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| ORIGINAL RESEARCH |
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| Year : 2022 | Volume
: 14
| Issue : 6 | Page : 618-623 |
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Neurosensory deficit of inferior alveolar nerve after bilateral sagittal split osteotomy, advancement versus setback: An observational study
Suresh Vyloppilli1, Annamalai Thangavelu1, Sankar Vinod Vichattu2, Nithin Kumar3, Fahad Ahmad4, Paranthaman Srinivasan1
1 Department of Oral and Maxillofacial Surgery, Rajah Muthiah Dental College, Annamalai University, Chidambaram, Tamil Nadu, India
2 Department of Oral and Maxillofacial Surgery, Mar Baselios Dental College & Hospitals, Kothamangalam, Kerala, India
3 Akfa Dental School, Akfa University, Tashkent, Uzbekistan
4 Department of Oral & Maxillofacial Surgery, Jahra Specialty Dental Center, Al Jahra, Kuwait
| Date of Submission | 27-Jun-2022 |
| Date of Acceptance | 17-Oct-2022 |
| Date of Web Publication | 30-Dec-2022 |
Correspondence Address:
Dr. Annamalai Thangavelu
Department of Oral and Maxillofacial Surgery, Rajah Muthiah Dental College, Annamalai University, Chidambaram, Tamil Nadu
India
 Source of Support: None, Conflict of Interest: None  | Check |
DOI: 10.4103/jioh.jioh_119_22
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. Keywords: Bilateral Sagittal Split Osteotomy, Inferior Alveolar Nerve Injury, Mandible, Nerve Encounters, Orthognathic Surgery
How to cite this article:
Vyloppilli S, Thangavelu A, Vichattu SV, Kumar N, Ahmad F, Srinivasan P. Neurosensory deficit of inferior alveolar nerve after bilateral sagittal split osteotomy, advancement versus setback: An observational study. J Int Oral Health 2022;14:618-23 |
How to cite this URL:
Vyloppilli S, Thangavelu A, Vichattu SV, Kumar N, Ahmad F, Srinivasan P. Neurosensory deficit of inferior alveolar nerve after bilateral sagittal split osteotomy, advancement versus setback: An observational study. J Int Oral Health [serial online] 2022 [cited 2023 Nov 30];14:618-23. Available from: https://www.jioh.org/text.asp?2022/14/6/618/366426 |
| Introduction | |  |
Bilateral sagittal split osteotomy (BSSO) of the mandible is vastly used in the treatment of mandibular deficiencies and discrepancies as it offers a broad contact area for bone fragments.[1]
First introduced by Schuchardt in 1942, the credit for improving on this Osteotomy belongs to Trauner and Obwegeser, who in 1957 described their modified Sagittal Split Osteotomy. Further modification in surgical technique by Dalpont and Hunstuck, Epker, and others have made the BSSO less difficult and more predictable.[2]
However, despite its versatility, neurosensory deficit (NSD) postoperatively is common. Neurosensory disorders such as paresthesia, hyperesthesia, and dysesthesia lead to patient’s dissatisfaction.[3] A meta-analysis found a mean incidence of patient-reported NSD of 33.9%, 1 year postoperatively.[4] The risk factors for the development of NSD include older age, intraoperative encounter with the nerve, and concurrent genioplasty. The other factors such as sex and extent of BSSO on the outcome of NSD remain a matter of debate.[5],[6]
The primary aim of this study was to evaluate the incidence of NSD after BSSO advancement and setback surgeries. The secondary aim was to identify intraoperative nerve encounter status, and to analyze possible correlation in the outcome of IAN NSD after BSSO advancement and setback procedures. The null hypothesis was that there was no significant difference in the outcome (NSD) between the advancement and setback BSSO surgeries.
| Materials and Methods | | |
Type of study and delimitation
The observational study was conducted among the oral and maxillofacial surgeons in South India, who had more than 5 years of expertise in the field of orthognathic surgery due to the high learning curve.
Population and participants
The study focused on patients who had undergone BSSO surgeries, in the age group of 18–28 years who belongs to south India.
Sampling criteria with sample size calculation
The inclusion criteria of the study included surgeons of 5 years or more experience in the field of orthognathic surgery, cases of only BSSO surgeries, and patients in the age group of 18–28 years.
The exclusion criteria of the study included any previous medical history of neurosensory disorders and patients with the previous history of surgery on the mandible due to trauma or other pathology.
A total of 1600 participants were included, and the sample size was estimated by the formula = 4pq/d2.
Variables
BSSO advancement surgeries, setback surgeries, and various nerve encounter status were considered as variables as all other factors such as age and method of fixation were kept constant.
