Hyoid Expansion With Titanium Plate and Screw: A Human Cadaveric Study Using Computer-Assisted Airway Measurement

Importance  Hyoid expansion with suspension can potentially increase the upper airway at the hypopharyngeal level, benefitting patients with sleep-related breathing disorder.

Objectives  To document the effect of hyoid expansion using titanium plate and screw on retrolingual hypopharyngeal airway dimension and to compare the airway dimension after isolated hyoid expansion with hyoid expansion + hyomandibular suspension.

Design  Anatomical cadaveric dissection study.

Setting  This study was performed in a laboratory setting using human cadavers.

Intervention  This is an anatomical feasibility study of hyoid expansion using titanium plate and screw on 10 cadaveric human heads and necks. The hyoid bone is trifractured with bony cuts made just medial to the lesser cornu. The freed hyoid body and lateral segments are expanded and stabilized to a titanium adaptation plate. Computer-assisted airway measurement (CAM) was used to measure the airway dimension at the hypopharynx at the level of the tongue base before and after the hyoid expansion. The expanded hyoid bone was then suspended to the mandible, and the airway dimension was measured again with CAM.

Main Outcomes and Measures  Airway dimension after isolated hyoid expansion with hyoid expansion with hyomandibular suspension.

Results  Hyoid expansion with titanium plate and screw resulted in statistical significant increase in the retrolingual hypopharyngeal airway space in all of the 10 human cadavers. The mean (SD) increase in retroglossal area was 33.4 (13.2) mm² (P < .005) (range, 6.0-58.7 mm²). Hyoid expansion with hyomandibular suspension resulted in a greater degree of airway enlargement. The mean (SD) increase in retroglossal area was 99.4 (15.0) mm² (P < .005) (range, 81.9-127.5 mm²).

Conclusions and Relevance  The retrolingual hypopharyngeal airway space increased with hyoid expansion using titanium plate and screw in our human cadaveric study, measured using CAM. The degree of increase is further augmented with hyomandibular suspension.

The hyoid bone is closely related to the hypopharyngeal airway dimension. It is attached to the epiglottis via the hyoepiglottic ligament and the tongue base via the genioglossus and hyoglossus muscles. The middle constrictors muscles are attached to the lesser cornu. During inspiration, the hyoid bone moves anteriorly, and hyoid muscles activity helps maintain upper airway patency.¹ Numerous investigations have supported the concept that surgical intervention at the hyoid level may improve the posterior airway space.^2-5

Patton and coworkers^6,7 investigated the idea of hyoid expansion in a live canine model and showed that hyoid expansion can favorably alter the anatomic relations involved in collapse of the hypopharynx and base of tongue without compromising swallowing function.

We postulate that the tongue base–hypopharyngeal region airway dimension can be increased by expanding the hyoid bone and stabilizing it with titanium plating. We aimed to quantify the increase in anterior-posterior dimensional using computer-assisted videoendoscopic measurement (CAM) on fresh human cadavers. We also compared hyoid expansion with hyoid expansion + hyomandibular suspension. To our knowledge, there is no such study in the literature.

This is an anatomical feasibility study of human cadaveric hyoid–epiglottis–tongue base complex from April 2011 to November 2011. Ten human cadaveric heads and necks were obtained from persons of unknown age for this study. All specimens had their hyoid and mandible intact, as well as intact oropharyngeal and laryngo-hypopharyngeal airway. This study was approved by the Singapore General Hospital institutional review board.

The fresh human cadaveric neck was exposed from the mandible to the larynx cartilage, in the supine position with the face toward the ceiling. A horizontal skin incision approximately 4 to 5 cm long was made at the level of the hyoid bone. The incision was deepened through the subcutaneous layer and platysmal muscle. Once the skin and subplatysmal planes were elevated, the hyoid was identified. The anterior aspect of the hyoid bone is skeletonized. To ensure that the hyoepiglottic ligament and genioglossus muscle attachment to the body of the hyoid are not dissected off the central portion of the hyoid, care is taken not to traumatize the posterior aspect of the hyoid bone. The airway size was measured using CAM, a well-validated and published methodology.^8-10 A ruler, as the calibrator, was placed in the hypopharyngeal area and using digital measurement software (Bersoft Image Measurement software 6.0; Bersoft Inc). We used a Karl Storz 45° telescope to view the hypopharyngeal, and images were captured using the Karl Storz Telepack system (Karl Storz GmbH). The preadvancement retroglossal airway area was measured (Figure 1). The central hyoid body was isolated by fracturing the hyoid bone medial to the lesser cornu using a bone cutter. We bent a 12-hole titanium adaption plate (AO Synthes Compact 2.0 System) into the shape of the hyoid. Using a 1.5-mm drill bit, we drilled 2 to 3 holes on the hyoid body and then attached the hyoid body to the plate using two 1.3-mm self-tapping 8-mm screws. The lateral segments (with greater cornu) of the hyoid are then screwed to the titanium plate using 1.3-mm self-tapping 6-mm screws. If it is not possible to place the drill holes on the greater cornu, 2-0 silk sutures were used to secure the greater cornu to the titanium plate, keeping the trifractured hyoid in an expanded position (Figure 2). We were able to attach the titanium plate and screws onto the body (center part) on all 10 of the trifractured hyoid. The greater cornu has less bone than the body, and in 4 cases we were unable to create the necessary screw holes to attach the hyoid bone to the titanium plate. In these instances, we had to secure the separated greater cornu to the titanium plate using 2-0 silk suture. We were able to achieve a 2–drill-hole length between each segment. The retroglossal area was then measured (Figure 3A). Two bony holes were drilled at the inferior border of the mandible, and the expanded hyoid bone was suspended from the mandible as previously described.² The retroglossal area after suspension was then measured (Figure 3B).

