Allograft bone vs. bioactive glass in rehabilitation of canal wall-down surgery

Canal wall-down (CWD) mastoidectomy creates a radical cavity that modifies the anatomy and physiology of the middle ear, thus preventing it from being self-cleaning and causing epidermal stagnation in the posterior cavities. Canal wall-down tympanomastoidectomy with reconstruction (CWDTwR) can obliterate such radical cavities. The main objective of this study was to compare postoperative results after CWDTwR by using either bone allografts or 45S5 bioactive glass as a filling tissue with an 18-month follow-up. This was a single-center observational trial including all patients undergoing CWDTwR. Patients were divided into two groups according to the filling material used: allograft bone (AB group) or 45S5 bioactive glass (BG group). Clinical monitoring was performed regularly, with control imaging performed at 18 months (CT scan and DW MRI). The two groups were compared with the t test for quantitative variables and the chi square test for qualitative variables (no revision surgery, audiometric results, complications, mastoid obliteration volume). Thirty-two patients underwent CWDTwR between October 2015 and 2018. The mean age was 48 years, and 71.9% (23/32) were men. A total of 46.9% (15/32) of the patients had undergone at least 3 middle-ear surgeries prior to CWDTwR. The most frequent preoperative symptom was otorrhea (100.0%, 32/32), and only 12.5% (4/32) experienced dizziness. Fifteen and 17 patients underwent surgery with bone allografts and 45S5 bioactive glass, respectively. At 18 months post-operation, 53.3% of the patients (8/15) in the AB group presented with recurrent otorrhea versus 5.9% (1/17) of patients in the BG group (p = 0.005). Seventy-eight percent (7/9) of symptomatic patients had undergone revision surgery at 18 months postoperation: 40.0% (6/15) in the AB group and 5.9% (1/17) in the BG group (p = 0.033). One patient's surgery was cancelled due to the COVID-19 pandemic, and one patient refused surgery. The effects of CWDTwR with bone allografts are disappointing in early follow-up, with significant resorption leading to a 40.0% revision surgery rate. 45S5 BG is a simple solution, with preliminary results that are superior to those of AB. However, prospective controlled studies with longer follow-up times are needed to evaluate the value of BG versus other synthetic materials (such as hydroxyapatite) in surgical management of CWDTwR.Trial registration: retrospectively registered.