Minimally invasive unilateral arytenoid lateralization in dogs: A cadaveric study

    Minimally invasive unilateral arytenoid lateralization in dogs: A cadaveric study A. Shipov, I. Israeli, M. Weiser, E. Kelmer, S. Kleinbart, J. Milgram PII: DOI: Reference:

S0034-5288(15)30027-8 doi: 10.1016/j.rvsc.2015.07.019 YRVSC 2926

To appear in: Received date: Revised date: Accepted date:

9 June 2014 13 July 2015 26 July 2015

Please cite this article as: Shipov, A., Israeli, I., Weiser, M., Kelmer, E., Kleinbart, S., Milgram, J., Minimally invasive unilateral arytenoid lateralization in dogs: A cadaveric study, (2015), doi: 10.1016/j.rvsc.2015.07.019

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ACCEPTED MANUSCRIPT Minimally invasive unilateral arytenoid lateralization in dogs: A cadaveric study

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A. Shipov a, I. Israeli a, M. Weiser a, E. Kelmer a, S. Kleinbart a, J. Milgram a*

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Veterinary Teaching Hospital, Koret School of Veterinary Medicine, The Hebrew University of Jerusalem, P.O box 12, Rehovot 76100, Israel

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* Corresponding author. Tel.: +972 3 9888550

E-mail address: [email protected] (J. Milgram).

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Fax: +972 3 9688525

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ACCEPTED MANUSCRIPT Abstract The aim of this study was to develop a minimally invasive thyroarytenoid lateralization

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technique (MITAL). Eleven unilateral MITAL procedures were performed on 11 canine

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cadavers. Two hypodermic needles were passed through the skin into the lumen of the larynx, penetrating the thyroid and arytenoid cartilages. Suture material was passed through the needles

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to lateralize the arytenoid cartilage. A rigid endoscope was used to visualize needle insertion and

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suture material placement. A key-hole approach to the larynx was performed and the suture material was knotted on the lateral aspect of the thyroid cartilage. The change in the rima

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glottidis area was recorded as were the duration of the procedure and complications encountered.

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The landmarks for needle insertion were easily palpated. A significant increase in the

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area of the rima glottidis was documented after performing unilateral MITAL. In conclusion, unilateral MITAL is a quick, minimally invasive procedure which increases the area of the rima glottidis in cadaveric dogs.

Keywords: Arytenoid cartilage Lateralization; Laryngeal Paralysis; Minimally-Invasive; Dog; Surgery.

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ACCEPTED MANUSCRIPT Introduction Laryngeal paralysis results in partial or complete loss of the ability of the arytenoid

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cartilages to abduct during inspiration (Bjorling, 1995; Hedlund, 2002; White, 1989). Although a

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congenital form of the disease is reported, the acquired form is the more common, affecting

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middle-aged to older large and giant breed dogs (Greenfield, 1987; Holt and Harvey, 1994; MacPhail and Monnet, 2001; White, 1989). Multiple etiologies are associated with laryngeal

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paralysis; however, in cases of idiopathic laryngeal paralysis (Gaber et al., 1985; MacPhail and

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Monnet, 2001; Ridyard et al., 2000), it has been shown that degeneration of the recurrent laryngeal nerves lead to atrophy of the intrinsic abductors of the larynx that are critical for

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normal function (Thieman et. al. 2010). Affected animals present with a wide variety of clinical

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signs including change in phonation, stridor, coughing (especially during eating and drinking),

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exercise intolerance, and respiratory distress (Gaber et al., 1985; White, 1989).

