Frequency of Inferior Alveolar Nerve Damage After Open Reduction and Internal Fixation in Mandibular Fractures

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Frequency of Inferior Alveolar Nerve Damage After Open Reduction and Internal Fixation in Mandibular Fractures
Surgical reduction and xation of the fracture results in damage of inferior alveolar nerve leading to sensory disturbances in the lower lip and the chin area, infection disturbed occlusion, impaired wound healing [8,9]. Inferior alveolar nerve injuries after open reduction and xation in mandibular fractures is the focus of this study. Fractures positioned amongst the mandibular foramen and mental foramen causes neurosensory variations in inferior alveolar nerve which may be due to the injury or because of open reduction and xation [10,11]. Inferior alveolar nerve Frequency of Inferior Alveolar Nerve Damage

I N T R O D U C T I O N
One of the most frequent injuries to the maxillofacial region is mandibular fracture. Numerous places experience fractures. The inferior alveolar nerve is often injured as a result of mandibular fractures. Objective: To ascertain how frequently patients in the oral and maxillofacial department of the Ayub Teaching Hospital in Abbottabad experienced inferior alveolar nerve injury following open reduction and xation of a mandibular fracture. Methods: This was a Descriptive case series carried out at Oral and Maxillofacial Department, Ayub Teaching Hospital, Abbottabad after approval from the IRB of the institution and CPSP vide number (CPSP/REU/DSG-2018-010-2532). Using the formula to evaluate proportion with absolute precision and the following premises, the sample size was determined to be 96 using the WHO software for sample size computation in health studies: The expected percentage of inferior alveolar nerve injury following xation in mandibular fracture is 45%, the con dence level is 95%, and the absolute precision is 10%.

M E T H O D S
injury is the common problem after surgical reduction and xation of mandibular fracture [4]. It might be of temporary or permanent in nature affecting the normal routine [12][13][14][15]. The main causes of neurosensory changes postoperatively include handling of fracture segments, cutting of tissue, retraction of appliances and closeness of fracture segments with the inferior alveolar nerve [16].The features that add to the nerve injury include site of the fracture, type of fracture, distance between the fragments, numbers of missing teeth and treatment used for reduction [9]. Patients with inferior nerve injury complain of sensory damage that may manifest as pain, paraesthesia, dysesthesia, hypoesthesia, hyperaesthesia and anaesthesia. Affected drinking, eating, talking abilities and lip biting are the major complains of the patients [1, 2]. The frequency of postoperative nerve damage is 0.6% to 92.3% [1-3, 7, 8]. While the reported frequency of permanent inferior alveolar nerve damage is up to 45% [2]. The study's goal was to ascertain how frequently patients in the oral and maxillofacial department of the Ayub Teaching Hospital in Abbottabad experienced inferior alveolar nerve injury following open reduction and xation of a mandibular fracture.
This was a Descriptive case series carried out at Oral and Maxillofacial Department, Ayub Teaching Hospital (ATH), Abbottabad after approval from the IRB of the institution and CPSP vide number (CPSP/REU/DSG-2018-010-2532). Using the formula to evaluate proportion with absolute precision and the following premises, the sample size was determined to be 96 using the WHO software for sample size computation in health studies: The expected percentage of inferior alveolar nerve injury following xation in mandibular fracture is 45%, the con dence level is 95%, and the absolute precision is 10%. Patients of both genders aged between 20-50 years and gone under open reduction were involved in the study while Patients reporting with pathological mandibular fracture and those who were not keen to partake were omitted from the study. Well-versed consensus was taken from the patients after ful lling the inclusion criteria. Data was collected from the Oral and Maxillofacial Surgery, ATH with the help of structured questionnaire via interview. The surgery was performed by an oral and maxillofacial surgeon. General Anaesthesia was given, mucoperiosteal ap was raised. Nerve was identi ed. Fractured segments reduction and xation was done as per requirement of the situation. After the completion of surgery the patients were followed after one week, one month and three months of duration. Statistical analysis was performed by using SPSS version 26.0. Quantitative variables like age were described as mean ± standard deviation. Categorical variables like gender, type of anaesthesia, fragment manipulation, presence of preoperative inferior alveolar nerve injury, degree of fracture segment displacement, and type of xation method were described as frequencies and percentages. Outcome variable was strati ed by gender, age groups, fragment manipulation, type of anaesthesia, degree of fracture segment displacement and type of xation method. Post strati cation Chi square test was used at 5% level of signi cance. Perioperative inferior alveolar nerve injury was observed in 56 (58.33%) patients while permanent inferior alveolar nerve injury was diagnosed in 39 (40.63%) patients (Table  2).  The frequency of inferior alveolar nerve injury in study participants was 40.63%. A broad range of IAN injury has been reported in literature and it could be due to demographics of the study participants. In general, the occurrence of IAN injur y was 33.7% beforehand management and 53.8% after management, according to a study from Singapore. In this investigation, 123 mandibular sides (43 bilateral) from 80 patients were examined. The most common causes of injuries were assault (33.8%), falls (31.3%), car accidents (25.0%), and sports injuries (6.3%). All condylar fractures (13.0%) lacked NSD, and 49.6% of the fractures elaborate the posterior mandible, which bears the IAN. Open reduction and internal xation (ORIF; 74.8%), closed reduction and xation (22.0%), and no treatment (3.3%) were the available options for treatment [1]. In dissimilarity, the follow up period for our study was very short and therefore, we were unable to determine recovery of the neurosensory de cit in our study population. In another investigation, the sharp/blunt differentiation method was used to assess the inferior alveolar nerve for neurological de cit following damage. The progression of brain recovery was evaluated over the observation period. This study comprised 52 patients with mandibular fractures affecting the ramus, angle, and body. The likelihood of neural injury to the inferior alveolar nerve was 42.3%; comminuted and displaced linear fractures were related with a higher risk of neural injury to the inferior alveolar nerve and a slower rate of recovery; and 91% of patients had their inferior alveolar nerve function return. Injuries to the inferior alveolar nerve are more common in cases of mandibular fractures affecting the ramus, angle, and body, as well as comminuted and displaced linear fractures [17]. In dissimilarity; we did not determine the mode / type of trauma to mandible and did not determine its relationship with the outcome. .In difference; our investigation did not nd a statistically signi cant correlation amongst fracture displacement and IAN damage. Subjects with unilateral mandibular fracture reported within a day after injury were monitored over the course of a year in a prospective cohort study that included sixty patients cared for mandibular fracture. 52 patients (86.7%) were found to have a post-traumatic neurosensory de cit, albeit this number fell to 23.3% over the follow-up period. Angle fracture cases (33.3%) had abnormal p o s to p e r a t i ve n e u r o s e n s o r y r a t i n g s t h a t we r e substantially greater than body fracture cases (11.1%). 90% of body fracture cases had considerable recovery associated to 67% of mandibular angle fracture cases when non-recovered and recovered neurosensory scores were related by fracture location. Neurosensory recovery scores were statistically substantially higher in cases with less than 5mm fracture dislocation (90.6%) than in cases with more than 5mm fracture displacement (59.9%) [17]. In difference; the current study did not nd any statistically signi cant association amongst IAN injury and fracture displacement. We did not take into account the location of mandibular fracture and its association with the outcome in our study population. The probability of IAN injury was 35% in a Lahore-based randomized controlled experiment

D I S C U S S I O N
*Chi-square test Similarly the difference for post-surgical inferior alveolar nerve injury among type of anesthesia (p=.851), fragment manipulation (p=.370), degree of fracture segment displacement (p=.793) and xation method (p=.793) was not statistically signi cant. The details are shown in Table 4.