Bilateral Sagittal Split Osteotomy Advancement Research Articles

Reliability of 3D Stereophotogrammetry for Measuring Postoperative Facial Swelling.

This study aimed to determine the reliability of three-dimensional (3D) stereophotogrammetry as a measurement instrument for evaluating soft tissue changes in the head and neck area. Twelve patients received a bilateral sagittal split osteotomy (BSSO). Test and retest 3D photographs were captured within the first three postoperative weeks, and a reference 3D photograph was capture at three months postoperatively. Distance measurements, mean and root mean square of the distance map, and volume differences were obtained. Reliability of these parameters was assessed by intraclass correlation coefficients (ICCs), standard error of measurement (SEM), and smallest detectable change (SDC). All distance measurements had an ICC > 0.91, and the distance map parameters and volume differences showed ICCs > 0.89. The neck region presented the largest SEMs (5.09 mL) and SDC (14.1 mL) for the volume difference. In conclusion, 3D stereophotogrammetry is reliable for distance and volume measurements of soft tissues in patients after a BSSO advancement.

Risk factors for lower border notching after bilateral mandibular sagittal ramus advancement: three-dimensional evaluation

Bilateral sagittal split osteotomy (BSSO) mandibular advancement can cause mandibular lower border notching (MLBN). The objective of this study was to calculate the incidence of MLBN and identify risk factors. This single-centre, retrospective study was performed between January 2018 and November 2020, in the Maxillofacial Surgery Department, Centre Hospitalier Universitaire, Caen. Patients who underwent BSSO advancement and had cone beam computed tomography (CBCT) scans obtained preoperatively, immediately postoperative (within 1 week), and late postoperative (≥1 year) were included. Measurements were made on the CBCT images. A total of 113 patients (226 operated sides) were enrolled. Mean age at the time of surgery was 17 years; 66.4% of patients were female and 33.6% were male. MLBN was observed on 35 operated sides (15.5% of sides). Advanced age (P = 0.002) and the degree of mandibular advancement (P = 0.008) were determined to be risk factors for developing MLBN. Sex, the operated side, third molar removal, and genioplasty were not associated with an increased occurrence of MLBN. Older patient age at the time of surgery and the requirement for a large advancement should be taken into consideration by the surgeon in order to reduce the risk of MLBN by using a modified BSSO procedure or bone grafting.

Three-Dimensional Pharyngeal Airway Space Changes Following Isolated Mandibular Advancement Surgery in 120 Patients: A 1-Year Follow-up Study.

Lack of evidence exists related to the three-dimensional (3D) pharyngeal airway space (PAS) changes at follow-up after isolated bilateral sagittal split osteotomy (BSSO) advancement surgery. The present study assessed the 3D PAS changes following isolated mandibular advancement at a follow-up period of 1 year. A total of 120 patients (40 males, 80 females, mean age: 26.0 ± 12.2) who underwent BSSO advancement surgery were recruited. Cone-beam computed tomography (CBCT) scans were acquired preoperatively (T0), immediately following surgery (T1), and at 1 year of follow-up (T2). The volume, surface area, and minimal cross-sectional area (mCSA) of the airway were assessed. The total airway showed a 38% increase in volume and 13% increase in surface area from T0 to T1, where the oropharyngeal region showed the maximum immediate change. At T1–T2 follow-up, both volumetric and surface area showed a relapse of less than 7% for all sub-regions. The mCSA showed a significant increase of 71% from T0 to T1 (p < 0.0001), whereas a non-significant relapse was observed at T1–T2 (p = 0.1252). The PAS remained stable at a follow-up period of 1 year. In conclusion, BSSO advancement surgery could be regarded as a stable procedure for widening of the PAS with maintenance of positive space at follow-up.

