The Classification of Glenoid Version and Its Relevance to Shoulder Instability

Background Previous studies have demonstrated that the glenoid fossa can be anteverted or retroverted with respect to the scapular spine and that this may affect the propensity to dislocate, although clinical studies have provided conflicting evidence. Methods We have used a highly accurate, noncontact laser morphometric method of analysis to determine the precise shape of 59 glenoid fossae from shoulders, with no evidence of instability, arthritis or rotator cuff disease. Results We have shown that, at the mid-glenoid level, most fossae are retroverted, although some are anteverted. Furthermore, below this level, the glenoid can either twist into greater anteversion or retroversion. This forms the basis of a classification system that describes how much static restraint to dislocation is provided by the bony glenoid, and we have repeated the work to identify any contribution from variations in the thickness of overlying articular cartilage. Of 59 fossae, five were of type 1A, comprising an anteverted glenoid that becomes increasingly anteverted below its equator and provides least bony restraint to anterior dislocation. Conclusions We propose that this classification system is used to study the effect of glenoid shape on shoulder stability and options for reconstruction.