Mandibular Osteotomy for Expanded Transoral Robotic Surgery: A Novel Technique

Transcription

1 The Laryngoscope VC 2014 The American Laryngological, Rhinological and Otological Society, Inc. Mandibular Osteotomy for Expanded Transoral Robotic Surgery: A Novel Technique Alfred Marc C. Iloreta, MD; Katie Anderson, MSBME; Brett A. Miles, DDS, MD Objectives/Hypothesis: Transoral Robotic Surgery (TORS) has revolutionized the surgical treatment of malignant lesions of the oropharyngeal region. Recent studies have shown that this approach is a very safe procedure and can provide favorable clinical and functional outcomes with respect to traditional approaches. However, a small minority of patients who present with lesions amenable to TORS resection may not be candidates due to anatomical access issues. Anatomic features such as a retrognathic mandible, macroglossia, trismus, dentition, and small oral aperture limit the ability to perform TORS with current technology. We propose a modified TORS approach in which transoral mandibular osteotomies are performed that can greatly improve exposure to oropharyngeal subsites and expand access to the larynx in selected patients. Study Design: Five experimental procedures were performed on five cadavers. Methods: Five cadavers were obtained for the investigation. Measurements including retractor opening, lateral cephalography, acoustic pharyngometry, and high-resolution photographs were taken prior to mandibular osteotomies and then repeated following the osteotomies. Results: An increase in retractor opening, transoral exposure, and oral cavity was observed in all specimens. Conclusions: Mandibular osteotomies increase exposure to oral cavity and oropharyngeal lesions in the setting of TORS. Key Words: Transoral Robotic Surgery, HPV related oropharyngeal cancer, osteotomy, squamous cell carcinoma. Level of Evidence: N/A. Laryngoscope, 124: , 2014 INTRODUCTION Transoral Robotic Surgery (TORS) has revolutionized the treatment of head and neck cancer, specifically for malignant lesions of the oropharyngeal region. In an era marked by advances in minimally invasive surgery, the TORS approach has allowed surgeons to perform oncological sound resections of tumors while decreasing treatment-related morbidity and improving posttreatment quality of life. 1,2 Recent studies have shown that this approach is a safe procedure and can provide favorable clinical and functional outcomes with respect to traditional approaches. These investigations have noted several advantages relative to traditional transmandibular approaches, which include faster recovery of swallowing and vocal function, decreased need for reconstruction, decreased incidence in aspiration pneumonia, and decreased length of hospitalization. 3,4 From the Department of Otolaryngology Head and Neck Surgery (A.M.C.I., B.A.M.); the Department of Oral and Maxillofacial Surgery (B.A.M.), Mount Sinai School of Medicine, New York, New York; the Intuitive Surgical (K.A.), Sunnyvale, California, U.S.A Editor s Note: This Manuscript was accepted for publication December 30, Intuitive Surgical Inc., DepuySynthes Companies, SleepGS Solutions provided material support. The authors have no other funding, financial relationships, or conflicts of interest to disclose. Send correspondence to Brett A. Miles, DDS, MD, FACS, Department of Otolaryngology Head and Neck Surgery, The Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, Box 1189, New York, NY brett.miles@mountsinai.org DOI: /lary The robotic systems currently employed by TORS surgeons were initially pioneered by urologic and cardiac surgeons; and with recent advances and the micronization of instrumentation these systems have been adapted for head and neck surgery. Current TORS applications in the head and neck include lesions of the laryngopharyngeal subsites such as the base of tongue, tonsillar fossa, palate, posterior pharynx, and epiglottis. However, a small minority of patients that present with these lesions may not be TORS candidates due to anatomic constraints related to previous therapy or anatomic factors. Patients with anatomic features such as a retrognathic mandible, macroglossia, and small oral aperture limit the ability to provide an adequate surgical port to introduce the endoscopic arm and two instrument arms. Additionally, patients with a history of adjuvant radiotherapy often have resulting cervical fibrosis and treatment-related trismus. Recent literature has demonstrated that salvage surgery with TORS for recurrent oropharynx tumors versus open surgery has superior outcomes with respect to function, morbidity, and operative time. 5 Despite transoral surgery being the favored salvage option, some patients are unable to undergo transoral procedures due to limited access. In these patients, the ability to gain appropriate exposure to the lesion often dictates which patients can undergo TORS/TLMS (transoral laser microsurgery), rather than oncologic considerations alone. Suboptimal exposure leads to increased operative times, greater risk of surgical complications, and the possibility of inadequate surgical resection margins. A recent study from a major robotic center cited 1836