All statistical analyses were performed using SPSS statistical package version 16.0 (SPSS Inc) All mean values are shown as mean (standard deviation). Differences in the value of mean with the appropriate 95% confidence interval were shown using a paired-sample test.

Hyoid expansion by trifracturing the hyoid bone and titanium plate and screw resulted in a statistical significant increase in the hypopharyngeal airway dimension in all cadaveric head and neck dissections (Table 1). Hyoid expansion resulted in a mean (SD) increase in retroglossal area of 33.4 (13.2) mm² (P < .005) (range, 16.0-58.7 mm²). Hyoid expansion with hyomandibular suspension resulted in a greater degree of airway enlargement. The mean (SD) increase in retroglossal area was 99.4 (15.0) mm² (P < .005) (range, 81.9-127.5 mm²) (Table 2).

Our study showed that trifracturing of the hyoid bone and stabilization with titanium plate and screw led to an increase in the hypopharyngeal airway dimension measured at the retroglossal area. This increase in airway dimension is further augmented with hyomandibular suspension.

The concept of expansion hyoidplasty was explored in a study using an experimental live canine model, in which the investigators showed that the hyoid bone can be trisected, expanded, stabilized, and held in place using arch bars and wires. This technique leads to a decreased closing pressure and an expanded superior hypopharyngeal measurement.^6,7,11 The researchers had expanded the hyoid anteriorly by 1.21 cm and laterally by 0.91 cm, on average. However, there were no data on the corresponding increase in intraluminal airway size, and there was no follow-up human study on its applicability for use in human with obstructive sleep apnea syndrome (OSAS).

The concept of modifying the hypopharyngeal airway size using the hyoid bone and its musculature has been applied to the treatment of OSAS. Since Riley and colleagues² described hyomandibular suspension and myotomy in a patient with OSAS in 1984, there are various modifications to the original technique.^3,12,13 Hyoid myotomy and suspension has become part of the surgeons’ armamentarium to treat obstructive sleep apnea in a multilevel airway modification concept. The technique of hyomandibular suspension moves the entire hyoid bone with its attached muscles and ligaments to either the mandible or thyroid cartilage. Stuck et al¹⁴ had demonstrated that the airway size did not increase in patients who had undergone the procedure, and its effect is likely to be due to stabilization and prevention of tongue base collapse rather than increase in airway dimension. Our study demonstrates that expansion of the hyoid bone, with the central body anteriorly and lateral segment laterally, can lead to an increase in airway size while possibly stabilizing the tongue base, preventing its collapse. This is further augmented with suspension of the expanded hyoid bone to the mandible. A recent report by Hamans et al¹⁵ demonstrated that hyoid expansion using an airframe device decreased snoring and daytime sleepiness symptoms but did not decrease parameters on an overnight polysomnogram. The degree of airway improvement, however, was not reported, and the addition of a hyomandibular suspension procedure with expansion was not studied. This favorable report, however, points to the usefulness of hyoid surgery in improving sleep-related breathing disorder and warrants further investigations.

There are several limitations of our study. First, this is a study with human cadavers. The tension of ligaments and muscles and thus the amount of airway increment may not be representative in a live human. Second, the amount of increase in airway dimension is not consistent. We were able to achieve a greater degree of airway increase in some cadavers than in others. Third, we were not able to make a consistent measurement of the expansion, but we were able to achieve a 2–drill-hole length between the segments. Further studies are required to investigate the effect of hyoid expansion with titanium plate and screw on live humans and on sleep-related breathing disorder.

In conclusion, the retrolingual hypopharyngeal airway space increased with expansion of the hyoid, and hyoid expansion with suspension further augments the airway, as measured with CAM. The degree of increased airway space varies. Further studies are required to translate this technique to clinical use to address hypopharyngeal obstruction in patients.

Corresponding Author: Song-Tar Toh, MBBS(S’pore), MMED(ORL), MRCSEd, FAMS(ORL), Sleep Apnea Surgery Service, Department of Otolaryngology–Head and Neck Surgery, Singapore General Hospital, Outram Road, Singapore 169608 (songtar@gmail.com).

Submitted for Publication: January 31, 2013; final revision received April 3, 2013; accepted May 15, 2013.

Author Contributions: Dr Toh had full access to all the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis.

Study concept and design: Toh, Hsu, Tan, Lu.

Acquisition of data: Toh.

Analysis and interpretation of data: Toh, Han.

Drafting of the manuscript: Toh.

Critical revision of the manuscript for important intellectual content: All authors.

Statistical analysis: Toh.

Obtained funding: Toh.

Administrative, technical, and material support: All authors.

Conflict of Interest Disclosures: None reported.

Funding/Support: This study was supported by a Singhealth Foundation Startup grant (SHF/FG403S/2009).