Evaluation of Mandibular Anatomy Associated With Bad Splits in Sagittal Split Ramus Osteotomy of Mandible

Fracture patterns in cleft orthognathic surgery. a cross-sectional study

Objective

This study aims to identify fracture patterns on the lingual aspect of the mandible following Bilateral Sagittal Osteotomy of the Mandibular Ramus and correlate these patterns with mandibular anatomical characteristics in patients with cleft lip and palate.

Methods

Two hundred cone beam CT scans were analyzed, with 100 scans in the preoperative period to assess mandibular anatomy and 100 in the postoperative period to evaluate the course of fractures on the lingual surface after surgery.

Results

Statistical analysis revealed no correlation between the depth of the mandibular fossa and the type of fracture after bilateral sagittal osteotomy. Similarly, there was no association between the height and angle of the mandibular body and the type of fracture. The most common fracture type observed was the type 3 pattern, characterized by a line running through the mandibular canal. Furthermore, no relationship was identified between the studied anatomical aspects and the occurrence of undesired fractures.

Conclusions

The anatomical data presented in this study can assist surgeons in selecting the safest surgical techniques and optimal osteotomy sites, particularly in patients with cleft lip and palate.

Computed tomography evaluation of risk factors for an undesirable buccal split during sagittal split ramus osteotomy

Sagittal split ramus osteotomy (SSRO) sometimes induces an irregular split pattern referred to as a bad split. We investigated the risk factors for bad splits in the buccal plate of the ramus during SSRO. Ramus morphology and bad splits in the buccal plate of the ramus were assessed using preoperative and postoperative computed tomography images. Of the 53 rami analyzed, 45 had a successful split, and 8 had a bad split in the buccal plate. Horizontal images at the height of the mandibular foramen showed that there were significant differences in the ratio of the forward thickness to the backward thickness of the ramus between patients with a successful split and those with a bad split. In addition, the distal region of the cortical bone tended to be thicker and the curve of the lateral region of the cortical bone tended to be smaller in the bad split group than in the good split group. These results indicated that a ramus shape in which the width becomes thinner towards the back frequently induces bad splits in the buccal plate of the ramus during SSRO, and more attention should be paid to patients who have rami of these shapes in future surgeries.

Correlation between mandibular anatomy and bad split occurrence during bilateral sagittal split osteotomy: a three-dimensional study

OBJECTIVES

This study aimed to find out the correlation between different anatomical parameters of the mandible and the occurrence of a bad split in patients who had undergone bilateral split sagittal ramus osteotomy (BSSRO).

MATERIALS AND METHOD

At both the distal roots of the first molar (1) and the retromolar area (2), we measured the distance from the buccal margin of the inferior dental canal (IDC) to the buccal margin of the cortical bone (MCBC), the thickness of both buccal cortical (WBCB) and cancellous bone (WBCA), distance from the superior border of IDC to the alveolar crest (MCAC), buccolingual thickness (BLT), and thickness of cancellous bone (WCA). At the ramus, the distances between the sigmoid notch to the upper part of the lingula (SL) and the inferior border of the mandible (SIBM), the thickness of the ramus at the level of the lingula (BLTR), and the anteroposterior width of the ramus (APWR) were measured. The paired and independent t-tests were used when applicable, and a P-value < 0.05 was considered significant.

RESULTS

MCBC1 showed a significant difference between bad and non-bad split sides (P = 0.037). Both WBCA1 and WBCA2 show the same significant difference (P = 0.023, 0.024). Similarly, WCA1 and WCA2 showed a statistical difference between the bad and non-bad split sides (P = 0.027, 0.036). There were no statistically significant differences between the compared sides of WBCB1, WBCB2, MCAC1, MCAC2, SIBM, APWR, SL, and BLTR.

CONCLUSION

Narrow space between IDC and the buccal cortical margin, along with the decrease in the thickness of both buccal cancellous bone and total cancellous bone at the inferior border of the mandible along the course of SSRO, has been implicated in the occurrence of bad split intraoperatively.

Comparison of two surgical techniques (HOO vs. BSSO) for mandibular osteotomies in orthognathic surgery-a 10-year retrospective study

PURPOSE

To retrospectively compare the high-angled sagittal split osteotomy (HOO) and the bilateral sagittal split osteotomy (BSSO) for the correction of skeletal dysgnathias regarding intra- and postoperative complications.

METHODS

The electronic medical records of all patients treated with an orthognathic surgery at the Department for Oral, Maxillofacial and Facial Plastic Surgery, University Hospital Frankfurt, Germany, between the years 2009 and 2019 were retrospectively reviewed.