2 that the size of the base of tongue and the epiglottis was a major problem in exposure for the hypopharyx and larynx. 6 This group suggested that partial epiglottectomy can be performed to increase exposure. Because of these anatomic- and treatment-related limitations, many patients have inadequate access to perform a sound oncologic resection with TORS. Patients who are unable to undergo TORS procedures due to anatomic limitations are often salvaged with traditional transmandibular approaches and subjected to the associated morbidity of these procedures. We propose a modified TORS approach in which transoral mandibular osteotomies are performed that can greatly improve exposure to oropharyngeal subsites and expand access to the larynx in selected patients. This technique takes advantage of transoral mandibular osteomy to improve surgical access without the increased morbidity of transmandibular or transfacial approaches, which would be required in many patients with inadequate access for TORS. In addition, due to similar anatomic constraints our technique can applied to any transoral surgery requiring increased access, such as in the case of TORS or TLMS. This investigation is designed to test the hypothesis that mandibular osteotomies can expand access to the oral cavity, oropharynx, hypopharynx, and supraglottis. MATERIALS AND METHODS To assess the preclinical viability of our technique, we compared the surgical access and exposure of the standard TORS approach to the modified MOTORS approach in five cadaveric specimens. Assessment of surgical exposure was performed using several different metrics, as described below. Five fresh cadaveric specimens were employed in the study. Both approaches were compared with high-resolution images from the endoscope and camera, measurements of the aperture of the oral cavity, lateral radiographs using spinal needles to depict the angles of exposure, and an acoustic pharyngometer. All measurements were collected in a standard database format (Microsoft Excel, Microsoft Corp., Redmond, WA). Age, height, weight, sex, and maximal incisor opening are depicted in Table I. Preosteotomy measurements were then performed, as outlined below. Maximal incisal opening was measured as the interincisal distance at the maximal mouth opening. Specimens were placed on standard operating room tables in the surgical position with cervical flexion an atlantoocciptal extension; a shoulder roll was not employed. Sutures were passed through the anterior tongue to allow for traction of the tongue during placement of the retractor. The Feyh- Kastenbauer (FK) retractor (Gyrus ACMI, Southborough, MA) was then placed in the standard fashion for TORS. The retractor was then deployed to its maximal opening in the craniocaudal and transverse dimensions with the standard blades and cheek retractors. Measurements were then taken of the vertical and horizontal distance of the FK-retractor aperture opening. The surgical aperture of the oral cavity, as defined by the distance between the retractor blades, was measured in the craniocaudal dimension. The transverse distance was measured between the cheek retractor blades at the level of the oral cavity. After these baseline measurements, extraoral digital photographs were taken at a fixed focal length to allow 1:1 reproducibility and comparison after osteotomy. The da Vinci TABLE I. Subject Demographic Information and Anatomical/Pharyngometric Measurements Before and After Osteotomy. Demographics MIO 38 48* 41 30* 32 Age Height (m) Weight (kg) Sex M F M F M BMI (kg/m^2) Measurements Prior to Osteotomy Subject Craniocaudal Transverse Pharyngometer Mean Mean Measurements Following Osteotomy Subject Craniocaudal Transverse Pharyngometer Mean Mean BMI 5 body mass index; MIO 5 maximal incisional opening. *Subjects 2 and 4 were edentulous. Surgical System (Intuitive Surgical Inc., Sunnyvale, CA) was then positioned and docked in the standard TORS surgical position. The endoscopic camera was then positioned at the entrance of the oral cavity at a standard point marked on the FK retractor system to allow for a reproducible focal distance for comparison. Simulated surgical endoscopic video and