|Year : 2021 | Volume
| Issue : 3 | Page : 221-227
Treatment of anterior mandibular fractures by lag screw - A systematic review
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 Web Publication||23-Aug-2021|
A F. M Shakilur Rahman
Department of Oral and Maxillofacial Surgery, Rajshahi Medical College, Rajshahi
Source of Support: None, Conflict of Interest: None
Different techniques that meet the basic principles of open reduction and internal fixation with either plates and screws or lag screws may treat anterior mandibular fractures (AMFs).This review article aims at assessing the effectiveness of lag screw fixation in the treatment of AMFs. Using the following electronic databases, a systematic electronic search was carried out: PubMed, Elsevier, Google Scholar, and Wolters Kluwer. The following search words were used in single or in combination: AMFs, fixation, and lag screw. Any randomized or quasi-randomized controlled trials, controlled clinical trials, or retrospective studies regarding the lag screw fixation in the management of AMFs were included. Studies of more than 10 years were not included in this study. This study was reviewed in compliance with the PRISMA guidelines. A total of 13 articles were included in the qualitative synthesis of this review. The majority of the studies were comparative studies between the lag screw and the mini plate. In lag screw groups, the duration of surgery, postoperative radiographic distance, and biting ability reported better outcomes than in miniplate groups. A sensitive, simplistic, accurate, and relatively inexpensive approach to internal fixation for AMFs is the lag screw fixation. The Lag screw provides an effective and rapid rigid internal fixation in the treatment of AMFs. Although it is a technique-sensitive procedure for fixation of AMFs, it permits the skilled surgeon to achieve the most favorable stability and functional rehabilitation with the minimum amount of materials.
Keywords: Anterior mandibular fractures, fixation, lag screw
|How to cite this article:|
Shakilur Rahman A F, Haider IA. Treatment of anterior mandibular fractures by lag screw - A systematic review. J Dent Res Rev 2021;8:221-7
|How to cite this URL:|
Shakilur Rahman A F, Haider IA. Treatment of anterior mandibular fractures by lag screw - A systematic review. J Dent Res Rev [serial online] 2021 [cited 2022 Aug 18];8:221-7. Available from: https://www.jdrr.org/text.asp?2021/8/3/221/324413
| Introduction|| |
Owing to its position and prominence, the second most fractured bone of the maxillofacial skeleton is the mandible. Even though the percentage of anterior mandibular fractures (AMFs) varies widely, AMFs form a significant entity of mandibular trauma (14%–30% of all mandibular fractures) in the previously published work.,, AMFs are classified as mandibular fractures that include the region of the mandibular symphysis and parasymphysis region bounded by the vertical lines on either side just distal to the canine teeth.
The key goals for the mandibular fractures management should comprise healing of fractured fragments to restore oral function, return preinjury force, and avoid fractured site infection. To achieve these results, adequate reduction, fixation, and immobilization of fractured segments to be part of the strategy of management. Various approaches of fixation have developed in the maxillofacial surgery, for example, wires, pins, staples, plates, and screws. Different degrees of rigidity results in these fixation approaches ranging from nonrigid fixation (e.g., wires), semi-rigid fixation (e.g., mini plates), to rigid fixation (e.g., compression plates and lag screw method). AMFs can be managed by various techniques that follow precise theories of open reduction and internal fixation (ORIF) with either plates and screws, or lag screws. Lag screw fixation for AMFs is a responsive, simplistic, reliable, and relatively affordable approach for internal fixation of suggested fractures.
The lag screw technique was first used as an option in the treatment of maxillofacial trauma in 1970. Later on, it was reintroduced by Niederdellmann et al., subsequently claimed that as a minimum two screws were required to avoid the rotational movement of the broken segments in the mandibular oblique fractures. For three factors, the anterior mandible is suitable for the lag screw fixation. First, the anterior mandibular curvature allows lag screws to be set around the symphysis, for sagittal fractures, from one buccal cortex to the other buccal cortex across the fracture line, and for oblique fractures, from anterior to posterior. Second, the bony cortex of the anterior mandible is thick enough to permit very stable fixation when the lag screws are introduced precisely. Finally, under the apices of the teeth, there are no anatomical risks until the mental foramen is met. This creates lag screw positioning extremely easy, secure, and consistent in the AMFs.
