Longitudinal Ultrasonographic Features and Predictors of Physical Therapy Outcomes in Infants With Congenital Muscular Torticollis and Sternocleidomastoid Muscle Mass: A Prospective Cohort Study

Background: Congenital muscular torticollis (CMT) with a sternocleidomastoid muscle (SCM) mass presents varying prognoses, yet early, quantifiable predictors of physical therapy (PT) outcomes remain inadequately defined. This study aimed to identify the predictors of PT outcomes and evaluate the clinical and ultrasonographic (US) features influencing PT duration in infants with CMT with an SCM mass. Methods: In this prospective cohort study, 153 infants (30 ± 15 days old) with CMT and SCM mass were enrolled. Clinical evaluation and US measurements were performed at the initial visit and at 2, 4, 6, and 12 months of age. The primary outcome was favorable outcome versus unfavorable outcome. Unfavorable outcome was defined as surgery, PT >1 year without further improvement, or persistent cervical range-of-motion limitation >5 degrees. PT duration was analyzed among favorable outcome cases. Results: Favorable outcome was achieved in 126 infants (82.4%), whereas 27 (17.6%) failed. >66% SCM length involvement was the strongest predictor of unfavorable outcome (92.6% in unfavorable vs. 45.2% in favorable; OR 15.23, P =0.010). Higher SCM thickness ratio at 2 months predicted unfavorable outcome (OR: 4.05, P =0.016). In the favorable outcome group, >66% length involvement was associated with significantly longer PT duration (B=0.201, P =0.004). Conversely, isolated sternal head involvement without clavicular head involvement was strongly associated with shorter PT duration (B=–0.229, P =0.008), and all such cases achieved favorable outcome. Conclusions: Greater SCM length involvement (>66%) and higher 2-month thickness ratio independently predict unfavorable outcome, whereas isolated sternal head involvement predicts shorter therapy duration. Early US evaluation at 2 months provides robust prognostic information and may guide individualized PT strategies in infants with CMT. Level of Evidence: Level II.