pictures were captured using the 0-degree scope. The da Vinci Surgical System was then removed from the oral cavity. Spinal needles were placed to approximate the superior and inferior angles of the surgical approach in the sagittal plane. An operative C-arm (OED Series 9600, General Electric, CT) was then placed at a standardized distance from the operative table, and lateral radiographs were taken. The C-arm and operative table were locked into place in order to provide accurate lateral radiographs and prevent magnification error. Preintervention and postintervention pharyngeal volume was approximated using acoustic pharyngometry. In addition to nasal cavity and nasopharyngeal volume assessment, this tool has been used by sleep apnea clinicians to assess the geometry and volume of the oropharyngeal cavity. 7,8 The device emits an acoustic signal and measures the reflection to determine volume. Simply stated, the amplitude and frequency of the reflected waves depend on the cross-sectional area, and the 1837

3 Fig. 1. A. Sagittal cross section of oral cavity prior to mandibulotomy and following mandibulotomy. B. The tongue is retracted into the space created by the midline osteotomy between the mandibular segments. Surgical access is further augmented by slight rotation of the mandibular segments in a lateral plane. time taken for the reflected wave to return is a function of distance. Previous studies have compared this method to other traditional methods such as cephalometrics, computed tomography, and magnetic resonance imaging, and these studies have found no significant difference in its ability to estimate airway area The acoustic pharyngometer (Eccovision, Miami, FL) was positioned at the entrance of the oral cavity at a standardized distance marked on the FK retractor system. A rubber gasket with soaked towels was employed to create an acoustic seal around the pharynx. In addition, the nose and nasal cavity were occluded prior to acquiring acoustic measurements in order to limit the volume assessment to the oropharynx and hypopharyngeal region. Measurements were recorded as cross sectional area versus pharyngeal depth. Trace measurements were recorded from the aperture of the oral cavity to the level of the glottis. The volume of this cavity was then recorded as the integrated area under the curve between the oral cavity and the glottis. This value was measured in triplicate in every specimen in order to reduce sampling error. Surgical Technique After the baseline measurements were taken, the specimens were then sequentially modified by a transoral midline mandibulotomy. No external incisions are used with this technique. A midline mucosal incision was performed, and mucoperiosteal dissection exposed the mandibular symphysis sufficiently for osteotomy. Reflection of the lingual mucoperiosteum exposed the lingual surface of the mandible in order to prevent damage to the lingual tissues and submandibular ducts. Preadaptation of titanium plates in an appropriate fixation scheme was performed prior to osteotomy. A reciprocating saw with a thin osteotomy blade was then used to make a midline mandibular osteotomy from the inferior border through the alveolar segment between the central incisors (see Figure 1 for illustration of procedure). After performing the mandibular osteotomy, the FK retractor was replaced and maximally deployed as previously stated above. Postosteotomy measurements were then performed as outlined in the above protocol (Fig. 1A and Fig. 1B). The interval change in measurements following the intervention (volume, craniocaudal length, transverse length) were calculated as the subtracted difference between preosteotomy measurements and postosteotomy measurements. Mean values were calculated using Microsoft Excel (Microsoft Corp., Redmond, WA) of all applicable data, including maximal incisional opening (MIO), age, height, weight, body mass index (BMI), craniocaudal distance, transverse distance, volume measurements from the acoustic pharyngometer, and delta values. Photographs were cropped and edited in Aperture (Apple Computer, Cupertino, CA) and Adobe Photoshop (Adobe Systems, San Francisco, CA). Aside from cropping and the addition of figures, the images were not manipulated in any way. Subject 1 underwent an additional feasibility procedure to determine the utility of the sagittal split osteotomy for accessing lateral pharyngeal/pyriform sinus lesions. After undergoing the standard midline osteotomy, anatomic reduction and rigid fixation was performed on the mandibular symphysis. After restoration of mandibular continuity, unilateral sagittal split osteotomy at the left mandibular ramus was performed (Fig. 2A 2B). Pharyngeal exposure using the Supraglottic FK blade was then performed, and access was assessed with digital and endoscopic photographs (Fig. 2B 2C). RESULTS Resulting data of individual measurements are summarized in Table I. There were three male specimens and two female specimens, with a mean weight of 71.6 kilograms, a mean height of 1.79 meters, and a mean calculated BMI of Mean MIO was MIO for the general population is approximately 47.1 mm, with a range between 33.7 mm and 60.4 mm. 13 The 1838

