This monocentric observational cohort study compares conventional instrumentation, patient-specific instrumentation, and augmented reality navigation in reverse total shoulder arthroplasty. The primary objective is to assess the accuracy of glenoid component positioning based on postoperative CT data. Secondary objectives include evaluation of functional outcomes and clinical performance at mid-term follow-up. Patients who underwent surgery between 2021 and 2024 are followed up clinically at 2 years postoperatively.

This study investigates the accuracy and clinical relevance of different planning and implementation techniques in reverse total shoulder arthroplasty. Patients treated at a single orthopedic center between 2021 and 2024 were included. Three established surgical approaches were analyzed: conventional instrumentation, patient-specific instrumentation, and augmented reality navigation.

Initial data collection included retrospective and prospective assessment of preoperative planning parameters and their intraoperative implementation. Postoperative evaluation included low-dose CT imaging to assess glenoid component positioning accuracy.

The current phase of the study focuses on long-term clinical outcomes, with a standardized 2-year follow-up including clinical examination and validated functional outcome scores. No additional imaging is performed as part of the follow-up phase.

Patients were not randomized; group allocation reflects the surgical technique used at the time of treatment.

Inclusion Criteria:

• Age ≥ 18 years
• Reverse total shoulder arthroplasty performed between 2021 and 2024
• Available preoperative imaging and planning (X-ray and/or CT)
• Available postoperative CT imaging
• Written informed consent

Exclusion Criteria:

• Major perioperative complications not related to the shoulder procedure affecting outcomes
• Incomplete imaging or clinical data

Patients who underwent reverse total shoulder arthroplasty at a single tertiary orthopedic center (Ordensklinikum Linz - Barmherzige Schwestern, Austria) between 2021 and 2024. The study population includes individuals treated using conventional instrumentation, patient-specific instrumentation, or augmented reality navigation as part of routine clinical care. Only patients with available preoperative planning data and postoperative CT imaging, as well as those eligible for clinical follow-up, were included. All participants are invited for a standardized clinical and functional assessment at 2 years postoperatively.