Histologic studies on the fate of soluble collagen injected into canine vocal folds

Insights Into the Role of Collagen in Vocal Fold Health and Disease

As one of the key fibrous proteins in the extracellular matrix, collagen plays a significant role in the structural and biomechanical characteristics of the vocal fold. Anchored fibrils of collagen create secure structural regions within the vocal folds and are strong enough to sustain vibratory impact and stretch during phonation. This contributes tensile strength, density, and organization to the vocal folds and influences health and pathogenesis. This review offers a comprehensive summary for a current understanding of collagen within normal vocal fold tissues throughout the life span as well as vocal pathology and wound repair. Further, collagen's molecular structure and biosynthesis are discussed. Finally, collagen alterations in tissue injury and repair and the incorporation of collagen-based biomaterials as a method of treating voice disorders are reviewed.

Injection Laryngoplasty with Calcium Hydroxylapatite Gel Implant in an in Vivo Canine Model

The ideal injectable agent for vocal fold medialization is biocompatible, durable, sized to prevent phagocytosis and migration, and formulated for easy injection and does not adversely affect the viscoelastic properties of the vocal fold. We tested a cohesive implant of calcium hydroxylapatite (CaHA) particles in a gel carrier in an in vivo canine model of phonation. Six dogs underwent unilateral recurrent laryngeal nerve section and injection laryngoplasty of the paralyzed vocal fold with a CaHA implant. The six follow-up examinations were performed at 1,2, 3, 6, 9, and 12 months, and the larynx and bilateral neck lymphatic system were harvested for histologic analysis. The CaHA implant adequately medialized the vocal fold to regain glottal closure. The mucosal waves remained unaltered from baseline. The implant remained soft in the larynx and did not migrate to the neck lymphatic system. A localized foreign body giant cell reaction was present on histologic evaluation, but not acute or other chronic inflammation. A size analysis revealed no resorption of the CaHA particles. A decrease in medialization was noted at all follow-up intervals related to resorption of the aqueous-based gel carrier. The CaHA implant appears to be relatively safe and suitable for injection laryngoplasty.

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.

Self-organizing tissue-engineered constructs in collagen hydrogels

A novel self-organizing behavior of cellularized gels composed of collagen type 1 that may have utility for tissue engineering is described. Depending on the starting geometry of the tissue culture well, toroidal rings of cells or hollow spheroids were prompted to form autonomously when cells were seeded onto the top of gels and the gels released from attachment to the culture well 12 to 24 h after seeding. Cells within toroids assumed distinct patterns of alignment not seen in control gels in which cells had been mixed in. In control gels, cells formed complex three-dimensional arrangements and assumed relatively higher levels of heterogeneity in expression of the fibronectin splice variant ED-A--a marker of epithelial mesenchymal transformation. The tissue-like constructs resulting from this novel self-organizing behavior may have uses in wound healing and regenerative medicine, as well as building blocks for the iterative assembly of synthetic biological structures.

Results with collagen injection into the vocal folds for medialization

PURPOSE OF REVIEW

This review outlines the indications, surgical techniques and follow-up, with results, for current collagen use.

RECENT FINDINGS

Micronized AlloDerm (Cymetra) is a presently available injectable substance made from human collagen and elastin particles. A mean follow-up of 8-10.5 months showed lasting results after injection for vocal fold immobility. Collagen injection is one possible method for treating a vocal fold scar - or sulcus -vergeture by medialization of one or both of the scarred vocal folds. Collagen injection laryngoplasty is presently the treatment of choice for presbyphonia if speech therapy is insufficient. Collagen injection for Parkinson-related dysphonia is an effective temporary method of subjectively improving voice and speech in selected patients. Laryngeal collagen injection can also permit further medialization of one or both vocal folds after medialization thyroplasty.

SUMMARY

Injection laryngoplasty with micronized AlloDerm, a presently available homologous collagen, remains a suitable option for the treatment of vocal fold immobility with a moderate gap. Collagen injection is also efficient for sulcus vergetures, scars and presbyphonia, and can help in cases of Parkinson's disease. Complications are uncommon but patients must be advised that the stability of results is unpredictable. Collagen injection can be repeated and does not prevent other surgical solutions.

Injection laryngoplasty

After a nearly a century of development, augmentation of laryngeal tissue through injection remains as complex a procedure as it was in the earlier part of the century. Initially, the number of surgeons performing injection laryngoplasty was limited since the technique of injection was thought to be difficult and the selection of cases was thought to require the judgment of an accomplished laryngologist. Performing successful injection laryngoplasty does in fact require an understanding of laryngeal anatomy and physiology, and the physical characteristics of the substance to be injected. In addition, the surgeon must be aware of potential host reactions to the injected material. Finally, the surgeon must have an understanding of the etiology and configuration of the glottic insufficiency, and keep in mind the goals of the procedure.

Viscoelasticity of Rabbit Vocal Folds After Injection Augmentation

OBJECTIVES/HYPOTHESIS

Vocal fold function is related to the viscoelasticity of the vocal fold tissue. Augmentation substances used for injection treatment of voice insufficiency may alter the viscoelastic properties of vocal folds and their vibratory capacity. The objective was to compare the mechanical properties (viscoelasticity) of various injectable substances and the viscoelasticity of rabbit vocal folds, 6 months after injection with one of these substances.

STUDY DESIGN

Animal model.

METHODS

Cross-linked collagen (Zyplast), double cross-linked hyaluronan (hylan B gel), dextranomers in hyaluronan (DHIA), and polytetrafluoroethylene (Teflon) were injected into rabbit vocal folds. Six months after the injection, the animals were killed and the right- and left-side vocal folds were removed. Dynamic viscosity of the injected substances and the vocal folds was measured with a Bohlin parallel-plate rheometer during small-amplitude oscillation.

RESULTS

All injected vocal folds showed a decreasing dynamic viscosity with increasing frequency. Hylan B gel and DiHA showed the lowest dynamic viscosity values, and vocal folds injected with these substances also showed the lowest dynamic viscosity (similar to noninjected control samples). Teflon (and vocal folds injected with Teflon) showed the highest dynamic viscosity values, followed by the collagen samples.

CONCLUSION

Substances with low viscoelasticity alter the mechanical properties of the vocal fold to a lesser degree than substances with a high viscoelasticity. The data indicated that hylan B gel and DiHA render the most natural viscoelastic properties to the vocal folds. These substances seem to be appropriate for preserving or restoring the vibratory capacity of the vocal folds when glottal insufficiency is treated with augmentative injections.

The use of injectable collagen in the management of pediatric vocal unilateral fold paralysis

Vocal fold paralysis (VFP) is the second most common congenital abnormality that affects the larynx. Unilateral cases may be asymptomatic or feature symptoms related to laryngeal incompetence, such as aspiration and dysphonia. Management has traditionally been conservative as a high percentage of these paralyses recover spontaneously. The literature is scant on the acute or chronic management of unilateral vocal fold paralysis related symptoms in children. We present a series of four children (age 21 days, 5 years, 5 years, and 18 years) with unilateral VFP paralysis treated with collagen (Cymmtera) augmentation for control of symptoms related to laryngeal incompetence. Two children (age 21 days and 5 years) were managed in the acute setting. Follow-up has ranged from 4 to 12 months, and all have maintained excellent outcomes. Vocal fold augmentation with collagen is an effective therapeutic option in the management of symptoms related to unilateral VFP and laryngeal incompetence. It decreases the risk of aspiration and improves vocal quality. Collagen augmentation can be used in the acute setting to decrease aspiration, possibly avoiding a tracheotomy or gastrostomy tube placement, or to augment patients with a tracheotomy who are still severely aspirating.

Soft tissue response of the rabbit larynx to Gore-Tex implants

The use of Gore-Tex (expanded polytetrafluoroethylene) for medialization laryngoplasty has recently been described. Clinically, this laryngeal implant has performed well, but no animal studies evaluating the use of this implant in the larynx have been published. This study examines the gross and histologic response of the rabbit larynx to the Gore-Tex implant. Five rabbits underwent bilateral medialization with the Gore Thyroplasty Device. The vocal folds were left innervated and mobile. After 6 months, the rabbits were painlessly sacrificed and the implants were evaluated by gross inspection and histologic examination. No gross changes to the glottis occurred, and the implants were easily removed with gentle traction. A modest inflammatory response with a thin fibrous capsule was present around the implant. Foreign body giant cells were observed at the interface of the implant with the tissue. No migration or extrusion of the implant was observed. These results suggest that Gore-Tex is biocompatible in the rabbit larynx.