During the past several decades, the management of AMFs has advanced, with the implementation of ORIF procedures in particular. This review is aimed to discuss the effectiveness of lag screw fixation in the treatment of AMFs.
| Materials and Methods|| |
Using the following electronic databases, a systematic electronic search was carried out: PubMed, Elsevier, Google Scholar, and Wolters Kluwer. Literature in English was only considered for this review. Manual exploration of oral and maxillofacial surgery-related journals was also performed. The terms AMFs, fixation, and lag screw were used separately or in combination. The aim of this review article is to evaluate the lag screw's efficacy in managing AMFs. To identify appropriate published studies, the following inclusion and exclusion criteria were considered. The PRISMA guidelines were implemented during the conduct of this review [Figure 1].
Any randomized or quasi-randomized controlled trials, controlled clinical trials, or retrospective studies were considered to determine the efficacy of lag screw installation in the management of AMFs. Case reports, technical reports, animal experiments, in vitro studies, and review articles were removed, as were studies that involved contaminated and/or comminuted AMFs, edentulous mandible fractures, and pediatric AMFs. This study omitted articles with a period of more than 10 years.
The primary computer search technique and a supplementary manual search resulted in the exploration of 56 publications [Figure 1]. Initially, the reviewer picked the articles based on their titles and abstracts, and 13 were rejected due to their failure to meet the eligibility criteria. Of those 43 papers, 7 were disqualified as in vitro studies, or review articles. The remaining 36 publications that matched the eligibility requirements were thoroughly studied. Of these 36 papers, only 13 articles satisfied the inclusion requirements for our review purposes.
All studies derived from the archives were carefully checked for validity. The following data were derived from the trials included (when accessible): authors, year of publication, study design, number of participants, mean age in years, time of follow-up, fracture sites, fixation techniques, outcomes, and risks.
| Results|| |
We included a total of 13 research papers that met our review study's inclusion requirements. These studies were conducted over a period of 10 years (from 2010 to 2020). [Table 1] summarizes the outline of these research findings.
| Discussion|| |
Due to three considerations, the lag screw ensures rigid fixation for AMFs: the mandible's curvature, the breadth of the cortical bone, and the absence of major anatomic structures except the mental nerve beneath the tooth apices. Treatment options for AMFs include close reduction with arch bar wiring and inter-maxillary fixation (IMF), ivy loop wiring, and continuous loop wiring process. AMFs are also managed by ORIF with wire, mini plate, bone plate, and lag screw.
The oblique mandibular fractures are usually repaired by lag screws. It has been documented that the lag screw is employed to stabilize the mandibular body, angle, and condyle fractures. In orthognathic surgery, it is used primarily for sagittal split osteotomies and genioplasties. The single isolated bone plate is capable enough to handle most mandibular fractures, while two bone plates must be required to resist rotational force in the AMFs. The installation of double lag screws is required to withstand rotational force in the AMFs. Ellis and Ghali employed a combination of a lag screw with a compression plate to handle AMFS. Another study reported that a solitary lag screw through the fracture edge combined with an arch bar is rigid and efficient enough to handle AMFs without requiring additional support from the IMF [Figure 2].
|Figure 2: Orthopantomogram (OPG) shows a lag screw in combination with an arch bar to treat right parasymphyseal fracture.|
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True lag screws have threads just on the bottom portion of the screw [Figure 3]a. By over drilling the proximal cortex and threading just the far cortex, it is possible to use the cortical screw as a lag screw [Figure 3]b.,,,,, When adjusting the screw, the threads of the true lag screw are installed at the distal cortex and the head is placed against the proximal cortex. The principle of lag screw positioning is predicated on the concept of osteosynthesis by bone compression. A specialized drilling approach and sequence are used to achieve the desired compression during reduction and repair. Compression is achieved by preparing the adjacent cortex (gliding space) osteotomy hole to a diameter that corresponds to the screw's outer diameter. As a consequence, if the screw head is flush with the cortex's outermost surface, the adjacent cortex is not activated. Screw threads extend to the far (distal) cortex, which has been designed to accept the screw's core diameter (traction hole). Tightening the screw causes the far cortex to migrate toward the near cortex, facilitating compression between fracture fragments.
