Genioglossus and Genioplasty Advancement

Key points

  • Genioglossus advancement with or without genioplasty is technique used as part of multilevel treatment of obstructive sleep apnea.

  • Many modifications have been described to tailor the technique to patient and surgeon specifications.

  • Computer-aided surgical planning and 3-dimensional printed guides remove much of the challenges of the surgery and allow for patient-specific osteotomy designs.

Introduction

Obstructive sleep apnea (OSA) is a complicated disease that is multifactorial. In many patients, obstruction at the level of the hypopharynx plays a prominent role. Examination of genioglossus activity in sleeping patients has identified progressive relaxation of tone culminating in obstructive events. This suggests that the genioglossus muscle plays an important role in OSA.

Genioglossus advancement (GA), sometimes combined with hyoid suspension, is a surgery aimed at treating hypopharyngeal obstruction. It is often performed along with tonsillectomy, adenoidectomy, and uvulopalatopharyngoplasty as part of multilevel surgery. Because it is rarely performed in isolation, it is difficult to say how effective GA is in relieving hypopharyngeal obstruction and treating OSA. As part of multilevel surgery, analyses of case series (not controlled) have found success rates (defined as at least a 50% reduction in the Apnea-Hypopnea Index (AHI) and an AHI below 20) ranged between 40% and 70%. A recent prospective study of patients with mild to moderate OSA receiving GA only has found similar success rates of 53%.

Riley and colleagues initially described GA as the inferior sagittal mandibular osteotomy. The ultimate goal was to advance the portion of the mandible that includes the genial tubercles, the attachment of the genioglossus muscle. Advancement of the genial tubercles is believed to tighten the genioglossus muscle, thereby mitigating relaxation and posterior positioning of the base of tongue and obstruction of the hypopharynx ( Figs. 1 and 2 ). Since that time, there have been several modifications to this technique.

Fig. 1
Genioglossus muscle.
( Courtesy of Stanley Y.C. Liu, MD, DDS, Stanford, CA.)

Fig. 2
Fixation with genioglossus muscle.
( Courtesy of Stanley Y.C. Liu, MD, DDS, Stanford, CA.)

Modifications have included the anterior mandibular osteotomy, trephine osteotomy, genioplasty with genioglossus suspension suture, and combining anterior mandibular osteotomy with a genioplasty, among others. Recent advances in computer-simulated surgery and 3-dimensional (3-D) printing of medical-grade cutting guides have allowed for patient-specific precision surgery on the inferior mandible.

In this article, we review workup of patients for this procedure, indications and proper case selection, and a technique for performing GA with and without genioplasty. Complications also are discussed, to aid the reader in preoperative patient counseling.

Preoperative planning

The workup of a patient with OSA is discussed elsewhere in detail. To briefly summarize, it starts with a careful history before moving onto physical examination. The focused examination of the head and neck should include a facial analysis, paying particular attention to the anterior-posterior and vertical development of the maxillomandibular complex.

A fiberoptic nasopharyngolaryngoscopy examination is a requisite part of the examination to identify the degree and level (or levels) of obstruction. Although helpful, awake upright fiberoptic examination does not accurately represent the conditions that occur with sleep-related obstructions.

If a patient is suspected of having a sleep disorder, a polysomnogram is performed to further characterize, diagnose, and grade the severity of the disorder.

Finally, a drug-induced sleep endoscopy is often a very helpful study that mitigates the limitations of an awake fiberoptic examination.

Indications

GA, alone or as part of a genioplasty, is typically one component of multilevel surgery to address OSA. The primary indication for GA is obstruction at the hypopharyngeal level, especially when associated with a retruded position of the base of tongue. Patients with mandibular retrognathism and retrogenia, in particular, benefit from GA with genioplasty, as it addresses both the hypopharyngeal obstruction and the dentofacial deformity.

Certain patients may have hypopharyngeal obstruction without significant or obvious retrognathism and retrogenia. These patients may not want the morphologic changes associated with an advancement genioplasty. In these circumstances, the anterior mandibular osteotomy should be considered.

As mentioned previously, there are limited data about the effectiveness of GA performed in isolation for treating OSA. The small number of studies examining the efficacy of GA have suggested that the technique, when performed without maxillomandibular advancement, was more likely to be effective in patients with mild to moderate OSA. As such, it is prudent to reserve isolated GA to patients with an AHI of 5 to 30.

Computer surgical planning

Traditionally, one of the more challenging parts of GA with genioplasty is performing the osteotomies in such a way that captures the genial tubercle and attachments of the genioglossus muscle. These osteotomies are performed from the labial cortex without being able to visualize the attachments that are on the lingual cortex. In addition, the apices of the mandibular incisors are in close proximity, making them at risk of injury by an errant saw blade. Several techniques have been described to allow for reliable approximation of the positioning of the osteotomies. However, the advent of computer-aided surgical planning and 3-D printed tooth borne cutting guides has eliminated most of this risk. Because I use computer planning exclusively when planning this procedure, I will restrict my technique description to this approach.

The digital work flow follows the clinical examination and includes a maxillofacial computed tomogram (CT) ( Fig. 3 ). Although a medical-grade spiral CT with fine cuts is the most accurate, a cone-beam CT (CBCT) is serviceable, faster (when available), and exposes the patient to much less radiation. A dental impression is also taken. If an analog impression is used, this is poured up into a model. The model is scanned. Both the CBCT of the patient and dental models are sent electronically to the computer surgical planning company of choice. Previously, fiduciary occlusal wafers or jigs were required so that the model and facial CBCTs could be registered to each other, but current software algorithms allow for this to be performed accurately without this additional step. If digital impressions are taken, the file can be sent electronically.

Fig. 3
Digital workflow for genioplasty. Blue boxes indicate steps performed by the surgeon. Green boxes indicate steps performed by computer engineers.

Once received, the computer surgical planning is started with creation of 3D models and registration of the dental model to the maxillofacial model. Because CT imaging of the dentition is usually of poor resolution and obscured by restorative artifacts, the dental model is essential so that any tooth born guide will be accurate. This is performed off-line by the computer engineer.

A Web-based meeting is initiated. During this session, the surgeon and computer engineer plan the osteotomies and desired movements of the genioplasty segment. The ability to manipulate and visualize the lingual aspect of the mandible and the roots of the mandibular incisors is of tremendous utility. Because of this improved visualization, patient-specific osteotomies can be planned with a high degree of both accuracy and safety.

There are some important considerations during the planning that should be observed. The first is identification of the genial tubercles. The second is highlighting the position of the mandibular incisors and canines. When planning for an anterior mandibular osteotomy (GA without genioplasty), the osteotomies must be parallel or diverging from lingual to labial, to allow the bone segment freedom to be drawn anteriorly. Finally, more or less of chin is included, depending on what would be more harmonious with the patient’s facial form.

Once the Web meeting is completed, the remaining work is performed by the computer engineer off-line. A tooth borne cutting guide is designed, with guide planes for the saw cuts and predictive holes in the genioplasty segment ( Fig. 4 ). For GA with genioplasty, a second positioning guide is designed with the desired advancement ( Fig. 5 ). This is intended to be fixated to the genioplasty segment using the previously placed predictive holes. This allows for accurate replication of the desired planned movement.

Jan 19, 2020 | Posted by in Oral and Maxillofacial Surgery | Comments Off on Genioglossus and Genioplasty Advancement
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