We determined whether the PA was within an extension of the osteotomy area. The shortest distance (yellow arrow) between the posterior tibial cortex and PA within the osteotomy area was measured (Distance 1). Moreover, the shortest distance between the line extending the osteotomy posteriorly and the PA was measured (Distance 2; red arrow). The distance 2 was determined to be 0 mm if the PA was within the extension of the osteotomy area.