Comparative analysis on the efficiency of the injection laryngoplasty technique using calcium hydroxyapatite (CaHA): the thyrohyoid approach versus the cricothyroid approach

Impact of Pulmonary Function on Voice Outcomes After Injection Laryngoplasty for Unilateral Vocal Fold Paralysis

OBJECTIVES

Pulmonary function is closely associated with voice quality especially in patients with voice disorder including unilateral vocal fold paralysis (UVFP). Injection laryngoplasty (IL) is the standard treatment for patients with UVFP. We investigated the subjective and objective voice outcomes according to pulmonary function test (PFT) before IL in patients with UVFP.

METHOD

We retrospectively analyzed the patients who underwent IL for UVFP between 2004 and 2021 (N = 1201), and finally investigated 261 patients with PFT results before IL. The patients were classified into three groups according to results of PFT: normal (n = 189, 72%), mild (n = 40, 15%), and moderate (n = 32, 13%) obstructive pattern. Aspiration symptoms and subjective and objective voice parameters of voice handicap index (VHI), GRBAS score, maximal phonation time (MPT), Jitter, Shimmer, and noise to harmonic ratio (NHR) were compared between normal and abnormal (mild or moderate obstructive pattern) PFT groups.

RESULTS

Age (68.0 ± 9.1 and 61.2 ± 12.6, respectively) was significantly higher and males were more common (84.7% and 57.7%, respectively) in abnormal PFT than in normal PFT. Aspiration showed significant improvement in all groups. The subjective and objective voice parameters significantly improved after IL in normal and mild obstruction groups, but MPT, Shimmer, and VHI did not significantly improve in the moderate obstruction group. The improvement in VHI-30 after IL was significantly higher in the normal group (20.0 ± 29.5) than in the mild (10.3 ± 32.8) or moderate (9.9 ± 33.2) obstruction group (P = 0.035). Improved amounts of MPT, Jitter, Shimmer, and NHR were not significantly different among the groups, but improvement of VHI was smallest in the moderate obstructive pattern group.

CONCLUSION

Voice parameters showed significant improvement after IL in both normal and mild obstructive pattern groups, but MPT and VHI did not significantly improve in the moderate obstructive pattern group. In addition, patients with normal pulmonary function had marked improvement of subjective symptoms after IL in comparison with patients with abnormal pulmonary function.

Acoustic and videoendoscopic effects of temporary vocal fold augmentation in an office-based setting: a quasi-experimental study

Background

Vocal-fold augmentation is a continuously developing treatment modality for glottic insufficiency. Patients with glottic insufficiency attend the phoniatrics clinics with increasing frequency. Glottic insufficiency may be due to vocal-fold paralysis, paresis, atrophy, sulcus vocalis, scarring, and vocal-fold deficiency after laryngeal surgery. A variety of materials exist for injection augmentation. This follow-up study aimed to assess the short-term as well as long-term outcomes of vocal-fold injection with calcium hydroxyapatite (CaHA) in patients with glottic gap 1–3 mm.

Method

This study included 25 patients with glottic insufficiency who underwent injection augmentation with CaHA. All patients were scheduled for voice evaluation using a comprehensive subjective and objective battery of assessments. Assessments were performed before the procedure and after the procedure at 2 months and at 1 year.

Results

Perceptual voice quality assessed with the GRBAS scale improved and the results were stable after 1 year. Shimmer and HNR improved continuously through the follow-up sessions, while jitter and f0 showed slight improvement after CaHA injection.

Conclusion

Voice improvement after injection of CaHA requires a minimum of 2 months to develop and may last for a long period.

Respiratory and voice outcomes of office-based injection laryngoplasty in patients with unilateral vocal fold paralysis

Background

Injection laryngoplasty is a surgical procedure used in management of glottal insufficiency. The objective of this study was to assess respiratory and voice outcomes of office-based injection laryngoplasty in patients with unilateral vocal fold paralysis (UVFP). Ten patients underwent office-based injection via transcutaneous approach using Radiesse or hyaluronic acid. Auditory perceptual assessment (APA), voice handicap index (VHI), size of the glottic gap, acoustic parameters (jitter, shimmer, and harmonic to noise ratio), maximum phonation time (MPT), stroboscopic evaluation, pulmonary function tests (PFTs), and videofluoroscopic evaluation of swallowing were done pre-injection, 1 week and 3 months post-injection.

