|Year : 2021 | Volume
| Issue : 2 | Page : 95-102
Evaluation of efficacy of lag screw fixation in the management of mandibular parasymphysis fracture
A F M Shakilur Rahman1, Ismat Ara Haider2
1 Department of Oral and Maxillofacial Surgery, Rajshahi Medical College, Rajshahi, Bangladesh
2 Department of Oral and Maxillofacial Surgery, Dhaka Dental College and Hospital, Dhaka, Bangladesh
|Date of Submission||10-Jun-2021|
|Date of Decision||02-Oct-2021|
|Date of Acceptance||08-Oct-2021|
|Date of Web Publication||11-Feb-2022|
Dr. A F M Shakilur Rahman
Department of Oral and Maxillofacial Surgery, Rajshahi Medical College, Rajshahi
Source of Support: None, Conflict of Interest: None
Objectives: Mandibular fractures are treated surgically by either rigid or semi-rigid fixation. The focus of this study was to determine the efficacy of lag screws in treating mandibular parasymphysis fractures.
Materials and Methods: We conducted a quasi-experimental study in which ten patients with mandibular sagittal parasymphysis fractures were enrolled. In these patients, two 2.0 mm stainless steel lag screws were installed for open reduction and internal fixation. Throughout the study, patients were examined for occlusion, fracture stability, screw location in relation to vital anatomical structures, reduction precision, maximum mouth opening (MMO), biting efficiency, and several other complications on the 1st day, 1st, 2nd, and 6th weeks postoperatively.
Results: All parasymphysis fractures had a good bony union after surgery. One patient had mild occlusal discrepancies postoperatively, and statistical significance was found between preoperative and postoperative occlusion (P < 0.0004). Only one patient had abnormal mobility between the fracture lines postoperatively, with a highly meaningful statistical observation (P < 0.001). The comparative statistical analysis of MMO at different follow-up periods showed highly significant (P < 0.00001) results. Substantial improvement in biting effectiveness yielded a high statistical significance (P < 0.00001). There was no evidence of postoperative complications such as wound infection, wound dehiscence, intraoral screw exposure, or mental nerve injury in any of these patients.
Conclusions: Lag screw fixation is a realistic and reliable method of internally fixing mandibular parasymphysis fractures. This technique allows the skilled surgeon to achieve optimum stability and functional healing by using the least amount of material.
Keywords: Fixation, fractutres, lag screw, mandibular, parasymphysis
|How to cite this article:|
Shakilur Rahman A F, Haider IA. Evaluation of efficacy of lag screw fixation in the management of mandibular parasymphysis fracture. Int J Oral Health Sci 2021;11:95-102
|How to cite this URL:|
Shakilur Rahman A F, Haider IA. Evaluation of efficacy of lag screw fixation in the management of mandibular parasymphysis fracture. Int J Oral Health Sci [serial online] 2021 [cited 2023 Jun 7];11:95-102. Available from: https://www.ijohsjournal.org/text.asp?2021/11/2/95/337494
| Introduction|| |
The maxilla and mandible contribute to the maxillofacial region's bony structure. Due to the presence of teeth in this area, the treatment of maxillofacial trauma is unique. Due to its location and prominence, the mandible is the most often fractured bone. Maxillofacial fractures have been attributed to a variety of causes, including road traffic accidents (RTAs), falls, assaults, gunshot injuries, sporting events, and workplace injuries. RTAs are the primary etiologies of maxillofacial trauma.
Functional inability and aesthetic disfigurement contribute to the trauma patient's misery and are a primary concern for the maxillofacial specialist. The aim of all types of treatment is to restore the structure and function of the face and jaws in order to function naturally. Over a long period, the management of mandibular fractures has changed immensely. The re-establishment of the patient's typical occlusion and anatomical bony reduction can be accomplished by different internal fixation methods.
