LARYNGEAL FRAME WORK SURGERY
PAST, PRESENT AND FUTURE
Introduction : Laryngoplasty was introduced and popularised by Isshiki in the 1970’s. Dr.Anand from MCV add gone to Kyoto University Hospital, Japan in 1998. He was trained there by Dr.Isshiki & Dr.Kojimi.
It was Dr.Isshiki systamatic proposal of different laryngoplasty clasifications that popularised this field. Laryngoplastic phono surgery is performed for voice alteration. Phono surgery procedures are most often performed to correct incompetent larynx caused by Vocal Cord paralysis, atrophy or scarring. Amongst these the most often performed procedure to correct glottic incompetence is Type I Medialisation thyroplasty. The other types of Laryngical frame work surgery are out lined below.
Laryngeal Frame Work Surgery
|Vocal Cord Medialisation||Type I|
|Vocal Cord Lateralisation||Type II|
|Anterior Commisure Set back||Type III|
|Cricothyroid Approximation||Type IV|
|and anterior commisure advancement|
Though literature was available earlier (Nobuhiko Isshiki, 1989) thyroplastic phono surgery was taken up by the Indian ENT fraternity in the mid 90’s. Reasons for the delay in application of these techniques was due to lack of practical training, equipment, sialastic blocks and other prosthesis.
To substitute for sialastic in the initial 7 cases of Type 1 Thyroplasty (1994, 1995) we had used autograft cartilage taken from nasal septum and thyroid alae superior border. Shims of tantalum for Type IV (anterior commissure advancement) was substituted by medical grade stainless steel. In our series out of a total 91 cases of Laryngoplastic phono surgery 63 cases underwent Type I medialisation laryngoplasty alone or in combination. These alone were included in the study. Present generation of thyroplasty sets from the west offer total solutions of information, equipment and ready made prosthesis (William W. Montgomery 1997) As the cost of these sets and the disposable items is high it is difficult to use them in existing Indian conditions.
Considering the above a set of instruments has been designed based on an anatomical study of cadaver larynges. This helped us to standardise instrumentation to suit the anatomical parameters of our patient groups. To cut down cost of disposables, multiple size prosthesis are avoided and simple techniques of shaping sialastic is proposed. To understand the difficulties and needs of other surgeons an opinion poll was conducted amongst the 20 participants of a phono surgery cadaver training workshop and the feed back was used to redesign the sialastic trimming technique. This apart from saving operating time avoids wastage of sialastic.
Design of Instruments :
A set of instruments for Type 1 Thyroplasty has been developed. These are useful to make the cartilage window at the desired levels and size with reduced operating time. The instruments were designed during the cadaver study and prototypes were made of wood and brass (Fig I.A)
Modifications were made in the prototypes for the determination of the ideal window sizes. The final design was made out of surgical steel (Fig.I.B) and used for live surgery.
Fig.I.A – Prototype Instruments for type I thyroplasty
Fig.I.B – Final design instruments for type I thyroplasty
11 adult cadaver human larynges were chosen. These included 6 male and 5 female larynges (Fig II, Fig V). The overlying soft tissue was removed to expose the thyroid cartilage and the tracheal transaction was made at 3 – 4 tracheal ring. The thyroid cartilage was measured carefully to determine the following.
- Location of thyroplasty Type 1 window so that it lies opposite the membranous vocal cord.
- Margin of error in the vertical plane that can be allowed in placement of window so that medialisation of the vocal cord alone without displacement of false cord is possible.
- Size of prosthesis that will be ideal to medialise the cadaver vocal cord.
- Thickness of thyroid alae in the four borders of the window.
Fig-III Thyroid cartilage exposed. 5mm caliper to mark point in midline 5mm from lower border. Swivel caliper laterally from this. The first point is marked with Diathermy.
The correct level of vocal cord was marked in cadaver larynx by passing needles from outside to vocal cord margin perpendicular to the thyroid alae. Using the easily identifiable midline lower border of thyroid alae a point is marked 5 mm above. From this point 5 mm laterally the anterior boundary of thyroplasty window is marked as the first point.(Arrow in Fig. III).
As the first point will give only the anterior boundry of the window, the inferior border was chosen parallel and 2 -3 mm above the lower border of thyroid cartilage (Fig IV). The vocal cords from anterior commissure slope inferiorly in relation to thyroid alae. As the window is made parallel to the inferior border which has a similar slope the window and vocal cord axis becomes parallel
Fig-IV Male or female marker is chosen and medial edge of instrument is kept at the first point. Lower border of instrument moved 3 mm away and parallel to lower border of thyroid alae. Diathermy used to burn 4 points of the window.
