Challenges in the Analysis of Longitudinal Pain Data: Practical Lessons from a Randomized Trial of Annular Closure in Lumbar Disc Surgery

Figure 1

VAS pain scores with ACD and control through 2 years. Notes: in unadjusted analysis (top panel), values represent actual VAS scores recorded at scheduled follow-up visits. In integrated analysis (bottom panel), the BOCF approach was used where the baseline VAS pain score was substituted for the patient-reported pain score at the time of symptomatic reherniation and at each subsequent follow-up visit through 2 years. Comparing ACD to controls, VAS change from baseline (mean±SE) was -68 ± 2 versus -67 ± 2 (p = 0.06) in unadjusted analysis and -62 ± 2 versus -52 ± 2 (p < 0.001) in integrated analysis. Abbreviations: ACD, annular closure device; BOCF, baseline observation carried forward; SE, standard error; VAS, visual analogue scale.