|Year : 2014 | Volume
| Issue : 3 | Page : 180-185
Solitary lag-screw fixation for mandibular angle fractures: Prospective study
Sasikala Balasubramanian1, C Kumaravelu2, P Elavenil1, VB Krishnakumar Raja1
1 Department of Oral and Maxillofacial Surgery, SRM Dental College and Hospital, Ramapuram, India
2 Department of Oral and Maxillofacial Surgery, Tamil Nadu Government Dental College and Hospital, Chennai, Tamil Nadu, India
|Date of Web Publication||14-Aug-2014|
Department of OMFS, SRM Dental College and Hospital, Ramapuram, Chennai - 600 087, Tamil Nadu
Aim: The aim of the prospective clinical study was to evaluate the efficacy of "solitary lag-screw fixation" in treating mandibular angle fractures. Materials and Methods: Five cases of mandibular angle fracture were taken up for the study. All cases were treated with solitary lag-screw technique according to principles outlined by this technique using 2.7 mm stainless steel screws. Postoperative complications such as wound dehiscence, infection, neurosensory disturbance, mal-occlusion, nonunion, and postoperative mouth opening were recorded for follow-up of 6 months. Observation and Results: The patients were evaluated postoperatively for 6 months. All the cases achieved long-term occlusal stability, interincisal opening of 35-45 mm, and showed no signs of infection or neurosensory disturbance. Conclusion: Solitary lag-screw fixation is an effective and simple procedure in producing good treatment results for angle fractures of mandible, but is technique sensitive and requires surgical expertise.
Keywords: Lag-screw, mandibular angle fracture, technique sensitive
|How to cite this article:|
Balasubramanian S, Kumaravelu C, Elavenil P, Krishnakumar Raja V B. Solitary lag-screw fixation for mandibular angle fractures: Prospective study. SRM J Res Dent Sci 2014;5:180-5
|How to cite this URL:|
Balasubramanian S, Kumaravelu C, Elavenil P, Krishnakumar Raja V B. Solitary lag-screw fixation for mandibular angle fractures: Prospective study. SRM J Res Dent Sci [serial online] 2014 [cited 2019 Jul 20];5:180-5. Available from: http://www.srmjrds.in/text.asp?2014/5/3/180/138736
| Introduction|| |
One of the most demanding aspects of dental and surgical practice is the management of the patient who has suffered facial trauma. Mandibular fractures outnumbered zygomatic and maxillary fractures by a ratio of 6:2:1, respectively. The etiology of mandibular fractures includes mainly assaults and road traffic automobile accidents. In addition, fall and sports injuries are the most common causes for mandibular fractures.
Fractures of the mandibular angle are common injuries, comprising approximately 30% of mandibular fractures. There are several proposed reasons including:
- The presence of third molars. ,
- A thinner cross-sectional area than the tooth-bearing region.
- Due to curvature of trajectories in the angle region.
- The lingual surface of the mandible in the region of the second and third molars is one site of maximum tensile strain resulting from anterolateral application of force on the same side.
- The weakness of the angle is produced by the abrupt change in direction between the body and ascending ramus in two planes. In the vertical plane, change in direction is almost 20°, while in the horizontal plane it is about 70° at the upper border.
- The insertions of the masseter and medial pterygoid muscles comprise a great source of strength to the ascending ramus, and the anterior limit of their insertion lies just behind the third molar.
Fractures of the mandibular angle represent an important clinical challenge because their treatment is associated with the highest postsurgical complication rate of all mandibular fractures. It has been suggested that rigidity is important to resist infection in mandibular fracture. As a result, many forms of treatment have been used to manage such fractures. Open reduction and internal fixation of mandibular fractures, using plates has become a widely accepted method during past five decades. In contrast to orthopedic surgery, lag screws play a minor role in maxillofacial osteosynthesis. However, besides rigid fixation, lag screws possess distinct advantages compared with plates in appropriate indications, especially in mandibular fractures.
