Craniofacial microsomia: management and outcomes. Part 2

Orbital involvement

The orbital size and position may be normal or with varying degrees of abnormality. The eyes may be affected with epibulbar dermoids (growth on the sclera) and necessitate ophthalmology involvement. If the facial nerve is affected, it is important to ensure adequate corneal lubrication owing to the risk of exposure keratitis of the cornea.

Orbital dystopia (orbits not on same horizontal plane) may be surgically corrected once orbital growth is complete, generally after the age of 4 years. This is usually reserved for cases with severe asymmetry. This may involve a circumferential box osteotomy, often combined with cranial surgery, if required. For patients who require orbital expansion, the use of balloons or orbital distraction may be necessary.

Ear

The severity of ear involvement may range from unaffected to anotia (absence of the outer ear with narrowing or absence of the ear canal), with malformations involving the external, middle or inner ear. Patients may have varying degrees of hypoplasia/absence of external auditory canal (aural atresia), external ear (auricle) or concha. Patients with CFM should undergo a hearing evaluation within the first 6 months of life, in addition to the newborn hearing screen. Hearing impairments may be conductive or sensorineural. Conductive hearing impairments occur when sound cannot adequately reach in the inner ear, due to hypoplastic or absent ossicles or aural atresia. Hearing aids or bone-anchored hearing aids (BAHA) are effective in these patients. A CT scan can help indicate whether there is likely to be an improvement in hearing following atresial repair. Sensorineural hearing loss is seen less commonly, with one study indicating that 10% of CFM patients are affected, in comparison to 86% with conductive hearing loss.⁵ Sensorineural hearing loss is due to abnormalities in the inner ear or cochlea or with the vestibulocochlear nerve.

Ear reshaping or reconstruction is managed on an individual patient basis. Removal of ear remnants and pre-auricular tags may be carried out at an early stage. Patients with more pronounced involvement of the ear might require a prosthesis or reconstruction, using autologous or synthetic materials. Autologous reconstruction is generally carried out as a two-stage procedure (Figure 1). Rib cartilage is harvested once the patient has reached a sufficient chest circumference, generally from age 10 years onwards. It is important to consider the aesthetic implications of any future jaw surgery when planning the final ear position.

Nerve involvement

CFM may affect the trigeminal, facial and hypoglossal nerves, with a wide variety of nerve presentations. It is thought that dysmorphogenesis of the temporal bone and the resulting effects on the facial nerve are the cause of facial weakness; however, this has not been conclusively determined, with uncertainty still present over whether there is facial nerve dysfunction or facial muscle weakness.⁶ Facial reanimation may be considered in addition to functional muscle transfer or a muscular free flap. Ideally these procedures are performed following any craniofacial, ear or orthognathic surgery.

Soft tissue

The soft tissue deficiency is graded using the OMENS classification from 0–3, ranging from no obvious deficiency up to severe tissue hypoplasia. This may affect the musculature, skin and subcutaneous fat. In addition, the presence of a facial cleft or macrostomia (enlargement of the mouth at the oral commissures) will lead to a tissue deficit. Macrostomia repair and facial tag removal is generally carried out within the first year. It is preferable to delay other soft tissue procedures until after definitive bony reconstructive surgery or orthognathic surgery, such that the final bone framework and support for the soft tissue is established. Microvascular free flap surgery can be used to increase soft tissue bulk, although this is not frequently carried out. Adipofascial free flaps can provide a large amount of soft tissue in a single surgery.⁷ Donor sites may include free groin, anterolateral thigh or medial sural artery perforator.⁸

If the patient has aesthetic facial concerns prior to definitive skeletal surgery, then autologous fat transfer may be a solution to camouflage the facial tissue deficit and asymmetry.⁹ This procedure may require repeating due to a tendency for resorption of some of the grafting fat tissue; however, it provides a useful, less-invasive alternative to microvascular free tissue transfer.¹⁰

For patients presenting with a mild soft tissue deficit, consideration could be given to a mandibular body augmentation using a porous polyethylene (PPE) implant, instead of an autograft.

General dental management

Patients require close dental monitoring and robust preventive care. Patients may be at risk of caries if mouth opening and access for cleaning is restricted. Patients who are fed by gastrostomy may have limited oral intake, but will still require dental monitoring to ensure oral hygiene remains satisfactory and calculus deposits removed. It may be necessary to undertake dental treatment when undergoing general anaesthesia for other procedures, such as ear reconstruction.

Mandible

Management of the mandible varies considerably between patients and even between treatment centres. Therefore, surgical and orthodontic involvement is tailored to the specific needs of each patient and depends on the age, skeletal maturity of the patient and severity of deformity.

The majority of surgical correction is carried out after growth has completed. There are instances where surgery before completion of growth may be indicated, such as to minimize secondary deformities due to restricted growth of adjacent structures, or for aesthetic or functional concerns.

