Many plastic surgeons use mandibular osteotomy (reduction gonioplasty) without masseter resection to correct a square face. However, there is not enough long-term observation of the masseter after reduction gonioplasty, although some researches have already confirmed that the volume of masseter muscle does decrease shortly after reduction gonioplasty.
Methods: The Plastic Surgery Hospital database was retrospectively reviewed for patients who underwent reduction gonioplasty. Fifty-six patients with both preoperative and 4 years postoperative 3-dimensional computed tomography (3DCT) were included. The changes in the volume and morphology of the masseter muscle after reduction gonioplasty were assessed quantitatively. The 3DCT data were analyzed using Mimics 10.01 software.
Results: All patients were satisfied with the outcome. No complications happened. There were significant differences between the preoperative and 4 years postoperative volume and morphology.
Conclusion: After reduction gonioplasty, the masseter muscle atrophied (reduced 20.98% ± 8.75%), especially the lower part of the masseter muscle in the long-term follow-up. Most patients with prominent mandibular angles should be treated with reduction gonioplasty without approaching the masseter muscle.