Surgery is indicated in dogs with moderate to severe clinical signs or decreased quality of life. The aim of surgical treatment is to decrease laryngeal resistance by manipulating laryngeal tissues that obstruct the rima glottidis during inspiration (Monnet and Tobias, 2012). Multiple techniques have been described, of which the most common include unilateral (MacPhail and Monnet, 2001; White, 1989) and bilateral arytenoid lateralization (Burbidge et al., 1993; Rosin and Greenwood, 1982), bilateral thyroarytenoid lateralization (Monnet and Tobias, 2012), vocal fold excision and mucosoplasty (Schofield et al., 2007), vocal fold resection (Ridyard et al., 2000), partial laryngectomy (Harvey and O’Brien, 1982; Ross et al., 1991) and castellated laryngofissure (Gourley et al., 1983). The method of choice is unilateral cricoarytenoid

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ACCEPTED MANUSCRIPT lateralization (Hedlund, 2002), however, in a previous report, there was no difference in clinical

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outcome between crico- and thyroarytenoid lateralization (Griffiths et al., 2001).

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The superficial location of the larynx, the location of the arytenoid cartilage medial to the thyroid cartilage and the ability to visualize the lumen of the larynx, favor the development of

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minimally invasive techniques for unilateral thyroarytenoid lateralization. The aims of this study

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were to develop a minimally invasive thyroarytenoid lateralization (MITAL) technique, and to

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evaluate a safe corridor for the placement of the prosthesis in canine cadavers.

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Materials and methods

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The procedure described herein is a modification of the open thyroarytenoid technique (Rosin and Greenwood, 1982), in which the arytenoid cartilage is sutured to the thyroid cartilage,

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resulting in arytenoid cartilage lateralization. Eleven canine cadavers free of laryngeal or pharyngeal pathology, euthanized for unrelated reasons, were used. Dogs were refrigerated (5°C) immediately after euthanasia and the procedure was performed within 48 hours.

A 10 mm, 15° rigid endoscope attached to a light source, camera, and monitor (Karl Stortz, Germany) was used. Video data were captured on a digital storage device (SDC HD, Stryker) and analyzed using Videopad Video Editor Software.1 Individual images were captured from the video using the Videopad software and used to determine the area of the rima glottidis prior to, and following the procedure.

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See: http://www.nchsoftware.com/videopad/index.html 4

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Surgical procedure Eleven unilateral MITAL procedures were performed on 11 canine cadavers. MITAL

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was performed on the right side in all cadavers; and is illustrated in an isolated larynx in Fig. 1.

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The hair on the ventral and lateral aspect of the neck was clipped. Dogs were placed in ventral

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recumbency, with the head extended and lifted off the table with a loop of gauze bandage passed caudal to the maxillary canine teeth as described for soft palate resection (Richard, 2006). The

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endoscope was passed into the oropharynx until the entire rima glottidis was visible. A gingival probe with millimeter markings was advanced and placed cranial to the corniculate processes to

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provide scaling. The probe was removed and an endotracheal (ET) tube, with a diameter that did

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not extend dorsal to the junction of the vocal fold and the arytenoid cartilage, was placed.

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Two, 1.5 inch, 18 gauge needles were inserted, percutaneously, into the laryngeal lumen from the right. The first needle was advanced through the skin, parallel to the floor, from lateral to medial, until it entered the laryngeal lumen after penetrating the thyroid and arytenoid cartilages. In a pilot study completed prior to this study, it was determined that the needles must penetrate the lateral aspect of the thyroid cartilage, craniodorsally, in order to pass into the lumen of the larynx while engaging both thyroid and arytenoid cartilages. Ideally, both needles should pass through the craniodorsal aspect of the thyroid cartilage as depicted in Fig. 2. The craniodorsal aspect of the thyroid cartilage is caudal to the cranial horn, ventral to the dorsal border, and caudal to the cranial border of the thyroid cartilage. The craniodorsal aspect can be found by palpating the space between the thyrohyoid cartilage and the cranial border of the

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ACCEPTED MANUSCRIPT lateral lamina of the thyroid cartilage. The dorsal aspect of this space is closed by the attachment of the thyrohyoid cartilage to the cranial horn of the thyroid cartilage.

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The desired location of needle penetration of the arytenoid cartilage was caudal to the

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intersection of the dorsal aspect of the vocal fold and the arytenoid cartilage (Fig 3). The needle

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was considered to be placed incorrectly if it was located cranial to the intersection of the vocal fold and the arytenoid cartilage and penetrated the laryngeal ventricle, if it was located in the

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vocal fold ventral to the arytenoid cartilage, or if it exited the thyroid cartilage and could be seen

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crossing the piriform recess from lateral to medial prior to penetrating the arytenoid cartilage. The second needle was placed into the laryngeal lumen using an identical technique in a location

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either dorsal or caudal to the first needle, depending on the exit point of the first needle.

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Monofilament nylon (2/0, Monosof, Covidien) was passed into the laryngeal lumen via one of the needles and out of the laryngeal lumen via the second needle. The intraluminal manipulation of the suture material was performed using a laparoscopic forceps (Maryland laparoscopic dissection forceps, Karl Storz) under endoscopic guidance. Each needle was removed immediately after the suture material was passed to prevent damage to the suture material by the bevel of the needle. The two free ends of suture material, exiting the skin, were then tied temporarily. The endotracheal tube was removed and the gingival probe was placed as before. The time taken to place the suture material (suture placement time) was measured from the removal of the gingival probe prior to the procedure, to its placement following the procedure.

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ACCEPTED MANUSCRIPT Potential damage to neighboring structures was evaluated in the first 6 dogs. In these dogs, a dissection of the lateral aspect of the larynx was performed to determine the exact path of

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the suture material. Prior to performing the dissection, the suture material was untied. The

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dissection was performed through a 15 cm skin incision dorsal to the exit points of the suture material. The dissection was considered complete when the suture material was visualized

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exiting the thyroid cartilage and passing through the skin incision without any intervening soft

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tissue. The nylon suture material was then tied firmly on the lateral aspect of the thyroid cartilage. Vital structures compromised by the placement of the suture material were noted. To

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evaluate the change in the area of the rima glottidis after tying the suture material the identical procedure was used to visualize the rima glottidis with the gingival probe cranial to the

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corniculate processes.

In the remaining 5 dogs, an identical procedure was performed, however, the lateral aspect of the thyroid cartilage was exposed via a key-hole approach to facilitate tying of the suture material on the lateral aspect of the thyroid cartilage. A 3 cm skin incision, parallel to the jugular vein, was made dorsal to the suture material exiting the skin. The suture material was pulled through the skin incision as before and blunt dissection was used to expose the thyroid cartilage. Once all intervening soft tissue had been removed, the suture material was knotted using a square knot on the thyroid cartilage. Any vital structure compromised during the heyhole approach was noted.

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ACCEPTED MANUSCRIPT Complications were classified as major when they required a revision of the procedure or when damage to a vital structure occurred. Complications which did not necessitate revision of

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the procedure or damage to a vital structure were considered minor complications.

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Procedure time was defined as the time from the introduction of the endoscope until the

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tying of the knots on the thyroid cartilage.

Finally, the larynx was removed en bloc with the surrounding musculature and

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esophagus, in all dogs, via a ventral approach. Soft tissues were carefully removed and the thyroid cartilage was disarticulated from the cricoid cartilage to confirm the location of the

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fracture of the cartilage.

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suture material and to document compromise to any of the peri-laryngeal structures as well as

One video file was available for each procedure. Time measurements were not obtained in the first two procedures. Two still images, depicting the entire periphery of the rima glottis and the gingival probe, were captured from each video for measurement of the area of the rima glottidis. One image was captured prior to placing the endotracheal tube and a second image was captured after tying the suture material (Fig. 4). The area of the rima glottidis was determined using ImageJ software.2 The periphery of the rima glottidis was marked, and the area defined within the periphery was calculated before and after the procedure to evaluate the effect of the procedure (Fig. 4)

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See: http://rsbweb.nih.gov/ij/ 8

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Data analysis Data are presented as median and range. The rima glottidis area prior and post procedure

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were compared using the Wilcoxon Signed Ranks test. The Shapiro Wilk test was used to assess

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normality of continuous parameters. Analysis was performed using statistical software (SPSS 17

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for Windows, Chicago, IL, USA). P < 0.05 was considered statistically significant.

Results

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Cadavers were mixed breed dogs with a median body weight of 33.0 kg (range 15-40 kg).