Neurosensory deficit of inferior alveolar nerve after bilateral sagittal split osteotomy, advancement versus setback: An observational study

Aim: The aim of this study was to compare the incidence of inferior alveolar sensory deficits, its association with various intraoperative nerve encounter status and the possible outcome of neurosensory deficits (NSDs) of the bilateral sagittal split osteotomy (BSSO) advancement, and setback procedures. Materials and Methods: This was an observational study among the oral and maxillofacial surgeons of south India who had expertise in the field of orthognathic surgery. A self-administered questionnaire (SAQ) with closed-ended answers was prepared using Google Forms (Google Inc.), pretested, and was sent to the prospective participants selected by convenience sampling through various social media outlets. A total of 1600 participants were included, and the sample size was estimated by the formula = 4pq/d2 and assessed 800 cases each of BSSO setback and advancement surgeries. Since the study focused on the NSD of the inferior alveolar nerve (IAN) post-BSSO, the advancement procedures, setback procedures, and various nerve encounter statuses were considered the variables. All the study procedures were performed as per the ethical guidelines laid down by the Declaration of Helsinki (October 2013) after approval by the Institutions Human Ethics Committee (IHEC), Rajah Muthiah Medical College, Annamalai University. Results: Chi-squared test was used to assess the qualitative variables. The incidence of NSDs was 17.7% in the setback cases and with respect to advancement, the NSD was 15.1%, P < 0.08 indicating no statistically significant difference. When comparing the independent nerve encounter status and NSDs between the groups, the cases where the nerve got transected post osteotomy, necessitating repair as well as those needing dissection due to its presence in the proximal fragment presented with a higher incidence of NSDs which was clinically and statistically significant, P < 0.001. Conclusion: No significant difference was observed in the NSD after mandibular sagittal split advancement and setback procedures. The status of the IAN intraoperatively can influence the incidence of postoperative prolonged IAN NSDs.

Three-dimensional evaluation of distal and proximal segment skeletal relapse following isolated mandibular advancement surgery in 100 consecutive patients: A one-year follow-up study

The aim of this study was to perform a three-dimensional evaluation of the skeletal relapse of the proximal and distal mandibular segments following isolated bilateral sagittal split osteotomy advancement surgery. One hundred consecutive patients (mean age 25.8±11.7 years), comprising 65 female patients (mean age 26.4±12.1 years) and 35 male patients (mean age 24.6±11.0 years) requiring mandibular advancement without genioplasty, were enrolled prospectively in the study. Cone beam computed tomography scans were acquired for each patient at three time-points: preoperatively, immediately (1–6 weeks) after surgery, and 1 year after surgery. A validated tool was utilized to assess the surgical movement and relapse. Based on percentage, the majority of the distal and proximal translational and rotational movements relapsed within the range of ≤2mm and ≤2°. The distal segment revealed a significant relapse in a posterior, inferior, and clockwise pitch direction. Both left and right proximal segments showed a significant translational relapse in the medial, posterior, and superior direction. Amongst the rotational parameters, proximal segments relapsed significantly in clockwise pitch, clockwise roll, and counterclockwise yaw direction. Overall, both distal and proximal bone segments showed a clinically acceptable translational and rotational stability. The proximal segments torqued towards their original position with a reduction of flaring.

Evaluation of the Pharyngeal Airway Space Before and after Bi-Lateral Sagittal Split Osteotomy Surgery using Three-Dimensional Cone Beam Computed Tomography

Objectives: To evaluate the changes in the pharyngeal airway space (PAS) before and after bi-lateral sagittal split osteotomy (BSSO) surgery using a three-dimensional cone-beam computed tomography (3D-CBCT). Material and Methods: The sample consisted of patients (n=7), aged between 21-30 years, having a skeletal Class II with retrognathic mandible and orthognathic maxilla who underwent orthodontic treatment and were advised for BSSO advancement surgery. Pre-surgical CBCT scans were taken a week before the surgery (T0) and the post-treatment records, three months after the surgery (T1). The 3D PAS was reconstructed from the CBCT scans, and the volumetric changes were evaluated.