Treatment alternatives for mandibular parasymphysis fractures range from close reduction with arch bar wiring and inter-maxillary fixation (IMF) or ivy loop wiring procedure or continuous loop wiring method to open reduction and internal fixation with wire or miniplate or compression bone plate or lag screw osteosynthesis. The lag screw is the most straightforward internal fixation device available for treating mandibular fractures. In 1970, it was incorporated into maxillofacial surgery. Niederdellmann et al. advocated that two lag screws must be required to avert rotational movement between segments in the mandibular oblique fractures. It is often used to repair mandibular oblique fractures. There are, moreover, some reports of utilizing lag screws in the treatment of mandibular symphysis, parasymphysis, body, angle, and condyle fractures.
The lag screw is threaded on its lower end and is threadless on its upper part. The threads are set distally and the head is seated against the proximal cortex, leading to compression as the screw is fixed. The advantages of lag screws over plates and screws are numerous, such as less implant content, low cost, easy technique, and simplicity. The idea behind lag screw osteosynthesis is to compress the fracture fragments by passing screws through a wider to a narrower hole on either side of the fracture (from gliding to traction hole). Passive installation of the screw is possible because of the gliding hole. Usually, as it is tightened, the inter-fragmentary distance is compressed, due to the articular portion of the screw being engaged. A single small bone plate is adequate to handle the majority of mandibular fractures, but two plates are considered necessary to resist rotational force in anterior mandibular fractures (AMFs). Two lag screws are required to handle AMFs and resist rotational forces during jaw functional activities.
Few studies have been performed to determine the feasibility of lag screw fixation in the treatment of mandibular parasymphysis fractures. The focus of this study was to assess the effectiveness of lag screw fixation in treating mandibular parasymphysis fractures. The primary outcome variables were fracture fragment stability, occlusion, reduction accuracy, screw placement assessment, maximum mouth opening (MMO), biting efficiency, and other postoperative complications.
| Materials and Methods|| |
The research was a prospective, quasi-experimental design in which patients with mandibular parasymphysis fracture were enrolled in the Department of Oral and Maxillofacial Surgery at Dhaka Dental College and Hospital in Bangladesh. The study lasted from July 2016 to June 2017. On December 28, 2016, the “Ethical Committee” of Dhaka Dental College granted approval (Ref: DDC/F-5/2016/2235). Those who had fulfilled and gave consent for the study and agreed to return for follow-up were enrolled in this study. This study enrolled ten patients who were clinically and radiographically diagnosed with mandibular parasymphysis fracture. Orthopantomogram (OPG) and occlusal radiograph were taken in all the cases preoperatively, and on 1st day, 1st week, 2nd week, and 6th week postoperatively [Figure 1] and [Figure 2]. In our study, we employed stainless steel lag screws (2.0-mm) of different lengths. The key outcome variables were the occlusion, fracture stability, the screw position assessment, the reduction accuracy, MMO, biting efficiency, and postoperative complications (wound infection and dehiscence, screw loosening, intraoral exposure of the screw, and mental nerve injury). All the parameters for functional outcomes were evaluated separately for each patient and put into a tabulated form for detailed qualitative analysis. All the patients were followed up for 1½ months. After 1½ months of follow-up, we removed the lag screws. We informed patients in detail about the procedure and the outcome of the research and received signed permission.
|Figure 1: (a) Preoperative OPG shows the mandibular left parasymphysis fracture. (b) Preoperative occlusal view of the mandible|
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|Figure 2: (a) Postoperative OPG shows the fixation of two lag screws in mandibular left parasymphysis fracture. (b) Postoperative occlusal view of the mandible shows two lag screw fixation|
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This study involved patients with unilateral, sagittal, parasymphysis fractures of the mandible who were over the age of 14 years.
This study omitted patients with comminuted mandibular fractures, midface fractures, edentulous, bone loss, pathological fractures, preexisting infection at the fracture site, and malunion or nonunion fracture.
