Relationship between glenoid deformity and gait characteristics in a rat model of neonatal brachial plexus injury.

UNLABELLED: Neonatal brachial plexus injury (NBPI) results in substantial postural and functional impairments associated with underlying muscular and osseous deformities. We examined the relationship between glenoid deformity severity and gait in a rat model of NBPI, an established model for studying the in vivo pathomechanics of NBPI. At 8 weeks post-operatively, we monitored the gait of 24 rat pups who exhibited varying degrees of glenoid deformity following unilateral brachial plexus neurectomy and chemodenervation interventions administered 5 days postnatal. Five basic stride and stance metrics were calculated for the impaired forelimbs over four consecutive gait cycles. Bilateral differences in glenoid version (ΔGAv ) and inclination (ΔGAi ) angles were computed from data for the same rats as reported in a previous study. A linear regression model was generated for each deformity-gait pair to identify significant relationships between the two. ΔGAv was not significantly correlated with any gait measurements, while ΔGAi significantly correlated with all five gait measurements. Specifically, ΔGAi was significantly positively correlated with stride length (R2  = 0.38, p = 0.001) and stance factor (R2  = 0.45, p < 0.001), and significantly negatively correlated with stance width (R2  = 0.24, p = 0.016), swing/stance ratio (R2  = 0.17, p = 0.046), and stride frequency (R2  = 0.33, p = 0.003). Rats with declined glenoids exhibited the most altered gait.

CLINICAL SIGNIFICANCE: Our findings link musculoskeletal changes and functional outcomes in an NBPI rat model. Thus, gait analysis is a potentially useful, non-invasive, quantitative way to investigate the effects of injury and deformity on limb function in the NBPI rat model. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:1991-1997, 2018.