Medial pterygoid muscle and stylomandibular ligament: the effects on postoperative stability

Skeletal stability of inter-molar mandibular distraction osteogenesis in growing patients

INTRODUCTION

The aim of this retrospective study was to firstly assess the stability of surgical advancement using inter-molar mandibular distraction osteogenesis (IMDO) and secondly to assess the impact of the surgical intervention on subsequent mandibular growth in patients with residual growth.

METHODS

The sample consisted of 17 (13F and 4M) consecutively treated patients who underwent IMDO and orthodontic treatment. Cephalometric analysis was performed at three time points: T0 prior to distraction; T1 post-distraction immediately prior to surgical removal of the distractors; and T2 following completion of orthodontic treatment when the final lateral cephalogram was taken (0.86-4.37 years after T1). Statistical comparison of lower facial height, mandibular length, growth, condylar position and anterior mandibular rotation was performed.

RESULTS

No association was found between changes in any of the cephalometric measurements and the length of the follow-up interval. The anterior mandibular segment underwent clockwise rotation during distraction and recovered to near its pre-distraction angulation during remodelling. An increase in the lower facial height of 1.88 ± 2.81mm also occurred during distraction (T0-T1) and was maintained during the follow-up period (T1-T2). Post-distraction (T1-T2) growth of lower facial height (p value 0.872) and mandibular length (p value 0.251) showed no association when compared to an untreated control group and an overall reduction in growth was reported.

CONCLUSIONS

IMDO was highly stable within a follow-up period of 2.3 ± 0.9 years; however, growth appears to have been inhibited.

Mandibular stability and condylar changes following orthognathic surgery in mandibular hypoplasia patients associated with preoperative condylar resorption

OBJECTIVES

To evaluate postoperative mandibular stability and condylar changes in patients with mandibular hypoplasia and preoperative condylar resorption (CR) undergoing orthognathic surgery.

MATERIALS AND METHODS

Fifty-four patients were included in this retrospective study. Computed tomography (CT) scans were acquired preoperatively (T0), 2-7 days immediate postoperatively (T1), and at least 1 year postoperatively (T2). Three-dimensional (3D) cephalometric analysis and measurements of condylar angle, volume, and position (joint spaces) were performed. A 2-mm mandibular relapse was deemed clinically acceptable. We also analyzed the correlations between relapse and postoperative CR and susceptible factors using a multivariate logistic regression model.

RESULTS

The results showed one year after the surgery, the average mandibular relapse was 1.0 mm (p < 0.05), and the average reduction of condylar volume was 152.4 mm³ (12.7%). Condyle-fossa relationships were improved immediately after the surgery, with a tendency of returning to their original state in the follow-up (p < 0.05). Anteroposterior advancement at point B (B-CP advancement) at T1 and superior joint space (SJS) at T0 were significantly correlated with mandibular relapse, and postoperative CR was mainly associated with vertical increasement at point B (B-AP increasement) at T1. The optimal cut-off values were as follows: 1.6 mm for SJS, 4.2 mm for B-CP advancement, and 1.8 mm for B-AP increasement. Concomitant advancement Genioplasty showed no significant correlation with relapse and postoperative CR.

CONCLUSIONS

While patients with mandibular hypoplasia and preoperative CR were vulnerable to further condylar resorption after mandibular advancement, the treatment outcomes were generally clinically acceptable. Postoperative relapse was associated with a larger than 4.2 mm of mandibular advancement measured at B-CP and a larger than 1.6 mm of superior joint space measured at SJS, and postoperative CR was associated with a larger than 1.8 mm of mandibular vertical increasement measured at B-AP.

CLINICAL RELEVANCE

The findings of this study suggested that the mandibular advancement might be limited to 5 mm for patients with preoperative CR. A concomitant advancement genioplasty might also be considered to achieve a better facial profile in these patients.

Skeletal and upper airway stability following modified maxillomandibular advancement for treatment of obstructive sleep apnea in skeletal class I or II deformity

OBJECTIVES

Maxillomandibular advancement (MMA) is an effective short-term treatment for obstructive sleep apnea (OSA). This study aimed to evaluate the long-term stability of the facial skeleton, upper airway, and its surrounding structures, as well as improvement in OSA following MMA.

