Effectiveness of maxillo-mandibular advancement in obstructive sleep apnea patients with and without skeletal anomalies

Article Outline

• Abstract
• Materials and methods
• Results
• Discussion
• Funding
• Competing interests
• Ethical approval
• References
• Copyright

Abstract 

This study evaluates the effectiveness of maxillo-mandibular advancement (MMA) in patients with obstructive sleep apnea syndrome (OSAS), even those without skeletal anomalies, indicating the possibility of extending this procedure to more patients. Two groups with different skeletal patterns were studied pre- and post-surgery. Group 1 (11 patients) had severe or moderate OSAS and maxillo-mandibular hypoplasia and/or mandibular deformities (SNA angle 78° or less or SNA angle>78° but with SNB<65° and severe skeletal class II malocclusion). Group 2 (11 patients) had severe or moderate OSAS without maxillo-mandibular hypoplasia or deformity (SNA angle>80°, dental class I occlusion). Analysis comprised: apnea hypopnea index (AHI), posterior airway space (PAS), SNA and SNB angles, Epworth sleepiness scale (ESS), body mass index (BMI), and a subjective standardized questionnaire about aesthetic appearance. All patients had increased PAS width and complete remission of objective and subjective OSAS symptoms evaluated by AHI and ESS. Results in both groups are comparable. Data were analysed using t-test; p<0.005 was statistically significant. All patients were satisfied with the functional and aesthetic results. MMA is effective in patients with severe or moderate OSAS, even in those without skeletal and/or occlusal anomalies and can be considered in more patients.

Keywords: OSAS, maxillo-mandibular advancement

The primary goal of the surgical approach to severe cases of obstructive sleep apnea syndrome (OSAS) is to resolve or significantly improve the clinical situation, thus avoiding the use of nasal-continuous positive airway pressure (N-CPAP), which is frequently badly tolerated or refused. About 50% of patients in the USA and 25% in Europe have poor compliance with ventilatory therapy¹⁵.

Surgical techniques involving the soft tissues, such as uvulopalatopharyngoplasty⁵, hyoid suspension²⁰, partial glossectomy²⁴ and lingual suspension¹⁴ have given partial results, mainly in cases of medium to light severity¹, ¹⁸. The only technique that has given good results, including in obese patients, is resection of the base of the tongue with hyoidoepiglottoplasty³ but it has a high incidence of intra-operative and postoperative complications and sequelae.

Surgical methods involving skeletal components of the oro-maxillo-facial area have gained ground. Initially, mandibular advancement alone was employed¹⁶, followed by anterior-inferior mandibular osteotomy⁷ and, more recently, maxillo-mandibular advancement (MMA) surgery has been employed⁶, ¹³, ¹⁷, ¹⁹. With MMA, all the soft-tissue structures making up the pharyngeal walls are tightened at once; this stops them from collapsing, or reduces this occurrence, by acting on the suprahyoid and palatal muscles and on the lateral musculature of the pharynx. The tongue is also pulled forward. The result is a significant increase of posterior airway space (PAS) and the resolution of the syndrome in a high (95%) percentage of cases.

At first, MMA was suggested for patients with clinical and cephalometric patterns of mandible and maxilla retrusion, and in a second stage of treatment, after nasal or palatal surgery without significant improvement⁸, ¹⁹. Later studies recommended the use of MMA as the first surgical choice in patients with severe OSAS and cranio-facial anomalies⁶, ¹³, ¹⁷.

Although it is logical to advance both jaws in patients with clinical and/or cephalometric evidence of maxillo-mandibular hypoplasia or retrusion, the possibility of extending indications to include other types of patients remains unclear, and few studies have been published⁹.

Regarding the maxilla, a wide advancement beyond the traditional cephalometric values could compromise the facial aesthetic. This retrospective study evaluates the results obtained in two groups of patients with abnormal or normal facial patterns, through MMA surgery. The results are discussed and compared with reports in the literature, in particular the indications and motivations for this treatment.