The surgical area was infiltrated with a solution of 2% lignocaine hydrochloride with epinephrine (1:80,000). A lower vestibular incision was made to expose the fracture site. To expose the fracture site, the mucoperiosteal flap was raised [Figure 3]. Preoperative radiographs of the entire fracture were evaluated and analyzed. The position in which the lag screw should be inserted was then decided. Maxillo-mandibular fixation (MMF) was done to establish occlusion. The drill bit was mounted far away from the fracture line in the buccal cortex. A sufficient amount of bone was present between the head of the screw and the fracture line after drilling and counter-shink. The first screw was inserted just above the mandible's inferior border. This was accomplished by drilling a gliding hole with the 2.0-mm (larger drill bit) through the proximal bone to the level of the fracture line. Then, by sliding a drill guide into the gliding hole, the trajectory of the distal hole was maintained. The drill bit was then changed to a 1.5-mm (smaller drill bit) and the distal bone was drilled until the drill exited the cortex. A counter-shink hole was drilled to allow full contact between the screw head and bone. The appropriate screw length was determined by using the depth gauze. The second screw was positioned approximately 4–5 mm from the first to prevent damaging the important structures [Figure 4]. Following MMF withdrawal, proper reduction, occlusion, and segmental mobility were assessed visually and manually. The intra-oral incision was closed in two layers with resorbable 3-0 vicryl sutures beginning with the mentalis muscle and progressing to the mucosa. A tape pressure dressing was applied to the submental area to prevent the development of postoperative hematomas. The patient was prescribed a soft diet for 2 weeks. All surgeries were performed under local anesthesia with adequate antibiotic coverage. All cases were followed up for a period of 6 weeks, and on the 1st day, 1st week, 2nd week, and 6th week.
|Figure 3: Intraoral exposure of fracture site through a lower vestibular incision|
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Assessment of parameters
The following variables were clinically evaluated during follow-up of the patients: The occlusion, the stability of fractured fragments, the reduction of accuracy, screw position, and postsurgical complications (wound infection, wound dehiscence, intraoral exposure of screw, screw loosening, and mental nerve injury). All cases were followed up on the 1st day, 1st week, 2nd week, and 6th week of the postoperative day. The following systems were used to evaluate patient postoperative status in our study:
Evaluation of the occlusion
The occlusion was evaluated by differentiating into three categories: Normal occlusion (score = 3), a mild discrepancy in occlusion that required adjustment (score = 2), deranged occlusion required re-operation (score = 1).
Stability of fractured segments
This parameter was assessed by either presence (score = 1) or absence (score = 2) of mobility between fractured segments.
Assessment of the reduction of accuracy
Accuracy reduction was determined by the presence or absence of displacement between fractured segments. The patient was examined on the 1st day and 6 weeks following surgery.
Screw position assessment
The orientation of the lag screw was determined using an OPG and the occlusal view of the mandible on the1st day and 6th week postoperatively. This parameter was determined by the presence of a lag screw in three positions: Optimal anatomical location, screw penetration of adjacent root, and screw penetration of the inferior alveolar canal.
Maximum mouth opening
MMO was determined by evaluating the gap between the upper and lower central incisors' incisal edges during MMO. The inter-incisal distance was determined with the help of a divider and a scale.
Biting efficiency is described as the patient's ability to chew regular food efficiently. The assessment of biting efficiency was determined by the following scoring system; patients on a liquid diet (score = 0), chew semisolid food (score = 1), chew soft food (score = 2), and chew normal food (score = 3).
Except for the mental nerve injury, all postoperative complications (wound infection, wound dehiscence, intraoral exposure of the screw, and screw loosening) were evaluated for presence or absence. The damage to the mental nerves was classified as natural feeling, hypoesthesia, paresthesia, or anesthesia.
A standardized structured data collection sheet was used to collect the necessary information for the study sample. The data sheet included all of the study's variables. The data was processed using the Statistical Package for the Social Scientists (SPSS version 17.0, SPSS Inc., Chicago, Illinois, USA). Demographic characteristics were expressed as frequency using a tabular and graphical pattern. Assessment of the occlusion, the stability of fractured segments, the reduction of accuracy, screw position, MMO, biting efficiency, and postsurgical complications were reported. The Friedman test was used to determine the level of significance for categorical variables like occlusion, fracture stability, and biting efficiency. The one-way ANOVA followed by a post-hoc test (Tukey HSD) was used to evaluate the statistical significance of continuous variables like MMO. A statistically significant result was defined as one with a probability value (P-value) less than 0.05 (P < 0.05).
| Results|| |
The study sampled ten patients, with a male predominance (n = 8, 80%) over females (n = 2, 20%). The age of the patients ranged between 14 and 53 years, with a mean of 24.1 years. The age group of 14–23 years (50%) was the most affected, followed by 24–33 years (30%) and 34–43 years (10%). The age group that was least affected (10%) was those aged more than 43 years [Figure 5].
