The Study Of Biological Mechanics Mechanism Of Trans-Sutural Distraction Osteogenesis For Midfacial Hypoplasia In Growing Cleft Lip And Palate Patients

Objective:1.To investigate the biological mechanics mechanism of trans-sutural distraction osteogenesis(STDO)for midfacial hypoplasia in craniofacial complex with cleft lip and palate through clinical study and finite element analysis(FEA).2.To compare the effects of TSDO made from the two devices for treatment of midfacial hypoplasia and investigate the biomechanical changes of craniofacial skeleton during protraction in growing patients with cleft lip and palate to improve the understanding of the mechanism of the TSDO to optimize its application via FEM.Methods:1.3D morphological and quantitative measurement analyses were performed to evaluate the changes of midfacial sutures and by superimposition of preoperative and postoperative computed tomographic(CT)images.Meanwhile,FEA models simulating STDO with rigid external distractor were constructed and stress distribution over sutures were analyzed.2.FEA models simulating STDO with facemask were constructed and stress distribution were analyzed.Results:(1)The patient achieved satisfactory appearance.The 3D quantitative measurement showed differential advancement of each landmark of midfacial sutures.In the sagittal plane,maximum forward displacements were observed at the pteryomaxillary suture.In the vertical plane,nasomaxillary suture and frontomaxillary suture on both sides showed the maximum upward displacements,and the maximum downward displacement at pteryomaxillary suture.In the transverse plane,each landmark of midfacial sutures had a smaller displacement.The maximum Von Mises stress was at zygomaticomaxillary suture on the normal side.The stress level on the cleft side was higher than that on the normal side,and the maximum Von Mises stresses were at sphenomaxillary suture and zygomaticomaxillary suture.(2)On the normal side,the maximum Von Mises stress was at zygomaticotemporal suture,followed by frontomaxillary suture and sphenomaxillary suture.And the maximum first principal stresses were at frontomaxillary suture.On the cleft side,the maximum Von Mises stress was at sphenomaxillary suture,followed by zygomaticomaxillary suture and pteryomaxillary suture.And the maximum first principal stress was at sphenomaxillary suture.Also,the stress distribution in mandible,condyle,articular disk and articular fossa were high.Conclusion:(1)The different growth potential of midfacial sutures are results of the unequal advancement in different regions.(2)The first principal stresses on sutures were similar between the two devices,but the reaction force on forehead and chincup may cause related complications.