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Materials and methods 

Between January 2003 and November 2007, a retrospective study of two groups of patients affected by severe or moderate OSAS, with different skeletal patterns, and treated by MMA was carried out. Group I included 11 patients with known severe or moderate OSAS, who had been undergoing treatment with N-CPAP for some time but had not tolerated it well, and who had clinical and cephalometric evidence of dento-facial anomalies (Table 1): SNA angle 78° or less or SNA>78°, but with SNB angle<65° and severe mandibular deformity with skeletal class II malocclusion. Group II included 11 patients with known severe or moderate OSAS, who had been undergoing treatment with N-CPAP for some time but had not tolerated it well, but who had cephalometric, occlusal and aesthetic characteristics within the normal range (Table 2): SNA angle>80° and class I occlusion. Other inclusion criteria were: apnea hypopnea index (AHI)>20, and Epworth sleepiness scale (ESS)>10 in both groups.

Table 1. Analytical results for group I.

Table 2. Analytical results for group II.

MMA was performed in all patients, to produce mandibular advancement, measured at the incisal margin of the mandibular incisors, of at least 10mm. In group I, preoperative orthodontic treatment was performed in 8 patients; appropriate partial removable prostheses were prepared for three partially edentulous patients, to achieve a better occlusal stability in post surgery. The initial class I occlusion was maintained unaltered in all patients in group II. In 18 patients (9 in each group) associated advancement genioplasty was performed, following the technique described by Prinsell¹⁷ (Fig. 1a and b).

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• Fig. 1. 

  (a and b) Diagram showing the patterns of MMA and genioplasty.

Septoplasty was carried out in 15 patients (8 in group I and 7 in group II) and reduction of the inferior turbinates in 4 (2 in each group). In 2 patients in group II, in whom the osteotomy gap at the maxilla was particularly wide, a graft of cortico-cancellous bone, harvested from the iliac crest, was utilized (Table 3).

Table 3. Adjunctive surgical procedures.

In all cases, fixation was achieved using microplates at the maxilla and miniplates with monocortical screws at the mandible. Maxillo-mandibular fixation was not used in any cases. In group II patients, careful remodelling of the anterior nasal spine and pyriform area was used to avoid excessive protrusion of cheeks and/or lips. For the same reason, a meticulous alar cinch suture was performed, but not a VY closure of the vestibular mucosa, a linear closure was preferred. It is known that advancement of superior labrale can change from 60% to 90% in relation with the skeletal advancement of the maxilla, depending on soft tissue management and VY closure of the mucosa². The use of N-CPAP was abandoned from day 1 post-surgery.

Clinical and instrumental examination, by polysomnography, lateral cephalogram and helical CT, in selected cases, was carried out before surgery, immediately post-surgery (8–10 days) and at follow-up between 4 and 27 months after surgery. The indexes evaluated were: PAS (on cephalometric tracing), SNA and SNB angles, AHI, daytime sleepiness using ESS, and body mass index (BMI). Data were analysed using Student's t-test, considering p<0.005 as statistically significant.

In some cases, a 3D volumetric evaluation of the posterior airways was performed using a helical CT scan. Recent studies have demonstrated the effectiveness of this technique to evaluate the antero-posterior and lateral dimension of the airways space⁴. These dimensions show a wide range of linear and volumetric measurement in different patients, so it is difficult to define a mean minimum value, but a percentage increase in an individual patient is very significant. This procedure has recently become popular²², ²⁵, but is limited to selected cases because of its high cost and the amount of radiation. In the present cases, the authors measured the total volume of PAS between two horizontal planes (superior limit of hard palate and apex of epiglottis), pre- and postoperatively. The authors consider that PAS evaluation on the lateral cephalogram is valid, both from a clinical and statistical point of view, for a study with a fairly large number of patients.

The patient's subjective experiences were evaluated using a standardized questionnaire. They were asked to evaluate and judge their profile and their aesthetic appearance before and after surgery, with four different degrees of judgement: unchanged (a), slightly improved (b), very improved (c), worse (d). Finally, they were asked to judge their overall satisfaction with the treatment outcomes, and whether they would recommend the same treatment to other patients.

