Asymmetric mandibular prognathism: outcome, stability and patient satisfaction after BSSO surgery. A retrospective study.

PURPOSE: To investigate surgical outcome, long-term stability, the time course of relapse, neurosensory disturbances, and patient satisfaction after BSSO for correction of mandibular asymmetry. Another objective was to examine whether osteotomies for transverse rotation of the distal segment represent an increased risk for nerve injury.

SUBJECTS AND METHODS: In a retrospective study lateral and postero-anterior cephalograms, information from patient files and questionnaires were analysed for 38 patients having more than 4 mm asymmetry at the chin pre-treatment (mean 8.4 mm). The radiographs were analysed preoperatively, postoperatively, after 6 months and 3 years.

RESULTS: Asymmetry of the chin to the facial midline improved on average by 56%. Skeletal relapse was about the same for transverse and antero-posterior surgical changes (10-15%). 58% of the patients had asymmetry of more than 3 mm at menton 3 years post-surgery. Discrepancy between upper and lower dental midlines improved on average 80%. Normal or near normal sensation to the lower lip/chin was reported by 44% of the patients which is similar to sensory disturbances after BSSO straight set-back performed by the same surgical team. A difference in the incidence of neurosensory disturbance between the two osteotomy sides was observed. Satisfaction with the treatment result was reported by all patients except for two.

CONCLUSION: Correction of mandibular asymmetry by BSSO is fairly stable. Although the risk for sensory impairment for the individual patient was similar to impairment in a sample having straight setback, rotation of the distal segment during surgery may represent an increased risk for sensory impairment on the deviating side (P = 0.06). Three years after surgery patients were generally satisfied with the result even if more than 3 mm of asymmetry at the chin remained for 58%. The findings have implications for treatment planning and the decision to elect one-jaw, bimaxillary surgery and/or additional genioplasty.