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The landmarks for needle insertion were palpated without difficulty in all dogs. There was a

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large subjective variation in the amount of force needed to place the needles into the lumen of the larynx. Once the thyroid cartilage had been penetrated, a second resistance was felt as the needle contacted and penetrated the arytenoid cartilage. At this stage movement of the arytenoid cartilage could be seen endoscopically.

The median duration of suture material placement was 9:46 min (range 4:21-20:19 min, n=9) while the median procedure time was 11:00 min (range 9:30-15:30 min, n=4).

Change in area of the rima glottis was measured in 10 procedures (data for one procedure were lost). The area of the rima glottidis was significantly increased following the procedure (P

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ACCEPTED MANUSCRIPT <0.005). The median increase in rima glottidis area following the procedure (Fig. 5) was 4.9 fold

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(range 1.8-7.8 fold).

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Complications

Major complications associated with laryngeal suture placement included jugular vein (or

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one of its branches) penetration in one case (9.1%) and accidental cutting or breakage of the suture material (3/11 procedures, 27.3 %). The suture material was cut with the scalpel blade

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during the dissection in the keyhole approach in 2 of the cases and broke when knotting the suture in one case. Penetration of the endotracheal tube while placing the suture material in the

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larynx occurred in 2/11 procedures (18.2%) and was considered a minor complication.

The suture material was confirmed to penetrate the cranio-dorsal aspect of the lateral lamina of the thyroid cartilage and pass through the arytenoid cartilage in all but one procedure (9.1%). In this procedure, both needles were inserted cranial to the thyroid cartilage, and the typical “double resistance” was not felt while inserting the needles through the laryngeal cartilages, however, lateralization of the arytenoid cartilage still occurred.

Discussion This study describes a modification of the unilateral thyroarytenoid lateralization technique, in which the suture prosthesis is placed percutaneously. This procedure is short and minimally invasive and resulted in significant increase in the area of the rima glottidis. A 10

ACCEPTED MANUSCRIPT procedure resembling MITAL has been described in humans for treating vocal cord paralysis (Lichtenberger, 1999).

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Unilateral MITAL resulted in abduction of the arytenoid cartilage and a significant

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increase in the area of the rima glottidis. In order to reduce the risk of aspiration pneumonia, only

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a moderate abduction of the arytenoid cartilage is advised (Greenberg et al., 2007). Unfortunately, we did not quantify the tension placed on the suture prior to tying it and as a

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result we increased the area of the rima glottidis a median of 4.9 fold. Good clinical results were

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reported with an increase in rima glottidis area of approximately 250% (Demetriou and Kirby 2003) and 140% (thyroarytenoid) and 207% (cricoarytenoid) (Griffiths et. al. 2001). In light of

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our findings we would recommend tensioning and tying of the suture under direct endoscopic

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visualization to achieve an increase in the area of the rima glottis of between 200% and 250%.

Up to 16 minutes were required to perform a unilateral MITAL on a canine cadaver, which compares favorably with the time reported for other “tie back” techniques (Griffiths et al., 2001; Schofield et al., 2007), however, performing this procedure on a clinical case is expected to exceed this time until experience is gained.

The use of an ET tube is advised with any procedure performed under general anesthesia. In this procedure, though it interferes with visualization, the ET tube opens the rima glottidis, facilitating suture placement. The ET tube diameter used in this study was considerably smaller than the recommended diameter, which might interfere with ventilation; however, use of a smaller size ET tube or extubation can be performed during needle placement with reintubation 11

ACCEPTED MANUSCRIPT using an appropriately sized ET tube immediately after suture placement. Penetration of the ET tube occurred in 2/11 procedures with the use of a small diameter ET tube. The incidence of this

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complication is expected to increase if a larger diameter ET tube is used. This complication

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occurred mainly in the earlier cases and with experience this minor complication was avoided.

