Comparison of 1-year fusion rates between demineralized bone matrix and a combination of bone morphogenetic protein-2 and β-tricalcium phosphate in oblique lumbar interbody fusion: a retrospective study in Korea

Objective: To compare interbody fusion rates at 1 year, assessed by computed tomography (CT), between demineralized bone matrix (DBM) and bone morphogenetic protein-2 (BMP-2) combined with β-tricalcium phosphate (β-TCP) in patients undergoing oblique lumbar interbody fusion (OLIF).Methods: We retrospectively reviewed 54 patients who underwent OLIF at 77 levels and had 1-year CT scans available for Bridwell grading. DBM was used in 19 patients at 28 levels, and BMP-2 plus β-TCP was used in 35 patients at 49 levels. Fusion was defined as Bridwell grade I or II. Fisher’s exact test was used for the primary comparison by treated level, and logistic regression with patient-clustered robust standard errors was used for the sensitivity analysis.Results: Fusion was achieved at 13 of 28 levels with DBM and 38 of 49 levels with BMP-2 plus β-TCP (46.4% vs. 77.6%, P=0.011), yielding an unadjusted odds ratio (OR) of 3.99 (95% confidence interval [CI], 1.46–10.85). BMP-2 plus β-TCP remained associated with fusion after adjustment for age, sex, and number of operated levels (adjusted OR, 5.23; 95% CI, 1.33–20.60; P=0.018). The rates of recorded complications did not differ significantly between groups.Conclusion: BMP-2 combined with β-TCP was associated with a higher fusion rate at 1 year after OLIF than DBM. The retrospective design and potential calendar-period confounding warrant prospective studies.