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Surgical Impact of the Montgomery Implant System on Arytenoid Cartilage and the Paralyzed Vocal Fold
ARTICLE IN PRESS
Surgical Impact of the Montgomery Implant System on Arytenoid Cartilage and the Paralyzed Vocal Fold 1
€ thi, Flurin Honegger, and Fabian Unteregger, Basel, Switzerland Claudio Storck, 1Martin Lu Objectives/Hypothesis. Medialization thyroplasty (MT) has become a prominent method for treating glottal insufficiency. This study aimed to visualize the biomechanical influence of a medialization implant on arytenoid cartilage, particularly on the length and level of paralyzation in the vocal fold, in patients with unilateral vocal fold paralysis. Study Design. Prospective study. Methods. We recruited 15 patients (10 men, 5 women) with unilateral vocal fold paralysis that underwent MT Ò with a Montgomery thyroplasty implant. We performed high-resolution computed tomography of the arytenoid cartilage before and after MT and analyzed the three-dimensional images. To visualize the movement of the arytenoid and to measure the lengthening of the vocal fold, we superimposed pre- and postoperative 3D images with MIMICS software. Results. On the affected side, the implant pushed the arytenoid backwards. In addition, the vocal process of the arytenoid was inwardly rotated. These movements resulted in an elongated, augmented vocal fold on the affected side. Conclusion. MT led to an elongated, medialized vocal fold on the treated side. After the intervention, the vocal folds on both sides were the same length in the phonatory position. Key Words: Larynx 3D Montgomery MIMICS Unilateral vocal fold immobility Arytenoid cartilage.
TAGEDH1INTRODUCTIONTAGEDN Unilateral vocal fold paralysis (UVFP) often leads to dysphonia as the main symptom. Insufficient glottal closure results in a membranous gap with asymmetric vocal folds. The size of this gap determines the degree of vocal complaints.1 Various methods have been developed to restore glottal closure, eg, an injection laryngoplasty, medialization thyroplasty (MT), arytenoid adduction (AA), arytenoidopexy (AP), or muscle reinnervation. However, MT is one of the dominant methods for treating glottal insufficiency.2,3 This method is safe and simple. Several previous studies have demonstrated the many postoperative benefits of MT, including improvements in voice quality, swallowing impairments, and breathlessness.4-6 MT can be performed with different implant materials (eg, thyroid cartilage, silasÒ tic, goretex , titanium, hydroxylapatite, or different injectables), with all different advantages and disadvantages. For the latter, we refer to the literature. Development of the Ò Montgomery Thyroplasty Implant System (MTIS), by Montgomery and Montgomery,7 has contributed to standardizing the MT intervention. Accepted for publication July 13, 2018. Presented at The Voice Foundations 45th Annual Symposium, June 3, 2017, Philadelphia, USA, Winner of the Hamdan Award 2017. Financial disclosure: No. Conflict of interest: No. Level of evidence: 4. From the Department of Otorhinolaryngology, Head and Neck Surgery, Division of Phoniatrics, University Hospital Basel, Basel, Switzerland. 1 Equal co-authors. Address correspondence and reprint requests to Claudio Storck, Department of Otorhinolaryngology, Head and Neck Surgery, Division of Phoniatrics, University Hospital Basel, Petersgraben 4, 4031 Basel, Switzerland. E-mail: [email protected] Journal of Voice, Vol. &&, No. &&, pp. 1 5 0892-1997 © 2018 The Voice Foundation. Published by Elsevier Inc. All rights reserved. https://doi.org/10.1016/j.jvoice.2018.07.019
Patients with UVFP display an inward-rotated arytenoid; thus, the vocal process is inferior to that on the non-paralyzed side. The vocal fold is excavated, due to reduced tension, and the level is lowered. Therefore, restoring the voice requires achieving glottal closure, restoring the length, and raising the vocal fold level. It is assumed that the MT has some limitations, particularly in patients with a wide posterior glottal gap and/or differences in the vertical levels of the vocal folds.3,8,9 Therefore, many authors recommend performing an AA or AP, in addition to an MT.2,8 Both techniques alter the position of the arytenoid. This repositioning leads to better closure of the posterior glottis and an optimized position/level of the vocal fold, which results in a better voice outcome.2,8 Nevertheless, the functional voice outcome is controversial, compared to the higher morbidity related to exposing the arytenoid cartilage.2,8,9 To date, no studies have analyzed the length in the vocal fold induced by MT, with or without additional AA/AP. Due to this lack of evidence, it remains unclear how the level and the length of the paralyzed vocal fold might be influenced by MT with the MTIS. Two-dimensional endoscopy is a common approach for examining the vocal folds pre- and postoperatively. However, this approach has some limitations in visualizing the level of the vocal fold and estimating the vertical movements of the arytenoid and vocal folds.10 Investigations with high-resolution computed tomography (HRCT) offer a three-dimensional view. With HRCT, the influence of the medialization implant on the arytenoid cartilage can be evaluated and quantitatively measured. Therefore, the present study aimed to perform HRCT to visualize the biomechanical influence of the MTIS on the
ARTICLE IN PRESS 2
Journal of Voice, Vol. &&, No. &&, 2018