RESULTS

Two hundred ninety-one patients were included. The overall complication rates were 19.78% (BSSO) compared to 12.5% (HOO) (p = 0.14). Significant differences were found regarding the operation time (HOO < BSSO, p = 0.02), material failure (HOO > BSSO, p = 0.04), and early recurrence requiring revision surgery (HOO < BSSO, p = 0.002). The use of a ramus plate significantly reduced the risk of plate failure (2.8% < 13.6%, p = 0.05). More bad splits (p = 0.08) and early sensory disorders (p = 0.07) occurred in the BSSO group.

CONCLUSION

The HOO presents a possible alternative to the BSSO since newly developed osteosynthesis material significantly reduces the risk of material failure. The BSSO is accompanied by higher risks of developing complications like a bad split and sensory disorders but, however, remains the standard for large anterior-posterior transpositions of the mandible.

Dal Pont vs Hunsuck: Which Technique Can Lead to a Lower Incidence of Bad Split during Bilateral Sagittal Split Osteotomy? A Triple-blind Randomized Clinical Trial

BACKGROUND

We aimed to assess the incidence of bad split fractures during Bilateral Sagittal Split Osteotomy (BSSO) mandibular setback surgery using Dal Pont and Hunsuck techniques.

METHODS

All healthy adults with skeletal class III discrepancy, who were candidates for mandibular setback surgery were enrolled in this randomized clinical trial in the Maxillofacial Surgery Department of Qaem Hospital, Mashhad, Iran; from 2018-2020. These patients were randomly divided into two equal groups; one group underwent BSSO using Dal Pont osteotomy while the Hunsuck osteotomy was employed for the other group. A bad split fracture which identified through intra-operative clinical and postoperative radiographic examination was the outcome variable. The significance level was set at 0.05 using SPSS 16.

RESULTS

Overall, 104 consecutive patients, comprising of 52 (50%) males with an average age of 23.09±3.08 were recruited. The average duration of osteotomy and splitting was reported to be 22.74±3.06 min. 10 bad split fractures (9.62%) were observed; 7 of which occurred in the Dal Pont group and 3 in the Hunsuck group. However, this difference was not significant. In 80% of the cases, bad split osteotomy occurred in the proximal segment, while this finding was identified in the distal segment in 20% of cases. The average duration of osteotomy and splitting was significantly longer in the Dal Pont group (P<0.001).

CONCLUSION

The duration of osteotomy and splitting is much shorter when the Hunsuck technique is employed, and the incidence of unfavorable fractures is also less compared to the Dal Pont osteotomy technique.

Does the Presence of Impacted Mandibular Third Molars Increase the Risk of Bad Split Incidence During Bilateral Sagittal Split Osteotomy?

BACKGROUND

The possibility of mandibular bad spilt might happen during bilateral sagittal split osteotomy (BSSO). This study investigated the effect of impacted mandibular third molars on bad spilt incidence during BSSO.

METHODS

Totally, 140 patients under 40 years old who were candidates for BSSO surgery due to class 3 skeletal discrepancy were divided randomly into two equal groups. The impacted mandibular third molars were presented in one group during BSSO (Exposed), and the third molars were removed at least six months before surgery for the other group (Unexposed). All cases underwent BSSO using the same technique by a single surgeon. A bad split was diagnosed by inter-operative clinical examination and postoperative panoramic radiography.

RESULTS

Four bad split occurrences were observed including three patients in the group which impacted mandibular third molars were presented and one patient in the group without impacted mandibular third molars. The incidence of bad fracture in the exposed group was 3.7 times more than the unexposed group. The incidence of the bad fracture in exposed group was 3.7 times more than unexposed group. The chance of fractures in females was 1.7 times higher than males. With one year addition to the patient's age, chance of fracture increased 0.985 times more.

CONCLUSION

Overall incidence of bad split fracture in presence of mandibular third molars in females and at older ages increased during BSSO. The extraction of impacted mandibular third molars, six months before the BSSO is recommended to prevent the bad split incidence during the operation.

What are the Effects of Age and Presence of Third Molars on the Occurrence of Unfavorable Splits During Sagittal Split Osteotomy?

PURPOSE

Several studies have investigated risk factors of unfavorable splits associated with sagittal split osteotomies but yielded conflicting information. The purpose of this study is to estimate the frequency of and identify factors associated with unfavorable splits during sagittal split osteotomies (SSOs).

MATERIAL AND METHODS

A retrospective cohort study was conducted on patients who underwent orthognathic surgery, including SSOs at our institution from January 2010 to October 2016. The independent variables were mandibular third molar (M3) status, age, gender, and preoperative dentofacial diagnosis. The outcome variable was the effectiveness of the sagittal split resulting in either favorable or an unfavorable split. Data analyses were performed using logistic regression models except in the case of small sample sizes of preoperative dentofacial diagnoses for which the Fisher's exact test was used.

