Difference in stiffness-related functional disability between decompression alone and decompression with short segments fusion (1 or 2 levels) in the lower lumbar region: a propensity scores matching study.

Background Context: Stiffness-related functional disability (SRFD) is a well-known complication after long-segment fusion surgery. However, SRFD following decompression with short-segment fusion (1 or 2 levels) compared with decompression alone surgery in the lower lumbar region, which accounts for a significant portion of lumbar range of motion, is poorly documented.

Purpose: This study aimed to compare SRFD after decompression alone (D-A) surgery and decompression with short-segment fusion (D+F) surgery in the lower lumbar region.

Study Design/setting: Retrospective observational study.

Patient Sample: Patients who underwent D-A or D+F surgery at the lower lumbar region (L4 to S1) between 2016 and 2022, with a follow-up period of over 2 years, were reviewed.

Outcome Measure: The visual analog scale (VAS) for the back and leg, Oswestry disability index (ODI), specific functional disability index (SFDI) for SRFD, and lumbar range of motion (LROM) were evaluated as clinical and radiological outcomes preoperatively and at 1 and 2 years postoperatively.

Methods: We divided the lower lumbar region into three segments: L4-5, L5-S1, and L4-5-S1. Out Of the initial 425 patients, 32 pairs in the L4-5 segment, 36 pairs in the L5-S1 segment, and 27 pairs in the L4-5-S1 segment were included in the final cohort after conducting propensity score matching (1:1). Outcomes were compared between the two groups within each segment.

Results: The mean follow-up periods were 27.2, 26.1, and 26.5 months in each group, respectively. In L4-5, there was no difference in the VAS scores for leg pain, ODI, SFDI, and LROM. However, the VAS for back pain was significantly higher in the D+F group preoperatively and at 2 years postoperatively (6.4±2.0 vs. 3.6±2.3, p=.001; 3.6±2.7 vs. 2.1±1.9, p=.046). In the L5-S1, VAS for back pain was significantly higher in the D+F group preoperatively and at 2 years postoperatively (6.2±2.0 vs. 4.4±1.9, p=.001; 4.2±1.7 vs. 3.5±1.3, p=.034). The LROM was significantly lower in the D+F group at 1- and 2-year postoperatively (33.3±8.0° vs. 38.4±9.2°, p=.015; 32.4±7.3° vs. 36.8±9.4°, p=.032). However, the SFDI was higher in the D+F group only at 1 year postoperatively (22.4±7.7 vs. 19.2±5.2, p=.037). In the L4-5-S1, SFDI was significantly higher in the D+F group at 1- and 2-year postoperatively (1 yr: 22.7±7.7 vs. 17.1±7.9, p=.011; 2 yrs: 22.3±7.6 vs. 17.9±7.2, p=.001), LROM was significantly lower in the D+F group (1 yr: 24.1±8.3° vs. 37.0±8.4°, p=.001; 2 yrs: 25.0±6.9° vs. 38.2±6.4°, p=.001).

Conclusion: For the L4-5 segment, there were no differences in LROM and SFDI between the D-A and D+F groups. At L5-S1, significant differences were noted in both parameters at 1-year postoperatively, but SFDI showed no significant differences by the 2-year mark, despite differences in LROM. For two-level fusion at L4-5-S1, significant differences in both LROM and SFDI persisted 2 years postoperatively.