Canalplasty Technique

No specific medical therapies have been shown to definitively improve exostoses or other causes of acquired external auditory canal (EAC) stenosis. Otitis externa may develop in the presence of acquired EAC stenosis, a condition requiring treatment with topical or systemic antimicrobials. For hearing loss associated with EAC occlusion, hearing aids may prove beneficial. In the setting of EAC obstructions, however, hearing aids may additionally cause inflammation that may exacerbate the condition and may be uncomfortable for the patient. ^{[10, 11]}

The goal of surgery is simply to establish an open external auditory canal, which may require addressing the cartilaginous or bony portions of the EAC. Preoperative planning should address which, if not both, are required.

Patients undergoing canalplasty who also have cosmetic deformities of the external ear should undergo any cosmetic procedures first, as a postauricular incision may affect blood supply to future planned repairs.

If acquired stenosis is the result of canal fibrosis, the lateral epithelial border of the TM may be included in the stenosis.

Several techniques for canalplasty have been advocated. For external auditory exostoses, osteotomes and otologic drills have both been used to remove excess bone. ^[12]  Typically, a postauricular approach is used with an endaural incision for exostoses and medial canal fibrosis. An endaural incision alone may be appropriate for an osteoma, as they often have a stalk that facilitates easier removal.

The planned incision areas in the postauricular sulcus and EAC are infiltrated with local anesthetic medication, typically 1% lidocaine with 1:100,000 parts epinephrine. The ear is then prepared and draped in a sterile manner.

The endaural incision is first made in the EAC as far medial as allowable given the constraints of the obstruction. A laterally-based vascular strip is developed in the EAC skin. Attention is then directed to the post-auricular area. A post-auricular incision is made approximately 7 mm behind the postauricular sulcus. The auricle is retracted laterally. The incision is then continued through the auricularis posterior muscle and down to temporalis fascia. Periosteum over the mastoid is incised and elevated anteriorly to the external auditory canal. The endaural incision is found from the postauricular approach, and the 2 incisions are joined. The EAC skin is carefully elevated off of the bony EAC and then retracted forward with the auricle.

In external auditory exostosis, the skin overlying the exostosis is elevated with a round knife and elevated toward the tympanic membrane. The exostosis is drilled down using cutting and diamond burrs in a lateral to medial direction. Curettes may be used to augment dissection of bony ledges. Typically, canalplasty for acquired EAC stenosis requires drilling of the anterior bony canal. When using the otologic drill, care must be taken to avoid contact with the ossicular chain, as this can contribute to hearing loss.

Additional care must be taken when drilling anteriorly to avoid penetration into the temporomandibular joint (TMJ). A technique for this portion of the procedure involves drilling away bone superior and inferior to the TMJ first, before carefully removing the buttress of bone overlying the joint. ^[4] If surgery is being performed for medial canal fibrosis, the scar can usually be dissected off of the tympanic membrane (TM), leaving an intact medial layer of the TM. Occasionally, however, a portion of the membrane must be resected and subsequently repaired.

If canalplasty is being performed alone, then after the exostosis is removed, the flap of ear canal skin is placed back in position. If necessary, releasing cuts may be made to allow the flap to rest properly. If insufficient skin is present to cover the defect, a split-thickness skin graft may be required. Out of convenience, the typical donor site is postauricular skin. Other donor sites, however, include the abdomen, leg, or forearm. A dermatome with a 2-inch blade is used with a thickness of 0.005-0.006 inches. Hemostasis is obtained at the donor site with pressure, topical epinephrine, or topical thrombin. The donor site can be dressed with an elastic bandage.

The postauricular incision is then closed in layers and the external auditory canal is packed with Gelfoam. A stent may be placed to assist with adherence of the graft to the EAC.