Results

Subjective and objective voice outcomes, in addition to laryngostroboscopic parameters improved after injection. Non-significant difference was found between pre- and post-injection results of the PFTs.

Conclusions

Office-based injection laryngoplasty is a safe and effective method for treating UVFP. Patients with glottic gap (< 1–3 mm) are perfect candidates for such procedure. Injection laryngoplasty improves patients’ voice quality and does not impair respiration.

Guidelines for the Management of Unilateral Vocal Fold Paralysis From the Korean Society of Laryngology, Phoniatrics and Logopedics

The Korean Society of Laryngology, Phoniatrics and Logopedics appointed a task force to establish clinical practice guidelines for the management of unilateral vocal fold paralysis (UVFP). These guidelines cover a comprehensive range of management-related factors, including the diagnosis and treatment of UVFP, and provide in-depth information based on current, up-to-date knowledge. Detailed evidence profiles are provided for each recommendation. The CORE databases, including OVID Medline, Embase, the Cochrane Library, and KoreaMed, were searched to identify all relevant papers, using a predefined search strategy. When insufficient evidence existed, expert opinions and Delphi questionnaires were used to fill the evidence gap. The committee developed 16 evidence-based recommendations in six categories: initial evaluation (R1–4), spontaneous recovery (R5), medical treatment (R6), surgical treatment (R7–14), voice therapy (R15), and aspiration prevention (R16). The goal of these guidelines is to assist general otolaryngologists and speech-language pathologists who are primarily responsible for treating patients with UVFP. These guidelines are also intended to facilitate understanding of the condition among other health-care providers, including primary care physicians, nurses, and policy-makers.

Vocal Fold Insufficiency: How Effective is Injection Laryngoplasty? Short Term Clinical Outcomes

Office based Injection Laryngoplasty has become a common and feasible method of addressing vocal fold insufficiency (VFI) resulting from a plethora of aetiologies. Contemporary to various injectates, Calcium Hydroxylapatite has met with great success across usage with various techniques. But, irrespective of the technique and injectate material, the burning question in mind of "realistic" clientele remains, "How soon will I have by voice back?". Aim of this study is to evaluate the short term (3 months postoperative) effects of Injection Laryngoplasty in cases of VFI using Calcium Hydroxylapatite via trans cricothyroid route, in terms of both objective and subjective parameters. 12 patients with mean age of 35.67 years underwent vocal fold injections (via transnasal flexible fibreoptic laryngoscopic guided trans-cricothyroid membrane approach using CaHA) for VFI. The pre injection and 1, 2- and 3-months post injection scores' changes in outcome measures in form of videostroboscopic parameters, Voice Handicap Index scores and acoustic analysis were compiled and analysed. 91.6% of patients showed statistically significant benefit after 3 months post injection. 0.1% patients showed loss of benefit of the CaHA material even 3 months post injection. Average length of benefit was 1-month post injection. No significant complication was observed in any patient. We conclude that the objective evidence of structural and functional improvement may be seen immediately post injection laryngoplasty, minimum of 3 months is required for evident improvement in patient's perception of his own voice in terms of Quality of Life parameters.

Stroboscopic assessment of unilateral vocal fold paralysis: a systematic review

PURPOSE

To review the relevant basic stroboscopic evaluations in unilateral vocal fold paralysis (UVFP). Our aim was twofold: (1) to determine the frequency of use of stroboscopic parameters in outcome evaluation after surgical treatment of UVFP using a Pareto diagram; and (2) to select the most relevant parameters in terms of a significant difference between pre- and post-surgical intervention for UVFP.