Comparison of microflap healing outcomes with traditional and microsuturing techniques: initial results in a canine model

A prospective, blinded study was designed to determine whether placement of a microsuture in epithelial defects created on canine vocal folds results in histologically demonstrable improved heating. Epithetial defects similar to those created during microflap removal were made by means of traditional microsurgical techniques on both vocal folds of 4 adult dogs. One vocal fold defect on each dog was then closed with a single microsuture placed through the laryngoscope. The larynges were harvested approximately 6 weeks later, and blinded histologic quantification of scar formation was performed. Microsutures resulted in less scarring in all but 1 of the larynges studied. Unsutured vocal folds exhibited a 75% larger average scar cross-sectional area. Although the sample size was insufficient to establish statistical significance, the observed difference in scar formation between microsutured and unsutured vocal folds suggests that primary closure with a microsuture in the canine model results in less scarring than when healing occurs by secondary intention.

Histological study of injected autologous fascia in the paralyzed canine vocal fold

OBJECTIVE

Several methods have been used for the treatment of the unilateral paralyzed vocal fold. Teflon injections have been used extensively but not without complications. The ideal substance for injection is yet to be determined. Injected autologous fascia has been reported as a means of achieving glottic closure. In review of the literature, there are no long-term results described using autologous fascia in this way. The purpose of this study was to examine the histological changes of the larynx after injection of autologous fascia into a paralyzed vocal fold.

STUDY DESIGN

A prospective study with the contralateral side of the larynx used as the control.

METHODS

Six adult dogs underwent severing of one of their recurrent laryngeal nerves. After the vocal folds were confirmed to be paralyzed by direct laryngoscopy, fascia lata that was harvested from the animal was minced and injected into the paralyzed vocal fold. The dogs were then killed at intervals ranging from 3 to 12 months and their larynges reviewed histologically.

RESULTS

The larynges revealed muscle atrophy of the vocal fold, which is consistent with denervation, but there was no evidence of persistent fascia. In addition, there was no evidence of reaction to the injected fascia. Special stains for collagen were also performed which showed no significant change from the non-injected vocal fold.

CONCLUSION

From this model, it is concluded that injected autologous minced fascia is not a good short- or long-term substance for vocal fold augmentation. Further study is warranted to confirm this observation.

Phonosurgical vocal fold injection: procedures and materials

Significant advances have recently occurred in the area of vocal fold injection. Phonosurgical vocal fold injection is now a precise set of techniques used to improve voice quality through vocal fold injection. Lipoinjection and collagen injection are discussed in detail. The different vocal fold injection techniques and materials are discussed in this article.

Microsurgery of sulcus vergeture with carbon dioxide laser and injectable collagen

Between January 1989 and June 1998, we operated on 45 patients for sulcus vergeture. The studied population encompassed 38 women (84%) and 7 men (16%). The median age was 36 (range 12 to 71 years). The surgical technique is based on a concept of Cornut and Bouchayer according to which the dissection of the epithelium adherent to the deep subepithelial plane improves the vocal fold vibration. Dissection is performed with a single-pulsed carbon dioxide laser at 2 to 3 W with a pulse duration of 0.1 second. We use the Super-pulse microwave. The Acuspot micromanipulator provides a spot size of 250 microm at 350-mm focal length. When the vocal fold is atrophic, surgery is completed with a bovine or autologous collagen injection; the median injected quantity is 0.3 mL (range 0.1 to 0.4 mL). The epithelial microflap is redraped with fibrin glue. Voice therapy is indispensable for correcting the associated hyperkinetic dysphonia. The median postoperative follow-up period is 5 months (range 1 to 18 months). In terms of median values, the maximum phonation time improved from 9 to 13 seconds, the phonation quotient improved from 296.5 to 228.5 mL/s, and the spectral analysis distribution improved by 1 class. Stroboscopic examination reveals an improvement of the vibratory symmetry, amplitude, and wave. Subjectively, the patients describe an improved ability for vocal effort and the regression or disappearance of vocal fatigue. Although the timbre is improved, the voice often remains breathy and hoarse.

