LiDAR-based scaling of OpenSim musculoskeletal human models is a viable alternative to marker-based approaches - A preliminary study

Biomechanical analysis is increasingly being undertaken in field-based settings, often using inertial sensors or video-based pose estimation. These advancements necessitate more practical and accessible scaling methods as alternatives to traditional laboratory-based techniques like optical marker-based scaling. LiDAR scanning is a technique that could provide a reliable and efficient means of scaling biomechanical models. This study tested a scaling method for OpenSim models and comparing outcomes with those of traditional marker-based scaling in healthy adult participants. An anatomical skeleton was inferred from a LiDAR scan taken with an iPad. Key skeletal landmarks were then used to generate scaling factors using statistical shape models. The scaling factors of the pelvis, femur and tibia body segments derived from the LiDAR-based method demonstrated excellent reliability, with repeated scans of seven subjects producing an ICC value of 0.961. When comparing the scaling factors of eight additional subjects with the current gold standard technique of marker-based optical motion capture, a Bland-Altman analysis revealed differences of -0.5% ± 5.3 (95CI = [-10.8, 10]). Joint kinematics calculated using LiDAR scaled models had an average RMSD of 3.7° ± 0.1°when compared with those calculated with a marker-scaled model. These results indicate that a LiDAR-based scaling method can address the challenge of accurate and reliable scaling methods that are practical for use in the field. Future work with larger cohorts and diverse populations, and scaling of other body segments will provide further validation and enhance the generalizability and robustness of this approach.