Predicting motor outcomes with 3 month prone hip angles in premature infants.

Purpose: This study used kinematic analysis to identify a reliable and rapid assessment method for abnormal patterns of motor development in preterm infants.

Methods: In a retrospective analysis, we examined video of n= 35 preterm infants at 3mo corrected age (CA) who had concurrent Test of Infant Motor Performance (TIMP) scores. Hyperflexion at the hip produces common gait anomalies seen in children with CP, therefore we analyzed hip angle in the prone head lift position at 3 months CA. Magnetic Resonance Spectroscopy (MRS) was performed at term equivalent (n= 23) and Bayley-III neurodevelopmental tests were performed at 1 year (n= 28). We correlated hip angles with TIMP and Bayley-III scores, and MRS neuronal metabolites.

Results: Hip angle positively correlated with TIMP at 3 months (r= 0.642, p≤ 0.001), but not with Bayley-III at 1 year (r= 0.122, p= 0.529). Hip angle correlated negatively with myo-inositol (mI) ratios in frontal white matter tracts (mI/Cr r= -0.520, p= 0.011).

Conclusions: These results suggest prone hip angle may be a quantitative proxy for the 42-item TIMP at 3 months, and that hypertonicity in the hip flexor musculature is a manifestation of white matter metabolic abnormalities (elevated mI ratios) that may indicate occult white matter injury.