Correcting vocal fold immobility by autologous collagen injection for voice rehabilitation. A short-term study

We report on a short-term clinical study of injectable autologous collagen (Vocalogen) used to correct dysphonias arising from vocal fold immobility. The collagen is extracted from skin taken from the lower abdominal quadrant area or from just above the bikini line. About 30 cm2 of skin are required to provide 2 mL of injectable collagen. The histologic examination of the preparation before injection disclosed the presence of elastin fibers and some clusters of epithelial cells, beside the collagen fibers. The collagen is naturally reticulated, and the molecule is preserved in its entirety. The technique is exactly the same as that reported for bovine collagen: injection into Reinke's space, under general anesthesia, monitored by direct microlaryngoscopy. The amount injected is also similar: 1.5 mL for correction of glottic insufficiency in which the immobile vocal fold is in the intermediate position. Eight patients were injected, and the average follow-up was 4.5 months. Voice assessments made before and after the treatment included stroboscopy, subjective and perceptual judgments, and aerodynamic and acoustic measurements. The functional results were similar to those obtained with bovine collagen. No complications arose. The probability of any hypersensitivity reaction, always a possibility to be feared with bovine collagen, is negligible with the autologous collagen. Long-term results are as yet unknown, but from the fact that the collagen molecular structure is intact and there is little risk of foreign body response, it would be expected that autologous preparations would be more stable than bovine collagen; this appears to be the case in cosmetic applications. Autologous collagen could be employed for the same indications as bovine collagen, provided that a delay of 45 days (the time required to prepare the injectable collagen) is acceptable. The amount of collagen required is also a limiting factor, since the patient's own skin is the starting donor material.

Transurethral collagen injection for female stress incontinence

Periurethral collagen injections have been used to treat female urinary incontinence secondary to intrinsic sphincteric deficiency (ISD). As an alternative, a transurethral submucosal collagen injection was used in 33 consecutive women suffering from stress incontinence secondary to ISD at Tulane University Medical Center. Prior to the procedure, careful clinical examination with a videofluorourodynamic study was performed for each case. The procedure was carried out under local anesthesia assisted with monitored anesthesia care (MAC). The collagen was injected transurethrally by the long collagen needle (C. R. Bard). In the first 11 cases the average cumulative collagen injected per patient was 6.1 ml, whereas in the last 22 cases the average was 3.5 ml. As a result of the injection 16 patients were dry (48.5%) and 11 were improved (33.3%), with an overall success rate of 81.8%. The injection failed in 6 patients (18.1%). The mean follow-up was 18.8 months, with a range of 2-33 months. In the successful group there was a significant decrease in pretreatment frequency, from an average of 8 to 4.9 (P = 0.005) and in nocturia from an average of 2.14 to 0.76 (P = 0.001). Also, there was a significant decrease in the number of pads, from an average of 3.7 to 1.1 (P = 0.001). The stress leak-point pressure showed a significant increase, from an average of 68.1 to 93.5 cm H2O (P = 0.03). There was no relation between grade of incontinence and the success of the injection. Two cases suffered from temporary urinary retention. This study revealed that the transurethral submucosal collagen injection is an effective method for treating cases of intrinsic sphincteric deficiency. The volume of collagen required to produce the seal effect is small and it may decrease the reinjection rate. As experience is gained, the procedure time is typically 15 minutes. This makes it a reliable, cost-effective and well-controlled method. However, it has a learning curve and the cystoscope instruments require minor adaptation for its use.

Collagen injection for intrinsic sphincteric deficiency in men: a reasonable option in selected patients

PURPOSE

We evaluate transurethral collagen injection as a minimally invasive option in treating stress urinary incontinence in men and identify the prognostic factors for success or failure.

MATERIALS AND METHODS

Transurethral collagen was injected in 35 men with grades III (22) and II (13) incontinence.

RESULTS

Of the patients 7 became dry (20%), 11 improved (31.4%) and 17 were considered failures (48.6%). Abdominal leak point pressure increased and the number of pads needed decreased. In the failed group 4 patients had a history of pelvic irradiation, 5 urethral stricture disease and 3 bladder instability before injection. There was 1 case of temporary urinary retention as a complication.

CONCLUSIONS

Transurethral collagen injection for male stress urinary incontinence is a reasonable option in select patients.

