Human factors and surgical never events: A two-phase updated systematic review applying the SHEEP model

Surgical never events, including wrong-site surgery, retained foreign objects, and wrong implants or prostheses, persist globally despite successive patient safety frameworks. Human factors are consistently identified as contributors, yet prior systematic reviews have not applied a structured health care-specific analytical taxonomy to this evidence base. This two-phase updated systematic review searched MEDLINE, CINAHL, and specialist journals from inception to December 2025, identifying 39 studies. Human factors findings were mapped against the five domains of the SHEEP model (Systems, Human Interaction, Equipment, Environment, Personal). Human Interaction and Systems were the dominant domains, co-occurring in the majority of studies. Equipment was the least prevalent domain, indicating that technology remains an adjunct rather than a primary prevention strategy. Sustained reduction in surgical never events requires investment in checklist fidelity, speaking-up culture, and organisational responses that prioritise learning over blame rather than reliance on guidance alone.Summary of Major ThemeSurgical never events, including wrong-site surgery, retained foreign objects, and wrong implants or prostheses, represent a persistent patient safety challenge despite successive national and international policy frameworks. Human factors are consistently identified as contributory across the published literature, yet no prior systematic review has applied a structured health care-specific analytical taxonomy to this evidence base. This two-phase updated systematic review applied the Systems, Human Interaction, Equipment, Environment and Personal (SHEEP) model across 39 included studies spanning inception to December 2025, producing domain-level frequency data unavailable from prior narrative reviews. Human Interaction and Systems were identified as the dominant domains, co-occurring in 77% of studies, confirming that never events arise from the simultaneous breakdown of communication and organisational safety systems rather than from isolated individual failures. Equipment was the least prevalent domain, indicating that technology-based prevention strategies remain an adjunct to cultural and systems change.