Robotic microlaryngeal surgery: a technical feasibility study using the daVinci surgical robot and an airway mannequin

OBJECTIVES/HYPOTHESIS: The trend toward minimally invasive surgery has led to the development and mastery of endoscopic and laparoscopic surgical techniques. These minimally invasive approaches, which only two decades ago were either novel or experimental, are now mainstream. More recently, robot-assisted surgery has evolved as an adjunct to open and endoscopic techniques. Surgical robots are now approved by the United States Food and Drug Administration for a variety of thoracic and abdominal/pelvic surgical procedures. The purpose of this study is to demonstrate the technical feasibility of robot-assisted microlaryngeal surgery. STUDY DESIGN: Experimental surgical manipulation of the larynx in an airway mannequin with a surgical robot. METHODS: A variety of laryngoscopes and mouthgags, coupled with the daVinci Surgical Robot's (Intuitive Surgical, Sunnyvale, CA) 0-degree and 30-degree, two-dimensional and three-dimensional endoscopes, were utilized to optimize visualization of the larynx in an airway mannequin. Five millimeter and 8 mm microinstruments compatible with the daVinci robot were utilized to manipulate different elements of the larynx. Experiments were recorded with both still and video photography. RESULTS: The endoscope and robotic arms of the daVinci robot are well suited to airway surgery. CONCLUSIONS: Robot-assisted laryngeal surgery can be performed with currently available technology. The potential for fine manipulation of tissues, increased freedom of instrument movement, and endolaryngeal suturing may increase the precision of endoscopic laryngeal microsurgery and offers the potential to increase the variety of laryngeal procedures that can be performed endoscopically.     

Robotic surgery in the pediatric airway: application and safety

OBJECTIVE: To assess the application and safety of transoral robotic surgery in the pediatric airway. DESIGN: An institutional review board-approved study. Experimental laryngeal surgery was performed on 4 pediatric cadaver larynxes as controls. Application of robotic equipment for laryngeal surgery was attempted on 5 patients. SETTING: Tertiary care pediatric medical center. PATIENTS: Five patients with laryngeal cleft and 4 pediatric cadaver larynxes. INTERVENTIONS: (1) The da Vinci Surgical Robot (Intuitive Surgical Inc, Sunnyvale, Calif) was used on 4 cadaver larynxes and assessed for the dexterity, precision, and depth perception that it allowed the surgeon during laryngeal surgery. Procedures were documented with still and video photography. (2) The da Vinci Surgical Robot was used through a transoral approach to attempt repair of a laryngeal cleft in 5 pediatric patients who were under spontaneously breathing general anesthesia. RESULTS: (1) Use of the surgical robot on cadaver larynxes provided great dexterity and precision, delicate tissue handling, good 3-dimensional depth perception, and relatively easy endolaryngeal suturing. (2) The surgical robot could not be used for repair of laryngeal cleft on 3 patients owing to limited transoral access. However, 1 patient with a type 1 laryngeal cleft and 1 patient with a type 2 laryngeal cleft underwent transoral robotic repair with great success. CONCLUSIONS: Surgical robots provide the ability to manipulate instruments at their distal end with great precision, increased freedom of movement, and excellent 3-dimensional depth perception. The size of the equipment can be a limiting factor with regard to the application and success of the transoral approach to airway surgery. We believe that further advances in device technology and a new generation of robotic equipment will facilitate the incorporation of surgical robotics in the advancement of minimally invasive endoscopic airway surgery.     

Assessment of intraoperative safety in transoral robotic surgery

INTRODUCTION: Robotic technology has been safely integrated into thoracic and abdominopelvic surgery, and the early experience has been very promising with very rare complications related to robotic device failure. Recently, several reports have documented the technical feasibility of transoral robotic surgery (TORS) with the daVinci Surgical System. Proposed pharyngeal and laryngeal applications include radical tonsillectomy, base-of-tongue resection, supraglottic laryngectomy, and phonomicrosurgery. The safety of transoral placement of the robotic endoscope and instruments has not been established. Potential risks specific to the transoral use of the surgical robot include facial skin laceration, tooth injury, mucosal laceration, mandible fracture, cervical spine fracture, and ocular injury. We hypothesize that these particular risks of transoral surgery are similar with robotic assistance compared with conventional transoral surgery. METHODS: To test this hypothesis, we attempted to intentionally injure a human cadaver with the daVinci Surgical System by impaling the facial skin and pharyngeal and laryngeal mucosa with the robotic instruments and endoscope. We also attempted to extract or fracture teeth and fracture the cadaver's mandible and cervical spine by applying maximal pressure and torque with the robotic arms. Experiments were documented with still and video photography. RESULTS: Impaling the cadaver's skin and mucosa resulted in only superficial lacerations. Tooth, mandible, and cervical spine fracture could not be achieved. CONCLUSIONS: Initial experiments performing TORS on a human cadaver with the daVinci Surgical System demonstrate a safety profile similar to conventional transoral surgery. Additionally, we discuss several strategies to increase patient safety in TORS.     

Transoral robot-assisted CO2 laser supraglottic laryngectomy: experimental and clinical data

BACKGROUND: Transoral CO2 laser surgery for selected supraglottic tumors results in improved postoperative function and decreased morbidity, with comparable survival to open surgery. Recently, robot-assisted techniques have been reported for the management of supraglottic lesions. There are no reports in the English literature of robotic technology coupled with CO2 laser technology. Our objective was to report the use of such technology. STUDY DESIGN: Experimental resection of the supraglottis in a cadaver and a dog model using a commercially available surgical robot coupled with CO2 laser technology. Initial human experience with such technology is reported. METHODS: With use of a hollow core fiber that allows the transmission of CO2 laser energy linked to the daVinci Surgical Robot, a supraglottic laryngectomy was performed in an edentulous female cadaver. The FK Laryngo-Pharyngoscope was used for exposure. In a second experiment, a supraglottic partial laryngectomy was performed in an 80 pound dog. On the basis of our experimental experience, a CO2 laser robotic-assisted supraglottic laryngectomy was attempted in three patients. RESULTS: Removal of the supraglottic larynx in both a cadaver and canine experimental models was believed to be satisfactory using this technology. Bleeding was easily controlled in the live canine model. A 74-year-old woman with a large supraglottic mass for which she had been offered a total laryngectomy was resected successfully with this technology. The FK Laryngo-Pharyngoscope provided excellent exposure. The patient was able to swallow without difficulty on postoperative day 5. Follow-up endoscopic examination at 1 month showed no evidence of residual laryngeal tumor. Robot-assisted procedures were attempted in two additional patients, but adequate exposure could not be achieved, and more traditional techniques were performed. CONCLUSIONS: The use of the daVinci Surgical robot coupled with CO2 laser technology is feasible, as demonstrated by our experimental and clinical data. Although further development of the robotic technology is required at present, the use of robotics coupled with CO2 laser technology may have important implications in the management of supraglottic laryngeal cancer in the future.     

Maintenance of hemostasis in transoral robotic surgery

BACKGROUND: The last decade has seen a tremendous growth in the field of robotic surgery with an increasing number of cardiac and urologic procedures performed each year. Several attributes of this technology may offer advantages to laryngeal and pharyngeal surgery in that it allows for exceptional visualization of the operative field, precise handling of soft tissues, and multiplanar transection of tissues. One potential limitation is the management of bleeding in transoral pharyngeal and laryngeal surgery, which is critical to prevent both intravascular volume loss and aspiration. OBJECTIVES: To demonstrate methods for management of bleeding in the surgical field during transoral robotic surgery (TORS). METHODS: We developed a canine robotic surgery model for the evaluation of the ability to control bleeding in laryngeal and pharyngeal procedures using the daVinci surgical robot (Intuitive Surgical, Inc., Sunnyvale, Calif., USA). Both large- and small-vessel hemostasis was obtained with both robotically controlled monopolar and bipolar cautery and with robotically controlled small hemoclips. Additionally, manually controlled large hemoclips were applied by an assistant surgeon viewing on a video monitor for management of large arterial vessels. Suction was performed with both flexible suction catheters controlled by the robotic arms and with manually controlled conventional suction catheters. Data were collected with still and video photography. RESULTS: The lingual artery as well as small arteries and veins were easily controlled and there were no difficulties with maintenance of hemostasis. CONCLUSIONS: Effective hemostasis with control of both large and small vessels can be obtained using both surgical hemoclips and electrocautery during TORS in a canine model.     

