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Laryngotracheal Reconstruction in Canines
Fixation of Autologous Costochondral Grafts Using Polylactic and Polyglycolic Acid Miniplates
Christopher M. Long, MD;
Stephen F. Conley, MD;
Andre Kajdacsy-Balla, MD, PhD;
Joseph E. Kerschner, MD
Arch Otolaryngol Head Neck Surg. 2001;127:570-575.
ABSTRACT
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Objective To examine the feasibility of a new method of laryngotracheal reconstruction
(LTR) that uses a bioabsorbable plating system consisting of polylactic and
polyglycolic acid and provides some advantages over currently used methods.
Design and Interventions Anterior subglottic stenosis was created in 10 beagles that then underwent
LTR using an autologous costochondral graft. External laryngotracheal framework
and cartilage grafts were secured using a sheet and screws made from a copolymer
composed of polylactic and polyglycolic acid. Animals were humanely killed
at 40, 60, and 90 days, and specimens were submitted for pathological examination.
Histologic analysis included evaluation for inflammatory reaction, polylactic
and polyglycolic acid incorporation into cartilage, cartilage necrosis, cartilage
remodeling, and graft epithelialization.
Results All animals underwent LTR after creation of a subglottic stenosis without
episodes of airway compromise. After LTR, all airways were returned to prestenosis
diameter without significant complication, and all animals were immediately
extubated after surgery without difficulty. After the animals were killed,
distraction of the stenotic cricoid area was demonstrated in 100% of the cases.
Significant necrosis was noted in 2 of 10 grafts grossly; however, histologic
analysis demonstrated significant areas of viable cartilage, areas of cartilage
remodeling, and good epithelialization despite graft necrosis. Complete epithelialization
of grafts was noted in the other 8 specimens.
Conclusions Using a canine model, we demonstrated a bioabsorbable plating system
that offers an effective method for LTR. This model has the advantages of
providing external support to the operated laryngeal and tracheal framework,
elimination of the difficulties of suture placement, and potential future
failure while offering rigid external fixation of a cartilage graft.
INTRODUCTION
THE TREATMENT of subglottic stenosis (SGS) continues to challenge those
involved in the care of patients with this pathological condition. Treatment
options have evolved from the use of tracheostomy and anterior cricoid split
to more complex procedures designed to expand the airway, most commonly through
the use of autologous cartilage grafts. Attempts at new surgical procedures
have been designed to improve the ability to provide a stable and appropriate-sized
airway and to reduce postoperative morbidity and mortality. Despite these
attempts, many surgical procedures for the resolution of SGS remain technically
challenging and present significant opportunity for morbidity and mortality
due to factors such as long-term stenting, long-term intubation, and long-term
use of narcotics for sedation.
One method to attempt to lessen the technical difficulty and morbidity
and mortality in laryngotracheal reconstruction (LTR) for SGS involves the
use of external fixation techniques. Initial attempts with external fixation
techniques have produced mixed results. The present study examined a plating
system composed of a copolymer of polylactic and polyglycolic acid (PLA-PGA)
to perform single-stage LTR (SS-LTR) using an autologous costochondral graft
in a canine model with SGS with immediate extubation after surgery.
MATERIALS AND METHODS
Animals were treated in accordance with the Public Health Service Policy
on Humane Care and Use of Laboratory Animals, the National Institutes of Health
Guide for the Care and Use of Laboratory Animals, and the Animal Welfare Act;
the animal use protocol was approved by the Institutional Animal Care and
Use Committee of the Medical College of Wisconsin, Milwaukee. Ten preconditioned
female beagles weighing 9.6 to 12.2 kg (average weight, 11.0 kg) were used
in this study.
On arrival at the Animal Research Center at the Medical College of Wisconsin,
the animals were allowed a 1-week period of adjustment. The initial phase
of this experiment involved the creation of an SGS in all 10 animals. Under
general anesthesia maintaining spontaneous respiration (2.5% thiopental sodium,
1.0-1.5 mL/kg intravenously), the cricoid cartilage was brought into view
using a Killian suspension apparatus and a Zeiss operating microscope. An
electric drill and cutting burr were used to surgically remove mucosa and
perichondrium in the area of the cricoid and the first 2 tracheal rings. The
animal was then allowed to recover. At 1-week intervals the stenotic site
was reinspected using the previously described method to assess for scar formation.
