Initial Dead Space and Multiplicity of Bone Flap as Strong Risk Factors for Bone Flap Resorption after Cranioplasty for Traumatic Brain Injury

OBJECTIVE: Bone flap resorption (BFR) is a complication of cranioplasty (CP) that increases the risk of brain damage and can cause cosmetic defects. In this study, the risk factors for BFR were examined to improve the prognosis of patients after CP for traumatic brain injury (TBI). METHODS: This study was conducted in 80 patients with TBI who underwent decompressive craniectomy and CP with an autologous bone graft between August 2006 and August 2017. BFR was defined as a >0.1 ratio of the difference between the initial bone flap area and the last bone flap area to the craniectomy size and a <0.5 ratio of the last bone flap thickness to the bone thickness of the contralateral region on computed tomography scans and plain skull radiographs. The patients were divided into the BFR and non-BFR groups, and medical data were compared between the two groups. RESULTS: Among the 80 patients, 22 (27.5%) were diagnosed as having BFR after CP. The earliest cases of BFR occurred at 57 days after CP, and the latest BFR cases occurred at 3,677 days after CP. Using multivariate logistic regression analyses, the initial dead space size (odds ratio [OR], 1.002; 95% confidence interval [CI], 1.001–1.004; p=0.006) and multiplicity of the bone flap (OR, 3.058; 95% CI, 1.021–9.164; p=0.046) were found to be risk factors for BFR. CONCLUSION: The risk factors for BFR in this study were the initial dead space size and multiplicity of the bone flap.