4 Fig. 2. Representative photographs of subject 1. Plate A/B is following unilateral sagittal-split osteotomy taken from a digital camera. Plate C/ D is the endoscope picture taken using the supraglottic retraction blade. Note the dramatic increase of hypopharyngeal exposure and pyriform sinus access provided by the osteotomy. mean craniocaudal aperture with the FK retractor maximally positioned (standard) was 39.4 mm, and mean transverse aperture was 74.4 mm. Performing the midline mandibular osteotomy in the cadaveric specimens took approximately 5 minutes. Postosteotomy mean craniocaudal aperture was 57.0 mm, and mean transverse aperture was 72.4 mm. The average change following osteotomy was a 17.6 mm increase in crandiocaudal aperture and a 2 mm loss in transverse aperture. The mean volume of the oral cavity and oropharynx, as measured by the acoustic pharyngometer, was cm/3; and the postintervention volume was measured as cm/3. The average increase in volume was 21.7 cm/3. DISCUSSION This preliminary investigation represents the first application of transoral mandibular osteotomies to increase the exposure for TORS. For the majority of cases, traditional TORS surgery offers excellent results and reduced morbidity relative to traditional transmandibular approaches. In patients who would be candidates for TORS from an oncologic standpoint, but have limited surgical access related to anatomical variations or previous therapy, MOTORS offers significant additional surgical access without the additional morbidity of transmandibular/transfacial approaches. While the functional impact of the addition of a mandibular osteotomy during TORS surgery remains unknown, the procedure does increase the possibility of additional morbidity and increases operative time. It should be noted, however, that mandibular osteotomies performed for traditional orthognathic surgery are well tolerated and functional outcomes are excellent. Coupling these techniques with TORS surgery may offer an excellent alternative approach to patients who would not otherwise be candidates for TORS. When comparing the visualization with standard TORS approach to the MOTORS technique in cadavers, all subjects exhibited a dramatic increase in exposure of the epiglottis, hypopharynx, and base of tongue (see Fig. 3). Midline mandibular osteotomy with separation creates improved access via a two-fold mechanism. Firstly, the bulk of the tongue musculature is retracted into the space created when the mandible is separated. In addition, the mandible is allowed to splay laterally about the condylar axis. The result is an expanded optical cavity posteriorly, as well as anterior displacement of the base of tongue and epiglottis, creating improved surgical access. The lateral radiographs reveal the expansion of the optical working cavity (see Fig. 4).The additional caudal and anterior retraction of the tongue allows this area to be placed on-stretch to optimize both visualization of the tumor and augment surgical dissection with increased tissue traction. One of the more dramatic 1839

5 Fig. 3. Representative photographs of subject 4 with a very limited mouth opening. Plate A-1 is the captured image taken using the 0- degree telescope of patient 2, with the retractor in place prior to mandibulotomy. Plate A-2 is the captured image following mandibulotomy. Plate B-1 is an image taken using a digital camera prior to mandibulotomy. Plate B-2 is the picture taken following mandibulotomy. changes was with subject 3, with a large body habitus (BMI of 33.1), barrel chest, blunted cervico-mental angle, and a large tongue. Comparing the preosteotomy and postosteotomy photographs, the significant improvement of the exposure of the epiglottis and base of tongue is obvious (see Fig. 5). The feasibility of transoral robotic supraglottic laryngectomy has been assessed by several groups; and one center has shown that it can be performed safely, with appropriate surgical margins and excellent functional outcomes. 