The histologic fate of autologous collagen injected into the canine vocal fold

Collagen is a functionally essential component of the five-layered structure of the vocal fold. Soluble bovine collagen has previously been shown to be an effective injectable bioimplant for vocal fold defects, paralysis, and, especially, scarred larynges. Although bovine collagen appears to be well tolerated, the concern for possible adverse immunologic responses has deterred approval from the Food and Drug Administration for its clinical use in the larynx. Currently we are investigating the use of injectable autologous collagen for vocal fold augmentation. The purpose of this study is to examine the histologic fate of autologous collagen injected into the canine vocal fold at multiple intervals after injection. An ellipse of skin measuring 3 x 6 cm was harvested from each of three dogs and processed into a naturally cross-linked injectable solution of collagen (Autologen). This autologous collagen was injected into one vocal fold and a control injection of buffer solution was injected contralaterally. The injections were well tolerated and no dog appeared to suffer any immediate or delayed ill effects. The dog larynges were harvested 1, 3, and 6 months after collagen injection and examined grossly and histologically. Injected autologous collagen material persisted in these experimental animals and appeared to be well tolerated. Based on this preliminary study, we anticipate autologous collagen to be at least as suitable as bovine chemically cross-linked collagen as an injectable bioimplant for vocal fold augmentation. It may also have the advantage of added safety and stability.

Lipoinjection in the Paralyzed Feline Vocal Fold: Study of Graft Survival

Six adult domestic strain cats were used to study the long-term histologic outcome of injected autologous fat for augmentation of the paralyzed vocal fold. Each animal had surgically induced left vocal cord paralysis via sectioning of the recurrent laryngeal nerve, followed by injection of 0.1 to 0.2 ml of autologous fat into the paralyzed vocal fold. The animals were killed at 6 weeks, and at 4, 6, 8, and 12 months after the injection. Photographic and videolaryngoscopic data were obtained. Histologic studies of the larynges were performed. The results documented histologic viability and persistence of a portion of the injected adipose tissue graft at 8 months after the injection, but only minimal graft survival at 12 months. The outcome suggests that autologous lipoinjection has potential use for short-term (several months) augmentation of the paralyzed vocal cord. Further investigation is warranted before recommending this technique for such use or as an alternative to currently available long-term injectable laryngeal biomaterials.

MRI evaluation of vocal fold paralysis before and after type I thyroplasty

Magnetic resonance imaging (MRI) is a useful modality for three-dimensional evaluation of laryngeal anatomy. The authors present data on patients with unilateral vocal fold paralysis both before and after type I thyroplasty for medialization. Videoendoscopic and acoustic measures were obtained. MRI was performed preoperatively and postoperatively. Three-dimensional descriptive parameters were established to assess implant location. As well, vocal and endoscopic assessment were used to determine a successful result. Magnetic resonance images of two patients with satisfactory results were compared with images and vocal analysis of two dissatisfied patients. Use of MRI after type I thyroplasty provides additional information about implant location that can help determine the cause of poor results.

Vocal fold scarring: current concepts and management

Scarring of the vocal folds can occur as the result of blunt laryngeal trauma or, more commonly, as the result of surgical, iatrogenic injury after excision or removal of vocal fold lesions. The scarring results in replacement of healthy tissue by fibrous tissue and can irrevocably alter vocal fold function and lead to a decreased or absent vocal fold mucosal wave. The assessment and treatment of persistent dysphonia in patients with vocal fold scarring presents both diagnostic and therapeutic challenges to the voice treatment team. The common causes of vocal fold scarring are described, and prevention of vocal fold injury during removal of vocal fold lesions is stressed. The anatomic and histologic basis for the subsequent alterations in voice production and contemporary modalities for clinical and objective assessment will be discussed. Treatment options will be reviewed, including nonsurgical treatment and voice therapy, collagen injection, fat augmentation, endoscopic laryngoplasty, and Silastic medialization.

Unilateral vocal fold paralysis: a review of the current methods of surgical rehabilitation

This review article discusses the surgical treatment of patients suffering from unilateral vocal fold paralysis who have already been assessed and considered appropriate candidates for surgery. There are currently three main methods of surgical rehabilitation; injection medialisation; laryngeal framework surgery; re-innervation procedures.

