20 Maxillofacial surgery

The mandible is one of the most frequently fractured bones of the face (Fig. 20.1). Fractures of the mandible are most common in young males and are frequently the result of interpersonal violence. Sporting accidents and motor vehicle accidents are other common causes.

Fractures of the mandible may also be the result of underling bony pathology of the mandible such as large jaw cysts or tumours that weaken the bone structure thereby predisposing to fracture. These are referred to as ‘pathological’ fractures.

The mandible can be likened to a ring structure (much like the pelvis) and therefore more than one fracture is commonly present.

Treatment consists of open reduction and internal fixation of fractures with titanium mini-plates usually via an intraoral approach. A small incision (<1cm) through the cheek may be required to facilitate this. Occasionally in the case of comminuted fractures, or pathological fractures, an extraoral approach with subsequent reconstruction achieved using larger and stronger plates may be required.

The procedure involves the placement of screws, buttons, or archbars so that the patient's occlusion (bite) may be restored using inter-maxillary wiring. The fracture sites are then exposed and the fractures reduced and fixed with bone plates. The incisions are closed using absorbable sutures.

Postoperatively the patient will need to maintain immaculate oral hygiene, keep to a very soft diet and refrain from smoking. Postoperative radiographs are usually required to ascertain the adequacy of the reduction and position of the plates.¹

The zygoma is the most commonly fractured facial bone, usually as a result of interpersonal violence. Sporting accidents and motor vehicle accidents are also common causes. The left side is more commonly fractured than the right.

The zygoma forms the prominence of the cheek, part of the lateral wall, and floor of the orbit and parts of the temporal and infratemporal fossae. It articulates with the frontal, sphenoid and temporal bones, and the maxilla. Fractures may disrupt any combination of these articulations (Fig. 20.2) and the treatment required will vary according to the pattern of fracture.

Treatment usually consists of open reduction and internal fixation via either a single or combination of approaches. Most commonly the fractured zygoma is approached intraorally via an incision within the upper buccal sulcus and the zygoma is elevated and plated with titanium mini-plates. However, incisions may be required in the region of the fronto-zygomatic suture, the lower eyelid, and the temporal hairline in order to fully reduce and fix the fractures.¹

Postoperatively, regular eye observations will be required and the patient is advised not to blow their nose. The patient will need to avoid contact sports and further trauma to the area and maintain good oral hygiene. Postoperative radiographs are usually required to establish the adequacy of the reduction. Skin sutures will need to be removed at follow-up.

Teeth may need to be extracted for a number of reasons. The most common causes are dental caries (decay) and periodontal (gum) disease. Lower third molars or wisdom teeth are frequently impacted and may become symptomatic necessitating extraction.

Each group of teeth requires its own technique for extraction and the risks of the procedure depend on the position of the tooth, the tooth morphology and the position of adjacent structures. Structures to be aware of include adjacent teeth, the mandibular branch of the trigeminal nerve (inferior dental nerve), including where it exits the mandible through the mental foramen, the lingual nerve, and the maxillary antrum.¹

Lower third molar extraction carries the highest risk of damage to the inferior dental and lingual nerves, and patients should be specifically counselled about the risk of damage to them. Damage to the inferior dental nerve may result in temporary or permanent numbness to the ipsilateral lower lip and chin; damage to the lingual nerve may result in temporary or permanent numbness of the ipsilateral anterior two-thirds of the tongue.²

The upper molars may be intimately related to the floor of the maxillary antrum and occasionally their removal may result in the formation of a communication between the mouth and antrum, i.e. an oro-antral fistula This may close spontaneously, if small or require a formal procedure to close.

Direct blows to the globe may result in fractures to the delicate bones of the walls or floor of the orbit as the force is dissipated. This may lead to an increased orbital volume.

Clinical features of such injuries include enophthalmos and restriction of eye movements with associated diplopia, as the orbital contents herniate through the fracture and may become trapped. Hypoaesthesia in the distribution of the infraorbital nerve may also result if the fracture involves the infraorbital canal, thereby damaging the infraorbital nerve. Formal ophthalmological and orthoptic assessment are required prior to surgery.

The orbital floor may be accessed through a subciliary or blepharoplasty incision in the lower eyelid or via a transconjunctival approach. The orbital contents are retrieved from the fracture and the orbital floor reconstructed using either autologous (bone) or alloplastic (titanium mesh) materials.¹

Postoperatively the patient will require regular eye observations, as for a fractured zygoma and is advised to refrain from nose blowing. It may take some weeks for the oedema to settle and for ocular function to return to normal.