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Penetration of one of the major superficial veins draining the head with the needle occurred in one procedure. This is likely due to the inability to identify the veins by occluding

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and dilating them in a cadaver. In a clinical case the location of the jugular vein and its branches is easily determined and avoided. Hemorrhage resulting from inadvertent puncture of one of the

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veins could be controlled with digital pressure, however, in the event of excessive bleeding,

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ligation may be required (Phillips and Aronson, 2012). Hemorrhage may also obscure the

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surgical field in those cases in which the procedure has to be converted into an open one; however, as the hemorrhage is generally superficial, this is unlikely to significantly affect the surgical approach.

When the needles are advanced, a double resistance is felt as they pass through the lateral lamina of the thyroid cartilage and the arytenoid cartilage. This is a good indication that both cartilages have been penetrated. Although the landmarks were readily palpable in all cadavers, in one of the procedures, the needles were incorrectly placed as they did not penetrate both the thyroid and arytenoid cartilages. Tying the suture material substantially abducted the arytenoid cartilage, in this procedure and the rima glottis area was larger compared to its area prior to the procedure. It is critical, however, that the needles pass through both laryngeal cartilages in order 12

ACCEPTED MANUSCRIPT to achieve a long term, stable suture. Abduction on its own is not a measure of the success of the procedure as this will occur even in incorrectly placed suture. The location of the vocal process

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can be estimated as lying caudal to the proximal aspect of the vocal fold. Needles exiting the

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laryngeal ventricle or the vocal fold can be assumed to have missed the arytenoid cartilage, the

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thyroid cartilage or both, and should be re-inserted.

Suture breakage during the procedure, necessitating a repeat procedure, was the most

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common complication in our study and occurred in 3/11 procedures. A contributing factor is damage to the suture material by the beveled point of the needle, therefore, we recommend using

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a sufficiently long length of suture material so that the knot can be tied in an area of the suture

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material which did not pass through the needles. In addition, we recommend pulling out the

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needle immediately after passing the suture material to prevent damage to the suture material. Alternatively, an 18G trocar and pointed cannula may be used to avoid damage to the suture material. In addition, during the approach, care must be taken not to cut the suture material and sharp dissection should be avoided. Once the skin is incised only blunt dissection guided by the direction of the suture material is required to expose the lateral aspect of the thyroid cartilage.

Canine cadavers have been used in many previous studies evaluating the effectiveness of various techniques of unilateral arytenoid lateralization (Bureau and Monnet, 2002; Lussier et al., 1996; Weinstein and Weisman, 2010). The advantages of MITAL are it's minimally invasiveness, simplicity and reduced procedure time, however, the procedure as described is performed with the aid of an endoscope. An added advantage is that MITAL can be performed in 13

ACCEPTED MANUSCRIPT an emergency setting, in which the suture material can be placed through the arytenoid cartilage and tied on the skin without the described keyhole approach. This will temporarily abduct the

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arytenoid cartilages until a definitive procedure can be performed.

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The authors of this study routinely perform unilateral cricoarytenoid lateralization for

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cases of idiopathic laryngeal paralysis with excellent clinical outcome. However, we believe this procedure can be improved by limiting the dissection required to expose the deep structures of

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the larynx. During the approach branches of the internal division of the cranial laryngeal nerve are encountered and if compromised will affect the sensory innervation of the larynx. The extent

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to which this occurs, and effect on postoperative complications, is unknown.

We have shown that the arytenoid cartilage can be lateralized without the need for dissection of the deep structures of the larynx. Our technique involves some dissection, however, we consider a “key-hole” approach to a superficial structure such as the lateral aspect of the thyroid cartilage to be minimally invasive when compared to the dissection required to expose the deep structures of the larynx. We believe that the minimal invasive nature of the procedure will decrease the amount of surgical trauma, as well as the morbidity and complication rate associated with the procedure.

There are several limitations to this study. This is a cadaveric study so no conclusions can be drawn as to the effectiveness of this technique in clinical cases. In addition we used dogs

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ACCEPTED MANUSCRIPT with a large weight variation, and some of the cadavers were not representative of cases generally seen in practice. The study is also limited in that we did not measure the effect of the

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procedure on airway resistance. The emphasis of this study was to show that the technique when

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performed as described will result in an increase in the area of the rima glottidis. The study would have been enhanced if the effect of suture tension on rima glottis area and airway

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resistance would have been measured. However, these studies are best performed on an isolated

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larynx rather than in situ.

