Viscosity of Materials for Laryngeal Injection: A Review of Current Knowledge and Clinical Implications

Prolonged persistence of hyaluronic acid after suboptimal vocal fold injection

Hyaluronic acid (HA) is a commonly used injectable material in temporary vocal fold injections (VFI) in patients with unilateral vocal fold paralysis (UVFP). Hyaluronic acid has generally been known for its three-six months of longevity following VFI. Owing to recent advances in cross-linking technologies, the longevity of HA-based materials, including deep-volumizing cross-linked HA used in VFI, has been improved. However, persisting injectable material in the subepithelial space poses undesirable complications following VFI. Herein, we report 2 cases of unexpected persistence of superficially injected cross-linked HA. In the first case, a 70-year-old man with iatrogenic UVFP received VFI with cross-linked HA three years ago and was referred for persistent dysphonia. Previously injected HA spilled out from the vocal fold (VF) when an epithelial incision was made in the subepithelial cystic lesion. In the second case, a 72-year-old woman with iatrogenic UVFP received VFI with cross-linked HA that migrated into the subepithelial space. Diffuse swelling of the injected VF caused dysphonia that lasted for a year. The previously injected HA spilled out when an epithelial incision was made in the swollen VF. Since superficially injected deep-volumizing cross-linked HA can persist for up to three years, laryngologists should be aware of possible sequelae upon suboptimal VFI with cross-linked HA.

Duration of Effect and Associated Factors of Injection Laryngoplasty

OBJECTIVE

Injection laryngoplasty (IL) has become a mainstay in the treatment of unilateral vocal fold paralysis due to technical ease and avoidance of open surgery. The duration of IL effect depends on the injected material and has not been defined clearly. We aimed to define the effective duration of IL and to investigate the associated factors.

METHODS

Fifty-nine patients who underwent IL for unilateral vocal fold paralysis were included. IL was performed using a cricothyroid membrane approach under local anesthesia. During follow-up, in cases that developed subjective hoarseness with objective glottic insufficiency, a second IL was performed, and loss of IL effect was recorded. The duration of IL was analyzed using Kaplan-Meier estimates, and the associations between duration of effect and various factors such as postinjection voice therapy, injected material, and cause of paralysis were investigated using log-rank test.

RESULTS

Of 59 patients, 20 (33.9 %) received a second IL. The median time interval between the first and second IL was 3.3 months (95% CI, 0.4∼27.8 months). The mean duration of effect after IL was 42.5 months (95% CI, 32.1∼52.9 months), and the rate of persisting effect was 63.4% at 1-year after IL (1-year effect rate) and 59.4% at 2 years after IL. The 1-year effect rate was 80.8% in cases with postinjection voice therapy and 57.8% in those without postinjection voice therapy (P = 0.084). Injected material, DM, HTN, patient age and sex, and cause of paralysis had no effect on the 1-year effect rate.

CONCLUSIONS

The mean duration of IL effect was 42.5 months, and the rate of persisting effect was 63.4% at 1-year after IL. There were no significant factors affecting the duration of effect, although the duration tended to be slightly longer in cases with postinjection voice therapy. Further study with a prospective, randomized design is needed.

Injection medialisation laryngoplasty: an alternative approach for challenging cases

OBJECTIVE

Conventional injection medialisation laryngoplasty techniques may be compromised by patient-specific factors such as marked kyphosis, an anteriorly positioned larynx or intolerance to nasendoscopy. This paper describes a technique for successful injection medialisation laryngoplasty where conventional methods are precluded, in an 88-year-old man with presbyphonia on a background of Parkinson's disease.

METHODS

After induction of general anaesthesia, a transoral introducing needle, shaped by tactile manipulation to match the curvature of a 'C-MAC' intubating video-laryngoscope 'D-blade' attachment, was introduced until visible above the glottis. The implant material was then injected into the paraglottic space as normal until satisfactory medialisation of the vocal fold was achieved.

RESULTS

When reviewed in the out-patient clinic four weeks later, the patient's post-operative Voice Handicap Index score fell to 6, from a pre-operative score of 21.

CONCLUSION

By utilising commonly available equipment and anaesthetic support to recreate the views and access conventional nasendoscopy and laryngoscopy facilitate, this novel procedure provides a viable and proven alternative in uncommon but challenging cases.

