Floating bone phenomenon in Pierre Robin Sequence

After a failed mandibular osteodistraction, the wrong positioned mandible of a few patients with Pierre Robin sequence returned in the most functional position and regained a proper symmetry, without external intervention. The study aims to explain this self-adjustment and introduce the floating bone phenomenon.The inclusion criteria were severe micrognathia, Fast and Early Mandibular Distraction Osteogenesis protocol, postoperative mandibular wrong positioning, presurgery, immediate postsurgery, and long-term computed tomography scan. Five patients were included. The considered parameters were the distance between mandibular dental centerline and midsagittal facial axis, the rotation of the mandibular body, the magnitude of elongation, and the lowering of the mandibular body.Three patients went from a decentralization >4 mm in the activation phase to a normalization of the said value in the follow-up. In the same period, the interincisal point of 2 patients moved respectively from 0.5 mm on the left and 0.8 mm on the right to 1.2 mm and 1.6 mm on the right, respectively. The rotation of the mandibular body was meanly 25.6° among all patients. The mean value of the distraction was 14.1 mm. A difference of about 4.4 mm between the left and the right side was measured. The lowering of the mandible varied between 2.8 and 12.6 mm.All patients improved their symmetry. Four of them improved in all the measured parameters, while 1 patient presented a worsening in the decentralization of the interincisal point.The floating bone phenomenon could break new grounds in the management of patients with Pierre Robin sequence.