Can unilateral-transforaminal lumbar interbody fusion replace the traditional transforaminal lumbar interbody fusion procedure for lumbar degenerative disc diseases?: a single center matched case-control mid-term outcome study.

Study design: Matched case-control study.

Purpose: To evaluate the midterm outcomes of unilateral pedicle screw fixation (UPSF) versus bilateral pedicle screw fixation (BPSF) in transforaminal lumbar interbody fusion (TLIF) procedure, ascertain efficacy of UPSF in adequately decompressing contralateral foramen+spinal canal and reducing rate of adjacent segment degeneration (ASD) at 4-8-year follow-up (FU).

Overview of literature: Previous meta-analyses found no significant differences between UPSF and BPSF regarding fusion rates, clinical and radiological outcomes; however, few studies have reported higher rates of cage migration/subsidence and pseudoarthrosis in the UPSF. No study has evaluated the impact of UPSF on indirect decompression and ASD.

Methods: Retrospective analysis of 319 patients treated with UPSF vs. 331 patients treated with BPSF between 2012 to 2020. Clinical and radiological outcomes were evaluated at 6 months, 1 year, 2 years, and 4 years postoperatively. X-rays were used to assess fusion+ASD and computed tomography scans in doubtful cases. Magnetic resonance imaging was used at last FU to determine cross-sectional area of cord (CSA), foraminal height (FH), and width (FW) restoration.

Results: The mean FU duration was 50 months (range, 44-140 months). In UPSF, CSA increased by 2.3 times from preoperative values; FH and FW increased by 25% and 17.5%, respectively, at last FU (p<0.001); fusion rate was 94.3%, comparable to BPSF (similar CSA, FW, FH, 96.4% fusion rate). In UPSF, adjacent disc height remained stable, from preoperative 11.39±2.03 to 10.97±1.93 postoperatively at 4 years and 10.03±1.88 at 8 years. BPSF showed ASD in 14 (4.47%) vs. three patients (1.06%) in UPSF (p<0.04). Complication rates were similar (6.58% UPSF vs. 6.04% BPSF, p>0.05).

Conclusions: UPSF-TLIF is comparable to BPSF in terms of patient-reported clinical outcomes, fusion rates, and complication rates while being superior in terms of lesser ASD. UPSF enables radiologically and clinically significant contralateral indirect neural foraminal decompression and canal decompression without disturbing the contralateral side anatomy, unlike BPSF.