Andrew B. Robbins

Background: Inertial measurement units (IMUs) have potential to be inexpensive, portable sensors for collecting gait parameters and joint kinematics. Current validation protocols generally do not investigate IMU accuracy in measuring altered gait; therefore, they cannot assess an IMU’s ability to detect pathologies. The Stridelink IMU-based gait analysis device is intended for use in detecting and monitoring gait abnormalities, thus there is a need to evaluate the device’s accuracy under abnormal gait conditions. Research question: How well do measurements from the StrideLink IMU agree with motion capture (MoCap), particularly when gait is mechanically altered to simulate pathology? Methods: Twenty-eight healthy participants (ages 18-40) were analyzed during a one-minute tread-mill walk with Vicon MoCap and StrideLink. Tests were performed under normal and mechanically induced abnormal conditions (knee brace, walking boot). Equivalence testing and correlation analysis evaluated StrideLink’s accuracy against MoCap. Results: StrideLink showed statistical equivalence (within 5%) for average cadence, stride, swing, and stance times but not double support time. Many metrics were statistically equivalent (p < .001) despite induced abnormalities. Correlation analysis showed almost perfect agreement with MoCap for stride times, cadence, and stance. However, the abnormal gait protocol revealed nuances not observed in normal gait; specifically, the device underestimated swing time by ∼10 ms in knee brace restricted limbs. Significance: This study utilized mechanically induced gait abnormalities to assess the robustness of IMU measurements. Results indicate StrideLink yields valid temporal gait measurements comparable to reference systems, even under conditions of significant deviation, supporting the utility of using induced abnormalities for sensor validation.

Estimation of body segment inertial properties (BSIPs) is a crucial step in development of inverse dynamics models. The goal of this study was to develop predictive models to estimate the mass, center of mass, and inertia tensor of the hindlimbs of sheep using easily obtainable morphometric data. In addition, this study presents a more comprehensive and repeatable method for defining each hindlimb body segment when calculating BSIPs from CT data. CT scans from 16 sheep of varying age, weight, sex, and phenotype were used to develop predictive models to estimate the BSIPs of the pelvis, thigh, crus, metatarsus, and pastern segments. The predictive models developed enable investigators to create inverse dynamics models of sheep hindlimbs. These models are particularly informative and expand the use of ovine models of human musculoskeletal disease.

The goal of this work was to experimentally validate a computational model for TKRs to improve implant alignment accuracy and assess potential implant misalignment during preoperative planning. Initial validation of the model was achieved by comparing ligament strain energies between the computational model and a physical knee model comprised of bone and ligament analogues. Experimental validation would be considered met when the computational model strain energies were within 10% of the measured values for all six physical knees. Physical and computational knee models were created with six variations of implant alignment to test the robustness of the computational model. Strain energy errors were well within the 10% threshold across knee range of motion.

Bone fragments embedded in a rib of a mastodon ( Mammut americanum ) from the Manis site, Washington, were digitally excavated and refit to reconstruct an object that is thin and broad, has smooth, shaped faces that converge to sharp lateral edges, and has a plano-convex cross section. These characteristics are consistent with the object being a human-made projectile point. The 13,900-year-old Manis projectile point is morphologically different from later cylindrical osseous points of the 13,000-year-old Clovis complex. The Manis point, which is made of mastodon bone, shows that people predating Clovis made and used osseous weapons to hunt megafauna in the Pacific Northwest during the Bølling-Allerød.