METHODS

A systematic review in PUBMED includes studies on stroboscopic evaluation in combination with UVFP and surgical treatment. The review was limited to English studies published between 1990 and March 2018. The most frequently used stroboscopic parameters were identified using a Pareto diagram. Then, 'the percentage of significance' for the most frequently stroboscopic parameters was identified by comparing the number of studies that showed a statistically significant change in pre- and post-treatment results with the total number of studies using the same parameters.

RESULTS

Seven stroboscopic parameters were nominated using the Pareto diagram. In decreasing order of citation frequency, periodicity, edge bowing, mucosal wave, glottic gap, position of vocal fold, amplitude, and symmetry have respective percentages of significance of 87.5%, 83.3%, 77.7%, 64.5%, 60%, 57.1%, and 50%. Five pertinent scales were selected for the most frequent and significant stroboscopic parameters.

CONCLUSIONS

The results indicate that periodicity, edge bowing, mucosal wave, glottic gap, and position of vocal fold represent the five most frequently used and relevant stroboscopic parameters in UVFP evaluation. The current review outlines a proposal scale of these stroboscopic parameters.

PROSPERO REGISTRATION NUMBER

CRD42019126786.

Injection laryngoplasty in neonates and young children with unilateral vocal fold immobility

INTRODUCTION

Although injection laryngoplasty (IL) is a well-accepted treatment strategy in older children and adults with unilateral vocal fold immobility (UVFI), its efficacy and safety have not been well studied in neonates and young children.

OBJECTIVES

The main objective of this study was to evaluate the clinical and radiographic effects of IL on aspiration & dysphagia in neonates and young children with UVFI.

METHODS

This was a retrospective chart review of infants and children who underwent IL at a tertiary children's hospital. The primary endpoints were improved aspiration and avoidance of gastrostomy tube placement. Additional endpoints included adverse airway and swallowing effects of IL.

RESULTS

Eight patients were included in this case series. A total of 10 injection laryngoplasties were performed. Average corrected age of patients undergoing IL was 1.22 years(range 0.5-3.6 y). Seven out of 8 patients had preoperative modified barium swallow (MBS). Five out of seven showed improvement in aspiration. Three out of six (50%) patients who did not have gastrostomy tube preoperatively, were able to avoid gastrostomy tube. No adverse effects were noted following IL. One patient with severe tracheomalacia ultimately required tracheostomy 5 months after IL.

CONCLUSION

Injection laryngoplasty appears to be a safe and effective therapeutic option in neonates and young children with unilateral vocal cord immobility and associated aspiration. It may be an effective treatment to improve aspiration and avoid gastrostomy tube placement. Further investigation is warranted.

LEVEL OF EVIDENCE

4.

Structural Fat Grafting to Improve Outcomes of Vocal Folds’ Fat Augmentation: Long-term Results

Objective

Evaluating the long-term outcomes of vocal fold structural fat grafting.

Study Design

Case series with chart review.

Setting

University hospital.

Subjects and Methods

Seventy-nine dysphonic patients (16-82 years; 55 with unilateral laryngeal paralysis and 24 with vocal fold scarring) underwent vocal fold fat injection. Fat was harvested by low-pressure liposuction and then processed by centrifugation. Refined fat aliquots were placed in the vocal fold and paraglottic space in multiple tunnels to enhance graft neovascularization. All patients were followed for 12 months, 15 for 3 years, and 5 for 10 years with videolaryngostroboscopy, maximal phonation time (MPT) measurement, Voice Handicap Index (VHI) questionnaire, and GRBAS (grade, roughness, breathiness, asthenia, strain) perceptual evaluation. Laryngeal computed tomography (CT) and/or magnetic resonance imaging (MRI) studies were performed in 16 patients 3 to 28 months postoperatively; MRI was repeated in 5 cases 12 to 18 months after the first radiological study.

Results

The voice quality of all patients improved after surgery, and long-term stability was confirmed by MPT, GRBAS, and VHI ( P ranging between .004 and <.001). The results achieved 1 year postoperatively remained stable at 3 and 10 years. Videolaryn-gostroboscopy showed improved glottic closure in all patients despite a limited amount of fat resorption. CT and MRI demonstrated survival of the fat grafts in all of the 16 examined cases. Serial MRI scans showed no change in graft size over time.