Fig.V – Sialastic block fixed into thyroplasty window
Fig.VI – Medialised left vocal cord Cadaver study
When windows were made in these locations, the mid point of anterior 2/3 of true vocal cord (confirmed by passing the needle) always lay within the window. With a window size of 10 X 5 mm in male and 9 X 4 mm in female the vertical margin of error was determined to be just adequate to medialise only the vocal cord and not the superior false cord (Fig. V & Fig. VI). A size larger than this was found to medialise the ventricular band and smaller size medialised subglottic tissue alone posteriorly. From the cut window edges, the thickness of the thyroid cartilage in all 4 borders were measured (Table I).
TABLE – I
Average thickness of Thyroid cartidge in relation to Type-I cartidge window.Candaver Study. Note the thin anterior border
Due to the tougher cadaver tissues to medialise the true cord adequately more height of sialastic prosthesis was required. Hence in this study the necessary height of sialastic for medialisation was determined during live surgery.
Pre – Operative Evaluation of the Patient and Selection :
The larynx is examined by video laryngoscopy using the 90 degree Berciward laryngoscope and the flexible nasopharyngoscope. The recordings were made in video Tape with simultaneous audio input. This evaluation is repeated 1 month following thyroplasty and again 3 months post – operatively. These evaluation are useful for determining position of the paralysed vocal cord, arytenoid and the amount of phonatory gap. We are not using stroboscopy as the video laryngoscopic images when seen in slow motion gives adequate information regarding mucosal pathology. Voice was seperately assessed by Speech Pathologist to determine maximum phonation duration (M.P.D.). As this can be checked during the surgery under local anaesthesia it was found to be very useful. Manual compression tests were also employed to assess possible outcome of medialisation. However due to ossified cartilge compression tests were not used in patients above 50 years of age. The patients with movement, tension disorders of more than 3 months duration were included in the study. 22 patients had unilateral recurrent laryngeal nerve paralysis. Out of these 5 had concomittant vocal cord tension abnormalities. 6 patients had bilateral sulcus vocalis and underwent bilateral medialisation. One patient had a medialisation laryngo plasty along with woodman’s lateralisation operation. A total of 29 cases were operated upon from 1994 – 2001.4.00
Anaesthesia & Technique :
The procedures are done under local anaesthesia. Inj. Fortwin and Phenergan are given according to body weight 1 hour before surgery. Atropine was not used as the induced dryness changes vocalisation. The line of incision and the underlying musculature are infiltrated with 2 % Xylocaine and 1 : 2,00,000 Adernaline.
External incision is made horizontally 1 cm above the inferior border of the thyroid lamina. There is a tendency to make the incision too low which makes access difficult. After elevation of skin flaps strap muscles are retracted and not cut. Jolly thyroid retractor for the skin flap and a mastoid self retaining retracter for the strap muscles are placed. Out of the 22 patients with unilateral recurrent nerve paralysis 13 underwent type-I thyroplasty alone 4 in combination with Arytenoid adduction and 5 in combination with Type III or Type IV thyroplasty.
Fig.VII Marking the first point with 5mm caliper & diathermy. This corresponds to the anterior boundary of thyroplasty window. A skin hook stabilises the thyroid alae.
Fig.VIII. Window marker is placed with the anterior border in line with the first point. The inferior border is parallel and 2-3mm away from lower margin of thyroid alae.
|Teflon Injection||Sialastic Implant Medialisation||Sialastic (or) Ceramic Implant with Reinnervation||Arytenoid Adduction|
2 – 4 mm defect
Cannot correct Fixed arytenoid
Does not Restore tensing
Any size defect
Can correct fixed arytenoid
Does not restore tensing
Any size defect
Can correct fixed arytenoid
Can restore pitch control & quality
GA or LA
Fig- IX The 4 points of the window is joined by knife in cartilage or by 6 mm cutting burr if ossified. Care in creating lower border as the bridge of tissue below window should not be broken. Drill or knife should not breach inner perichondrium.
For Type – I Thyroplasty :
Essentially the same method of window marking as performed in the cadaver was used. Flexible laryngoscopy was used to assess the medialisation effect as needle technique is not possible. The inferior border of thyroid alae is exposed. The 5 mm caliper is used to locate the medial border of thyroplasty window. The caliper point is kept in midline at the lower margin of thyroid alae and a point 5 mm from the lower border in the midline is marked. Using this point the caliper is swivelled laterally and the first point is marked with monopolar diathermy (Fig. VIII).
This is the medial border of the thyroplasty window. The male or female window marker is kept with the anteromedial margin at this point. The inferior border of the marker is kept 2 – 3 mm away and parallel to the lower border of thyroid alae (Fig VIII). Monopolar diathermy is used to mark the 4 points of the marker on to the thyroid alae. These 4 points when connected completes the window outline
For cutting the window a 6 mm burr is used in cases where the cartilage has undergone ossification. In other cases a 15 blade is sufficient. Cases above 40 yrs required drills to cut the Inferior & Posterior borders. The Cartilage island is preseved carefully and in all 4 borders the inner perichondrium is elevated. Care is taken not to penetrate the inner perichondrium in the anterior margin.
