By the end of this lesson, you will be able to describe the classification of the different types of mandibular fractures, the clinical presentations, and how they are investigated prior to treatment.
Between 45-73% of patients with maxillofacial trauma may have a fractured mandible (1,2), with many causes. The aetiology of facial fractures were generally discussed in the previous lesson, so you should already have an idea of why mandibular fractures may occur. However, looking more closely at studies on the patterns of mandibular fractures, we can identify the key reasons for why mandibular fractures occur. Evidence from a retrospective study in a London teaching hospital suggests that up to 77% of mandibular fractures in males were due interpersonal violence, whilst 43% of these fractures in females were due to a fall (3).
Moreover, we should always try to get the full story when taking a history of the injury, as other studies suggest that violence is actually the number one cause of mandibular fractures in females (4,5). Therefore, the cause of mandibular fractures in females could be misrepresented. This could relate to a safeguarding issues, with violence and abuse being a challenging subject for a patient to discuss.
Other causes of mandibular fractures include road traffic accidents and sports-related injuries. It should be noted that the incidence of mandibular fractures is higher in males compared to females, and in those aged 20-29, for both genders (3).
The mandible is a V-shaped bone that articulates bilaterally with the temporal bone, forming the temporomandibular joint on both sides. You would have also noticed in your anatomy lessons that the mandible has a degree of bone thickness variation, where some parts of the mandible are ‘thicker’ than others. This has an impact on the biomechanical strength of the mandible, and can be related to the frequency of fractures at particular sites; though it is not the sole factor of fracture frequencies (6). The cross-sectional area of bone generally increases as you move anteriorly, and the total cross-sectional area of the body, parasymphysis and symphysis is significantly greater than the angle (6).
In addition, we shouldn't forget about the muscles around the mandible too! The muscles of mastication; masseter, temporalis, lateral and medial pterygoid muscles, all run from the skull and insert into different parts of the mandible. The suprahyoid muscles; geniohyoid, stylohyoid, mylohyoid and digastric muscles, originate from the hyoid bone. These muscles have a role in moving the mandible during mastication and speech, and, due to the tension within the muscle, can also displace bone fragments in different directions, creating unfavourable or favourable movement of the fracture.
It is always worth remembering that the location of the fracture will often reflect the aetiology. For example, most angle fractures occur due to interpersonal violence (7), whilst condylar fractures are commonly associated with road traffic accidents and falls (8).
The diagram below displays the basic classifications of the mandibular fracture patterns, along with the statistics, showing which types of fracture occur more commonly (3). You may find that these figures vary depending on where the study was conducted and the sample size.
As well as basing the classification on the location of the fracture, fractures can be distinguished on whether they are favourable or unfavourable. The fracture line direction and the musculature forces on the fracture fragments will determine this. These terms are often used for fractures of the body. In favourable fractures, the bony fragments are drawn together by the muscles, whereas in unfavourable fractures, the bony segments become displaced by the muscle forces due the muscles pulling the segments apart.
Muscles such as the masseter, temporalis, and medial pterygoid muscles will displace the posterior bony segment in the supero-medial direction. The mylohyoid and anterior belly of digastric can cause displacement of the segments in a postero-inferior direction. It is also worth mentioning that other factors such as the force of the blow and gravity can also have an impact on fragment displacement. It is important to understand the concept of favourable and unfavourable fractures, as this can have an influence on the choice of treatment provided.
When it comes to mandibular fractures, multiple fractures are more likely to occur than a single isolated fracture. Common combinations include fractures of the angle and contralateral parasymphysis (often caused by interpersonal violence), and fractures of the parasymphysis and contralateral condyle (3). By knowing this, you should always have in mind that when a patient presents with a condylar fracture for example, there is a chance that there may be another fracture elsewhere in the mandible.
Another example of combination fractures include the Guardsman fracture pattern, consisting of a symphyseal fracture along with bilateral fractures of the condyles. These has been shown to occur in 2% of patients with mandibular fractures, and the most common cause is a fall (3).
There are other patterns of bilateral fractures that can occur. Bilateral parasymphyseal fractures are of particular interest as they may cause airway obstruction. This is due to the corresponding loss of tongue muscle support, rendering the symphysis a free fragment that will retract posteriorly (15). Muscles such as the mylohyoid, digastric, geniohyoid, and genioglossus displace the bone fragments, of the symphyseal posteriorly (16)
Signs and symptoms of mandibular fractures include:
Firstly, you need to make sure an Airway, Breathing, Circulation, Disability, Exposure assessment has occurred. This was explored in the previous lesson. We would also want to find out if the patient lost consciousness at any point, in addition to ascertaining whether the patient has inhaled anything. It is also important to find out when the injury occurred, the means by which the trauma occurred and how it all happened. We previously spoke about how each of these questions are vital in building a picture of how the trauma occurred. Taking a thorough medical and social history is key, as this will give us an insight into any patient factors which may alter the management of the patient.
When assessing the mandible, the inferior and lateral borders of the mandible should be palpated extra-orally. Along with this, the TMJ should be examined, and any malocclusion which is due to the injury should also be noted (the patient can usually state if their bite has changed). As previously mentioned, changes in occlusion can be concurrent with step deformities along the occlusal plane. If you have identified a possible fracture site, this should be investigated further with bimanual palpation of the area. This is done by applying firm pressure over the mandible, anterior and posterior to the fracture to see if there is any mobility after the pressure has been applied.
