Tympanoplasty-Undersurface Graft Technique: Postauricular Approach

Chapter 12 Tympanoplasty—Undersurface Graft Technique


Postauricular Approach



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Since the fundamental principles of tympanoplasty were first introduced by Wullstein1 and Zollner,2 there has been great diversity in the accepted surgical techniques used for repair of the tympanic membrane. The multitude of graft materials employed is a testimony to the difficulty of middle ear reconstruction. With advanced microsurgical techniques, the state of the art has now developed to the extent that graft success rates of 90% to 97% are to be expected.35 Two basic grafting techniques have evolved based on where the graft material is placed in relation to the drum remnant (overlay versus underlay techniques). This chapter presents a method of undersurface grafting. Detailed surgical techniques and appropriate preoperative and postoperative care are presented.



HISTORICAL ASPECTS


Modern middle ear reconstructive surgery represents a culmination of more than a century of contributions by numerous dedicated and innovative otologic surgeons. The term tympanoplasty was originally defined in 1964 by what was then known as the American Academy of Ophthalmology and Otolaryngology’s Committee on Conservation of Hearing as “an operation to eradicate disease in the middle ear and to reconstruct the hearing mechanism without mastoid surgery, with or without tympanic membrane grafting.”6 If a mastoid procedure is included, the term tympanoplasty with mastoidectomy is used.


The era of surgical repair of the tympanic membrane dates as far back as the 19th century. In 1853, Toynbee7 described closure of a perforation of the tympanic membrane using a small rubber disk attached to a silver wire. Ten years later, Yearsley8 advocated placing a cotton ball over the perforation; in 1887, Blake9 introduced the concept of placing a thin paper patch over the membrane. The use of cautery to promote spontaneous healing of tympanic membrane perforations was introduced by Roosa in 187610; he used silver nitrate. Later, Joynt,11 Linn,12 and Derlacki13 described modifications of this technique using various forms of cautery and patches. Closure of tympanic membrane perforations was considered appropriate only for dry central perforations, however. At this point, no one advocated the use of drum closure for the chronically draining ear.


It was not until 1952 that Wullstein1 and Zollner2 revolutionized middle ear surgery by advocating reconstructive grafting of the chronically diseased ear through the use of full-thickness or split-thickness skin grafts. House and Sheehy14 and Plester15 later used canal skin, believing that it more closely resembled the squamous layer of the tympanic membrane. The overall poor success rates of these grafts and the development of iatrogenic cholesteatomas prompted the search for alternative grafting materials.


Shea16 and Tabb,17 working independently, described the use of autogenous vein to close the tympanic membrane. Goodhill18 advocated tragal perichondrium in the mid-1960s, and tympanic membrane homografts became popular a few years later. Glasscock and House19 reported the first sizable series of homograft tympanic membrane transplants in 1968. Interest in homografts has waned, however, largely because of the fear of transmission of infectious diseases. Storrs20 performed the first fascia graft in the United States. Although vein, perichondrium, and homografts still have their advocates, autogenous fascia has now become the standard by which all other grafting materials are measured.


The use of skin grafts required that the tympanic membrane perforation be repaired by laying the graft on top of the denuded drum remnant. This method of repair eventually became known as the overlay technique and was carried over to other forms of grafting material. With the use of connective tissue grafts, the graft material could be placed medial to the tympanic membrane remnant. The success of this approach eventually gave rise to the underlay technique of tympanic membrane grafting; Austin and Shea3 reported a large series. Proponents of the underlay procedure submit that it eliminates many of the problems associated with overlay grafts, such as anterior blunting, epithelial pearl formation, and lateralization of the new drum.


In 1973, Glasscock4 described an underlay grafting technique that relied on a postauricular approach. With minor modifications, this approach continues to be the preferred method of dealing with disorders of the tympanic membrane and the middle ear.




FUNDAMENTALS









PREOPERATIVE PREPARATION




Eustachian Tubal Tests


No clinical test exists for eustachian tubal physiology. Eustachian tubal patency is testable via methods such as the Valsalva maneuver and the Toynbee test, but it is not important in the grand schematic of tympanoplasty. Eustachian tubal physiology tests exist (e.g., the Flisberg test), but are clinically impractical and are not done. A statement attributed to Sheehy is true: “Sometimes the best test of eustachian tubal function is a tympanoplasty.”


Eustachian tube function is nonetheless important to tympanic membrane grafting success. Status of the contralateral ear often predicts the eustachian tubal capacity of the involved ear. Apparent current eustachian tubal dysfunction may be a consequence of active infections unilaterally or the aftermath of a lifetime of chronic otitis media. Tympanoplasty is not contraindicated. Postoperatively, when the ear is restored to a more normal state, its eustachian tubal function may also be restored. In the difficult situation of tracheostomy in which eustachian tube function is compromised or when effusion or retraction affects the successful graft, the ear can be ventilated in the office. Ventilation tubes should not be placed in tympanic membrane grafts because they promptly extrude. Tube placement can be performed in the first month after the procedure in the office because the tympanic membrane is still anesthetic.


An atelectatic ear should not preclude tympanoplasty. Rather, it is a perfect indication for cartilage tympanoplasty.






BASIC TECHNICAL PRINCIPLES


The basic surgical principles we all learn as surgical interns are as important here as ever when the operating microscope is introduced as a surgical tool.



Infection Control


Chronic ear surgery is clean-contaminated or contaminated; 90% of otologic wounds are colonized at the time of surgery. The general surgical principle of infection control seeks to minimize colony counts so that host defense mechanisms are not overwhelmed. Whether or not surgeons can accomplish this in ear surgery is highly debated. Otologists seeking higher graft take rates and fewer complications often resort to prophylactic antibiotics as a “protective umbrella.”


In the only study of statistical power on this subject, Jackson23 concluded that prophylactic antibiotics are harmless, but useless. In common uncomplicated tympanoplasty, antimicrobial prophylaxis is unwarranted. An indication for prophylaxis exists in the draining ear, which, intuitively, has a high postinfection rate with graft failure. Despite this fact, no protocol exists to prevent such an outcome. This is an ideal indication for intraoperative irrigation, yet ototoxicity and medicolegal concerns have impeded human study design to address this issue.


There are indications for antimicrobial prophylaxis in ear surgery. Violation of the dural integrity with or without cerebrospinal fluid leakage, violation of the labyrinth, acknowledged aseptic technique breaks, only hearing ears, and implantation of indwelling devices such as cochlear implants all are valid indications.


“The secret to pollution is dilution.” Aggressive irrigation throughout the procedure theoretically clears devitalized debris and clots, and is thought to reduce colony counts. Normal saline is used. The surgical preparation is described in the section on technique.


Jun 14, 2016 | Posted by in OTOLARYNGOLOGY | Comments Off on Tympanoplasty-Undersurface Graft Technique: Postauricular Approach
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