Using the window marker sialastic block with excess height was cut (Fig. X.) Suitable size (20x15x15mm) sialastic blocks of soft grade were supplied by NMP.
Fig-X Keep the male / female marker on the silastic block of size 20mm x 15mm x 15mm. Use the same marker used earlier. Mark the 4 borders with knife / blade. Two blade technique is useful to precisely cut sialastic (Fig. XI)
Fig-XI Two Blade Technique : Use another blade and cut from lateral edge while keeping the first blade in place. As the first knife is seen well through the silastic guiding the second blade is made easy. This gives a sialastic block with an external flange (Fig. XII).
Fig-XII Block cut to size with outer retaining flange.
The anterior border of the sialastic block is made short in height and the block is pressed into the cartilage window. As both the window and implant is cut with the same marker and as the sialastic is pliable it fits the window snuggly. The patients voice and flexible laryngoscope is used as a guide to determine the ideal height. This will be a size that is 2 mm less than the size producing the strained voice of over correction. The excess height is trimmed off the medial border of the sialastic. The transperancy of the sialastic allows inspection of retaining flange in relation to the window cartilage. (Fig. XIII) The implant is kept in place with prolene stitches to the four corners of sialastic (Fig XIV)
Fig.XIII Sialastic with external flange.Cartilage window outline can be seen through the transparent material
Fig. XIV – External flange sutured to Outer perichondrium
Fig.XV Unilateral Medialisation with Autograft Cartilage. Note the crossed proline sutures to prevent extrusion. Final Medialisation pressure on the paralysed structures is less than sialastic.
Fig. XVI. Bilateral Medialisation with Autograft Cartilage in one of the patients with Sulsus Vocalis early in our series.
The voice is judged by the quality and mean phonation duration (MPD). The assessment is done by a Speech Pathologist and the scoring is also influenced by the patients perception. (Table III). Most of the patients had audio recordings and video endoscopic recordings before and after surgery. Out of the 29 cases 12 were judged to have a good post – op voice, 13 were fair and 4 poor (Table IV). We encountered two airway compromises and 2 cases of post -op wound infection (Table V).
TABLE – V
Laryngoplasty Complication : (N=91, 1994 – 2003)
|Intra OP laryngeal Perforation||=||7|
REVIEW AND DISCUSSION
The 4 type of thyroplasty (Nobuhiko Isshiki – 1989) as described by Isshiki have been modified by many authors. As experience is gathered, the location and size of thyroplasty windows have been standardised and variation if any between authors is more due to differences in the average dimensions of larynx in the racial group of patients involved in the particular study. The complex formulaes suggested earlier have been replaced by standardised sizes (W.Montgomery & K.Montgomery – 1997) and the fine tuning is being done by varying the size of the implant.
The implants also come in various types (Antonie Giovanni, – 1999). The most widely used sialastic (Dow corning, Perthese) has to be hand crafted. Cartilage has also been used. Ceramic and other synthetic non bio degradable polymers are used widely (Vocom, Portex). The advantage of pre shaped prosthesis is the operative time saving and the disadvantage is their cost. Cartilage and ceramic prosthesis allow tissue in growth and attain fixation. This feature helps in medialising mobile vocal cords as in sulcus vocalis or partially mobile paretic cords. In these situations sialastic may have a higher slippage or extrusion rate as tissue fixation does not occur. We have used cartilage from patients nasal septum and sialastic with grooves or sutures which fix to the thyroplasty window securely in these cases.
Apart from specifically shaped implants medialisation has been acheived by simple packing with Gore – Tex ribbon in the inner perichondrial pocket(Antonie Giovanni 1999) and the results were comparable to other methods. The method of making an oversize implant and reduce height as per requirement allowed us to minimise implant inventories. The operating time was not unduly prolonged and results favourable.
In Montgomery’s technique the fixed land mark on the thyroid alae is the inferior thyroid tubercle under thyrohyoid muscle (Wiiliam W. Montgomery 1997). We identified the midpoint of the lower border of thyroid alae for fixed land mark. This is not covered by muscle and minimal dissection exposes the same. As dissection is less we did not use intra op sedation which facilitated patients co operation or phonation trials during surgery.
Preserving the cartilage island in the thyroplasty window is favoured by some (Nobuhiko Isshiki 1998) and removal by others (William W Montgomery 1997). Retaining the island gives security against intrusion endolaryngeally and in our series no implant extruded endolaryngeally or externally. A large external flange and fixing the implant with prolene to the thyroid outer perichondrium also help to prevent this.
