Clinical outcome in decompression alone versus decompression and instrumented fusion in patients with isthmic spondylolisthesis: a prospective cohort study

OBJECTIVE In the surgical treatment of isthmic spondylolisthesis, it is debatable whether instrumented fusion is mandatory in addition to decompression. The objective of this prospective cohort study was to assess the long-term effect of decompression alone compared with decompression and instrumented fusion in patients who underwent the intervention of their own preference. The results were compared with those in patients who underwent randomly assigned treatment. METHODS The authors performed a prospective observational multicenter cohort study, including 91 patients with isthmic spondylolisthesis assigned to undergo either decompression alone (n = 44) or decompression and fusion (n = 47). The main outcomes were the Roland-Morris Disability Questionnaire (RDQ) scores and the patient's perceived recovery at the 2-year follow-up. Secondary outcomes were visual analog scale (VAS) leg pain and back pain scores and the reoperation rate. A meta-analysis was performed for data from this cohort study (n = 91) and from a randomized controlled trial (RCT) previously reported by the authors (n = 84). Subgroup analyses were performed on these combined data for age, sex, weight, smoking, and Meyerding grade. RESULTS At the 12-week follow-up, improvements of RDQ scores were comparable for the two procedures (decompression alone [D group] 4.4, 95% CI 2.3-6.5; decompression and fusion [DF group] 5.8, 95% CI -4.3 to 1.4; p = 0.31). Likewise, VAS leg pain scores (D group 35.0, 95% CI 24.5-45.6; DF group 47.5, 95% CI 37.4-57.5; p = 0.09) and VAS back pain scores (D group 23.5, 95% CI 13.3-33.7; DF group 34.0, 95% CI 24.1-43.8; p = 0.15) were comparable. At the 2-year follow-up, there were no significant differences between the two groups in terms of scores for RDQ (difference -3.1, 95% CI -6.4 to 0.3, p = 0.07), VAS leg pain (difference -7.4, 95% CI -22.1 to 7.2, p = 0.31), and VAS back pain (difference -11.4, 95% CI -25.7 to 2.9, p = 0.12). In contrast, patient-perceived recovery from leg pain was significantly higher in the DF group (79% vs 51%, p = 0.02). Subgroup analyses did not demonstrate a superior outcome for decompression alone compared with decompression and fusion. Nine patients (20.5%) underwent reoperation in total, all in the D group. The meta-analysis including both the cohort and RCT populations yielded an estimated pooled mean difference in RDQ of -3.7 (95% CI -5.94 to -1.55, p = 0.0008) in favor of decompression and fusion at the 2-year follow- up. CONCLUSIONS In patients with isthmic spondylolisthesis, at the 2-year follow-up, patients who underwent decompression and fusion showed superior functional outcome and perceived recovery compared with those who underwent decompression alone. No subgroups benefited from decompression alone. Therefore, decompression and fusion is recommended over decompression alone as a primary surgical treatment option in isthmic spondylolisthesis.