Conclusions

The reported clinical and radiological data demonstrate that fat is an effective filler for permanent vocal fold augmentation if the refined micro-aliquots are placed in multiple tunnels.

Parameters and Scales Used to Assess and Report Findings From Stroboscopy: A Systematic Review

OBJECTIVE

Laryngeal endoscopy with stroboscopy, a critical component of the assessment of voice disorders, is rarely used as a treatment outcome measure in the scientific literature. We hypothesized that this is because of the lack of a widely used standardized, validated, and reliable method to assess and report laryngeal anatomy and physiology, and undertook a systematic literature review to determine the extent of the inconsistencies of the parameters and scales used in voice treatment outcome studies.

STUDY DESIGN

Systematic literature review.

METHODS

We searched PubMed, Ovid, and Cochrane for studies where laryngeal endoscopy with stroboscopy was used as a treatment outcome measure with search terms representing "stroboscopy" and "treatment" guided by Preferred Reporting Items for Systematic Reviews and Meta-Analyses statement standards.

RESULTS

In the 62 included articles, we identified 141 terms representing 49 different parameters, which were further classified into 20 broad categories. The six most common parameters were magnitude of glottal gap, mucosal wave amplitude, location or shape of glottal gap, regularity of vibration, phase symmetry, and presence and size of specific lesions. Parameters were assessed on scales ranging from binary to 100 points. The number of scales used for each parameter varied from 1 to 24, with an average of four different scales per parameter.

CONCLUSIONS

There is a lack of agreement in the scientific literature regarding which parameters should be assessed to measure voice treatment outcomes and which terms and scales should be used for each parameter. This greatly diminishes comparison and clinical implementation of the results of treatment outcomes research in voice disorders. We highlight a previously published tool and recommend it for future use in research and clinical settings.

Calcium Hydroxylapatite Pulmonary Embolism after Percutaneous Injection Laryngoplasty

Injection medialization laryngoplasty is a procedure that has many advantages in treating vocal fold paralysis; however, undesired complications can occur. We experienced a case of a pulmonary embolism, suspected in a patient who had undergone an injection laryngoplasty with calcium hydroxylapatite (CaHA). The patient suffered dyspnea after undergoing the injection laryngoplasty. Chest embolism computed tomography (CT) scan revealed a new lesion of enhancing materials at the pulmonary vasculature in the right upper lobe. The CaHA embolism was suspected, and the patient was treated with warfarin for 12 months. The patient's symptom of dyspnea nearly disappeared and a follow up chest embolism CT scan revealed no signs of the previous lesion. Thus, we would like to report this rare case along with a review of the literature.

Injection laryngoplasty as miniinvasive office-based surgery in patients with unilateral vocal fold paralysis - voice quality outcomes

Introduction

Injection laryngoplasty (glottis augmentation) is the preferred method in surgical management of unilateral vocal fold paralysis (UVFP). Traditionally, these procedures are performed in the operating room. Nowadays, however, these procedures have moved into the office.

Aim

To evaluate the voice quality after transoral injection laryngoplasty under local anaesthesia in patients with unilateral vocal fold paralysis.

Material and methods

Fourteen subjects (5 women and 9 men) with unilateral vocal fold paresis (9 with right vocal fold paresis and 5 with left vocal fold paresis) were included in the study. The mean age of the group was 57.8 ±19.0 years (32–83 years). All of the injection laryngoplasties were performed transorally, under local anaesthesia. The injection material was calcium hydroxylapatite. Before and 1, 3 and 6 months after the procedure the following variables were evaluated: voice perception, videostroboscopy, acoustic analysis, aerodynamic evaluation, and the subjective rating of the voice quality by the patient.

Results

After injection laryngoplasty, complete glottal closure was achieved or there was a significant improvement in the glottal closure of each subject. We noted great improvement in the post-injection objective and subjective voice outcomes and patients reported improvement in the voice-related quality of life.

