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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

Specimen mounted in the RTP. This image shows clearance between the heel and X-Y table as the AT load is applied, allowing unconstrained arch formation.
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fig3: Specimen mounted in the RTP. This image shows clearance between the heel and X-Y table as the AT load is applied, allowing unconstrained arch formation.

Mentions: Potted specimens were clamped securely in a mounting block and rigidly connected to the testing platform. A sagittal plane was established for each specimen by bisecting the second metatarsal and AT [11, 13, 17] with a vertical axis aligned with the tibia that matched the X-Z plane of the testing platform. A static AT force vector (Fa) was applied via a cable-pulley system designed to minimize friction to within four degrees of the vertical tibia axis, while the heel was raised approximately 50 mm and the X-Y table was unlocked (Figure 3). This feature allowed for unconstrained arch formation while transferring loads from the tibia to the calcaneus and maintaining foot support throughout the gait simulation [31, 32]. The heel was then returned to the neutral position and an axial tibia force (Ft) was applied to the specimen to meet the desired vertical ground reaction force (vGRF) condition within a prescribed ±2 N tolerance. After the desired loading condition was met, the X-Y table was locked and the rotation of the specimen was started.


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)

Specimen mounted in the RTP. This image shows clearance between the heel and X-Y table as the AT load is applied, allowing unconstrained arch formation.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

fig3: Specimen mounted in the RTP. This image shows clearance between the heel and X-Y table as the AT load is applied, allowing unconstrained arch formation.
Mentions: Potted specimens were clamped securely in a mounting block and rigidly connected to the testing platform. A sagittal plane was established for each specimen by bisecting the second metatarsal and AT [11, 13, 17] with a vertical axis aligned with the tibia that matched the X-Z plane of the testing platform. A static AT force vector (Fa) was applied via a cable-pulley system designed to minimize friction to within four degrees of the vertical tibia axis, while the heel was raised approximately 50 mm and the X-Y table was unlocked (Figure 3). This feature allowed for unconstrained arch formation while transferring loads from the tibia to the calcaneus and maintaining foot support throughout the gait simulation [31, 32]. The heel was then returned to the neutral position and an axial tibia force (Ft) was applied to the specimen to meet the desired vertical ground reaction force (vGRF) condition within a prescribed ±2 N tolerance. After the desired loading condition was met, the X-Y table was locked and the rotation of the specimen was started.

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