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No attempt was made to quantify the suture tension during the procedure. During the procedure sutures were tied firmly on the lateral aspect of the thyroid cartilage which resulted in

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excessive lateralization of the arytenoid cartilage. The technique can be easily modified to allow

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direct visualization of the rima glottidis during the tying of the suture to achieve the

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recommended moderate lateralization to reduce the risk of aspiration pneumonia. Fracture of the laryngeal cartilages between the needles was not documented in this study but remains a concern. Aiming the needles to penetrate the laryngeal cartilage at different locations is recommended. Although beyond the scope of the study, multiple attempts to place a needle correctly may also weaken the laryngeal cartilage resulting in fracture of the cartilage and failure of the procedure, especially in old dogs in which the laryngeal cartilages may be calcified.

The loop of suture material exposed in the laryngeal lumen on the surface of the mucosa is also a concern, however, only a small piece of suture material is left exposed, and the clinical significance is yet to be determined. It is the authors’ opinion that in time, the suture material will become buried under the mucosa, as seen with intraluminal stents that are placed into the 15

ACCEPTED MANUSCRIPT upper airways of dogs (Tsukada et al., 2009). Alternatively, potential complications can be avoided by burying the suture material by incising the mucosa between the two needles

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endoscopically.

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MITAL is minimally invasive and requires a thorough knowledge of the laryngeal

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anatomy. Careful palpation is required to identify the space between the thyrohyoid cartilage and the thyroid cartilage as well as dorsal border of the thyroid cartilage. Time should be spent

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familiarizing oneself with the anatomy, as described, before attempting a MITAL. If the landmarks cannot be palpated (e.g. obese dogs), the procedure is contraindicated. Additional

Conclusions

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contraindications include inter-arytenoid ankylosis and laryngeal chondromalacia.

MITAL is a quick, minimally invasive procedure which successfully increases the area of the rima glottidis in cadaveric dogs. Further evaluation is needed to assess whether this technique can serve as an alternative to conventional surgical procedures for the treatment of dogs displaying clinical signs related to laryngeal paralysis.

Conflict of interest statement None of the authors has any financial or personal relationships that could inappropriately influence or bias the content of the paper.

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ACCEPTED MANUSCRIPT

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Acknowledgements Preliminary results were presented as an Abstract at the 22nd European College of

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Veterinary Surgeons annual scientific meeting, Rome, Italy, 4th-6th July 2013 and as an abstract

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at the American College of Veterinary Surgeons veterinary symposium, San Antonio, USA,

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24th-26th October 2013

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ACCEPTED MANUSCRIPT References Bjorling, D.E., 1995. Laryngeal paralysis, in: RW, K. (Ed.), Current Veterinary Therapy, XII ed.

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Burbidge, H.M., Goulden, B.E., Jones, B.R., 1993. Laryngeal paralysis in dogs: An evaluation of the bilateral arytenoid lateralisation procedure. Journal of Small Animal Practice 34, 515-519.

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Bureau, S., Monnet, E., 2002. Effects of suture tension and surgical approach during unilateral arytenoid

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lateralization on the rima glottidis in the canine larynx. Veterinary Surgery 31, 589-595. Demetriou, J.L., Kirby, B.M., 2003. The effect of two modifications of unilateral arytenoid lateralization

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Gaber, C.E., Amis, T.C., LeCouteur, R.A., 1985. Laryngeal paralysis in dogs: a review of 23 cases.

