Floating bone phenomenon in pierre robin sequence: from a failure to a new concept

Background: The Pierre Robin Sequence (PRS) is characterized by micrognathia, glossoptosis and airways obstruction. The fast and early mandibular distraction osteogenesis (FEMOD) is an effective procedure in the management ofpatients diagnosed with severe Pierre Robin Sequence. Objectives: Aim of the study is to introduce the “Floating Bone Phenomenon”. The authors noticed in few patients with wrong positioning ofthe distracted fragments the tendency ofthe mandible to return in the most functional position and regain a proper symmetry, avoiding an extra corrective intervention. Methods: Inclusion criteria were severe micrognathia, FEMOD protocol, post-operative mandibular wrong positioning and pre-surgery, short and long-term maxillofacial CT-scan. Five patients were included. The considered parameters are: distance between mandibular dental centerline and midsagittal facial axis, rotation of the mandibular body, magnitude of elongation, low- ering of the mandibular body. The mandible was geometrically evaluated pre and post-surgery with the Dolphin software. Findings: The frontal symmetry of four out of five patients improved. The interincisal point in the fifth patient further devi- ated from the midsagittal plane. A different advancement between right and left side meanly of 4,4mm was assessed. In all patients occurred a certain degree ofrotation and lowering ofthe mandibu- lar body after FEMOD. Conclusion: All patients improved their symmetry. Four of them improved in all the measured parameters, while one patient got worse only in the decentralization of the interincisal point relative to the midsagittal line. The Floating Bone phenomenon could break new grounds in the management ofPRS patients.