208. Low pelvic incidence (PI) patients are at high risk of over correction following ASD surgery

Abstract

BACKGROUND CONTEXT Age and pelvic incidence (PI) optimal alignment has been shown to minimize mechanical complications such as PJK. Low PI patients may be susceptible to overcorrection because PI specific alignment is not always prioritized. PURPOSE The purpose of this study is to examine the incidence of over-correction in low PI ASD patients undergoing surgical intervention, and to quantify the impact of over-correction on radiographic PJK in this patient population. STUDY DESIGN/SETTING Retrospective analysis of a prospective, multicenter database. PATIENT SAMPLE Surgical ASD patients with low pelvic incidence. OUTCOME MEASURES PJK defined as 1) proximal junctional angle (PJA, UIV – UIV+2) >10° and 2) increase in the PJA > 10° METHODS A prospective database of operative ASD patients was analyzed. Patients undergoing fusions greater than 5 levels and completed two-year follow-up were included. Low PI ( RESULTS A total of 118 low PI patients met inclusion criteria, and overcorrection occurred in 73.7% (n=87). By comparison, overcorrection occurred in only 53.1% of non-low PI patients enrolled in the same registry (p=0.0001).There was no statistically significant difference between overcorrected low PI patients and non-overcorrected in regards to baseline demographics and radiographic parameters (PI, PI-LL, PT, SVA), and HRQoL (SRS22R, NRS back / leg, ODI). The two groups were different in regards to surgical invasiveness (overcorrected 111.46 vs not overcorrected 95.6, p=0.03). The over-corrected group were less likely to have their apex of lordosis below the level of L4 (2.3% vs 19.35% p=0.001). They also had a lower proportion of their lumbar lordosis coming from L5-S1 (39% vs 48%, p=0.009), and a higher proportion of their lumbar lordosis coming from L1-L3 (8.23% vs 3.4%, p=0.04). Radiographic PJK occurred in 52% of low PI patients. Those who were over-corrected were more likely to experience radiographic PJK (OR 2.61, p=0.03). CONCLUSIONS Overcorrection is more frequent in low PI patients, occurring in 73.7% of cases. Those who were over-corrected were less likely to have their apex of lordosis below L4, and had a lower proportion of their overall lordosis coming from L5-S1. They were also more likely to experience radiographic PJK than their counterparts who were not over-corrected. These results highlight the importance of not over-correcting low PI patients, and paying attention to the location of the apex of lordosis. FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs.