Discussion

Surgical treatment of chronic otitis media aims to provide the patient with a dry ear and to protect their hearing. Many surgical techniques have been described for the treatment of chronic otitis media. Canal wall down mastoidectomy is a surgical procedure that provides successful outcomes, especially in cases with extensive cholesteatoma. In this surgical approach, a large cavity is formed in the mastoid region.^{Reference Kim, Lim, Oh, Kim and Chang1} Many cavity obliteration methods have been described, but these may result in complications in the mastoid cavity.^{Reference Roberson, Mason and Stidham5,Reference Mehta and Harris6} Obliteration has some other negative consequences, including delays in the detection of relapse. One of the rare complications of canal wall down mastoidectomy is deformities in the auricle post-operatively.^{Reference van Hövell Tot Westerflier, van Wijk and Kon7,Reference Hong, Arseneault and Makki8}

Although the auricle cartilage touches the skull base, it is not physically connected to it.^{Reference Guyuron and DeLuca9} Stability of the auricle in the mastoid region is maintained by skin continuity, soft tissues, and the anterior, superior and posterior external auricular muscles.^{Reference Guyuron and DeLuca9} The posterior auricular muscle enables adduction of the auricle, preventing its outward protrusion. Dysfunction of this muscle can therefore cause protrusion.^{Reference Smith10} During the post-auricular incision, the skin, subcutaneous connective tissue and posterior auricular muscle are cut.^{Reference Hong, Arseneault and Makki8} In addition, the integrity of the mastoid bone, which is supported by a large portion of these structures, is broken, and a cavity is formed. In our study, disruption of the integrity of these structures was found to cause deformity in the auricle and a narrowing of the auriculo-cephalic angle over the long term.

van Hövell Tot Westerflier et al.^{Reference van Hövell Tot Westerflier, van Wijk and Kon7} reported that soft tissues were displaced into the cavity formed after mastoidectomy; they named this deformity ‘sunken ear’. In their study, nine adult patients with sunken ear deformities were retrospectively analysed, and it was revealed that all the patients had previously undergone canal wall down mastoidectomy surgery more than one year previously. All nine patients subsequently underwent reconstruction with grafts taken from costal cartilage. Similarly, in our study, we detected an asymmetric auriculo-cephalic angle reduction at the middle part of the auricle.

Low-set ear deformity was defined in 10 patients who had undergone mastoid surgery for chronic suppurative otitis media.^{Reference Ali4} Seven of these patients had undergone canal wall down mastoidectomy, while three had undergone canal wall up mastoidectomy. Although seven patients were aware of this potential complication, two stated that they were dissatisfied with the outcome.^{Reference Ali4} Potential predisposing factors include dissection of the auricle and ear canal, and lowering of the posterior bony canal wall. In our study, we found that canal wall down mastoidectomies performed in 34 patients resulted in significant narrowing of the auriculo-cephalic angle and caused deformities.

Hong et al.^{Reference Hong, Arseneault and Makki8} reported that tympanoplasty performed via post-auricular incisions in 19 paediatric patients did not change the auriculo-cephalic angle. In another study, it was found that tympanoplasty performed with post-auricular incision did not change the auriculo-cephalic angle in 35 adult patients.^{Reference Akgül, Özgür, Yemiş, Özdemir, Ünal and Çelebi11} Patients who underwent canal wall down mastoidectomies were not included in these studies.^{Reference Hong, Arseneault and Makki8,Reference Akgül, Özgür, Yemiş, Özdemir, Ünal and Çelebi11} It was found that the auriculo-cephalic angles did not change after interventions where the mastoid bone was preserved. Soft tissue damage is not effective in changing the ear position, but, if mastoidectomy is performed, there is a possibility that the tissues will be buried in the cavity, in which case the ear position may change.

Kim^{Reference Kim12} found that the position of the auricle returned to its initial position two months after tympanoplasty and canal wall up mastoidectomy, and four months after canal wall down mastoidectomy. However, the follow-up period was six months post-surgery in their study. In the current study, patients who underwent canal wall down mastoidectomy were evaluated one year after the initial surgery. The position of the auricle was found to be approaching the mastoid bone at this longer-term follow up.

In a normal ear, the auriculo-cephalic angle is 25–30 degrees and the distance of the auricle to the mastoid is 15–20 mm. Okur et al. measured the auricle–mastoid mean distance as 16.9 mm.^{Reference Okur, Kahveci, Miman, Yıldız, Ayçiçek and Altuntaş13} The helix upper-tip to scalp distance was measured as 10–12 mm.^{Reference Graham, Bezuhly and Hong14} In our study, the distance between the middle part of the auricle and the mastoid was found to be 19.03 mm pre-operatively and 16.29 mm post-operatively, while the distance between the upper part of the helix and the skull was 14.18 mm pre-operatively and 13.15 mm post-operatively. Auricular deformity and the auriculo-cephalic angle reductions after canal wall down mastoidectomy cause dissatisfaction in some patients.^{Reference Ali4,Reference van Hövell Tot Westerflier, van Wijk and Kon7} Informing patients of this complication before surgery may help them to better accept the outcome.