Intraoral Vertical Ramus Osteotomy Procedure and Technique

Determining the position of the lingula and the mandibular foramen using the antilingula in orthognathic surgery

BACKGROUND

The antilingula located on the lateral surface of the mandibular ramus has been served as a surgical landmark for the mandibular foramen on the medial surface for decades. However, whether the antilingula truly represents the lingula which is the bony prominence overlapping the mandibular foramen, or the foramen itself, is still unclear. This study thus aimed to examine the position of the antilingula in relation to three reference points: the lingula, the anterior and the posterior borders of the mandibular foramen, as well as to the reference plane used in the inferior alveolar nerve block, and to the posterior border of the mandible.

METHODS

This observational study was performed in 113 Thai dry mandibles. The antilingula were identified followed by transferring the reference points to the lateral surface. The distances from the antilingula to the reference points, the reference plane and the posterior border of the ramus were then measured. Chi-square test was calculated for side-dependency of the antilingula. Paired t-test was calculated for difference in measurements in left and right sides.

RESULTS

The antilingula could be identified in 92.48% of the mandibles with 86.67 - 90.00% accuracy and 86.67% reliability. There was no significant difference in the presence of the antilingula on left and right sides (p = 0.801). Only 2.5% and 0.83% of the antilingula correspond to the lingula and the anterior border of the mandibular foramen, respectively. However, 85% of the reference points were located within 11 mm radius. The antilingula was found located 2.80 mm inferior to the reference plane and 16.84 mm from the posterior border of the ramus.

CONCLUSIONS

The antilingula does not concur with the reference points on the medial surface. Our study also suggests that the safe area for vertical osteotomy is 11 mm posterior to the antilingula or at 30% of the length from the posterior border parallel to the occlusal plane. The use of more accurate techniques in localizing the mandibular foramen combined with the antilingula is more recommended than using the antilingula as a sole surgical guide.

Minimally Invasive Approaches in Orthognathic Surgery: A Narrative Review of Contemporary Techniques and their Clinical Outcomes

Maxillofacial surgery has evolved significantly, particularly in orthognathic procedures, shifting from invasive methods to minimally invasive techniques (MITs). Innovations, like 3D imaging, computer-aided simulations, piezoelectric surgery, and endoscopic assistance, have revolutionized patient care. These methods notably reduce bleeding, scarring, hospital stays, and recovery time, while enhancing surgical precision and outcomes. Our review focuses on modern MITs, including endoscopically assisted maxillomandibular advancement (EAMMA) and CAD/CAM technology. We conducted a thorough literature search, identifying 21 relevant articles from an initial pool of 423. The review evaluates the efficacy, complication rates, and long-term stability of these techniques, addressing challenges and future prospects. Emphasizing the significance of MI methods in orthognathic surgery, it advocates for further research and clinical adoption.

What are the Effects of Internal Fixation on Trigeminal Neurosensory Function and the Temporomandibular Joints Following Intraoral Vertical Ramus Osteotomy?

PURPOSE

Intraoral vertical ramus osteotomy (IVRO) has, traditionally, been accomplished without internal fixation, necessitating a period of maxillomandibular fixation (MMF). With advances in instrumentation, internal fixation of IVRO is feasible, obviating the need for MMF. The purpose is to investigate the effects of transoral internal fixation on the prevalence of third division trigeminal nerve (CNV3) injury, temporomandibular joint (TMJ) arthralgia, and surgical site bleeding following IVRO.

MATERIALS AND METHODS

A retrospective study was conducted on patients who underwent IVRO at Vanderbilt University Medical Center between January 2017 and December 2020. The primary predictor variable was fixation status-internal fixation versus MMF. The primary outcome variable was postoperative CNV3 neurosensory disturbance. The secondary outcome variables were TMJ arthralgia and surgical site bleeding. Statistical analysis included Fisher's exact test and McNemar's Chi-squared test.

RESULTS

Seventy two subjects (59 IVROs without internal fixation and 65 IVROs with internal fixation) were studied. The frequency of CNV3 neurosensory deficit was 0% in the IVRO without internal fixation group and 3.1% in the IVRO with internal fixation group (P = .49). Within group analysis showed a decreased frequency of postoperative TMJ arthralgia compared to preoperative records in both groups (IVRO without internal fixation group, P = .04 and IVRO with internal fixation group, P = .004). The frequency of active surgical site bleeding controlled with local measures was 1.7% in the IVRO without internal fixation group and 3.1% in the IVRO with internal fixation group (P = 1).

