Cephalometric Long-Term Surgical Outcomes in Treacher Collins Patients

In Treacher Collins syndrome bimaxillary surgery can serve to restore the facial balance and also level the occlusal plane. Do to the shortened posterior facial height in Treacher Collins patients the orthagnathic setup generally involves anterior impaction of the maxilla with posterior maxillary extrusion resulting in correction of the palatal plane angle and the opening of the posterior nasopharyngeal airway. This leveling of the maxilla results in an even greater rotation of the already obtuse mandibular plane during the saggital split. The purpose of this study was to examine the long-term stability of bimaxillary orthagnathic surgery in a Treacher Collins population..

Patients and Methods:

A total of 22 patients where found to meet the inclusion criteria. Of the 22 patients 11 were felt to have occlusal relationships that required orthagnathic surgery for correction. Of the 11 potential surgical cases 9 patients underwent bimaxillary surgery. Part I of the study analyzed if there were cephalometric differences between the surgical and nonsurgical Treacher Collins cases. Part II of the study analyzed the 9 surgical cases using the same cephalometric parameters. For each parameter there was a pretreatment measurement(T1), presurgical measurement(T2), immediate post-op(T3) and at least one year post-op(T4). The relapse was calculated as the change fromT3 to T4(T3-T4) and total gain was calculated as the surgical movement minus relapse. The Student t test for paired parametric data was applied to obtain values for statistical differences across time for the data sets.

Results:

Part I: Part I of the study found that non-operated patients demonstrated a more normal projected maxilla and less open mandibular angle supporting the clinical findings of a normal occlusal relationship without an anterior open bite.

Part II: Part II of the study demonstrated that there was a significant relapse of the midface length and palatal plane angle. The anterior impaction of the maxilla and posterior extrusion relapsed to a significant degree. The relapse in the rotation of the mandibular plane angle it was not significant. Palatal plane relapse was 100%.

Discussion

Clinically the un-operated patients demonstrate a normal occlusal relationship not typical of the operated patients who all had anterior open-bite malocclusion. There was significant relapse in the SNA and Witts appraisal which is in keeping with a loss in maxillary advancement position. This relapse however did not effect the final occlusal result which was probably compensated with post-operative orthodontic treatment. The second area of significant relapse was in the midface length and palatal plane angle.

In summary bimaxillary surgery in Treacher-collins patients exhibits good skeletal and dental stability. LeFort I osteotomy to correct maxillary clockwise rotation tends to relapse however mandibular counterclockwise rotation and bilateral saggital split osteomies remain stable over time.