The medial surface of the mandible as an alternative source of bone grafts in orthognathic surgery

Facial Palsy after Orthognathic Surgery: Incidence, Causative Mechanism, Management, and Outcome

BACKGROUND

Facial palsy after orthognathic surgery is an uncommon but serious complication causing dissatisfaction and affecting quality of life. The occurrence could be underreported. Surgeons need to recognize this issue regarding the incidence, causative mechanism, managements, and outcome.

METHODS

A retrospective review of orthognathic surgery records between January of 1981 and May of 2022 was conducted in the authors' craniofacial center. Patients who developed facial palsy after the surgery were identified, and demographics, surgical methods, radiologic images, and photographs were collected.

RESULTS

A total of 20,953 sagittal split ramus osteotomies (SSROs) were performed in 10,478 patients. Twenty-seven patients developed facial palsy, resulting in an incidence of 0.13% per SSRO. In a comparison of SSRO technique, the Obwegeser-Dal Pont technique using osteotome for splitting had higher risk of facial palsy than the Hunsuck technique using the manual twist splitting ( P < 0.05). The severity of facial palsy was complete in 55.6% of patients and incomplete in 44.4%. All patients were treated conservatively, and 88.9% attained full recovery in a median duration of 3 months [interquartile range (IQR), 2.75 to 6 months] after surgery, whereas 11.1% attained partial recovery. Initial severity of facial palsy predicted the timing of recovery, with incomplete palsy patients having faster median recovery (3 months; IQR, 2 to 3 months) than the complete palsy patients (6 months; IQR, 4 to 6.25 months) ( P = 0.02).

CONCLUSIONS

The incidence of facial palsy after orthognathic surgery was 0.13%. Intraoperative nerve compression was the most likely causative mechanism. Conservative treatment is the mainstay of therapeutic strategy, and full functional recovery was anticipated.

CLINICAL QUESTION/LEVEL OF EVIDENCE

Risk, IV.

Three-dimensional evaluation of skeletal stability after surgery-first bimaxillary surgery for class III asymmetry in 70 consecutive patients

Background/purpose

Skeletal stability after orthognathic surgery is essential for positive treatment outcome. This study evaluated the stability of osteotomy segments after surgery-first bimaxillary surgery for class III asymmetry.

Materials and methods

Seventy adults with class III asymmetry consecutively corrected through surgery-first Le Fort I and bilateral sagittal split osteotomies were investigated. Cone-beam computed tomography before treatment (T0), 1-week after surgery (T1), and after all treatment (T2, ≥1-year after surgery) was used to assess surgical movement (T0 to T1) and skeletal stability (T1 to T2) regarding the translation and rotation of the maxillary, mandibular distal, and proximal segments.

Results

At T1, the maxillary segment had moved forward and upward, turned to the deviated side, and rotated downward (all P < 0.01). The distal segment of mandible had moved forward and upward and rotated upward (all P < 0.001). The deviated proximal segment had moved upward, tilted to the opposite side, and rotated upward (all P < 0.001). The opposite proximal segment had moved upward and tilted to the deviated side (both P < 0.01). At T2, significant relapse occurred in the mandible. The distal segment moved forward and upward and rotated upward (all P < 0.001). The deviated proximal segment moved upward, tilted to the opposite side, and rotated upward (all P < 0.001). The opposite proximal segment moved upward and tilted to the deviated side (both P < 0.01).

Conclusion

Clinically significant relapse of class III asymmetry was discovered on the mandibular distal and opposite proximal segments.

Comparison of regional soft tissue changes after bimaxillary rotational surgery between class III deformity with overbite and open bite: A 3D imaging analysis

BACKGROUND

This prospective study aimed to compare regional soft tissue changes between patients with class III overbite and open bite deformities treated with bimaxillary surgery involving clockwise and counter-clockwise mandibular setback, respectively.

MATERIAL AND METHODS

Class III deformity adults receiving Le Fort I and bilateral sagittal split osteotomies were grouped according to the incisal occlusion: overbite (n = 30) and open bite (n = 30). Combined cone-beam CT scans and 3D facial photographs preoperative and at least 1-year postoperative were taken to assess the soft tissue changes.

