Mid-term outcomes of mastoid obliteration with biological hydroxyapatite versus bioglass: a radiological and clinical study

Purpose: Radiological assessment of osseointegration of mastoid grafts: biological hydroxyapatite (Bio-Oss®) (BHA) versus bioglass S53P4 (Bonalive®) (BG).

Methods: Retrospective (10 ± 4 months post-surgery) monocentric high resolution computed tomography (CT) scan assessment (November 2018 and October 2020) by two independent radiologists (R1, R2), blinded to patient allocation. All patients who had undergone a total mastoid obliteration were eligible. Excluded: complications namely otological acute or chronic infections, unbalanced metabolic disease, long-term cortico-steroid therapy, auto-immune disease, history of allergy to grafting materials and post-surgery CT scan in other centers (n = 8).

Primary outcomes: the ratio between two regions of interests (ROI) (graft to otic capsule).

Secondary outcomes: resorption of mastoid grafts and assessment of clinical tolerance.

Results: Included 21 patients (mean age: 29 ± 21 years; 5 females, 16 males). Significantly higher osseointegration for BHA vs. BG (R1 p = 0.043; R2 p = 0.004); almost perfect inter-reader agreement k = 0.922). The ROI ratios for BHA and BG to that of the otic capsule were 0.57 ± 0.11 (R1) and 0.59 ± 0.14 (R2); 0.43 ± 0.11 (R1) and 0.43 ± 0.08 (R2), respectively. Density increased significantly by 399 ± 261 Hounsfield units (HU) (p = 0.008) and decreased by 464 ± 161 HU (p < 0.001) for BHA vs. BG. Resorption rates were 24.1 ± 21.0% and 66.7 ± 15.1% (p = 0.076), respectively. No significant difference in clinical tolerance was observed.

Conclusion: Post-operative CT scan of mastoid obliteration seems reliable in assessment of biomaterial graft's mid-term feasibility and stability: BHA seems to provide a more optimal osseointegration versus BG with no significant differences in graft resorption and clinical tolerance.