MATERIALS AND METHODS

Thirty-one adults with moderate-to-severe OSA underwent surgery-first modified MMA as primary surgery. Polysomnography and cone-beam computed tomography were obtained pre-surgery, early post-surgery, and at follow-up (i.e., ≥ 2 years post-surgery). Image analysis software assessed the facial skeleton, upper airway, and its surrounding structures.

RESULTS

Early post-surgery, apnea-hypopnea index (AHI) had decreased significantly (p < 0.001) and the minimum oxygen saturation (MSAT) increased (p = 0.001), indicating significant improvement in OSA. At follow-up, the AHI and MSAT remained stable. However, the anterior maxilla, soft palate, and tongue moved backward while the hyoid moved downward. There was also a significant decrease in the minimal cross-sectional area of the oropharynx. The reduction in AHI was significantly related to the anterior movement of the anterior maxilla and tongue, inferior movement of the posterior maxilla, and superior movement of the soft palate tip.

CONCLUSIONS

The improvement of OSA after modified MMA remained stable for at least 2 years following treatment, despite the relapse of the facial skeleton, upper airway, and its surrounding structures. The reduction of AHI was not related to changes in the caliber of the upper airway but to the movement of the maxilla, soft palate, and tongue. Clinical relevance Modified MMA is clinically effective for long-term treatment of patients with moderate-to-severe OSA.

Three-dimensional surgical management of a patient with Pruzansky I hemifacial microsomia and severe facial asymmetry: A 4-year follow-up

Treatment of hemifacial microsomia is challenging and often requires multiple interventions to restore function and facial esthetics. In this article, the combined orthodontic-surgical treatment of a young patient exhibiting Pruzansky I hemifacial microsomia is reported. The patient was aged 15 years, but his bone age was determined to be 18 years. His facial asymmetry was severe, with the nose and a retrusive chin deviated to the left side and a canted smile. The presurgical phase was aimed at centering the mandibular midline to the center of the chin through the distal movement of the mandibular left buccal dentition. The surgery was planned with 3-dimensional computer-aided surgical simulation and included a LeFort I and unilateral sagittal split osteotomies combined with a genioplasty. This report illustrates the therapeutic stages and a 4-year follow-up of a unique and complex orthognathic surgical approach, chosen among other alternatives and leading to improved function and appearance and stable results.

The role of muscular traction in the occurrence of skeletal relapse after advancement bilateral sagittal split osteotomy (BSSO): A systematic review

The aim of this systematic review was (i) to determine the role of muscular traction in the occurrence of skeletal relapse after advancement BSSO and (ii) to investigate the effect of advancement BSSO on the perimandibular muscles. This systematic review reports in accordance with the recommendations proposed by the Preferred Reporting Items for Systematic Reviews and Meta‐Analyses (PRISMA) statement. Electronic database searches were performed in the databases MEDLINE, Embase and Cochrane Library. Inclusion criteria were as follows: assessment of relapse after advancement BSSO; assessment of morphological and functional change of the muscles after advancement BSSO; and clinical studies on human subjects. Exclusion criteria were as follows: surgery other than advancement BSSO; studies in which muscle activity/traction was not investigated; and case reports with a sample of five cases or fewer, review articles, meta‐analyses, letters, congress abstracts or commentaries. Of the initial 1006 unique articles, 11 studies were finally included. In four studies, an intervention involving the musculature was performed with subsequent assessment of skeletal relapse. The changes in the morphological and functional properties of the muscles after BSSO were studied in seven studies. The findings of this review demonstrate that the perimandibular musculature plays a role in skeletal relapse after advancement BSSO and may serve as a target for preventive strategies to reduce this complication. However, further research is necessary to (i) develop a better understanding of the role of each muscle group, (ii) to develop new therapeutic strategies and (iii) to define criteria that allow identification of patients at risk.

Independent risk factors for long-term skeletal relapse after mandibular advancement with bilateral sagittal split osteotomy