RESULTS

Postoperative changes for the overbite and open bite groups included anterior repositioning of nose (-0.8 ± 1.2 mm and -1.1 ± 1.1 mm, respectively) and cheek (-1.9 ± 1.3 mm and -1.7 ± 2.6 mm, respectively), posterior repositioning of chin (5.2 ± 4.0 mm and 4.9 ± 3.2 mm, respectively), and medial (-1.7 ± 2.0 mm and -1.9 ± 2.1 mm, respectively) and posterior (2.7 ± 1.4 mm and 2.8 ± 2.3 mm, respectively) repositioning of bilateral angles. Posterior (1.2 ± 2.0 mm and 5.1 ± 3.3 mm) and inferior (-1.4 ± 2.2 mm and -2.4 ± 2.7 mm) repositioning of upper lip and lower lip occurred in overbite group. Inferior (-2.3 ± 2.4 mm) and superior (3.7 ± 3.4 mm) repositioning of chin occurred in the overbite and open bite groups, respectively.

CONCLUSIONS

Treatment of class III overbite and open bite deformities with bimaxillary rotational surgery resulted in comparable regional soft tissue changes, except for upper lip, lower lip and chin.

Accuracy of Mandible-First versus Maxilla-First Approach and of Thick versus Thin Splints for Skeletal Position after Two-Jaw Orthognathic Surgery

BACKGROUND

The aim of this study was to investigate the accuracy of bimaxillary orthognathic surgery regarding different sequencing (maxilla-first or mandible-first surgery) and different thicknesses of intermediate splints.

METHODS

This retrospective cohort study evaluated the accuracy of postoperative outcome in accordance with virtual planning in 57 patients requiring bimaxillary osteotomies with different operation sequence: maxilla-first (n = 31) or mandible-first (n = 26) surgery. The effect of different splint thicknesses (i.e., thick, n = 22; and thin, n = 35) was also evaluated. The 1-week postoperative cone-beam computed tomographic craniofacial images were superimposed onto preoperative simulated images to measure the discrepancy of the three-dimensional cephalometric landmarks.

RESULTS

Neither sequencing approach differed in overall accuracy (1-week postoperative to preoperative simulated image discrepancy): maxilla-first, 1.69 ± 0.53 mm; versus mandible-first, 1.44 ± 0.52 mm. In detailed comparison, mandible-first surgery resulted in more accuracy in the vertical dimension. Thick intermediate splints provided better control (less error) of upper central incisors in the sagittal position (thick splint, 1.38 ± 1.17 mm; thin splint, 2.13 ± 1.38 mm). However, overall accuracy was not affected by splint thickness. Conditions affecting sequencing predilection included skeletal class III with vertical excess, maxillary down-grafting, counterclockwise rotation of the maxillomandibular complex, and simulated mandibular opening for splint fabrication clearance.

CONCLUSIONS

Despite both means of sequencing being performed similarly, mandible-first surgery was more precise in the vertical dimension. Thick intermediate splints seemed to yield better control of central incisors in the sagittal position. However, under appropriate selection of intermediate splints to maintain interim condylar position, splint thickness has no effect on overall accuracy.

CLINICAL QUESTION/LEVEL OF EVIDENCE

Therapeutic, III.

Type of maxillary segment mobilization affects three-dimensional nasal morphology

BACKGROUND

Surgical mobilization of the maxillary segment affects nasal morphology. This study assessed the impact of the type of maxillary mobilization on the three-dimensional (3D) nasal morphometry.

METHODS

Pre- and postsurgery cone beam computed tomography-derived facial image datasets of consecutive patients who underwent two-jaw orthognathic surgery were reviewed. Using preoperative 3D facial models as the positional reference of the skeletal framework, 12-month postoperative 3D facial models were classified into four types of maxillary mobilizations (advancement [n = 83], setback [n = 24], intrusion [n = 55], and extrusion [n = 52]) and four types of final maxillary positions (anterosuperior [n = 44], anteroinferior [n = 39], posterosuperior [n = 11], and posteroinferior [n = 13]). Six 3D soft tissue nasal morphometric parameters were measured, with excellent intra- and interexaminer reliability scores (ICC>0.897) for all the measurements. The 3D nasal change for each nasal parameter was computed as the difference between postoperative and preoperative measurement values.