In Vivo Automatic and Quantitative Measurement of Adult Human Larynx and Vocal Fold Images

INTRODUCTION

Qualitative laryngoscopy belongs to a diagnostic routine. Nevertheless, quantitative morphometric measurements of laryngeal structures remain challenging. This study aimed to introduce a special laser projection device that can facilitate computer-assisted digitalized analysis and provide important quantitative information for diagnostics and treatment planning.

MATERIALS AND METHODS

The laryngeal images were captured with our device, which contained two parallel laser beams in order to provide the scaling reference. The maximum length of the vocal fold during respiration and vibration (phonation), vocal width at midpoint, total fold area, maximum cross-sectional area of the glottic space, and maximum vocal fold angle were determined and calculated. These parameters were analyzed and compared on the basis of age, sex, body height, body weight and body mass index.

RESULTS

A total of 87 subjects were enrolled in this study, comprising 39 males and 48 females. The age range for all subjects was 21 to 80 years old. The maximum value of the glottic area and vocal angle showed no significant gender difference. Both the respiration and vibration vocal fold length was significantly longer in males than in females. The vocal width revealed no gender difference, but the fold area during both respiration and phonation was significantly larger in men than in women. As for the respiration-to-vibration ratio of the vocal length, there was a trend, but without statistical significance (P = 0.06), toward a higher length compression ratio in men than in women. Meanwhile, age was found to have a strong relationship with vocal width during phonation. The width of vibration vocal fold decreased with aging significantly.

CONCLUSION

Our innovative module can provide reference parameters, which makes it possible to directly estimate the objective absolute values of relevant laryngeal structures. Our non-invasive approach can be used during routine laryngoscopy and the findings easily documented. In future, we can extend its clinical application to measure subtle laryngeal or hypopharyngeal changes, which are difficult to objectively quantify.

Variations in Practices and Preferences of Vocal Fold Injection Materials: A National Survey

BACKGROUND

Vocal fold injection augmentation (VFI) is a common procedure for the treatment of glottic insufficiency. Material options for VFI and decisions regarding material selection are not standardized and often based on clinician preference.

OBJECTIVE

This study aims to understand the variations in provider preference and utilization of injectable materials for VFI.

METHODS

A 40-question survey was sent to 158 academic laryngologists. Questions pertained to the type of injectable materials used including brand preferences and rationale for preferences.

RESULTS

Ninety-seven of the 158 laryngologists contacted participated in the survey (61.4%). The most frequently used injectable materials were Hyaluronic Acid (HA)-based products. Carboxymethylcellulose (CMC)-based products were preferred for trial augmentation (57.2%), HA-based products were preferred for acute/subacute vocal fold paralysis, presbyphonia, and sulcus/scar (54.2%, 61.5%, 44.7%, 41.7% respectively), and Calcium Hydroxyapatite (CaHA)-based products were preferred for long-term paralysis (28.1%). CMC-based products were discontinued by 21.8% of participants, largely due to quick material resorption. 17.8% of participants discontinued HA-based products largely due to adverse events and 26.0% abandoned CaHA-based products mostly due to inflammatory properties causing vocal fold stiffness and material unpredictability. Over 30% of respondents reported wanting to reinitiate micronized alloderm Cymetra® as an available injectable.

CONCLUSION

Our survey demonstrated that there are significant variations in practice and preferences in regard to injectable material selection for VFI. As there is limited data on the direct material comparison, understanding the rationale behind these variations is crucial to guide new providers in material selection and provide information to patients undergoing these procedures.

LEVEL OF EVIDENCE

5 Laryngoscope, 133:1176-1183, 2023.

Autologous Fat Plus Platelet-Rich Plasma versus Autologous Fat Alone on Sulcus Vocalis

Sulcus vocalis is a frequent cause of glottic insufficiency that leads to incomplete vocal fold closure during phonation. Type II sulcus vocalis is defined as a partial defect of the lamina propria (LP). Treatment with fillers, such as fat or hyaluronic acid (HA), in the vocal folds is widely used, but the duration of effect is variable. Platelet-rich plasma (PRP) can enhance the survival of autologous fat in fat grafting, and also is used to treat sulcus vocalis. This study aimed to compare the effectiveness of autologous fat graft versus fat graft plus PRP to treat type II sulcus vocalis. Thirty-four patients with a voice handicap index (VHI) ≥ 11 were randomized to two groups, which received LP injections of fat graft (n = 17) or fat graft plus PRP (n = 17). At 1 month and 6 months after injection, the VHI decreased significantly in both groups. The fat plus PRP group had better Jitter, Shimmer, and noise to harmonic ratio (NHR) in 1 month and 6 months after surgery. The fat plus PRP group resulted in lower VHI scores one month after surgery, and stroboscopy revealed sustained smaller gaps after six months. These results indicate that a combination of fat graft plus PRP is safe and effective for treating sulcus vocalis type II and associated vocal atrophy.