Do Patients With Different Mandibular Plane Angles Have Different Time to Relapse After Bilateral Sagittal Osteotomy With Mandibular Advancement?

This study sought to answer the following question: Do patients with different mandibular plane angles (MPAs) have a different time to relapse after mandibular advancement with bilateral sagittal split osteotomy? We performed a retrospective cohort study of patients who underwent bilateral sagittal split osteotomy advancement at Massachusetts General Hospital between 2005 and 2017. The primary predictor variable was MPA, categorized as low (<25°), medium (between 25° and 35°), or high (>35°). The outcome variable was time to relapse (≥2-mm posterior change at the B point). Other covariates included gender, age, temporomandibular joint symptoms, bimaxillary surgery, direction of mandibular rotation, magnitude of advancement, genioplasty, and fixation method. Time to relapse was estimated using the Kaplan-Meier method. Cox and parametric regressions for interval-censored data were performed. P<.05 was considered statistically significant. The sample was composed of 58 patients (40 female patients), with a mean age of 26.1±4.9years, grouped as follows: low MPA, n=15; medium MPA, n=26; and high MPA, n=17. Clinically significant relapse was found in 18 patients (31%).Age, temporomandibular joint symptoms, counterclockwise rotation, and magnitude of advancement were statistically significantly different among the 3 groups. When we assessed time to relapse, the Kaplan-Meier method showed that high-MPA patients had a longer mean time at risk and higher estimated probabilities of relapse at different time points compared with low- and medium-MPA patients (P<.05). However, this association was not significant in Cox and parametric regressions. Our results suggest that clinically significant relapse was found during the first postoperative year in low-MPA patients and from 2 to 5years postoperatively in high-MPA patients. Multivariate regression analyses did not show a significant association between MPA and time to relapse, suggesting that other covariates may play a role in the observed time to relapse.

Natural head posture changes after maxillomandibular procedures – A prospective study

Purpose of the Study: The aim of this study is to evaluate the natural head posture changes in the individuals after orthognathic surgery assessed using cone-beam computed tomography (CBCT) scan. Materials and Methods: The study was conducted in the age group above 18 years who underwent mandibular advancement for the correction of the skeletal deformity. The difference was evaluated in cases with the help of CBCT scan which was taken preoperatively and 3 months postoperatively. The inclusion criteria were patients undergoing mandibular advancement with or without maxillary procedures. The CBCT scan was taken in a natural head position with lips in a relaxed position and without any other tongue movements like swallowing. The exclusion criteria include patients with pharyngeal pathology, syndromic conditions, and history of orthognathic surgery. The head posture was determined by measuring the craniocervical angle (CCA) before and after surgery to evaluate the changes. The study was divided among bilateral sagittal split osteotomy (BSSO) advancement cases and maxillomandibular procedures. The statistical analysis was done using a paired t-test. Results: The head posture changes present in mandibular advancement cases show a decrease in the angulation of CCA in both types. The P value of head posture in BSSO advancement cases was 0.25, and for maxillomandibular cases, it was 0.007. Conclusion: The study was concluded by showing a decrease in the angulation of the CCA after orthognathic surgery. This shows improvement in the facial profile and structural positions.

