When the spine has been fused or some type of procedure has been performed, the upper end of the construct and instrumentation is subject to a lot of stress forces. This can result in excessive amount of compensation from the remaining spinal levels due to the loss of movement at that fixed surgical region. The terms proximal junctional kyphosis and proximal junctional failure are both used to describe and abnormality at the adjacent level to some type of construct or intervention.
The case of proximal junctional kyphosis there are only radiologic findings of excessive hyper motion or instability. This is classically evaluated by measuring the Cobb angle and finding it greater than 10°. However proximal junctional failure on the other hand relates to symptomatic proximal junctional kyphosis, meaning that the patient not only has the radiographic findings but also presents with pain, signs of instability, or neurologic changes. In general proximal junctional kyphosis can be simply monitored for further worsen while proximal junctional failure will require intervention.