Intra operative laryngeal perforation can occur in the anterior border of the thyroplasty window while undermining inner perichondrium. Recognising the tear and keeping dissection minimum and fixing implant securely avoids further problems. The post operative airway obstruction is more serious as tracheostomy is required. One patient (No. 22 in Table III) with type-I and type-III combination and another patient (No. 16 in Table III) with type-I and Arytenoid adduction developed post op airway obstruction and required Tracheostomy. One patient developed stridor 48 hours post operatively after under going a Type I thyroplasty with tensioning by anterior commissure advancement. He was managed conservatively avoiding tracheostomy. Bilateral inner perichondrial elevation causing oedema in such cases should be minimised. Intra op steroids may also be used to avoid air way compromise. Both these tracheostomies were temporary and closure was possible within 4 days.
Arytenoid adduction is technically more difficult to perform than the Type I Thyroplasty (Zeitals – 1999 & Zeitals, Hillman – 1998). This is made simpler by cutting out a posterior thyroplasty window to access the arytenoid, CA joint and muscles acting on the arytenoid. In addition to vocal fold palsy this procedure is indicated for arytenoid dislocations and fractures (Maragos – 1999). Complications were reportedly higher with arytenoid adduction (Rosen 1998) than in medialisation thyroplasty. Post op airway obstruction is reportedly more with Arytenoid adduction when compared with Medialisation Laryngoplasty . (Eric. C. Weinman 2000) The post-op airway obstruction can be reduced in arytenoid adduction by creating the posterior thyroplasty window. The advantage of this procedure is the pitch improvement by tensioning the vocal cord (zeitals 1999). Furthur more when Arytenoid adduction is combined with type-I thyroplasty vocal result were better than either of these procedures alone. As an operator gains experience choice of Arytenoid adduction is found to increse in comparision to Type I Medialisation.
Some patients require combination of medialisation with tensioning or relaxing the vocal cord. (Nobuhiko Isshiki – 1998). In our patients ( 19 out of 91) we recognised the need for the combination only during surgery as improvement by medialisation alone was not satisfactory. Relaxing a tense vocal cord can be achieved by anterior commissure set back Type III technique. Tensing a lax vocal cord type IV is the opposite of this and is achieved by crico thyroid approximation or by anterior commissure advancement . We prefer the latter and had used it in combination with type I (Koufman 1986). It is also of interest that this method originally proposed by Dr. Koufman is no longer advocated by him and he prefers arytenoid adduction at present (Koffman – 1999).
A case still in question is the sulcus vocalis. Results with medialisation thyroplasty have been poor (Todd G. Dray – 1999, our case results, personal communication with Dr.Isshiki & Dr.Kojima, Kyoto). The Pre operative Mean phonation duration in these patients was better than unilateral recurrent laryngeal nerve palsy group (Table III). The post op voice showed only minimal improvement of MPD (table III). 4 out of 6 patients felt that the effort to produce voice is less and vocal fatigue improved following medialisation. This group of 4 patients also reported reduction in throat pain following vocal strain. All of them felt that the post op voice is not up to their expectation. An important point we noted was though the 4 patients reported improvement their relatives and friends felt that the voice is the same as per op. Hence the improvement of voice in bilateral sulcus vocalis after Bilateral medialisation is more subjective than objective. The development of autologous tissue transplant in the form of fat injection or facial transfer is more promising than thyroplasty in sulcus vocalis. (Heikki Rihhanen – 1998, Peak Woo 1999 & Nobuhiko Isshiki, Shoji, Kojima & Hirano – 1996).
The last case in our series No. 29 had a Bilateral vocal cord palsy caused by thyroidectomy and a tracheostomy. She had undergone an unsuccesful endoscopic lateralisation operation on the right vocal cord once. After undergoing left vocal cord Lateralisation by woodmans technique the airway improved considerably but the voice was in audible. This was probably due to absence of interarytenoid muscle adduction which is present after Bilat Vocal fold paralysis but will be absent after Bilateral Arytenoid Operations. Hence a left vocal cord medialisation with Type I was performed. She had her tracheostomy closed 15 days after the operation & the voice is poor but audible.
Thyroplasty has been well accepted as a procedure and has been standardised. We have proposed a set of Guidelines that have been evolved through cadaver study to simplify window placement for Type I thyroplasty. Availability of window marking special instruments and prosthesis will enable even the occasional operator to provide a fair voice result. Combination of medialisation laryngo plasty Type – I and Arytenoid adduction provides superior results than Medialisation alone. Bilateral Medialisation thyroplasty Type I for sulcus vocalis produces only subjective improvement and alternate procedures should be considered. GORETEX Thyroplasty is an alternative technique to sialastac.
Our Association with Prof Timothy Mccullough of Madison, USA has encouraged us to use this method developed by him. Advantage in this method is intra operative voice tuning is easier. We now favour this method in large glottic chinks and in older individuals. Again we believe in combination of goretex with arytenoid adduction and tensioning.