AbstractBackground Autologous bone flap preservation following decompressive craniectomy (DC) is routinely performed using either subcutaneous or cryogenic preservation. Despite widespread use, comparative effectiveness data remains conflicting, and the biological relevance of these preservation strategies incompletely defined. Objective To compare clinical outcomes associated with subcutaneous versus cryogenic preservation of autologous bone flaps following DC using systematic review and meta-analysis, stratified by study design. Methods PubMed, Embase, MEDLINE, and Cochrane Library were searched in accordance with PRISMA guidelines to identify randomised and observational studies comparing subcutaneous and cryogenic preservation in adults undergoing cranioplasty post-DC. Primary outcomes were surgical site infection (SSI), revision surgery, and bone flap resorption. Secondary outcomes included intracranial haematoma, length of hospital stay, and timing of cranioplasty. Random-effects meta-analyses were performed, with predefined stratification by randomised versus non-randomised study design. Risk of bias was assessed using RoB 2 and ROBINS-I. Certainty of evidence was evaluated using GRADE. A cost analysis from the UK NHS perspective was performed using revision surgery rates derived from randomised data. Results Seven studies encompassing 811 patients (337 subcutaneous; 474 cryogenic) were included. SSI occurred in 8.6% of subcutaneous and 11.6% of cryogenic patients, with no significant difference in pooled analysis (RR 0.55, 95% CI 0.22–1.34; P = 0.19). Stratified analysis showed a significantly lower SSI risk with subcutaneous preservation in randomised controlled trials (RCTs). Clinical bone flap resorption occurred in 14.7% of subcutaneous and 15.6% of cryogenic patients (RR 0.98, 95% CI 0.70–1.38; P = 0.91). Radiological bone flap resorption was associated with a non-significant trend favouring subcutaneous preservation (mean difference -0.38 mm, 95% CI -0.80–0.04; P = 0.08). Revision surgery occurred in 11.2% of subcutaneous and 11.8% of cryogenic cases (RR 0.92, 95% CI 0.33–2.50; P = 0.86), but was significantly lower with subcutaneous preservation in RCTs. Mortality and secondary outcomes did not differ between strategies. Observational studies were judged to have serious risk of bias, with moderate certainty for RCT-derived outcomes. Subcutaneous preservation was associated with an absolute reduction in revision surgery, corresponding to a number needed to treat of 11. Conclusion Subcutaneous and cryogenic bone flap preservation strategies yielded comparable outcomes in routine clinical practice. However, randomised evidence suggests a potential clinical advantage of subcutaneous preservation for infection-related outcomes and revision surgery, which is biologically plausible but not directly measured in the included studies, supporting the need for further adequately powered, biologically informed randomised trials.
Thamilmaran et al. (Thu,) studied this question.