Autologous collagen vocal fold injection: a preliminary clinical study

This preliminary study reports the first use of injectable autologous collagen for vocal fold augmentation. In previous studies, the authors showed cross-linked bovine collagen to be effective in more than 150 patients with glottic incompetence, particularly those with focal defects or scarred or atrophic vocal folds. However, concerns about possible adverse immunologic responses to the bovine material have limited its use. The authors studied eight patients with difficult vocal fold pathology, including sulcus vocalis, atrophy, and scarring secondary to trauma and cordectomy. Skin was harvested under local anesthesia, processed into a naturally cross-linked injectable form (Autologen), and injected using indirect laryngoscopy. Voice production was evaluated prior to the injection and at intervals after the injection, using subjective, perceptual, aerodynamic, acoustic, and videostroboscopic assessments. The results indicate that autologous collagen is comparable to injectable bovine collagen in the management of several difficult glottic insufficiency problems and that the likelihood of a hypersensitivity response is negligible. Unlike bovine collagen preparations, Autologen does not require breakdown of the natural collagen molecule, so it is anticipated that this material will be better tolerated and more stable over time.

Endoscopic microsuture repair of vocal fold defects

The presence of a nonvibratory segment of vocal folds after microlaryngeal surgery is often a cause of poor voice result. The etiology of a nonvibratory segment is due to full thickness epithelial defect followed by secondary wound closure and scar contracture. To reduce scar contracture and nonvibratory segment of the vocal folds, primary repair with a 6-0 chromic endo-knot suture technique was used to close defects and approximate microflaps of the vocal folds. This was done in 18 patients with epithelial defects after resection of benign vocal fold lesions. The pathologic findings included severe polypoid degeneration (n = 7), fusiform laryngeal polyps (n = 5), sulcus vocalis (n = 2), cyst (n = 2), and keratosis (n = 2). Voice was improved in all patients after surgery. Comparison of vocal fold vibration before and after surgery showed improvements in configuration, amplitude, and mucosal wave. Vocal folds that were sutured all had good vibratory characteristics; none had a nonvibrating segment at the site of suture placement. Voice and healing after microsuture technique were near normal by Day 10 and return of mucosal wave was often complete by Day 14. Endoscopic microsuture closure of microflaps of the vocal folds edge is safe and affords the surgeon an opportunity for primary repair with improved functional result.

Treatment of vocal fold immobility by glutaraldehyde-cross-linked collagen injection: long-term results

Fifty-three cases of unilateral vocal fold immobility treated by glutaraldehyde-cross-linked (GAX) collagen over a 6-year period with a mean follow-up of 4.5 years were reviewed for assessment of the immediate and long-term effects on phonation. The mean amount injected was 1.47 mL. No long-term local or systemic reaction to the collagen was seen. The median preoperative maximum phonation time (MPT) was 7.5 seconds, the median immediate postoperative MPT 12 seconds, and the median long-term postoperative MPT 11 seconds. The median preoperative phonatory quotient (PQ) was 564 mL/s. The median immediate postoperative PQ was 320 mL/s, whereas the median long-term postoperative PQ was 385 mL/s. The quantitative improvement in the voice as measured by the PQ was thus 67% for the short range and 49% for the long range. The decline in the results over time was 20.3%. Vocal frequency analysis showed that the fundamental frequency and harmonics returned and were maintained in the long term for more than 80% of the patients with the help of speech therapy. This relative stability is explained by the findings of previous histological work. The fact that collagen, unlike Teflon, does not cause an inflammatory reaction and the partial maintenance of the improvement achieved, which is to be compared with the instability of the effects produced by resorbable substances, make it the "least objectionable" injectable for the treatment of unilateral glottic fold immobility. One must overcompensate 20% to 30%, given the results of the long-term stability studies.