CONCLUSION

Internal fixation of IVRO is associated with low incidence of neurosensory deficit, TMJ arthralgia, and active surgical site bleeding.

The Unfavourable Split: a novel classification and an 11-year retrospective study looking at alternative methods for management of this well-known complication

An unfavourable split is a well-known complication following a sagittal split osteotomy (SSO) of the mandible. Our aim was to analyse all unfavourable mandibular splits that had occurred when carrying out a SSO with the aim to design a classification which can facilitate management. We carried out a retrospective study analysing all orthognathic surgery from January 2010 until April 2021. Data surrounding unfavourable splits during this period were specifically analysed. Orthognathic surgery during this period was performed by a single OMFS unit with osteotomies performed by a single surgeon and their trainee. The dataset included 311 patients who underwent either a bilateral sagittal split osteotomy (BSSO) or a bimaxillary osteotomy. There were 225 bimaxillary osteotomies and 86 BSSOs. Twenty-one patients had unfavourable splits following their BSSO with a total of 22 out of 622 sagittal split osteotomies over this 11-year period. Bilateral unfavourable splits occurred in one patient. These results correlate to an incidence rate of 6.8% of unfavourable splits following SSO's in an 11-year period. The results reveal common patterns of unfavourable splits to suggest a simple classification based on our results. This can be applied to any unfavourable splits in SSO which then allows the clinician to proceed with surgery and prevent abandonment of the procedure. It is classified as follows: Type 1 fractures where the mandibular condyle is attached to the proximal fragment; Type 2 fractures whereby the mandibular condyle is attached to the tooth-bearing segment; Type 3 fractures are lingual cortex fractures. Each of these fracture types has a specific management protocol, which we recommend is used in all unfavourable splits.

Surgical cutting guide and single plate fixation for intraoral vertical ramus osteotomy

With the advancement of digital technology over the last few decades, the use of virtual surgical planning and fabrication of surgical guides have tremendously improved the outcomes of various maxillofacial surgical procedures. The intraoral vertical ramus osteotomy (IVRO) is an orthognathic surgical procedure largely employed for mandibular setback in correcting dentofacial deformities. This study describes the design and application of a surgical cutting guide for IVRO. The guide can also be used to facilitate the placement of miniplate fixation. The initial experience at the authors' centre suggests that the guide has allowed the osteotomy to be performed with increased precision and confidence. Furthermore, the use of miniplate fixation decreased the period of maxillomandibular fixation. However, a larger series is required to evaluate the utility of this system more thoroughly.

Skeletal Stability after Mandibular Setback via Sagittal Split Ramus Osteotomy Verse Intraoral Vertical Ramus Osteotomy: A Systematic Review

Purpose: The purpose of present study was to review the literature regarding the postoperative skeletal stability in the treatment of mandibular prognathism after isolated sagittal split ramus osteotomy (SSRO) or intraoral vertical ramus osteotomy (IVRO). Materials and Methods: The articles were selected from 1980 to 2020 in the English published databases (PubMed, Web of Science and Cochrane Library). The articles meeting the searching strategy were evaluated based on the eligibility criteria, especially at least 30 patients. Results: Based on the eligibility criteria, 9 articles (5 in SSRO and 4 in IVRO) were examined. The amounts of mandibular setback (B point, Pog, and Me) were ranged from 5.53–9.07 mm in SSRO and 6.7–12.4 mm in IVRO, respectively. In 1-year follow-up, SSRO showed the relapse (anterior displacement: 0.2 to 2.26 mm) By contrast, IVRO revealed the posterior drift (posterior displacement: 0.1 to 1.2 mm). In 2-year follow-up, both of SSRO and IVRO presented the relapse with a range from 0.9 to 1.63 mm and 1 to 1.3 mm respectively. Conclusion: In 1-year follow-up, SSRO presented the relapse (anterior displacement) and IVRO posterior drift (posterior displacement). In 2-year follow-up, both of SSRO and IVRO showed the similar relapse distances.

