# Optimal time between decompressive craniectomy and cranioplasty to reduce the risk of complications: A retrospective study

## TL;DR

This study finds that waiting about 122 days after a skull surgery before doing a follow-up procedure may reduce complications.

## Contribution

The study identifies a specific timing cut-off (day 122.5) for cranioplasty to reduce complications, which is novel in this clinical context.

## Key findings

- A delay of about 122 days between surgeries is associated with fewer complications.
- No significant risk factors for complications were found except for timing.
- CART analysis identified day 122.5 as the optimal cut-off for reducing complications.

## Abstract

Cranioplasty (CP) is performed after decompressive craniectomy (DC), with complication rates of 15-40%. Risk factors and ideal timing for CP are unclear. This study investigates risk factors for complications after CP and the best time to perform a CP. This retrospective single-center study includes patients admitted to the neurosurgical department of the University Hospital Zurich between 01.2013 and 05.2023, who underwent a CP following a supratentorial DC. Demographics, comorbidities, indication for the DC, material used, complications, time between DC, CP and onset of complication were collected. The investigated complications are infections, bleeding, bone flap resorption or others requiring surgery. A multivariable logistic regression was performed to identify risk factors for the occurrence of complications. A Classification and Regression Tree (CART) was performed to identify the best time for CP. The result was tested with a Cox regression and a ROC analysis. Overall, 141 patients were included, of whom 39% (n=55) developed a complication. No difference in sex, age, comorbidities, DC-indication, material used was found, except for a trend for CP-time (shorter time for patients with vs without complication, 84±44 vs 102±70 days, p=0.065). In the CART analysis, day 122.5 was the best time cut-off for reducing complications (sensitivity 87%). In our case-series, we could not identify risk factors for complications after CP, except possibly for CP-timing. A longer time between DC and CP seems to be associated with less complications, with day 122.5 as the cut-off time.

The online version contains supplementary material available at 10.1007/s10143-025-03993-1.