Changes in natural head position in response to mandibular advancement

We investigated the change in the natural head position and its relation to the change in the mandibular position in patients with mandibular hypoplasia. Forty-one patients treated by orthognathic surgery were divided into three groups: bilateral sagittal split osteotomy (BSSO) advancement (n=8); BSSO advancement with genioplasty (n=12), and Le Fort I osteotomy with BSSO advancement (n=21). Cone-beam computed tomographic (CT) datasets were collected preoperatively and six weeks postoperatively. The natural head position was measured using the craniocervical angle and the distance from the second vertebra to the frontal plane, and the mandibular position was measured using the craniomandibular angle and the distance from the mandible to the frontal plane. Repeated measures two way ANOVA was used to assess the significance of differences between the angular and linear measurements, and Pearson’s correlation coefficient to assess those between the change in the mandibular position and the natural head position. The craniomandibular angle increased and the mandible to frontal plane distance decreased, as planned; the craniocervical angle increased, and the distance from the second vertebra to the frontal plane decreased in all three groups. ANOVA showed a significant difference in the time factor (preoperative compared with postoperative) but no significant differences between the groups or interaction (time multiplied by group) factors. There was a significant correlation between the change in mandibular position and the change in the natural head position. Changes in the natural head position after correction of mandibular hypoplasia are correlated with the change in the mandibular position, regardless of whether a genioplasty or Le Fort I osteotomy was done.

The use of SPHARM-PDM and mean latitude axis to evaluate airway changes.

To introduce new 3-D imaging techniques to characterize shape and volume changes of the oropharyngeal space after bilateral sagittal split osteotomy (BSSO) advancement. Longitudinal cone-beam computed tomography (CBCT) scans were obtained for 20 patients undergoing BSSO advancement at three time points (T1 = presurgery, T2 = splint removal, and T3 = 1 year after surgery). Segmentation of the airway was performed using the following boundaries: hard palate/posterior nasal spine superiorly and lower border of C3 to the base of the epiglottis inferiorly. For shape measurements, point-based correspondent models and mean latitude axis were obtained for all the data using SPHARM-PDM software. All 3-D correspondent models were rigidly registered using Procrustes alignment. Absolute distance maps and corresponding vector maps were calculated to show shape and vector differences between each correspondent point. Mean latitude axis is a new imaging method to calculate minimum cross-sectional areas along the long axis of the airway independent of head position/alignment. The airway volume increased (P < .01) after BSSO advancement (2973.9 mm3 ± 27882.0) and was stable (-439.9 mm3 ± 3308.8) 1 year post-op. 3-D color maps and semitransparency overlays showed more lateral than anteroposterior expansion of the airway after BSSO advancement. Mean latitude axis was used to measure minimum cross-sectional area, showing a statistically significant increase (52.7 mm2 ± 46.7) (P < .01) after surgery and remained stable (-10.3 mm2 ± 43.3) 1 year after surgery. SPHARM-PDM and mean latitude axis are useful tools to assess airway shape change. BSSO advancement produces a significant increase in pharyngeal airway volume and minimum cross-sectional area. The airway space increased more transversely than anteroposteriorly.

A new 3D approach to evaluate facial profile changes following BSSO.

The purpose of this study was to evaluate changes in the soft tissue facial profile in patients who underwent bilateral sagittal split osteotomy (BSSO) using 3D stereophotogrammetry and principal component analysis (PCA). Twenty-five female patients (mean age, 24 years; range: 18-26) who underwent BSSO and 70 female controls (mean age, 24 years; range: 18-26) participated in this prospective study. Three-dimensional photographs of all patients and controls were acquired. PCA was used to determine the unique morphological variations (UV) between the dysgnathic group and the control group. The most prominent facial morphologic difference between the dysgnathic group and the control group (UV1) was a clockwise rotation of the mandible and shortening of the lower part of the face, followed by a protrusion of the upper lip, retrusion of the mandible and over-accentuation of the labial-mental fold (UV2). The combination of UV1 and UV2 could be used to simulate a typical Class II facial profile and to automatically differentiate between the preoperative patients, postoperative patients and the control group. Based on the applied PCA method, this study demonstrated that BSSO advancement surgery could only provide a suboptimal improvement of the soft tissue facial profile in the majority of cases.