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Gourley, I.M., Paul, H., Gregory, C., 1983. Castellated laryngofissure and vocal fold resection for the

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Griffiths, L.G., Sullivan, M., Reid, S.W., 2001. A comparison of the effects of unilateral thyroarytenoid lateralization versus cricoarytenoid laryngoplasty on the area of the rima glottidis and clinical outcome in dogs with laryngeal paralysis. Veterinary Surgery 30, 359-365. Harvey, C.E., O’Brien, J.A., 1982. Treatment of laryngeal paralysis in dogs by partial laryngectomy. Journal of the American Animal Hospital Association 18, 551-556. Hedlund, C.S., 2002. Surgery of the upper respiratory system in: Fossum, T.W. (Ed.), Small Animal Surgery, II ed. Mosby, St. Louis, MO. 18

ACCEPTED MANUSCRIPT Holt, D., Harvey, C., 1994. Glottic stenosis secondary to vocal fold resection: results of scar removal and corticosteroid treatment in nine dogs. Journal of the American Animal Hospital Association 30, 396-400.

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Lichtenberger, G., 1999. Reversible immediate and definitive lateralization of paralyzed vocal cords. Eur Arch Otorhinolaryngol 256, 407-411.

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surgical treatment of laryngeal paralysis: 140 cases (1985-1998). Journal of the American Veterinary

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ACCEPTED MANUSCRIPT Thieman, K.M., Krahwinkel, D.J., Sims, M.H., Shelton, G.D., 2010. Histopathological Confirmation of Polyneuropathy in 11 Dogs With Laryngeal Paralysis. Journal of the American Animal Hospital

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Association 46, 161-167.

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Tsukada, H., Matsuda, S., Inoue, H., Ikada, Y., Osada, H., 2009. Comparison of bioabsorbable materials for use in artificial tracheal grafts. Interactive Cardiovascular and Thoracic Surgery 8, 225-229.

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White, R.A.S., 1989. Unilateral Arytenoid Lateralization - an Assessment of Technique and Long-Term

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Results in 62 Dogs with Laryngeal Paralysis. Journal of Small Animal Practice 30, 543-549.

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ACCEPTED MANUSCRIPT Figure Legends: Figure 1: Isolated larynx showing the technique used to perform the percutaneous

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thyroarytenoid lateralization procedure. A. Placement of the first 18G hypodermic needle (white

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arrowhead) through the right lateral aspect of the thyroid cartilage and the arytenoid cartilage

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into the lumen of the larynx. B. Placement of the second needle dorsal to the first needle. C. Placement of 2/0 nylon suture material through the needles (white arrow). D. Knotting the suture

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cartilage and opening of the rima glottidis.

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material adjacent to the thyroid cartilage, which results in abduction of the ipsilateral arytenoid

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Figure 2: Lateral view of the larynx of a dog. The two dots indicate the location at which the needles should penetrate the thyroid cartilage. (Modified from Miller’s anatomy of the dog. 4th

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edition (Reprinted with permission).

Figure 3: Endoscopic image of the rima glottidis showing with the ideal location of needle penetration of the vocal process marked with a white arrow head.

Figure 4: Three images of the larynx captured from the video recorded via the rigid endoscope. The dental probe can be seen cranial to the rima glottidis in all images. A: An image of the cranial aspect of the larynx prior to performing unilateral MITAL. B: An image of the cranial aspect of the larynx after performing MITAL on the right. C, D: Identical images indicating the area used to calculate the area of the rima glottidis (marked in black). The images were 21

ACCEPTED MANUSCRIPT calibrated, the periphery of the rima glottidis was marked and the area defined was filled and

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calculated using ImageJ software.

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Figure 5: Box and whisker depicting the increase in rima glottidis area following unilateral

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MITAL. The horizontal line within the box represents the median. The gray box represents the interquartile range (2nd and 3rd quartiles) and the whiskers represent the range and the circle

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Fig. 1

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Fig. 3

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Fig. 4

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Fig. 5

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ACCEPTED MANUSCRIPT Highlights  A minimally invasive thyroarytenoid lateralization (MITAL) in canine cadavers is described. Suture material is inserted percutaneously through 2 needles, into the laryngeal lumen

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A rigid endoscope is used to assess proper suture placement.

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Suture material is tied directly on the thyroid cartilage through a key-hole approach.

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A significant increase in rima-glottidis was demonstrated after tying the suture.

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