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What should your therapeutic option be?
¿Cuál sería su opción terapéutica?

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We present the case of a 26-year-old male that came to our unit for an assessment of a dento-facial deformity associated with an Obstructive Sleep Apnea Syndrome (OSAS); the patient presented micro-retrognathia and an ogival palate and the response in the OSAS to CPAP treatment had been deficient. His medical history included operations, an adenoidectomy and tonsillectomy, and he had hypertrophy of the turbinates. The sleep study prior to treatment resulted in the following: the lowest oxygen saturation was 95%, the average was 80%, and there was a minimum of 58%; 65 desaturations were apparent, 35 of which were less than 90%. Forty obstructive apneas were detected and 94 hypopneas. The apnea/hypopnea index (AHI) was of 18.8 (normal< 5), with light to moderate characteristics and with clinical repercussions (Epworth sleepiness scale of 18).

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Mandibular distraction osteogenesis in severe adult microretrognathia

Distracción osteogénica mandibular en microrretrognatia severa del adulto

 

M. Castrillo Tambay¹, I. Zubillaga Rodríguez², G. Sánchez Aniceto², R. Gutiérrez Díaz², M. Gutiérrez Díez³, J.J. Montalvo Moreno⁴

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1 Medico residente.
2 Medico adjunto.
3 Especialista en Ortodoncia.
4 Jefe de Servicio.
Servicio de Cirugía Oral y Maxilofacial. Madrid. España.

Correspondencia:

Servicio de Cirugía Oral y Maxilofacial
Hospital Universitario «12 de Octubre». Madrid, España.
Avenida de Cordoba s/n. 28041. Madrid, España.
E-mail: manumber@hotmail.com

 

Following a preoperative examination which included lateral and anteroposterior teleradiography of the skull as well as an orthopantomography and cephalometric analysis, opting for the following surgical procedure was decided upon: under general anesthesia bilateral mandibular osteotomies were carried out on the gonial notch via an intraoral vestibular approach over the mandibular ramus; two unidirectional intraoral distractors were used that were capable of producing an advancement of 20 mm. The position on the bone was marked previous to the osteotomy so that the distraction vector could be maintained parallel to the occlusal plane, and so that both distractors could be kept suitably parallel to each other in order to avoid any convergence which could damage the TMJ;¹ these devices are fixed by means of unicortical screws in the distal fragment before the osteotomy and once this has been carried out with a chisel the proximal segment can be fixed. There is less risk of the dental nerve being damaged in this way. Once the distractors were fixed, these were tried in order to ensure that they functioned properly and they were put back into place before closing the incision. After a latency period of three days, distraction was started at a rate of 0.5 mm/12 hours on both sides; the only complication the patient experienced was an episode of bilateral acute locking of the joints with intense pain five days after starting the distraction. As treatment for this, the distraction process was halted for 12 hours, in addition to the relevant medical treatment, after which the distraction process was started at the same rate in order to reach an elongation of 19 mm. Following a consolidation period of four months, the distractors were removed by means of the same approach, and in the same surgical act a reduction mentoplasty with advancement was performed, all under general anesthesia.

The patient currently has the correct occlusion and the sleep study carried out after the surgical correction using the same team and under the same conditions revealed the following data: the lowest oxygen saturation was 94%, with an average of 87.4% and a minimum of 80% (the lowest oxygen saturation level had previously been 95%, with an average of 80% and a minimum of 58%). Fourteen desaturations were detected, 5 of which were less than 90%. An obstructive apnea and a hypopnea were registered with an AHI of 0.4 (the previous registers had been of 65 saturations, 35 below 90%. Forty obstructive apneas were detected and 94 hypopneas, with an apnea/ hypopnea index (AHI) of 18.8). The formation of new bone in both the distraction calluses was confirmed by means of a postsurgical CT scan three months later. In the final diagnosis the presence of OSAS was ruled out and the patient currently does not require any treatment.

Discussion

Obstructive Sleep Apnea Syndrome (OSAS) is associated with a repetitive nocturnal obstruction of the upper airway in the form of apneas (absence of air flow) or hypopneas (flow limitation) that carries additional daytime sleepiness due to sleep fragmentation as a result of micro-arousals, arterial oxygen desaturation and finally of cardiovascular changes in advanced cases (arterial hypertension in 50%, arrhythmias, pulmonary hypertension in 10% among others).^3,4 The OSAS study is carried out by means of a polysomnography that in addition allows the definition of the following diagnostic criteria: Apnea /Hypopnea Index per hour (AHI or RDI)>5 (or 10 according to some authors) or more than 30 episodes during seven consecutive hours of sleep. The RDI allows the classification of the OSAS according to how serious it is: AHI>=5-20 mild; AHI>=20-50 moderate; AHI>50 severe. ⁵ Another measured parameter that is useful for clinical and diagnostic purposes, is oxygen saturation, as it enables us to determine the number of oxygen saturations that are lower than 90% (85% according to some authors) and the minimum oxygen saturation (<60% is considered life threatening).⁴ The criteria for treatment should be: 1) The disappearance of the clinical symptoms (daytime sleepiness, dyspnea, cognitive dysfunction); 2) RDI <5: 3) Min SaO₂>85%.⁵