arytenoid cartilage, particularly on the elongation of the paralyzed vocal fold. T ATERIALS AND METHODSTAGEDN AGEDH1M Study population Between 2015 and 2016, a total of 15 patients (10 men, 5 women) with UVFP (9 on the left side, 6 on the right side) underwent a type I MT with the MTIS at the University Hospital of Basel, Switzerland. The UVFP was caused by a bronchial carcinoma in nine patients, meningioma surgery in two patients, vagus neurinoma surgery in two patients, and a reconstruction of the aortal branch in two patients. The mean age was 63 (range: 48 77) years. All patients underwent pre- and postoperative videoendostroboscopies. In addition, all patients underwent an HRCT of the larynx, 1 day before surgery and 2 days after surgery (details described in Section 2.2). All procedures were performed in the operation room under local anesthesia by the same surgeon (C.S.). After preparing the thyroid ala, the window was cut out of the thyroid ala and the inner perichondrium was undermined. Different precast sizers were used to find out the right size. The implant was placed without use of endoscopic control. The study was approved by the Medical Ethics Committee of the University of Basel, Switzerland. HRCT imaging HRCT of the larynx was performed 1 day before surgery and 2 days after surgery on a Siemens Healthcare Scanner (Zurich, Switzerland). We used the following parameters: 100 kV and 203 mA; slice thickness: 1.5 mm; radiation dosage: 1.2 mSv; and length product: 182 mGy cm. During the scan, patients were asked to sing or act as if singing in their own middle speaking frequency; this activity moved the non-paralyzed vocal fold into the phonation position. Postprocess imaging To discern the laryngeal structures, we converted the HRCT data to digital imaging and communications in medicine data and transferred them to the postprocess imaging software, MIMICS 14.0 (Version 14.0, Materialise, Leuven, Belgium). Then, we created 3D images of the larynx. To visualize the movement of the arytenoid and to measure the lengthening of the vocal fold, the pre- and postoperative 3D images were superimposed (Figure 1, compound movement). To calculate the vocal fold length, we defined the anterior commissure and the vocal process of the arytenoid cartilage as landmarks in the three-dimensional pre- and Ò postoperative images. MIMICS then calculated the distances between landmarks. All statistical analyses and comparisons of vocal fold length data were performed with Matlab R2017a, and the version that corresponded to Statistics Toolbox. Significance testing was performed with the paired t test, for means, and with the Wilcoxon rank sum test, for medians.
FIGURE 1. Representative 3D reconstructions show movements of the cricoid cartilage and the arytenoid cartilage with the MT procedure. (A) Superior views, (B) anterior views, and (C) lateral views show the preoperative (green) and postoperative (yellow) positions of the arytenoid. (Right column) Superimposed 3D scans of the pre- and postoperative positions of the arytenoid; (black arrows) the movement of the arytenoid. Black points = vocal process. The arytenoid was rotated medially and pushed posterosuperiorly by the Montgomery implant (white).
T ESULTSTAGEDN AGEDH1R Videoendostroboscopy With preoperative videoendostroboscopy, we could observe an excavated paralyzed vocal fold in intermediate position including insufficient glottal closure, anterior tilting of the arytenoid cartilage, and a lowered vocal fold in 15/15 patients. Postoperatively, all patients achieved complete glottal closure and straightening of the paralyzed vocal fold. The paralyzed vocal fold seemed to be at the same level as the non-paralyzed vocal fold.
Elongation of the vocal fold The paralyzed vocal fold was significantly elongated by up to 20.6% (P = 0.00003), from the mean preoperative length of 17.6 mm (range: 11.8 23.0 mm) to the mean postoperative length of 21.1 mm (range: 15.1 27.0 mm). In addition, in 10/15 patients, the non-paralyzed vocal fold was significantly elongated, by 1.0% (P = 0.015), from a mean of 20.9 mm (range: 14.3 26.8 mm) preoperatively to a mean of 21.1 mm (range: 14.5 27.6 mm) postoperatively. Thus, the two vocal folds were the same length postoperatively in the phonatory position (Table 1,Figure 2).
Movement of the arytenoid cartilage The reconstructed 3D images showed that the MTIS pushed the arytenoid backwards, up onto the cricoidal facet, in 15/ 15 patients. This backward sliding leads to a posterior and superior movement of the vocal process. Additionally, the
ARTICLE IN PRESS Claudio Storck, et al
3
Montgomery Implant influences vocal fold length and position
TABLE 1. Influence of the MTIS on the Length of the Vocal Folds (VF) Mean lengths (mm) of the vocal folds before and after the MTIS intervention Preoperative Postoperative
Paralyzed VF Non-paralyzed VF
Elongation
Mean
SD
Mean
SD
P
Mean [range]
% [range]
17.6 20.9
3.0 3.5
21.1 21.1
3.5 3.6
0.00003 0.015
3.5 [2.9, 4.5] 0.2 [0.04, 0.37]
20.6 [17.0, 24.9] 1.0 [0.17, 1.62]
MTIS led to an inward rotation of the vocal process of the arytenoid cartilage. These movements (backward push and inward rotation) led to a backward, upward movement of the vocal process. This resulted in vocal fold elongation. In addition, the vocal fold was medialized at a higher level. In our 3D reconstructions of the cricoid and arytenoids, it was possible to visualize the same level of the vocal process of the paralyzed vocal fold to the vocal process of the non-paralyzed vocal fold (Figure 1).
