Novel Strategy using Transpedicular Injection of rhBMP-2 to Reduce the Proximal Junctional Kyphosis for Adult Spinal Deformity Correction Surgery

Abstract Injecting recombinant human bone morphogenetic protein-2 (rhBMP-2) into the uppermost instrumented vertebra (UIV) during surgery to increase the bone for adult spinal deformity (ASD) is expected to be protective against the development of proximal junctional kyphosis (PJK) and proximal junctional failure (PJF). The 25 patients from study group had received 0.5 mg rhBMP-2 mixed with 1.5 g β-tricalcium phosphate paste injection into the UIV during surgery. The control group consisted of 75 age and sex matched patients who underwent surgery immediately before the start of the study. The incidences of PJK and PJF were analyzed as primary outcomes. Spinopelvic parameters and patient-reported outcomes were analyzed as secondary outcomes. Hounsfield unit (HU) measurements were performed to confirm the effect of rhBMP-2 on bone formation at preoperative and postoperative computed tomography (CT). PJK and PJF was more occurred in control group than study group (p = 0.02, 0.29, respectively). The HU of the UIV significantly increased 6 months after surgery. And the increment at the UIV was also significantly greater than that at the UIV-1 6 months after surgery. Injection of rhBMP-2 with TCP into the UIV reduced PJK and PJF rates 6 months after surgery with new bone formation.