Pilot study of modification of the bilateral sagittal split osteotomy (BSSO) in pig mandibles

Does the modified inferior border osteotomy improve the surgical outcomes in bilateral sagittal split osteotomy?

BACKGROUND

To investigate the effect of lower border osteotomy on the lingual split pattern and IAN in BSSO procedures.

MATERIALS AND METHODS

The study comprised 32 patients (64 operated sides) who underwent bilateral sagittal split osteotomy (BSSO) due to dentofacial abnormalities between the periods of April 2021 and April 2022. In the mandible, 32 sides (the conventional group) received standard BSSO surgery, while 32 sides (the modified group) additionally received lower border osteotomy. Data regarding the split difficulty of the mandibular in BSSO surgery and the recovery status of the inferior alveolar nerve (IAN) one year after surgery were obtained and evaluated from patient records. The fracture line was radiographically evaluated for the lingual split pattern following surgery.

RESULTS

A statistically significant difference was observed in favor of the modified group when the mandibular split difficulty of the groups was compared (p = 0.032). The split time of the modified group was found to be statistically shorter than the conventional group (p ≤ 0.001). The mean numbness level of the modified group one year after surgery was statistically significantly lower than that of the conventional group (p = 0.019). Although there was no statistically significant difference between the two groups in terms of lingual fracture pattern, the rate of type 1 (87.5 %) fracture was higher in the modified group compared to the other group (68.8 %) (p = 0.089).

CONCLUSION

The lower border osteotomy performed in addition to the conventional BSSO surgery allows the split procedure easier and in a shorter time. The modification resulted in an increased incidence of type 1 lingual fracture pattern in the mandible. The neurosensory recovery capacity of the IAN in the postoperative period is higher in areas where lower-border osteotomies are performed.

Does osteotomizing the lower border of the mandible affect the lingual split pattern in a sagittal split ramus osteotomy?

AIM

The purpose of this study was to evaluate the effect of adding a fourth osteotomy at the lower border of the mandible on the lingual cortical fracture pattern in bilateral sagittal split ramus osteotomies.

PATIENTS AND METHODS

The sample of the study consisted of 20 patients (12 male and 8 female, with a mean age of 26.79 ± 7.12 years) with mandibular deformities who needed bilateral sagittal split ramus osteotomy. One side underwent a traditional sagittal split ramus osteotomy, and the procedure was modified on the other side by adding a 1 cm horizontal osteotomy at the lower border of the mandible, just distal to the caudal end of the vertical buccal osteotomy cut. A 3D CBCT was used to identify the split pattern.

RESULTS

In the total sample, 40% of the lingual splits ran vertically toward the lower border of the mandible (LSS1), 20% of the splits passed horizontally to the posterior border of the mandible (LSS2), 32.5% of the splits took place along the inferior alveolar canal (LSS3), and 7.5% of the splits were unfavourable fractures (LSS4). On the inferior border osteotomy sides, the distribution of LSS1, LSS2, LSS3, and LSS4 was 10 (25%), 6 (15%), 4 (10%), and 0 (00), respectively. Their distribution on the sides without inferior border osteotomy was 6 (15%), 8 (20%), 13 (32.5%), and 3 (7.5%), respectively. Statistical analysis revealed a significant difference between the two groups (p < 0.05).

CONCLUSION

Inferior border osteotomy tends to direct the lingual split fracture line toward the lower and posterior borders of the mandible and minimizes bad splits; however, further studies are needed to confirm our findings.

A Modified of Bilateral Sagittal Split Osteotomy: Technical Note and Proposal of a Nomenclature on the Osteotomy Lines

Bilateral sagittal split osteotomy for orthognathic surgery is the most used technique for mandible advancement or setback and has been well documented and modified over the years since Trauner and Obwegeser described it. The improvement brought by each technique allowed the surgeons to perform safer osteotomies, shorten the operative time, and increased the flexibility of the programmed mandibular movements. The authors present a modification of the bilateral sagittal osteotomy technique with the aim of making the technique easier to perform and more comfortable for the surgeon for the purpose of positioning the osteosynthesis plates and screws. Finally, the authors describe a nomenclature on the osteotomy lines of the bilateral sagittal split osteotomy.