Transoral robotic surgery: supraglottic laryngectomy in a canine model

OBJECTIVES/HYPOTHESIS: To develop a technique for computer enhanced robotic transoral supraglottic partial laryngectomy in the canine model. STUDY DESIGN: Surgical procedure on the larynx in a canine model with a commercially available surgical robot. METHODS: With use of the da Vinci Surgical Robot (Intuitive Surgical, Inc., Sunnyvale, CA), the supraglottic partial laryngectomy was performed on a mongrel dog that had been orotracheally intubated using general anesthesia. The videoscope and the 8 mm end-effectors of the robotic system were introduced through three ports, transorally. The surgical procedure was performed remotely from the robotic system console. The procedure was documented with still and video photography. RESULTS: Supraglottic partial laryngectomy was successfully performed using the da Vinci Surgical Robot, with 8 mm instrumentation. The robotic system allowed for celerity and accuracy secondary to findings specific to the surgical approach, including excellent hemostasis, superb visualization of the operative field with expeditious identification of laryngeal submucosal soft tissue and skeletal landmarks, and multiplanar transection of tissues. In addition, the use of the robotic system also was found to have technical advantages inherent in robotic surgery, including the use of "wristed" instrumentation, tremor abolition, motion scaling, and three-dimensional vision. CONCLUSIONS: The da Vinci Surgical Robot allowed for successful robotic transoral supraglottic partial laryngectomy in the canine model.     

Transoral robotic surgery (TORS) for base of tongue neoplasms

OBJECTIVE: To develop a minimally invasive surgical technique for the treatment of base of tongue neoplasms using the optical and technical advantages of robotic surgical instrumentation. STUDY DESIGN: Ten experimental procedures including tongue base exposure and dissections were performed on three cadavers and two mongrel dogs. Transoral robotic surgery (TORS) was then performed on three human patients with tongue base cancers in a prospective human trial. METHODS: Using the da Vinci Surgical Robot (Intuitive Surgical, Inc., Sunnyvale, CA), we performed a total of 10 base of tongue resections on edentulous and dentate cadavers as well as live mongrel dogs. In the cadaver models, exposure was evaluated using three different retractors, the Dingman, Crowe Davis, and FK retractors. The three human patients underwent TORS surgery of their tongue base cancers under an institutional review board approved prospective clinical trial. The ability to identify and preserve or resect key anatomic structures such as the glossopharyngeal, hypoglossal, and lingual nerves as well as techniques for identifying the lingual artery and achieving hemostasis were developed. RESULTS: The da Vinci Surgical Robot provided excellent visualization and enabled removal of the posterior one third to one half of the oral tongue in cadavers, dogs, and human patients. Among the three retractors evaluated, the FK retractor offered the greatest versatility and overall exposure for robotic instrument maneuverability. Complete resection to negative surgical margins with excellent hemostasis and no complications was achieved in the live patient surgeries. CONCLUSIONS: TORS provided excellent three-dimensional visualization and instrument access that allowed successful surgical resections from cadaver models to human patients. TORS is a novel and minimally invasive approach to tongue neoplasms that has significant advantages over classic open surgery or endoscopic transoral laser surgery.     