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Results 

In group I (Table 1) an increase in PAS was recorded, with the mean value rising from 4.4 (SD 2.3) to 11.1 (SD 3.2) at the postoperative check-up (p<0.001). A complete remission of subjective daytime symptoms was achieved, evaluated by ESS. The number of oxygen desaturation events (AHI) decreased drastically in all patients, the mean value falling from 57.9 (SD 21.9) to 7 (SD 4.8) after surgery (p<0.001). All these variations were statistically significant using Student's t-test. Regarding the aesthetic results, five patients reported a slight improvement and six patients a great improvement.

In group II (Table 2) an increase in PAS was recorded, with the mean value rising from 3.7 (SD 1.5) to 10.9 (SD 1.9) at the postoperative check-up (p<0.001). Even in this group a complete remission of subjective symptoms was achieved, evaluated by ESS. The number of AHI decreased from 50.6 (SD 19.2) to 7.6 (SD 4.4) after surgery (p<0.001). Regarding the questionnaire, five patients reported a slight improvement, five patients reported unchanged appearance, and one patient reported a great improvement. In no case was a worsening of the aesthetic appearance reported.

When performed, the 3D evaluation of PAS by helical CT scan, demonstrated a high percentage of increase in volume (Fig. 2a and b).

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• Fig. 2. 

  CT scan with 3D of the airways. (a) Preoperative; (b) postoperative.

The results in both groups were comparable, using Student's t-test analysis (Table 4, Table 5). In particular, the increase of PAS measured on cephalograms, was similar in both groups (252% in group I and 294% in group II).

Table 4. Final results for group I.

	Preoperative	Postoperative	p
PAS	4.4 (DS 2.3)	11.1 (DS 3.2)	p<0.001
AHI	57.9 (DS 20)	7 (DS 4.8)	p<0.001
Epworth S.S.	15.2 (DS 2.4)	0.9 (DS 0.9)	p<0.001

Table 5. Final results for group II.

	Preoperative	Postoperative	p
PAS	3.7 (DS 1.5)	10.9 (DS 1.9)	p<0.001
AHI	50.6 (DS 19.2)	7.6 (DS 4.4)	p<0.001
Epworth S.S.	12.5 (DS 2.2)	0.9 (DS 1)	p<0.001

Remission of symptoms was swift in all cases, and N-CPAP was abandoned immediately after surgery. No temporomandibular joint disorders were reported. One patient had paraesthesia of the lower lip, which persisted at 1 year post-surgery, but was fairly well tolerated by the patient. All the patients were satisfied with the functional and aesthetic results, and would recommend the same treatment to other patients.

All improvements were stable over time from the clinical and instrumental standpoints. There were no significant changes between the immediate postoperative check-up 8–10 days post-surgery, and the long-term check-up (mean follow-up at 13 months, minimum 4 months; maximum 27 months). At the long-term check-up, no patients had a reduction in BMI that could, even partially, explain the remission of symptoms.

Fig. 3, Fig. 4, Fig. 5, Fig. 6 present two significant clinical cases; one from each group, with their clinical and instrumental data.

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• Fig. 3. 

  (a) Preoperative profile; (b) preoperative cephalogram AHI 51, PAS 4, SNA 78°, SNB 71°, ESS 13.

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• Fig. 4. 

  (a) Postoperative profile; (b) postoperative cephalogram, AHI 5, PAS 9, SNA 84°, SNB 80°, ESS 0.

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• Fig. 5. 

  (a) Preoperative profile; (b) preoperative cephalogram, AHI 64, PAS 4, SNA 82°, SNB 81°, ESS 11.

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• Fig. 6. 

  (a) Postoperative profile; (b) postoperative cephalogram, AHI 6, PAS 13, SNA 90°, SNB 88°, ESS 0.