Are There Differences in Fracture Patterns in Mandibular Ramus Sagittal Osteotomies Between Hunsuck/Epker, Wolford, and Posnick Modifications?

PURPOSE

Despite decades of study, the best technique for mandibular ramus sagittal osteotomy has not been definitively determined. The purpose of the present study was to compare fracture patterns, inferior alveolar nerve (IAN) visualization, and torque required for mandibular sagittal splitting using the Hunsuck/Epker, Wolford, and Posnick techniques.

METHODS

This was a laboratory (ex vivo), randomized, a single-blind study performed to evaluate sagittal split osteotomies in porcine mandibles using a specifically designed test system. The study's predictor variable was the osteotomy technique, which was divided into 3 groups: Group Hunsuck/Epker (GHE), group Wolford (GW), and group Posnick (GP). The outcome variables were lingual fracture pattern, torque in newtons (N) required to separate the mandible, and IAN visualization. The covariates were mandibular radiodensity and time between dejection and the experiment. The Kolmogorov-Smirnov normality statistics and analysis of variance with Tukey post test statistics were performed. P value <.05 was considered statistically significant.

RESULTS

The sample was composed of 120 equally divided porcine hemimandibles in each group. The torque forces were significantly lower (P < .001) when using the Posnick technique (2.07 ± 0.22 N) than when using the Hunsuck/Epker technique (4.45 ± 0.32 N) and Wolford (3.00 ± 0.21 N). GW (93.3%) and GHE (56.7%) showed a higher prevalence of lingual fracture in the posterior region of the mandibular canal (P < .001), while the GP (90%) had a higher frequency of lingual fracture pattern on the mylohyoid sulcus (P < .001). In more than 90% (P < .001) of the mandibles in GW and GHE, the IAN visualization was higher than 50%. In the GP, 90% (P < .001) of patients had IAN visualization of less than 50%.

CONCLUSIONS

The Posnick technique required less torque to perform the sagittal osteotomy in a pig mandible and had good predictability (90%) for the less preferred lingual fracture pattern and minimal visualization of the nerve. The Wolford technique provided the best predictability (93%) for the preferred lingual fracture pattern and the best nerve visualization. Caution must be exercised when extrapolating the results from animal models to human applications.

A Novel Modification of the Sagittal Split Osteotomy as an Access Osteotomy

Pathologies present in the central zone of the mandible are difficult to access, primarily because of the presence of the inferior alveolar nerve (IAN) and the need to remove a large corticocancellous component to reach the area of interest. Many times, this bony window is replaced as a free graft and there is complete resorption in the long term or even rejection of the graft causing a bony defect which can weaken the mandible. Furthermore, the damage to the IAN is profound. To try and avoid these comorbidities the traditional sagittal split osteotomy was modified to access a central osteoma impinging on the IAN and the successful removal of the same without any comorbidities such as paraesthesia or loss of bone structure. We believe that this modification can be used for other scenarios such as benign cysts and difficult presentations of impacted teeth.

Evaluation of the lingual fracture patterns after bilateral sagittal split osteotomy according to Hunsuck/Epker modified by an additional inferior border osteotomy using a burr or ultrasonic device

This study was conducted to compare fracture patterns and operation times after sagittal split osteotomy (SSO) by Hunsuck/Epker approach, performed using a burr or ultrasonic device, with and without osteotomy modification. A total of 80 SSOs were performed in fresh human cadavers using a burr or ultrasonic device to investigate the influence of surgical instruments as well as an additional bone cut on the inferior border of the mandible in terms of lingual fracture patterns. The times required for osteotomy and sagittal split were measured, and postoperative cone beam computed tomography images of all splits were analyzed. Without an additional inferior osteotomy, preferred splits according to Hunsuck/Epker were achieved in 35% of cases (7/20) with the burr and 45% (9/20) with the ultrasonic instrument. The inferior modification resulted in a greater number of unwanted fracture patterns in both groups. There was no relationship between the split technique and the fracture pattern (P=0.7854). Statistically significant differences in osteotomy time were observed between burr osteotomy and modified burr osteotomy (P=0.006), as well as modified ultrasonic osteotomy (P<0.001), but not between burr and ultrasonic surgery both without the inferior cut (P=0.36). The bone cut on the inferior border did not improve split control, but rather increased the risk of unwanted fractures and extended the operation time.