TAGEDH1DISCUSSION AND CONCLUSIONTAGEDN MT has become one of the dominant methods for treating glottal insufficiency in cases of dysphonia, due to UVFP.1 The position of the paralyzed vocal fold in patients with UVFP has been intensely studied, during both phonation and respiration. Deviations in the horizontal plane are typically classified as median, paramedian, intermediate, or lateral positions.11 However, differences in the vertical plane can also occur on the paralyzed side; these changes are more complex to investigate. The vertical gap between the paralyzed and the innervated vocal folds remains an issue of
FIGURE 2. Pre-to-postoperative changes in vocal fold length. (Left) Changes in the paralyzed vocal fold lengths on the treated side indicate a net increase with treatment, as intended; (right) changes observed on the untreated side. (Grey lines) Lines indicate the preoperative to postoperative values for each individual. Both the treated and untreated sides show a significant increase in the median and mean values, although the change is small on the untreated side. ***P < 5 £ 10¡5; *P < 0.05.
controversy. However, most studies assume that the level of the vocal fold on the affected side is lower than the level of the vocal fold on the healthy side.12-14 Nevertheless, many parameters were shown to influence the position of the paralyzed arytenoid cartilage, including the severity of paralysis, the shape of the arytenoid, and the sex and age of the patient.12,15 Moreover, the type of cricothyroid joint also seems to play an important role in the elongation of the vocal fold.16,17 Interestingly, we did not find any studies that analyzed the length of the vocal fold induced by medialization, with or without additional AA/AP. A further study investigating the influence of vocal fold injection onto the position of the arytenoid showed a combination of medial rotation and medial translation movement of the arytenoid after intervention. They also did not observe a movement in the coronal plane, but interpret both movements as components of a rocking motion, without analyzing the specific influence onto the vocal process and thus on the height and length of the vocal fold.18 Thus, it was unclear whether the level of the affected vocal fold could be influenced by MT with the MTIS, and if so, by what mechanism. The purpose of the present study was to investigate the biomechanical influence of the MTIS on the elongation and level of the paralyzed vocal fold. We used the software package, MIMICS, to superimpose 3D images of the larynx to visualize the movement of the arytenoid cartilage on the shoulder of the cricoarytenoid facet. Due to the Montgomery implant, the arytenoid cartilage was pushed posterior and upwards, which resulted in a backward, upward movement of the vocal process. On one hand, postoperative measurements showed that the paralyzed vocal fold was significantly elongated, by about 20.6%. On the other hand, the paralyzed vocal fold could be medialized and raised to nearly the same level as the untreated vocal fold. We measured the length of the contralateral, untreated vocal fold to compare the lengths of both vocal folds postoperatively. Interestingly, we found that the untreated vocal fold was significantly elongated, by an average of 0.2 mm. Consequently, the two vocal folds were the same length postoperatively. Regarding the vertical gap between the paralyzed and the innervated vocal fold, there is still controversy in literature: Some studies suppose that during inspiration, the level of the vocal fold on the healthy side is higher compared to the paralyzed side, due to a rocking movement of the arytenoid
ARTICLE IN PRESS 4 on the non-paralyzed side. During phonation, the paralyzed arytenoid can perform a passive gliding movement cranially, resulting in a higher level of the paralyzed vocal fold, compared to the healthy side. It is assumed that this phenomenon is, first, caused by contact with the non-paralyzed arytenoid during phonation and, secondly, by expired air.12,13 In these cases, AA is often recommended to medialize the paralyzed vocal fold and correct the difference in fold levels by lowering the paralyzed vocal fold.2 This, however, is also subject of a controversial discussion: On the one hand, former studies, which evaluated if AA in addition to MT yields better posterior closure and vertical height equality than MT alone, showed no significant additional benefit of AA compared to MT alone.19,20 On the other hand, a recent study supports an additional benefit of AA when performed with medialization thyroplasty in patients with posterior glottic gaps.21 However, other investigations have shown patients, in which the affected vocal fold was located at the same or in a lower vertical position and highlight the significant variations within patients. In addition, the vertical mismatch depends on the paralyzed position (lateral or medial paralysis), the status of the larynx, and the shape of the arytenoid.22,23 Nevertheless, in case of a lowered paralyzed vocal fold, patients could benefit of MT due to the postero-superior gliding movement of the arytenoid onto the shoulder of the CAJ and thus a heightened vocal process, as we could show in this study. Previously, we could demonstrate that the movement of the arytenoid cartilage onto the shoulder of the cricoid was very complex; it included rotation, rocking, and sliding of the arytenoid.24,25 Thus, the medialized, raised position of the vocal fold could be explained by the following movements: due to the medialization implant, the arytenoid was pushed upwards, in a sliding movement. In addition, the rotation of the arytenoid leads to a medialized vocal process. In our 3D reconstructions we could not observe any rocking movement of the arytenoid followed by the MTIS postoperatively. Nevertheless, it