The four treatment objectives proposed by Kaban et al¹¹ are useful foundations from which to consider surgical and orthodontic correction:

Type IIb and III

Patients with Type IIb and III classifications have more pronounced mandibular involvement and often require a multi-staged treatment approach, involving a series of surgical procedures as the patient grows.¹⁸ These patients have a non-functional or absent TMJ, so the use of a functional appliance is not appropriate. Patients in these categories will require reconstruction of the ramus and TMJ. A costochondral graft (CCG) has been the preferred approach in growing patients (Figure 6). It facilitates mandibular reconstruction and, due to its inherent growth potential, it has the ability to grow as the patient grows. Research and clinical practice indicate that this is not always borne out, however, with unpredictable graft growth.^17,19 They can overgrow, grow too little or exhibit no useful growth. In addition, ankylosis at the TMJ area may occur.

Lengthening the mandible by placing a CCG will lead to an open bite, which can be used to help prevent secondary maxillary canting if eruption guidance is used during the mixed dentition.^11,19 A removable or fixed bite plane is used to encourage eruption of the teeth in a controlled manner to resolve a maxillary cant or prevent the formation of one (Figure 2). Once the permanent teeth have erupted, it is more difficult to level the occlusal plane using eruption, as dental extrusion would be unstable.

Early distraction osteogenesis (age 5–12 years, before the permanent dentition is established and before skeletal maturity) was a common treatment modality for hard and soft tissue enhancement. In cases with mandibular Type IIb and III, distraction osteogenesis provides the ability to stretch the soft tissue, facilitating later surgery. However, distracting a severely hypoplastic mandibular proximal segment can be problematic due to the lack of a stable posterior joint to act as a foundation for the movement. In addition, evidence that this procedure is stable is somewhat lacking with research now showing that there is no significant long-term advantage to early vertical mandible distraction.^16,17,20,21 It also will not correct canting of the occlusal plane, nor achieve three-dimensional facial and occlusal asymmetry and thus, a bimaxillary osteotomy is often still required.²¹ It is now considered that early distraction osteogenesis may be no more beneficial than reconstruction of the TMJ joint with a graft and adjunctive soft tissue procedures.² In addition, conventional orthognathic surgery is more predictable than distraction osteogenesis, once adequate bone levels are available. It is also not reliant on patient compliance and produces no visible scarring. However, for patients with no maxillary compensatory cant, who require unilateral mandibular lengthening, distraction can offer a favourable outcome (Figure 7).

Orthognathic surgery and a prosthetic joint replacement are carried out towards the end of the adolescent growth phase. A bimaxillary osteotomy is required if a maxillary cant is present. Wolford describes the use of a bimaxillary osteotomy with mandibular advancement with a patient-fitted total joint prosthesis on the affected side and contralateral ramus bilateral sagittal split osteotomy in an anticlockwise direction.²² 3D planning can help to determine extent of osteotomy movement and vectors, and ensure that there is a custom-made joint to fit.²³

A prosthetic TMJ is a predictable solution in the non-growing patient for long-term management (Figure 8). Their use is not recommended in growing patients because they do not adapt to facial growth. However, similar to other joint prosthesis, the lifespan of a replacement TMJ joint is finite and thus, the patient and family must be counselled accordingly (Table 2).

A systematic review found that patients with mandible Types IIa, IIb and III had commonly undergone previous procedures (distraction osteogenesis, CCG, tibia graft, sternoclavicular graft), whereas those with Type I often just had one surgical procedure for asymmetry correction.²⁴ Van de Lande et al concluded that it is preferable to delay mandibular reconstruction until at least the permanent dentition is established, or ideally skeletal maturity achieved, once there are no functional or psychological problems.²⁴ This is in agreement with a 2014 systematic review¹⁸ and a review by Mommaerts and Nagi.¹⁶

Successful outcomes are linked with the severity of the case, with Type I and IIa showing minimal relapse and minimal increase in asymmetry.¹⁸

Adjunctive procedures

Following definitive hard tissue surgery, consideration may be given to carrying out adjunctive soft tissue procedures to improve facial balance and symmetry. This may include fat transfer grafting, malar implants, rhinoplasty, genioplasty and nerve reanimation. Patient opinion and case severity will dictate the requirement for any additional procedures.

Dental

Restoration of the dental occlusion may be required once hard tissue surgery is complete. Mild cases of CFM may achieve a favourable post-operative occlusal result and require minimal post-operative orthodontic treatment. Regular post-orthognathic orthodontic management may suffice. When using orthodontic elastics to improve occlusal setting, care must be taken to prevent relapse especially if a CCG is present instead of a solid functioning TMJ.

More complex cases of CFM may require intervention from a restorative dental team, to facilitate replacement of the missing dental units (Figure 4). Adjunctive alveolar bone grafting may be necessary to enable dental implant replacement of the posterior dentition, if absent (Figure 5). Consideration may be given to the use of zygomatic implants should the alveolar bone supply be insufficient.