Skeletal stability following mandibular advancement with and without advancement genioplasty

The correction of most cases of skeletal class II mandibular deficiency requires surgical advancement of the mandible for treatment of the malocclusion. Often genioplasty is included in the procedure to improve the soft tissue profile. Long-term skeletal stability is an important goal for the surgeon and orthodontist following bilateral sagittal split osteotomy (BSSO) and is influenced by the muscles attached to the mandible. Following the surgical advancement of the mandible, the suprahyoid muscle complex is stretched and even more so when the procedure is combined with surgical advancement of the chin. This retrospective comparative study determined the long-term skeletal stability of patients who had undergone surgical advancement of the mandible by means of BSSO with an advancement genioplasty, compared to those who had undergone mandibular advancement surgery (BSSO) without an advancement genioplasty. This study concluded that the postoperative hard tissue relapse following BSSO advancement, with or without genioplasty, was clinically insignificant.

3D quantitative analysis of condylar morphology and its effects on skeletal relapse following bilateral sagittal split advancement osteotomies

Objectives: The objective of the current study is to quantify the postoperative 3D morphologic changes of condyles using cone beam computed tomography (CBCT) and evaluate the subsequent effects on skeletal stability following a BSSO advancement of the mandible.

Effect of mandibular advancement on the natural position of the head: a preliminary study of 3-dimensional cephalometric analysis

Our aim was to investigate the potential effect of advancement by bilateral sagittal split osteotomy (BSSO) on the natural position of the head by using 3-dimensional cephalomentric analysis. Seven consecutive patients who had had only BSSO advancement, and had had preoperative and 6-week postoperative cone beam computed tomography (CT) scans, were recruited to this retrospective study. Two variables, SNB and SNC2, were used to indicate the craniomandibular alignment and craniocervical inclination, respectively, in the midsagittal plane. Using 3-dimensional cephalometric analysis software, the SNB and the SNC2 were recorded in volume and measured in the midsagittal plane at 3 independent time-points. The reliability was measured and a paired t test used to assess the significance of differences between the means of SNB and SNC2 before and after operation. The 3-dimensional cephalometric measurement showed good reliability. The SNB was increased as planned in all the mandibles that were advanced, the cervical vertebrae were brought forward after BSSO, and the SNC2 was significantly increased in 6 of the 7 patients. Three-dimensional cephalometric analysis may provide an alternative way of assessing cephalometrics. After BSSO advancement, the natural position of the head changed by increasing the craniocervical inclination in an anteroposterior direction.

Static and dynamic loading of mandibular condyles and their positional changes after bilateral sagittal split advancement osteotomies

This study analysed the effects of change of direction of masseter (MAS) and medial pterygoid muscles (MPM) and changes of moment arms of MAS, MPM and bite force on static and dynamic loading of the condyles after surgical mandibular advancement. Rotations of the condyles were assessed on axial MRIs. 16 adult patients with mandibular hypoplasia were studied. The mandibular plane angle (MPA) was <39° in Group I (n=8) and >39° in Group II (n=8). All mandibles were advanced with a bilateral sagittal split osteotomy (BSSO). In Group II, BSSO was combined with Le Fort I osteotomy. Pre and postoperative moment arms of MAS, MPM and bite force were used in a two-dimensional model to assess static loading of the condyles. Pre and postoperative data on muscle cross-sectional area, volume and direction were introduced in three-dimensional dynamic models of the masticatory system to assess the loading of the condyles during opening and closing. Postsurgically, small increases of static condylar loading were calculated. Dynamic loading decreased slightly. Minor rotations of the condyles were observed. The results do not support the idea that increased postoperative condylar loading is a serious cause for condylar resorption or relapse.

