The «SPA-CE» classification for glenoid bone loss in reverse shoulder arthroplasty: a CT-based analysis of 211 shoulders.

BACKGROUND: Glenoid bone loss represents a major challenge in primary reverse shoulder arthroplasty (RSA), directly influencing implant fixation, positioning, and reconstructive strategy. Existing classification systems describe glenoid morphology but do not provide a unified framework for treatment-oriented decision-making. The SPA-CE classification was developed as a CT-based system integrating defect depth, location, and version abnormality. METHODS: A retrospective analysis of 211 consecutive primary RSA procedures was performed. Preoperative CT scans were used to classify glenoid morphology according to the SPA-CE system and the Walch classification. Reconstructive strategies were analyzed in relation to SPA-CE types. The distribution of morphologic patterns and their association with surgical techniques and underlying diagnosis were assessed. RESULTS: The most common SPA-CE pattern was simple central (SC), observed in 62.1% of cases. Overall, simple (S) defects predominated (75.4%), whereas plastic (P) defects accounted for 24.2% and advanced (A) defects were rare (0.5%). Defects managed without structural reconstruction (SC and SEI) accounted for 73.9% of shoulders, whereas 1.4% required version correction without lateralization (SEII), 24.2% required lateralization (plastic types), and 0.5% required patient-specific reconstruction. A consistent relationship was observed between SPA-CE types and reconstructive strategies. In contrast, substantial variability in SPA-CE patterns was identified within individual Walch groups, particularly in Walch B2 glenoids. Underlying diagnosis influenced defect morphology: post-traumatic conditions, fractures, and rotator cuff tears were predominantly associated with SC defects, whereas osteoarthritis demonstrated the widest distribution of SPA-CE patterns, including complex and reconstructively demanding defects. CONCLUSION: The SPA-CE classification provides a structured, CT-based, and treatment-oriented framework for the assessment of glenoid bone loss in RSA. It demonstrates a consistent relationship with reconstructive strategies and may improve preoperative planning and surgical decision-making.