The usual treatment for OSAS can entail from hygiene and postural measures (weight loss, sleep posture) to the use of a CPAP machine; its efficacy has been demonstrated even from the first days it is used, with associated cardiovascular morbidity being reduced in the medium term; however there is a low tolerance level and the long term cure rate is less than 45%. For this reason various surgical techniques have been proposed for the treatment of OSAS with the basic aim of increasing the upper airway dimension and decreasing its propensity to collapse;³ a tracheotomy is the only procedure that achieves a 100% cure rate and there are still some indications for this procedure despite the associated morbidity.⁴ Uvulopalatopharyngoplasty (UPPP) either classical or laser assisted: the results regarding the decrease in the number of apneas and desaturations during sleep is not very satisfactory, with an approximate 50% improvement in cases but with this percentage decreasing in the long term.⁴ It is however very efficient fo eliminating snoring; other techniques include genioglossus advancement, hyoid suspension, glossopexy, reduction glossoplasty and maxillo-mandibular advancement, all either on their own or combined.² Various studies show the effectiveness of bimaxillary advancement, fundamentally combining a Lefort I osteotomy together with a bilateral mandibular sagittal osteotomy and rigid fixation for those patients with skeletal and dentofacial alterations requiring OSAS treatment.^3,8-10 A new technique has been added to this variety of surgical modalities, which are presented as alternatives to classical orthognathic surgery; this is Distraction Osteogenesis (DO): initially described and applied by Ilizarov for the correction of deformities of the extremities, ¹¹ it was in the 90s decade that its principles were applied in humans to elongate the mandible,¹² permitting the treatment of micrognathia with initially extraoral devices,^13,14 as well as intraoral devices that were developed later. The use of DO in the treatment of OSAS in pediatric patients with craniofacial alterations has been widely developed and good therapeutic results have been demonstrated; ^16,17 However, its use in selected adult patients with OSAS is a little-studied area, that has an application potential that is little known, although recent studies support its efficiency. ^1-3,5

The role of surgery in the treatment of OSAS is nevertheless controversial, given that the existence of a non-aggressive technique that has demonstrated its efficiency as a treatment, such a CPAP, seems to limit the indications for surgery. The patients subjected to surgical techniques require exhaustive control after the surgery by means of objective and detailed polysomnographic monitoring, and comparisons have to be made between the indexes before the surgery and the results afterward. Patient selection is essential. Motives have to be evaluated, and certain cases have to be excluded such as those with morbid obesity, or those with severe associated pathologies, while low CPAP tolerance cases or those with a severe maxillofacial deformity that would clearly benefit from treatment entailing corrective surgery should be included.¹⁸

Returning to the case that concerns us, we are presented with a young man, with no associated medical pathology, who had previously tried CPAP treatment but had experienced an unsatisfactory clinical response with low tolerance and who had, in addition, severe micro-retrognathia. Given the age of the patient and the existence of local deformities that were potentially correctible, surgical correction of the micro-retrognathia was proposed to the patient in conjunction with orthodontic treatment beforehand. Given the characteristics of the case, two therapeutic options could be considered: bimaxillary corrective surgery by means of «classical» orthognathic surgery as opposed to mandibular advancement by means of distraction osteogenesis.^6,7 The advantages that traditional orthognathic surgery gives us would be a solution in a single surgical procedure, a more predictable end result and lower economic costs in conjunction with greater surgical experience. However, in the case that concerns us there was one great disadvantage in that the mandibular advancement required for solving the OSAS was more than 10 mm, while the maximum limit for mandibular advancement by means of bilateral sagittal osteotomies is 10 mm; in addition the risk of relapse is greater, the greater the advancement required due to the tension exerted by the soft tissue attached to the mandible. Other potential inconveniences associated with these procedures are neurological and provoked by the surgical technique and by the changes in the temporomandibular joint (TMJ) due to the rigid fixation in mandibular osteotomies.

With regard to DO, the progressive advancement allows the soft tissues to adapt better while allowing advancements that are far greater than 10 mm with less risk of relapse.³ TMJ discomfort, although frequent during the distraction process, seems to be less in the long term due to the load exerted on the joint being progressive and to the condyle not being fixed. The neurological problems associated with the surgical technique appear less frequently in the case of DO, although there are without doubt much fewer cases; the dental nerve allows progressive elongation without there being any functional consequences in the long run. However, the DO also has its inconveniences; the main one is based on the direction of the vector of distraction, a factor that increases when two or more distractors are used simultaneously that require a parallelism to be maintained among them;³ in the case of mandibular advancement, the tendency to develop open bite during the distraction is frequent. In some cases, in order to avoid this, directing the advancement by means of directional bands will be necessary. As adults are involved, not all of them will be able to accept the additional orthodontic treatment and the final occlusion is thus made much more difficult. This fact, in addition to the need for at least two surgical procedures, one for placing the distractor and another for removing it, and the treatment that is long, and which entails four months and greater cost, should lead us to chose correctly those cases we are to treat.

Conclusions

Surgical treatment of adults with OSAS should be established for certain patients possessing the right characteristics; from these we will be able to select a candidate for treatment by means of DO; more experience is still required given that the number of patients treated with this technique is still scarce.

References

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