Evaluation of overlapped cortical bone area after modified plate fixation with bent plate in sagittal split ramus osteotomy

https://doi.org/10.1016/j.jcms.2013.08.009Get rights and content

Abstract

Purpose

The purpose of this study was to evaluate bony change in an overlapped cortical bone area at the anterior site of the proximal segment after modified plate fixation with a bent plate in sagittal split ramus osteotomy (SSRO).

Subjects and methods

The subjects were 66 patients (132 sides) who underwent bilateral SSRO setback surgery. After the surgery in SSRO, an overlapped area of cortical bone at the anterior site of the proximal segment was not removed to keep the contact area between the proximal and distal segments intact, and was fixed with a bent plate and 4 screws in each side of the mandible. At the posterior site, a 3–7 mm gap was maintained between the proximal and distal segments to prevent inward-rotation of the condylar long axis. Ramus width, lateral cortex width and lateral cortex step angle were assessed in a coronal image immediately after the surgery, and 1-year postoperative by computed tomography (CT).

Results

Ramus width after 1-year was significantly larger than that before surgery and smaller than that immediately after surgery in both sides (P < 0.0001). Lateral cortex width after 1-year was significantly larger than the preoperative value and smaller than that immediately after surgery in both sides (P < 0.0001). Lateral cortex angle after 1-year was significantly larger than the preoperative value in both sides (P < 0.0001).

Conclusion

The above findings suggested that the overlapped cortical bone decreased thickness and the cortical bone step disappeared following favourable bone remodelling after 1-year, even though the cortical bone was not removed at the anterior site of the proximal segment.

Introduction

Sagittal split ramus osteotomy (SSRO) is used most frequently to correct jaw deformities (Trauner and Obwegeser, 1957). One of the advantages of this method is that formation of a large area of bony contact is possible after either advancement or retrusion of the distal segment. However, a wide bony contact without the step of a cortical bone surface between the proximal and distal segments can induce inward-rotation of the condylar long axis in setback surgery (Ueki et al., 2001, Ueki et al., 2007).

We previously used bent plates to secure fragments without positioning the device and found that the bent plates increased the incidence of postoperative TMD and did not change skeletal or occlusal stability (Ueki et al., 2001, Ueki et al., 2007). In this method, the gap between the proximal and distal segments is created by a bent plate, preventing formation of a large bony contact. In setback surgery, especially with asymmetry, fixation between segments can be performed without a bony contact to prevent large changes in condylar position and angle.

The previous study showed that the gap between the proximal and distal segments could fill with new bone after SSRO with titanium or absorbable plates, even if there were few bony contacts between the segments (Ueki et al., 2009). Furthermore, bone volume and facial contour can be adjusted without bone grafts, preventing postoperative TMD (Ueki et al., 2009).

Although the absorbable plate has recently become used more often in orthognathic surgery, there is the possibility of breakage of the absorbable plate (Yoshioka et al., 2013). Therefore, we devised a method where the two cortical bones of the distal and proximal segments are left overlapping at the anterior site of the proximal segment. This method makes it possible to keep the contact area and rigid fixation at the anterior site of the proximal segment and to create the gap at the posterior site of the proximal segment as reported previously. However, there was the question of how the overlapped area of the two cortical bones changed over time.

The purpose of this study was to evaluate bony change in the overlapped cortical area at the anterior site of the proximal segment after modified fixation with a bent absorbable plate in SSRO.

Section snippets

Patients

The 66 Japanese adults (men: 22, women: 44) in this study presented with jaw deformities diagnosed as mandibular prognathism with and without maxillary deformity. At the time of orthognathic surgery, the patients ranged in age from 16 to 51 years, with a mean age of 29.2 years (standard deviation, 10.8 years). Although this study was a retrospective study, informed consent was obtained from the patients in accordance with the declaration of Helsinki and the study was approved by Kanazawa

Results

No patient had post-surgical wound infection or dehiscence, bone instability or non-union, or long-term malocclusion. The mean setback amount was 7.5 ± 2.9 mm on the right side and 7.1 ± 3.3 mm on the left side.

