J Korean Assoc Oral Maxillofac Surg.  2013 Oct;39(5):217-223.

Effect of perioperative buccal fracture of the proximal segment on postoperative stability after sagittal split ramus osteotomy

• Lee SY
• Yang HJ
• Han JJ
• Hwang SJ

Abstract

OBJECTIVES
Buccal fracture of the mandibular proximal bone segment during bilateral sagittal split ramus osteotomy (SSRO) reduces the postoperative stability. The primary aim of this study is to evaluate the effect of this type of fracture on bone healing and postoperative stability after mandibular setback surgery.
MATERIALS AND METHODS
Ten patients who experienced buccal fracture during SSRO for mandibular setback movement were evaluated. We measured the amount of bone generation on a computed tomography scan, using an image analysis program, and compared the buccal fracture side to the opposite side in each patient. To investigate the effect on postoperative stability, we measured the postoperative relapse in lateral cephalograms, immediately following and six months after the surgery. The control group consisted of ten randomly-selected patients having a similar amount of set-back without buccal fracture.
RESULTS
Less bone generation was observed on the buccal fracture side compared with the opposite side (P<0.05). However, there was no significant difference in anterior-posterior postoperative relapse between the group with buccal fracture and the control group. The increased mandibular plane angle and anterior facial height after the surgery in the group with buccal fracture manifested as a postoperative clockwise rotation of the mandible.
CONCLUSION
Bone generation was delayed compared to the opposite side. However, postoperative stability in the anterior-posterior direction could be maintained with rigid fixation.

Keyword

Mandibular fracture; Sagitta split ramus osteotomy; Fracture healing; Postoperative stability

MeSH Terms

Fracture Healing
Humans
Mandibular Fractures
Osteotomy, Sagittal Split Ramus*
Recurrence

Figure

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  Fig. 1 Rigid fixation of a buccal fracture of the proximal segment. The buccal fracture on the right side was stabilized using long mini-plate and monocortical screws and additional bicortical positional screw (circle).

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  Fig. 2 Evaluation of bone regeneration using Image J. A. The buccal fracture was occurred on right proximal segment (circle). B. The total inter-segmental area between the proximal and distal segments was defined based on the axial computed tomography image. C. The total inter-segmental area was adjusted to the threshold below 210 in the Image J program, where the threshold of cortical and medullar bone was greater than 210. D, E. The area of newly formed bone (threshold from 190 to 210 in the Image J program) was extracted from the total inter-segmental area. Soft tissue and dead space (threshold below 190) were also removed. Finally, the ratio of new bone area to total inter-segmental area was calculated.

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  Fig. 3 Post-operative stability was evaluated by measuring the changes in reference points and reference planes: sella (S), nasion (N), x-axis (SN7, a line drawn 7° lower to the S-N line), y-axis (SN7V, a line on the N and perpendicular to SN7), point B (B), menton (Me), gonion (Go).

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  Fig. 4 Comparison of new bone formation between the buccal fracture side and non-fractured side. Bone healing was significantly delayed on the fractured side compared with the opposite side. *P=0.019.

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  Fig. 5 Surgical movement in the experimental group and control group. There were no significant differences between the two groups (P<0.05). (SN-MeGo: mandibular plane angle, S-Go: posterior facial height, N-Me: anterior facial height, SNB: SN to NB, OB: overbite, OJ: overjet, SN7-B vertical: vertical change of B point by surgery, SN7V-B horizontal: horizontal change of B point by surgery)

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  Fig. 6 Post-operative changes of parameters in the experimental group and control group six months after surgery (T2-T1). There were no significant differences between the two groups, except in mandibular plane angle (SN-MeGo) and anterior facial height (N-Me). P<0.05, *P=0.015, **P=0.029. (S-Go: posterior facial height, SNB: SN to NB, OB: overbite, OJ: overjet, SN7-B vertical: vertical change of B point by surgery, SN7V-B horizontal: horizontal change of B point by surgery)

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