Fig. 2.

Change scores in the ODI over time are displayed according to baseline low back pain (LBP). The surgery p value compares baseline LBP ≤ 4 with baseline LBP ≥ 5 among surgery patients. The nonoperative p value compares baseline LBP ≤ 4 with baseline LBP ≥ 5 among nonoperative patients. The interaction p value compares the treatment effect (surgery versus nonoperative) between baseline LBP ≤ 4 and baseline LBP ≥ 5. All p values are time-weighted averages over 8 years (ie, area under the curve).