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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

IAR paths of specimen 1 during dorsiflexion and plantar flexion plotted on medial radiographs. Mean IAR values for all three cycles (circles) with standard deviations (too small to see) are shown. Dashed arrows denote the direction of the IAR through rotation.
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fig8: IAR paths of specimen 1 during dorsiflexion and plantar flexion plotted on medial radiographs. Mean IAR values for all three cycles (circles) with standard deviations (too small to see) are shown. Dashed arrows denote the direction of the IAR through rotation.

Mentions: The final 3 cycles of IAR pathways are plotted relative to the ankle coordinate frame for specimen 1 (Figure 8) and specimen 2 (Figure 9) along with mean IAR values and standard deviations. The IAR represents a moving axis of rotation due to the joint articular geometry and surrounding soft tissue structures. Dorsiflexion paths show little movement in the talus, remaining within a 4.5 mm range (i.e., 2 mm in X and 4 mm in Z). In plantar flexion, the first degrees of motion started up within the articular surface of the talus. As rotation continued, the IAR path moved downward towards the middle of the talus. The plantar flexion IAR path had a maximum range of approximately 21 mm (i.e., 20 mm in Z and 6 mm in X). A linear regression analysis was performed on the plantar flexion paths. The slopes of the IAR paths for dorsiflexion testing are listed in Table 4. No statistical differences were found between the slopes for specimen 1 (P = 0.7823) or specimen 2 (P = 0.0826).


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)

IAR paths of specimen 1 during dorsiflexion and plantar flexion plotted on medial radiographs. Mean IAR values for all three cycles (circles) with standard deviations (too small to see) are shown. Dashed arrows denote the direction of the IAR through rotation.
© Copyright Policy - open-access
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC4821921&req=5

fig8: IAR paths of specimen 1 during dorsiflexion and plantar flexion plotted on medial radiographs. Mean IAR values for all three cycles (circles) with standard deviations (too small to see) are shown. Dashed arrows denote the direction of the IAR through rotation.
Mentions: The final 3 cycles of IAR pathways are plotted relative to the ankle coordinate frame for specimen 1 (Figure 8) and specimen 2 (Figure 9) along with mean IAR values and standard deviations. The IAR represents a moving axis of rotation due to the joint articular geometry and surrounding soft tissue structures. Dorsiflexion paths show little movement in the talus, remaining within a 4.5 mm range (i.e., 2 mm in X and 4 mm in Z). In plantar flexion, the first degrees of motion started up within the articular surface of the talus. As rotation continued, the IAR path moved downward towards the middle of the talus. The plantar flexion IAR path had a maximum range of approximately 21 mm (i.e., 20 mm in Z and 6 mm in X). A linear regression analysis was performed on the plantar flexion paths. The slopes of the IAR paths for dorsiflexion testing are listed in Table 4. No statistical differences were found between the slopes for specimen 1 (P = 0.7823) or specimen 2 (P = 0.0826).

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