Surgical robotic applications in otolaryngology

OBJECTIVES: To explore the feasibility of performing endo-robotic neck surgery in a porcine model and to compare the results of robotically enhanced endoscopic surgery with those from a conventional endoscopic technique. STUDY DESIGN: Prospective, nonrandomized experimental investigation in a porcine model. METHODS: We performed a consecutive series of endoscopic neck surgeries using the daVinci surgical system (Intuitive Surgical Inc.). The length of time required to establish the operative pocket and to assemble the robotic components, as well as the total duration of each operation, was recorded. The animals were continuously monitored for heart rate, blood pressure, and end-tidal CO(2) pressure, and evaluation for presence of pneumothorax and subcutaneous emphysema was undertaken postoperatively. The specimens were examined histologically. RESULTS: Four different types of neck surgery were successfully performed on both sides of the neck of four animals using the daVinci surgical system. Creation of the operative pocket took, on average (+/-SD), 18.1 +/- 11.9 minutes, and assembly of the robot required 12.5 +/- 9.9 minutes, resulting in a mean preparation time for all procedures of 30.6 +/- 21.0 minutes. The mean operative time for submandibular resection (n = 3) was 19.0 +/- 6.6 minutes, with a total procedure time of 39.0 +/- 10.2 minutes. Selective neck dissections (n = 3) required a mean operative time of 66.0 +/- 18.5 minutes and a total procedure time of 85.7 +/- 16.7 minutes. One partial parotidectomy and one thymectomy were also performed. The median estimated blood loss was 0 mL (range, 0-10 mL). The end-tidal CO(2) pressure fell from the start to the end of the procedures by a mean of 4.4 +/- 7.9 mm Hg. The blood pressure fell by a mean of 1.9 +/- 7.5 mm Hg. There was one case of modest subcutaneous emphysema, and there were no cases of pneumothorax or air embolism. No conversions to open resection were necessary. CONCLUSIONS: Robotically enhanced endoscopic surgery in the neck is feasible and offers a number of compelling advantages over conventional endoscopic neck surgery. Clinical trials will be necessary to determine whether these advantages can be achieved in clinical practice.     

Laser Versus Cold Instruments for Microlaryngoscopic Surgery

Controversy has arisen concerning the merits of the CO₂ laser in microlaryngoscopic surgery because of the potentially harmful effects that the injudicious application of the laser could have on voice production. In an effort to develop a logical approach to instrument selection, the author examined the use of both cold instruments and the CO₂ laser in the treatment of various benign and malignant lesions. A retrospective review of 307 microlaryngeal procedures performed over a 3-year period revealed that 263 (86%) were glottal and 44 (14%) were supraglottal. Of the 263 glottal procedures, 203 (77%) employed cold instruments alone and 60 (23%) used both cold instruments and the CO₂ laser. The laser was used to assist in all 44 supraglottal procedures. Therefore, 203 (66%) of 307 procedures were done with cold instruments alone, and 104 (34%) of 307 procedures were performed using the CO₂ laser with cold instruments. Lesions were stratified on the basis of pathology and size, as well as surgical approach. A primary phonomicrosurgical principle in glottal surgery is to maximally preserve the vocal fold's layered microstructure (laminae propria and epithelium). Precise tangential dissection was necessary for achieving this goal. For limited lesions, this dissection was best accomplished with cold instruments alone. The CO₂ laser facilitated hemostatic surgical dissection for all supraglottal lesions and for selected larger glottal lesions in which bleeding would obscure visualization of the microanatomy of the musculomembranous vocal fold. Laryngoscope, 106:545-552, 1996     

Laryngeal function-preserving operation for T4a laryngeal cancer with vocal cord paralysis — A case report

For locally advanced laryngeal cancers, the standard treatment of choice is chemoradiotherapy if organ function needs to be conserved. Surgical treatment with larynx preservation is conducted only for limited cases. For locally advanced laryngeal cancers such as those with vocal cord fixation and/or cricoid cartilage destruction, there is no apparent standardized organ-preserving surgery keeping the essential laryngeal functions, viz. the airway, deglutition and articulation, uncompromized.Recently, our surgical team saw a patient with T4a advanced laryngeal cancer with vocal cord fixation who aspired to maintain his laryngeal function. Driven by his eagerness, we contrived novel techniques for laryngeal function preservation and performed a two-staged operation.In the first stage, extended vertical partial laryngectomy was conducted including resection of the affected thyroid, arytenoid, and cricoid cartilages, followed by local closure of the hypopharynx. Additionally, laryngeal suspension surgery and cricopharyngeal myotomy were performed in addition to suturing the epiglottis with the intact arytenoid cartilage to enhance swallowing function. In the second stage, airway reconstruction was performed using a local skin flap.As of 10 months after operation, there has been no tumor recurrence, and the reconstructed larynx has been working satisfactorily.In this report we describe an innovative operation that was especially contrived for laryngeal function preservation.     

Benign lesions of the larynx: Should the laser be used?