has to be considered that a slight rocking movement of the arytenoid on the cricoid facet not as much as we expect from phonatory to respiratory position seems to be possible due to the pressure of the implant. However, the elongation of the contralateral (untreated) vocal fold could not be explained by any direct action of the medialization implant. Therefore, we interpreted the elongation as a sort of compensatory mechanism of the contralateral laryngeal muscles, which moved to provide optimal conditions for voice production. Further studies are needed to investigate that phenomenon in detail. Our study had some limitations. First, the number of subjects in our study was relatively small. In addition, there were variations between patients, regarding the severity of paralysis, the shape of the arytenoid, and the sex and age.12,15 Further studies with a larger number of subjects are needed to specify how the MTIS is likely to influence a given individual. Second, we did not assess the influence of
Journal of Voice, Vol. &&, No. &&, 2018
the extra laryngeal muscles on the final position of the paralyzed vocal fold or on the healthy vocal fold. As mentioned above, the position of the arytenoid cartilage, both in respiratory and in phonatory functions, depends on various factors (sex, age, cricothyroid-joint-type, extra-laryngeal muscles). In addition, we are aware that 2 days after surgery the tissue can be swollen, and can influence the position of the arytenoid cartilage. These factors add complexity to an analysis of the true impact of the MTIS on the arytenoid, and hence, on the vocal fold. To the best of our knowledge, this study was the first to visualize the biomechanical influence of the MTIS on the arytenoid and the vocal fold in patients with UVFP. In previous studies, we showed that superimposing 3D images of the laryngeal framework, based on HRCT scans, was a suitable method for analyzing the movement and position of the arytenoid cartilage.26,27 Our study highlighted the potential of this method for further investigations in this field of research. It is crucial to know the precise position of the paralyzed vocal fold for an understanding of the mechanisms underlying the results of MTIS. This study was the first to show the interaction between the MTIS and the biomechanics of the arytenoid cartilage in patients with UVFP. Our findings about the impact of the MTIS on the arytenoid cartilage might influence the optimization of preoperative planning in the future.
TAGEDH1REFERENCESTAGEDN 1. El-Banna M, Youssef G. Early voice therapy in patients with unilateral vocal fold paralysis. Folia Phoniatr Logop. 2014;66:237–243. 2. Mortensen M, Carroll L, Woo P. Arytenoid adduction with medialization laryngoplasty versus injection or medialization laryngoplasty: the role of the arytenoidopexy. Laryngoscope. 2009;119:827–831. 3. Isshiki N. Progress in laryngeal framework surgery. Acta Otolaryngol. 2000;120:120–127. 4. Raj A, Girhotra M, Meher R. Medialization laryngoplasty—a study of 15 cases. Indian J Otolaryngol Head Neck Surg. 2004;56:283–288. 5. Laccourreye O, Papon JF, Menard M, et al. [Treatment of recurrent unilateral paralysis with thyroplasty with Montgomery implant]. Ann Chir. 2001;126:768–771. 6. Laccourreye O, El Sharkawy L, Holsinger FC, et al. Thyroplasty type I with Montgomery implant among native French language speakers with unilateral laryngeal nerve paralysis. Laryngoscope. 2005;115:1411–1417. 7. Montgomery WW, Montgomery SK. Montgomery thyroplasty implant system. Ann Otol Rhinol Laryngol Suppl. 1997;170:1–16. 8. Isshiki N, Tanabe M, Sawada M. Arytenoid adduction for unilateral vocal cord paralysis. Arch Otolaryngol. 1978;104:555–558. 9. Zeitels SM, Mauri M, Dailey SH. Adduction arytenopexy for vocal fold paralysis: indications and technique. J Laryngol Otol. 2004;118:508–516. 10. Iwahashi T, Ogawa M, Hosokawa K, Mochizuki R, Inohara H. Computed tomographic assessment of the causal factors of unsuccessful medialization thyroplasty. Acta Otolaryngol. 2015;135:283–289. 11. Schwarz K, Cielo CA, Steffen N, Jotz GP, Becker J. Voice and vocal fold position in men with unilateral vocal fold paralysis. Braz J Otorhinolaryngol. 2011;77:761–767. 12. Hiramatsu H, Tokashiki R, Suzuki M. Usefulness of threedimensional computed tomography of the larynx for evaluation of unilateral vocal fold paralysis before and after treatment:
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Montgomery Implant influences vocal fold length and position
technique and clinical applications. Eur Arch Otorhinolaryngol. 2008;265:725–730. Hiramatsu H, Tokashiki R, Nakamura M, et al. Characterization of arytenoid vertical displacement in unilateral vocal fold paralysis by three-dimensional computed tomography. Eur Arch Otorhinolaryngol. 2009;266:97–104. Okamoto I, Tokashiki R, Hiramatsu H, et al. Detection of passive movement of the arytenoid cartilage in unilateral vocal-fold paralysis by laryngoscopic observation: useful diagnostic findings. Eur Arch Otorhinolaryngol. 2012;269:565–570. Wang Q, Liang L, Liu Y, et al. Quantitative analysis of the visor-like vertical motion of the cricoarytenoid joint in the living subject. J Voice. 2016;30:354–361. Unteregger F, Thommen J, Honegger F, et al. How age and frequency impact the thyroid cartilages of professional singers. J Voice 2018; pii: S0892-1997(17)30395-8. doi: 10.1016/j.jvoice.2017.11.017. [Epub ahead of print]. Storck C, Unteregger F. Cricothyroid joint type as predictor for vocal fold elongation in professional singers. Laryngoscope. 2018;128:1176–1181. Mau T, Weinheimer KT. Three-dimensional arytenoid movement induced by vocal fold injections. Laryngoscope. 2010;120:1563–1568. Chester MW, Stewart MG. Arytenoid adduction combined with medialization thyroplasty: an evidence-based review. Otolaryngol Head Neck Surg. 2003;129:305–310.
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20. Li AJ, Johns MM, Jackson-Menaldi C, et al. Glottic closure patterns: type I thyroplasty versus type I thyroplasty with arytenoid adduction. J Voice. 2011;25:259–264. 21. Chang J, Schneider SL, Curtis J, et al. Outcomes of medialization laryngoplasty with and without arytenoid adduction. Laryngoscope. 2017;127:2591–2595. 22. Hong KH, Jung KS. Arytenoid appearance and vertical level difference between the paralyzed and innervated vocal cords. Laryngoscope. 2001;111:227–232. 23. Yumoto E, Oyamada Y, Nakano K, et al. Three-dimensional characteristics of the larynx with immobile vocal fold. Arch Otolaryngol Head Neck Surg. 2004;130:967–974. 24. Unteregger F, Honegger F, Potthast S, et al. 3D analysis of the movements of the laryngeal cartilages during singing. Laryngoscope. 2017;127:1639–1643. 25. Storck C, Juergens P, Fischer C, et al. Biomechanics of the cricoarytenoid joint: three-dimensional imaging and vector analysis. J Voice. 2011;25:406–410. 26. Vorik A, Unteregger F, Zwicky S, et al. Three-dimensional imaging of high-resolution computer tomography of singers' larynges—a pilot study. J Voice. 2017;31. 115 e117-115 e121. 27. Storck C, Juergens P, Fischer C, et al. Three-dimensional imaging of the larynx for pre-operative planning of laryngeal framework surgery. Eur Arch Otorhinolaryngol. 2010;267:557–563.
Surgical Impact of the Montgomery Implant System on Arytenoid Cartilage and the Paralyzed Vocal Fold 1
€ thi, Flurin Honegger, and Fabian Unteregger, Basel, Switzerland Claudio Storck, 1Martin Lu Objectives/Hypothesis. Medialization thyroplasty (MT) has become a prominent method for treating glottal insufficiency. This study aimed to visualize the biomechanical influence of a medialization implant on arytenoid cartilage, particularly on the length and level of paralyzation in the vocal fold, in patients with unilateral vocal fold paralysis. Study Design. Prospective study. Methods. We recruited 15 patients (10 men, 5 women) with unilateral vocal fold paralysis that underwent MT Ò with a Montgomery thyroplasty implant. We performed high-resolution computed tomography of the arytenoid cartilage before and after MT and analyzed the three-dimensional images. To visualize the movement of the arytenoid and to measure the lengthening of the vocal fold, we superimposed pre- and postoperative 3D images with MIMICS software. Results. On the affected side, the implant pushed the arytenoid backwards. In addition, the vocal process of the arytenoid was inwardly rotated. These movements resulted in an elongated, augmented vocal fold on the affected side. Conclusion. MT led to an elongated, medialized vocal fold on the treated side. After the intervention, the vocal folds on both sides were the same length in the phonatory position. Key Words: Larynx 3D Montgomery MIMICS Unilateral vocal fold immobility Arytenoid cartilage.
TAGEDH1INTRODUCTIONTAGEDN Unilateral vocal fold paralysis (UVFP) often leads to dysphonia as the main symptom. Insufficient glottal closure results in a membranous gap with asymmetric vocal folds. The size of this gap determines the degree of vocal complaints.1 Various methods have been developed to restore glottal closure, eg, an injection laryngoplasty, medialization thyroplasty (MT), arytenoid adduction (AA), arytenoidopexy (AP), or muscle reinnervation. However, MT is one of the dominant methods for treating glottal insufficiency.2,3 This method is safe and simple. Several previous studies have demonstrated the many postoperative benefits of MT, including improvements in voice quality, swallowing impairments, and breathlessness.4-6 MT can be performed with different implant materials (eg, thyroid cartilage, silasÒ tic, goretex , titanium, hydroxylapatite, or different injectables), with all different advantages and disadvantages. For the latter, we refer to the literature. Development of the Ò Montgomery Thyroplasty Implant System (MTIS), by Montgomery and Montgomery,7 has contributed to standardizing the MT intervention. Accepted for publication July 13, 2018. Presented at The Voice Foundations 45th Annual Symposium, June 3, 2017, Philadelphia, USA, Winner of the Hamdan Award 2017. Financial disclosure: No. Conflict of interest: No. Level of evidence: 4. From the Department of Otorhinolaryngology, Head and Neck Surgery, Division of Phoniatrics, University Hospital Basel, Basel, Switzerland. 1 Equal co-authors. Address correspondence and reprint requests to Claudio Storck, Department of Otorhinolaryngology, Head and Neck Surgery, Division of Phoniatrics, University Hospital Basel, Petersgraben 4, 4031 Basel, Switzerland. E-mail: [email protected] Journal of Voice, Vol. &&, No. &&, pp. 1 5 0892-1997 © 2018 The Voice Foundation. Published by Elsevier Inc. All rights reserved. https://doi.org/10.1016/j.jvoice.2018.07.019
Patients with UVFP display an inward-rotated arytenoid; thus, the vocal process is inferior to that on the non-paralyzed side. The vocal fold is excavated, due to reduced tension, and the level is lowered. Therefore, restoring the voice requires achieving glottal closure, restoring the length, and raising the vocal fold level. It is assumed that the MT has some limitations, particularly in patients with a wide posterior glottal gap and/or differences in the vertical levels of the vocal folds.3,8,9 Therefore, many authors recommend performing an AA or AP, in addition to an MT.2,8 Both techniques alter the position of the arytenoid. This repositioning leads to better closure of the posterior glottis and an optimized position/level of the vocal fold, which results in a better voice outcome.2,8 Nevertheless, the functional voice outcome is controversial, compared to the higher morbidity related to exposing the arytenoid cartilage.2,8,9 To date, no studies have analyzed the length in the vocal fold induced by MT, with or without additional AA/AP. Due to this lack of evidence, it remains unclear how the level and the length of the paralyzed vocal fold might be influenced by MT with the MTIS. Two-dimensional endoscopy is a common approach for examining the vocal folds pre- and postoperatively. However, this approach has some limitations in visualizing the level of the vocal fold and estimating the vertical movements of the arytenoid and vocal folds.10 Investigations with high-resolution computed tomography (HRCT) offer a three-dimensional view. With HRCT, the influence of the medialization implant on the arytenoid cartilage can be evaluated and quantitatively measured. Therefore, the present study aimed to perform HRCT to visualize the biomechanical influence of the MTIS on the
ARTICLE IN PRESS 2
Journal of Voice, Vol. &&, No. &&, 2018
arytenoid cartilage, particularly on the elongation of the paralyzed vocal fold. T ATERIALS AND METHODSTAGEDN AGEDH1M Study population Between 2015 and 2016, a total of 15 patients (10 men, 5 women) with UVFP (9 on the left side, 6 on the right side) underwent a type I MT with the MTIS at the University Hospital of Basel, Switzerland. The UVFP was caused by a bronchial carcinoma in nine patients, meningioma surgery in two patients, vagus neurinoma surgery in two patients, and a reconstruction of the aortal branch in two patients. The mean age was 63 (range: 48 77) years. All patients underwent pre- and postoperative videoendostroboscopies. In addition, all patients underwent an HRCT of the larynx, 1 day before surgery and 2 days after surgery (details described in Section 2.2). All procedures were performed in the operation room under local anesthesia by the same surgeon (C.S.). After preparing the thyroid ala, the window was cut out of the thyroid ala and the inner perichondrium was undermined. Different precast sizers were used to find out the right size. The implant was placed without use of endoscopic control. The study was approved by the Medical Ethics Committee of the University of Basel, Switzerland. HRCT imaging HRCT of the larynx was performed 1 day before surgery and 2 days after surgery on a Siemens Healthcare Scanner (Zurich, Switzerland). We used the following parameters: 100 kV and 203 mA; slice thickness: 1.5 mm; radiation dosage: 1.2 mSv; and length product: 182 mGy cm. During the scan, patients were asked to sing or act as if singing in their own middle speaking frequency; this activity moved the non-paralyzed vocal fold into the phonation position. Postprocess imaging To discern the laryngeal structures, we converted the HRCT data to digital imaging and communications in medicine data and transferred them to the postprocess imaging software, MIMICS 14.0 (Version 14.0, Materialise, Leuven, Belgium). Then, we created 3D images of the larynx. To visualize the movement of the arytenoid and to measure the lengthening of the vocal fold, the pre- and postoperative 3D images were superimposed (Figure 1, compound movement). To calculate the vocal fold length, we defined the anterior commissure and the vocal process of the arytenoid cartilage as landmarks in the three-dimensional pre- and Ò postoperative images. MIMICS then calculated the distances between landmarks. All statistical analyses and comparisons of vocal fold length data were performed with Matlab R2017a, and the version that corresponded to Statistics Toolbox. Significance testing was performed with the paired t test, for means, and with the Wilcoxon rank sum test, for medians.