In osteosynthesis, the requirement of minimum implant material with maximum stability always should be considered. This goal is particularly appropriate for lag-screw osteosynthesis. Brons et al. first introduced lag-screw osteosynthesis to maxillofacial surgery in 1970, not only does it immobilize fracture fragments it also produces a constant compression in the fracture area.
Ellis 3 rd and Ghali (1991) reported a technique for treating fractures of the mandibular angle to facilitate anatomic reduction and stable fixation even in severely displaced fractures. 
| Materials and methods|| |
In this study, stainless steel cortical screw was used for osteosynthesis with following specifications: [Figure 1] and [Figure 2]
External diameter −2.7 mm, head diameter −5.00 mm, total length-varies from 30 to 40 mm, head type-slotted and nontapping type.
Five cases of fracture, mandibular angle were taken up for the study. A complete and detailed history was taken from each patient in a standardized method. On inspection ecchymosis, swelling, soft tissue lacerations, obvious deformity of the bony contour if any, were noted down. On palpation tenderness, step defects in the bone, anesthesia or paresthesia of the lower lip, mobility of the teeth, and mobility of fractures across the site of fracture were recorded. In addition etiology, number and location of fracture and presence of preoperative infection was also recorded.
All cases were treated with solitary lag-screw technique according to principles outlined by this technique using 2.7 mm stainless steel screws. Following application of arch bars/eyelets, under local anesthesia (LA)/general anesthesia (GA), vestibular incision is made from the retro molar area to the maxillary canine. Sub periosteal dissection of the lateral and inferior borders of the mandible from mental foramen to just behind the fracture site is essential for exposure of the fracture and for instrumentation. Mandible is placed in intermaxillary fixation (IMF) while simultaneously reducing the fracture. A 4 mm extra-oral stab incision is made through the skin at the inferior border of the mandible in the area of the first premolar. A hemostat is used to bluntly tunnel through the subcutaneous tissue in a posteromedial direction until the elevated periosteum is punctured [Figure 3]. A 2.7 mm drill guide is then inserted through this tunnel, followed by a 2.7 mm drill.
|Figure 3: Exposure of fracture site, stab incision, drilling the distal fragment|
Click here to view
Selection of point of entry is based on two factors. First factor is the initial point of entry should be approximately 12-15 mm anterior to the fracture. Most commonly the point of entry will correspond to the anterior aspect of the external oblique ridge as it tapers down into the mandibular body. In this manner, a sound bony buttress will remain following countersinking. Second factor is initial drill entry in superior-inferior position. The best method to determine this is by laying the 2.7 mm drill over the top of the mandible, establishing proper mediolateral and superior-inferior angulation, retracting the drill until the proper anteroposterior position is found, and using this superioinferior angulation thus, established in drilling a hole.
The path of screw insertion is predicted on securing the terminal screw threads in bone that is dense enough to provide rigid fixation. This can usually be achieved by the path of screw insertion that is approximately 10°-20° from the buccal cortex. Using this path of insertion, the screw will come out posterior to the temporal crest of the mandible.
Once the proper angulation and point of entry is established, drilling the outer cortex should proceed. The 2 mm drill in the drill guide is inserted through the stab incision and is initially placed almost perpendicular to the buccal cortex at the selected point of entry to prevent skidding of the drill bit, and a hole is made through the buccal cortex. The drill is then redirected to the previously selected angulation and the drilling completed through the buccal cortex and medullary bone of distal fragments only [Figure 3].
It is imperative that while countersinking, two factors be considered. First, the same angulation must be used as established by the initial 2.7 mm drill hole. Second, countersinking must be adequate to allow complete seating of the screw head. Because head of a 2.7 mm screw is 5.0 mm in diameter, and other 1.2 mm of bone must be removed from the buccal cortex on the medial side of the drill hole [Figure 4].