The zygomatic arch consists of the zygomatic process of the temporal bone and the temporal process of the zygomatic bone. It may be fractured in isolation by a direct blow. There is characteristically a dimple evident in the region when the swelling subsides. There may also be associated limitation of mouth opening due to the depressed arch impinging on the coronoid process of the mandible.

The temporalis fascia attaches to the upper border of the arch whereas the temporalis muscle itself attaches to the coronoid process of the mandible. It is this anatomical arrangement that facilitates the surgical elevation of a fractured arch. Surgical elevation is achieved through a temporal hairline incision and dissection made down to the temporalis fascia. This fascia is then incised and an elevator inserted down between the fascia (Fig. 20.3) and the muscle extending beneath the zygomatic arch. The fracture can then be elevated and reduced.¹

Postoperative radiographs are usually required to ascertain the adequacy of the reduction. The patient should be advised to sleep on the contralateral side and to avoid contact sports for 6 weeks.

The bilateral sagittal split mandibular osteotomy may be used to correct mandibular prognathism, retrognathism, or asymmetry. It may be a single jaw procedure or as part of a bimaxillary procedure in conjunction with a Le Fort 1 osteotomy. The patient will usually undergo a course of orthodontic treatment prior to surgery to facilitate maximum accuracy of the procedure and optimization of their occlusion (bite).

The procedure is undertaken through an intraoral approach. Mucoperiosteal flaps are raised and a series of bone cuts made in the sagittal plane. The mandible is then split on either side. The free distal portion is repositioned into an appropriate occlusion using a prefabricated splint, the jaws wired together, and the osteotomized fracture sites fixed with titanium mini-plates or screws. Small incisions (<1cm) may be required on either cheek to facilitate this. Closure is with resorbable sutures.

Postoperative radiographs are taken and the patient may need to wear intermaxillary elastic bands. A further period of orthodontics is usually required.

An alternative approach may be considered for patients with isolated mandibular prognathism. The vertical subsigmoid mandibular osteotomy involves bone cuts made vertically to section the ramus of the mandible from the sigmoid notch down to its inferior border. The body of the mandible is then repositioned posteriorly with the fragments now overlapping. A major disadvantage of this procedure is that a 4–6-week period of rigid intermaxillary fixation is required.

The Le Fort 1 maxillary osteotomy is a procedure whereby the maxilla is separated from the skull base so that it may be repositioned in order to correct an underlying skeletal deformity. It may be a single-jaw procedure or as part of a bimaxillary procedure in conjunction with a mandibular osteotomy. The patient will usually undergo a course of orthodontic treatment prior to surgery to facilitate maximum accuracy of the procedure and optimization of their occlusion (bite).

The procedure is undertaken through an intraoral approach. An incision is made in the upper buccal sulcus and cuts made through the lateral, medial, and posterior maxillary walls. The maxilla is then dis-impacted (Fig. 20.4) and repositioned into an appropriate position using a prefabricated splint, the jaws are wired together, and the fracture sites fixed with titanium mini-plates. Closure is with absorbable sutures.

Postoperatively, radiographs are taken, and the patient may need to wear intermaxillary elastic bands. A further period of orthodontic treatment is usually required.

A cyst is a pathological cavity, usually lined by epithelium and filled with fluid, semifluid, or gaseous material. They can vary in size from the very small to involving the majority of one or both jaw bones. They may be developmental or inflammatory, odontogenic or non-odontogenic in origin. Patients may be asymptomatic and the cyst found incidentally on routine radiographs or they may occasionally present with swelling of the jaw, with pain and discharge if the cyst has become infected.¹

The treatment required depends on the histological subtype. The majority of cysts respond well to simple enucleation. A mucoperiosteal flap is raised intraorally, and the cyst accessed through the bone and removed in its entirety. The specimen is then sent for histological analysis. Large cysts may significantly weaken the bone and fracture of the mandible, either at the time of surgery or during the recovery period is a recognized complication. Large mandibular cysts may also envelop the inferior dental nerve as it passes through the mandible and therefore the patient must be counselled about the possibility of damage to the nerve at time of surgery.²

Dental decay can allow ingress of bacteria into the pulp of a tooth and from there into the surrounding alveolar bone, resulting in a localized infection. This infection can spread, usually along the path of least resistance into the surrounding tissues. This path of spread is influenced by the position of the tooth and the position of surrounding structures, for example muscle attachments. In simple cases, resolution may be achieved by commencing root canal therapy or extracting the affected tooth. However, if left untreated such infections can progress to become very serious and in some cases life-threatening.

