Nobuhiko Isshiki

Thyroplasty as a New Phonosurgical Technique

In an attempt to examine the surgical possibility of changing the vocal cord position and tension by reforming the thyroid cartilage, an experimental study was made using 10 adult dogs. Hoarseness produced by section of the recurrent laryngeal nerve was generally much improved by vertical incision on the thyroid ala and slipping in of the lateral cartilage segment. Four types of thyroplasty were proposed from the functional viewpoint. Their effects on the vocal cord are (1) lateral compression, (2) lateral expansion, (3) relaxation (shortening) and (4) stretching (lengthening) respectively. Possible indications for each type of thyroplasty were described with reference to specific laryngeal diseases. The advantages of thyroplasty were emphasized namely, that the intervention inside the thyroid cartilage is minimal and therefore fine and reliable adjustment is possible during surgery. Thyroplasty thus offers a new possibility in phonosurgery.

Thyroplasty Type I (Lateral Compression) For Dysphonia Due To Vocal Cord Paralysis Or Atrophy

Based on the experimental results of thyroplasty, thyroplasty type I which aims at medical shifting the vocal cord was performed on 8 patients with dysphonia, 6 with vocal cord paralysis and 2 with vocal cord atrophy. The surgery was conducted on either in- or out-patient basis and local anesthesia was used. Usually, a rectangular incision was made on the thyroid cartilage at the level of the vocal cord, and the fragmemt was depressed inward. A cartilage piece taken from the opposite side was used as a wedge, if necessary, to enhance the effect of lateral compression of the vocal cord. The voice after surgery was generally satisfactory, except in one case of traumatic vocal cord paralysis. Complications such as stridor or dyspnea were nil. As surgical intervention inside the thyroid cartilage is minimal, fine and reliable adjustment of depression is possible during the surgery.

Experimental study of a newly developed bilayer artificial skin

A bilayer artificial skin composed of an outer layer of silicone polymer and an inner sponge layer of collagen containing chondroitin 6-sulphate was developed by modifying the technique proposed by Yannas et al. The artificial skin was placed on the skin defects on the backs of rats. Histological observation indicated that fibroblasts and capillaries infiltrated into the pores and filled in lattice spaces, resulting in synthesis of the connective tissue matrix and absorption of the original network of collagen and chondroitin 6-sulphate. Epidermal cells migrated from the edge of the wound between the two layers. Post-operative contracture in the wound with the artificial skin was significantly less than in the control.

A new skin equivalent : keratinocytes proliferated and differentiated on collagen sponge containing fibroblasts

Three types of artificial skin containing keratinocytic components were prepared and tested for comparison. Keratinocytes were cultured on the artificial skin dermis (collagen sponge) by the air-liquid interface culture method. In order to create continuous keratinocytic layers on the artificial skin dermis, pores of its uppermost layer were filled beforehand with type I collagen gel, Matrigel, or fibroblasts. A band of keratinocytes consisting of two to six cell layers was formed on collagen gel-coated artificial skin dermis. On Matrigel-coated artificial skin dermis, keratinocytes were piled up into about 20 cell layers, but cell differentiation was incomplete; cornified material was not fully developed, and the proportion of cuboidal cells was very high compared with normal epidermis. Keratinocytes formed continuous layers on the fibroblasts-artificial skin dermis complex without gel coating. Keratinocytes proliferated well and differentiated properly on this matrix, and their histologic appearance was similar to that of normal epidermis. Thus keratinocytes cultured on the fibroblast-artificial skin dermis complex seem to be a good skin equivalent.

Recent Modifications in Thyroplasty Type I

Among thyroplasties, type I is the most frequently used for medialization of the vocal cord. Follow-up study on patients indicated that reversion of voice can occur after operation. Revision was done in five cases with improvement of voice. On the basis of this experience, modifications were made in the technique of thyroplasty type I. They include 1) cutting the calcified cartilage with minimal intervention in the soft tissue, 2) fixation of the window with a silicone plug to enhance medialization, and 3) overmedialization of the vocal cord and definition of criteria for it that can be used during surgery.