Instruments
A self-administered questionnaire (SAQ) was used which consisted of the years of experience of the surgeon, age group of patients, number of cases performed, when the NSD begin, duration of deficit, method of assessment of the deficit, whether the nerve was present on the distal fragment or proximal fragment and needed to be dissected free post osteotomy, and whether the nerve was transected and needed repair or not visible post osteotomy. The questionnaire was prepared from previous instruments that were used to evaluate the inferior alveolar nerve (IAN) injuries post-BSSO.[6]
Validity, reliability, formulation, and translation: Testing of questionnaire
The SAQ was validated, and the content validity with Aiken’s V value was 0.8. The questionnaire was forwarded to some participants in the English language and pilot tested, following which some corrections were made to the questionnaire to gain focused attention of the participants before administration [Table 1]. The study duration was set for a period of 3 months starting from May 1, 2021 to July 30, 2021 and multiple entries by a single person were avoided from the collected data. The SAQ consisted of closed-ended questions to attain uniformity in the answers.
Procedure and questionnaire process performed
The SAQ was prepared using Google Forms (Google Inc.) and was sent to the prospective participants selected by convenience sampling through various social media outlets. All the major social media outlets such as WhatsApp groups (belonging to the speciality) were used as platforms to gain maximum responses for the study.
Risk of bias and tackling process
The range of experience of the surgeons could be a potential confounder, which could lead to different postoperative outcomes. This was controlled to a certain extent by excluding surgeons with less than 5 years of experience, thereby reducing the possibility of iatrogenic nerve damage. Uniformity in the survey was made certain since the questions were provided with closed-ended answers to reduce bias.
Statistical analysis
Data were recorded as the mean and standard deviation, or the number and percentage. All statistical procedures were performed using the Statistical Package for Social Sciences (SPSS) software program, version 20.0 (IBM, Armonk, New York). Calculation for power (80%) of the study was performed before the commencement of the study. All quantitative variables were expressed in mean and standard deviation. Qualitative variables will be expressed in percentages. Chi-square test was used to find the association between variables. A probability value (P < 0.05) will be considered statistically significant at a 95% confidence interval.
Ethical policy
The study was approved by the Institutions Human Ethics Committee (IHEC), Rajah Muthiah Medical College, Annamalai University. All the study procedures were performed as per the ethical guidelines laid down by the Declaration of Helsinki (October 2013) after approval by the IHEC, Rajah Muthiah Medical College, Annamalai University.
| Results | | |
A total of 800 cases of setback and advancement surgeries done by the surgeons who participated in the study were included. The mean age of the sample was 24 ± 3 years (average 18–28 years). Following surgery, 15.1% (121) cases of advancement and 17.7% (142) cases of setback presented with NSDs post 6 months follow-up [Table 2].
In the setback and advancement procedures, the sides where the nerve got transected and repaired had a high incidence of NSD, P < 0.001, followed by the nerve in the proximal fragment which needed dissection. The lowest incidence of NSD was observed in the cases where the nerve was not visible post osteotomy and the nerve in the distal fragment [Table 3] and [Table 4]. When comparing the NSD in the advancement and setback procedures, no significant difference was observed, P < 0.08 [Table 2].
| Discussion | | |
Like all surgeries, orthognathic surgery carries the risk of accidents and complications. The adequate step toward the appropriate treatment plan is the diagnosis and proper understanding of these events,[7] to minimize the potential for these complications.
In this study, we sought to evaluate the incidence of NSD of IAN in BSSO setback and advancement surgeries. Previous retrospective studies report the IAN injury to be the most common postoperative complication with an incidence ranging from 9% to 100%.[8],[9],[10],[11],[12]
In our study, the incidence of NSD after setback surgeries was 17.7% (182) in post 6 months follow-up. Previous literature reports on NSD recovery have shown that most patients have a return of sensation within 6 months of surgery.[13] Recent literatures reported 23.91% of NSD on 6 months follow-up which was in line with our study.[1]
In the study, the incidence of postoperative NSD after BSSO advancement surgeries after 6 months was 15.1% (130) from 800 cases. Our study was in concordance with the study by Shaltout et al.[7] which had 14.1% after 6 months.
A literature review and meta-analysis concluded that the incidence of NSD after 1 year of BSSO in the recent literature ranges between 0.0% and 48.8% with a mean of 21.7%. The wide range of incidence of NSD after BSSO can be contributed to the fact that there are a number of variables such as age, type of fixation, and intraoperative nerve encounters.[7]
In the study, we have investigated the incidence of NSD in BSSO advancement and setback procedures, various nerve encounter status intraoperatively, and their possible contribution to the postoperative IAN NSD. Intraoperatively the various nerve encounter status such as nerve in the distal fragment post osteotomy, nerve in the proximal fragment and needed dissection, nerve not seen, and nerve transected and repaired were included.
