Assessing cranioplasty outcomes: Implant types and cerebrospinal fluid shunts

Introduction: Cranioplasty aims to repair the cranium, typically after injury or surgery. It has a high failure rate (10%-20%). Additionally, hydrocephalus can occur concurrently, either due to the primary injury or as a surgical complication. The treatment of hydrocephalus requires the insertion of a cerebrospinal fluid shunt. The optimal timing for cerebrospinal shunting and the optimal cranioplasty material and implant type remain undetermined. Our study seeks to assess the impact of these factors on patient outcomes.

Methods: 433 cranioplasty procedures conducted to 379 patients were retrospectively identified from the Cambridge University Hospital and Oulu University Hospital patient databases. The primary outcome was implant removal and the secondary outcome occurence of any complication. Titanium and fiber-reinforced composite-bioactive glass (FRC-BG) were categorized as onlay-type, and the other materials as inlay-type.

Results: The median follow-up time was 9 months (IQR 21,7), the mean age was 43 years (SD 17,6) and 274/379 (63%) patients were male. The mean ASA grade was 2,5 (SD 0,67). Out of 433 cases 68 had cerebrospinal fluid shunts, 64 (94%) of which were inserted pre- or post-cranioplasty. The presence of a CSF shunt increased the risk of implant removal (OR 2,73, 95% CI) and overall complications (OR 2,64, 95% CI).
Eighty (19%) of the implants were autografts, 212 (49%) titanium, 79 (16%) FRC-BG, and 56 (13%) plastic. Although complication rates were different between implant types (onlay vs. inlay), there was no difference in implant survival. Higher ASA grade was associated with implant failure (OR 1,99, 95% CI).

Conclusion : Patients with CSF shunts had higher implant failure rates and shorter implant survival. Pre-cranioplasty shunted patients had more cranioplasty infections (26% vs. 14%) and post-operative haematomas (9% vs. 4%) than those shunted post-cranioplasty. Nevertheless, implant failure rates were similar between those who had been shunted pre- and post-cranioplasty. Although outcomes were similar between implant types, the complication profiles vary. It may be prudent to delay shunting until after cranioplasty whenever possible, and to consider individual patient characteristics in implant material and type choices.