Drilling through the proximal fragment with the 2.0 mm drill is the next step. To ensure that the 2.0 mm is perfectly centered in the 2.7 mm hole previously drilled through the buccal cortex, a special drill guide is used. This guide had an outer diameter of 2.7 mm on its working end, allowing a snug fit into the hole previously drilled through the buccal cortex. It has an inner diameter of 2.0 mm, acting as a drill guide for the 2.0 mm drill, perfectly centering it within the 2.7 mm hole in the buccal cortex. During drilling of the proximal segment with the 2.0 mm drill, it is imperative that the fracture be anatomically reduced. Once properly reduced, drilling through the proximal segment with the 2.0 mm drill is performed [Figure 4].
A long depth gauge is inserted through the stab incision, and the screw length is determined. The hole in the proximal segment is tapped using a long tap.
After selection of appropriate length of screw, it is inserted into the screw hole with a screw driver. Before the last few turns of the screw are accomplished, attention to the fracture site is mandatory to assure that it is perfectly reduced along its entire length. It is essential that the screw exit the lingual cortex of the proximal segment for maximal strength [Figure 5].
Maxillomandibular fixation (MMF) should be released at this point and the rigidity of the fracture tested. The intraoral incision is closed in one layer with resorbable sutures. One monofilament suture is placed to close the dermal surface of the trocar incision.
All patients were kept under antibiotic cover for 1 week. Sutures were removed on the 7 th postoperative day. Follow-up was performed, weekly during the first 6 weeks and thereafter monthly for 6 months. Postoperative complications such as wound dehiscence, infection, neurosensory disturbance, mal-occlusion, nonunion, and mouth opening were recorded.
| Observation and results|| |
Five patients with fracture mandibular angle were chosen of which two patients were isolated angle fracture and three patients with mandibular angle and contralateral body/parasymphysis fracture. All patients were treated with single-lag screw fixation. All patients were males ranging in age from 20 to 35 years. The cause of injury was assault, sports-related, and industrial-related injuries. Patients presented to the hospital within 2-10 days of trauma. The time of injury to treatment ranged from 4 to 12 days. All five patients who underwent an application of single-lag screw were postoperatively evaluated for 6 months by clinical examination and radiographs [Figure 6] .
The results of this study indicate that lag-screw fixation of mandibular angle fractures is a simple, but extremely technique sensitive method of rigidly securing fragments in mandibular angle fractures. All patients showed stable occlusion postoperatively. Postoperative radiographs taken within first 2 days showed excellent reduction in four cases and moderate reduction in one case. All the cases achieved long-term occlusal stability.
| Discussion|| |
It is the angle region, where the horizontal and vertical rami of the mandible join and where the powerful elevator muscles attached to the ramus transfer there force to the body of the mandible which creates great demands for fixation, if rigidity under functional loads is to be maintained.
With recent enthusiasm for rigid forms of internal fixation, experimentation with various forms of plate and screw fixation has been attempted. In general, this can be divided into those techniques that use large bone plates with or without compression) secured near the inferior border of the mandible or miniplates (without compression) applied to the superiolateral border of the mandible. Both of these techniques have advantages and disadvantages. The large bone plates are more difficult to place than miniplates in the mandibular angle region through transoral approach.
The advantage of miniplate technique is that small plates are secured along the external oblique ridge, facilitating access. The main problem with this technique is that is not truly a rigid technique. These plates essentially provide stable fixation only at the superior border of the mandible, neutralizing the tension zone during function. The nonrigidity of this technique has prompted most surgeons to use varying periods of MMF following surgery and to limit the diet to very soft foods.
In 1981, Niederdellmann  described a method of internal fixation of mandibular angle fractures using lag screws. The anatomy of the mandible and technique of screw placement is understood, lag-screw fixation makes very good sense. A distinct advantage over the miniplate system, however, is the ability to apply great compression between the fragments to promote healing and to stabilize the entire length of the fracture.
