Jeffrey C. Posnick, DMD, MD

Special Medical Considerations

For the adult who is more than 40 years old and who is considering orthognathic surgery, additional medical risk factors may include cardiovascular disease; the effects of obesity; smoking history and pulmonary function; the potential for deep vein thrombosis or pulmonary embolus; the effects of bisphosphonate medication on wound healing; and occult malignancy. As with teenagers and young adults, taking a thorough history, performing a review of the medical records, and completing a physical examination are essential. To clarify areas of concern in these patients, there should be emphasis placed on the need for a thorough clearance examination by a primary care physician; evaluations by other medical specialists; (e.g., cardiologist, pulmonologist); the completion of an electrocardiogram, chest radiography, and laboratory tests (e.g., chemistries, hematology, thyroid tests, coagulation tests); and other special studies (e.g., stress test, echocardiogram, sleep study, pulmonary function tests). Obtaining a hemoglobin A1C level and a serum or urine cotinine level are useful checks to address long-term diabetes effects and smoking compliance, respectively. The adult with a dentofacial deformity and an elevated body mass index is at risk for obstructive sleep apnea (OSA) and therefore more vulnerable to intraoperative and postoperative complications (see Chapter 26).

Functional Assessment of Head and Neck Structures

The orthognathic surgeon should evaluate the baseline head and neck functions of their patients, which include speech, swallowing, chewing, breathing, hearing, vision, cognition, and psychosocial competence (see Chapters 7 and 8). The documentation of cervical spine and temporomandibular joint (TMJ) baseline function and of any limitations in neck or mandibular range of motion is also essential (see Chapter 9). Each of these aspects may be negatively affected by the presenting maxillofacial malformations and influenced favorably or unfavorably by the treatment being contemplated. Baseline chronic obstructive nasal breathing as a result of septal deviation, enlarged inferior turbinates, or a tight nasal aperture should not be ignored (see Chapter 10).^{103,104,106,107} In the adult, weight gain with adipose hypertrophy within the upper airway in combination with hypotonia of the pharyngeal muscles in the presence of an uncorrected dentofacial deformity is likely to result in OSA. A formal attended polysomnogram, a complete upper airway evaluation, and a consultation with a sleep specialist are frequently indicated (see Chapter 26).

Temporomandibular Disorders: Effects of Orthodontics and Orthognathic Surgery

It is estimated that an average of 32% of the population report at least one symptom of temporomandibular disorder (TMD) and that an average of 55% demonstrate at least one clinical sign of such a condition.¹¹⁷ TMDs include various symptoms and signs of the TMJs, the masticatory muscles, and the related structures. The symptoms and signs may include a spectrum of referred head and neck discomforts; joint noise (e.g., popping, clicking, crepitus); reduced or altered mandibular movements as a result of muscle spasm or disc displacement with or without reduction; condylar head erosion; and pain on direct palpation of either TMJ or of the masticatory muscles.

The effects of orthodontics and orthognathic surgery on TMJ function for each specific adult patient cannot be fully predicted. Many clinical studies report improvement in TMJ symptoms and signs in a majority of individuals after successful orthodontics and orthognathic surgery, although some patients will deteriorate after the procedures. The favorable TMJ effects of orthognathic surgery often observed in patients with preoperative TMD may be the result of the improved occlusion, the restoration of normal facial height and jaw projection, or the reduced emotional stress. Adults with longstanding TMD should be cautioned that their pretreatment findings may not respond to occlusal correction and jaw-straightening surgery. Baseline TMD problems in the patient with a dentofacial may primarily be masticatory muscle disorders (i.e., myofascial conditions) or, less commonly, the result of joint pathology (i.e., internal derangement). These two problems may coexist, and the distinction in some individuals may be difficult. It is unlikely that the correction of an existing dentofacial deformity will correct either internal joint problems or other non-muscular sources of pain. Myofascial pain develops when muscles are fatigued, because they then tend to go into spasm. Myofascial pain generally occurs after clenching or grinding the teeth for many hours each day, presumably as a response to stress. It is also true that some types of occlusal discrepancies predispose the individual who clenches or grinds his or her teeth to TMD. A compelling argument against malocclusion as the primary cause of TMD is the observation that TMD is not more prevalent among individuals with malocclusion as compared with those with a more normal occlusion. Interestingly, for those individuals with myofascial pain, the orthodontic mechanics required as part of the orthognathic correction are often helpful. This is because orthodontic treatment makes the teeth sensitive, which tends to limit grinding and clenching. Therefore, when the parafunctional (i.e. clenching, grinding) activity stops, the myofascial pain is often diminished. The changing occlusal relationships during the orthodontic phase of treatment may also contribute to a break in the cycle that contributed to the initial muscle fatigue and pain. The cycle of clenching and grinding is also broken during the healing phase that takes place just after orthognathic surgery. Unfortunately, it is also recognized that, at some point after successful orthodontics and orthognathic surgery, the individual with a long history of myofascial TMD symptoms may return to the clenching and grinding parafunctional habits. The use of an intra-occlusal splint in this situation will often be the best way to break the cycle and keep symptoms at bay. For all of these reasons, the individual’s rationale for the correction of the jaw deformity and the associated malocclusion should not be solely based on a desire for the permanent relief of TMJ symptoms and signs (see Chapters 7 and 9).

Special Wound Healing Risk Factors

Special wound healing risk factors may include previous radiation therapy, diabetes mellitus, smoking or other forms of nicotine use, and past or current bisphosphonate treatment for osteoporosis. Diabetes mellitus, high blood pressure, hyperlipidemia, and OSA are frequent comorbidities of obesity that may complicate wound healing. A significant incidence of postoperative infections among diabetic patients undergoing maxillary or mandibular osteotomies has been reported, despite adequately controlled glucose levels. The inhalation of nicotine via cigarette smoke affects pulmonary function as well as tissue oxygenation and the healing of the surgical wounds. Smoking (nicotine ingestion) has been shown to delay the chondrogenic phase of bone (osteotomy) healing, thereby negatively affecting the circulation of elevated flaps and their healing after wound closure. It is known that bisphosphonate treatment for osteoporosis affects osteoclastic activity and may negatively affect bone healing (see Chapter 16).

Comprehensive Dental Rehabilitation

Recognizing when a patient who is seeking orthognathic surgery has additional dental needs beyond standard orthodontics is essential to the achievement of a favorable outcome (see Figs. 25-1 through 25-11