Intra-operatively, all cases had satisfactory occlusion. A minor occlusal discrepancy was observed in one patient 2 weeks after surgery. However, by the 6th postoperative week, all patients had acceptable occlusion. Statistical analysis showed (P < 0.00046) a high statistical significance between preoperative and postoperative occlusion [Table 1]. Stability was achieved intra-operatively in all instances. At the 2 week postoperative follow-up, one patient (10%) had abnormal mobility. Segmental stability was observed in all cases 6 weeks after surgery. Statistical analysis showed a significant difference (P < 0.001) between preoperative and postoperative stability between fractured segments [Table 2].
|Table 2: Stability at preoperative and postoperative follow-up periods (n=10)|
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In all cases, the screws remained in an appropriate natural anatomical location without causing any injury to the teeth roots or inferior alveolar nerve [Table 3]. There was no displacement of fracture fragments on the 1st day and 6th-week except in one (10%) case on the 2nd week postoperatively. We treated this patient by extracting a tooth from the fracture line and then providing MMF for 3 weeks [Table 4]. The mean MMO (standard deviation [SD]) on the last follow-up was 38.3-mm (1.7). The comparative statistical analysis of MMO in different follow-up periods showed highly significant (P < 0.00001) results [Table 5]. [Table 6] demonstrates that the Friedman test yielded a P = 0.00001, indicating a substantial improvement in biting effectiveness. Postoperative complications like screw loosening occurred in one (10%) patient, and two (20%) had paresthesia in the lower lip, indicating the mental nerve injury intra-operatively [Table 7].
|Table 5: Statistical analysis of maximum mouth opening among study sample (n=10) during follow-up periods|
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| Discussion|| |
The lag screw allows rigid fixation for the AMFs for three reasons, such as curved region of the anterior mandible, the thickness of the mandibular cortical bone, and the absence of significant anatomical structure except the mental nerve. Mandibular fractures may be managed by closed treatment with IMF, which has some disadvantages. Moreover, the IMF is not indicated for some patients. After IMF removal, the patient may experience periodontal problems and trismus. The lag screw is an alternative to miniplate fixation for the treatment of AMFs with some beneficial effects. The beneficial effects of the lag screw fixation are early mobilization with fewer postsurgical complications in comparison to IMF.
We fixed double lag screws in the parasymphyseal area to accomplish optimum stability and reinstallation of occlusion. We did not use an arch bar or miniplate at the superior border to resist rotational forces to prevent subsequent inter-fragmentary displacement and secondary malocclusion. In this study, a screw with a diameter of 2.0 mm was used. This diameter was smaller than those used in previously published reports, in which 2.3-mm and 2.7-mm screws were utilized., The lag screw of 2.0-mm in diameter, was applied in the parasymphysis fractures, proving their efficiency. We made use of a 20.0-mm length with a 2.0 mm diameter lag screw. The length of lag screws varied from 12 to 40 mm, exercised for the fixation of AMFs.
The mean age of patients was 24.1 years, ranged from 14 to 53 years. Patients' peak frequency was in the age groups of 14–23 years (50%). This outcome is consistent with a previously published report. The possible explanation for the greater rate of occurrence of fractures in the age group 21–30 years is that these age groups show more activity in sports, fights, violent activities, and high-speed transportation. The majority of patients were male (80%), with a male-to-female ratio of 4:1. Our results coincide with previously published reports.,
We accomplished intraoperative stability in every patient following fixation of the lag screw. On the 2 week postoperatively, we discovered mobility in one patient (10%). This may be because of the presence of an infected tooth in the fracture edge. The patient was treated with tooth extraction and MMF for 3 weeks. On the 6th week postoperatively, we found no evidence of bony instability between fracture segments. A potential explanation for postoperative mobility is the prevalence of contaminated teeth between the fracture lines.
