Perioperative neurocognitive disorders in elderly orthopedic surgery: from mechanistic insights to risk prediction and multimodal integrated care

Background Perioperative neurocognitive disorders (PND) encompass pre-existing neurocognitive disorder, postoperative delirium (POD), delayed neurocognitive recovery, and postoperative neurocognitive disorder. Older orthopedic patients are vulnerable, but diagnostic and population heterogeneity complicate interpretation. Methods This narrative review critically synthesizes epidemiological, mechanistic, prediction, and intervention evidence, distinguishing formal diagnoses from screening-score changes and orthopedic-specific from transferable perioperative studies. Findings Multicomponent delirium prevention and coordinated perioperative assessment and recovery support provide the strongest clinical foundation. REGAIN, ENGAGES, the multicenter ketamine trial, and the minocycline trial were neutral for their relevant delirium or cognitive prevention outcomes. Signals from smaller studies of dexmedetomidine, peripheral nerve blocks such as the pericapsular nerve group (PENG) block, intranasal insulin, transcutaneous electrical acupoint stimulation (TEAS), repetitive transcranial magnetic stimulation (rTMS), and specific probiotic formulations require replication and safety assessment. Observational hemodynamic and biomarker findings do not establish preventive efficacy. Conclusion Care should combine guideline-supported delirium prevention with individualized supportive measures. Research priorities include standardized neurocognitive diagnosis, externally validated prediction models, and multicenter orthopedic trials that measure cognition, function, and harms.