RESULTS

A total of 888 patients with an average age of 24.97 ± 5.09 years underwent 1,776 SSOs. Sixteen (0.90%) unilateral unfavorable splits occurred. Unfavorable splits were less common in patients with an M3 present than in patients with the M3 absent. Having an M3 present reduced the chance of an unfavorable split by 69%, adjusted for age and gender; OR (95% CI) = 0.308 (0.103, 0.919); P = .035. The odds of having an unfavorable split were increased by 8.8% for every year of age increase; adjusted OR (95% CI) = 1.088 (1.004, 1.178); P = .038. Based on this estimation, a 45-year-old is 2.3 times more likely to have an unfavorable split compared to a 35-year-old (95% CI:1.041, 5.146), and is 5.4 times more likely to have an unfavorable split compared to a 25-year-old (95% CI:1.083, 26.48).

CONCLUSIONS

The presence of a mandibular third molar (M3) was associated with a decreased risk of an unfavorable split, independent of age and gender. There was a significant association between increased age and the incidence of an unfavorable split.

Distribution of bone thickness in the human mandibular ramus - a CBCT-based study

Background

The bone thickness of the human mandibular ramus is an important parameter in mandibular surgeries. The aim of this study was to systematically measure the bicortical bone thickness, the ramus dimensions and the position of the lingula. The measurements were tested on significant correlations to the patients’ parameters.

Methods

Based on CBCT scans 150 rami were reconstructed as 3D polygon surfaces. An anatomical grid was adapted to the ramus surface to mark the bone thickness measurement points and to achieve comparability between the measurements on different mandibles. The bone thickness, ramus height, ramus width and the gonion angle were measured. A cluster analysis was performed with these parameters to identify clinically relevant groups with anatomical similarities.

Results

The median distribution of the bone thickness was calculated and visualized in a pseudo-colour map. The mean ramus height was 44.78 mm, the mean width was 31.31 mm and the mean gonion angle was 124.8°. The average distance from the lingula to the dorsal tangent was 53% of the total width and its distance to the caudal tangent was 65% of the total height. Significant correlations between the bone thickness and the ramus proportions could be identified. Age and sex had no significant influence on the mean bone thickness. The measured rami could be divided into two groups by cluster analysis.

Conclusion

The dimensions of the human mandibular ramus can be determined from 3D reconstructed surface models from CBCT scans. Measurements could be made comparable by applying an anatomically oriented grid. A cluster analysis allowed the differentiation of two groups with different bone thickness distributions and geometries, which can be used for the optimization of osteosynthesis systems and their precision of adaptation to different ramus morphologies.

Density of the mandibular ramus (cancellous:cortical bone volume ratio) as a predictor of the lingual fracture pattern in bilateral sagittal split osteotomy

The aim of this retrospective cohort study was to evaluate the relative amount of cancellous bone in the mandibular ramus as a predictor of lingual fracture patterns after bilateral sagittal split osteotomy (BSSO). The study including 78 consecutive patients (156 osteotomy sites). In preoperative cone-beam computed tomographic (CT) scans, the volumes of cancellous and cortical bone in the BSSO surgical field were estimated. Patients were divided into two groups based on the cancellous:cortical bone ratio. We studied postoperative cone-beam CT scans for lingual fracture lines and subcategorised them according to the lingual split scale (LSS). Generalised linear mixed models (GLMM) were estimated to evaluate the association between the cancellous:cortical bone ratio and the lingual fracture pattern. There was a significant association between the cancellous:cortical bone ratio of the mandibular angle and the lingual fracture pattern after BSSO. Mandibular angles with a relatively small amount of cancellous bone showed significantly more LSS3 fracture lines (OR=1.990, 95%CI 1.043 to 3.796, p=0.043). These mandibular angles also showed more unfavourable fractures (LSS4), although this was not significant (OR=2.352, 95%CI 0.748 to 7.392, p=0.143). The relative amount of cancellous bone in the mandibular angle is significantly associated with the lingual fracture line after BSSO.

Spontaneous Union of an Accidentally Fractured Proximal Segment During Vertical Ramus Osteotomy

After sawing in the intraoral vertical ramus osteotomy, in the case of an incomplete amputation, the proximal segment is split using the osteotome. Unfortunately, in this case, the proximal segment was accidentally fractured. The operation was completed without performing any other fixation. Postoperatively intermaxillary fixation was performed and kept for a week, followed by physical therapy, which was initiated immediately after. The patient was closely observed for 6 months. No abnormal findings were detected clinically, and the union of bone was verified.