Early experience with intraurethral collagen injections for urinary incontinence

We report on 41 patients (10 men and 31 women) who underwent collagen injections for urethral incompetence. Mean followup was 6 months (range 3 to 11 months) in men cured or improved, 8.4 months (range 3 to 15 months) in women who were cured and 4.5 months (range 2 to 10 months) in women who were improved. In women the procedure was usually performed through a periurethral approach while they were under local anesthesia and in men it was performed transurethrally while under either general or local anesthesia. Of the 31 women 28 (90.3%) were cured (15) or improved (13). Mean maximum Valsalva pressure increased from 31 cm. water before injection to 85 cm. water at 6 months after injection in women who were cured or improved. The mean amount of collagen used in the female group was 12.7 cc (range 2.5 to 47.5) and the mean number of treatments was 2 (range 1 to 7). Of the men 7 (70%) had successful results (2 cured and 5 improved). In contrast to the women, they required a mean of 51.8 cc (range 7.5 to 82.5) of collagen and a mean of 6 treatments (range 3 to 12). Of 5 patients with bladder instability 4 did not improve. One patient suffered acute bacterial prostatitis and 2 patients had post-injection urinary retention. All women with little or no bladder neck hypermobility (types 1 and 3) were either cured or improved. We conclude that intraurethral collagen injection is safe and simple to perform. The results achieved in women are acceptable. In men, while collagen does provide improvement, the cost-to-benefit ratio and effectiveness are less than those in women. Instability may obviate a good outcome.

Role of injectable collagen in the treatment of glottic insufficiency: a study of 119 patients

Injectable bovine collagen has been used for treatment of glottic insufficiency at the University of Wisconsin Clinical Science Center since 1983. This report reviews our experience in treating 119 patients with a variety of vocal fold disorders manifested by glottic insufficiency. Many of the patients were referred because of prior treatment failures or problems that were impossible to treat with other modalities. Results were assessed by comprehensive voice evaluations using subjective patient self-assessments, perceptual judgments made by a panel of experts who had no prior knowledge of the study, objective assessments, and videostroboscopy. Objective assessment included vocal function measures and acoustic analysis. Results indicate that collagen not only is comparable to other injection filler substances but also has unique advantages as a bioimplant. Collagen injection seems uniquely suited for treatment of several problems, including vocal fold atrophy, focal defects, minimal glottic insufficiency, and scarred vocal folds that are not managed optimally with Teflon injection. Overall there were no serious complications and treatment was effective for a broad spectrum of problems. In most instances the correction persisted, and in those instances in which injected collagen seemed improperly distributed, the vocal fold was recontoured or the implant removed without appreciable damage to the surrounding tissues. Injectable collagen has been extensively studied and deserves to be included in the armamentarium of the laryngeal surgeon.

Further morphologic studies on collagen injected into canine vocal folds

We compared the morphologic fate of three types of soluble bovine collagen injected into vocal folds of dogs: 1) Zyderm collagen implant containing 35 mg/mL of collagen (ZCI I), 2) Zyderm collagen implant containing 65 mg/mL of collagen (ZCI II), and 3) GAX collagen containing 35 mg/mL of collagen minimally cross-linked with 0.0075% glutaraldehyde. Light and electron microscopy showed good host tolerance and a long-term persistence of the three types of collagen at the site of injection. The collagen implants were progressively colonized by fibroblasts and capillaries accompanied by host collagen deposition. No inflammatory process or foreign body reaction occurred, in contrast to the typical host reaction to injected Teflon. The colonization of GAX collagen was slower than for ZCI I and ZCI II. No other significant difference was evident among the three types of injectable collagen. All three appear to be very suitable materials for laryngeal implants; moreover, they seem to best meet accepted requirements for a good implant: they are easy to inject, they are well tolerated, and they persist for a long time. We prefer GAX collagen for clinical use because of its lower reactivity and higher stability, and because overinjection is not necessary (GAX shrinks less than ZCI I and ZCI II).

Histological study of atelocollagen infused into the human vocal cords

There have been only three case reports of histological study on injection of atelocollagen into the human vocal cords, and none of these have indicated foreign body reaction. We histologically examined the larynx of a 70-year-old man, which had to be excised 44 days after infusion of atelocollagen into the vocal cords. The atelocollagen infused was found to have been replaced with the collagen of host cells, but no foreign body reaction was observed. As in conventional reports, the histoaffinity of atelocollagen was confirmed.

Correction of glottic insufficiency by collagen injection

Thirty-nine patients were treated with GAX collagen for vocal fold augmentation. The objective results were evaluated by measurement of the maximum phonation time, the phonatory quotient, vocal frequency analysis, and laryngostroboscopy. These results are as good as those with Zyderm Collagen II (ZCI). Avoidance of useless overcorrection, better resistance to collagenase, and less induced hypersensitivity differentiate GAX from ZCI.