Factors Influencing the Use of Patient-Specific Instrumentation (PSI) in Shoulder Arthroplasty: A Single-Centre Study.

Background Accurate component placement is vital for shoulder arthroplasty success, with poor positioning linked to a range of clinical complications. This study aims to identify which patient, anatomical and surgical factors influenced the adoption of patient-specific instrumentation (PSI) for glenoid component placement. These included patient demographics, implant type, glenoid version and inclination, glenoid dimensions, use of augmentation, and surgeon-related factors. Methodology A retrospective decision-analysis study of 191 shoulder arthroplasty cases (reverse and anatomical) conducted between 2021 and 2024 at a single NHS trust. Preoperative imaging protocols, component planning, degree of deformity and intraoperative decision-making were examined. The primary outcome was the association between anatomical factors and PSI use. Statistical analysis performed using SPSS v16 (SPSS Inc., Chicago, IL). Results PSI use was strongly associated with increased glenoid retroversion (Cramér's V = 0.37, P < 0.001) and superior inclination (Cramér's V = 0.30, P = 0.001), and moderately associated with the use of medium and large glenoid augments (Cramér's V = 0.33, P < 0.001). No significant association was observed between PSI use and patient age, sex, surgical side, glenoid anteroposterior width, or vault depth (all Cramér's V < 0.15). Conclusions PSI is primarily adopted in cases with complex glenoid deformities. This study analyses decision-making patterns rather than clinical effectiveness. This may help inform future work towards more consistent PSI selection.