14 However, each group has commented that inadequate transoral exposure was the critical point in performing the procedure. The MOTORS approach reduces this technical challenge by increasing anterior and caudal retraction of the tongue. Displacement of the bulk of the oral tongue into the space created by the midline mandibular osteotomy offers significant increase in the volume of the hypopharyngeal optical cavity, and visualization of the base of tongue and hypopharyngeal region. By optimizing the angle of attack and the working cavity of the current instrumentation, surgical resection at the hypopharynx and larynx would be significantly augmented. During our cadaver study, we performed feasibility testing of current robotic instrumentation; and it appears that functional access to the oropharyngeal and laryngeal subsites is improved. However, further investigation will need to be performed to demonstrate that current instrumentation will be able to reliably meet requirements to perform adequate surgical procedures with anatomic targets that were previously inaccessible prior to osteotomy, especially in the hypopharynx and the larynx. Further developments/improvements in instrumentation may be necessary to fully appreciate the benefits of improved access with the MOTORS technique. The obvious argument against the MOTORS approach is the added morbidity of the midline mandibulotomy, which is somewhat counterintuitive to a minimally invasive surgical technique such as TORS. It should be noted, however, that several investigations evaluating transmandibular approaches which include midline mandibulotomy with a lip-splitting incision and floor of mouth division with mylohyoid myotomy have shown that this is a safe, reliable technique associated with few complications, mainly related to local wound healing. 15,16 Using the standard transmandibular approach the suprahyoid musculature is left intact, however, the genioglossus and geniohyoid are transected. In several series, transection of these muscles produced minimal problems with swallowing. 15,17 By performing a transoral midline mandibulotomy, the attachments of the genioglossus and geniohyoid muscles are disrupted to a lesser degree relative to the separation in a standard transmandibular approach. Additionally, paramidline mandibulotomy may avoid transection of the genioglossus and geniohyoid musculature; however, previous studies have indicated that there is no difference in complication rates. 18,

6 The incorporation of a piezoelectric bone scalpel to perform the midline osteotomy may further limit the morbidity because its use is associated with a lower operating temperature and a finer osteotomy, which would minimize damage to nearby dentition and surrounding bone. Some authors have suggested the incorporation of planned dental extractions to increase exposure; however, these extractions are associated with a significant cosmetic and functional morbidity, and we would not recommend the routine use of dental extractions in this population. Midline mandibular osteotomy offers minimal risk of injuring neurovascular structures with minimal disruption of blood supply. It is also important to note that the osteotomy is not generally in the field of radiation for oropharyngeal and hypopharyngeal lesions. There is some risk to the dentition if inappropriate techniques are utilized. We recommend use of a thin osteotomy blade with the surgical reciprocating saw for the mandibular osteotomy and a thin osteotome for interdental separation after scoring the outer alveolar cortex. When performed appropriately, this will ensure minimal bone loss and decrease the incidence of injury to the dentition. In addition, meticulous soft tissue management with appropriate incision designs, which are not coincident to the location of the osteotomy, can minimize complications. In vivo, this procedure would add an estimated 30 minutes to the procedure to include the osteotomy and rigid fixation performed using miniplates or lag screw techniques. 20 Fixation of the mandible with a single titanium plate at the inferior border has been a proven method to repair the osteotomy and does not require intermaxillary or maxillomandibular fixation. Fig. 4. Lateral cephalograms taken prior (series 1) to midline mandibulotomy, with retractor in place and after the mandibulotomy was performed (series 2). (Plate A corresponds to patient 1; plate B corresponds to patient 2, etc.) The green shaded area represents the area between the retractors and the optical working cavity provided by the retraction. CONCLUSION This study represents the first application of transoral mandibular osteotomies to augment the current TORS approach. We have shown the feasibility and effectiveness in our technique by demonstrating the approach in five cadaveric specimens. By using both subjective and objective metrics, there