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

Figure 2

Cumulative incidence of pain nonresponders with ACD and control through 2 years. Notes: in unadjusted analysis (top panel), time to pain non-response defined as days to first instance of pain score improvement <20 points relative to baseline. In integrated analysis (bottom panel), time to pain nonresponse additionally includes patients at the time of symptomatic reherniation detection. Comparing ACD to controls, the cumulative incidence of pain nonresponders through 2 years was 16.4% versus 18.3% (log-rank p = 0.51) in unadjusted analysis and 23.7% versus 31.2% (log-rank p = 0.04) in integrated analysis. ACD, annular closure device; VAS, visual analogue scale.