Still photography is a reliable method for measuring habitual head deviation from midline in infants with CMT. Several modifications to the measurement procedure have been suggested.

Purpose: To describe the development of the Functional Symmetry Observation Scale (FSOS) Version 2 and its content validation. Methods: The FSOS Version 2 is an observational assessment that quantifies symmetry in spontaneous movement and posture in infants with congenital muscular torticollis, age birth to 18 months. Twenty expert pediatric physical therapists were identified through purposive sampling and invited to participate in a modified Delphi study. Survey data were collected on Qualtrics. Consensus was evaluated using median ratings and percent agreement on Likert Scale items. Thematic analysis was performed for open-ended question responses. Results: Thirteen experts completed Round 1 and 2 surveys. In Round 1, consensus was achieved on all but 1 item. The scale was modified based on received feedback. In Round 2, consensus was achieved on all items (median rating of 4, agreement at 85%-100%). Conclusions: This study established the content validity of the FSOS Version 2.