|Figure 3: (a)Lag screw. Note the lack of threads except at the screw end, (b) Cortical screw.|
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Applying lag screws for AMFs needs relatively few instruments [Figure 4], but the technique requires the right equipment (instruments for AO/ASIF are obtainable from Orthomax Manufacturing Ltd., India or other manufacturers). For the management of AMFs, the 2.7-mm lag screw prerequisite is essential. The length of the screw varies depending on the need. However, the diameter of the lag screw varied in the previous studies. The diameter of the screw was either 2.7-mm,,, or 2.5-mm,,,,, used previously. Emam and Stevens used 2.0-mm true titanium self-tapping lag screw in their study. The material of the lag screw may be either stainless steel, or titanium.,,
The arch bar wiring is done in both jaws before having a lower vestibular incision to expose the fracture site. The mucoperiosteal flap is raised to reveal the fractured area [Figure 5]. The entire fracture and the preoperative radiographs are compared and examined. After inspecting the fracture site, debris is cleaned and maxillo-mandibular fixation is done with simultaneous reduction of the fracture. The drilling on the buccal cortex should be started at a distance from the fracture line so that a significant amount of bone remained to seat the screw head after finishing the procedure. This principle is important while drilling through the curved anatomy of the symphyseal and parasymphyseal regions. The screw head should sit firmly on the remaining bone to withstand chewing forces. Sufficient space must be required for the placement of a second screw. Therefore, just above the inferior border, the initial screw must be mounted [Figure 6].
|Figure 6: (a) The intra-operative image depicts the position of two lag screws perpendicular to the fracture from one buccal cortex to the other, (b) Postoperative OPG shows two lag screws placement, (c) Postoperative occlusal view of mandible shows lag screw placement.|
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The 2.7-mm drill bit is used for the drilling of the proximal buccal cortex or near segment after determining the right angulation and entry point. The drilling must end at the fracture line. The proximal buccal cortex is countersunk to get a secure screw-head positioning framework. The next step is to drill through the distal (far) segment with a smaller (2.0-mm) drill bit. A drill guide with an outside diameter of 2.7-mm is employed in the gliding hole (2.7-mm hole). The 2.0-mm drill bit is put through the drill guide and the drilling begins in the distal (far) segment until it exits through the buccal (sagittal fractures) or lingual cortex (oblique fractures).
There is also an alternative technique of drilling. Both holes can be drilled with the smaller drill bit first, then using the wider drill bit up to the fracture line, create the gliding hole in the nearby cortex. Sluggish, adequate irrigation must be used during the drilling, and the drill flutes must be removed continuously to wash the bony residue. Otherwise, the drill becomes very warm due to the clogged flutes with the bony residue.
The depth gauge is essential to measure the screw's valid length for fixation. The hole is then tapped employing an elongated tap in the distal (far) segment. The hole must be irrigated prior to installing the screw. After determining the exact length, a lag screw is installed using a screwdriver. Then, via the gliding hole (proximal or nearby segment), the screw is positioned to insert the traction hole (distal or far segment). The screw does not contact the proximal or nearby segment due to the screw diameter matching the diameter of the gliding hole. As a result, once installed, a screw must simultaneously compress the two bone segments.
The inaccurate positioning of lag screws leads to imprecise reduction, complications, and/or lack of stability. The medullary bone is insufficiently resistant to lag screw fixation. Therefore, the bony cortex should always be employed with the screw. Never obliquely insert the screw into symphyseal sagittal fractures, as this can result in segment separation. In addition, the screw's location in the lingual cortex, so adjacent to the fracture line, can cause to fracture instability. The best outcomes for different types of AMFs are dependent on proper screw placement: first, the screw must be perpendicular or nearly perpendicular to the fracture line when it is sagittal, and second, it must be inserted at right angles to the fracture line as possible when it is oblique.
The plurality of the trials cited in this review compared the lag screw and the mini plate. This research brought to an end that in terms of stability and occlusion, there was no statistically meaningful discrepancy between lag screws and the mini plate group. In the mini plate groups, mild postoperative complications such as wound dehiscence, inflammation, and swelling were observed. However, lag screw groups achieved better outcomes in terms of surgical period, postoperative radiographic distance, and biting ability than mini plate groups.,,,,,
Tiwana et al. performed a retrospective analysis to determine the difficulties associated with AMFs lag screw fixation. Complications such as fixation loss, nonunion, delayed union, and contamination were discovered. The major complication occurred during the procedure in six patients due to a broken drill bit. However, the majority of faults or complications occur as a result of an operator's decision or technique.
| Conclusions|| |
Lag screw fixation presents many benefits for rigid internal fixation of AMFs. It is an effective way to achieve fast and efficient fixation, preceded without any significant complications by primary bone healing without lasting neuro-sensory disturbance or the increased possibility of abnormal occlusion in the AMFs. This method permits the skilled surgeon to attain the most favorable stability and functional rehabilitation with the least amount of materials.
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Conflicts of interest
There are no conflicts of interest.
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