Postoperative Positional and Dimensional Changes of Mandibular Canal after Bilateral Sagittal Split Set-Back Osteotomy

Objective

This preliminary study was planned to provide information about preoperative mandibular canal (MC) position and the postoperative positional changes of MC and length in three dimensions, with the purpose of providing some assistance in reducing inferior alveolar neurosensory disturbance (IAND).

Methods

MC was examined on CBCT data using SimPlant Pro Standalone 13.0. MC locations were measured in all dimensions, with respect to mandibular bony borders.

Results

The results showed that MC is frequently located in the midthird of the ramus anteroposteriorly and superoinferiorly and in the midthird of the corpus superoinferiorly. Postoperatively, ramus width was increased, ramus length was decreased significantly, and MC was repositioned laterally and inferiorly. MC length was decreased on both sides, non-correlated with the set-back amounts.

Conclusion

Preoperative results may be beneficial for the prediction of MC position for surgeons, and postoperative results will be used for the following studies to correlate postoperative positional changes with IAND.

Surgical Management of Laterognathia in Orthofacial Surgery

INTRODUCTION

Each year around the world, various surgical procedures are carried out with the goal of correcting laterognathia; both the intraoral vertical ramus osteotomy (IVRO) and bilateral sagittal split ramus osteotomy (OSB) have been the most used techniques in mandibular surgery. These techniques have advantages and disadvantages; for example the advantages of the OSB include: increased coefficient of friction between bony segments, for both the forward and the retroposition, as well as decrease in the time of intermaxillary fixation (IMF). Disadvantages include injury to the inferior alveolar nerve (IAN), hemorrhage, bad split, among others. The advantages of IVRO include decrease of possibility of injury to the IAN, ease of implementation of the technique, a lower incidence of hemorrhage and the short duration of the surgical procedure. Their disadvantages include: lower coefficient of friction between bony segments, requires a relatively long period of IMF. The combination between the techniques of mandibular osteotomy for the correction of minor 10 mm laterognathia is the ideal treatment, since it avoids potential recurrence.

MATERIALS AND METHODS

We describe two cases of patients with laterognathia greater than 6 mm associated with maxilla deformity, which were treated with combined osteotomies. At Maxillofacial Surgery Service, Specialty Hospital, National Medical Center XXI Century, we describe the advantages and disadvantages, pre and postoperative nosocomial, by comparing them with the reports of the literature.

CONCLUSION

The combination of techniques in the correction of laterognathias greater than 4 mm (smaller than 10 mm) is the ideal treatment, eliminating problems of articular compression, recurrence and damage to the alveolar nerve.

An In Vitro Comparison Study of the Use of a Drill or a Saw in the Hunsuck-Dal Pont Modification of the Obwegeser Sagittal Split Osteotomy in Pig Mandibles

PURPOSE

Fracture lines in unfavorable locations are referred to as "bad splits" in a mandibular sagittal split osteotomy (SSO). Several modifications of the technique by Obwegeser have been introduced to minimize this risk. This in vitro study was performed to determine whether the shape of the osteotomy cut affects the torque and the fracture pattern of an SSO in pig mandibles.

MATERIALS AND METHODS

In a split-mouth model, 16 mandibles were split according to the Hunsuck-Dal Pont modification of the Obwegeser technique. Using an oscillating saw, sharp-edged osteotomies were created on one side of the mandible and round-edged osteotomies were created on the contralateral side using a Lindemann bur. Torque forces were measured during the splitting, and the lingual fracture pattern of each split was classified.

RESULTS

Torque forces were significantly (P < .05 by paired t test) decreased by 0.77 N-m (15.6%) when a saw was used for the osteotomy. In the 2 groups, fractures were produced along the mandibular canal. The mandible was more often completely fractured, including the lower mandibular border, when the fracture was created with an oscillating saw (P = .06 by Pearson χ² test). No correlation was found between the torque used and the fracture pattern.

CONCLUSION

Compared with round-edged osteotomies, sharp-edged osteotomies in pig mandibles facilitated the Hunsuck-Dal Pont modification of the Obwegeser sagittal splitting procedure and produced predictable results with decreased torque.