FIGURE 1. Representative 3D reconstructions show movements of the cricoid cartilage and the arytenoid cartilage with the MT procedure. (A) Superior views, (B) anterior views, and (C) lateral views show the preoperative (green) and postoperative (yellow) positions of the arytenoid. (Right column) Superimposed 3D scans of the pre- and postoperative positions of the arytenoid; (black arrows) the movement of the arytenoid. Black points = vocal process. The arytenoid was rotated medially and pushed posterosuperiorly by the Montgomery implant (white).
T ESULTSTAGEDN AGEDH1R Videoendostroboscopy With preoperative videoendostroboscopy, we could observe an excavated paralyzed vocal fold in intermediate position including insufficient glottal closure, anterior tilting of the arytenoid cartilage, and a lowered vocal fold in 15/15 patients. Postoperatively, all patients achieved complete glottal closure and straightening of the paralyzed vocal fold. The paralyzed vocal fold seemed to be at the same level as the non-paralyzed vocal fold.
Elongation of the vocal fold The paralyzed vocal fold was significantly elongated by up to 20.6% (P = 0.00003), from the mean preoperative length of 17.6 mm (range: 11.8 23.0 mm) to the mean postoperative length of 21.1 mm (range: 15.1 27.0 mm). In addition, in 10/15 patients, the non-paralyzed vocal fold was significantly elongated, by 1.0% (P = 0.015), from a mean of 20.9 mm (range: 14.3 26.8 mm) preoperatively to a mean of 21.1 mm (range: 14.5 27.6 mm) postoperatively. Thus, the two vocal folds were the same length postoperatively in the phonatory position (Table 1,Figure 2).
Movement of the arytenoid cartilage The reconstructed 3D images showed that the MTIS pushed the arytenoid backwards, up onto the cricoidal facet, in 15/ 15 patients. This backward sliding leads to a posterior and superior movement of the vocal process. Additionally, the
ARTICLE IN PRESS Claudio Storck, et al
3
Montgomery Implant influences vocal fold length and position
TABLE 1. Influence of the MTIS on the Length of the Vocal Folds (VF) Mean lengths (mm) of the vocal folds before and after the MTIS intervention Preoperative Postoperative
Paralyzed VF Non-paralyzed VF
Elongation
Mean
SD
Mean
SD
P
Mean [range]
% [range]
17.6 20.9
3.0 3.5
21.1 21.1
3.5 3.6
0.00003 0.015
3.5 [2.9, 4.5] 0.2 [0.04, 0.37]
20.6 [17.0, 24.9] 1.0 [0.17, 1.62]
MTIS led to an inward rotation of the vocal process of the arytenoid cartilage. These movements (backward push and inward rotation) led to a backward, upward movement of the vocal process. This resulted in vocal fold elongation. In addition, the vocal fold was medialized at a higher level. In our 3D reconstructions of the cricoid and arytenoids, it was possible to visualize the same level of the vocal process of the paralyzed vocal fold to the vocal process of the non-paralyzed vocal fold (Figure 1).
TAGEDH1DISCUSSION AND CONCLUSIONTAGEDN MT has become one of the dominant methods for treating glottal insufficiency in cases of dysphonia, due to UVFP.1 The position of the paralyzed vocal fold in patients with UVFP has been intensely studied, during both phonation and respiration. Deviations in the horizontal plane are typically classified as median, paramedian, intermediate, or lateral positions.11 However, differences in the vertical plane can also occur on the paralyzed side; these changes are more complex to investigate. The vertical gap between the paralyzed and the innervated vocal folds remains an issue of
FIGURE 2. Pre-to-postoperative changes in vocal fold length. (Left) Changes in the paralyzed vocal fold lengths on the treated side indicate a net increase with treatment, as intended; (right) changes observed on the untreated side. (Grey lines) Lines indicate the preoperative to postoperative values for each individual. Both the treated and untreated sides show a significant increase in the median and mean values, although the change is small on the untreated side. ***P < 5 £ 10¡5; *P < 0.05.
