Posterior elements disruption with hybrid constructs in AIS patients: is there an impact on proximal junctional kyphosis?

Proximal junctional kyphosis (PJK) is a frequent proximal adjacent segment disease following spinal fusion in adolescent idiopathic scoliosis (AIS) and its rate has been estimated to 28% in the literature. The etiology is multifactorial, and risk factors associated with PJK are controversial. The aim of this study was to demonstrate that the disruption of muscular and bony tissue above the upper instrumented vertebra (UIV) during surgery does not increase the rate of PJK in patients undergoing posterior fusion for adolescent idiopathic scoliosis.

50 patients with AIS operated between June 2014 and January 2016 were included. Every patient underwent a long posterior spine arthrodesis with a hybrid construct (proximal lamino-laminar claw, thoracic sublaminar bands and lumbar screws). The dissection of posterior elements above the UIV was necessary for the placement of proximal anchors. Radiographic analysis including proximal junctional angle, spino-pelvic parameters (cervical lordosis, thoracic kyphosis TK, lumbar lordosis, pelvic incidence, pelvic tilt, sacral slope) and sagittal vertical axis were collected preoperatively and postoperatively at the last control. The numbers of fused levels, locations of upper instrumented vertebra, locations of lower instrumented vertebra, length of fusion segments were also recorded. Multiple odd ratios and other statistical analysis were performed to evaluate the relation between PJK and the potential risk factors.

There were 43 females and 7 males with a mean age of 14.8 years at surgery. PJK occurred in 5 out of 50 cases with an incidence of 10%. The mean follow-up was 18 months. There was no significant difference in gender (OR 1.36, p = 0.8), decrease of TK (OR 1.63, p = 0 0.69), location of UIV (OR 2.25, p = 0.4), LIV (OR 2, p = 0.55), and SVA change (OR 1.63, p = 0.46).

The disruption of ligamentous and bony tissue proximal to the UIV during the surgery does not increase the rate of PJK.