Bimaxillary Orthognathic Approach to Correct Skeletal Facial Asymmetry of Hemifacial Microsomia in Adults

BACKGROUND

Hemifacial microsomia (HFM) is the second most common congenital craniofacial deformity after cleft lip and palate. Distraction osteogenesis (DO) is regarded as an alternative and efficient treatment option for patients with HFM. However, DO was not proven effective for all cases, and the results of long-term follow-up were not satisfactory as expected. Compared with DO, the orthognathic surgery approach may offer more stable clinical outcomes for this kind of disease. The purpose of this study is to evaluate the long-term clinical and radiographic outcome of bimaxillary orthognathic surgery in the treatment of adult HFM.

METHODS

Eight patients with HFM who had undergone bimaxillary orthognathic surgery between 2008 and 2012 were included in the study. The surgical procedures included Le Fort I osteotomy, inverted-L osteotomy, sagittal split ramus osteotomy, genioplasty, and iliac bone grafting. Pre- and postoperative orthodontic treatments were performed, respectively. Clinical and radiographic examinations were carried out to assess postoperative outcomes.

RESULTS

No obvious complications appeared postoperatively and no recurrences occurred during follow-up. All patients obtained satisfactory aesthetic results. Marked improvement in facial contour and occlusion were observed. Plain radiographs showed that the height ratios between the affected and unaffected ramus were ameliorated significantly.

CONCLUSION

The bimaxillary orthognathic approach to correct the deformity of adult HFM can obtain stable results in the long-term follow-up, and should be considered as a priority method for the treatment of adult patients with dentofacial deformity.

LEVEL OF EVIDENCE V

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In vitro comparison of the sagittal split osteotomy with and without inferior border osteotomy

PURPOSE

By adding an osteotomy of the inferior border of the mandibular body to the classic sagittal split osteotomy, the authors expected to prevent unfavorable splits and damage to the inferior alveolar nerve.

MATERIALS AND METHODS

Thirty-five human mandibles were used to perform 70 sagittal split osteotomies as an in vitro study. Conducted as a split-mouth model, each mandible was split at the midline. One side of the mandible was split using the traditional Obwegeser-Dal Pont technique, and the other side was split in the same manner with an additional osteotomy of the inferior mandible border. The torque used to split the mandible was measured, and the fracture line of the mandible was recorded.

RESULTS

The average torque associated with the original technique was 1.38 Nm (standard deviation, 0.60 Nm), with a fracture line along the mandibular canal. The average torque required to split the hemimandible with the modified technique was 1.02 Nm (standard deviation, 0.50 Nm), a significant (P < .001) difference, with a fracture line parallel to the posterior ramus of the mandible. The fracture pattern depended significantly on the technique used (P < .001), but not on the applied torque force.

CONCLUSION

By adding an osteotomy of the inferior mandibular border to the sagittal split osteotomy, less torque was needed to split the mandible. The fracture line was more predictable, even when all the surgical manipulations were performed at a safe distance from the inferior alveolar nerve.

The modifications of the sagittal ramus split osteotomy: a literature review

BACKGROUND

In 1953, the sagittal ramus split osteotomy was introduced by Obwegeser. For many years, and in some countries still, this technique has defined the term oral and maxillofacial surgery.

METHODS

The basic design of the sagittal ramus split surgical procedure evolved very quickly. The original operation technique by Obwegeser was shortly after improved by Dal Pont's modification. The second major improvement of the basic technique was added by Hunsuck in 1967. Since then, the technical and biological procedure has been well defined. Resolution of the problems many surgeons encountered has, however, taken longer. Some of these problems, such as the unfavorable split or the damage of the inferior alveolar nerve, have not been satisfactorily resolved.

RESULTS

Further modifications, with or without the application of new instruments, have been introduced by Epker and Wolford, whose modification was recently elaborated by Böckmann. The addition of a fourth osteotomy at the inferior mandibular border in an in vitro experiment led to a significant reduction of the torque forces required for the mandibular split.

CONCLUSIONS

The literature was reviewed, and the last modifications of the successful traditional splitting procedure are presented narrowly. It indicates the better the split is preformatted by osteotomies, the less torque force is needed while splitting, giving more controle, a better predictability of the lingual fracture and maybe less neurosensory disturbances of the inferior alveolar nerve.