Orthognathic Surgery of the Mandible

Orthognathic surgery performed in conjunction with orthodontic treatment is commonly performed to correct skeletal irregularities and realign the maxillomandibular relationship to improve occlusal function and facial esthetics. A thorough understanding of soft tissue esthetics, skeletal and occlusal relationships, and surgical techniques is required to obtain successful results. Surgical techniques have evolved greatly throughout history, as technological advances such as virtual surgical planning have become available and widely used to obtain predictable movements with minimized complications. The aim of this article is to review the orthognathic surgical procedures of the mandible, with particular attention to the indications, contraindications, preoperative assessment, surgical technique, and possible complications encountered.

Sexual dimorphism and geographical variance: their impact on the reliability of the antilingula as a landmark in human mandibular surgery

The intraoral vertical ramus osteotomy (IVRO) is an orthognathic procedure that is used to correct dentofacial abnormalities, and is performed by approaching the lateral aspect of the mandibular ramus. This approach, however, precludes visualisation of the inferior alveolar nerve (IAN) on the medial side, thereby placing it at risk of iatrogenic damage. The antilingula, a bony prominence on the lateral mandibular ramus, has been proposed as a landmark for prediction of the IAN's location during IVRO. The current study aimed to evaluate the variation in incidence and position of the antilingula, and therefore to determine its suitability as a surgical landmark during IVRO. The study included 480 dry hemimandibles from eight geographical populations from the Duckworth Collection in Cambridge. Skulls were sexed by visual analysis of dimorphic traits. Positional relations were determined through the digitisation of nine anatomical landmarks. The antilingula was identified in all specimens. No significant difference was identified in the positional relation between the antilingula and mandibular foramen between sexes, but multiple differences were identified in this relation between geographical populations. Our data showed that, irrespective of geographical variation, an osteotomy performed 8mm posterior to the antilingula would avoid the mandibular foramen in 98.8% of cases.

Two-thirds anteroposterior ramus length is the preferred osteotomy point for intraoral vertical ramus osteotomy

OBJECTIVES

This study aimed to investigate the mandibular canal of ramus and design a suitable osteotomy line for intraoral vertical ramus osteotomy (IVRO) using cone-beam computed tomography (CBCT).

MATERIALS AND METHODS

Ninety patients were classified into class I, II, and III skeletal pattern groups. When extended from the horizontal base plane (0 mm, mandibular foramen [MF]), with a 2-mm section interval, to 10 mm above and 10 mm below the MF, the following landmarks were identified: external oblique ridge (EOR), posterior border of the ramus (PBR), and posterior lateral cortex of ramus (PLC): IVRO osteotomy point.

RESULTS

In the base plane (0-mm plane), the EOR-PBR distance of class III (34.78 mm) and the IOR-PBR distance of class II (32.72 mm) were significantly higher than those of class I (32.95 mm and 30.03 mm). Compared to the EOR-PLC distance, the designed osteotomy point (two-thirds EOR-PBR length) has a 3.49-mm safe zone at the base plane and ranging from 0.89 mm (+ 10-mm plane) to 8.37 mm (- 10-mm plane).

CONCLUSIONS

The position at two-thirds EOR-PBR length (anteroposterior diameter of the ramus) can serve as a reference distance for the IVRO osteotomy position.

CLINICAL RELEVANCE

Mandibular setback operations for treating mandibular prognathism mainly include sagittal split ramus osteotomy (SSRO) and IVRO. IVRO has a markedly lower incidence of postoperative lower lip paraesthesia than SSRO. Our design presented a reference point for identification during IVRO, to prevent damage to the inferior alveolar neurovascular bundle.

Postoperative CT findings of orthognathic surgery and its complications: A guide for radiologists

Orthognathic surgery is the standard procedure to correct congenital, developmental, or acquired dentofacial deformities. The maxillomandibular relationship corrected by orthognathic surgery can improve facial esthetics, masticatory function, articulation, and breathing. The most common types of osteotomies include the combination of Le Fort I osteotomy, bilateral sagittal split mandibular ramus osteotomy, and genioplasty. High-resolution low-dose computed tomography is useful for evaluating the facial skeleton and soft tissues after surgery as well as for depicting a variety of possible complications. This article reviews the postoperative imaging findings of the most common orthognathic surgeries and their potential complications on multidetector-row computed tomography.

Anatomical Variation in the Mandibular Foramen in Non-Atrophic and Atrophic Mandibles

Objectives

Previous studies of variation in mandibular foramen characteristics with age have involved comparison in different populations, but few data, between non-atrophic and atrophic mandibles are available. The aim of this original article was to compare the position, shape and area of the mandibular foramen between non-atrophic and atrophic mandibles.

Material and Methods

Morphometric methods were used to study the mandibular foramen variation. Fifty adult dry mandibles from the laboratory of anatomy were selected. Mandibles were considered non-atrophic if the distance between the base and alveolar ridge was homogeneous and greater than 25 mm in the anterior region and 20 mm in the posterior region. Conversely, mandibles were considered atrophic if that distances were lower than those described to a minimum of 11 mm in all areas. All measurements were performed with a digital caliper. For statistical analysis, the admitted level of significance was 5%.

Results

When non-atrophic mandibles were compared to atrophic ones, the mandibular foramen shifted significantly to an anterior position (mean difference [MD]: 4.81 mm; P < 0.0001) and to an inferior position (MD: 3.04 mm; P < 0.0001) and changed from an elliptical shape to round one, with a significant decrease in its area (MD: 3.66 mm²; P < 0.05).

Conclusions

The results indicate that there are significant differences in the position, shape and area of the mandibular foramen between non-atrophic and atrophic mandibles. These data should be considered in anaesthetic techniques and surgical procedures to prevent vascular and nervous lesions.

The presence probability of mandibular lingla and antilingula

PURPOSE

The lingula and antilingula are crucial surgical landmarks for mandibular setback surgery. The purpose of study was to investigate the correlation of presence probability between lingual and antilingula.

MATERIALS AND METHODS

A total of 180 cone-beam computed tomography sides were collected from 90 patients. The probability of absence of the lingula and antilingula was recorded with respect to the gender, mandible (unilateral and bilateral), and skeletal patterns (Class I, II, III); in addition, the correlations between these variables were analysed.

RESULTS

Of the 180 sides, 9 sides showed the absence of the lingula (5%) and 34 sides showed the absence of the antilingula (18.9%). Pearson's test revealed that the presence of the lingula and antilingula differed nonsignificantly with respect to gender and skeletal patterns, respectively. The bilateral presence of the lingula was observed in 16 sides (91.1%), and that of the antilingula was observed in 122 sides (67.8%). Pearson's test verified a significant correlation between the presence of the left and right lingula (P<0.05). By contrast, gender and skeletal patterns were nonsignificantly correlated with the presence of the lingula and antilingula. The presence of the lingula was also nonsignificantly correlated with that of the antilingula.

CONCLUSION

Gender and skeletal patterns were nonsignificantly correlated with the presence of the lingula and antilingula, respectively. The presence of the lingula was also nonsignificantly correlated with that of the antilingula. Consequently, lingula and antilingula cannot serve as the absolute standards for mandibular setback surgery.

Digital cutting guide and endoscopically-assisted vertical ramus osteotomy to treat condylar osteochondroma: a long-term study

We have introduced an effective treatment for mandibular condylar osteochondroma with a digital cutting guide and endoscopically-assisted vertical ramus osteotomy (VRO). Eleven patients with unilateral condylar osteochondroma, who did not require orthognathic surgery or had less than 3mm deviation of the chin and a stable occlusion, were treated during the period April 2013-January 2017 with a digital cutting guide and endoscopically-assisted VRO. Clinical data collected included the occlusion, facial contour, and maximum mouth opening (MMO). Computed tomographic (CT) scans were taken before and after operation. Two patients also had additional shaping of the mandibular contour. The pathological diagnosis was confirmed to be osteochondroma in all cases. A mean (range) 19 (12-40) months of follow-up for all 11 cases showed stable postoperative occlusion and facial aesthetics. There were no functional disturbances, recurrence, or condylar absorption. VRO is an alternative to orthognathic surgery for patients with osteochondroma who do not have severe malocclusions. The digital cutting guide and endoscopically-assisted VRO make it possible to achieve precise resection of the tumour and maintain the occlusion with minimal invasion.