Characteristics of the Patient Cohort
The patient characteristics are shown in Table 1. Preoperatively, 31% (n = 135) of the patients had severe LBP, 38% (n = 166) had moderate LBP, and 31% (n = 135) had mild LBP (Figure 1). Between the baseline and 2-year postoperative evaluations, there were significant improvements in the VAS score for LBP as well as all other measured PROs (VAS change 2.3 [95% CI: 2.0–2.6], P < 0.01, Table 1). Of the 436 patients, 55% (n = 240) achieved an MCID, 67% (n = 292) had no or mild LBP (VAS<4.5), 48% (n = 208) achieved an MSS, and 10% (n = 42) had persistent severe LBP after surgery (Figure 2).
The distribution of baseline and 2-year postoperative LBP VAS score in surgically treated patients with LSS.
Unadjusted and Adjusted Risk Analysis for 2-year Postoperative Persistent LBP (VAS Score ≥4.5) Among Surgically Treated Patients With LSS
In univariate analysis, sex (female), age, baseline severe LBP, and joint replacement were candidate risk factors for persistent LBP (P < 0.20, supplemental Table 1, https://links.lww.com/BRS/B802). In the multivariate analysis, only sex and the presence of severe baseline LBP were identified as independent risk factors (sex: female: OR 1.9 [95% CI: 1.2–3.0], severe baseline LBP [VAS≥7.5]: OR 1.9 [95% CI: 1.2–3.1], Table 2).
Unadjusted and Adjusted Risk Analysis for Baseline Severe LBP (VAS Score ≥7.5) Among Surgically Treated Patients With LSS
We then assessed the factors that can potentially affect the baseline severity of LBP. In univariate analysis, age, sex (female), a history of cerebral palsy, a history of rheumatoid arthritis, frailty, joint replacement, and baseline functional status were candidate risk factors for baseline severe LBP (P < 0.20, supplemental Table 2, https://links.lww.com/BRS/B802, 3, https://links.lww.com/BRS/B802). In a multivariate analysis, the independent risk factors for severe baseline LBP were sex and mental status (sex [female]: OR 1.7[1.1–2.7] P = 0.03, mental status: OR 3.8[2.4–6.0] P < 0.01, Table 3).
Comparisons of Postoperative LBP Between Propensity-score-matched Female and Male Patients With LSS
The distributions of the VAS scores for baseline LBP were significantly different between male and female patients, and more female patients had severe baseline LBP (Figure 3, supplemental Table 3, https://links.lww.com/BRS/B802). The comparisons of recovery kinetics between male and female patients showed statistically worse VAS scores and JOABPEQ pain intensity domain scores at baseline and all postoperative visits up to 2 years in the female group (Figure 4).
Comparison of distribution of baseline LBP VAS score between female and male patients (rounded). More female patients had severe LBP at preoperative visit.
Comparisons of the VAS score of LBP and JOABPEQ pain intensity domain results between male and female patients at baseline, 1-year, and 2-year postoperative follow-up evaluations (means and standard deviations). A, Comparisons of VAS score of LBP showed statistically higher VAS scores at all visits in the female group. The difference of the VAS score of LBP between female and male patients was consistent 1-year after surgery to 2-year after surgery. B, Comparisons of JOABPEQ pain intensity domain showed statistically higher VAS scores at all visits in the female group. The difference of the postoperative JOABPEQ pain intensity domain between female and male patients was consistent 1-year after surgery to 2-year after surgery.
Due to the statistically higher baseline VAS score for LBP in female patients, we propensity score matched male and female patients by potential confounders to eliminate the effect of confounders on postoperative LBP. An analysis of 102 pairs of 204 male and female propensity-score-matched patients by age, LBP aetiology, frailty, joint replacement, mental status, and baseline VAS score showed no difference in the improvement of LBP at 2 years after surgery (male vs. female: 2-yr postoperative LBP VAS score 3.8 ± 2.8 vs. 4.0 ± 2.9, P = 0.61, VAS score changes 3.1 ± 2.9 vs. 2.7 ± 3.0, P = 0.38, supplemental Table 5, https://links.lww.com/BRS/B802).
Likelihood of LBP Improvement at 2 Years Post Operation in Patients With Baseline Severe LBP
Among the 135 patients who had baseline severe LBP, the patients who answered #1 for any of questions Q5–3, 4, or 6 in the JOABPEQ mental health section (Q5–3; Have you been discouraged and depressed? Answer #1: Always, Q5–4; Do you feel exhausted? Answer #1: Always, Q5–6; Do you think you are in decent health? Answer #1: Not at all [my health is very poor]) were 2.6-fold more likely to have postoperative persistent LBP (VAS≧4.5), and 61.7% of these patients had persistent LBP after surgery (OR 2.6 [95% CI: 1.2–5.2], P = 0.01).
Spine. 2022;47(7):557-564. © 2022 Lippincott Williams & Wilkins