is little doubt that our modification will expand surgical access in patients with a variety of anatomical challenges. Advances in robotic instrumentation will likely expand the application of TORS techniques in patients with difficult access. These advances will offer the most significant gains in terms of robotic access in the head and neck, with specifically designed head and neck systems currently being developed and available in the future. Nevertheless, operative management requires appropriate access, regardless of the robotic system for visualization and control of hemorrhage and in some patients this may require some variation of mandibulotomy. While we do not advocate routine use of this approach, it certainly should be considered for patients who would otherwise be candidates for TORS but have limited access. This approach has the potential to broaden the application of transoral robotic surgery for patients, regardless of body type and treatment-related morbidity. We are currently obtaining pilot data regarding the use of the MOTORS technique in selected patients; and future investigations 1841

7 Fig. 5. Representative photographs of subject 3 with a large body habitus and a large tongue. Plate A-1 is the captured image using the 0- degree telescope with the retractor in place prior to mandibulotomy. Plate A-2 is the captured image following mandibulotomy. Plate B-1 is the extraoral digital photograph prior to mandibulotomy. B-2 is the picture taken following mandibulotomy. will determine which patients are best suited for this approach and will help define the surgical and functional outcomes of the technique. BIBLIOGRAPHY 1. Newman JG, Kuppersmith RB, O Malley BW. Robotics and telesurgery in otolaryngology. Otolaryngol. Clin North Am 2011;44: Iseli TA, Kulbersh BD, Iseli CE, Carroll WR, Rosenthal EL, Magnuson JS. Functional outcomes after transoral robotic surgery for head and neck cancer. YMHN 2009;141: Genden EM, Desai S, Sung C-K. Transoral robotic surgery for the management of head and neck cancer: a preliminary experience. Head Neck 2009;31: Sinclair CF, McColloch NL, Carroll WR, Rosenthal EL, Desmond RA, Magnuson JS. Patient-perceived and objective functional outcomes following transoral robotic surgery for early oropharyngeal carcinoma. Arch Otolaryngol Head Neck Surg 2011;137: White H, Ford S, Bush B, et al. Salvage surgery for recurrent cancers of the oropharynx: comparing TORS with standard open surgical approaches. JAMA Otolaryngol Head Neck Surg 2013;139: doi: /jamaoto De Virgilio A, Park YM, Kim WS, Baek SJ, Kim S-H. How to optimize laryngeal and hypopharyngeal exposure in transoral robotic surgery. Auris Nasus Larynx 2013;40: doi: /j.anl Epub Gelardi M, Del Giudice AM, Cariti F, et al. Acoustic pharyngometry: clinical and instrumental correlations in sleep disorders. Braz J Otorhinolaryngol 2007;73: Kamal I. Test-retest validity of acoustic pharyngometry measurements. Otolaryngol Head Neck Surg 2004;130: Jung DG, Cho HY, Grunstein RR, Yee B. Predictive value of Kushida index and acoustic pharyngometry for the evaluation of upper airway in subjects with or without obstructive sleep apnea. J Korean Med Sci 2004; 19: Fredberg JJ, Wohl ME, Glass GM, Dorkin HL. Airway area by acoustic reflections measured at the mouth. J Appl Physiol 1980;48: Gelardi M, Del Giudice AM, Cariti F, Cassano M, Farras AC, Fiorella ML, Cassano P. Acoustic pharyngometry: clinical and instrumental correlations in sleep disorders. Braz J Otorhinolaryngol 2007;73: Kamal I. Test-retest validity of acoustic pharyngometry measurements. Otolaryngol Head Neck Surg 2004;130: Cox SC, Walker DM. Establishing a normal range for mouth opening: its use in screening for oral submucous fibrosis. Br J Oral Maxillofac Surg 1997;35: Ozer E, Alvarez B, Kakarala K, Durmus K, Teknos TN, Carrau RL. Clinical outcomes of transoral robotic supraglottic laryngectomy. Head Neck 2013;35: doi: /hed Epub Eisen MD, Weinstein GS, Chalian A, et al. Morbidity after midline mandibulotomy and radiation therapy. Am J Otolaryngol 2000;21: El-Zohairy MA. Straight midline mandibulotomy: technique and results of treatment. J Egypt Natl Canc Inst 2007;19: Amin MR, Deschler DG, Hayden RE. Straight midline mandibulotomy revisited. Laryngoscope 1999;109: Pan W-L, Hao S-P, Lin Y-S, Chang K-P, Su J-L. The anatomical basis for mandibulotomy: midline versus paramidline. Laryngoscope 2003;113: Dai T-S, Hao S-P, Chang K-P, Pan W-L, Yeh H-C, Tsang N-M. Complications of mandibulotomy: midline versus paramidline. YMHN 2003;128: Serletti JM, Coniglio JU, Pacella SJ, Norante JD. Transverse lag screw fixation in midline mandibulotomy: a case series. Ann Otol Rhinol Laryngol 2000;109: