Journal of Laryngology and Voice

: 2018  |  Volume : 8  |  Issue : 2  |  Page : 29--35

Type I thyroplasty for unilateral vocal fold palsy: Silastic or titanium implant?

Nidhi Vohra Maggon, Ashwani Sethi, Awadhesh Kumar Mishra, Ajay Mallick 
 Department of Otorhinolaryngology, Army College of Medical Sciences, Base Hospital, New Delhi, India

Correspondence Address:
Dr. Ashwani Sethi
Department of Otorhinolaryngology, Army College of Medical Sciences, Base Hospital, Delhi Cantt - 110 010, New Delhi


Introduction: Process of speech involves adduction of true vocal cords, and their palsy results in dysphonia with or without aspiration. Medialization thyroplasty is the standard of care and involves insertion of an implant to achieve apposition. We conducted a randomized prospective study to evaluate two types of implants (Silastic vs. titanium) in terms of surgical time and perceptive, acoustic, and aerodynamic evaluation. Materials and Methods: Twenty-six patients were randomized into two groups and were implanted one type of implant. They were evaluated and compared on the basis of voice handicap index (VHI), voice quality evaluation (VQE), and maximum phonation time (MPT). Results: The mean time taken for Silastic implantation was 83.07 min and for titanium implantation was 52.16 min. VHI and VQE decreased significantly following implantation in both groups, while MPT increased in both groups significantly. There was no significant difference between two groups. Conclusion: Medialization thyroplasty with both types of implants achieves good and comparable results. Silastic implant surgery takes longer time but is relatively inexpensive.

How to cite this article:
Maggon NV, Sethi A, Mishra AK, Mallick A. Type I thyroplasty for unilateral vocal fold palsy: Silastic or titanium implant?.J Laryngol Voice 2018;8:29-35

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Maggon NV, Sethi A, Mishra AK, Mallick A. Type I thyroplasty for unilateral vocal fold palsy: Silastic or titanium implant?. J Laryngol Voice [serial online] 2018 [cited 2019 Aug 25 ];8:29-35
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Human larynx performs various functions and the most important of these is protection of lower respiratory tract that is achieved by its sphincteric action and sensory innervation. Larynx is also essential for coughing, phonation, lifting heavy weights by increasing the intrathoracic pressure and controlling the exit of air from lungs.[1] Speech, by use of language, is the foremost medium of communication in all cultures. The process of speech involves encoding one's thoughts into a recognizable sound by a complex mechanism that converts aerodynamic energy of the lungs and thoracic cavity into acoustic energy. Adduction of true vocal folds plays a critical role in this conversion. A unilateral vocal fold palsy (UVFP) immobilizes the vocal fold and prevents its adduction during phonation. This leads to dysphonia and may also cause dysphagia and/or aspiration, thus posing a serious health risk and impairing the quality of life (QOL).[2] Medialization thyroplasty is the most preferred surgical treatment for UVFP. It mechanically aligns the paralyzed cord to the midline position and ensures apposition of the normal cord to the paralyzed cord.[3] We performed type I (medialization) thyroplasty in 26 patients of UVFP using two different types of implants, namely Silastic (Silicon elastomer) and titanium vocal fold medialization implant (TVFMI), and compared the outcomes in terms of the following three parameters:

Perceptive evaluation of voice using voice handicap index (VHI)Acoustic evaluation by voice quality evaluation (VQE)Aerodynamic evaluation using maximum phonation time (MPT).

We also compared the time taken to perform the two procedures using two different implants.

 Materials and Methods

This study was carried out in a tertiary care hospital from January 2013 to January 2016. A total of 26 patients suffering UVFP causing an invaliding dysphonia with or without aspiration were included in the study. All patients were treated with speech rehabilitation for 6 months. If it failed to achieve desired results only then surgery was advised. They were randomly divided into two groups (Gp) with the help of a random number generator. Fourteen patients underwent thyroplasty with a Silastic implant (Gp 1) and 12 with TVFMI (Gp 2) (TVFMI used in this study was the one standardized by Prof. Gerhard Friedrich M.D., Graz, Austria). A single surgeon performed all the surgeries.

Exclusion criteria are as follows:

Patients with any structural abnormalities of true vocal foldsThose who had undergone injection medialization alreadySuffered a pulmonary disease affecting voice generationUnwilling for surgery.

All patients underwent complete preintervention workup including examination of cranial nerves and ENT examination including flexible fiberoptic laryngoscopy (FOL) and video-laryngostroboscopy. A detailed voice analysis was done a day before surgery in terms of:

Subjective perceptive evaluation by self-assessment using VHI incorporating all three domains, viz., physical, functional, and emotionalAcoustic analysis by VQE score determined by Dr. Speech voice analysis software (Tiger DRS, Inc Seattle, WA 98175) incorporating fundamental frequency (F0) of voice, jitter (variation in F0 from cycle to cycle), shimmer (amplitude variation from cycle to cycle), and normalized noise energy (NNE)Aerodynamic evaluation in terms of MPT.

Following detailed clinical examination, a contrast-enhanced computed tomographic scan was performed in all patients to exclude any organic lesion that may have caused UVFP.

Patients were randomly divided into two groups; 14 patients underwent medialization thyroplasty with a Silastic implant (Gp 1) and 12 patients were implanted a TVFMI (Gp 2). In all cases, surgery was performed by the same surgeon under local infiltrative anesthesia (lidocaine 2% with adrenaline), and the patient was placed supine with head rotated to the side opposite to side of palsy. Superior and inferior edges of the thyroid cartilage and cricoid cartilage were identified. After exposing the thyroid cartilage, a vernier caliper (surgical grade) was used to mark the level of vocal cord. The markings of standard thyroplasty window were made on the outer perichondrium (13 mm × 6 mm for males; 11 mm × 5 mm for females). A window was created using a burr, and an adequate circumferential pocket was made between the window and the inner perichondrium for fixing the implant. The implant was inserted in this pocket and was adjusted to achieve adequate medialization to ensure satisfactory apposition with the opposite vocal fold [Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6]. This fine adjustment was made under FOL guidance with the patient being asked to say “e” at different intensities. Improvement in voice quality was assessed simultaneously. The total time taken to perform the surgery was recorded. Patients were kept under observation for 48 h. The voice analysis was done preoperatively and postoperatively at 3 months.{Figure 1}{Figure 2}{Figure 3}{Figure 4}{Figure 5}{Figure 6}


A total of 26 patients underwent medialization thyroplasty. Of these 26 patients, 16 were male and 10 were female, with the age ranging from 35 to 72 years (mean: 51 years). Fourteen patients underwent a Silastic implantation and 12 patients underwent a TVFMI implantation.

Of the 26 patients, 18 were labeled as idiopathic UVFP as no clear etiology was found after a detailed evaluation, five patients suffered UVFP following surgery due to iatrogenic injury after hemi thyroidectomy, and three patients had developed UVFP due to trauma in a road traffic accident and splinter injury [Table 1].{Table 1}

The mean time taken for thyroplasty in Gp 1 was 83.07 min (range: 72–92 min, standard deviation [SD]: 6.58) while the mean time taken in Gp 2 was 52.16 min (range: 43–61 min, SD: 5.92). The surgical time taken in Gp 2 was significantly less than time taken for surgery in Gp 1 (P < 0.05).

No significant immediate postoperative complications were noticed. Two patients developed a subcutaneous hematoma (both in Gp 2) that resolved without any intervention. Three patients developed laryngeal edema (2 in Gp 1 and 1 in Gp 2), leading to a deterioration in the voice quality that had been achieved peroperatively and had to be treated with oral steroids for 2 weeks. All three achieved complete clinical and functional resolution. Twenty-four patients (92.3%) reported marked improvement in phonation. Two cases in Gp 2 had inadequate improvement in phonation. A threat of extrusion of the Silastic implant was noticed 3 weeks after surgery in one patient. It was addressed by repositioning the implant under local anesthesia.

The mean preoperative VHI score in Gp 1 was 68.29 (SD: 6.97) which reduced to a mean VHI score of 22.07 (SD: 2.16) postoperatively. The mean preoperative VHI score in Gp 2 was 69.75 (SD: 4.79) which reduced to a mean VHI score of 20.67 (SD: 1.78) postoperatively. The difference between VHI score before and after surgery in two groups was highly significant. However, the difference in reduction of VHI scores between the two groups was not significant statistically [Table 2].{Table 2}

In acoustic parameters, the mean preoperative VQE score in Gp 1 was 2.22 (SD: 0.29) which reduced significantly postoperatively to a mean of 0.73 (SD: 0.08). The mean preoperative VQE score in Gp 2 was 2.31 (SD: 0.24) which reduced significantly postoperatively to a mean of 0.72 (SD: 0.1) (P < 0.05) [Table 3]. However, there was no significant difference in improvement between the two groups.{Table 3}

In aerodynamic parameters, the mean preoperative MPT in Gp 1 was 5.14 s (SD: 0.95) and it increased to 14.93 s (SD: 0.83) after surgery. The mean preoperative MPT in Gp 2 was 4.83 s (SD: 0.83) and it increased to 14.08 s (SD: 1.16) after surgery. Improvement in MPT was significant in both groups (P < 0.05).


UVFP is the most common neurogenic disorder affecting the larynx.[4] UVFP is caused by any disease process that affects the recurrent laryngeal nerve (RLN) supplying intrinsic laryngeal muscles or due to any pathology affecting vagus nerve, particularly between the jugular foramen and entrance of RLN into larynx. Nearly 90% cases of UVFP are due to lesions which affect the peripheral segment of the nerve. Only 15% of the causative lesions are proximal to the jugular foramen.[5]

UVFP results in deficient glottic closure due to an incomplete true vocal fold approximation. The paralyzed vocal fold remains in abducted or in an intermediary position, resulting in dysphonia, swallowing disorders, reduced effectiveness of coughing, or even shortness of breath that may influence patient's QOL. Surgical treatment of UVFP is indicated if the patient suffers a life-threatening aspiration or an invaliding dysphonia in spite of speech therapy.[6] Medialization of the paralyzed vocal fold with a thyroid implant is one of the most widely employed surgical techniques for treating this glottic insufficiency. Isshiki et al. pioneered and described this technique in 1974.[7] Several thyroid implants have been described and each has its own advantages and disadvantages.[8],[9],[10],[11]

UVFP is observed 3–4 times more often on the left side.[8] In our study, 17 patients had a left-sided paralysis and 9 on the right (nearly 2:1). No organic cause for UVFP could be found in 18 patients (65.23%), while five patients suffered paralysis due to iatrogenic trauma (19.23%), and remaining three suffered a posttraumatic paralysis (11.53%). In none of our cases, UVFP resulted due to a malignancy. In an Australian study of 108 cases, etiology of the palsy was found to be iatrogenic in 41.66%, idiopathic in 30% (36 of 108), and due to other defined causes in 25% (27 of 108).[12] In another study of 397 cases, the single largest cause of unilateral immobility was a nonlaryngeal malignancy (24.7%), followed by secondary to surgical trauma (23.9%). Thyroidectomy accounted for only 8.2% of cases. The leading cause of bilateral immobility was surgical trauma (25.7%). Acute and chronic intubation injuries accounted for 21 unilateral (7.5%) and 18 bilateral (15.4%) cases.[13]

In our study, the mean time taken for the surgery in Gp 1 was 83.07 min while the mean time taken in Gp 2 was 52.16 min. The surgical time taken for Gp 2 was significantly less than the time taken for surgery in Gp 1. In a study by Storck et al., the average duration of surgery while using Silastic implant was 65 min and using TVFMI was 55 min.[14] The mean surgical time taken is slightly higher in our study as compared to other studies. However, as we became better conversant with the surgical technique, we did observe a reduction in surgical duration in the last 10 surgeries. The time taken to fashion the Silastic implant to fit the thyroid cartilage ostium adds to the surgical duration.

