Healthcare organizations operate within increasingly hostile cyber environments while simultaneously depending on legacy medical devices and outdated operating systems. The coexistence of modern cyber threats and legacy clinical infrastructure creates a structural security paradox: hospitals must preserve device compatibility and patient safety while modernizing security architectures to withstand sophisticated lateral movement, ransomware, and advanced persistent threats. This study develops a comprehensive theoretical and evaluative framework examining the integration of Zero-Trust Architecture (ZTA) principles into hospital clinical workstations through the adoption of Windows 11, particularly in environments characterized by legacy medical operating systems.

Drawing upon foundational zero-trust theory, national standards, lateral movement detection research, healthcare incident analyses, and empirical threat intelligence reports, the article synthesizes architectural, operational, and governance perspectives. The research evaluates how Windows 11 security capabilities-when aligned with NIST SP 800-207 zero-trust principles-can mitigate risks associated with unsupported legacy systems widely prevalent in healthcare environments. The analysis contextualizes the WannaCry incident within systemic perimeter-security failure and explores contemporary threat patterns affecting healthcare providers.

The findings demonstrate that zero-trust adoption, when embedded within endpoint modernization, identity-centric validation, distributed access enforcement, AI-enhanced monitoring, and micro-segmentation strategies, significantly reduces lateral movement potential and containment failure. However, modernization must be strategically phased to preserve device interoperability and regulatory compliance. The study further identifies critical governance, operational, and socio-technical challenges, including medical device certification constraints, cost structures, cultural resistance, and integration complexity.

The article concludes that bridging zero-trust security and legacy medical devices requires a hybrid transition model-combining containment-based isolation, progressive operating system modernization, AI-enabled validation, and distributed trust enforcement-to achieve sustainable resilience in hospital clinical environments.