The use of the carbon dioxide (CO2) laser in the treatment of patients with benign laryngeal lesions, excluding respiratory papillomatosis, has been questioned because of potential adverse thermal effects on surrounding tissue. We question whether wound healing and subsequent quality of voice would be better if the surgeon used the "cold technique" with microlaryngeal instruments. Since the advent, in 1987, of a small-spot (0.3 mm) CO2 laser micromanipulator and more precise microlaryngeal instruments, we have redefined our use of the CO2 laser for benign laryngeal lesions. Over the past 4 years, in a series of 68 consecutive patients with vocal cord nodules, polyps, polypoid changes, or granulomas, the CO2 laser was useful for mucosal micro-flap dissection techniques and for vascular lesions. Smaller pedunculated lesions, such as vocal cord nodules, were more efficiently removed with the new microlaryngeal instrumentation. The combined selective use of a microspot CO2 laser at low-power settings (1 to 3 W), with 0.1-second pulses, and with precise microlaryngeal instruments will give the best results.     

The AESOP robot system for video-assisted rigid endoscopic laryngosurgery

Surgeons may occasionally encounter difficulty in visualizing the whole larynx with a direct laryngoscope. In such cases, rigid endoscopic laryngosurgery using a direct laryngoscope is an optimal solution. Multidirectional examination of the larynx using rigid endoscopes during direct laryngoscopy, leads to better control and management of the ventricle, inferior surface of the vocal fold and subglottis, and the anterior commissure. Currently, 0 degrees , 30 degrees , 70 degrees and 120 degrees angled rigid telescopes are used worldwide. Our experience in telescopic endolaryngeal surgery provided us the opportunity to work with AESOP 3000 (automated endoscope system for optimal positioning), coupling a robotic arm to a rigid endolaryngeal telescope. The use of this device allows the surgeon to control the field of view and operate with both hands. A total of 20 patients presenting a laryngeal lesion were randomly selected and included in this study undergoing a robot-assisted procedure. Three of 20 patients presented a difficult laryngeal exposure with direct laryngoscopy due to a rigid, short neck (1 male, 1 female) and prominent teeth (1 male). We used Karl Storz Hopkins II long rigid endoscopes having 0 degrees , 30 degrees and 70 degrees direction of view, a Storz Xenon 300 cold light, a Storz Tricam SL camera, the Kleinsasser direct laryngoscope. The instruments we used are all commercially available for microlaryngeal surgery and included upward curved instruments in case of difficult laryngeal exposure. The operative equipment was the same for all procedures. We evaluated the acquisition of skills in controlling the AESOP 3000, the feasibility of a single surgeon performing procedures with this machine, and any advantages that it might offer to endolaryngeal surgery. The use of robotic devices improves the precision of surgical procedures, offering surgeons a more comfortable working position, particularly for longer procedures, and without an assistant to hold the camera.     

Mechatronik in der HNO-Chirurgie

BACKGROUND: This study examines the advantages and disadvantages of a commercial telemanipulator system (daVinci, Intuitive Surgical, USA) with computer-guided instruments in functional endoscopic sinus surgery (FESS). METHODS: We performed five different surgical FESS steps on 14 anatomical preparation and compared them with conventional FESS. A total of 140 procedures were examined taking into account the following parameters: degrees of freedom (DOF), duration , learning curve, force feedback, human-machine-interface. RESULTS: Telemanipulatory instruments have more DOF available then conventional instrumentation in FESS. The average time consumed by configuration of the telemanipulator is around 9+/-2 min. Missing force feedback is evaluated mainly as a disadvantage of the telemanipulator. Scaling was evaluated as helpful. The ergonomic concept seems to be better than the conventional solution. DISCUSSION: Computer guided instruments showed better results for the available DOF of the instruments. The human-machine-interface is more adaptable and variable then in conventional instrumentation. Motion scaling and indexing are characteristics of the telemanipulator concept which are helpful for FESS in our study.     

