Research Article: A retrospective descriptive study of cranioplasty failure rates and contributing factors in novel 3D printed calcium phosphate implants compared to traditional materials

Date Published: June 17, 2020

Publisher: Springer International Publishing

Author(s): Michael Koller, Daniel Rafter, Gillian Shok, Sean Murphy, Sheena Kiaei, Uzma Samadani.


Failure rates with cranioplasty procedures have driven efforts to improve graft material and reduce reoperation. One promising allograft source is a 3D-printed titanium mesh with calcium phosphate filler. This study evaluated failure rates and pertinent characteristics of these novel 3D-grafts compared to traditional materials.

Sixty patients were retrospectively identified who underwent a cranioplasty between January 2015–December 2017. Specific data points related to graft failure were collected for all surgical admissions, from the primary injury to their most recent. These included, but were not limited to, initial physical exam findings, vitals, comorbid conditions, surgery length, estimated blood loss, incision type, and need for revision. Failure rates of 3D-printed allografts were compared to traditional grafts.

A total of 60 subjects were identified who underwent 71 unique cranioplasty procedures (3D = 13, Synthetic = 12, Autologous = 46). There were 14 total failures, demonstrating a 19.7% overall failure rate. Specifically, 15.4% (n = 2) of 3D, 19.6% (n = 9) of autologous, and 25.0% (n = 3) of synthetic grafts required revision. Patients receiving 3D-grafts had the shortest overall mean surgery times (200.8 ± 54.3 min) and lowest infection rates (7.7%) compared to autologous (210.5 ± 47.9 min | 25.0%) and synthetic models (217.6 ± 77.3 min | 8.7%), though significance was unable to be determined. Tobacco use and trap-door incisions were associated with increased failure rates relative to straight or curved incisions in autologous grafts. Cranioplasties performed less than 3 months after craniectomy appeared to fail more often than those performed at least three months after craniectomy, for the synthetic group.

We concluded that 3D-printed cranioplasty grafts may lead to lower failure rates and shorter surgery times compared to traditional cranioplasty materials in our limited population. 3D-implants hold promise for cranial reconstruction after TBI.

Partial Text

Decompressive craniectomy (DC) is a common neurosurgical intervention in which a large section of the skull is removed in the setting of severe traumatic brain injury (TBI). The resulting skull defect is left open to allow brain tissue to swell past this rigid border, thus mitigating potentially fatal elevations in intracranial pressure [1–3]. Once the underlying pathology has been corrected, the contour of the skull is reconstructed either with the autologous bone flap or a synthetic implant via cranioplasty. This is done for cosmesis as well as to reduce complications from DC including seizure, post-traumatic hydrocephalus, and syndrome of trephined [4–7]. While cranioplasty is a routine and technically straightforward procedure, current data demonstrates failure and complication rates as high as 40% due to infection, hardware exposure, and autologous bone resorption [8–10]. As such, there has been a focus on shorter operating times, optimizing time between craniectomy and cranioplasty, and managing patient comorbidities to improve outcomes [11–13].

Complications from cranioplasty procedures continue to be an important issue despite the procedure’s routine nature. Prior work has investigated the feasibility of utilizing 3D technology for cranioplasty implants [37–41]. A mold fabrication system has been developed that constructs cranioplasty implants with higher cranial index symmetry – matching the cranial defect more accurately – than autologous types [41–44] (Figs. 1 and 2). Other research has assessed these 3D implants using cadavers as proxies, providing insight into the efficiency of the technique and the clinical applications of employing procedures of this genre [45]. The most promising research looked retrospectively at patients undergoing calcium phosphate-based implants with 3D-printed titanium mesh reinforcement [36]. Notably, the need for explantation was found in 7.5% of these patients, who collectively had a previous failure rate of 64% in prior autologous or alloplastic implants. This study, however, did not assess the failure rates between different cranioplasty types, nor did they delve into the factors contributing to these outcomes. While the results from the present study were based on a population size that did not allow for reliable statistical testing, the raw data does provide valuable insight into the promising potential of 3D-printed implants and the elements involved in reducing cranioplasty failures.

Based on the findings from the present study, 3D-printed implants demonstrate potentially favorable failure rates, infection rates, and surgery times compared to autologous and synthetic implants in TBI cranial reconstruction, although statistical significance could not be determined given our limited study population. Further research on the efficacy of 3D implants and their impact on surgical outcomes using larger sample sizes and longer follow-up assessments are warranted.