Chapter 11 Tympanoplasty—Undersurface Graft Technique
Many otologic surgeons prefer placing connective tissue grafts medial to the tympanic membrane remnant. This graft placement can be accomplished through either a transcanal or a postauricular approach. This chapter describes in detail the transcanal technique and discusses our rationale for favoring it.
If the canal is of adequate size, this technique is suitable for any tympanic membrane perforation in which tympanoplasty is indicated, regardless of size or location. If the canal is not large enough to accommodate a 5 mm or larger ear speculum, however, this procedure may not be technically feasible. The usual indications for closure of tympanic membrane perforations are to reduce the incidence of middle ear infections and to improve hearing. Not every perforation needs to be or should be closed, however. Each patient must be evaluated on the basis of what would be best for that individual. An elderly or debilitated patient with an asymptomatic perforation or a patient for whom the ear under evaluation is the only hearing ear is usually not a good surgical candidate. In the case of a young child who developed a perforation from a ventilation tube that was initially inserted because the child could not ventilate the ear, it would be unwise to repair the tympanic membrane until it is apparent that eustachian tube function has significantly improved, to avoid the pathologic process repeating itself.
There is no infallible test of tubal function, but it is reasonable to assume that if the patient can autoinflate by the Valsalva maneuver preoperatively, he or she would be able to ventilate the ear by this method, if necessary, postoperatively. Consequently, the patient is instructed in this procedure before surgery.
In transcanal tympanoplasty using the underlay technique, the grafting material may be any type of autogenous connective tissue, such as vein, fascia, or perichondrium. In 1957, Shea,1 using vein, was the first to use the underlay grafting technique. Tabb,2 Austin and Shea,3 and others soon recognized the superiority of this method over onlay skin grafting and followed Shea’s lead. The use of fascia as an underlay graft was first reported by Storrs.4 Tragal perichondrium was first used in tympanoplasty as an onlay graft by Goodhill and associates,5 and it is the material we prefer. It is in the immediate surgical field, is extremely durable, and is very easy to handle when pressed. Vein also is easy to position and, if large enough (as from the antecubital fossa), can be used to repair perforations of any size. Our primary objection to the use of vein grafts is that in the event of a serious future illness, the large vein could be an important means of administering parenteral medications.
Temporalis fascia, its overlying areolar tissue, or even scar tissue from the vicinity of a previous postauricular incision can be used with the transcanal undersurface technique, but it is not as easy to handle as vein or perichondrium. Pressing the fascia in a vein or fascia press makes it much more manageable by eliminating the tenacious loose strands, and at the same time preventing the stiffness that occurs with drying. We do not recommend pressing the vein for tympanoplasty (as done in stapedectomy) because it results in excessive thinning. Instead, we trim away the adventitia and stretch the vessel between the blades of a vein scissors before opening it.
Perioperative antibiotics are rarely used. The hair and skin surrounding the ear are cleansed with 70% alcohol. The hair is not shaved unless fascia is to be taken, but it is combed away from the ear and sprayed with liquid spray bandage. The head is secured with tape in a standard foam headrest in the position most conducive to good visibility for the surgeon; this usually involves tilting the head back and the chin up slightly (Fig. 11-1