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Development of a Robotic Assembly for Analyzing the Instantaneous Axis of Rotation of the Foot Ankle Complex.

Salb KN, Wido DM, Stewart TE, DiAngelo DJ - Appl Bionics Biomech (2016)

Bottom Line: Mean ATLs and IAR values were not significantly different between cycles of motion, but IAR values were significantly different between dorsiflexion and plantar flexion.A linear regression analysis showed no significant differences between slopes of plantar flexion paths.The customized robotic platform and advanced testing protocol produced repeatable and accurate measurements of the IAR, useful for assessing foot ankle biomechanics under different loading scenarios and foot conditions.

View Article: PubMed Central - PubMed

Affiliation: BioRobotics Laboratory, Department of Orthopaedic Surgery and Biomedical Engineering, The University of Tennessee Health Science Center, 956 Court Avenue, Suite E226, Memphis, TN 38163, USA.

ABSTRACT
Ankle instantaneous axis of rotation (IAR) measurements represent a more complete parameter for characterizing joint motion. However, few studies have implemented this measurement to study normal, injured, or pathological foot ankle biomechanics. A novel testing protocol was developed to simulate aspects of in vivo foot ankle mechanics during mid-stance gait in a human cadaveric specimen. A lower leg was mounted in a robotic testing platform with the tibia upright and foot flat on the baseplate. Axial tibia loads (ATLs) were controlled as a function of a vertical ground reaction force (vGRF) set at half body weight (356 N) and a 50% vGRF (178 N) Achilles tendon load. Two specimens were repetitively loaded over 10 degrees of dorsiflexion and 20 degrees of plantar flexion. Platform axes were controlled within 2 microns and 0.008 degrees resulting in ATL measurements within ±2 N of target conditions. Mean ATLs and IAR values were not significantly different between cycles of motion, but IAR values were significantly different between dorsiflexion and plantar flexion. A linear regression analysis showed no significant differences between slopes of plantar flexion paths. The customized robotic platform and advanced testing protocol produced repeatable and accurate measurements of the IAR, useful for assessing foot ankle biomechanics under different loading scenarios and foot conditions.

No MeSH data available.


Related in: MedlinePlus

The “ankle coordinate frame” designated to plot the IAR on individual specimen. It was defined as the intersection of bisector of the tibia and the highest point on the tibial mortise.
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fig7: The “ankle coordinate frame” designated to plot the IAR on individual specimen. It was defined as the intersection of bisector of the tibia and the highest point on the tibial mortise.

Mentions: Force and positional data were sampled at 20 Hz. A modified set of equations originally derived by Crisco III et al. [33] were applied to the NTT rotational and positional data for each increment of rotation to calculate the IAR of the ankle in the sagittal plane. Unlike previous studies that used positional data from camera targets or radiographs to calculate the IAR [7, 24], this study used the positional data from the robot to determine the IAR values. In doing so, the overall error in the IAR calculations of the entire testing system (including the testing frame, actuator, gimbal assembly, mounting fixtures, and load cell) was within ±0.050 mm for loads up to 1000 N. The path of the IAR was plotted back onto the specimen and expressed relative to an “ankle coordinate frame” that was defined by the bisector of the tibia and highest point on the tibial mortise in the initial neutral vertical orientation (Figure 7). The same process used to determine the location of the pARA and fixture reference point (Figure 2) was used to locate the ankle coordinate frame.


Development of a Robotic Assembly for Analyzing the Instantaneous Axis of Rotation of the Foot Ankle Complex.

Salb KN, Wido DM, Stewart TE, DiAngelo DJ - Appl Bionics Biomech (2016)

The “ankle coordinate frame” designated to plot the IAR on individual specimen. It was defined as the intersection of bisector of the tibia and the highest point on the tibial mortise.
© Copyright Policy - open-access
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC4821921&req=5

fig7: The “ankle coordinate frame” designated to plot the IAR on individual specimen. It was defined as the intersection of bisector of the tibia and the highest point on the tibial mortise.
Mentions: Force and positional data were sampled at 20 Hz. A modified set of equations originally derived by Crisco III et al. [33] were applied to the NTT rotational and positional data for each increment of rotation to calculate the IAR of the ankle in the sagittal plane. Unlike previous studies that used positional data from camera targets or radiographs to calculate the IAR [7, 24], this study used the positional data from the robot to determine the IAR values. In doing so, the overall error in the IAR calculations of the entire testing system (including the testing frame, actuator, gimbal assembly, mounting fixtures, and load cell) was within ±0.050 mm for loads up to 1000 N. The path of the IAR was plotted back onto the specimen and expressed relative to an “ankle coordinate frame” that was defined by the bisector of the tibia and highest point on the tibial mortise in the initial neutral vertical orientation (Figure 7). The same process used to determine the location of the pARA and fixture reference point (Figure 2) was used to locate the ankle coordinate frame.

Bottom Line: Mean ATLs and IAR values were not significantly different between cycles of motion, but IAR values were significantly different between dorsiflexion and plantar flexion.A linear regression analysis showed no significant differences between slopes of plantar flexion paths.The customized robotic platform and advanced testing protocol produced repeatable and accurate measurements of the IAR, useful for assessing foot ankle biomechanics under different loading scenarios and foot conditions.

View Article: PubMed Central - PubMed

Affiliation: BioRobotics Laboratory, Department of Orthopaedic Surgery and Biomedical Engineering, The University of Tennessee Health Science Center, 956 Court Avenue, Suite E226, Memphis, TN 38163, USA.

ABSTRACT
Ankle instantaneous axis of rotation (IAR) measurements represent a more complete parameter for characterizing joint motion. However, few studies have implemented this measurement to study normal, injured, or pathological foot ankle biomechanics. A novel testing protocol was developed to simulate aspects of in vivo foot ankle mechanics during mid-stance gait in a human cadaveric specimen. A lower leg was mounted in a robotic testing platform with the tibia upright and foot flat on the baseplate. Axial tibia loads (ATLs) were controlled as a function of a vertical ground reaction force (vGRF) set at half body weight (356 N) and a 50% vGRF (178 N) Achilles tendon load. Two specimens were repetitively loaded over 10 degrees of dorsiflexion and 20 degrees of plantar flexion. Platform axes were controlled within 2 microns and 0.008 degrees resulting in ATL measurements within ±2 N of target conditions. Mean ATLs and IAR values were not significantly different between cycles of motion, but IAR values were significantly different between dorsiflexion and plantar flexion. A linear regression analysis showed no significant differences between slopes of plantar flexion paths. The customized robotic platform and advanced testing protocol produced repeatable and accurate measurements of the IAR, useful for assessing foot ankle biomechanics under different loading scenarios and foot conditions.

No MeSH data available.


Related in: MedlinePlus