Conclusions

The transoral approach for injection laryngoplasty under local anaesthesia is an effective and safe way to treat incomplete glottal closure in patients with UVFP. The transoral approach is an efficient alternative to other surgical techniques used for vocal fold injection.

The usefulness of the transcricothyroid injection laryngoplasty via contralateral paramedian approach

OBJECTIVE

Several laryngeal injection techniques are technically difficult and have limitations. In this study, we modified a transcricothyroid approach for injections to enhance needle visualization during procedures. The objective of this study was to investigate the efficacy of this alternative injection technique.

METHODS

We performed a retrospective analysis of 51 patients who had undergone injection laryngoplasty for unilateral vocal paralysis between March 2014 and February 2015. In total, 17 patients underwent a transcricothyroid injection laryngoplasty via the contralateral paramedian approach (ILC) and 34 patients underwent transcricothyroid injection laryngoplasty via the conventional approach (ipsilateral approach, ILI). Acoustic analyses, aerodynamic analyses, voice handicap index (VHI), and GRBAS scale were assessed pre-operatively and at 2 weeks and 3 months postoperatively.

RESULTS

From our acoustic and aerodynamic analyses, jitter, shimmer, noise-to-harmonic ratio (NHR), maximum phonation time (MPT), and mean flow rate (MFR) were all significantly improved in both groups after injection. VHI and GRBAS scales also improved postoperation. There were no significant differences between the pre-operative and postoperative subjective and objective parameters between both groups. The total injection volume used on the ILI group was larger than the volume given to the ILC group.

CONCLUSION

The transcricothyroid injection laryngoplasty via the contralateral paramedian approach is potentially more beneficial to performing injection laryngoplasty under local anesthesia. One important advantage of this approach to conventional approaches is its enhanced visualization of the needle during procedures.

Injection Laryngoplasty Using Micronized Acellular Dermis for Vocal Fold Paralysis

Objectives

Micronized acellular dermis has been used for nearly 15 years to correct glottic insufficiency. With previous demonstration of safety and efficacy, this study aims to evaluate intermediate and long-term voice outcomes in those who underwent injection laryngoplasty for unilateral vocal fold paralysis. Technique and timing of injection were also reviewed to assess their impact on outcomes.

Study Design

Case series with chart review.

Setting

Tertiary care center.

Subjects and Methods

Patients undergoing injection laryngoplasty from May 2007 to September 2012 were reviewed for possible inclusion. Pre- and postoperative Voice Handicap Index (VHI) scores, as well as senior speech-language pathologists’ blinded assessment of voice, were collected for analysis. The final sample included patients who underwent injection laryngoplasty for unilateral vocal fold paralysis, 33 of whom had VHI results and 37 of whom had voice recordings. Additional data were obtained, including technique and timing of injection.

Results

Analysis was performed on those patients above with VHI and perceptual voice grades before and at least 6 months following injection. Mean VHI improved by 28.7 points at 6 to 12 months and 22.8 points at >12 months ( P = .001). Mean perceptual voice grades improved by 17.6 points at 6 to 12 months and 16.3 points at >12 months ( P < .001). No statistically significant difference was found with technique or time to injection.

Conclusion

Micronized acellular dermis is a safe injectable that improved both patient-completed voice ratings and blinded reviewer voice gradings at intermediate and long-term follow-up. Further investigation may be warranted regarding technique and timing of injection.

