Modeling and simulation of material degradation in biodegradable wound closure devices.

Biodegradable materials have been used as wound closure materials. It is important for these materials to enhance wound healing when the wound is vulnerable, and maintain wound closure until the wound is heal. This article studies the degradation process of bioresorbable magnesium micro-clips for wound closure in voice/laryngeal microsurgery. A novel computational approach is proposed to model degradation of the biodegradable micro-clips. The degradation process that considers both material and geometry of the device as well as its deployment is modeled as an energy minimization problem that is iteratively solved using active contour and incremental finite element methods. Strain energy of the micro-clip during degradation is calculated with the stretching and bending functions in the active contour formulation. The degradation rate is computed from strain energy using a transformation formulation. By relating strain energy to material degradation, the degradation rates and geometries of the micro-clip during degradation can be represented using a simulated degradation map. Computer simulation of the degradation of the micro-clip presented in the study is validated by in vivo and in vitro experiments.

New device for single-stage in-office secondary tracheoesophageal puncture: animal studies.

BACKGROUND: A new device is described for secondary tracheoesophageal puncture (TEP). We hypothesize that the device can be used to create the puncture, size, and insert the voice prosthesis in antegrade fashion in a single procedure suitable for office-based use. METHODS: A measurement and insertion device (MAID) was designed with the hypothesis in mind and tested on 3 pigs while they were under general anesthesia. RESULTS: The procedure was easy and successful in all 3 animals. The MAID allowed measurement of tracheoesophageal wall thickness and antegrade insertion of voice prosthesis with a single device. Transnasal esophagoscopy (TNE) allowed visualization of markings on the MAID within the esophagus to facilitate sizing. Intraesophageal visualization using TNE also enabled accurate positioning, reduced risk of posterior esophageal wall injury, and practically eliminated false passage formation. CONCLUSION: We believe the MAID can facilitate single-stage office-based secondary TEP in postlaryngectomy patients.

Development of a microclip for laryngeal microsurgery: initial animal studies.

OBJECTIVES/HYPOTHESIS: Mucosal closure following laryngeal microsurgery can be challenging due to limited access, and incisions are often left to heal without formal closure. This study explores the hypothesis that a bioabsorbable microclip can be developed as an alternative method to close mucosal incisions in laryngeal microsurgery. STUDY DESIGN: Animal study. METHODS: In vitro studies were performed to determine if a suitable clip could be designed using bioabsorbable materials. A porcine model was used to study behavior of the clip in vivo. RESULTS: We initially studied poly-ϵ-caprolactone but encountered difficulty creating a small clip with the necessary material strength. Using magnesium we were able to produce a clip sufficiently small to close vocal fold incisions. Magnesium is biocompatible, bioabsorbable, and malleable, and has been used to manufacture vascular stents and sutures. The magnesium microclip could be deployed rapidly using modified 2-mm micro-laryngeal cup forceps, which enable the clip to close in a circular shape. In vitro and in vivo tests showed the clip held securely to the vocal fold mucosa. Macroscopic and histologic studies showed no significant injury to the contralateral vocal fold. There was no evidence of lower airway injury after implanting clips into the lower airway. CONCLUSIONS: The bioabsorbable clip could be used to close selected incisions in laryngeal microsurgery. Currently we are working to further reduce the size of the clip and modify its bioabsorption properties to enable precise control of degradation.

Diagnosis of early stage nasopharyngeal carcinoma using ultraviolet autofluorescence excitation-emission matrix spectroscopy and parallel factor analysis.

