Heterogeneity in definitions of surgical site infection after cranial surgery limits the validity of research findings in neurosurgery: a systematic review.

Surgical site infections after cranial surgery (SSI-CRAN) are serious adverse events considering the vicinity of the wound to the central nervous system. Variability in outcome definitions can hinder the ability to produce reliable evidence. This systematic review aimed to investigate whether there is variation in SSI-CRAN definitions across studies and its impact on the identification of effective treatments for patients after cranial surgery. Systematic searches of Medline, Embase and Cochrane Central were undertaken. Studies that reported data about SSI-CRAN were included. Our final dataset consisted of 519 studies reporting SSI-CRAN. Subspecialties included were neuro-oncology (n = 103,19.8%), neurotrauma (n = 92,17.7%), paediatric neurosurgery (n = 56,10.8%), functional neurosurgery (n = 52,10.0%), neurovascular (n = 38,7.3%), skull base (n = 37,7.1%), cerebrospinal fluid dynamics (n = 11,2.1%), and general neurosurgical cases (n = 149,28.7%). A hundred and sixty-nine (32.6%) studies reported SSI-CRAN definitions. Twenty-six different indicators for SSI-CRAN were used, with a median of nine (range: one to 16) utilised per study. Only 21 (4.0%) studies considered the varying definitions of SSI-CRAN in their conclusions, indicating that a lack of consistent definitions across studies impacted the ability to draw clear conclusions. There are discrepancies in the definition of SSI-CRAN across the literature. This heterogeneity has hindered the ability to draw conclusions about the effects of interventions, with only 4.0% of authors accounting for this in their findings. It is important to be cautious when reviewing studies that report SSI-CRAN outcomes without acknowledging this heterogeneity, as the validity of their reported evidence may be limited. The implementation of a new core indicator set could support uniform reporting of indicators along with regulation of reported SSI-CRAN outcomes, thereby facilitating more effective evidence synthesis.