Uso do programa MDVP em diferentes contextos: revisão de literatura

Resumo:Este estudo tem como objetivo descrever, a partir de revisão de literatura, a confiabilidade da análise acústica utilizando o Multi Dimensional Voice Program,comparação de suas medidas com outros programas de análise acústica; caracterização de vozes de diferentes grupos; e sua utilização para verificar os efeitos e eficácia de diferentes procedimentos terapêuticos. Realizou-se levantamento bibliográfico que priorizaram estudos dos últimos cinco anos, incluindo-se artigos cujo objetivo estivesse de acordo com o interesse da presente revisão. A pesquisa foi realizada nos bancos de dados das bases Lilacs, BIREME, PubMed, MedLine, Scielo e Google Schoolar, por meio dos descritores acoustic, speech acoustics e voice. As medidas mais utilizadas são frequência fundamental, jitter, shimmer e proporção harmônico-ruído. As medidas de tremor não apresentam boa confiabilidade. As medidas mais consistentes que apresentam alta concordância com outros programas de análise acústica são as relacionadas com a frequência fundamental. Diversos estudos buscam caracterizar diferentes tipos de vozes tais como as de sujeitos sem alterações vocais de ambos os sexos, buscando estabelecer parâmetro de normalidade para diferentes grupos populacionais. Além disso, alguns estudos caracterizam vozes com diferentes distúrbios. A análise acústica é um recurso objetivo e necessário na avaliação de pacientes com distúrbio vocal e, principalmente, na comparação de diversos tipos de tratamento.

Transillumination for needle localization in the larynx

OBJECTIVES/HYPOTHESIS

Transillumination through laryngeal soft tissue may be used to direct percutaneous transcricothyroid membrane subepithelial needle placement in the larynx.

STUDY DESIGN

Cadaver simulation (canine and human).

METHODS

Lighted devices, including sialendoscopes and fiberoptic cables, were tested as transilluminating obturators in trocars and needles through multiple studies to identify appropriate illumination, monitoring, and equipment for successful localization of needle/trocar tips placed within laryngeal tissue.

RESULTS

Lighted 250-micron fiberoptic cables within 23-gauge needles were successfully placed percutaneously through the cricothyroid membrane and maneuvered submucosally into Reinke's space, the midlateral vocal fold, and through the thyroarytenoid gap with monitoring via flexible transnasal laryngoscopy. Technical adaptations in the course of study permitted successful simulation of clinical use in full cadaver study for accurate injection laryngoplasty, confirmed by laryngeal dissection following collagen injection.

CONCLUSIONS

Small caliber fiberoptic cables are useful as transilluminating obturators to accurately direct needle position within laryngeal tissue. Clinical application of this new technique is anticipated to improve the accuracy of percutaneous needle localization in the larynx, as well as to assist in directed instrumentation of the larynx from an external approach.

LEVEL OF EVIDENCE

N/A.

Transnasal injection laryngoplasty

OBJECTIVES

The objective of this study was to evaluate the role of transnasal fiber-optic injection laryngoplasty in the treatment of glottic insufficiency.

METHODS

Video recordings of 16 patients who underwent fiber-optic injection laryngoplasty for the treatment of glottic insufficiency were reviewed. Outcome measures included perceptual evaluation using the GRBAS (grading, roughness, breathiness, asthenia, straining) classification, laryngeal videostroboscopy, and frame-by-frame analysis to assess the extent, shape, and duration of glottic closure.

RESULTS

Nine patients were ultimately included in this study. Their mean age was 66.2 years, with 7 men and 2 women. The most common symptoms were dysphonia and aspiration, and the most common diagnosis was vocal fold paralysis. Patients underwent transnasal fiber-optic injection laryngoplasty with hyaluronic acid as a filling material (0.2-0.8 mL). The procedure was well tolerated by all patients, with improvement in the phonatory symptoms and aspiration in 66.66% and 50% of patients, respectively. There were significant decreases in the mean scores of all perceptual parameters (P<.05 for all). All subjects had glottal gap preoperatively that was closed completely in 66.66% and reduced to <2 mm in 33.33%. The mean closed quotient significantly increased from 0.10 to 0.51 (P<.05).

CONCLUSIONS

Transnasal fiber-optic injection laryngoplasty is a safe procedure well tolerated by patients with good results.

Favorable vocal fold wound healing induced by platelet-rich plasma injection

OBJECTIVES

To introduce a new injection material for vocal fold diseases, which could be readily translated to clinical practice, we investigated the effectiveness of platelet-rich plasma (PRP) injection on the injured vocal fold in terms of histological recovery.

