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  • Minimally Effective Dose of Bone Morphogenetic Protein (BMP) in Minimally Invasive (MIS) Lumbar Interbody Fusions: 714 Patients in a Dose-Finding Statistical Modeling Cohort Study

    Final Number:

    Evan Joseph Lytle DO; Doris Tong MD; Lisa Govila; Roger F Gonda MD; Clifford Michael Houseman DO; Teck-Mun Soo MD

    Study Design:

    Subject Category:

    Meeting: Congress of Neurological Surgeons 2017 Annual Meeting

    Introduction: With increasing doses of BMP, the risk of adverse events increases. We seek to demonstrate the minimally effective BMP dose to achieve a fusion in MIS TLIF.

    Methods: Consecutive patients from 2009-2014, who underwent MIS lumbar interbody fusion, were reviewed. We excluded patients without radiographic (XR) follow up =3m postop. Dose of BMP/interspace was determined. Fusion was determined by XR evaluated by independent radiologists. A pilot study was performed to determine the baseline fusion rate in our population and sample size. We used multiple logistic regression with fusion at =3m and =6m as the dependent variable and BMP dose/interspace, single vs. multi-level, postop XR interval, smoking, gender, and age as covariates. The Expß coefficient represented change in odds of fusion for one-unit change in an independent variable. Minimally effective dose of BMP was determined by running separate logistic regressions for discrete BMP dose ranges for all fusion levels and a subgroup of multi-level fusions. We considered p-value = 0.0083 as significant to compensate for multiple comparisons.

    Results: We identified 1,168 interspaces among 714 unique patients. Average BMP dose was 1.25mg/level (Table 1). Dose/level, and multi-level fusion were significant predictors for fusion at =6m postop with an overall fusion rates of 95% (Table 2). Odds of fusion increased by 4.7 when BMP dose was increased from range 1 (0.16-1mg/lvl) to range 2 (1.01-2mg/lvl), but did not increase when BMP dose increased from range 2 to range 3 (>2mg/lvl) (Table 3). The odds of fusion in multi-level fusions increased by 4.0 when BMP dose increased from range 1-2, but fusion odds did not increase when increased from range 2-3 (Table 4).

    Conclusions: We found using a BMP dose of 1.01-2mg/level had a fusion rate of 95%. Increasing the dose above 2mg/level does not correlate with an increase in odds of fusion.

    Patient Care: Determining the minimally effective dose of BMP will reduce the patients exposure to BMP and potential dose related adverse events. It will also decrease the operative cost by preventing the overuse of BMP.

    Learning Objectives: By the conclusion of this session, participants should be able to: 1) Describe current recommendation with regards to BMP use in transforaminal interbody fusions. 2) Identifiy a minimally effective BMP dose/level and associated fusion rate.


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