P101. Pseudarthrosis and rod fracture at the distal levels of a long construct are associated with proximal junctional kyphosis after ASD surgery

Abstract

BACKGROUND CONTEXT More distal fusion levels and overall stiffness of a long fusion construct for ASD may result in larger range of motion and stress at the proximal junctional level. Stability of distal fixation, inferred by the presence or absence of pseudarthrosis and rod fracture, may affect proximal junctional stresses and contribute to proximal junctional kyphosis (PJK) and associated revision surgery.To date, very few studies have evaluated the relationship between achieving solid fusion at the base of a long construct and rate of PJK. PURPOSE To assess the relationship between lumbosacral rod fracture and pseudarthrosis and development of proximal junctional kyphosis (PJK) after long construct ASD surgery. STUDY DESIGN/SETTING Retrospective review of prospectively collected single center database. PATIENT SAMPLE We performed a review of 942 patients who underwent ASD surgery (Age: 55 ± 23 y; mFI: .41 ± .67; Levels fused: 10.1 ± 4.2; Revision: 22.3%; 3CO: 12.3%). OUTCOME MEASURES We assessed the rate of PJK at minimum 2-year follow-up, as well as the rate of pseudarthrosis or rod fracture at the lower lumbar levels or lumbosacral junction, and the association between these complications. METHODS A total of 942 patients were divided into PJK and non-PJK groups using whole spine standing radiographs. The incidences of PJK, and lumbar or lumbosacral pseudarthrosis were defined. The relationship between these complications was assessed. RESULTS The cohort had sagittal malalignment as demonstrated by PT 23.7 ± 12.4°, TPA 22.5 ± 26.2°, and SVA 77.8 ± 70 mm. The PJK and non-PJK groups comprised 350 and 592 cases respectively. Mean follow-up time was 48.9 months. There was no significant difference in baseline SVA, T1 pelvic angle, change in sagittal alignment postoperatively, and surgical invasiveness index between the two groups. There were 11.1% of patients who developed PJK had a pseudarthrosis at the lower lumbar levels or lumbosacral junction, versus 6.4% of those who did not develop PJK (p=0.011). Patients who developed PJK had a significantly higher rate of rod fracture in the lower lumbar levels or lumbosacral junction (15.4%) versus those who did not develop PJK (7.3%) (p CONCLUSIONS Pseudarthrosis and rod fracture at the lower lumbar levels or lumbosacral junction were predictive of development of PJK at final follow-up. This may indicate that distal stability of a long construct has a significant impact on stresses at the proximal junction. FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs.