Comparison between the different types of heterologous materials used in cranioplasty: A systematic review of the literature

INTRODUCTION: The choice of heterologous materials for cranioplasty after decompressive craniectomy is still difficult. The aim of this study is to examine the association between material of choice and related complications to suggest the best treatment option. eViDeNce acQuisiTioN: a systematic review was performed for articles reporting cranioplasty comparing the following heterologous implants: titanium, poli-methyl-methacrylate (PMMa), polyetheretherketone (PeeK) and hydroxyapatite (Ha). extracted data included implant materials and incidence of the most frequent complications. EVIDENCE SYNTHESIS: The final selection resulted in 106 papers but according to our rules only 27 studies were included in the final analysis. among a total of 1688 custom-made prosthesis implanted, 649 were titanium (38.49%), 298 PMMa (17.56%), 233 PeeK (13.82%), and 508 were Ha (30.13%). a total of 348 complications were recorded out of 1688 reported patients (20.64%). in the titanium group, 139 complications were recorded (21.42%); in the PMMa group 57 (19.26%), in the PeeK group 49 (21.03%) and in the Ha group 103 (20.3%). if we examine a summary of the reported complications clearly related to cranioplasty (postoperative infections, fractures and prosthesis displacement) versus type of material in multicentric and prospective studies we can see how Ha group patients have less reported infections and cranioplasty explantation after infections than PMMa, PeeK and titanium. on the contrary Ha patients seem to have a higher number of prosthesis displacement again if compared with the other materials. since these data are not derived from a statistically correct analysis they should be used only to help to differentiate the properties of the various heterologous cranioplasties. CONCLUSIONS: The ideal material for all heterologous cranioplasty has not yet been identified. The choice of material should be based on the clinical data of patients, such as the craniectomy size, presence of seizures, possibility of recovery, good long-term outcome associated with a cost analysis.