Osteoporosis Delimit the Indication for Additional Fixation in Oblique Lumbar Interbody Fusion

Abstract Study design: A retrospective cohort study.Objective: To detect the boundary of indications of fixation in OLIF surgery.Methods: Review patients undergoing stand-alone or combined OLIF. Measure the disc height increment (ΔDH), foraminal height (FH), cage subsidence (CS). VAS and the ODI was used to evaluate low back pain and functionality. Multiple linear regression were used to determine the risk factors of CS.Results: A totle of 66 consecutive patients included. The BMD in combined group was significantly lower than that of stand-alone group(p=0.005). The combined group showed better FH maintenance at 6 months (p= 0.049) and last follow-up (p= 0.019). In combined group, tCS was significantly lower at all post-operation point (p≤0.001). BMD was a mild negative correlated factor for CS in combined group (r= -0.602, p= 0.001)and a strongly negative correlated factor in stand-alone group (r= -0.797, p< 0.001). Greater mCS significantly associated with worse VAS (r=0.685, p<0.001) and ODI (r=0.616, p<0.001) in stand-alone group, and this effect was significantly weakened in the combined group as VAS (r=0.427, p=0.033) and ODI (r=0.594, p=0.002). Patients with stand-alone OLIF were at risk of severe CS when BMD Conclusions: The long-term fusion rates and functionality improvements of OLIF with or without fixation are comparable. Patients with BMD < -1.38 may not suitable for stand-alone procedure due to higher risk of severe CS and worse clinical outcomes. Additional fixation can extends the applicable boundary to a BMD = -4.77.