RESULTS

The intrusion maxillary mobilization resulted in a significantly (all p<0.05) larger 3D nasal change in terms of alar width, alar base width, and nostril angle parameters, and a smaller change in terms of the nasal tip height parameter than the extrusion maxillary mobilization; however, no significant (all p>0.05) difference was observed between advancement and setback maxillary mobilizations. The anterosuperior and posterosuperior maxillary positions had a significantly (all p<0.05) larger 3D nasal change in terms of the alar base width and nostril angle than the anteroinferior and posteroinferior maxillary positions.

CONCLUSION

The type of maxillary mobilization affects the 3D nasal morphometry.

Investigation of a Modified Novel Technique in Bilateral Sagittal Splitting Osteotomy Fixation: Finite Element Analysis and In Vitro Biomechanical Test

Purpose

To evaluate the biomechanical properties of the modified novel 2-hole monocortical plate fixation (2HMCPf) and traditional 4-hole monocortical plate fixation (4HMCPf) techniques in bilateral sagittal splitting osteotomy (BSSO) synthesis using a finite element analysis (FEA) and an in vitro biomechanical test with the application of a shearing loading force on a sawbone mandible model.

Materials and Methods

A three-dimensional mandible models were generated using the geometry obtained from the computerized tomography image of a sawbone mandible. Plates and screws were generated and combined with the mandible in a CAD environment. The 2HMCPf and traditional 4HMCPf techniques for BSSO osteosynthesis were then analyzed under the occlusal load using the FEA. An in vitro biomechanical test was executed to verify the result of FEA. The force on fixation failure and pattern of failure were recorded.

Results

The results revealed that the von Mises Stress on the mandible cortical bone (75.98 MPa) and the screw/plate (457.19 MPa) of the 2HMCPf group was lower than that of the 4HMCPf group (987.68 MPa, 1781.59 MPa). The stress concentrated on the central region of the 4HMCPf group and the distal set of the 2HMCPf group. In vitro study using the sawbone mandible model showed mechanical failure at the region of the proximal segment near the osteotomy site with the 4HMCPf group (average 32.198 N) but no failure on the fixation sites with the 2HMCPf group. Instead, the mandible sawbone fractured on the condyle neck region (average 44.953 N).

Conclusion

From the biomechanical perspective, we proved that the 2HMCPf method was able to withstand a higher shearing loading force than the 4HMCPf fixation method in BSSO osteosynthesis.

A new 3D analysis on displacement of proximal segment after bilateral sagittal split osteotomy for class III asymmetry

OBJECTIVES

We aimed to quantify the displacement of the proximal segment after bilateral sagittal split osteotomy in patients with class III asymmetry and evaluate if the displacement was related to the movement of the distal segment.

MATERIAL AND METHODS

Forty adults with class III asymmetry corrected by bimaxillary surgery were studied. Cone-beam computed tomography taken before and 1 week after surgery was used to measure the displacement of proximal segments and movement of the distal segment in terms of translation and rotation. The relationship between the displacemnt of the proximal segment and the movement of the distal segment was evaluated.

RESULTS

After surgery, the deviated proximal segment was displaced forward and to the deviated side, rotated downward, tilted, and turned to the opposite side. The opposite proximal segment was displaced forward and rotated downward. The roll rotation of the proximal segment was correlated with the left/right movement and roll rotation of the distal segment.

CONCLUSION

Early after orthognathic correction for class III asymmetry, the deviated proximal segment was displaced in a direction favorable for correction of asymmetry. The roll rotation of the proximal segment was affected by the transverse movement and roll rotation of the distal segment.

CLINICAL RELEVANCE

Knowledge of the ability and limitation of the proximal segment rotation improves the virtual simulation.

Outcomes of conventional versus virtual surgical planning of orthognathic surgery using surgery-first approach for class III asymmetry

OBJECTIVES

To determine if patient outcome variables differ between conventional and virtual surgical planning of orthognathic surgery for class III asymmetry.

