Fig. 2

The double-circle system in anteroposterior view. The inside circle was the best-fit circle of the humeral head and the center was set as point C. The outside circle was a concentric circle with point C as the center and passed through the most lateral edge of the greater tuberosity. The radius of the inside circle was defined as the humeral head radius (HHR) and that of the outside circle was defined as the greater tuberosity radius (GTR). The ratio of HHR to GTR was defined as the double-circle radius ratio (DRR)