Biomechanical analysis of proximal junctional kyphosis: preliminary results

Proximal junctional kyphosis (PJK) is a complication related to spinal instrumentation. Defined as a pathological kyphosis of levels above the upper instrumented vertebra, PJK is not yet fully understood although many studies have been conducted in this regard. The objective of this study is therefore to understand the influence of some biomechanical risk factors with respect to PJK. For this purpose, a biomechanical model has been developed and used to test three factors: the sagittal balance, the implant type used at the upper instrumented vertebra (UIV) and the proximal dissection (posterior ligaments disruption and joint capsule degeneration). The preliminary results showed that the PJK is correlated to both sagittal balance and the reduction of spinal stability due to posterior ligaments disruption and joint capsule degeneration.