Autologous Adipose Tissue Injection of Vocal Cords in Presbyphonia

OBJECTIVE

This series evaluates the long-term results of autologous adipose injection (AAI) in patients older than 65 years with presbyphonia.

STUDY DESIGN

Retrospective cohort study.

SETTING

Academic secondary medical center.

METHODS

This was a retrospective study with a minimum follow-up of 12 months. All patients underwent AAI for atrophy of both vocal folds due to presbyphonia. We measured subjective parameters as Voice Handicap Index-10 (VHI-10) or GRBAS scale (grade, roughness, breathiness, asthenia, strain) and objective measures such as maximum phonation time (MPT) or square pixel closure defect. We reviewed the medical records of patients undergoing AAI during the 2011-2018 period. An analysis of the demographic variables of the group was performed, as well as the values of VHI-10, GRBAS, and MPT, and the minimum closure defect measured in square pixels and the number of closed frames in the glottal cycle before and after the intervention.

RESULTS

At 12 months, 17 of 18 patients reported subjective and VHI-10 improvement. The mean preoperative VHI-10 (26.7) was significantly higher than the postoperative value (14.4), and the GRBAS scale had a preoperative mean of 8.7 and a postoperative mean of 4.3, both with statistical significance. MPT increased from 7.7 to 12.4 seconds (P < .0001). The minimum closure defect measurements obtained in square pixels changed from 305 to 124, achieving complete closure in 3 patients. The closed phase of the glottal cycle change from 14.3% to 38.2% after the AAI.

CONCLUSIONS

AAI improves long-term vocal fold closure, demonstrating utility in patients with presbyphonia.

Adverse Reaction to Restylane: A Review of 63 Cases of Injection Laryngoplasty

The aim of this study is to review the prevalence of adverse reactions to cross-linked hyaluronic acid (HA) following injection laryngoplasty and discuss possible mechanisms. A retrospective chart review of patients who underwent injection laryngoplasty using HA was conducted. Demographic data included age, gender, etiology, site of injection, and amount injected. Adverse reaction was diagnosed by the presence of inflammatory reaction at the injection site. A total of 63 patients were included, divided into 41 males and 22 females with a mean age of 51.76 years. The most common etiology was vocal cord paralysis (n = 53), followed by postcordectomy, puberphonia, and vocal fold atrophy and bowing. The average amount injected was 0.56 (0.22) mL. Three cases out of 63 patients developed an adverse reaction and presented with airway symptoms, namely, progressive shortness of breath and globus 2 to 3 days postinjection. Adverse reactions following HA injection laryngoplasty may occur with life-threatening symptoms.

Volumetric analysis of vocal fold atrophy via magnetic resonance imaging

Objective

To quantitatively test the hypothesis that older patients have increased thyroarytenoid muscle atrophy by comparing thyroarytenoid muscle volumes across different age groups.

Methods

A retrospective chart review was conducted. The study included 111 patients with no history of laryngeal pathology. Two investigators reviewed magnetic resonance imaging studies of these patients and manually traced the thyroarytenoid muscles on multiple slices bilaterally. Thyroarytenoid muscle volumes were then computed using imaging analysis software. Patients were stratified into three age groups (18–50 years, 51–64 years, and 65 years or older) for comparison.

Results

Intra- and inter-rater reliabilities were excellent for all measurements (intraclass correlation co-efficient > 0.90). There was no statistically significant difference in the mean volumes of left and right thyroarytenoid muscles in all age and gender groups.

Conclusion

Given the lack of statistically significant difference in thyroarytenoid muscle volume between age groups on magnetic resonance imaging, the prevailing assumption that age-related thyroarytenoid muscle atrophy contributes to presbyphonia should be re-examined.