MATERIAL AND METHODS

This retrospective case-control study examined 95 patients with class III asymmetry who had been consecutively treated with at least a Le Fort I osteotomy and a bilateral sagittal split osteotomy with a surgery-first approach. Two groups were examined: 51 patients treated with conventional surgical planning and 44 with virtual surgical planning. After treatment, quantitative assessment was determined with measurements of midline symmetry, contour symmetry, and overall facial symmetry using standardized frontal photographs. Subject assessments were analyzed with questionnaires regarding self-perception of overall appearance, satisfaction with appearance, and quality of life.

RESULTS

Conventional and virtual surgical planning resulted in significant improvements in outcomes for all patients. However, facial midline and overall facial symmetry were significantly greater for the virtual compared with the conventional group. There were no significant differences in subjective measures of appearance, satisfaction with appearance, and quality of life for patients treated with conventional or virtual surgical planning; measures were high for both groups.

CONCLUSIONS

Conventional and virtual surgical planning of surgery-first bimaxillary orthognathic surgery resulted in quantitative and qualitative improvements in facial symmetry. Although patient satisfaction was similar for both approaches, virtual surgical planning was superior to conventional surgical planning for the improvement of midline and overall asymmetry.

CLINICAL RELEVANCE

Improvements with virtual surgical planning in facial midline, facial contour, and overall facial symmetry are as good as or better than conventional surgical planning.

The Medial Subcoronoid Process Region as a Novel Source of Bone Grafts in Orthognathic Surgery and Genioplasty

BACKGROUND

Since 2012, the authors have adopted the medial subcoronoid process bone interpositional grafting in OGS and genioplasty procedures. The purpose of this study was to present the technical details and clinical outcomes of this alternative bone interpositional grafting for LeFort I and chin osteotomies.

METHODS

Consecutive patients (n = 50) who underwent single-splint bimaxillary OGS with or without genioplasty and received medial subcoronoid bone interpositional grafting were included. Standardized facial and intraoral photographs at early and late postoperative periods (12.2 ± 3.3 and 44.8 ± 8.4 months postsurgery, respectively) were blindly rated to assess facial symmetry, chin, and occlusion status based on qualitative rating scales. Complication and reoperation rates were also reviewed.

RESULTS

The medial subcoronoid bone interpositional grafts were adopted to stabilize different LeFort I maxillary movement types or lengthening/advancing genioplasty (36 and 14 patients, respectively). Overall, the early facial symmetry, chin, and occlusion status were maintained at late evolutions. None of the patients had donor-site or bone graft-related complications (i.e., bad split, undesired mandible fracture, infection, fibrous union, nonunion, and/or permanent neurosensory deficit) or revisionary surgery during follow-up.

CONCLUSION

The medial subcoronoid process bone grafting was a feasible alternative for bone interpositional defects of LeFort I and chin osteotomies with no significant morbidity and avoiding secondary donor sites.

Surgical-orthodontic treatment for class II asymmetry: outcome and influencing factors

The study aimed to evaluate the treatment outcome of bimaxillary surgery for class II asymmetry and find the influencing factors for residual asymmetry. Cone-beam computed tomographic images of 30 adults who had bimaxillary surgery were acquired, and midline and contour landmarks of soft tissue and teeth were identified to assess treatment changes and outcome of facial asymmetry. The postoperative positional asymmetry of each osteotomy segment was also measured. After surgery, the facial midline asymmetry of the mandible, chin, and lower incisors improved significantly (all p < 0.01). However, the residual chin deviation remained as high as 2.64 ± 1.80 mm, and the influencing factors were residual shift asymmetry of the mandible (p < 0.001), chin (p < 0.001), and ramus (p = 0.001). The facial contour asymmetry was not significantly improved after surgery, and the influencing factors were the initial contour asymmetry (p < 0.001), and the residual ramus roll (p < 0.001) or yaw (p < 0.01) asymmetry. The results showed that bimaxillary surgery significantly improved midline but not contour symmetry. The postoperative midline and contour asymmetry was mainly affected by the residual shift and rotational jaw asymmetry respectively.