We report the diagnostic ability of ultraviolet (UV)-excited autofluorescence (AF) excitation-emission matrix (EEM) spectroscopy associated with parallel factor (PARAFAC) analysis for differentiating cancer from normal nasopharyngeal tissue. A bifurcated fiber-optic probe coupled with an EEM system was used to acquire tissue AF EEMs using excitation wavelengths between 260 and 400 nm, and emission collection between 280 and 500 nm. A total of 152 AF EEM landscapes were acquired from 13 normal and 16 nasopharyngeal carcinoma (NPC) thawed ex vivo tissue samples from 23 patients. PARAFAC was introduced for curve resolution of individual AF EEM landscapes associated with the endogenous tissue constituents. The significant factors were further fed to a support vector machine (SVM) and cross-validated to construct diagnostic algorithms. Both the EEM intensity landscapes and the PARAFAC model revealed tryptophan, collagen, and elastin to be the three major endogenous fluorophores responsible for the AF signal from normal and NPC tissues. The EEM intensity distribution and PARAFAC factors suggest an increase of tryptophan and a decrease of collagen and elastin in NPC tissues compared to the normal. The classification results obtained from the PARAFAC-SVM modeling yielded a diagnostic accuracy of 94.7% (sensitivity of 95.0% (76/80); specificity of 94.4% (68/72)) for normal and NPC tissue differentiation. This study suggests that UV-excited AF EEM spectroscopy integrated with PARAFAC algorithms has the potential to provide clinical diagnostics of early onset and progression of NPC.

Injection laryngoplasty with hyaluronic acid for unilateral vocal cord paralysis. Randomized controlled trial comparing two different particle sizes.

The objective was to determine if particle size affects durability of medialization in patients undergoing injection laryngoplasty (IL) with hyaluronic acid (HA) for unilateral vocal cord paralysis (UVCP). We hypothesized that large particle-size HA (LPHA) persists longer after injection to produce a more durable vocal result. The study design used was a prospective randomized controlled single-blind trial. Patients underwent IL with Restylane (small particle-size HA, SPHA) or Perlane (LPHA) (Q-Med AB, Uppsala, Sweden). Injections were performed transcutaneously in the outpatient clinic. The Voice Handicap Index (VHI) at 6 months postinjection was the primary outcome measure. Secondary outcomes included videostroboscopic findings, and objective acoustic and aerodynamic measures. Seventeen patients (eight SPHA, nine LPHA) were available for follow-up at 6 months. Normalized VHI scores at 6 months after IL were significantly lower in the LPHA group compared to the SPHA group when not adjusted for age and sex (P=0.027). After adjustment, the difference was not significant (P=0.053) but the LPHA group trended toward lower normalized VHI scores. The findings support the hypothesis that the larger particle-size of LPHA makes this material more durable than SPHA for IL. This material may be considered for temporary medialization in patients with UVCP in whom medium-term improvement of at least 6 months is desirable. The transcutaneous route can be used safely in the office setting in non-anticoagulated patients.

Spectroscopic diagnosis of laryngeal carcinoma using near-infrared Raman spectroscopy and random recursive partitioning ensemble techniques.

In this work, we evaluated the diagnostic ability of near-infrared (NIR) Raman spectroscopy associated with the ensemble recursive partitioning algorithm based on random forests for identifying cancer from normal tissue in the larynx. A rapid-acquisition NIR Raman system was utilized for tissue Raman measurements at 785 nm excitation, and 50 human laryngeal tissue specimens (20 normal; 30 malignant tumors) were used for NIR Raman studies. The random forests method was introduced to develop effective diagnostic algorithms for classification of Raman spectra of different laryngeal tissues. High-quality Raman spectra in the range of 800-1800 cm(-1) can be acquired from laryngeal tissue within 5 seconds. Raman spectra differed significantly between normal and malignant laryngeal tissues. Classification results obtained from the random forests algorithm on tissue Raman spectra yielded a diagnostic sensitivity of 88.0% and specificity of 91.4% for laryngeal malignancy identification. The random forests technique also provided variables importance that facilitates correlation of significant Raman spectral features with cancer transformation. This study shows that NIR Raman spectroscopy in conjunction with random forests algorithm has a great potential for the rapid diagnosis and detection of malignant tumors in the larynx.

Raman spectroscopy for optical diagnosis in the larynx: preliminary findings.