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Discussion 

Treatment of patients with OSAS is not always simple. Patients who are candidates for surgery have severe OSAS and the primary goal of surgery is to resolve, or at least significantly improve, the clinical situation. For surgery to be successful it is necessary to determine the anatomical causes and physiopathological mechanisms underlying the syndrome. A number of different areas may be targeted, but it is now generally agreed that restriction of PAS, especially if this restriction extends vertically, is the critical point for the pathogenesis of OSAS⁴, ¹⁷, ²⁵. Analysis of the literature reveals that the increase in PAS after MMA is greater than that offered by other surgical techniques such as anterior-inferior osteotomy of the mandible or hyoid or lingual suspension⁴, ¹⁷. Li et al.¹⁰ showed that the ‘tightening’ effect of MMA affects the lateral walls of the pharynx, which comprise the aponeuroses and muscles of the hypopharynx; it thus offers a stable and significant reduction in the collapsibility of the hypopharynx.

The enlargement of PAS by MMA has been demonstrated using helical CT scans and 3D evaluation⁴. Using 3D geometrical reconstruction and computational fluid dynamics simulations, it is possible to predict the likely success of treatment, and to forecast the amount of surgical movement necessary to create an adequate airflow²².

In patients with known severe OSAS, MMA is undoubtedly a resolutive operation. Initially, MMA was employed in a second stage of treatment, after failure of previous nasal and/or palatal surgery, and in patients with a cephalometric pattern of cranio-facial anomalies¹, ⁸, ¹⁹. This protocol is still suggested by Schendel and Powell²¹, while Hochban, Miles and Prinsell⁶, ¹³, ¹⁷ propose MMA as the first stage treatment, if necessary followed by other surgical procedures, in patients with cranio-facial anomalies. Recently, MMA has been employed as the first treatment, with simultaneous adjunctive procedures (genioplasty, uvuloplasty, glossoplasty), but always in patients with maxillo-mandibular retroposition or retromandibulism²³.

The authors’ study confirms these data, but emphasizes that, in patients in whom subjective symptoms are significant and with an important restriction of PAS (measured by cephalometrics and/or helical CT scan) the primary indication could be MMA surgery, even in patients without dento-facial anomalies, because the success rate is very high. Other simultaneous procedures can be applied, such genioplasty, septoplasty, turbinates reduction, to achieve a better functional result.

Regarding the possibility of extending indications of MMA to patients without cranio-facial anomalies and with cephalometric, occlusal and aesthetic patterns that are within the normal range, the principal contraindication is the risk of producing protrusion of the jaws, especially regarding the maxilla and superior lip. In the authors’ view this risk should not be overly emphasized, even in the light of another study by Li et al.⁹. The authors think that with adequate reshaving of the anterior nasal spine and pyriform area, and suitable management of the soft tissues during closure of surgical access, with careful alar cinch suture, but without a VY closure, the protrusive effect on the soft tissues and upper lip can be reduced. Advancement genioplasty may also contribute to making any protrusion of the upper lip less apparent. Thus, also for these patients, MMA may provide a primary surgical solution.

The treatment of OSAS and the choice of MMA as primary treatment do not depend only on cephalometric measurements, but mainly on the severity of OSAS and restriction of PAS. The present study and the comparison of the two groups of patients demonstrate that the functional results are comparable.

Recent studies have also demonstrated that MMA is the most effective operation for treatment of OSAS, and the quality of life of the patients treated with this procedure is greatly increased¹².

The authors think that a good grounding in, and experience in the field of, orthognathic surgery is necessary to treat these patients, even if the use of prebent advancement plates can facilitate the procedure, as suggested by Lye et al.¹¹. The OSAS patient presents a complex case from diagnostic approach to the immediate pre- and postoperative periods²¹. In conclusion, the indications for MMA in OSAS patients can be extended significantly to patients without skeletal anomalies, because this procedure constitutes an effective, reliable and versatile surgical solution and may be applied to a wide range of patients with severe or moderate OSAS.

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Funding 

None.

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Competing interests 

None declared.

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Ethical approval 

Not required.

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