in the worst and neutrally positioned implant cases. In contrast, when the implant average/maximum micromotion is used to assess the THR performance, the implant best position corresponds to average/maximum micromotion of 9 μm/59 μm, compared to 20 μm/114 μm and 13 μm/71 μm in the worst and neutral positions, respectively. The proposed computational framework can be extended further to study the effects of uncertainty and variability in anatomy, bone mechanical properties, loading or bone-implant interface contact conditions.
authors.affiliation: Bioengineering Sciences Research Group, School of Engineering Sciences, University of Southampton, Highfield, Southampton SO17 1BJ, UK.
authors.forename: Mamadou T
authors.initials: MT
authors.lastname: Bah
authors.forename: Prasanth B
authors.initials: PB
authors.lastname: Nair
authors.forename: Mark
authors.initials: M
authors.lastname: Taylor
authors.forename: Martin
authors.initials: M
authors.lastname: Browne
mesh_terms: D019644:Arthroplasty, Replacement, Hip / Q000379:methods*; D001499:Bayes Theorem; D001696:Biomechanical Phenomena; D001843:Bone Cements; D003198:Computer Simulation; D005269:Femur / Q000502:physiology*; D020342:Finite Element Analysis; D006615:Hip / Q000503:physiopathology; D006621:Hip Joint / Q000502:physiology; D006622:Hip Prosthesis; D006801:Humans; D015233:Models, Statistical; D009068:Movement; D016011:Normal Distribution; D019736:Prostheses and Implants; D011474:Prosthesis Design
chemical_list: D001843:Bone Cements