Quantification of injection force mechanics during injection laryngoplasty

Approach to differentiate between hyaluronic acid skin quality boosters and fillers based on their physicochemical properties

BACKGROUND

The clinical indications, applications, and effect of the injectable hyaluronic acid range skin quality boosters (SQBs) are different than those of filler products. Material properties are increasingly being discussed for differentiation and in connection with clinical effects and esthetic indications.

AIMS

The aim of this study is to evaluate whether SQB products can be differentiated from filler products by their physicochemical material properties.

MATERIAL AND METHODS

Physicochemical properties (extrusion force, swelling degree, rheology, and cohesivity) of two SQBs (BEL_R , JUV_VE ) were compared with those of fillers (BEL_B , JUV_VT ) using the same manufacturing technology.

RESULTS

Cohesivity was almost equal for SQBs and fillers. Few statistically significant differences in physicochemical properties were found. Properties of SQBs differed from fillers mainly in their delta of rheological properties and extrusion force.

CONCLUSION

In this study, physicochemical differences between SQB and filler were determined and described, supporting the presence of two categories and their different clinical indications and applications.

Fibrin Gel Suspended Autologous Chondrocytes as Cell-based Material for long-term Injection Laryngoplasty

OBJECTIVES/HYPOTHESIS

Injection laryngoplasty of materials for unilateral vocal-fold paralysis has shown various results regarding the long-term stability of the injected material. We evaluated a fibrin-gel based cell suspension with autologous chondrocytes in-vitro and in-vivo as long-term-stable vocal-fold augmentation material in an animal model.

STUDY DESIGN

This study compises an in vitro cell-culture part as well as an in vivo animal study with New Zealand White Rabbits.

METHODS

In in-vitro experiments, auricular chondrocytes harvested from 24 New Zealand White Rabbits cadavers were cultivated in pellet cultures to evaluate cartilage formation for 4 weeks using long-term-stable fibrin gel as carrier. Injectability and injection volume for the laryngoplasty was determined in-vitro using harvested cadaveric larynxes. In-vivo 24 Rabbits were biopsied for elastic cartilage of the ear and autologous P1 cells were injected lateral of one vocal cord into the paraglottic space suspended in a long-term-stable fibrin gel. Histologic evaluation was performed after 2, 4, 12, and 24 weeks.

RESULTS

During 12-week pellet culture, we found extracellular matrix formation and weight-stable cartilage of mature appearance. In-vivo, mature cartilage was found in two larynxes (n = 6) at 4 weeks, in four (n = 6) at 12 weeks, and in five (n = 6) at 24 weeks mostly located in the paraglottic space and sometimes with spurs into the vocalis muscle. Surrounding tissue was often infiltrated with inflammatory cells. Material tended to dislocate through the cricothyroid space into the extraglottic surrounding tissue.

CONCLUSIONS

A cell-based approach with chondrocytes for permanent vocal-fold augmentation has not previously been reported. We have achieved the formation of structurally mature cartilage in the paraglottic space, but this is accompanied by difficulties with dislocated material, deformation of the augmentation, and inflammation.

LEVEL OF EVIDENCE

N/A Laryngoscope, 131:E1624-E1632, 2021.