Subject-specific finite element models (FEMs) of the shoulder complex are commonly used to predict differences in internal load distribution due to injury, treatment or disease. However, these models rely on various underlying assumptions, and although experimental validation is warranted, it is difficult to obtain and often not performed. The goal of the current study was to quantify the accuracy of local displacements predicted by subject-specific QCT-based FEMs of the scapula, compared to experimental measurements obtained by combining digital volume correlation (DVC) and mechanical loading of cadaveric specimens within a microCT scanner. Four cadaveric specimens were loaded within a microCT scanner using a custom-designed six degree-of-freedom hexapod robot augmented with carbon fiber struts for radiolucency. BoneDVC software was used to quantify full-field experimental displacements between pre-and post-loaded scans. Corresponding scapula QCT-FEMs were generated and three types of boundary conditions (BC) (idealized-displacement, idealized-force, and DVC-derived) were simulated for each specimen. DVC-derived BCs resulted in the closest match to the experimental results for all specimens (best agreement: slope ranging from 0.87-1.09; highest correlation: r 2 ranging from 0.79-1.00). In addition, a two orders of magnitude decrease was observed in root-mean-square error when using QCT-FEMs with simulated DVC-derived BCs compared to idealizeddisplacement and idealized-force BCs. The results of this study demonstrate that scapula QCT-FEMs can accurately predict local experimental full-field displacements if the BCs are derived from DVC measurements.

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The experimental quantification of the process parameters associated with bone burring represents a desirable outcome both from the perspective of an optimized surgical procedure as well as that of a future implementation into the design of closed-loop controllers used in robot-assisted bone removal operations. Along these lines, the present study presents an experimental investigation of the effects that tool type, rotational speed of the tool, depth of cut, feed rate, cutting track overlap, and tool angle (to a total of 864 total unique combinations) have on bone temperature, tool vibration, and cutting forces associated with superficial bone removal operations. The experimental apparatus developed for this purpose allowed a concurrent measurement of bone temperature, tool vibration, and cutting forces as a function of various process parameter combinations. A fully balanced experimental design involving burring trials performed on a sawbone analog was carried out to establish process trends and subsets leading to local maximums and minimums in temperature and vibration were further investigated. Among the parameters tested, a spherical burr of 6 mm turning at 15,000 r/min and advancing at 2 mm/s with a 50% overlap between adjacent tool paths was found to yield both low temperatures at the bone/tool interface and minimal vibrations. This optimal set of parameters enables a versatile engagement between tool and bone without sacrificing the optimal process outcomes.

Osteoarthritis (OA) is characterized by morphological changes that alter bone structure and mechanical properties. This study compared bone morphometric parameters and apparent modulus between humeral heads excised from end‐stage OA patients undergoing total shoulder arthroplasty (n = 28) and non‐pathologic normal cadavers (n = 28). Morphometric parameters were determined in central cores, with regional variations compared in four medial to lateral regions. Linear regression compared apparent modulus, morphometric parameters, and age. Micro finite element models estimated trabecular apparent modulus and derived density–modulus relationships. Significant differences were found for bone volume fraction (p < 0.001) and trabecular thickness (p < 0.001) in the most medial regions. No significant differences occurred between morphometric parameters and apparent modulus or age, except in slope between groups for apparent modulus versus trabecular number (p = 0.021), and in intercept for trabecular thickness versus age (p = 0.040). Significant differences occurred in both slope and intercept between density–modulus regression fits for each group (p ≤ 0.001). The normal group showed high correlations in the power‐fit (r2 = 0.87), with a lower correlation (r2 = 0.61) and a more linear relationship, in the OA group. This study suggests that alterations in structure and apparent modulus persist mainly in subchondral regions of end‐stage OA bone. As such, if pathologic regions are removed during joint replacement, computational models that utilize modeling parameters from non‐pathologic normal bone may be applied to end‐stage OA bone. An improved understanding of humeral trabecular bone variations has potential to improve the surgical management of end‐stage OA patients. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 38:503–509, 2020