Clinical Study on Mandibular Fracture After Marginal Resection of the Mandible

Kohei Okuyama DDS, Section of Maxillofacial Surgery, Department of Maxillofacial and Neck Reconstruction, Graduate school of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo, Japan
Yasuyuki Michi DDS, PhD, Section of Maxillofacial Surgery, Department of Maxillofacial and Neck Reconstruction, Graduate school of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo, Japan
Masashi Yamashiro DDS, PhD, Section of Maxillofacial Surgery, Department of Maxillofacial and Neck Reconstruction, Graduate school of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo, Japan
Kiyoshi Harada DDS, PhD, Section of Maxillofacial Surgery, Department of Maxillofacial and Neck Reconstruction, Graduate school of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo, Japan
Marginal resection (MR) of the mandible results in better esthetic and functional outcomes after surgery than segmental resection. On the other hand, MR has risks of mandibular fracture (MF) after surgery due to the decrease of mandibular strength depending on the reduction of the mandibular body height (MBH).  It is reported that the MBH should be at least more than 10 mm to prevent the MF1. In this study, we examined the various factors of postoperative MF retrospectively including the postoperative MBH not by measuring its actual height but by calculating the preserving rates of postoperative MBH.

The subjects were 45 patients who underwent MR from 2003 to 2012 in our department. We assessed the age, sex, resection area, occlusion, number of tooth, use of denture, and irradiation in these patients. The postoperative occlusion was classified by Eichner’s method which indicates the stability of occlusion. In additon, we calculated the preserving rate of MBH and the rate of defect range by measuring bone height or length on the panoramic radiographs. Those measuring methods are as follows; The preserving rate = postoperative MBH / preoperative MBH, and the rate of defect range = the length of postoperative defect / the distance between bilateral condylar heads.

In 45 patients, 33 (70.2%) patients underwent MR by extraoral approach and neck dissection with or without soft tissue reconstruction. The surgical defects were closed by primary suture in 25 patients (55.6%). The others were skin grafting (17.8%), soft tissue reconstruction by forearm flap (13.3%), and simple tie-over (13.3%). The MF occurred in 4 patients (8.9%). We examined their oral conditions such as surgical technique, defect area, fracture point, postoperative period, dental formula including the number of tooth, the preserving rate of MBH, and the rate of defect range. On the Eichner’s classification, all 4 fractured patients were included in the B-group that had at least one molar occlusal support. In addition, they had more than 20 teeth, and most of their preserving rates of MBH were less than 0.3, while the rate of defect range had no correlation with MF. Since the MF was observed between 1.5 and 40 months after MR, it was impossible to foresee when the MF occurred. Statistically, there were no significant factors for MF in age, sex, resection area, use of denture, and irradiation.

These results suggest that the preserved bone should be reinforced with titanium plates or bone transplantation when the preserving rate of MBH is less than 0.3 and the number of tooth are more than 20. Though, the patient’s oral habits such as bruxism, thickness of mandibular cortical bone2, buccal to lingual width of mandibular bone, and bone density, etc. were not examined in this study, those suggested standards in this study may be useful to prevent MF after MR of the mandible.

  1. Murakami K, Sugiura T, Kirita T, et al: Biomechanical Analysis of the Strength of the Mandible After Marginal Resection. J Oral Maxillofac Surg 69:1798-1806, 2011
  2. Kingsmill VJ, Boyde A: Variation in the apparent density of human mandibular bone with age and dental status. J Anat 192:233, 1998
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