The concept of lag-screw osteosynthesis is defined as the stable union of two-bone fragments under pressure with the aid of screws, which in turn are under tension.
Healing of fractures is extremely susceptible to mechanical influences. Mobility at the fracture site is one of the main causes of healing disturbances. There is a direct relationship between the amount of periosteal callus and the degree of mobility in the fracture area. The greater the instability, the more voluminous the callus becomes.
If the fragments are fixed together, so that the movement in the fracture area is impossible, periosteal callus formation does not take place. Fracture healing in these cases takes place by primary intention. To achieve successful stabilization of the fracture, at least two factors come into play, the amount of bone contact and the rigidity of the fixation device.
Kushner and Alpert  described these factors as stabilization by compression and stabilization by splinting. Unless compression is achieved across the fracture, the stability of the fracture is dependent on the rigidity of the fixation system, without the benefit of friction between the bony surfaces. If after the fracture reduction a space exists between the ends of the fracture, the fixation devices will be under great force, possibly leading to deformation of the plate, fracture of the plate or loosening of the screws.
The experiments have shown that primary healing of the bone can be expected only if there is absolute rigid fixation of the fragments. Only when absolute immobility is not maintained in the vicinity of the fracture is there a danger of infection to the damaged area. Bone healing takes place more rapidly under application of axial pressure than in osteosynthesis without pressure. It has been suggested that rigidity is important to resist infection in mandibular fracture. A lower incidence of infection due to the absence of inter-fragmentary mobility is also reported as an advantage to the lag-screw technique.
The mandible in the molar area has a relatively wide lateral extension because of external oblique line. Under functional pressure, traction forces occur in the alveolar process in this area.
This anatomical and biochemical condition makes the mandibular angle region especially suitable for a so-called tension band that will effectively eliminate all dynamic forces in the region of the fractures. Therefore, lag-screw osteosynthesis appears to be particularly suitable for the treatment of fractures of the mandibular angle.
The use of lag screws has several advantages over the use of bone plates:
- It uses less hardware making it more cost effective.
- It also does not cause facial asymmetry due to a large volume as plates sometimes may.
- When properly applied lag screws provide a very rigid method of internal fixation being functionally stable.
- As there is no place to be bent, the insertion of lag screw is quicker, easier and the reduction more accurate than when bone plates are used.
To evaluate these advantages,
We studied osteosynthesis of mandibular angle fracture with solitary lag-screw technique. Five patients with fracture mandibular angle were selected for osteosynthesis using lag-screw technique. All patients were males. Their ages were range from 20 years to 35 years. The cause of injury was assault in three cases, sports-related in one-case and industrial-related in the other case.
Patients presented to the hospital within 2-10 days of injury and the time from injury to treatment range from 4 th day to 14 th day.
Champy et al.  and Cawood  recommended that in achieving low rates of wound dehiscence and infection, osteosynthesis must be carried out within 12 h and 48 h after injury, respectively.
But Smith  had found that postoperative complications were comparable to osteosynthesis performed within 24 h even when treatment was performed 24 h after the injury. Our hospital being the referral one, surgery was performed even 1 week after trauma. No complications were observed regardless of time lapse between injury and treatment.
In our study, combined intraoral and transcutaneous incision was used. And extra-oral approach creates facial scar and has the possibility of injury to the marginal mandibular branch of the facial nerve.
Opinion differs regarding the retention or extraction of erupted or unerupted third molars in the line of fracture. While Rubin et al.  have found no significant difference between the two in the range of complications and retaining the tooth will only make it prone for complications.
Wagner et al.,  have emphasized open reduction of mandibular angle associated with teeth removed from fracture line produced the greatest incidence of complications. Niederdellmann and Shetty  recommended leaving teeth in the line of fracture of mandibular angle region unless they were grossly mobile or involved with the pathology and if necessary removing them later at the time of screw removal. They contend that the maintenance of teeth provides the broader surface area for adaptation of bone fragments. In our study, roots in the fracture line and tooth with abnormal mobility were extracted.
