Polydimethylsiloxane versus polytetrafluoroethylene for vocal fold medialization: histologic evaluation in a rabbit model

Histopathologic Evaluation of Hyaluronic Acid and Plasma-Rich Platelet Injection into Rabbit Vocal Cords: An Experimental Study

Objective

Various materials are used by otolaryngologists for vocal cord injections in the management of vocal cord paralysis. An ideal injection material should be long-term effective, readily available, cheap, easy to prepare, have no donor morbidity, easy to use, biocompatible, resistant to resorption or migration, and easy to extract during revision. In this study, we aimed to see the histopathological effects of hyaluronic acid (HYA) and platelet-rich plasma (PRP) injections into the vocal cords of New Zealand rabbits.

Methods

PRP was injected into the right vocal cords of twelve rabbits, which was prepared from their serum (PRP group). HYA was injected into the left vocal cords of first six rabbits (numbered 1-6) (HYA group), and the left vocal cords of the other six rabbits (numbered 7-12) were followed with no intervention (control group). Two months later, histomorphological findings in the vocal cords were assessed by two experienced pathologists in seven parameters: chronic inflammation, mucosal atrophy, necrosis, neovascularization, fibrosis, foreign body reaction, and muscular atrophy. They were scored double-blinded as negative (0), mild (+1), moderate (+2), and severe (+3). Fisher's chi-square test was used to evaluate any statistical significance among the three groups.

Results

Chronic inflammation, mucosal atrophy, necrosis, foreign body reaction, and muscular atrophy parameters were scored as "0" for each preparate by both pathologists. For neovascularization and fibrosis, a stasistically significant difference was seen among the three groups (p<0.05). Neovascularization was increased in the PRP and HYA groups compared with the control group. No significant difference was observed in fibrosis when the groups were compared separately. After two months, two of the six vocal cords injected with HYA revealed HYA; however, none of the PRP-injected vocal cords showed PRP.

Conclusion

HYA and PRP can be safely injected into vocal cords. Our findings show that HYA is a biocompatible and safe injection material for clinical use. Only two of the six vocal cords showed HYA at the end of two months, suggesting that HYA is a short-term effective material. Similarly, PRP was also shown to be a short-term effective material and can be used in patients for testing purpose before using a long-term effective material. The advantages of PRP are that it is inexpensive, readily available, and completely inert as it is prepared from the subject itself.

Polydimethylsiloxane Particles for Permanent Injection Laryngoplasty

Objectives:

Polydimethylsiloxane (PDMS) particles are a nonresorbable material that allows for permanent vocal fold augmentation. This study investigated morbidity and voice quality in patients treated for unilateral vocal fold paralysis by injection of PDMS particles.

Methods:

Fourteen patients who had neurogenic unilateral vocal fold paralysis of different causes were included in this prospective study. Each patient underwent videostroboscopic assessment before and after operation. Friedrich's dysphonia index (DI), a score system combining subjective and objective parameters, was used to describe voice quality. A DI of 0 reflects a normal voice, and a DI of 3 stands for complete aphonia. The PDMS particles were injected into the paraglottic space by microlaryngoscopy under general anesthesia.

Results:

The median follow-up was 4.1 months. There was no complication attributable to the injection of PDMS particles. The mean DI was 2.8 before operation. After the operation, voice quality improved significantly in each patient, as reflected by a mean postinjection DI of 1.4.

Conclusions:

Particles of PDMS provide a relatively safe and minimally invasive option for permanent vocal fold augmentation. The functional results in terms of voice improvement are comparable to those obtained with other techniques, including thyroplasty. In the European Community, PDMS particles are officially approved for use in the human larynx.

Comparison of lyophilized glutaraldehyde-preserved bovine pericardium with different vascular prostheses for use as vocal cords implants: experimental study

This study compared the use of lyophilized glutaraldehyde-preserved bovine pericardium (LGPBP), polytetrafluoroethylene (PTFE), polyethylene terephthalate (PET), and Teflon felt (TF) as implants for vocal cords (VC) medialization and aimed to assess the endoscopic, macroscopic, and microscopic VC changes after medialization in a canine model. In 18 mongrel dogs, the right VC were medialized with LGPBP and the left were implanted as follows: Group I (n = 6): LGPBP and PTFE; Group II (n = 6): LGPBP and PET; Group III (n = 6): LGPBP and TF. Surgical handling of the implants was compared. Three months after surgery, macroscopic and microscopic changes of VC and implants were evaluated. LGPBP offered the best surgical handling (p = 0.005, Kruskal-Wallis). TF implants showed extrusion (p = 0.005, Kruskal-Wallis) and severe inflammation. All VC formed fibrous capsules around the implants; the ones developed by LGPBP implants were thinner (p = 0.001, ANOVA, Tukey). VC implanted with synthetic materials showed eosinophilic infiltration (p = 0.01, Kruskal-Wallis). We concluded that the LGPBP could be used as an implant for VC medialization because it is biocompatible, easy to handle and remove during surgical procedures, and nonabsorbable or extrudable and produces an inflammatory reaction similar to PTFE and PET.

