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Updated: Oct 23, 2025
Methods for In Vivo Biomechanical Testing on Brachial Plexus in Neonatal Piglets
Published on: December 19, 2019
Location of brachial plexus birth injury affects functional outcomes in a rat model
Raveena M Doshi1, Monique Y Reid2,3, Nikhil N Dixit1
1Department of Mechanical and Aerospace Engineering, North Carolina State University, Raleigh, North Carolina, United States.
Insights
Brachial plexus birth injury (BPBI) impairs limb movement. This study found compensatory strategies in rats, suggesting functional movement analysis is key for BPBI treatment.
Area of Science:
- Biomechanical Engineering
- Neuroscience
- Orthopedics
Background:
- Brachial plexus birth injury (BPBI) often leads to shoulder and elbow paralysis.
- Common sequelae include shoulder internal rotation and elbow flexion contractures.
Purpose of the Study:
- To develop a method for measuring functional movement after BPBI.
- To investigate how injury location (preganglionic vs. postganglionic) affects functional outcomes in a rat model.
Main Methods:
- Integrated gait analysis with musculoskeletal modeling and simulation in rats post-BPBI.
- Extracted sagittal plane shoulder and elbow angles from gait recordings.
- Measured muscle architecture and simulated gait to determine muscle fiber lengths.
Main Results:
- The preganglionic neurectomy group showed significantly reduced stance time, elbow flexion, and shoulder protraction.
- No significant linear relationship was found between passive shoulder external rotation and functional shoulder protraction.
- Normalized functional muscle fiber excursions did not significantly differ between groups, despite restricted growth.
Conclusions:
- BPBI rat models exhibit compensatory motor control strategies during locomotion.
- Functional and passive movement assessments may yield substantially different outcomes in BPBI.
- Emphasizing functional movement analysis is crucial for effective BPBI treatment.
Abstract:
Brachial plexus birth injury (BPBI) results in shoulder and elbow paralysis with shoulder internal rotation and elbow flexion contracture as frequent sequelae. The purpose of this study was to develop a technique for measuring functional movement and examine the effect of brachial plexus injury location (preganglionic and postganglionic) on functional movement outcomes in a rat model of BPBI, which we achieved through integration of gait analysis with musculoskeletal modeling and simulation. Eight weeks following unilateral brachial plexus injury, sagittal plane shoulder and elbow angles were extracted from gait recordings of young rats (n = 18), after which rats were sacrificed for bilateral muscle architecture measurements. Musculoskeletal models reflecting animal-specific muscle architecture parameters were used to simulate gait and extract muscle fiber lengths. The preganglionic neurectomy group spent significantly less (p = 0.00116) time in stance and walked with significantly less (p < 0.05) elbow flexion and shoulder protraction in the affected limb than postganglionic neurectomy or control groups. Linear regression revealed no significant linear relationship between passive shoulder external rotation and functional shoulder protraction range of motion. Despite significant restriction in longitudinal muscle growth, normalized functional fiber excursions did not differ significantly between groups. In fact, when superimposed on a normalized force-length curve, neurectomy-impaired muscle fibers (except subscapularis) accessed regions of the curve that overlapped with the control group. Our results suggest the presence of compensatory motor control strategies during locomotion following BPBI. The clinical implications of our findings support emphasis on functional movement analysis in treatment of BPBI, as functional and passive outcomes may differ substantially.