BACKGROUND AND OBJECTIVES: Raman spectroscopy (RS) provides information about molecular structure and is a potential tool for non-invasive tissue diagnosis. To determine if Raman spectra could be obtained rapidly from laryngeal tissue in vitro, and compare Raman spectra from normal, benign, and cancerous laryngeal tissue. STUDY DESIGN/MATERIALS AND METHODS: Forty-seven laryngeal specimens were studied using RS with signal acquisition times (SAT) between 1 and 30 second(s). Multivariate analysis was used to determine the diagnostic ability of RS compared to standard histology (n = 18, 13, and 16 respectively for normal tissue, carcinoma, and squamous papilloma). RESULTS: Good quality spectra were obtained with 5-second SAT. Spectral peak analysis showed prediction sensitivities of 89%, 69%, and 88%, and specificities of 86%, 94%, and 94% for normal tissue, carcinoma, and papilloma. CONCLUSIONS: In the larynx, spectral differences appear to exist between normal tissue, carcinoma, and papilloma. The ability to obtain spectra rapidly supports potential for future in vivo studies.

Selective denervation: reinnervation for the control of adductor spasmodic dysphonia.

OBJECTIVES: The objective of this study was to evaluate the efficacy of a new surgical procedure for adductor spasmodic dysphonia (AddSD). This surgery involves the bilateral selective division of the adductor branches of the recurrent laryngeal nerves with immediate reinnervation of the distal nerve trunks with branches of the ansa cervicalis (selective denervation-reinnervation). METHODS: Our first six patients to undergo this procedure were enrolled in the study. All patients suffered from AddSD and had previously received botulinum toxin A (Botox, Allergen, Markham, ON) therapy. Patients were recorded preoperatively and all underwent the same surgical procedure performed by the same lead surgeon. All patients were surveyed postoperatively and then re-recorded. Expert and untrained judges undertook perceptual evaluation of voice quality. Voice samples were also objectively evaluated for aphonic voice breaks. RESULTS: No major surgical complications were noted. Patient satisfaction was excellent, and five of the six patients no longer require botulinum toxin therapy. In five of the six patients, the majority of untrained and expert listeners perceived the postoperative voice to be superior. Objectively, the rate of aphonic voice breaks was also reduced in five of the six patients.

Vocal fold paralysis following radiotherapy for nasopharyngeal carcinoma: laryngeal electromyography findings.

Laryngeal electromyography was used to study the pattern of neurological injury in three patients with unilateral vocal fold paralysis following radiotherapy for nasopharyngeal carcinoma. The thyroarytenoid and cricothyroid muscles were assessed to give an indication of recurrent and superior laryngeal nerve function. Two patients demonstrated both recurrent and superior laryngeal neuropathy suggesting injury at the skull base. The other patient had only recurrent laryngeal neuropathy indicating more distal involvement. Subclinical neuropathic changes were seen in two cases on the side contralateral to the vocal fold paralysis. These patients may be at increased risk of developing bilateral vocal fold paralysis and potentially life-threatening airway obstruction. Long-term follow-up is recommended for such patients, especially if medialization thyroplasty is being considered. This is the first report describing the use of electromyography to determine the pattern of nerve injury in patients with vocal fold paralysis following head and neck radiotherapy.

Raman spectroscopy for optical diagnosis in normal and cancerous tissue of the nasopharynx-preliminary findings.

BACKGROUND AND OBJECTIVES: Raman spectroscopy (RS), which can detect molecular changes associated with cancer, was explored as a means of distinguishing normal and cancerous nasopharyngeal tissue. STUDY DESIGN/PATIENTS AND METHODS: Tissue from six patients with normal and cancerous biopsies was studied using a rapid acquisition Raman spectrometer. RESULTS: Spectra were obtainable within 5 seconds. Consistent differences were noted between normal and cancer tissue in three bands 1,290-1,320 cm(-1) (P = 0.005), 1,420-1,470 cm(-1) (P = 0.006), and 1,530-1,580 cm(-1) (P = 0.002). CONCLUSIONS: Spectral differences appear to exist between normal and cancerous nasopharyngeal tissue. The ability to obtain spectra rapidly supports the potential for future in vivo application.