We should also be looking for other fracture sites in the mandible as well as the rest of the face. Clinical features of the mid-face and orbital fractures will be covered in future lessons, but some key clinical signs of these may include nosebleeds, periorbital ecchymosis, diplopia and nerve damage.
Having conducted an appropriate examination, radiographic imaging is utilised to investigation fractures further. As for any suspected head and neck injuries, skull and cervical spine radiographs will be taken. CT scans can also be taken depending on the extent of the injury. More specifically for mandibular fractures, an orthopantomogram (OPG) and a postero-anterior (PA) mandible x-ray will usually provide enough information for a clear visualisation of the fractures. For traumatised teeth, intra-oral radiography (such as a periapical radiograph) may be adopted during the investigation phase.
The surgical management of facial fractures, including mandibular fractures, can be broken down into three steps:
We spoke about what reduction is in the first lesson of Oral & Maxillofacial Surgery, but just to remind you, reduction is the action by which the fragments of the fractured bone are brought into contact with each other. By doing this, the bone is able to heal via primary measures. It is vital to ensure that the reduction is anatomically accurate (19), and that the occlusion is restored. In terms of how it is done, there are two techniques; open and closed. Open reduction (OR) is the process by which the fracture is exposed with various incisions, allowing the fracture to be visualised before being manipulated back into the correct position (19). Closed reduction is manipulation of the fracture into position with no direct vision (19). There is debate over which technique is preferred; however, the evidence suggests that there is little evidence to support one method of reduction over the other (20)
There are various techniques by which we can immobilize and fixate the fracture following reduction. This is done to ensure that the fragments of the fractures are kept in their reduced position to allow for excellent healing of the bone.
Indirect fixation with intermaxillary fixation (IMF) can be used following closed reduction, but it is used more commonly intra-operatively to assist with open reduction (19). IMF is the system by which various wires, bars and screws can be used to bring the maxillary and mandibular teeth together, and keeping them in a secured position. This in turn brings the fractured segments of the mandible together. Eyelet wires are commonly used with intermaxillary wires in order to do this (19). With the main intra-operative drawbacks of IMF being operation time and the risk of needle-stick injuries, other IMF methods have been proposed. Capstan screws are intra-oral bone screws which can be placed on the mandible and maxilla, and wires can be placed around these screws. The use of the Capstan screws removes the risk of inoculation injuries from twisting and bending the metal wires, and they are easy to use. Gunning splints are produced by the maxillofacial lab for partially edentulous or fully edentulous patients that require IMF (19).
It is worth remembering that we can encounter any of these IMF components in the general practice, and may find that oral hygiene is difficult to maintain for these patients. As a result, we should assist these patients with their oral hygiene, and monitor their progress post-operatively
Internal fixation (IF), also known as osteosynthesis, is a method that uses plates and screws (shown in the image below) to fixate the fracture segments together. It is commonly used after open reduction (ORIF), and has become the gold standard of maxillofacial trauma surgery (19). The plates can be made of titanium due to its strength and biocompatible characteristics, or the plates can be made of other materials to allow for biodegradation. IMF is not needed post-operatively when internal fixation is used, as the plates running across the fracture line provide adequate rigidity. As a result of not needing IMF, the patient can maintain their oral hygiene following surgery. Internal fixation does have some drawbacks, which include their permanent placement as well as being palpable under the mucosa (19)
Transosseous wires are also worth a mention. They were used for internal fixation before plates were introduced, but they can still have a role. These stainless steel wires can also be used as a point of anchorage for the suspension of fragments to ensure they don't drop (19).
External fixation is rarely used nowadays. It will often be indicated in comminuted, heavily infected or pathological fractures with bone loss (19).
Regardless of what technique is being used to treat mandibular fractures, early intervention is key, as it reduces the risk of secondary infection, as well as producing better anatomical and functional outcomes (19).
When treating children and the elderly, it is worth remembering that bone is different in these age groups. Children with mandibular fractures should be treated as soon as possible, due to how fast the healing process takes place at this age. Furthermore, when choosing which components to be used, correctly sizing the plates and screws etc. is important to avoid damage to vitals structures such as blood vessels and nerves (19). Early mobilization is also advised to prevent complications such as ankylosis.
In elderly patients, fixation plates are to be placed above the periosteum, as this is where the majority of the blood supply arises; in particular, in an edentulous mandible. Furthermore, bone grafting should be considered if it can improve the chances of healing in the atrophic areas of an edentulous mandible.
Following surgery, it is vital that rehabilitation takes place. During this period, measures should be taken to prevent infection. This is usually done with a short course of antibiotics. A soft diet is advised to patients following surgery to ensure that healing isn't interrupted.
This lesson covered the main concepts regarding mandibular fractures that you may see on your OMFS placements. Please see references and third party reading if you wish to continue your studies in more depth.
General references:
Dimitroulis G, Avery BS. Maxillofacial Injuries: a synopsis of basic principles, diagnosis and management. Wright; 1994
Pigadas N, Oliver R. Common facial fractures: 2. Management. Dental Update 2006; 33: 413-420
Hupp JR, Ellis III E, Tucker MR. 2014. Contemporary Oral and Maxillofacial Surgery. 6th ed. Elsevier
In text references:
Dental Update - Role of the GDP - mandibular fractures
