The Usefulness of Mandibular Anglectomy in Patients With Masticatory Muscle Tendon-Aponeurosis Hyperplasia: A Preliminary Single-Center Survey

Abstract

Objective Masticatory muscle tendon-aponeurosis hyperplasia (MMTAH) is a recently identified condition characterized by restricted mouth opening due to hyperplasia of the temporalis muscle tendon and masseter muscle aponeurosis. This study examines the treatment and clinical course of patients with MMTAH who underwent surgery at our hospital. Subjects and methods The study included 14 patients (four males and 10 females; mean age: 33.9 years; age range: 17-50 years) who were clinically diagnosed with MMTAH at our hospital between 2008 and 2020. The surgical procedure, as well as the preoperative, intraoperative, and postoperative mouth opening range of each patient, were examined. Results In all cases, the mouth opening range significantly improved postoperatively. Patients who underwent mandibular anglectomy showed a significantly greater mouth opening range both preoperatively and postoperatively compared to those who did not undergo the procedure. Additionally, mandibular anglectomy was effective in maintaining the mouth opening range at six months in patients who underwent the procedure, in contrast to those who did not. Conclusions Mandibular anglectomy appears to be effective in maintaining the mouth opening range in patients with MMTAH. While additional case studies are needed to confirm our findings, we believe that mandibular anglectomy is a valuable treatment option for MMTAH.

Keywords: anglectomy; masticatory muscle tendon-aponeurosis hyperplasia; mmtah; square mandible; trisumus.

Figure 1. Intraoperative findings (intraoral approach)

(A) A flying bird-like mucosal incision was made along the external oblique line of the mandibular branch, extending from the upper anterior margin of the mandibular branch to the first mandibular molar. (B) White aponeurosis on the lateral surface of the left masseter muscle, visible after dissection.

Figure 2. Coronoidectomy

(A, B) The muscle process was cut and extracted using a reciprocating bone saw or ultrasonic bone scalpel. (C) The surgery continued while the mouth opening range was monitored intraoperatively, with the range improving from 30 mm to 40 mm.

Figure 3. Mandibular anglectomy

(A) Preoperative 3D CT image. (B) Postoperative 3D CT image. (C, D) Resection of the mandibular angle. The mandibular angle was resected equally on both sides using an oscillating saw blade. Intraoperative mouth opening change: from 40 mm to 60 mm.

Figure 4. Patient-specific 3D-printed cutting guides

(A) Cutting guide derived from a 3D model (yellow dotted line), with the osteotomy line indicated by the red line. (B) Intraoperative findings, showing the application of the cutting guide during the procedure.

Figure 5. Photographs of faces

(A) Preoperative. (B) Postoperative (two weeks). (C) Postoperative mouth opening range, showing an improvement from 25 mm to 53 mm.

Figure 6. Maximum mouth opening

This figure shows the maximum mouth opening range measured preoperatively, intraoperatively, one month postoperatively, and six months postoperatively (mm), along with the average value of the maximum mouth opening range (mm). The asterisk (*) indicates statistical significance (p ≤ 0.05).