Any granulation tissue was excised, and subsequent burr procedures were performed
as deemed necessary. Subglottic narrowing of 25% to 50% was desired as measured
by sizing the airway with endotracheal tubes. The animals required 2 to 3
procedures in which the subglottic mucosa was denuded with the electric drill
and burr to achieve this level of stenosis. All animals achieved acceptable
SGS within 6 weeks.
The second phase of the study consisted of performing LTR in the area
of the SGS through the use of a costochondral graft fixed in place with a
bioabsorbable plate and screw system to expand the stenotic area.
All animals were treated with 500 mg of cefazolin intravenously before
surgery. Anesthesia was induced with 2.5% thiopental sodium intravenously
(1.0-1.5 mL/kg) and atropine, 0.1 mg/kg, intravenously. Animals were intubated
endotracheally and maintained under general anesthesia with 0.5% to 1.0% inhalational
halothane. Animals were mechanically ventilated (2 L/min oxygen, tidal volume
of 250 mL, 15 breaths/min) throughout the procedure and had continuous cardiac
and pulse oximetry monitoring.
The neck and right anterior chest were shaved and sterilely prepared
with povidone-iodine solution. The area overlying the first "floating rib"
was infiltrated with 1% lidocaine with 1:100 000 epinephrine. A horizontal
incision was made and dissection through the intercostal muscles was performed
to expose the costochondral graft site. The costochondral graft was harvested
with sharp dissection, and care was taken not to disturb the pleura to prevent
pneumothorax. The graft was placed in sterile isotonic sodium chloride solution
(saline), hemostasis was ensured, and the wound was closed in layers using
absorbable sutures. A drain was not used.
A vertical midline cervical incision was then carried out over the larynx
after infiltrating with 1% lidocaine with 1:100 000 epinephrine. The
strap muscles were divided along the median raphe to allow exposure of the
larynx, cricoid, and superior trachea. A midline incision was then made through
the inferior half of the thyroid cartilage and extended through the cricoid
cartilage and the first 2 tracheal rings. The costochondral graft was shaped
in an elliptical fashion to allow placement and expansion of the laryngeal,
cricoid, and tracheal incision. The perichondrium was left intact along the
graft surface that was to face the airway lumen. Costochondral graft dimensions
ranged from 0.3 to 0.6 cm wide and 2.4 to 4.0 cm long (mean area, 2.8 cm2). The graft was then attached to a PLA-PGA copolymer plate cut from
a 50 x 50 x 0.75-mm sheet (LactoSorb part 915-2832; W. Lorenz
Company, Jacksonville, Fla) with 1.5 x 4.0-mm PLA-PGA screws (LactoSorb
part 915-2315). The graft was fixed to the plate with 2 screws, 1 superior
and 1 inferior (Figure 1). The screw
hole was drilled through the plate and graft as a single unit using a pneumatic
drill and a 1.2-mm drill bit. Saline irrigation was used throughout drilling.
The drill hole was manually tapped with a 1.5-mm tap, and the screw was advanced
until tension caused the screw head to break off, as designed by the manufacturer.
The bioabsorbable plate, now attached to the costochondral graft, was heated
to allow for molding of the plate to conform to the external structure of
the larynx and trachea, with the graft positioned to expand the incision made
through the area of airway stenosis. The heating source used for the plate
molding is an enclosed saline bath provided by the manufacturer (W. Lorenz
Company). The bioabsorbable plate–costochondral graft unit was secured
into place using four 1.5 x 5.0-mm PLA-PGA copolymer screws (LactoSorb
part 915-2326). Screws were placed through 2 holes drilled and tapped as above
in the thyroid and cricoid cartilage (Figure
2). The wound was irrigated and closed in layers over a 5-mm Penrose
drain using absorbable sutures. Bacitracin ointment was placed over the wounds.
All animals were extubated when breathing spontaneously.
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Figure 1. Costochondral graft fixed to a
bioabsorbable plate with 2 bioabsorbable screws.
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Figure 2. Bioabsorbable plate–costochondral
graft unit fixed to the external airway with 2 bioabsorbable screws in each
of the thyroid and cricoid cartilages.
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Drains were removed and regular diets were started on postoperative
day 1. Treatment with oral cephalexin (20 mg/kg per dose, 4 times per day)
was continued until postoperative day 5. All animals were closely monitored
for wound infections and airway integrity.