The procedure undertaken depends on the tissue spaces involved, whether there is a collection of pus that can be drained and the severity of the infection. For maxillary teeth, extraction of the culprit tooth, with or without intraoral incision and drainage is usually sufficient. Infections associated with mandibular teeth commonly spread into the submandibular space (i.e. beneath the attachment of mylohyoid) and will therefore require incision and drainage via an extraoral submandibular incision. This approach will leave a scar on the neck and the patient should be warned about potential damage to the marginal mandibular branch of the facial nerve.¹

A plastic corrugated drain is usually left in situ for 24–48h postoperatively.

The submandibular gland is most often removed due to recurrent infections or sialadenitis. This is usually due to obstruction of the submandibular duct by a stone or stricture. The greater the number of episodes, the more damage is done to the gland and surrounding tissues. Patients may report repeated episodes of pain and swelling from the gland. In some cases of obstruction, the gland may swell every time the patient eats as the saliva produced is unable to pass down the duct into the mouth—this is known as ‘mealtime syndrome’.¹

Neoplasms may also develop in any of the salivary glands; they may be benign or malignant. Malignancies are more common than benign lesions in the submandibular glands.

The gland is accessed by an incision in the neck below the border of the mandible, care being taken to protect the marginal mandibular branch of the facial nerve. The lingual nerve is identified and protected and the gland dissected out from the surrounding structures (Fig. 20.5). The submandibular duct is tied off and the gland excised and sent for histopathological examination.

A drain is placed to prevent haematoma formation and the wound closed in layers, usually with absorbable sutures. The drain can usually be removed the following day and the patient discharged.

If a stone in the submandibular duct is responsible for the obstruction, then in some cases it may be amenable to removal, either endoscopically or surgically through an intraoral incision into the duct. This may provide resolution of the symptoms but often removal of the gland at a later date is required.

The parotid glands lie anterior and inferior to the ear over the ramus of the mandible. It can be considered to have both a superficial and a deep component, divided by the course of the facial nerve. The facial nerve, after exiting the skull base through the stylomastoid foramen enters the gland and divides into its five main branches (Fig. 20.6). The most common reason for undergoing a superficial parotidectomy is due to the development of a neoplasm within the gland, the commonest being the benign pleomorphic adenoma. Primary or secondary malignancies may also develop within the gland.

The procedure involves making a preauricular or postauricular incision and the raising of a skin flap. Dissection is then made to identify the main trunk of the facial nerve and the main branches are identified. The superficial lobe of the parotid containing the lesion can then be dissected out. A nerve stimulator is often used to facilitate this. If the resulting defect is large, a sternomastoid flap may be raised to fill the defect resulting in a better cosmetic result. A drain is placed to prevent haematoma formation. This is usually removed the following day.

Following the procedure, the patient may have ipsilateral facial weakness due to damage to the facial nerve, numbness over the ear lobe due to damage to the greater auricular nerve, and may develop a salivary collection or fistula. A syndrome known as gustatory sweating or Frey's syndrome may develop, where the patient's skin overlying the parotid sweats excessively at mealtimes. This is due to inappropriate regeneration of parasympathetic nerve fibres that, instead of innervating salivary tissue, now innervate the sweat glands of the skin.¹

The frontal sinuses lie within the frontal bone, varying considerably in size. Pneumatization progresses throughout childhood with the sinuses becoming fully developed in young adults. Occasionally one or both may be congenitally absent. The anterior wall of the sinus is formed by the anterior lamella of the frontal bone and is capable of withstanding substantial forces. The posterior wall, however, is a much thinner and the fragile structure intimately related to the dura. The floor of the sinus forms the orbital roof.

Due to the inherent strength of the anterior sinus wall considerable localized force is required to fracture it. Motor vehicle accidents and interpersonal violence account for the majority of cases. Due to the energies involved, there are commonly other maxillofacial and neurological injuries present and a thorough assessment is required. Signs that may be suggestive of a frontal sinus fracture include frontal bruising and swelling and an obvious depression or laceration over the region of the sinus.

If a frontal sinus fracture is suspected, imaging should be requested. Plain films can be of some use but CT is the imaging modality of choice. It gives an accurate axial view allowing assessment of the anterior and posterior table of the frontal sinus and additionally the presence of any intracranial injuries. Frontal sinus fractures may be treated conservatively or operatively. Isolated anterior table fractures with minimal displacement or cosmetic defect may be best treated conservatively, whereas fractures involving both anterior and posterior tables are usually managed operatively.¹

The most common approach is via a bicoronal incision made behind the hairline; a subgaleal flap is raised and the fractures exposed. If there are overlying lacerations then these may be used for access.