METHODS

Blood samples were drawn from New Zealand White rabbits and PRP was isolated through centrifugation and separation of the samples. Using a CO2 laser, we made a linear wound in the 24 vocal fold sides of 12 rabbits and injected each wound with PRP on one vocal fold side and normal saline (NS) on the other. Morphologic analyses were conducted at 2, 4, and 12 weeks after injection, and inflammatory response, collagen deposit, and changes in growth factors were assessed using H&E and masson trichrome (MT) staining and western blot assay.

RESULTS

PRP was prepared in approximately 40 minutes. The mean platelet concentration was 1,315,000 platelets/mm(3). In morphological analyses, decreased granulation was observed in the PRP-injected vocal folds (P<0.05). However, the irregular surface and atrophic change were not difference. Histological findings revealed significant inflammation and collagen deposition in NS-injected vocal folds, whereas the PRP-injected vocal folds exhibited less (P<0.05). However, the inflammatory reaction and fibrosis were not difference. In western blot assay, increased amounts of growth factors were observed in PRP-injected vocal folds.

CONCLUSION

Injection of injured rabbit vocal folds with PRP led to improved wound healing and fewer signs of scarring as demonstrated by decreased inflammation and collagen deposition. The increased vocal fold regeneration may be due to the growth factors associated with PRP.

A synthetic, self-oscillating vocal fold model platform for studying augmentation injection

OBJECTIVE

To design and evaluate a platform for studying the mechanical effects of augmentation injections using synthetic, self-oscillating vocal fold models.

STUDY DESIGN

Basic science.

METHODS

Life-sized, synthetic, multilayer, self-oscillating vocal fold models were created that simulated bowing via volumetric reduction of the body layer relative to that of a normal, unbowed model. Material properties of the layers were unchanged. Models with varying degrees of bowing were created and paired with normal models. Following initial acquisition of data (onset pressure, vibration frequency, flow rate, and high-speed image sequences), bowed models were injected with silicone that had material properties similar to those used in augmentation procedures. Three different silicone injection quantities were tested: sufficient to close the glottal gap, insufficient to close the glottal gap, and excess silicone to create convex bowing of the bowed model. The above-mentioned metrics were again taken and compared. Pre- and post-injection high-speed image sequences were acquired using a hemilarynx setup, from which medial surface dynamics were quantified.

RESULTS

The models vibrated with mucosal wave-like motion and at onset pressures and frequencies typical of human phonation. The models successfully exhibited various degrees of bowing which were then mitigated by injecting filler material. The models showed general pre- to post-injection decreases in onset pressure, flow rate, and open quotient and a corresponding increase in vibration frequency.

CONCLUSION

The model may be useful in further explorations of the mechanical consequences of augmentation injections.

Autologous platelet-poor plasma gel for injection laryngoplasty

PURPOSE

To overcome the potential disadvantages of the use of foreign materials and autologous fat or collagen, we introduce here an autologous plasma gel for injection laryngoplasty. The purpose of this study was to present a new injection material, a plasma gel, and to discuss its clinical effectiveness.

MATERIALS AND METHODS

From 2 mL of blood, the platelet poor serum layer was collected and heated at 100°C for 12 min to form a plasma gel. The plasma gel was then injected into a targeted site; the safety and efficacy thereof were evaluated in 30 rats. We also conducted a phase I/II clinical study of plasma gel injection laryngoplasty in 11 unilateral vocal fold paralysis patients.

RESULTS

The plasma gel was semi-solid and an easily injectable material. Of note, plasma gel maintains the same consistency for up to 1 year in a sealed bottle. However, exposure to room air causes the plasma gel to disappear within 1 month. In our animal study, the autologous plasma gel remained in situ for 6 months in animals with minimal inflammation. Clinical study showed that vocal cord palsy was well compensated for with the plasma gel in all patients at two months after injection with no significant complications. Jitter, shimmer, maximum, maximum phonation time (MPT) and mean voice handicap index (VHI) also improved significantly after plasma gel injection. However, because the injected plasma gel was gradually absorbed, 6 patients needed another injection, while the gel remained in place in 2 patients.

CONCLUSION

Injection laryngoplasty with autologous plasma gel may be a useful and safe treatment option for temporary vocal cord palsy.