The purpose of this study was to compare the clinical effectiveness of type I thyroplasty, injection laryngoplasty and graft implantation for the treatment of vocal fold scar and pathologic sulcus vocalis, using a prospective, quasi-experimental research design. To our knowledge, this study represents the first multi-arm treatment comparison for these disorders in the clinical literature. No single treatment modality demonstrated clear superiority across the majority of vocal function indices used. Type I thyroplasty and graft implantation both resulted in improved VHI with no concomitant improvement in auditory-perceptual, acoustic, aerodynamic or vocal fold physiologic performance. Injection laryngoplasty resulted in no improvement on any vocal function index. Patients who underwent graft implantation exhibited the slowest trajectory of improvement across the 18 month follow-up period.
Type I thyroplasty resulted in improved mean and best post-treatment VHI total scores, whereas graft implementation resulted in improved best post-treatment score only. This discrepancy was most likely due to the relatively slow trajectory of improvement in the graft group, leading to significantly improved VHI scores at a smaller number of (later occurring) post-operative timepoints, and a relatively smaller magnitude change in mean outcome. Given that VHI outcome at 18 months post-treatment was equivalent, but recovery trajectory was slower, our data do not support graft implantation over type I thyroplasty as a primary treatment modality for patients with vocal fold scar/sulcus. A prolonged and gradual recovery period is well documented following graft implantation to the lamina propria;25,29,30,32
as such, it is possible that a number of patients in the graft group experienced meaningful improvement beyond 18 months post-treatment. If so, there may be therapeutic value with this approach that was not captured in our dataset.
Discordance between the VHI and other vocal fold function measures, as seen in our dataset, has been reported in a number of studies. Cheng & Woo50
identified significant improvement in VHI total score following surgical removal of benign vocal fold lesions in 21 patients, but no change in 12 out of 13 acoustic and aerodynamic parameters. The majority of these instrumental parameters did not correlate with the VHI. Lau et al.51
compared VHI total score and various videostroboscopic parameters in 28 patients before and after injection laryngoplasty for unilateral vocal fold paralysis. VHI total score exhibited a moderately strong correlation with closed phase duration and weak correlations with all other parameters. These findings align with the majority of descriptive (non-treatment) studies that have reported weak to moderately strong correlations between the VHI and commonly used acoustic and aerodynamic measures.52-55
It is intuitive that individuals with dysphonia have varying personalities, personal circumstances, social and occupational demands, and consequently perceive different degrees of voice-related handicap; because of this, it has been suggested there is a nonlinear relationship between voice impairment, disability and handicap.54
Overall, the VHI captures a unique aspect of voice-related psychosocial function that is independent of (and complementary to) acoustic, aerodynamic and physiologic voice function. In one sense, improved voice handicap represents one of the most meaningful aspects of treatment-induced change.
Our study design and implementation hold several limitations. First, we did not randomize patients to the three treatment groups. This allowed the laryngologist to assign patients to the presumed most-appropriate treatment based on presentation, therefore reflecting standard clinical practice; nevertheless, our findings do not carry the weight of a randomized clinical trial. Second, we did not control for implant or injectate material, but rather focused exclusively on treatment modality. This may represent a source of intra-treatment variability in the dataset. Third, we administered routine perioperative voice therapy to all patients, which again reflects standard of care but also may have influenced treatment outcome. Fourth, our recruitment success and associated sample size were limited by the decision to exclude patients who had undergone prior surgical or behavioral intervention. Due to our sample size, we were unable to delineate and categorize patient subgroups based on potentially important variables such as scar/sulcus location, unilateral versus bilateral pathology, pathologic sulcus subtype, and the presence of aggravating factors and other comorbidities. This degree of patient hetereogeneity, inherent to almost any clinical scar/sulcus study, represents another source of variability. Future research efforts in this area may benefit from multi-institutional recruitment, in addition to patient randomization and (although controversial) consideration of a placebo control (i.e., sham surgery) condition. Additional experimental precautions, such as single- or double-blinding of treatment group assignment, are difficult to implement, as in-office injection laryngoplasty does not require general anesthesia, and patients/researchers can easily identify the incision sites used for thyroplasty window creation and autologous fat/fascia harvest.
We focused on three singular treatment modalities in this study, primarily due to their prominence and reported value in the clinical literature. Consequently, it is unknown how type I thyroplasty, injection laryngoplasty and graft implantation outcomes compare to other proposed approaches such as mucosal slicing,24
pulsed dye laser irradiation,38
and superficial injection/implantation of hyaluronic acid-based biomaterials36,37
or autologous fat.27,28,33,34
Further, we did not include combinative treatments, such as CO2
laser excision followed by collagen injection,19,20
fascia implantation followed by fat injection,32
or gelatin sponge implantation followed by fat injection;26
each of which holds the conceptual appeal of simultaneously or sequentially tackling glottal incompetence and lamina propria issues, with possibly compounded benefit. Finally, a number of emerging therapies involving growth factors,56-60
phytochemical and pharmacological agents,61,62
and various cell types71-79
await future clinical translation. Appropriate evaluation of these treatment strategies requires careful investigation in appropriately powered clinical trials.