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Table of Contents   
ORIGINAL RESEARCH  
Year : 2022  |  Volume : 33  |  Issue : 2  |  Page : 116-119
Incidence of inferior alveolar nerve sensory deficit and intra-operative nerve encounters after advancement of retrognathic mandible – A cross-sectional survey study


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 and Hospitals, Kothamangalam, Kerala, India
3 Department of Oral and Maxillofacial Surgery, Faculty of Dentistry, Tishk International University (TIU), Erbil, KRG, Iraq
4 Department of Oral and Maxillofacial Surgery, Jahra Specialty Dental Center, Kuwait
5 Department of Oral and Maxillofacial Surgery, Kannur Dental College, Kerala, India

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Date of Submission07-Apr-2022
Date of Decision11-Jun-2022
Date of Acceptance17-Jun-2022
Date of Web Publication13-Oct-2022
 

   Abstract 


Aims and Objectives: The aim of the current cross-sectional study was to conduct a survey among the oral and maxillofacial surgeons of South India regarding their experiences of incidence of inferior alveolar nerve (IAN) neurosensory deficit after bilateral sagittal split osteotomy (BSSO) for correction of mandibular retrognathism and to assess the intra-operative nerve encounters and its effect on the inferior alveolar neurosensory deficit (NSD), 6 months post-operatively. Materials and Methods: A self-administered questionnaire (SAQ) was prepared using Google Forms (Google Inc.) and sent to the prospective participants through various social media outlets such as Facebook, WhatsApp groups etc., of the maxillofacial surgery specialty for a period of 3 months. SAQ from surgeons with more than 5 years of experience in orthognathic surgery were included. Results: The incidence of NSD post-BSSO advancement surgery from 859 cases after 6 months was 15.1% (130). After splitting the mandible, the IAN was seen in the proximal fragment in 472 sites and needed dissection. The nerve was transected and neurorrhaphy was carried out in 26 sites. A Chi-square test was used to analyse the qualitative variables. The IAN was not visible post-osteotomy in 140 sites and in the distal fragment in 1080 sites. These groups had decreased incidence of NSD. The NSD was significantly higher in cases where the nerve was transected and sutured, P value <0.001 as compared with the other nerve status, followed by the nerve in the proximal fragment needing dissection. Conclusion: The IAN status intra-operatively can be assumed to have a significant role in persisting NSD.

Keywords: Bilateral sagittal split osteotomy, inferior alveolar nerve, mandibular retrognathism, neurosensory disturbance

How to cite this article:
Vyloppilli S, Thangavelu A, Vichattu SV, Kumar N, Ahmad F, Sayd S. Incidence of inferior alveolar nerve sensory deficit and intra-operative nerve encounters after advancement of retrognathic mandible – A cross-sectional survey study. Indian J Dent Res 2022;33:116-9

How to cite this URL:
Vyloppilli S, Thangavelu A, Vichattu SV, Kumar N, Ahmad F, Sayd S. Incidence of inferior alveolar nerve sensory deficit and intra-operative nerve encounters after advancement of retrognathic mandible – A cross-sectional survey study. Indian J Dent Res [serial online] 2022 [cited 2022 Nov 29];33:116-9. Available from: https://www.ijdr.in/text.asp?2022/33/2/116/358447



   Introduction Top


Bilateral Sagittal Split Osteotomy (BSSO) is considered one of the most common surgical procedures performed for mandibular deformities. It is indicated for the correction of mandibular excess, deficiency or asymmetry.[1] It remains an important tool for the management of mandibular discrepancies.[2],[3],[4],[5] Correcting jaw discrepancies leads to improved function and aesthetics, and the enhanced appearance also benefits the patients both psychologically and socially. However, complications can occur intra-operatively and post-operatively.

Although BSSO is considered to be a safe procedure, it is associated with specific post-operative complications. The neurosensory deficit (NSD) after BSSO is the most common complication and can cause considerable comorbidity.[6] Inferior alveolar nerve (IAN) somatosensory alteration in function ranges from 36% to 47% of the operated cases.[7],[8]

The osteotomy is performed in close proximity to the IAN and can result in post-operative NSD of the lower lip and chin. Although BSSO is the most versatile technique, NSD remains a major disadvantage of the procedure even with present modifications in the technique.[5]

Neurosensory phenomena such as hyperaesthesia, paraesthesia and dysaesthesia lead to patient dissatisfaction. There are many cases of spontaneous recovery who are unabated of their symptoms within a short duration. This is mostly determined by the factors such as the severity of nerve injury and its associated nerve repair process.[9]

The risk factors for the development of NSD include older age and intra-operative nerve encounters.[10],[11],[12],[13],[14] The influence of sex and the extent of BSSO advancement on the outcome of NSD remains a matter of debate.[14],[15],[16]

The aim of our study was to conduct a survey among the oral and maxillofacial surgeons of South India regarding their experience of neurosensory (IAN) deficit after BSSO advancement of the mandible, to assess the intra-operative encounters and its relation to NSD.


   Materials and Methods Top


The cross-sectional survey study was conducted among the Oral and Maxillofacial Surgeons in South India adhering to the ethical standards (RMCDH/656/2021). Patient consent was not required due to the nature of the study. A self-administered questionnaire (SAQ) was prepared using Google Forms (Google Inc) and was sent to the participants through various social media outlets. The questionnaire was validated, the content validity with Aiken's V value = 0.8 and pilot tested before administration. The survey questions were prepared from the previous questionnaire which was used to evaluate the IAN injuries post-BSSO.[5],[17] The study duration was set for a period of 3 months starting from 01-04-2021 to 30-06-2021 and multiple entries by a single person were avoided from the collected data. All of the major social media outlets, such as Whatsapp groups (belonging to the specialty) etc., were used as platforms to gain maximum responses for the study. The SAQ consisted of closed-ended questions so as to attain uniformity in the answers.