Research by Philips indicates that self-tapping screws are superior in thin bones, whereas in bones thicker than 3 mm pretapping provides superior axial force in the screw. Campbell,  reported a case of screw failure and attributed it to self-tapping screws and suggested to tap all screws when used in dense bones and when long screws are used. Pretapping screws of 2.7 mm diameter used in our study. Preoperative neurosensory disturbance was present in three of our cases. All were recovered within 1 month. The screw we have used is cortical screws which have threads along its entire length.
Except in one case, MMF was released immediately after the surgical procedure since MMF compromises nutritional status in the early postoperative period leading to loss of weight. Without MMF, the rate of recovery of normal jaw is greater and trismus is less. Sufficient stabilization of fracture segments is achieved even without postreduction MMF. Various authors too have suggested that MMF is not needed and Valentino et al. (1995), confirmed through his comparative study that supplemental MMF does not reduce complication rate.
In one of our cases, slight mobility of fractured fragment was noticed after lag-screw fixation. Hence, the patients were kept under IMF for 2 weeks. The failure may correlate with:
- Improper angulation of lag screw resulting in a screw that engages the bone just behind the lingual aspects of the third-molar area and anterior to the temporal crest. This bone is insufficient thickness and density to provide rigid fixation.
- Due to improper countersinking of the 2 mm drill guide will not fit properly into the 2.7 mm drill hole. And 2 mm drill hole will then be directed too far to the lingual engaging the bone of insufficient density for rigid fixation.
Schaaf et al. compared lag-screw with miniplate fixation for mandibular fractures. He observed that gaps between the fractured segments measured in panoramic radiographs differed significantly between the lag-screw (average 0.56 mm) group and the group using 1 miniplate (average 0.85 mm) and 2 miniplates (1.40 mm). He concluded that the miniplate fixation resulted in a wider fracture gap, especially in the region of the lower margin of the mandible and lag-screw fixation showed smaller fracture gaps compared with miniplate fixation. 
Goyal et al. compared the efficacy 2.0 mm titanium miniplate with 2.4 mm titanium lag-screw fixation for mandibular anterior fractures. He concluded that the mean postoperative radiographic distance between all fractured fragments were considerably more in case of miniplate group as compared to lag-screw group. 
It is widely established that lag-screw osteosynthesis in the management of mandibular fracture provides the maximum amount of fracture stabilization and compression utilizing a minimum amount of hardware in the shortest operative times. Yet, the major disadvantage of the lag-screw technique is that it is the most technique sensitive of all fixation modalities.
Shashidevi, et al. evaluated the efficacy of titanium lag-screw fixation for mandibular fractures. He concluded that it is too technique sensitive procedure, necessitating strict adherence to the principle of lag-screw placement and good knowledge about internal anatomy of the mandible. 
| Summary and conclusion|| |
There are various options available to treat a mandibular angle fracture, but the results are variable in each technique. The solitary fixation technique has a better outcome.
The following conclusions were drawn:
- Though the clinical sample was small and the postoperative follow-up was only 6 months, this technique produced good primary intraoperative anatomic alignment by applying intra-fragmentary compression.
- Single-lag-screw technique applied along the external oblique ridge provided sufficient stability for uneventful healing even in severely displaced mandibular angle fractures.
- Incidence of postoperative mal-occlusion was nil.
- Except in one case MMF was released immediately after surgical procedure. So, the patient had a much faster rate of recovery of mandibular fracture.
- External scar as in extra-oral technique is overcome by use of trocar and cannula.
- Technique can be performed under LA, patients who are unfit for GA can also benefit. It is also economical and affordable.
- More than 40 mm mouth opening was achieved in 6 months postoperatively.
- Incidences of complications were very low.
It can be concluded that solitary lag-screw fixation technique is an effective procedure in producing good treatment results for angle fractures of mandible, but is technique sensitive and requires surgical expertise.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6]