梨状窝内侧壁癌切除与喉功能保留

目的 探讨梨状窝内侧壁癌切除喉功能保留犬的技术方法和临床疗效。方法 回顾分析手术治疗的梨状窝内侧壁癌71例。其中49例行喉功能保留术;22例未保存喉功能。喉功能保留手术方法：①切除范围：声带活动正常者行患侧水平上半喉＋梨状窝内侧壁切除;声带活动受限者行同侧水平半喉＋声门旁间隙＋梨状窝内侧壁切除;声带固定者行患侧垂直半喉＋梨状窝内侧壁和部分梨状窝外侧壁切除,梨状窝尖受累者切除范围扩大到环状软骨环和颈段食管;②修复:喉修复对利用会厌、甲状软骨膜、带状肌肌筋膜、颈前皮瓣修复喉缺损;梨状窝修复对缺损范围小者用下咽粘膜瓣或残缘粘膜后直接讨合,对缺损范围大者用胸大肌肌皮瓣转移及胸三角皮瓣修复;③颈淋巴结处理：71例中65例（91．5％）行颈清扫术,其中同侧颈清扫术39例,双侧颈清扫术26例;④术后全部病例予以辅助放射性治疗,剂量60－75Gy。结果 寿命表法统计3年、5年生存率：喉功能保留组分别为63．4％和49．6％;喉功能不保留组分别为52．4％和42．4％。喉功能保留组喉功能全部恢复者占71．4％（35／49）,部分恢复者占28．6％（14／49）。结论 梨状窝内侧壁癌易侵入喉部,但多数病例在彻底切除肿瘤病灶的前提下保留喉功能是可行的。     

Transoral robotic surgery: supraglottic partial laryngectomy

OBJECTIVES: We assessed the feasibility of performing transoral supraglottic partial laryngectomy with robotic instrumentation. METHODS: Transoral robotic surgery (TORS) was performed on 3 human patients with supraglottic carcinoma in a prospective human trial. The study was approved by our institutional review board and involved the da Vinci Surgical Robot (Intuitive Surgical, Inc, Sunnyvale, California). RESULTS: All procedures were completed robotically. The median overall operation time to perform the robotic procedure was 120 minutes (range, 1:32:48 to 2:58:18), including 18 minutes (range, 00:6:07 to 00:30:39) for exposure and robotic positioning. There were no intraoperative or postoperative complications or surgical mortality. CONCLUSIONS: The preliminary results of our series suggest that application of the da Vinci robotic surgical system for TORS to supraglottic partial laryngectomy is technically feasible and relatively safe. Furthermore, TORS provides excellent surgical exposure that allows complete tumor resection. Most importantly, TORS provides an alternative to open approaches and "conventional" transoral supraglottic partial laryngectomy.     

An integrated simulator for endolaryngeal surgery

The acquisition and maintenance of skills in transoral microlaryngeal surgery requires extended practice. Effective mentoring of such single-operator procedures is not possible, making it important for trainee surgeons to acquire basic skills outside of the operating room before participating in procedures on patients. Currently available training simulators use either synthetic materials or human tissue, both of which have limitations. We have designed a hybrid simulator that incorporates a porcine larynx in to an airway training manikin, providing both accurate airway anatomy and natural tissue handling characteristics. This model allows training in the skills required for suspension laryngoscopy and the resection of laryngeal lesions. Further applications could include development of surgical techniques and instruments, and use in accreditation of training and revalidation of trained surgeons.     

闭合性喉外伤伴杓区损伤的临床特征和内镜下治疗

目的:探讨闭合性喉外伤伴杓区损伤的临床特征、内镜下手术治疗及疗效。方法:回顾性研究2007年4月至2018年12月因明显声音嘶哑就诊于首都医科大学附属北京同仁医院耳鼻咽喉头颈外科的闭合性喉外伤伴杓区损伤患者12例,其中男10例,女2例,年龄7~48岁,中位年龄21岁,患者均在全身麻醉和支撑喉镜下行喉显微修复手术。评估其...     

Thyroarytenoid muscle maintains normal contractile force in chronic vocal fold immobility.