The purpose of this retrospective cohort study was to identify the independent risk factors for long-term skeletal relapse following mandibular advancement with bilateral sagittal split osteotomy. Univariate and multivariate linear regression analyses were performed including nine common risk factors for relapse as independent variables and horizontal/vertical long-term (≥2 years) skeletal relapse as dependent variables. Ninety-six patients were analyzed; 66 were female (68.8%) and the average age of the patients was 29.7±10.5 years. Over an average follow-up of 3.8±1.8 years after an initial mandibular advancement of 8.8±2.4 mm, long-term skeletal relapse of 1.6±1.0 mm horizontal and 0.9±0.7 mm vertical was found. Multivariate analysis identified age, preoperative mandibular plane angle (MPA), bimaxillary surgery, counterclockwise mandibular rotation, and the magnitude of mandibular advancement to be significantly associated with horizontal long-term skeletal relapse. Preoperative MPA, counterclockwise mandibular rotation, and the magnitude of mandibular advancement were significantly associated with vertical long-term skeletal relapse. Thus preoperative MPA, the magnitude of mandibular advancement, and counterclockwise mandibular rotation of the mandible were found to be independent risk factors for both horizontal and vertical long-term skeletal relapse. Although long-term skeletal relapse cannot be avoided entirely, understanding the independent risk factors and their contributions will optimize treatment planning and long-term stability.

The outcome of skeletofacial reconstruction with mandibular rotation for management of asymmetric skeletal class III deformity: A three-dimensional computer-assisted investigation

The mandibular proximal ramus segments should be moved and rotated during orthognathic surgery-based skeletofacial reconstruction for the correction of challenging patients with facial asymmetry and malocclusion, but quantitative data regarding this rotation were not sufficient to date. This 3D computer-assisted study measured the proximal ramus segment rotation after 3D simulation-guided two-jaw surgery in patients with facial asymmetric deformity and class III malocclusion (n = 31). Using 3D mandible models and a reliable proximal ramus segment-related plane, angular changes in pitch, roll and yaw directions were measured before and one month after surgery. Significant rotational changes (p < 0.01) were observed in the left and right sides and overall proximal ramus segments after surgery, with absolute differences of 4.1 ± 3.0 (range −7.8 to 6.9), 2.8 ± 2.3 (−8.8 to 5.0), and 2.7 ± 2.4 (−6.6 to 9.9) degrees in pitch, roll, and yaw rotations, respectively. Numbness and mouth opening limiting occurred within the first 6 months after surgery but the patients had an unremarkable long-term postoperative course, with no revisionary surgery required. This study contributes to the multidisciplinary-related literature by revealing that proximal ramus segment rotation and rigid fixation with no postoperative intermaxillary immobilization was practicable in skeletofacial surgery for the successful treatment of asymmetric deformity and class III malocclusion.

Accuracy between virtual surgical planning and actual outcomes in orthognathic surgery by iterative closest point algorithm and color maps: A retrospective cohort study

BACKGROUND

To evaluate the accuracy between actual outcomes and virtual surgical planning (VSP) in orthognathic surgery regarding the use of three-dimensional (3D) surface models for registration using iterative closest point (ICP) algorithm and generated color maps.

MATERIAL AND METHODS

Construction of planning and postoperative 3D models in STL files format (M0 and M1, respectively) from CBCT of 25 subjects who had been submitted to bimaxillary orthognathic surgery was performed. M0 and M1 were sent to Geomagic software in semi-automatic alignment surface mesh order of M0 and M1 for registration using ICP algorithm to calculate mean deviation (MD, MD+, MD-, SD) and root mean square (RMS - 3D Error). Color maps were generated to assess qualitative congruence between M0 and M1. From deviation analysis, 3D Error was defined as accuracy measurement. To assess the reproducibility, the workflow was performed by two evaluators multiple times. t-tests were used to assess whether all means of MD, MD+, MD-, SD and 3D Error values would be ≤ - 2 mm and ≥ 2 mm.

RESULTS

High intra and inter evaluators correlation were found, supporting the reproducibility of the workflow. t-tests proved that all MDs and 3D Error values were > - 2 mm and < 2 mm.

CONCLUSIONS

3D error mean was within the standards of clinical success lower than 2 mm. ICP algorithm provided a reproducible method of alignment between 3D models and generated color maps to evaluate 3D congruence but did not answer all methodological parameters regarding the assessment of accuracy in orthognathic surgery.

Correlation between intraoperative proximal segment rotation and post-sagittal split ramus osteotomy relapse: a three-dimensional cone beam computed tomography study

This study evaluated the effects of proximal segment rotation and the extent of mandibular setback on post-sagittal split ramus osteotomy (SSRO) relapse using three-dimensional (3D) analysis. Thirty-one patients diagnosed with a skeletal class III malocclusion who underwent SSRO alone were enrolled in this study. The movements of the mandibular condyles were assessed using cone beam computed tomography (CBCT) and a 3D imaging program at ≤1 month before the operation (T0), 1 week after the operation (T1), and 6 months (T2) and 1year (T3) postoperative. Yaw and roll were increased at T1 as compared to T0. However, the proximal segments reverted to their original positions between T2 and T3. There was a positive correlation between the extent of the posterior movement of the mandible and relapse at 6 months and 1year postoperative. Although the proximal bone segments showed displacement in three dimensions at T1, they reverted to their original positions over time. In addition, although there was a positive correlation between the extent of the posterior movement of the mandible and the occurrence of post-surgical relapse at 6 months and 1year post-surgery, the rotation of the proximal bone segment during surgery had no relationship with postoperative relapse.

Complications after orthognathic surgery: our experience on 423 cases

INTRODUCTION

Orthognathic surgery is widely used to correct dentofacial discrepancies. However, this procedure presents numerous possible complications. The aim of our study is to review intraoperative and postoperative complications related to orthognathic surgery based upon a 10-year period in the Maxillofacial Surgery Department of Federico II University of Naples.

MATERIALS AND METHODS

Medical records of 423 patients who undergone orthognathic surgery in a 10-year period were retrospectively analyzed and complications was noted. Statistical analysis was conduced in order to understand if the type of surgical procedure influenced complications rate.

RESULTS

One hundred eighty-five complications in 143 (33.8%) of the 423 treated patients were reported. Complications detected were nerve injury (49 cases, 11.9%), infections (10 cases, 2.4%), complications related to fixation plates or screws (30 cases, 7.1%), bad split osteotomy (8 cases, 1.9%), secondary temporo-mandibular joint disorders (36 cases, 8.5%), dental injuries (21 cases, 5%), condilar resorption (2 cases, 0.5%), and necessity of a second-time surgery (24 cases, 5.7%).

CONCLUSIONS

Serious complications seem to be quite rare in orthognathic surgery. Some of the surgical complications found are related to the surgeon experience and not strictly to the risks of the operation itself. Understanding potential complications allows the surgeon to guarantee safe care through early intervention and correctly inform the patient in the preoperative colloquy.

Minimizing Relapse in Mandibular Asymmetry Correction by BSSRO with Intentional Osteotomy of Distal Segment: A Prospective Study

INTRODUCTION

Surgical correction of the patients with mandibular asymmetry by bilateral sagittal split ramus osteotomy (BSSRO) creats remarkable results in the immediate post operative period, but it carries a high risk of relapse by powerful muscle forces and the osteotomized segments. To minimize this risk, literatures highlight the procedure of an intentional osteotomy and stripping of muscles. A prospective study was conducted in Government Dental College, Kottayam, Kerala, to assess the effect of intentional osteotomy of posterior part of distal segment and stripping of medial pterygoid muscle on the proximal segment on affected side in mandibular asymmetry patients treated with BSSRO.

MATERIALS AND METHODS

20 patients above 18 years with mandibular asymmetry underwent surgical correction by BSSRO setback and rotation. Clinical evaluation and postero anterior cephalogram (PA Ceph) were used to assess relapse. PA cephalogram taken post operatively at 2 weeks, 6 months and 1year were compared using cephalometric parameters by Grummons analysis to assess relapse. Paired t test and Chi-square test was used to analyse quantitative and qualitative parameters respectively with statistical significance of p < 0.05.

RESULTS

Barring Methodological errors which is inevitable, the amount of relapse was not statistically significant with respect to dental midline, chin midline and frontal photograph.

CONCLUSION

Intentional osteotomy of posterior part of distal segment and stripping of medial pterygoid muscle on the affected side can prevent relapse in patients who underwent surgical correction of mandibular asymmetry by BSSRO set back and rotation.

[Relapse and alteration of results in orthognathic surgery]

Orthognathic surgery is a surgical technique that provides normalization of the face and occlusion. Some malocclusions are particularly unstable, such as maxillary transversal deficits, and anterior open bite. Many factors are implicated in the stability of surgical results. Indeed, facial balance largely depends on functions that could be the cause of unstable results, despite a good anatomical correction. Breathing, swallowing, chewing disorders and more largely alteration of the functional matrix may be sources of instability. These dysfunctions are the first cause of relapse. Others constitutional factors can also be involved in relapse. Understanding oro-facial functions and rules determining cranial and maxillo-facial balance is mandatory for the surgeon to ensure a long-term stability of procedures.