A pilot study of macrophage responses to silk fibroin particles

Silk fibroin (SF) shows promise for tissue engineering and other biomedical applications due to its excellent biocompatibility, unique biomechanical properties, and controllable biodegradability. The particulate form of SF materials may have many potential uses, including the use as a filler for tissue defects or as a controlled-release agent for drug delivery. However, many past in vivo and in vitro studies evaluating the biocompatibility and biodegradability of SF have involved bulk implants. It is essential to evaluate the inflammatory effects of SF particles before further use. In this study, two different sizes of SF particles were evaluated to assess their impact on the release of tumor necrosis factor (TNF)-α, interleukin (IL)-1β, and IL-6, in comparison with lipopolysaccharide positive control stimulation. The inflammatory processes were characterized using real-time reverse transcription polymerase chain reaction, enzyme-linked immunosorbent assay, and light microscopy evaluations. The results indicated that small silk fibroin particles and large silk fibroin particles, in culture with RAW 264.7 murine macrophage cells for 24 h, caused up-regulation of mRNA coding for TNF-α, which indicated that both size of particles have potential inflammatory effects. There was a statistically significant increase in this up-regulation under small silk fibroin stimulation. However, the immunosorbent assay suggested that there was virtually no observed release of IL-1β, IL-6, or TNF-α, relative to the control group. The results suggest that SF particles of the chosen dimensions may have good biocompatibility in culture with RAW 264.7 murine macrophages.

[Glutaraldehyde-preserved and lyophilized bovine pericardium as materials for medialization of the vocal folds in an animal model]

INTRODUCTION

Glutaraldehyde-preserved bovine pericardium (GBP) and lyophilized GBP (LGBP) have been used successfully in repairing several anatomical defects, but their effectiveness and safety as implants to vocal cords (VC) have not been reported.

OBJECTIVE

The aim of this study was to evaluate the use of GBP and LGBP as materials for medialization thyroplasty, as well as to assess the endoscopic, macroscopic and microscopic VC changes after medialization in an experimental canine model.

MATERIAL AND METHODS

In 12 healthy mongrel dogs, the right VC were medialized using pericardium and the left with polytetrafluoroethylene (PTFE). Group 1 (n=6): GBP and Group 2 (n=6): LGBP. The surgical manoeuvrability of the implants was compared. The animals were evaluated clinically and endoscopically. Three months after surgery, the larynges were assessed macro- and microscopically.

RESULTS

Both GBP and LGBP implants showed better surgical manoeuvrability (Kruskal-Wallis, P=.005). Endoscopic and macroscopic studies showed no evidence of granulomas, absorption or extrusion of the implant. At the end of the study, greater thickness was observed in VC implanted with PTFE. Microscopically, all the VC developed fibrous capsules surrounding the implants and similar chronic inflammation reaction. The VC implanted with PTFE presented eosinophilic infiltration (Kruskal-Wallis, P<.05).

CONCLUSION

Both GBP and LGBP can be used as implants for VC medialization because they are biocompatible, have easy surgical manoeuvrability, do not suffer absorption, migration or extrusion and produce inflammation reactions similar to those of PTFE.

MR evaluation of PDMS injections in head and neck tissues: a pilot study

OBJECTIVES

To describe the magnetic resonance (MR) appearance of polydimethylsiloxane (PDMS) injections in the head and neck region.

STUDY DESIGN

Retrospective review of MR images from a case series.

METHODS

MR images of 10 patients, who underwent PDMS injections at our department, were reviewed. Data from imaging were collected and analyzed.

RESULTS

After injection, PDMS can be identified in MR images, particularly in T2-weighted images in the early stages. Its MR characteristics are similar to silicone in other regions, but with time, its appearance can change.

CONCLUSIONS

The integration of PDMS with tissues may also be reflected in changes in MR appearance, as a result of an increased amount of fibrous tissue in the region injected. Radiologists and ENT specialists may benefit from knowledge of the MR characteristics and variability in appearance of PDMS in human tissues for improving image interpretation.