Upper instrumented vertebra-femoral angle and correlation with proximal junctional kyphosis in adult spinal deformity.

The more posterior the UIV is from the femoral head center after lower thoracic to pelvis surgical correction for ASD, the more patients are at risk for PJK. The greater the magnitude of posterior translation of the UIV from the femoral head center from preop to postop, the greater the likelihood for PJF.