Genetic and biomechanical determinants of glenoid version: implications for glenoid implant placement in shoulder arthroplasty.

SUMMARY: The universally accepted method of measuring glenoid version to determine proper alignment of the glenoid component during total shoulder arthroplasty does not account for the complex and variable relationship of the glenoid vault with the scapular body. Existing evidence indicates that the glenoid and the scapular body development are controlled by independent genetic and biomechanical factors. This raises the question: How relevant is the relationship of the glenoid face to the scapular body? This review paper integrates our present understanding of the genetics of scapular development and congenital and neuromuscular conditions to generate insights into scapular morphology and biomechanics. Glenoid version as traditionally defined may have limited relevance when positioning the glenoid component during total shoulder arthroplasty. Further studies of soft-tissue and muscular balance are needed to fully understand the consequences of variations in glenoid version. LEVEL OF EVIDENCE: Review.