The key focus of mandibular fracture repair is to restore occlusion. Before applying any material, the occlusion must be formed with MMF. In the current study, we used MMF to achieve occlusion before installing the lag screw. At the 2 week postoperative follow-up, we discovered minor occlusal inconsistency in one (10%) patient. It was caused by a dislodged screw, which was handled for 3 weeks with MMF. Following a 6 week follow-up, these patients' occlusions were satisfactory. We encountered no postoperative deranged occlusions that necessitated reoperation. Our results corroborate previously reported findings. Kallela et al. stated that lag screw fixation of mandibular parasymphysis and angle fractures resulted in minor occlusal change.
Postoperative dislodgment of fracture segments was not observed in all cases, except in one (10%) patient, who had fracture fragments noticed to be separated 2 weeks after surgery. The fracture line of this patient was infected by a tooth. Later, this tooth was extracted and treated with MMF fixation for 3 weeks postoperatively. Otherwise, no displacement of the fracture was detected on the 1st day or 6th week following surgery, according to radiological assessment. According to Kallela et al., lag screw fracture fixing results in anatomic reduction without visible dislocation in 21 (88%) cases, mild displacement in two (8%) cases, and osteosynthesis failure in one (4%) event. The screw caused no damage to the inferior alveolar canal or the roots of the lower anterior teeth. The findings corroborated the previous study.
No patients were held on MMF in our experiment, so their dietary health was not affected. We found significant biting efficiency following treatment with lag screw. Patients could be able to chew from a liquid diet to a normal diet gradually with advancing time. Bansal et al. conducted a study to evaluate the effectiveness of lag screw in the treatment of mandibular fractures and concluded with a gradual improvement of biting efficiency following treatment at the last follow-up. Bhatnagar et al. showed improving biting efficiency with a gradual increase in the bite force in the lag screw treated patients when compared to mini plate treated groups.
We recorded MMO at the different follow-up periods. The mean preoperative MMO (SD) was 17.5-mm (2.76), improved to the reading of 38.3-mm (1.70) on the 6th-week postoperative follow-up. The result showed a high statistical significance on the comparative analysis of MMO. Mittal et al. found more improvement of MMO with statistical significance in lag screw treated AMFs in comparison to mini plate treated patients.
None of the ten patients preoperatively had a neurosensory deficiency. We did not observe any cases of lower lip paresthesia during our study, but two patients did in the 1st and 2nd weeks following surgery. They were advised to take Vitamin B complex for 1 month. At the most recent follow-up, none of the patients demonstrated evidence of mental nerve injury. Paresthesia of the lower lip during surgery may be affected by compression or traction of the mental nerves during the operation. On radiographic inspection, no screws were found to be displaced into the inferior alveolar nerve canal. In a study conducted by Kallela et al., patients with parasymphyseal fractures had no neurosensory scarcity before surgery. Postoperatively, neuro-sensory deficiencies in the lower lip and/or chin were exposed in eight patients (68%). These cases improved within an average of 5.4 weeks. The authors attribute this to the operation's stretching of the mental nerve and soft tissues.
The lag screw, a rigid form of fixation, has a number of advantages over the bone plate. The primary benefit is that it can be used more easily, as the time-consuming process of adapting the bone plate is eliminated. Even so, a small discrepancy in the contouring of the plate can result in fracture displacement. Displacement of bony segments is less common when lag screws are used. Lag screws have optimum stability by using the least amount of implant material possible. Additionally, the lag screw is less expensive than the bone plate.
| Conclusions|| |
Lag screw fixation can be a viable alternative for mandibular parasymphysis fracture management. It results in natural bone healing without causing long-term neurosensory disruption or the likelihood of abnormal occlusion. This technique enables the specialist surgeon to accomplish the optimal level of stabilization and functional healing using the minimum possible materials. Despite the study's small sample size, it can be concluded that lag screw fixation is an efficient treatment option for mandibular parasymphysis fractures.
On 28th December 2016, the “Ethical Committee” of Dhaka Dental College granted approval (Ref: DDC/F-5/2016/2235).
The participants who took part in this research gave their written permission.
The corresponding author wishes to express his gratitude to Professor Dr. Tarin Rahaman and Assistant Professor Dr. Farjana Sultana for their assistance during the study period.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3], [Figure 5], [Figure 4]
[Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6], [Table 7]