Fig. 4From: Prognostic factors for medial open-wedge high tibial osteotomy with spacer implantation in patients with medial compartmental knee osteoarthritisDefinition and measurement of HKAA, MPTA, PTSA, and BPI. Angle α expresses the HKAA, angle β expresses the MPTA (a), and angle γ expresses the PTSA (b). The Blackburn–Peel index (BPI) is equal to b/a (c).Back to article page