Impact of medialization laryngoplasty on dynamic nanomechanical vocal fold structure properties

OBJECTIVES/HYPOTHESIS

Although the primary goal of medialization laryngoplasty is to improve glottic closure, implant placement is also likely to alter the biomechanical properties of the vocal fold (VF). We sought to employ novel, nanoscale technology to quantify these properties following medialization based on the hypothesis that different medialization materials will likely yield differential biomechanical effects.

STUDY DESIGN

Ex vivo.

METHODS

Nine pig larynges were divided into three groups: control, Silastic (Dow Corning, Midland, Michigan, U.S.A.) block medialization, or Gore-Tex (W.L. Gore & Associates, Newark, Delaware) medialization. Laryngoplasty was performed on excised, intact larynges. The larynges were then bisected in the sagittal plane and each subjected to dynamic nanomechanical analysis (nano-DMA) at nine locations using a 250-μm flat-tip punch and frequency sweep-load profile across the free edge of the VF and inferiorly along the conus elasticus.

RESULTS

Silastic block and Gore-Tex implant introduced increased storage and loss moduli. Overall, storage moduli mean (maximum) increased from 38 kilopascals (kPa) (119) to 72 kPa (422) and 129 kPa (978) in control, Gore-Tex, and Silastic implants, respectively. Similarly, loss moduli increased from 13 kPa (43) to 22 kPa (201) and 31 kPa (165), respectively. Moduli values varied widely by location in the Silastic block and Gore-Tex groups. At the free VF edge, mean (maximum) storage moduli were lowest in the Gore-Tex group, 20 kPa (44); compared to control, 34.5 kPa (86); and Silastic, 157.9 kPa (978), with similar loss and complex moduli trends.

CONCLUSION

Medialization laryngoplasty altered VF structure biomechanical properties; Silastic and Gore-Tex implants differentially impact these properties.

LEVEL OF EVIDENCE

NA. Laryngoscope, 128:1163-1169, 2018.

Aryepiglottic fold augmentation as treatment for late-onset dysphagia following surgical treatment of recurrent laryngeal neuropathy

OBJECTIVE

Coughing and dysphagia have been described following prosthetic laryngoplasty (LP) with or without ventriculectomy/ventriculocordectomy (VE/VCE) for the treatment of recurrent laryngeal neuropathy. All previous case descriptions include patients with acute onset of clinical signs after surgery that persisted. The authors observed a late-onset of dysphagia and coughing months to years after LP ± VE/VCE. The condition was always associated with an abnormality of the aryepiglottic fold (AEF). Treatment options for those patients are limited. We suggest augmentation of the AEF as treatment for affected horses. The goal of the study was two-fold: Firstly, to describe a new condition of late-onset dysphagia in horses following LP ± VE/VCE associated with an abnormal appearance of the AEF, and secondly, to offer a minimally invasive and successful treatment for those patients.

MATERIAL AND METHODS

Six horses were presented because of dysphagia and coughing with an onset of months to years after LP ± VE/VCE. Endoscopically, the AEF always appeared thinner and more flaccid to a varying degree. The food path was traceable along the AEF into the trachea using dyed molasses. An initial injection of hyaluronic acid (HA) into the AEF led to immediate improvement of the dysphagia. The procedure was performed in the standing sedated horse. The needle was placed through the cricothyroid ligament and the injection performed under endoscopic guidance.

RESULTS

All horses tolerated the injection well. Injection of HA was successful only in the short term in all cases and repeated injections were needed for permanent resolution using either cross-linked HA, polyacrylamide hydrogel or platelet rich plasma.

CONCLUSION AND CLINICAL RELEVANCE

Horses may develop dysphagia and coughing months to years after LP ± VE/VCE as a late-onset complication. The condition seems to be associated with an abnormal appearance and function of the AEF. Successful treatment is possible by augmenting the AEF. However, careful patient selection is mandatory.

Use of acellular dermal matrices in laryngotracheal and pharyngeal reconstruction: systematic review

Background:

Acellular dermal matrices are increasingly used in laryngotracheal and pharyngeal reconstruction, but specific indications and the type of acellular dermal matrix used vary. The authors systematically reviewed outcomes relating to acellular dermal matrix use in head and neck reconstruction.

Methods:

Electronic databases were searched through 1 May 2016 for literature on acellular dermal matrix use in laryngotracheal and pharyngeal reconstruction. Studies were appraised for surgical indications, outcomes and study design.