Treatment outcome of bimaxillary surgery for asymmetric skeletal class II deformity

OBJECTIVES

Facial asymmetry is one of the main concerns in patients with a dentofacial deformity. The aims of the study were to (1) evaluate the changes in facial asymmetry after bimaxillary surgery for asymmetric skeletal class II deformity and (2) compare preoperative and postoperative facial asymmetry of class II patients with normal controls.

MATERIALS AND METHODS

The facial asymmetry was assessed for 30 adults (21 women and 9 men, mean age: 29.3 years) who consecutively underwent bimaxillary surgery for asymmetric skeletal class II deformity using cone-beam computed tomography before and at least 6 months after surgery. Thirty soft tissue and two dental landmarks were identified on each three-dimensional facial image, and the asymmetry index of each landmark was calculated. Results were compared with those of 30 normal control subjects (21 women and 9 men, mean age: 26.2 years) with skeletal class I structure.

RESULTS

Six months after surgery, the asymmetric index of the lower face and total face decreased significantly (17.8 ± 29.4 and 16.6 ± 29.5 mm, respectively, both p < 0.01), whereas the asymmetric index of the middle face increased significantly (1.2 ± 2.2 mm, p < 0.01). Postoperatively, 53% of the class II patients had residual chin asymmetry. The postoperative total face asymmetric index was positively correlated with the preoperative asymmetric index (r = 0.37, p < 0.05).

CONCLUSIONS

Bimaxillary surgery for patients with asymmetric class II deformity resulted in a significant improvement in lower face asymmetry. However, approximately 50% of the patients still had residual chin asymmetry. The total face postoperative asymmetry was moderately related to the initial severity of asymmetry.

CLINICAL RELEVANCE

These findings could help clinicians better understand orthognathic outcomes on different facial regions for patients with asymmetric class II deformity.

Mandibular Contouring During Orthognathic Surgery Using the Modified Hunsuck Technique

Square face or prominent mandibular angle is a major concern in Asian women. In class III patients, mandibular setback may lead to a wider lower face that is not preferred in Asian culture. In order to achieve better aesthetic outcomes, simultaneous mandibular contouring to reduce the width of the lower face is required for some patients. This article details the authors' procedures modified from Hunsuck techniques of sagittal split osteotomy. This modified Hunsuck technique provides an alternative option to obtain a desirable mandibular outline. The long-term stability is also comparable to traditional methods.

Concomitant Third Molar Removal During Sagittal Split Osteotomy of the Mandible

It is described in textbook about management of third molar in orthognathic surgery that "ideally, the third molars should be removed 9 to 12 months before sagittal split osteotomy (SSO)." At the Chang Gung Craniofacial Center, the authors always remove mandibular third molars during SSO, because: removal of third molars at the same time of SSO could reduce psychological stress on patients by saving 1 surgical procedure under local anesthesia, better exposure of impacted third molars could be facilitated by sagittal split of buccal cortical plate, rigid fixation could be performed without difficulty by our fixation method using plates and screws crossover anterior oblique line. Strong force during the elevation of third molars, however, may result in the fracture of distal segment of SSO, where the buccal cortical plate is relatively thin because of the presence of third molar. Therefore, more care needs to be taken in the surgical technique, which is different from ordinary tooth extraction. In this paper, the details of surgical procedure of third molar removal during SSO were reported.

[Le Fort I osteotomies combined with post-operative bone grafts]

INTRODUCTION

We present and assess a surgical technique for maxillary auto-bone grafting concomitantly with Le Fort I osteotomy. The graft has 2 main objectives: to fill in the space between the 2 advanced segments of the maxilla to help bone consolidation, and to increase the volume of the malar, para-nasal spaces to improve post-operative esthetic results.

TECHNICAL NOTE

Bone fragments, removed during the Le Fort I osteotomy, are stored and wrapped in a Surgicel(®) sheet, then grafted in the space left by the osteotomy, or on the anterior maxilla in the para-nasal area or on the malar bone. One hundred and twenty-three patient records, operated from 2007 to 2012, were collected to assess the post-operative course retrospectively. The post-operative course was uneventful in 93.5% of cases. About 8.4% of patients (7 cases) presented with a persistent post-operative maxillary edema. 1 patient (1.2%) presented with a sinus infection without any determined etiology. The grafts were all osteointegrated at the end of follow-up.

