The impact of early recovery on long-term outcomes in a cohort of patients undergoing prolonged nonoperative treatment for lumbar disc herniation

Abstract

The authors comprehensively studied the recovery of individual patients undergoing treatment for lumbar disc herniation. The primary goal was to gain insight into the variability of individual patient utility scores within a treatment cohort. The secondary goal was to determine how the rates and variability of patient recovery over time, represented by improvement in utility scores, affected long-term patient outcomes. EuroQol Group-5 Dimension (EQ-5D) scores were obtained at baseline and at 2, 4, 8, 12, 26, 38, and 52 weeks for 93 patients treated under a prolonged conservative care protocol for lumbar disc herniation. Gaussian kernel densities were used to estimate the distribution of utility scores at each time point. Logistic regression and multistate Markov models were used to characterize individual patient improvement over time. Fisher exact tests were used to compare the distribution of EQ-5D domain scores. The distribution of utility scores was bimodal at 1 year and effectively sorted patients into a "higher" utility group (EQ-5D = 1; 43% of cohort) and a "lower" utility group (EQ-5D ≤ 0.86; 57% of cohort). Fisher exact tests revealed that pain/discomfort, mobility, and usual activities significantly differed between the 2 utility groups (p ≪ 0.001). The utility groups emerged at 8 weeks and were stable for the remainder of the treatment period. Using utility scores from 8 weeks, regression models predicted 1-year outcomes with 62% accuracy. This study is the first to comprehensively consider the utility recovery of individual patients within a treatment cohort for lumbar disc herniation. The results suggest that most utility is recovered during the early treatment period. Moreover, the findings suggest that initial improvement is critical to a patient's long-term outcome: patients who do not experience significant initial recovery appear unlikely to do so at a later time under the same treatment protocol.