Key result
Classical homogenized finite element methods excellently correlated with refined microfinite element predictions for evaluating bone anchor fixation stiffness, which was stiffened by cement augmentation.
Homogenized finite element modeling is a usable method for evaluating bone anchor fixation stiffness, which is influenced by bone density and cement augmentation.
Supports simplified FE modeling for preclinical bone anchor evaluation; leaves open clinical translation and human validation.
Bone quality is one of the reported factors influencing the success of bone anchors in arthroscopic repairs of torn rotator cuffs at the shoulder. This work was aimed at developing refined numerical methods to investigate how bone quality can influence the fixation stiffness of bone anchors. To do that bone biopsies were scanned at 26-μm resolution with a high-resolution microcomputer tomography (micro-CT) scanner and their images were processed for virtual implantation of a typical design of bone anchor. These were converted to microfinite element (μFE) and homogenized classical FE models, and analyses were performed to simulate pulling on the bone anchor with and without cement augmentation. Quantification of structural stiffness for each implanted specimen was then computed, as well as stress distributions within the bone structures, and related to the bone volume fraction of the specimens. Results show that the classical method is excellently correlated to structural predictions of the more refined μFE method, despite the qualitative differences in local stresses in the bone surrounding the implant. Predictions from additional loading cases suggest that structural fixation stiffness in various directions is related to apparent bone density of the surrounding bone. Augmentation of anchoring with bone cement stiffens the fixation and alters these relations. This work showed the usability of homogenized FE (hFE) in the evaluation of bone anchor fixation and will be used to develop new methodologies for virtual investigations leading to optimized repairs of rotator cuff and glenoid Bankart lesions.
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Yan Chevalier (2015) studied Torn rotator cuffs. Virtual implantation of bone anchor with cement augmentation vs. Without cement augmentation was evaluated on Fixation stiffness and stress distributions. Classical homogenized finite element methods excellently correlated with refined microfinite element predictions for evaluating bone anchor fixation stiffness, which was stiffened by cement augmentation.
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