Humane killing was undertaken 40 days (3 animals), 60 days (3 animals),
and 90 days (4 animals) after surgery using euthanasia solution consisting
of highly concentrated pentobarbital and phenytoin as approved by the Panel
on Euthanasia of the American Veterinary Medical Association. The laryngotracheal
complex was removed. Gross observations were made and sections were sent for
histologic examination. Slides were analyzed for graft viability, presence
of inflammatory reaction, and presence of graft mucosalization.
RESULTS
All 10 dogs underwent stenosis-creating procedures. These animals developed
mature SGS before LTR, with airway narrowing of 25% to 50%. None of the animals
developed stridor at rest, and tracheostomy was never required to rescue an
animal with critical airway stenosis.
Laryngotracheal reconstruction was performed on all animals without
intraoperative complications. After completion of the LTR, extubation was
successfully performed once the dog was breathing spontaneously in all cases.
There were no instances of respiratory distress or stridor during the immediate
or prolonged postoperative period. No animal required reintubation, and there
were no incidences of graft dislocation or migration causing airway compromise.
After LTR, all airways were returned to prestenosis diameter, as measured
by endotracheal tube, without significant complication. Minor complications
occurred in 4 of 10 animals. Two dogs developed small chest wound hematomas
that resolved without surgical or medical management. Two different dogs developed
a small amount of serous drainage from their neck wounds on postoperative
days 7 and 9. Both subsided with administration of oral cephalexin (20 mg/kg
per dose, 4 times per day) for 5 days.
After humane killing, gross examination of the laryngotracheal complex
demonstrated distraction of the cricoid cartilage in 100% of the cases. Two
animals killed at 40 days had evidence of graft necrosis on gross inspection.
These grafts were not associated with the animals that developed wound infections.
Histologic analysis demonstrated cartilaginous resorption but also significant
areas of viable cartilage, areas of cartilage remodeling, and good epithelialization
despite graft necrosis (Figure 3).
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Figure 3. Histologic analysis of a graft
with gross necrosis demonstrating cartilaginous resorption but also significant
areas of viable cartilage, areas of cartilage remodeling, and good luminal
epithelialization.
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The other 8 dogs demonstrated graft survival and essentially complete
epithelialization of the luminal surface of the graft (Figure 4). The only exceptions to complete epithelialization were
small areas of granulation tissue noted on the luminal surface of 4 of 10
grafts. These grafts were from animals killed at 40 days (n = 2), 60 days
(n = 1), and 90 days (n = 1). This granulation tissue seemed to be associated
with a PLA-PGA screw protruding into the lumen and contacting the newly formed
graft mucosa (Figure 5). The amount
of granulation tissue was small in all cases and did not clinically compromise
the airway in any of the animals. Acute inflammatory reactions were noted
in the vicinity of the plate. No granulation tissue was noted, however.
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Figure 4. Grossly viable graft with complete
epithelialization of the luminal surface of the graft.
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Figure 5. Granulation tissue associated
with a bioabsorbable screw protruding into the lumen and contacting the newly
formed graft mucosa.
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The PLA-PGA copolymer plating material was present in all specimens.
At 40 and 60 days after implantation, the plates and screws appeared intact
and rigid. Figure 6 demonstrates
a screw tract incorporated within viable cartilage. At 90 days, the plating
material had lost structural integrity and crumbled easily during specimen
preparation.
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Figure 6. Histologic section of a screw
tract incorporated within viable cartilage.
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COMMENT
The evolution of surgical management of SGS in children has greatly
improved the morbidity and mortality of this patient population. In 1980,
Cotton and Seid1 introduced the anterior cricoid
split. After modifications and specific guidelines were created, Cotton et
al2 reported that 70% of patients were successfully
extubated without the need for tracheotomy.
Further advances involved the use of more extensive airway incisions
to alleviate subglottic and tracheal stenosis and the use of cartilaginous
grafts to assist with maintaining the patency of the airway and its increased
intraluminal diameter. In most cases, mild to moderate SGS can now be managed
as a single-stage procedure (SS-LTR), with reconstruction of the laryngotracheal
framework performed over an endotracheal tube stent removed several days to
a week after surgery, thus avoiding the need for a tracheotomy.
Despite these advances in the treatment of subglottic and tracheal stenosis,
several aspects of the surgical procedures used in resolving this pathological
condition remain problematic. Laryngotracheal reconstruction can be technically
challenging, especially in a young child, requiring precise placement of sutures.