controversy. However, most studies assume that the level of the vocal fold on the affected side is lower than the level of the vocal fold on the healthy side.12-14 Nevertheless, many parameters were shown to influence the position of the paralyzed arytenoid cartilage, including the severity of paralysis, the shape of the arytenoid, and the sex and age of the patient.12,15 Moreover, the type of cricothyroid joint also seems to play an important role in the elongation of the vocal fold.16,17 Interestingly, we did not find any studies that analyzed the length of the vocal fold induced by medialization, with or without additional AA/AP. A further study investigating the influence of vocal fold injection onto the position of the arytenoid showed a combination of medial rotation and medial translation movement of the arytenoid after intervention. They also did not observe a movement in the coronal plane, but interpret both movements as components of a rocking motion, without analyzing the specific influence onto the vocal process and thus on the height and length of the vocal fold.18 Thus, it was unclear whether the level of the affected vocal fold could be influenced by MT with the MTIS, and if so, by what mechanism. The purpose of the present study was to investigate the biomechanical influence of the MTIS on the elongation and level of the paralyzed vocal fold. We used the software package, MIMICS, to superimpose 3D images of the larynx to visualize the movement of the arytenoid cartilage on the shoulder of the cricoarytenoid facet. Due to the Montgomery implant, the arytenoid cartilage was pushed posterior and upwards, which resulted in a backward, upward movement of the vocal process. On one hand, postoperative measurements showed that the paralyzed vocal fold was significantly elongated, by about 20.6%. On the other hand, the paralyzed vocal fold could be medialized and raised to nearly the same level as the untreated vocal fold. We measured the length of the contralateral, untreated vocal fold to compare the lengths of both vocal folds postoperatively. Interestingly, we found that the untreated vocal fold was significantly elongated, by an average of 0.2 mm. Consequently, the two vocal folds were the same length postoperatively. Regarding the vertical gap between the paralyzed and the innervated vocal fold, there is still controversy in literature: Some studies suppose that during inspiration, the level of the vocal fold on the healthy side is higher compared to the paralyzed side, due to a rocking movement of the arytenoid
ARTICLE IN PRESS 4 on the non-paralyzed side. During phonation, the paralyzed arytenoid can perform a passive gliding movement cranially, resulting in a higher level of the paralyzed vocal fold, compared to the healthy side. It is assumed that this phenomenon is, first, caused by contact with the non-paralyzed arytenoid during phonation and, secondly, by expired air.12,13 In these cases, AA is often recommended to medialize the paralyzed vocal fold and correct the difference in fold levels by lowering the paralyzed vocal fold.2 This, however, is also subject of a controversial discussion: On the one hand, former studies, which evaluated if AA in addition to MT yields better posterior closure and vertical height equality than MT alone, showed no significant additional benefit of AA compared to MT alone.19,20 On the other hand, a recent study supports an additional benefit of AA when performed with medialization thyroplasty in patients with posterior glottic gaps.21 However, other investigations have shown patients, in which the affected vocal fold was located at the same or in a lower vertical position and highlight the significant variations within patients. In addition, the vertical mismatch depends on the paralyzed position (lateral or medial paralysis), the status of the larynx, and the shape of the arytenoid.22,23 Nevertheless, in case of a lowered paralyzed vocal fold, patients could benefit of MT due to the postero-superior gliding movement of the arytenoid onto the shoulder of the CAJ and thus a heightened vocal process, as we could show in this study. Previously, we could demonstrate that the movement of the arytenoid cartilage onto the shoulder of the cricoid was very complex; it included rotation, rocking, and sliding of the arytenoid.24,25 Thus, the medialized, raised position of the vocal fold could be explained by the following movements: due to the medialization implant, the arytenoid was pushed upwards, in a sliding movement. In addition, the rotation of the arytenoid leads to a medialized vocal process. In our 3D reconstructions we could not observe any rocking movement of the arytenoid followed by the MTIS postoperatively. Nevertheless, it has to be considered that a slight rocking movement of the arytenoid on the cricoid facet not as much as we expect from phonatory to respiratory position seems to be possible due to the pressure of the implant. However, the elongation of the contralateral (untreated) vocal fold could not be explained by any direct action of the medialization implant. Therefore, we interpreted the elongation as a sort of compensatory mechanism of the contralateral laryngeal muscles, which moved to provide optimal conditions for voice production. Further studies are needed to investigate that phenomenon in detail. Our study had some limitations. First, the number of subjects in our study was relatively small. In addition, there were variations between patients, regarding the severity of paralysis, the shape of the arytenoid, and the sex and age.12,15 Further studies with a larger number of subjects are needed to specify how the MTIS is likely to influence a given individual. Second, we did not assess the influence of
Journal of Voice, Vol. &&, No. &&, 2018
the extra laryngeal muscles on the final position of the paralyzed vocal fold or on the healthy vocal fold. As mentioned above, the position of the arytenoid cartilage, both in respiratory and in phonatory functions, depends on various factors (sex, age, cricothyroid-joint-type, extra-laryngeal muscles). In addition, we are aware that 2 days after surgery the tissue can be swollen, and can influence the position of the arytenoid cartilage. These factors add complexity to an analysis of the true impact of the MTIS on the arytenoid, and hence, on the vocal fold. To the best of our knowledge, this study was the first to visualize the biomechanical influence of the MTIS on the arytenoid and the vocal fold in patients with UVFP. In previous studies, we showed that superimposing 3D images of the laryngeal framework, based on HRCT scans, was a suitable method for analyzing the movement and position of the arytenoid cartilage.26,27 Our study highlighted the potential of this method for further investigations in this field of research. It is crucial to know the precise position of the paralyzed vocal fold for an understanding of the mechanisms underlying the results of MTIS. This study was the first to show the interaction between the MTIS and the biomechanics of the arytenoid cartilage in patients with UVFP. Our findings about the impact of the MTIS on the arytenoid cartilage might influence the optimization of preoperative planning in the future.
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