Patients’ perceptions of improvements after bilateral sagittal split osteotomy advancement surgery: 10 to 14 years of follow-up

The aims of this study were to determine reasons for orthodontic-surgical treatment, to quantify the perceptions of possible improvement 10 to 14 years after treatment, and to assess factors that affect treatment satisfaction and socio-dental impacts on quality of life. The participation rate was 36 of 78 patients; their mean age was 45.7 years (SD, 10.7 years; range, 29-62 years). The presurgical anatomic occlusions were measured on dental casts. Visual analog scales allowed the participants to rate their perceived treatment outcome on 7 oral health-related items. A 3-point scale rated satisfaction with orthodontic-surgical treatment. The oral impact of daily performances index was included to assess socio-dental impacts on quality of life. Most responders reported improvements on the 7 items. The most significant change was reported for chewing. "Very satisfied" with the treatment was reported by 13 responders; 19 of 36 persons were "reasonably satisfied." Reporting "very satisfied with treatment" was 8 times more likely when peers had noticed a changed in the participant's appearance after surgery. Sex was significantly associated with quality of life. The most frequently reported reason for treatment was to improve chewing, and the item that showed the most pronounced improvement was also chewing. Most responders were only reasonably satisfied with the treatment. Whether peers noticed a change in appearance after treatment was a significant factor affecting both treatment satisfaction and reporting a good quality of life.

Soft Tissue Profile Changes After Bilateral Sagittal Split Osteotomy for Mandibular Advancement: A Systematic Review

The purpose of the present systematic review was to evaluate the soft tissue/hard tissue ratio in bilateral sagittal split advancement osteotomy (BSSO) with rigid internal fixation (RIF) or wire fixation (WF). The databases PubMed, Medline, CINAHL, Web of Science, Cochrane Library, and Google Scholar Beta were searched. From the original 711 articles identified, 12 were finally included. Only 3 studies were prospective and 9 were retrospective. The postoperative follow-up ranged from 3 months to 12.7 years for RIF and 6 months to 5 years for WF. The short- and long-term ratios for the lower lip to lower incisor for BSSO with RIF or WF were 50%. No difference between the short- and long-term ratios for the mentolabial-fold to point B and soft tissue pogonion to pogonion could be observed. It was a 1:1 ratio. One exception was seen for the long-term results of the soft tissue pogonion to pogonion in BSSO with RIF; they tended to be greater than a 1:1 ratio. The upper lip mainly showed retrusion but with high variability. Despite a large number of studies on the short- and long-term effects of mandibular advancement by BSSO, the results of the present systematic review have shown that evidence-based conclusions on soft tissue changes are still unknown. This is mostly because of the inherent problems of retrospective studies, inferior study designs, and the lack of standardized outcome measures. Well-designed prospective studies with sufficient sample sizes that have excluded patients undergoing additional surgery (ie, genioplasty or maxillary surgery) are needed.

Soft tissue changes in skeletal class II patients treated with bilateral sagittal split osteotomy advancement surgery

Abstract (J Korean Assoc Oral Maxillofac Surg 2010;36:94-9) Ⅰ. 서론 악교정수술은골격성부정교합을가진환자들의안모를극적으로변화시킴으로써골격성부정교합환자들이심미적이고기능적인안모를가질수있도록해왔다. 여러가지악교정술식들이이러한목적을위하여개발되고발전되어왔으며, 그중하악상행지시상분절술은악골의전진과후퇴에모두적용가능하여구강악안면외과의들은표준적인술식으로받아들이고있다 1 . 이러한악교정술식들의목적중심미성의회복은가장중요한요소중하나이며, 술후만족할만한심미적결과를얻기위해서는수술에따른연조직의변화를허용가능한범위내에서예측하는것이필요하다. 이를위해서치료계획의수립시경조직계측뿐만아니라연조직계측을필수적으로포함하여야한다. 또한적절한치료계획을수립하기위해서는이러한예측을수치화하여야보다예측성있는치료계획의수립이가능하다.앵글씨부정교합분류중에서골격성II급부정교합은상악에대하여하악이원심에위치한상태로이의개선을위하여보통하악의전진을요하며, 이때하악상행지시상분절술과이부성형술을빈번하게선택한다 2-3 . 골격성II급부정교합의치료에따른연조직변화는서양인에서는적지않게보고되고있지만 1,2,4,6-8 , 동양인의경우골격성III급부정교합환자의연조직변화에대한연구에비하여골격성II급부정교합의연조직변화에관한연구가매우부족하다. 이에본연구는골격성II급부정교합환자에서하악상행지시상분절술을이용한하악전진술전, 후의하순및이부의경조직및연조직의수평적변화량과하순길이의수직적변화량을계측하여악교정수술에따른안정성과예후를평가하는데도움이되고자한다. 박재억137-044 서울시서초구반포동505가톨릭대학교의과대학서울성모치과병원구강악안면외과학교실Je-Uk ParkDepartment of Oral and Maxillofacial Surgery, College of Medicine, The Catholic University505 Banpo-dong, Seocho-gu, Seoul, 137-044, KoreaTEL: +82-2-2258-6291 FAX: +82-2-537-2374E-mail: jupark@catholic.ac.kr

