Since the introduction of the GA procedure for OSA patients as an effective method of mandibular inferior border osteotomy for genioglossus advancement [6, 7], surgeons attempted other variations on this technique to improve efficacy. Currently, the most widely utilized technique employs the formation of a rectangular osteotomy within the mandible. When performed correctly, the GA surgical procedure addresses the retrolingual obstruction and significantly improves patency of the airway [5,6,7,8].
The success or failure of the GA technique relies prominently in accurately identifying the attachment of the belly of the genioglossus muscle to the mandible. From anatomical studies based on cadaveric dissections and radiographic imaging, the skeletal attachment of the genioglossus muscle appears localized about the genial tubercle. As with many anatomical structures, some degree of variation exists among the patient population.
Moreover, the accurate location of the muscle attachment remains difficult to confirm even intraoperatively causing some degree of consternation to the novice surgeon. Though the genioglossus muscle and genial tubercle area are palpable by means of digital pressure on the anterior mouth floor area, the spatial information and relationship to other anatomical structures remain elusive to the surgeon with limited experience in performing this procedure. Due to this inherent uncertainty and difficulty in localizing the attachment of the genioglossus muscle to the mandible, several groups attempted cadaveric studies to more clearly delineate the skeletal attachment [10, 12, 13].
Other groups augmented these findings with radiographic imaging modalities. Though more practical, imaging based on X-ray radiography presents some limitations on accurately identifying soft tissue structures. Consequently, two studies attempted to validate the radiographic evaluations by comparing cadaveric measurements to those obtained from CT scans [11, 13].
Because OSA typically presents with greater prevalence in skeletal occlusion class II patients with a posteriorly displaced and small chin, the dimension and the location of the genial tubercle appears more important for optimizing the assessment and plan for treatment. One radiographic study using CBCT compared the measurements based on the skeletal pattern and genders [14]. This group’s results revealed that the IGT-IMB (distance from the mandibular inferior border to the inferior margin of genial tubercle) of skeletal class II males was significantly different when compared to that of the skeletal class I female. However, they concluded that no significant differences existed among the skeletal patterns and genders even with the noted difference in IGT-IMB.
As for the dimensional difference between males and females in the context of the local anatomy for genioglossus advancement, most of the literature provided no specificity of the gender of their respective subjects. They did, however, present the distances between the superior border of the genial tubercle and the apex of the lower incisor separately with respect to the gender of the subject [13]. Use of three-dimensional CBCT scans improves visualization of the local anatomy. However, X-ray radiography remains limited in its ability to identify soft tissue morphology. Subsequently, accurate identification of the attachment of the belly of the genioglossus muscle to the mandible during genioglossus advancement remains difficult. Through experience and development of knowledge regarding spatial anatomy, the surgeon gains more expertise in more accurately performing the GA technique.
Previous cadaveric studies provided clear visualization of the genioglossus muscle and its subsequent attachments to the mandible. These studies helped to elucidate a relationship with these attachments to the position of the genial tubercle. To augment this estimation of muscle attachment, imaging modalities rely heavily upon X-ray radiography. Further, in order to validate radiographic studies of the lingual topography of the anterior mandible, some researchers correlated the cadaveric dissection with CT scans. These measurements vary among studies. We reviewed these anatomic and radiographic studies and compared the measurements from each study. From this systematic review, manual palpation to identify genial tubercle might be important; however, with the progress of digital technology and three-dimensional imaging techniques, we can definitely take advantage of the virtual surgery system to capture the genial tubercle [17]. Therefore, based on this observation, individual planning should be considered when genioglossus advancement is planned.