Editorial Commentary: Glenoid Bone Loss Measurements in Shoulder Instability-Precise but Not Accurate

Glenoid defects are important to consider when choosing the surgical stabilization technique in shoulder instability patients. Several measurement methods to determine the extent of glenoid bone loss have been proposed and their reliability or precision proved. However, it must be considered that these defect extent measurements are only surrogate parameters trying to express the loss of biomechanical stability generated by a glenoid defect, which in fact they do not do accurately. Current defect measurement techniques are either linear based (1-dimensional) or area based (2-dimensional) but do not take into account the 3-dimensional shape of the glenoid concavity, which creates stability by means of the concavity-compression effect. Furthermore, none of the current measurement methods take into account the native glenoid concavity shape, which significantly differs between patients and therefore also affects the biomechanical consequence a glenoid defect generates. To improve the accuracy of current glenoid defect measurement techniques in expressing the loss of biomechanical stability generated by a glenoid defect, measurements should take into account the concave shape of the glenoid (3-dimensional measurements) and account for the baseline shape of the native glenoid (4-dimensional measurements).