The sample size was determined by the formula n = Z2 α/2 × p × (1- p) × D/E2 and the prevalence was taken as 15.6% based on previous studies. The SAQ consisted of the years of experience of the surgeon, age group of the patient, the number of cases performed, duration of neurosensory 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 or the nerve was transected and needed repair or not visible post-osteotomy [Table 1].
Table 1: Questionnaires

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All statistical procedures were performed using the Statistical Package for Social Sciences (SPSS) 20.0. Calculations for power (80%) of the study were performed before the commencement of the study. All quantitative variables are expressed in mean and standard deviation. Qualitative variables were expressed in percentages. Chi-square was used for an association between variables. Probability value (P < 0.05) was considered statistically significant.


   Results Top


In the survey, 859 cases of BSSO advancement surgery for mandibular retrognathism were included. The sample's mean age was 21 ± 2.4 years (range, 18 to 28 years). The experience of the surgeons varied from 5 to 20 years.

Post splitting the mandible, the IAN was seen in the distal fragment in 1080 sites. The nerve was seen in the proximal fragment in 472 sites and needed dissection. The nerve was not viewed post-osteotomy in 140 sites. The nerve was transected and neurorrhaphy was performed in 26 sites. The total incidence of NSD after BSSO advancement surgery after 6 months was 15.1% (130) from 859 cases [Table 2].
Table 2: Complication: Neurosensory deficit in BSSO advancement

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The incidence of NSD in those cases with nerve in the distal fragment and not visible post-osteotomy was lesser. Those cases in which the nerve was transected and repaired had a higher incidence of NSD which was statistically significant (P < 0.001) followed by the nerve in the proximal fragment [Table 3].
Table 3: Nerve status: BSSO advancement

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   Discussion Top


Transient NSD is the most common complication of BSSO due to intra-operative manipulation of IAN, traction during mobilisation of the osteotomised segments, post-operative oedema and fixation devices compression.[5]

If the altered sensation in the lower lip and chin lasted for more than 1 year, it is considered a permanent NSD. IAN injury during surgery usually results from manipulation of the nerve or from direct injury to the nerve. IAN damage can consist of complete or partial transection, extension, compression, crushing or ischemia.[1] Impairment of sensory function after BSSO is not always avoidable.[5]

The transient neurosensory deficit was present in the post-operative phase for all patients and could be assessed both subjectively and objectively post-operative 1-week duration. In the study, the incidence of post-operative NSD after BSSO advancement surgeries after 6 months was 15.1% (130) from 859 cases. Similar findings were reported in a study conducted by Shaltout et al.[1] which had 14.1% after 6 months. A meta-analysis by Verweij et al.[10] reported a mean incidence of NSD of 33.91%, 1 year post-operatively. Alolayan and Leung[18] reported an incidence of NSD of 13.8% after 2 years. Politis et al.[12] reported post-operative NSD of 21.6%.

The incidence of permanent NSD in the literature is extremely variable from 0.0% up to 84.6% of cases.[1] Another literature review and meta-analysis done by Verweij et al.[10] 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 that can affect it, such as age, sex, the magnitude of movement, intra-operative nerve encounters, manipulation and type of fixation.

In our study, we investigated the incidence of nerve encounters intra-operatively, i.e., the nerve in the distal fragment, nerve in the proximal fragment and dissected free, nerve transected and nerve not visible and their possible relationship in post-operative NSD. The NSD and its duration of repair largely depend on the type of nerve injury and 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 a surgical area.[6] In our study, the IAN was in the distal fragment in 1080 sites and can be considered as a factor that has caused the reduced incidence of NSD as compared to other studies.

A limitation of the study was that the measurement of NSD relied on subjective evaluation. More accurate information could be obtained through the use of advanced objective evaluation of sensory function, i.e., by quantitative sensory testing, sensory nerve action potentials etc.


   Conclusion Top


Transient IAN somatosensory deficit is an unavoidable complication in BSSO surgery. The IAN status intra operatively can be assumed to have a significant role in the prolonged somatosensory alteration. To enhance the study compatibility, controlled prospective studies of longer duration are suggested. Further technical advancement in the BSSO techniques should aim to eliminate the need for surgical manipulation of IAN.

Acknowledgements

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

Nil.

Conflicts of interest

There are no conflicts of interest.



 
   References Top

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Shaltout SE-DG, Shahine MS, Saber DE-D, Osman MH, others. Is the magnitude of mandibular movement a risk factor for inferior alveolar nerve neurosensory disturbance after bilateral sagittal split osteotomy? Egypt J Surg 2020;39:849.  Back to cited text no. 1
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Böckmann R, Meyns J, Dik E, Kessler P. The modifications of the sagittal ramus split osteotomy: A literature review. Plast Reconstr Surg Glob Open 2015;2:e271.  Back to cited text no. 3
    
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Politis C, Lambrichts I, Sun Y, Vrielinck L, Schepers S, Agbaje JO. Attachment rate of the inferior alveolar nerve to buccal plate during bilateral sagittal split osteotomy influences self-reported sensory impairment. J Craniofac Surg 2014;25:2121-6.  Back to cited text no. 11
    
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Thygesen TH, Bardow A, Helleberg M, Norholt SE, Jensen J, Svensson P. Risk factors affecting somatosensory function after sagittal split osteotomy. J oral Maxillofac Surg 2008;66:469-74.  Back to cited text no. 15
    
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Top
Correspondence Address:
Dr. Annamalai Thangavelu
Department of Oral and Maxillofacial Surgery, Rajah Muthiah Dental College, Annamalai University, Chidambaram, Tamil Nadu
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/ijdr.ijdr_315_22

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