Comparison of three different posterior fixation techniques in transforaminal lumbar interbody fusion for two-level lumbar degenerative diseases: At a mean follow up time of 46 months

•We are the first to investigate three fixation techniques in two-level lumbar cases.•UPS/UPSFS could achieve satisfactory mid-term clinical outcome comparable to BPS.•UPS instrumented TLIF should be prudently performed for two-level cases.•Cannulated screws should be replaced by solid screws in UPSFS instrumented TLIF.