Volumetric changes in the bone flap at one year follow up in patients undergoing craniotomy

Although bone resorption has been extensively reported following craniectomy, bone resorption and fusion rates following craniotomy remains unexplored. The aim of the present study was to conduct a volumetric assessment of craniotomy resorption and fusion rates at one year following the index surgery. Adult patients who had a computed tomography scan immediately after craniotomy and at one year follow up were included in the study. Various baseline demographic variables and reason for craniotomy, method of fixation, and post-operative complications were recorded. 3D-Slicer was used to demarcate the bone flap segments - central flap, flap edge, kerf, burr-holes, and periphery and the volumes of both computed tomography scans were compared. 34 patients with a mean age of 59.29 ± 17.77 years were included in the study. Tumors were the most common indication of craniotomy. Four patients reported significant pain related to their hardware and one patient reported postoperative cerebrospinal fluid leakage. The mean follow-up period was 357.4 ± 62.67 days. An overall increase in the bone volume was observed in the kerf (+ 8.46%) and burr-hole regions (+ 12.92%) while the central flap (-1.55%), flap edge (-4.48%) and periphery (-3.5%) depicted bone resorption. The increase in volume in the kerf space represents at an average less than 10% bridging of the gap and is far from fusion. On multivariable regression, a negative correlation was observed between the change in peripheral bone volume and patient age and a positive correlation between male sex and flap edge volume change. Cranial flap bone loss in patients who underwent craniotomy was quantified in this study while an overall increase in bone volume was observed in the regions of the kerf and the burr-holes one-year postoperatively, less than 10% of the kerf space was bridged by bone. Clinical Trial Number: Not Applicable.