Re-freeze dried bilayer artificial skin

A bilayer artificial skin composed of a silicone sheet and a collagen sponge sheet was developed by us in 1986, modifying Yannas and Burkes technique. It was used in experimental animals and clinically, both with success; but the artificial skin was inconvenient for clinical use in terms of disinfection and preservation. In an attempt to reduce the drawbacks, we developed a re-freeze dried artificial skin. Experiments were conducted to examine whether the re-freeze dried material is equivalent to the prototype one. A significant difference between the two was found in tensile tests but not in experimental and clinical effects.

Clinical Significance of Asymmetrical Vocal Cord Tension

The effects of asymmetrical tension on the vibratory pattern of the vocal cords were studied in two kinds of experiments: 1) high speed motion picture photography of artificial voice production in excised canine and human larynges, and 2) computer synthesis of voice and vocal cord vibration via a theoretical model incorporating the physiological parameters required for phonation. In both approaches the asymmetrically tensed vocal cords consistently vibrated in three distinct modes which depend partly on the rest positions of the vocal cords; Type I. For rest positions at or near closure, the two cords vibrate at the same frequency with glottal closure every period, and with the tense cord preceding the lax one in phase and with the line of contact moving toward the tenser cord during the closed phase. The voice produced is not hoarse; Type II. For wider rest positions glottal closure occurs irregularly, the vibrations become complex and less periodic, and the voice becomes hoarse; Type III. The glottis never closes and the vibrations become more periodic with reduced amplitude. Supplementary strobo-scopic observations suggest a procedure for diagnosing tension asymmetry and the implications for surgical treatment for disorders of vocal pitch are discussed.

Progress in Laryngeal Framework Surgery

This paper reviews progress in laryngeal framework surgery since it was first reported about 25 years ago. The success of this type of surgery requires both a basic knowledge of the physiology of phonation, in order to make decisions about the surgical procedure, and surgical skill, in order to accomplish the intended procedure successfully. The main reason for hoarseness is imperfect closure of the glottis, but the second most important reason for hoarseness, increased stiffness of the vocal fold, cannot be corrected by mere medialization of the vocal fold. Laryngeal framework surgery is different in concept from conventional surgery, which is intended to remove the lesion. Controversial points discussed here regarding type I thyroplasty include: (i) whether the cartilage window should be removed; (ii) materials for fixation of the window; and (iii) comparison of type I thyroplasty with arytenoid adduction. A new surgical treatment for spasmodic dysphonia and its results in three patients are described briefly. Surgery for raising the vocal pitch requires further improvement. In the future, laryngeal framework surgery will have wider application in treatment of dysphonias, such as asthenic voice due to atrophy in professional singers or aging, pitch problems in females and gender identity disorder and spasmodic dysphonia.

Vocal Fold Atrophy and its Surgical Treatment

The effectiveness of surgical treatment for vocal fold atrophy of various causes was examined. Type I thyroplasty was performed on 31 patients with vocal fold atrophy, often bilaterally and occasionally combined with type III thyroplasty. Of these 31 patients, 3 patients underwent the operation twice, for a total of 34 operations. The surgery was found to be effective in improving the voice quality and the ease of phonation. When a scar or sulcus was present, the results were not as satisfactory. The intraoperative decision-making process as to which procedure to perform is extremely important for achieving an optimal voice, and should be based on the intraoperative voice quality, fiberoptic findings, and manual tests. In operations for vocal fold atrophy in which the vocal folds are mobile, a silicone shim should be firmly fixed to prevent migration. Overcorrection is generally recommended. No complications were encountered. It was often the increased ease of phonation rather than the improved voice quality that patients appreciated after surgery.

Evaluation of a bilayer artificial skin capable of sustained release of an antibiotic

A bilayer artificial skin, composed of an upper silicone sheet and a lower collagen sponge, has been developed by modifying a technique proposed by Yannas and Burke. We have applied it clinically with success, but infection sometimes occurred in the area where the artificial skin was placed. To use it safely in an infected wound, we developed a new type of artificial skin capable of sustained release of antibiotic. Microspheres of poly-L-lactic acid containing an antibiotic, were installed in the upper silicone sheet. The usefulness of the new type of artificial skin was suggested by in vitro studies.