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Normative Achilles and patellar tendon shear wave speeds and loading patterns during walking in typically developing
Anahid Ebrahimi1, Robyn L Kuchler1, Robin L Pomeroy1
1Department of Mechanical Engineering, University of Wisconsin-Madison, Madison, WI, USA.
Insights
Shear wave tensiometry measured Achilles and patellar tendon forces in children during walking. Tendon loading increased with walking speed, providing normative data for gait analysis in children with cerebral palsy.
Area of Science:
- Biomechanics
- Pediatric Gait Analysis
- Musculoskeletal Research
Background:
- Gait disorders in children with cerebral palsy are often assessed using motion analysis.
- Inferring muscle-tendon forces from joint kinetics alone is challenging.
- Shear wave tensiometry offers a novel method to directly measure tendon forces during dynamic activities.
Purpose of the Study:
- To investigate the modulation of Achilles and patellar tendon forces with varying walking speeds in typically developing children.
- To establish normative data for tendon loading during gait using shear wave tensiometry.
- To explore the potential of this technique for identifying abnormal tendon loading in pediatric populations.
Main Methods:
- Twelve typically developing children (9-16 years old) participated.
- Shear wave tensiometers were placed on Achilles and patellar tendons.
- Tendon wave speeds were recorded at five normalized walking speeds.
- Tendon forces were estimated using a calibrated wave speed-load relationship.
Main Results:
- Achilles and patellar tendon forces exhibited two peaks per gait cycle.
- Peak Achilles tendon force aligned with push-off, with less speed modulation.
- A second, speed-dependent Achilles loading peak occurred in late swing.
- Patellar tendon loading peaks corresponded to knee extension moments and increased with walking speed.
Conclusions:
- This study provides the first characterization of Achilles and patellar tendon loading during gait in children using shear wave tensiometry.
- The findings establish normative tendon force data across different walking speeds.
- These normative data can aid in identifying aberrant tendon loading patterns in pediatric gait disorders.
Background:
Motion analysis is commonly used to evaluate joint kinetics in children with cerebral palsy who exhibit gait disorders. However, one cannot readily infer muscle-tendon forces from joint kinetics. This study investigates the use of shear wave tensiometry to characterize Achilles and patellar tendon forces during gait.
Research Question:
How do Achilles and patellar tendon wave speed and loading modulate with walking speed in typically developing children?
Methods:
Twelve typically developing children (9-16 years old) walked on an instrumented treadmill with shear wave tensiometers over their Achilles (n = 11) and patellar (n = 9) tendons. Wave speeds were recorded at five leg length-normalized walking speeds (very slow to very fast). Achilles and patellar tendon moment arms were measured with synchronized ultrasound and motion capture. The tendon wave speed-load relationship was calibrated at the typical walking speed and used to estimate tendon loading at other walking speeds.
Results:
Characteristic Achilles and patellar tendon wave speed trajectories exhibited two peaks over a gait cycle. Peak Achilles tendon force closely aligned with peak ankle plantarflexor moment during pushoff, though force exhibited less modulation with walking speed. A second peak in late swing Achilles loading, which was not evident from the ankle moment, increased significantly with walking speed (p < 0.001). The two peaks in patellar tendon loading occurred at 12 ± 1% and 68 ± 6% of the gait cycle, matching the timing of peak knee extension moment in early stance and early swing. Both patellar tendon load peaks increased significantly with walking speed (p < 0.05).
Significance:
This is the first study to use shear wave tensiometry to characterize Achilles and patellar tendon loading during gait in children. These data could serve as a normative comparison when using tensiometry to identify abnormal tendon loading patterns in individuals who exhibit equinus and/or crouch gait.
