Modeling of the pliant surfaces of the thigh and leg during gait

Kevin Arthur Ball; Michael Raymond Pierrynowski

doi:10.1117/12.308193

13 May 1998 Modeling of the pliant surfaces of the thigh and leg during gait

Kevin Arthur Ball, Michael Raymond Pierrynowski

Proceedings Volume 3254, Laser-Tissue Interaction IX; (1998) https://doi.org/10.1117/12.308193
Event: BiOS '98 International Biomedical Optics Symposium, 1998, San Jose, CA, United States

Abstract

Rigid Body Modeling, a 6 degree of freedom (DOF) method, provides state of the art human movement analysis, but with one critical limitation; it assumes segment rigidity. A non- rigid 12 DOF method, Pliant Surface Modeling (PSM) was developed to model the simultaneous pliant characteristics (scaling and shearing) of the human body's soft tissues. For validation, bone pins were surgically inserted into the tibia and femur of three volunteers. Infrared markers (44) were placed upon the thigh, leg, and bone pin surfaces. Two synchronized OPTOTRAK/3020^TM cameras (Northern Digital Inc., Waterloo, ON) were used to record 120 seconds of treadmill gait per subject. In comparison to the 'gold standard' bone pin rotational results, PSM located the tibia, femur and tibiofemoral joint with root mean square (RMS) errors of 2.4 degrees, 4.0 degrees and 4.6 degrees, respectively. These performances met or exceeded (P less than .01) the current state of the art for surface data, Rigid Surface Modeling. The thigh's measured surface experienced uniform repeatable changes in scale: 40% mediolateral, 5% anterioposterior, 5% superioinferior, and planar shears of: 25 degrees transverse, 15 degrees sagittal, 5 degrees frontal. With the brief exception of push-off, the lower leg demonstrated much greater rigidity: less than 5% scaling and less than 5 degrees shearing. Thus, PSM offers superior 'rigid' estimates of knee motion with the ability to quantify 'pliant' surface changes.

Citation Download Citation

Kevin Arthur Ball and Michael Raymond Pierrynowski "Modeling of the pliant surfaces of the thigh and leg during gait", Proc. SPIE 3254, Laser-Tissue Interaction IX, (13 May 1998); https://doi.org/10.1117/12.308193

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