Preoperative TMJ symptoms most frequently reported were abnormal sound (clicking and crepitus) and slight pain when opening the mouth; none of the patients reported trismus. Symptoms were improved by surgery in 81.8% (18/22 joints) on the right side and 77.3% (17/22 joints) on the left

Discussion

Use of resorbable materials to stabilize the maxillofacial skeleton has been reported recently (Bessho et al., 1997, Bos et al., 1987, Edwards et al., 2001). There is no need for a second operation to remove the implant. There is less risk of weakening of the fixed bone due to stress shielding and there is no risk of metallic corrosion. However, several problems remain, including mechanical weakness (Böstman, 1991, Takizawa et al., 1998), late foreign body reactions, osteolytic change, and

Conclusion

This study suggested that overlapped cortical bone decreases in thickness and the cortical bone step disappears by bone remodelling after 1-year, even if the cortical bone is not removed at the anterior site of the proximal segment. In short, it is not always necessary to fit the lateral surface of the distal and proximal segments and remove the step of the cortical bone at the osteotomy line in SSRO.

Ethical approval

Not required.

Competing interests

None declared.

References (32)

Cited by (18)

  • Mandibular bone healing after advancement or setback surgery using sagittal split ramus osteotomy

    2018, Journal of Cranio-Maxillofacial Surgery
    Citation Excerpt :

    When segments were fixed in SSRO setback surgery, usually overlapping cortical bone of the anterior proximal segment is removed. However, it was found that the overlapping cortical bone actually decreases in thickness and the cortical bone step disappears by bone remodeling after 1 year, even if the overlapping area was not removed (Ueki et al., 2014). Bony contact can be obtained at the anterior site of the proximal segment although the gap between segments is made at the posterior site to prevent post-operative change of the condylar position and angle, in setback surgery.

  • Modified hybrid fixation using absorbable plate and screw for mandibular advancement surgery

    2017, Journal of Cranio-Maxillofacial Surgery
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    Landes et al. (2014) reported that an absorbable plate group showed less relapse yet with small operative movement in 13 mandibular advancement surgery cases. Our previous studies showed that the unsintered hydroxyapatite/poly-l-lactic acid (uHA/PLLA) plate system is also very useful for fixation in SSRO and Le Fort I osteotomy in class III cases (Ueki et al., 2011a,b, 2013, 2014a,b, 2012a,b, 2017). Furthermore, we introduced hybrid fixation (one four-halls-plate and four mono-cortical screws and one bi-cortical screw) and bi-cortical absorbable plate fixation (one four-halls-plate, two mono-cortical screws and two bi-cortical screws) in mandibular setback surgery in SSRO for class III cases.

  • Comparison of skeletal stability after sagittal split ramus osteotomy among mono-cortical plate fixation, bi-cortical plate fixation, and hybrid fixation using absorbable plates and screws

    2017, Journal of Cranio-Maxillofacial Surgery
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    The Obwegeser method was used for all patients. Fixation in SSRO was performed according to previous reports (Ueki et al., 2001, 2008, 2014a,b, 2015). Group division was as outlined below.

  • Change in mandibular body height at the site of a fixation plate in the advance (lengthening) and setback (shortening) sides after sagittal split ramus osteotomy

    2016, Journal of Cranio-Maxillofacial Surgery
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    Although there are limitations to this method in setback surgery, bicortical fixation consisting of two lateral cortical bones of the distal and proximal segments can also be obtained without use of large and long bicortical screws, provided the area of overlap is wide enough and thickness of the lateral cortex is adequate to implant the absorbable screw. Results of a previous study suggested that the overlapped cortical bone decreases thickness and the cortical bone step disappears by favorable bone remodeling after 1 year, even if the cortical bone is not removed at the anterior site of the proximal segment (Ueki et al., 2014). In another study using horizontal CT image, postoperative decrease in ramus length at the 1 cm level under the mandibular foramen suggested that the absorption might occur by set back surgery.

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