An orthotic helmet and methods for fabrication and use thereof. The orthotic is molded in situ on a growing infant's head for the treatment of plagiocephaly, postsurgical cranial molding, or other desired treatment plans. The helmet makes contact in areas where cranial shape and volume are adequate, and no contact in areas of planned cranial growth. The helmet includes a shell, a bladder system which can be filled with a viscoelastic expandable foam, a fastener and a retaining strap. In the areas of deficient cranial volume, a volume of modeling putty equivalent to the target growth volume is placed against the cranium, manually molded until the planned target volume and form have been attained, and the helmet is molded in place over this spacer material. The spacer is then removed, and the helmet is then worn continuously until resolution of the deformity or attainment of planned form is reached.
