Collapse Ratio and Operative Duration as Key Predictors of Postoperative Complications Following Cranioplasty

Background Cranioplasty (CP) after decompressive craniectomy (DC) restores cranial integrity, cerebral blood flow, and CSF dynamics, often improving neurological recovery. However, postoperative complications remain a concern, with debate traditionally centered on CP timing. Emerging evidence suggests that radiological parameters such as collapse ratio, the degree of parenchymal depression at the craniectomy site, and operative duration, a marker of intraoperative complexity, may better predict outcomes. This study explored these factors in relation to post-CP complications. Methodology We retrospectively reviewed 100 patients (≥16 years) who underwent CP following DC at a tertiary neurosurgical center in Nepal (2018-2024). Patients with prior CP, inadequate imaging, or intracranial tumors were excluded. The collapse ratio was measured on preoperative CT using 3D-Slicer software, and the operative duration and the DC-CP interval were recorded. Postoperative outcomes within six months, including seizures, infection, hemorrhage, hydrocephalus, and revision surgery, were documented. Data were analyzed using t-tests, chi-square/Fisher's exact tests, logistic regression, and receiver operating characteristic (ROC) curves. Results Complications occurred in seven (7%) patients, all manifesting as postoperative epilepsy. The complication group had a higher mean collapse ratio (0.78 ± 0.16 vs. 0.36 ± 0.14, p < 0.001) and a longer operative duration (139.7 ± 19.2 vs. 115.1 ± 14.5 minutes, p < 0.001). Logistic regression identified collapse ratio (OR 1.87, p = 0.001) and operative duration (OR 1.68, p = 0.001) as independent predictors, whereas timing was not significant. ROC analysis showed excellent predictive ability for the collapse ratio (area under the curve (AUC) = 0.812) and moderate predictive ability for operative duration (AUC = 0.702). Conclusions A higher collapse ratio and longer operative duration independently predict early post-CP complications, whereas fixed timing thresholds provide limited prognostic value. Incorporating these measures into preoperative assessment may enhance surgical planning and risk stratification, particularly in resource-limited settings.