Bone Flap Resorption and Its Risk Factors Following Autologous Cranioplasty with Bone Tissue Bank– Stored Grafts

Objective: To classify the severity of bone flap resorption (BFR) following autologous cranioplasty under bone tissue bank storage conditions and to identify potential risk factors by analyzing clinical cases exhibiting postoperative bone resorption. Methods: A retrospective analysis was conducted on clinical data from 61 patients who developed bone flap resorption after autologous cranioplasty performed with bone flaps stored under bone tissue bank conditions. Based on the Oulu Resorption Scale, patients were categorized into four groups: no bone flap resorption (NBFR), mild BFR (MBFR), intermediate BFR (IBFR), and severe BFR (SBFR). Clinical characteristics were compared across these groups. Variables showing statistical significance (p < 0.05) in univariate analyses were subsequently entered into a multivariate ordinal logistic regression model to evaluate their association with the development and severity of BFR. Results: All 61 patients completed follow-up, with a median follow-up duration of 378.0 days (interquartile range: 178.5–605.5 days). By the end of follow-up, 16 patients (26.2%) had developed BFR, including 9 cases (14.8%) of MBFR, 4 cases (6.6%) of IBFR, and 3 cases (4.9%) of SBFR. Univariate analysis revealed that smoking, traumatic brain injury (TBI), number of bone flaps ≥2, cranial defect area >92.11 cm², and bone flaps located in the frontotemporoparietal region were significantly associated with an increased risk of BFR (all p < 0.05). Multivariate ordinal logistic regression analysis identified smoking, TBI, and cranial defect area >92.11 cm² as independent risk factors for BFR, whereas having fewer than two bone flaps served as a protective factor against resorption (all p < 0.05). Conclusion: Autologous cranioplasty using bone flaps preserved under bone tissue bank conditions is associated with a low complication rate. With careful patient selection, it remains a recommended reconstructive option following decompressive craniectomy.