On subjective perceptive evaluation (improvement in QOL scale, i.e., VHI), there was a mean postoperative reduction of 46.22 (from 68.29 to 22.07) in Gp 1 and a reduction of 48.08 in Gp 2. There was a significant improvement in VHI scales in both groups, but the difference between two groups was not significant. Several studies have found the improvement in VHI to be a good indicator of voice improvement,[15] and our results also revealed marked enhancement in voice quality on all subscales, i.e., functional, emotional, and physical.

Acoustic parameters commonly used in voice analysis by Dr. Speech software are the fundamental frequency (F0), jitter, shimmer, and NNE. A composite parameter taking into account F0, jitter, shimmer, and NNE is VQE. It was analyzed in our patients and showed a significant fall in values after surgery from 2.22 to 0.73 in Gp 1. The fall was also significant in Gp 2 where the mean VQE value fell from a preoperative 2.29 to 0.68 postoperatively [Table 4]. In their study of eight canine larynges, Witt et al. conducted a type I thyroplasty with TVFMI and found that mean signal to noise ratio increased from 2.43 to 6.65 (P = 0.05), percent jitter decreased from 7.15% to 3.58%, and percent shimmer decreased from 27.80% to 13.69% (P = 0.005, P = 0.034).[16] Our results match the results of various other studies; however, in a study of 15 patients who underwent a porous titanium implant, Devos et al. did not find any significant difference in shimmer following surgery. Their results for F0, harmonics to noise ratio, and jitter were also equivocal.[17]{Table 4}

The ability to adduct the vocal folds efficiently and easily and to vibrate them strongly through rapid opening and closing cycles is referred to as glottic efficiency. A simple test of glottic efficiency is MPT and is the maximum time (in seconds), for which a person can sustain a vowel sound when produced on one deep breath at a relatively comfortable pitch and loudness. In a healthy larynx, an adult male can sustain vowel sounds for between 25 and 35 s and adult female between 15 and 25 s. In our study, the mean MPT values increased from a mean of 5.14 s to 14.93 s after surgery in Gp 1 and from a preoperative MPT of 4.83 s to 14.08 s postoperatively in Gp 2. There was a significant improvement in both the groups. However, the difference between two groups was not significant (P < 0.05). In a study of 19 patients undergoing type I thyroplasty, Asik et al. found a statistically significant increase in MPT from 5.5 ± 3 s to 11.2 ± 4.9 s postoperatively (P < 0.001).[18] Benninger et al. in their study of 78 cases of thyroplasty with Silastic implant found that MPT was significantly improved from 8.3 pretreatment to 22.6 at short-term follow-up (P < 0.05) and to 24.2 at long-term follow-up (P < 0.05).[19] Our results are similar to other studies and have revealed significant aerodynamic improvement in both groups.

Major complications of a medialization thyroplasty are wound hemorrhage, airway obstruction, or prosthesis extrusion. Other minor complications encountered are vocal fold hematoma without airway obstruction or prosthesis instability/movement. In our study, two patients developed a subcutaneous hematoma (both in Gp 2) that resolved without any intervention. Three patients developed laryngeal edema (2 in Gp 1 and 1 in Gp 2), leading to a deterioration in the voice quality that had been achieved peroperatively. All three were treated with oral steroids for 2 weeks and achieved complete clinical and functional resolution. In a study by Cotter et al., the rate of major complications was 8.6% and of minor complications was 29%.[20] Our rates of complications are better in comparison and may have been due to our fashioning the pouch with great care. This also probably explains the greater surgical time taken in this study.


Type I thyroplasty with both types of implants, i.e., Silastic and TVFMI, is equally effective and achieves significant comparable improvement on perceptive, acoustic, and aerodynamic parameters. A Silastic implant takes longer surgical time because of the necessity of fashioning the implant to the individual's requirement. This might result in slightly higher incidence of minor complications such as laryngeal edema and hematoma formation. However, a Silastic implant is much cheaper (costs only 1/5th) than a titanium implant.

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Conflicts of interest

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