Results:

Eleven publications with 170 cases were included. Eight articles reported on acellular dermal matrix use in oncological reconstruction. Most studies were case series; no high-level evidence studies were identified. Graft extrusion was more common in non-oncological applications. In general, post-oncological reconstruction with an acellular dermal matrix demonstrated complication rates similar to those reported without an acellular dermal matrix.

Conclusion:

Evidence in support of acellular dermal matrix use in head and neck reconstruction is generally poor. Prospective comparative studies are required to define the indications, safety and effectiveness of acellular dermal matrices in laryngotracheal and pharyngeal reconstruction.

Adverse Reaction to Hyaluronic Acid Injection Laryngoplasty: A Case Report

INTRODUCTION

Injection laryngoplasty using hyaluronic acid is a safe procedure commonly performed on patients with glottic insufficiency.

STUDY DESIGN

This is a descriptive study of a case of adverse reaction to hyaluronic acid in a patient who underwent injection laryngoplasty for the treatment of unilateral vocal cord paralysis.

DISCUSSION

The patient was treated with antibiotics and corticosteroids and had a full recovery. The authors recommend close observation following injection laryngoplasty using hyaluronic acid and diligent investigation of persistent postoperative laryngopharyngeal symptoms.

MERS versus Standard Surgical Approaches for Porcine Vocal Fold Scarring with Adipose Stem Cell Constructs

OBJECTIVE

Cells, scaffold, and surgical approaches are important for regeneration of the lamina propria of the scarred vocal fold (VF). Microendoscopy of Reinke's space (MERS) is a surgical approach used to access the lamina propria. The present study evaluated MERS in the treatment of VF scarring as compared with standardized approaches for the treatment of VF scarring with adipose stem cell constructs.

STUDY DESIGN

Animal study.

SETTING

Academic center.

SUBJECTS AND METHODS

VF injury was performed bilaterally to induce scarring in 20 pigs. Eight weeks after injury, pigs were classified into no treatment, minithyrotomy, VF injection, VF incision/dissection, and MERS. All groups (except control) were implanted with adipose stem cell and hyaluronan. Four weeks after treatment, histology for collagen, hyaluronan, and fibronectin; mRNA expression for α-smooth muscle actin, tumor growth factor β1, collagen 1α1, collagen 3α1, matrix metalloproteinase 2, basic fibroblast growth factor, and hepatocyte growth factor; and tissue rheology were evaluated.

RESULTS

Differences were measured among surgical approaches for protein levels of collagen, hyaluronan, and fibronectin (P = .0133, P < .0001, and P = .0025, respectively). Fibroblast growth factor, collagen 1α1, and matrix metalloproteinase 2 transcript levels were different among treatment groups (P = .003, P = .0086, and P = .014, respectively), while no differences were measured for α-smooth muscle actin, tumor growth factor β1, hepatocyte growth factor, and collagen 3α1. Rheologically, significant differences were not measured between groups.

CONCLUSION

MERS is a promising surgical approach for the treatment of VF scarring, optimizing the placement of implanted biomaterials.

Impact of patient-related factors on the outcomes of office-based injection laryngoplasty

OBJECTIVES/HYPOTHESIS

In-office percutaneous injection laryngoplasty (IL) is a common treatment for glottal insufficiency. The objective of this prospective study was to determine if voice outcomes from IL are affected by age, gender, or initial disease severity.

STUDY DESIGN

Prospective case series.

METHODS

Consecutive adult patients undergoing awake injection laryngoplasty were recruited from a subspecialty laryngology clinic. Voice Handicap Index (VHI-30); Consensus Auditory-Perceptual Evaluation of Voice (CAPE-V); and Grade, Roughness, Breathiness, Asthenia and Strain (GRBAS) Dysphonia Scale were evaluated prior to and 2 months after injection. Patients who had more severe disease were defined as those patients with greater initial perception of handicap, with a VHI score greater than 60.

RESULTS

Thirty-five subjects were enrolled, and 27 (16 male; mean age 61.6 ± 13.2 years) had complete data. No impact from age or gender was seen on outcomes from IL as measured by VHI-30 (P = 0.397 for age; P = 0.764 for gender), CAPE-V (P = 0.675 for age, P = 0.975 for gender), or GRBAS (P = 0.213 for age, P = 0.983 for gender). Patients with poorer initial VHI tended to have more significant improvement (P = 0.002), which may represent a ceiling effect.