Misplaced sutures or sutures that pull away from a graft or the site at which
the suture is anchored can lead to graft displacement, airway compromise,
and surgical failure to correct the area of stenosis. Postoperative care after
SS-LTR can also be problematic because most surgeons maintain an endotracheal
tube in place as an internal airway stent for several days. Use of this stent
is meant to reduce the chance of a dislodged graft and subsequent airway compromise.
Methods to reduce the difficulty from use of a stent have included reducing
the time intubated and using an indwelling nasotracheal tube without mechanical
ventilation.3 However, especially in younger
children, an SS-LTR still generally requires several days of intubation with
mechanical ventilation and sedation in an intensive care unit. This provides
the potential for accidental extubation and airway compromise as well as difficulties
from medication withdrawal. The risk of complications during this postoperative
phase continues to elicit debate within the literature regarding optimal management.
Zeitouni and Manoukian4 reported 4 complications
in a series of SS-LTRs, including 2 cases of severe narcotic withdrawal requiring
medical treatment. Rothschild et al3 recommend
refraining from the use of paralytic agents during the stenting phase of recovery,
instead titrating analgesics and sedatives for comfort. They demonstrate success
rates similar to those in studies in which paralysis is used. Still, some
would argue that this increases the risk of self-extubation or accidental
extubation and jeopardizes healing because of graft motion.3
The purpose of this study was to examine a new method of LTR that would
provide some advantages over currently used methods. The goals of this method
of LTR were to develop a technique using a well-established model of SGS5, 6, 7, 8, 9, 10
to (1) increase the diameter of a stenotic subglottic airway; (2) provide
a means of external fixation that would immediately and rigidly maintain the
increased diameter created in the incised airway; (3) provide the rigid external
fixation without interfering with laryngeal and tracheal growth and development;
and (4) provide a faster, technically less challenging and potentially more
rigid and secure method of fixating a tissue graft in the incised airway.
The advantages of providing rigid external support through an external
fixation system in LTR were initially identified by Zalzal and Deutch,11 who used a metallic alloy plating system to successfully
perform LTR in dogs. Weisberger and Nguyen12
reported use of an external fixation system using a Vitallium alloy in adults,
with 77% success. However, Mitskavich et al13
performed anterior cricoid split in a porcine model with SGS and noted intraluminal
migration of the plates in 50% of the subjects, which raised concerns regarding
using such external fixation systems in a developing larynx. The permanence
of the metallic plating systems also produced concerns regarding long-term
laryngeal and tracheal growth and development.
Use of bioabsorbable plating materials has become well accepted in the
treatment of osseous craniofacial diseases in children. The resorbable quality
of such materials is ideal for use in children because although it provides
initial rigid support, it is resorbed over time and has minimal long-term
impact on structures that are still growing and developing. The resorbable
quality of these materials also limits concerns regarding migration of the
rigid fixation material or the need for eventual removal of the material.
Polylactic and polyglycolic acid, a copolymer currently used extensively in
pediatric craniofacial surgery, demonstrates initial strength similar to titanium.14 Degradation seems to occur over a 12-month period.
At 2 months, there is no change in the size of this type of implant; by 6
months, implant material has significant loss in size; and by 9 months, greater
than 95% of the implant is resorbed.15
The possibility of using bioabsorbable materials in airway surgery was
introduced by Willner and Modlin,16 and only
one other study17 has been published investigating
the use of this material in airway reconstruction. In these investigations,
the resorbable material was not used to fixate a cartilaginous graft. Also,
in both of these studies, the bioabsorbable plate was sutured into place and
not held with screw fixation, making true rigid fixation less likely. Our
study is the first to incorporate PLA-PGA plates and screws to perform SS-LTR.
Use of a plating and screw system provides the opportunity for a more rigid
external fixation system that can add immediate stability to the expanded
airway and maintain its increased diameter. In addition, our model relies
on screw integrity, rather than sutures, to maintain its rigidity and to hold
a costochondral graft in place.
Although the efficacy and ability of bioabsorbable materials to achieve
rigid fixation is well documented when used in an osseous environment, transferring
these materials and the principles of rigid fixation with plates and screws
has not been attempted in a cartilaginous environment. The advantages of this
technique to provide immediate rigid external support to an enlarged airway
are self-evident. The airway would be immediately maintained at its increased
luminal diameter without the need for an interposed material such as a cartilage
graft to keep this increased diameter. The rigid fixation of the airway would
also potentially provide for more rapid extubation and preclude the need for
an endotracheal tube stent, limiting postoperative morbidity associated with
this procedure. The technique of rigidly fixating the airway in its expanded
position also allows for other possibilities in airway reconstruction, eg,
a vascularized, pedicled muscle flap to cover the defect created in the enlarged
airway. This might have superior qualities in healing and reduced donor site
morbidity compared with a free cartilage graft.