BACKGROUND: Denervation of skeletal muscle typically results in irreversible denervation atrophy over time. This finding has generated controversy as to the efficacy of reinnervation procedures for chronic vocal fold immobility related to recurrent laryngeal nerve injury. OBJECTIVE: To test the hypothesis that chronic vocal fold immobility after recurrent laryngeal nerve injury does not result in diminished maximal isometric force generation in the thyroarytenoid muscle. STUDY DESIGN: Adult random-bred cats underwent either unilateral laryngeal denervation (n = 6) or sham surgery (n = 6). After 6 months, videolaryngoscopy was performed followed by in vitro measurement of maximal isometric tetanic force produced by the thyroarytenoid muscle. RESULTS: All animals in the denervation group showed right vocal fold paralysis after the initial denervation operation; none of these animals had return of appropriately phased movement with respiration. Four had intermittent disorganized twitching movements. One had these movements plus an occasional weak adduction, and one had no movement. Normal vocal fold mobility was observed in 6 of 6 animals undergoing sham surgery. The maximal isometric tetanic force measured from the thyroarytenoid muscle in the sham group was 438 mN (+/-92 mN standard deviation [SD]). The maximal isometric tetanic force measured from the thyroarytenoid muscle in the chronically immobile group was 405 mN (+/-107 mN SD). Differences were not statistically significant. CONCLUSION: Maximal isometric force in the thyroarytenoid muscle is not diminished in chronic vocal fold immobility after recurrent laryngeal nerve injury. We conclude that the possibility for restoration of contractile force to the chronically immobile thyroarytenoid muscle exists. This finding supports the pursuit of reinnervation procedures in the treatment of chronic vocal fold immobility.     

Histological basis for indirect videostroboscopic phonosurgery —a scanning electron microscopic study

Indications for indirect videostroboscopic surgery are well established for small, benign functional lesions of the vocal folds. Epithelial cells of the vocal folds are spindle-shaped and by their long axies run parallel to the free edge of the vocal fold. This occurrence is used clinically by surgeons to obtain an even operative defect when using a cup forceps during single-handed manipulations. Nevertheless, there are still some doubts about single-handed procedures, so that many surgeons prefer the convenience of bimanual manipulation offered by direct (suspension) microlaryngoscopic surgery. The aim of this study was to demonstrate that single-handed manipulation during indirect videostroboscopic surgery permitted obtaining regular edges of an operative defect during laryngeal surgery. A scanning electron microscopic study was conducted on five cadaver larynges following indirect videoscopic excisions at the vocal fold's free edge and ten controls. Results demonstrated a clearly regular edge of the operative defects in cases when a posterior traction surgical procedure was followed. These findings reaffirm the value of indirect videostroboscopic surgery for small, benign functional lesions of the vocal folds.     

Vocal fold paralysis after anterior cervical spine surgery: incidence, mechanism, and prevention of injury

OBJECTIVE: Vocal fold paralysis is the most common otolaryngological complication after anterior cervical spine surgery (ACSS). However, the frequency and etiology of this injury are not clearly defined. This study was performed to establish the incidence and mechanism of vocal fold paralysis in ACSS and to determine whether controlling for endotracheal tube/laryngeal wall interactions induced by the cervical retraction system could decrease the rate of paralysis. STUDY DESIGN: Retrospective review and complementary cadaver dissection. METHODS: Data gathered on 900 consecutive patients undergoing ACSS were reviewed for complications and procedural risk factors. After the first 250 cases an intervention consisting of monitoring of endotracheal tube cuff pressure and release of pressure after retractor placement or repositioning was employed. This allowed the endotracheal tube to re-center within the larynx. In addition, anterior approaches to the cervical spine were performed on fresh, intubated cadavers and studied with videofluoroscopy following retractor placement. RESULTS: Thirty cases of vocal fold paralysis consistent with recurrent laryngeal nerve injury were identified with three patients having permanent paralysis. With this technique temporary paralysis rates decreased from 6.4% to 1.69% (P = .0002). The cadaver studies confirmed that the retractor displaced the larynx against the shaft of the endotracheal tube with impingement on the vulnerable intralaryngeal segment of the recurrent laryngeal nerve. CONCLUSION: The study results suggest that the most common cause of vocal fold paralysis after anterior cervical spine surgery is compression of the recurrent laryngeal nerve within the endolarynx. Endotracheal tube cuff pressure monitoring and release after retractor placement may prevent injury to the recurrent laryngeal nerve during anterior cervical spine surgery.