CONCLUSIONS

In this prospective clinical study, age and gender did not affect outcome in IL. Patients with more severe disease appeared to have greater improvement.

LEVEL OF EVIDENCE

4. Laryngoscope, 126:1806-1809, 2016.

Glass ionomer application for vocal fold augmentation: Histopathological analysis on rabbit vocal fold

OBJECTIVES/HYPOTHESIS

The aim of this study was to investigate the use of glass ionomer cement (GIC) as an injection material for vocal fold augmentation and to evaluate the biocompatibility of the material.

STUDY DESIGN

Ten adult New Zealand rabbits were used.

METHODS

Under general anesthesia, 0.1-cc GIC was injected to one vocal fold and the augmentation of vocal fold was observed. No injection was applied to the opposite side, which was accepted as the control group. The animals were sacrificed after 3 months and the laryngeal specimens were histopathologically evaluated.

RESULTS

The injected and the noninjected control vocal folds were analyzed. The GIC particles were observed in histological sections on the injected side, and no foreign body giant cells, granulomatous inflammation, necrosis, or marked chronic inflammation were detected around the glass ionomer particles. Mild inflammatory reactions were noticed in only two specimens. The noninjected sides of vocal folds were completely normal.

CONCLUSION

The findings of this study suggest that GIC is biocompatible and may be further investigated as an alternative injection material for augmentation of the vocal fold. Further studies are required to examine the viscoelastic properties of GIC and the long-term effects in experimental studies.

LEVEL OF EVIDENCE

NA.

Using Hyaluronic Acid for Improving Vocal Function in a Prepubescent Boy With an Atrophied Right Vocal Fold

OBJECTIVES

A single case study is reported of a child who underwent several surgical procedures as result of congenital grade III subglottic stenosis. The anterior aspect of the right vocal cord was damaged and underwent atrophy during one of these procedures. Now, an active 10-year-old, the patient has become increasingly aware of his vocal limitations on functional activities. Injection of hyaluronic acid into the vocal folds has been known to provide improved voice quality in adults although there are no known cases reported of this procedure in children.

METHODS

This article reports voice outcomes after injection of hyaluronic acid into the Reinke's space in a single case study. Voice recordings were made before, after, and 1 month after injection. The voice recordings were subject to acoustic and perceptual analysis.

RESULTS

Post and follow-up voice recordings demonstrate decreased jitter, shimmer, and harmonics-to-noise ratio. Perceptual evaluation indicates improved voice quality.

CONCLUSION

Injection of hyaluronic acid in children who require voice augmentation is possible and may contribute to increased vocal function and improved voice outcomes.

Treatment Outcomes of Injection Laryngoplasty Using Cross-Linked Porcine Collagen and Hyaluronic Acid

Objective

To investigate the treatment outcomes and prognostic factors of injection laryngoplasty (IL) using cross-linked porcine collagen (PC) and hyaluronic acid (HA) in unilateral vocal fold paralysis (UVFP).

Study Design

Case series with chart review.

Setting

A tertiary teaching hospital.

Subjects and Methods

This study reviewed 60 consecutive patients with UVFP who underwent IL with PC (n = 33) or HA (n = 27). Objective evaluations included maximal phonation time (MPT) and 10-item voice handicap index (VHI-10). Kaplan-Meier method was applied to evaluate the subjective treatment outcomes according to the patients’ self-assessment of symptom recurrence via chart review for the follow-up period of 15 months. Log-rank tests were applied to evaluate the association between clinical factors and subjective treatment outcomes.

Results

Objective outcome measurements revealed significantly improved MPT and VHI-10 at 1, 3, and 6 months posttreatment, with nonsignificant differences between the PC and HA groups. Subjective treatment outcomes also revealed a nonsignificant difference between the 2 groups. The median symptom-free durations were 10.9 and 14.4 months for the PC and HA groups, respectively. Subsequent analyses failed to identify prognostic significance of sex, time to treatment, etiology, side, injection approaches, and the presence of aspiration. No significant adverse effects occurred during the follow-up period.

Conclusion

This study demonstrated comparable subjective and objective improvements following IL using PC or HA in patients with UVFP. No significant prognostic factor of IL was discovered in the present research. Porcine collagen and HA as medium duration materials might play a role in the future of IL.