Evaluation of the mandibular split patterns in sagittal split ramus osteotomy

PURPOSE

To evaluate the split patterns of the mandibular ramus in sagittal split ramus osteotomy (SSRO) using cone-beam computed tomography (CBCT) and examine the related anatomic features that may be associated with these split patterns.

PATIENTS AND METHODS

The authors designed and implemented a retrospective cohort study and enrolled a sample composed of consecutive patients with different maxillofacial deformities who underwent an SSRO from July 2011 through October 2012 at the Department of Orthognathic Surgery at the Tianjin Stomatological Hospital of Nankai University. The split patterns, which were selected at random at 1 side per patient, were evaluated by CBCT as the outcome variable 1 month after the operation. The predictor variable was composed of a set of heterogeneous anatomic variables that could be associated with the split patterns. Type I split was defined as a split at the lingual side near the mylohyoid sulcus. Type II split was defined as a split at the posterior border of the mandibular ramus. Appropriate bivariate and regression statistics were computed, and the level of statistical significance was set at a P value less than .05.

RESULTS

One hundred thirty patients with different maxillofacial deformities (62 male and 68 female; mean age, 23 yr) underwent an SSRO. Two types of split patterns of the mandibular ramus were observed in SSRO: a split at the lingual side near the mylohyoid sulcus, which occurred in 75.38% of patients, and split at the posterior border region of the mandibular ramus, which occurred in 24.62% of patients. No fracture lines were observed through the mandibular canal. The thickness of the lingual cortical bone between the mandibular canal and the posterior border of the ramus was significantly associated with the split patterns (P < .05). The thickness of the cortical bone in the posterior border of the ramus, the degree of the mandibular angle, and the shapes of the mandibular ramus in the axial plane also were found to influence these split patterns. There was no meaningful association between the split patterns and a patient's age and gender.

CONCLUSION

The split patterns of the mandibular ramus during SSRO were influenced by some anatomic features of the mandibular ramus. Therefore, examining the anatomy of the mandible with CBCT before surgery may play an important role in predicting the split patterns of the mandibular ramus during SSRO.

Influence of osteotomy procedure and surgical experience on early complications after orthognathic surgery in the mandible

INTRODUCTION

This study evaluated the influence of osteotomy procedure and surgical experience on early complication rates following orthognathic surgery in the mandible.

MATERIALS AND METHODS

In a retrospective study, patients who underwent a mandibular osteotomy (Obwegeser-Dal Pont (ODP) and Hunsuk-Epker (HE)) were included. Incidence of "bad splits", "bleeding episodes", "delayed wound healing", "failed osteosynthesis" and "nerve lesions" at 2 months post-operatively were recorded. Surgical experience was classified as: beginner (<10), intermediate (10-40) and expert (>40). Complications were correlated to the surgical approach and the experience level of the surgeon.

RESULTS

400 patients were included. 200 underwent a bimaxillary approach. 186 patients were operated using the ODP technique, 214 according to HE. Multivariate analysis confirmed significantly more unwanted fractures and bleeding events for ODP when compared to HE (p = 0.28, p = 0.003). Experienced surgeons had more osteosynthesis failures (0.047) and significantly more nerve lesions than the other groups (p = 0.01).

DISCUSSION

The HE osteotomy showed a more reliable fracture mechanism with less relevant bleeding episodes. Differences between the surgeons of varying training status were marginal with exception of a higher rate of osteosynthesis failure and temporary hypoesthesia in the experienced group.

Lower-level laser therapy improves neurosensory disorders resulting from bilateral mandibular sagittal split osteotomy: a randomized crossover clinical trial

Bilateral sagittal split osteotomy (BSSO) is a technique commonly used to correct mandibular disproportion but many patients experience hypoaesthesia of the inferior alveolar nerve (IAN). The purpose of this study was to verify the effectiveness of using a low-level laser therapy protocol after BSSO. The 10 patients in our study, who underwent BSSO with Le Fort I osteotomy and had low-level laser therapy on one side of the jaw, were evaluated over a period of 60 days. The data for the treated and non-treated sides were compared post-operatively. At 15, 30 and 60 days after surgery, when sensitivity was recovered on both sides. On the treated side, recovery was faster and was almost complete at the time of the last evaluation. We suggest that this lower-level laser therapy protocol can improve tissue response and accelerate the recovery of neurosensory disorders following BSSO. (NCT01530100).