Even if a cartilage graft within the expanded airway is opted for, the
ability to rigidly fixate this graft without the use of sutures also has some
potential advantages. The technical difficulty of precisely placing multiple
sutures through a graft is eliminated. The procedures performed on these 10
dogs demonstrate that the graft could be fixed to the bioabsorbable plate
in a matter of minutes. The potential difficulty of anchoring sutures to a
rigid external structure, seen more commonly in younger patients, is also
eliminated by having a relatively large plate-graft unit that was easily and
rapidly fixated to the thyroid and cricoid cartilage in this study. Concerns
regarding sutures failing, being misplaced, or pulling away from the cartilage
graft were also eliminated. Potential new difficulties include the costochondral
graft not being held in place by the plate and screw system, although this
did not occur in our study. The results of our study demonstrated overall
success. The procedure did not present any technical challenges and could
be completed in a timely manner. All animals were extubated immediately without
any airway complications during this study.
The costochondral graft was viable in 8 of 10 cases. In the remaining
2 cases, where significant necrosis was identified, distraction of the subglottic
airway was maintained by the fixed plates, and good epithelialization occurred
over most of the grafted site. There is a possibility that graft survivability
was affected by heating the plate-graft unit to allow for molding of the plate
to the laryngeal and tracheal framework. Future studies are planned in which
the plate would be heated and molded before fixating the costochondral graft,
thus avoiding the high level of heat to, and possible damage of, the cartilage
graft. Another possibility is that a certain amount of graft necrosis, with
neochondrification or cartilage remodeling subsequently taking place, is the
natural course of this procedure. This possibility was demonstrated by Jacobs
et al,18 who presented similar necrosis and
neochondrification in their histopathologic analysis of cartilage grafts used
in LTR in a rabbit model. Similarly, in our study, all grafts without significant
necrosis demonstrated essentially complete epithelialization. Several of these
grafts also demonstrated some areas of cartilage necrosis, with areas of cartilage
remodeling on histologic examination. Intraluminal granulation tissue appeared
to occur over areas of the graft where the screw came into approximation with
mucosa, but no airway compromise was noted in these cases clinically. An additional
means of dealing with the potential reactivity of the bioabsorbable material
within the airway would be to use a system with a shorter screw or a technique
of "welding" down the excess screw length using a heating unit. This technique
is frequently used in craniofacial surgery to prevent any distal portion of
the screw from penetrating into the intracranial cavity.
This study has some shortcomings that deserve discussion. This is a
small study that does not completely account for the predicted life span of
the PLA-PGA material (12 months). Also, these animals did not have severe
SGS, which might place increased stress on the plate-graft complex. We also
cannot take into account possible long-term effects on voice production or
laryngeal development. Examining these areas would be worthwhile in future
investigations. In addition, this study only examined one possible bioabsorbable
material. Several different products exist, each of which has its own properties,
including rate of resorption, initial strength, and tissue reactivity. The
material used in this study has the quickest rate of resorption and loss of
structural integrity of products currently available. This might be the most
favorable scenario given the desire to limit effects on growth and development
of laryngeal and tracheal framework and the desire to minimize chances for
the migration of materials. However, a material with a somewhat longer period
of resorption might be more advantageous because these materials generally
provide for a lesser degree of tissue reaction during resorption. Alternatively,
potential exists for a manufacturer to design a material specifically for
use in a cartilaginous environment, with applications designed for procedures
such as LTR. This material would likely be superior to those that have been
primarily designed for specific applications within an osseous environment.
CONCLUSIONS
This study presents a new technique for LTR that has the potential advantage
of providing external airway support within a system of rigid fixation of
a graft with a plate and screw system. The bioabsorbability of this system
within a developing and growing larynx is particularly attractive, as is the
speed and relative technical ease with which the procedure is performed. Future
investigations using this or similar models would be worthwhile to further
determine the utility of these techniques.
AUTHOR INFORMATION
Accepted for publication September 22, 2000.
This study was funded in part by a research grant from the Children's
Hospital of Wisconsin Foundation Grant, Milwaukee.