Relapse following bilateral sagittal split osteotomy with rigid internal fixation

PubMed, Ovid (including OLDMedline), Google Scholar Beta, the Cochrane Library and references of identified articles were used to identify data sources. Studies were included if they involved more than 10 adults, a followup of greater than 6 months, and mandibular advancement by bilateral sagittal split osteotomy (BSSO) with rigid internal fixation. Studies that included another surgical intervention (eg, Le Fort I osteotomy), syndromic or medically compromised patients, case reports, case series, descriptive studies, review and opinion articles or abstracts were excluded. The following data items were extracted: year of publication, study design, followup, number and mean age of patients, ethnic background of patients, number of surgeons operating, type of rigid internal fixation, use of MMF (maxillomandibular fixation), use of genioplasty, mean advancement, mean relapse, correlations between relapse and different variables, proportion of patients with more than 2 mm of sagittal relapse, and authors' conclusions. A quality assessment of the included studies was undertaken following selection. Studies were categorised as medium or low quality based on study design, sample size, selection descriptions, withdrawals, valid methods, confounding factors, method error analysis, blinding in measurements and adequate statistics. None of the included studies met the criteria of the high-quality category. Twenty-four articles were finally included, comprising six prospective and 18 retrospective studies. The range of postoperative study records was 6 months to 12.7 years. The short-term relapse for bicortical screws was between 1.5 and 32.7%, for miniplates between 1.5 and 18.0%, and for bioresorbable bicortical screws between 10.4 and 17.4%, at point B (the deepest concavity on the anterior profile of the maxilla). The long-term relapse for bicortical screws was between 2.0 and 50.3%, and for miniplates between 1.5 and 8.9%, at point B. To obtain reliable scientific evidence, further short-term and long-term research into BSSO advancement with rigid internal fixation should exclude additional surgery, ie, genioplasty or maxillary surgery, and include a prospective study or randomised controlled clinical trial (RCT) design with correlation statistics.

3D evaluation of the lingual fracture line after a bilateral sagittal split osteotomy of the mandible

The purpose of this prospective observational study was to evaluate whether cone beam CT (CBCT) is a useful tool for analyzing the fracture line in a bilateral sagittal split osteotomy (BSSO). The patient group consisted of 40 consecutive patients (9 males and 31 females) with a mandibular hypoplasia who underwent a BSSO advancement (Hunsuck modification; n=80 splits) between September 2006 and July 2008. The mean age at the time of surgery was 34 years (range 17-61 years). A newly developed lingual split scale was used to categorize the path of the fracture line on the lingual side of the ramus based on one-day postoperative data sets reconstructed from CBCT data. Although all splits (n=80) were performed according to the standardized protocol, only 51% of the fracture lines run according to the Hunsuck's description, whereas 33% ran through the mandibular canal and 16% split otherwise. The split pattern was influenced by the length of the medial osteotomy (p=0.01). In conclusion, 3D imaging is a useful tool for analyzing the surgical outcome of a BSSO and has the potential to provide substantial data on the position of the proximal segments as a result of the lingual fracture line.