Isolated anterior wall fractures may simply have the bone fragments repositioned and fixed with titanium mini-plates, whereas fractures involving the posterior wall may require either obliteration or cranialization of the frontal sinus in order to minimize the risk of potential infection. Vacuum drains are usually placed, the incision closed, and a tight fitting head dressing applied.²

Cranioplasty is the surgical repair of a skull defect or deformity that often results from previous neurosurgery such as decompressive craniectomy or from trauma to the cranium. There is usually a significant time period between the initial surgery and cranioplasty repair. Many materials can be used for cranioplasty including bone and polymethyl-methacrylate. Custom-made titanium implants are widely used in the UK.

A CT scan of the defect is performed and a life size model produced using a computer-controlled mill. This allows for the fabrication of the implant prior to surgery. The placement of the implant is relatively straightforward. A scalp flap is raised, often using the scar from previous surgery, the defect fully exposed and the implant positioned appropriately. The implant is then secured with titanium bone screws. A vacuum drain is placed and the flap replaced. A tight fitting head bandage is placed to prevent the development of a seroma.

The cranioplasty restores the contour of the skull and provides physical protection to the intracranial structures. There is evidence emerging that the placement of a cranioplasty may also lead to an improvement in neurological function, perhaps by reducing atmospheric pressure on the brain and increasing cerebral blood flow in the area. There is, however, no way of predicting which patients will show an improvement in neurological function following surgery.¹

The temporomandibular joint forms the articulation between the condyle of the mandible and the glenoid fossa of the temporal bone of the skull. It is a synovial joint with a fibrocartilaginous articular disc dividing the joint into two compartments. The joint is capable of two types of movement. Initial mouth opening is a rotational movement of the condylar head against the articular disc, within the inferior joint compartment. Further opening leads to a translatory movement of the articular cartilage and condylar head around the glenoid fossa.

The temporomandibular joint can be affected by many different pathologies, the most common of which is temporomandibular joint dysfunction. This has a wide range of symptoms and presentations but generally involves one or more parts of the temporomandibular joint apparatus. Patients may complain of pain in or around the joint, reduced or painful mouth opening and a clicking or grinding sensation on mandibular movement. These symptoms may be constant or intermittent and are typically worse at certain times of day, typically in the morning.

The aetiology of such dysfunction is complex and many hypotheses have been suggested. There is often an associated psychological component. Due its multifactorial aetiology, a multidisciplinary team approach to temporomandibular joint dysfunction should be employed. The majority of patients can be managed non-operatively.

The least invasive of surgical temporomandibular joint procedures is arthroscopy. A small arthroscope can be introduced into the joint space allowing the joint to be visualized and any pathology such as adhesions, disc displacement, or perforation to be identified. In some cases, therapeutic procedures can be performed such as the lysis of adhesions and meniscopexy. This can remove the need to have open exploratory temporomandibular joint surgery with its associated risks.

Temporomandibular joint arthroplasty describes any open procedure of the temporomandibular joint. There are a variety of procedures that can be performed. They include disc reposition, discectomy, recontouring of the articular eminence, and total joint replacement.

The temporomandibular joint is accessed via a preauricular incision, a skin flap is raised and dissection continued down to the joint capsule. The capsule is opened to expose the joint itself allowing further assessment of the joint and full surgical access to it.

If the articular disc has been displaced it may be relocated into its appropriate position and sutured in place. If it has been too badly damaged it is sometimes necessary to remove it—discectomy. Synthetic or autologous materials can be used to re-create the disc or the space left empty for scar tissue to fill.

If the temporomandibular joint is not suitable for such procedures or they have been unsuccessfully attempted in the past, then a partial or total joint replacement may be indicated. Replacement temporomandibular joints consist of two components, a fossa component that reproduces the glenoid fossa and a mandibular component that replaces the mandibular condyle. Two incisions are required, one preauricular and one retromandibular, to gain sufficient access. The condylar head is excised and the glenoid fossa prepared. The patient is then put into rigid inter-maxillary fixation before the implants are placed and secured. A drain is rarely used due to the risk of introducing infection and the wounds are closed.

Open temporomandibular joint procedures are not without risk and should not be undertaken lightly. They are often a last resort for intractable joint pathology.

Specific risks include damage to the facial nerve, especially the temporal and zygomatic branches. The middle ear can also be damaged with associated loss of hearing. While such procedures are undertaken with the intention of improving the patient's symptoms, the patient must be specifically warned about failure of the procedure and that such procedures may cause a worsening of their symptoms.