DISCUSSION

The technique is simple and quickly performed; it improves bone healing and cosmetic results, without increasing morbidity or surgical time. It is a good alternative to bone grafts from a secondary sample site. It can be applied to all Le Fort I osteotomies.

Quantitative evaluation of cortical bone thickness in mandibular prognathic patients with neurosensory disturbance after bilateral sagittal split osteotomy

PURPOSE

The buccal cortical thickness (BCT) between the mandibular canal and the corresponding external cortical surface was compared in patients with and without neurosensory disturbance (NSD) after they underwent a bilateral sagittal split osteotomy (BSSO) to correct mandibular prognathism.

PATIENTS AND METHODS

This prospective cohort study was conducted in 146 patients (95 women, 65.1%; 51 men, 34.9%) 18 to 39 years old who underwent bimaxillary surgery (ie, Le Fort I osteotomy and BSSO) to correct mandibular prognathism. NSD was identified using a light touch test with a Semmes-Weinstein monofilament and a pricking pain test with a sharp dental explorer 1 week after surgery. Preoperative cone-beam computed tomographic (CBCT) imaging was used to visualize the bone contacts or fusion of the mandibular canal to the buccal cortical bone and to decrease injury to the mandibular nerve during surgical dissection. Preoperative CBCT imaging also was used to assess the BCT every 2 mm from the mandibular foramen to the furcation of the mandibular first molar in the NSD group and the sensory normal (N) group.

RESULTS

The incidence of NSD was 32.5% at 1 week after surgery. There was no statistically significant difference between men and women, the side affected, or genioplasty at the time of undergoing BSSO. Of the total sample group, decreased BCT was identified throughout the observed length of the mandibular canal in the NSD group compared with the N group. Statistically significant decreased BCTs were 16 to 20 mm and 24 mm in the total sample, 6 to 8 mm in the female group, and 16 to 18 mm in the male group.

CONCLUSION

Compared with the N group, BCTs in the NSD group were always decreased, especially those located at 16 to 20 mm and 24 mm in the total sample, 6 to 8 mm in the female group, and 16 to 18 mm in the male group.

Bimaxillary protrusion: an overview of the surgical-orthodontic treatment

Bimaxillary protrusion is a commonly seen deformity in Asian populations. This condition is characterized by protrusive and proclined upper and lower incisors and an increased procumbency of the lips. It is usually combined with lip incompetence, gummy smile, mentalis strain, and anterior open bite. Facial aesthetics is the primary concern of these patients. Successful treatment depends on a thorough evaluation and understanding of this dentofacial deformity. Typical orthodontic treatment includes retraction and retroclination of maxillary and mandibular incisors after extraction of the four first premolars. Orthognathic surgery is required to correct significant skeletal problems. Anterior subapical osteotomies and extraction of premolars can correct sagittal excess of the jaw bones and relieve dental crowding. Segmental maxillary osteotomies are performed to treat patients with an associated exaggerated curve of Spee and vertical maxillary excess. Differential intrusion of anterior and posterior maxilla/maxillary segments with clockwise rotation of the occlusal plane is a useful technique for treatment of anterior open bite and creation of a consonant smile arc. Le Fort I osteotomy with setback sometimes provides an alternative to segmental maxillary osteotomies. Meticulous planning and execution of osteotomies in accordance with surgical planning are essential for aesthetic and functional outcome.

Surgical Approach to the Patient with Bimaxillary Protrusion

The patient who has bimaxillary protrusion often is treated using a combination of orthodontics and orthognathic surgery, and the general approach is dental extraction with retraction of the incisors. In certain cases, maxillary excess may be corrected solely with LeFort I osteotomy and setback and without dental extraction or anterior segmental osteotomies. This article discusses (1) treatment evaluation and planning and (2) the specific surgical techniques, primarily anterior segmental osteotomies and the technical details for setback of the LeFort I osteotomized segment (more than 5 mm), as they relate to the surgical approach of the patient who has bimaxillary protrusion.