Presented at the American Society of Pediatric Otolaryngology meeting
at Combined Otolaryngology Spring Meetings (COSM), Orlando, Fla, May 17, 2000,
and second place winner of the William P. Potsic Basic Science Research Award
presented at COSM, May 17, 2000.
From the Departments of Otolaryngology and Communication Sciences (Drs
Long, Conley, and Kerschner) and Pathology (Dr Kajdacsy-Balla), Medical College
of Wisconsin, Milwaukee.
Corresponding author: Joseph E. Kerschner, MD, Department of Otolaryngology
and Communication Sciences, Children's Hospital of Wisconsin, 9000 W Wisconsin
Ave, Milwaukee, WI 53226.
REFERENCES
| |
1. Cotton RT, Seid AB. Management of the extubation problem in the premature child: anterior
cricoid split as an alternative to tracheotomy. Ann Otol Rhinol Laryngol. 1980;89:508-511.
ISI
| PUBMED
2. Cotton RT, Myer CM, Bratcher GO, Fitton CM. Anterior cricoid split, 1977-1987. Arch Otolaryngol Head Neck Surg. 1988;114:1300-1302.
FULL TEXT
|
ISI
| PUBMED
3. Rothschild MA, Cotcamp D, Cotton RT. Postoperative medical management in single-stage laryngotracheal reconstruction. Arch Otolaryngol Head Neck Surg. 1995;121:1175-1179.
PUBMED
4. Zeitouni AG, Manoukian J. Severe complications of the anterior cricoid split operation and single-staged
laryngotracheoplasty. Ann Otol Rhinol Laryngol. 1994;103:723-725.
PUBMED
5. Schmidt FW, Toohill RT, Piazza LS, Chipman TJ, Campbell BH. CO2 laser management of laryngeal stenosis. Otolaryngol Head Neck Surg. 1986;95:485-490.
PUBMED
6. Healy GB. An experimental model for the endoscopic correction of subglottic stenosis
with clinical applications. Laryngoscope. 1982;92:1103-1115.
PUBMED
7. McGee KC, Toohill RT, Nagle JW. CO2 laser repair of subglottic and upper tracheal stenosis. Otolaryngol Head Neck Surg. 1981;89:92-95.
PUBMED
8. Toohill RJ, Martinelli DL, Janowak MC. Repair of laryngeal stenosis with nasal septal grafts. Ann Otol Rhinol Laryngol. 1976;85:600-608.
PUBMED
9. Koufman JA, Branch ME, Ryu JH. A comparison of the carbon dioxide and neodymium:YAG lasers in a canine
model of acquired subglottic stenosis. J Otolaryngol. 1988;17:223-226.
PUBMED
10. Rice DH, Colman M. Repair of subglottic stenosis with a free perichondral graft. Arch Otolaryngol. 1982;108:25-27.
PUBMED
11. Zazal GH, Deutch E. External fixation using microplates after laryngotracheal expansion
surgery. Arch Otolaryngol Head Neck Surg. 1991;117:155-159.
FULL TEXT
| PUBMED
12. Weisberger EC, Nguyen CT. Laryngotracheal reconstruction using a Vitallium alloy miniplate. Ann Otol Rhinol Laryngol. 1996;105:363-366.
PUBMED
13. Mitskavich MT, Rimell FL, Shapiro AM, Post C, Kapadia SB. Laryngotracheal reconstruction using microplates in a porcine model
with subglottic stenosis. Laryngoscope. 1996;106:301-305.
PUBMED
14. Pietrzak WS, Sarver DR, Verstynen BS. Bioabsorbable polymer science for the practicing surgeon. J Craniofac Surg. 1997;8:87-91.
ISI
| PUBMED
15. Eppley BL, Reilly M. Degradation characteristics of PLLA-PGA bone fixation devices. J Craniofac Surg. 1997;8:116-120.
ISI
| PUBMED
16. Willner A, Modlin S. Extraluminal laryngotracheal fixation with absorbable miniplates. Arch Otolaryngol Head Neck Surg. 1995;121:1356-1360.
PUBMED
17. Weisberger EC, Eppley BL. Resorbable fixation plates in head and neck surgery. Laryngoscope. 1997;107:716-719.
PUBMED
18. Jacobs IN, Podrebarac P, Boden SD, Chen M. Graft healing in laryngotracheal reconstruction: an experimental rabbit
model. Ann Otol Rhinol Laryngol. 1999;108:599-605.
PUBMED
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