Proximity of nerve in the surgical site and its manipulation when exposed during the surgical procedure contributes to the NSD, thus suggesting the role of individual anatomy.[7] According to Mackinnon et al.,[11] when the nerve is intact following osteotomy, most patients complete sensory recovery within 6 months of surgery.
Multiple technical modifications and studies have been conducted with the aim of reducing or avoiding the NSD after BSSO, including computer-assisted preoperative planning and surgical splints, modifications in osteotomy, improvising armamentarium by using ultrasonic and piezo surgical units, etc., all of which can be the future advances to decrease the NSD.[14],[15],[16],[17] Antony et al.[18] reported that patients with neuropraxia recovered from sensory deficits within several days to weeks. Others who had much more severe injury took more than 8 months to regain sensation. In their study, the amount of nerve manipulation directly affects the rate of recovery.
In our study, 1050 sites (65.5%) of the BSSO setback cases and 1000 sites (62.5%) of the BSSO advancement cases, the nerve was in the distal fragment and needed no surgical manipulation. This factor had been assumed to determine the reduced incidence of NSD in our study as compared with the literature. The NSD and its duration of repair largely depend on the type of nerve injury and degree of manipulation. Assuming all other factors are kept constant the sensory nerves that are completely severed (neurotmesis) or are crushed (axonotmesis) are more likely to suffer residual damage than those which are merely exposed in the surgical area.[3]
Studies have shown that apart from the surgical manipulation, the type of fixation employed also affects the outcome of the nerve function recovery. Studies have found that the post-BSSO surgery, the patients with monocortical fixation have a lesser chance of developing NSD.[5] In our study, monocortical screws were used for fixation and were not considered a variable.
Susarla et al.[13] in their study noted that the IAN bundle is particularly vulnerable to compression at the level of mandibular foramen during mandibular setback procedures used for correction of prognathism. When compared with the advancement surgeries, where NSD is caused due to traction, the compression injury had a lower rate of complete recovery.[8]
In our study, the incidence of NSD in setback and advancement cases were 17.7% (180) and 15.1% (130), P < 0.08, the difference not statistically significant. In the setback and advancement procedures the sites where the nerve got transected and repaired had a high incidence of NSD, P < 0.001, followed by the nerve in the proximal fragment which needed dissection. The lowest incidence of NSD was seen in the cases where nerve was not visible post osteotomy and nerve in the distal fragment.
The strength of the study was that the incidence of NSD after BSSO setback procedure was segregated and analyzed. In the literature, most of the prospective and retrospective studies on the NSD of the IAN after BSSO advancement and setback were taken as a single sample. Further efforts to assess the relation of NSD with the intraoperative nerve encounter status were accomplished in the study.
The limitation was the retrospective design, the assessment period, and that the method of assessment relied on subjective methods, which could lead to a certain degree of recall bias. Further, there could also be some amount of social desirability bias involved with the participants vying to prove their professional excellence. More specific information could be obtained using advanced objective evaluation of sensory function, that is, by quantitative sensory testing, blink reflex, sensory nerve action potentials, etc. The range of experience of the surgeons could be a potential confounder which could lead to different postoperative outcomes. In addition, it was difficult to determine the temporal link between the outcome and the exposure as both variables were examined at the same time. Various studies in the literature have observed that self-reporting by patients is a reliable indicator when compared with the objective measurement of NSD since the subjective measurement is probably more representative of the patient’s perspective.[19]
Conclusion
IAN status intraoperatively can be assumed to have a significant role in the prolonged NSD in both advancement and setback BSSO surgeries. There was no significant difference in the postoperative NSD in the advancement and setback procedures. A need for follow-up of more than 1 year is deemed necessary. Prospective randomized control studies of longer duration are suggested.
Acknowledgement
The authors would like to thank the Association of Maxillofacial Surgery and the maxillofacial surgeons for the participation and cooperation, though wading amidst the pandemic.
Financial support and sponsorship
This research did not receive any specific grant from funding agencies in public, commercial, or not-for-porfit sectors.
Conflicts of interest
There are no conflicts of interest.
Authors’ contributions
All authors listed have significantly contributed to the development and the writing of this article.
Ethical policy and institutional review board statement
The study was approved by the Institutions Human Ethics Committee (IHEC), Rajah Muthiah Medical College, Annamalai University with approval number RMMC/670/2021(dated February 25, 2021). All the study proceedings performed as per the ethical guidelines laid down by Declaration of Helsinki (October 2013).
Patient declaration of consent
Informed consent for participation in the study and publication of data for research purposes was obtained.
Data availability statement
The data set used in the current study is available upon request from the corresponding author.
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[Table 1], [Table 2], [Table 3], [Table 4]
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