Oral Presentation 50th International Society for the Study of the Lumbar Spine Annual Meeting 2024

Introduction: Several studies have explored strategies to prevent PJK. Our study introduces a novel strategy to address the unresolved issue of PJK in ASD, utilizing recombinant human bone morphogenetic protein-2 (rhBMP-2). This study aimed to investigate the preventive effects of UIV (Upper instrumented vertebrae) rhBMP-2 injection on PJK and proximal junctional failure (PJF) and to determine whether UIV bone density significantly increases locally. This study design is a retrospective and prospective case control study.

Methods: All surgeries were performed with instrumentation and fusion from iliac to T10. In the experimental group, consisting of 25 patients with ASD, rhBMP-2 injection was administered to the vertebral body of UIV. To minimize performance bias, the control-1 group included 66 patients who had undergone ASD surgery by the same surgeon in the year preceding the commencement of the study. Control-2 consisted of 63 patients who had undergone ASD surgery by the same surgeon during the year following the end of the study for experimental group. Postoperatively, we evaluated presence of PJK and PJF, change in the Hounsfield unit (HU) of UIV after 1 year of follow-up. The control-1 group was respectively collected data and the experimental group and control-2 group were prospectively collected data.

Results: When comparing baseline characteristics with control groups, a significant difference was observed only in BMI with control-1 (p=0.006), control-total (control-1 + control-2, p=0.026) having a higher BMI than the study group. In the group that received rhBMP-2 at UIV, there were 3 cases (12.0%) of PJK, whereas the control-1 and control-2 had 26 cases (39.4%, BMI-adjusted p=0.010) and 20 cases (31.7%, BMI-adjusted p=0.078), respectively. In the control-total group (combining control-1 and control-2 groups), there were 46 cases (35.7%, BMI-adjusted p=0.025) of PJK. Regarding HU measurements, the UIV that received rhBMP-2 showed a statistically significant increase compared with the preoperative values 1 year after surgery (p=0.001).  

Discussion: This study aimed to reduce the influence of surgical technique changes and performance bias. Samples were collected from patients operated on by a single surgeon. To minimize the impact of surgical technique variations, two control groups were created: patients operated on within one year before the study started and those operated on within one year after it ended. This innovative approach offers several advantages compared to previous methods for preventing PJK. Firstly, it provides a longer-lasting augmentation effect compared to UIV cement augmentation, using a biological mechanism. Unlike cement augmentation, this new strategy doesn't alter the bone properties, reducing the risk of complications like adjacent-level fractures commonly associated with cement augmentation. Second, in contrast to using anabolic agents, such as parathyroid hormone analogs, to prevent PJK, it focuses more specifically on the most vulnerable site, the UIV.