Acute pain trajectories and the persistence of post-surgical pain: a longitudinal study after total hip arthroplasty.

PURPOSE: The aim of this study was to explore acute movement-evoked postoperative pain intensity trajectories over the first 5 days after total hip arthroplasty (THA) and to examine how these pain trajectories are associated with pain-related outcomes 6 weeks and 6 months later.

METHODS: A total of 150 adult patients [72 women (48.0 %); mean age 60.0 ± 9.2 (standard deviation) years] completed pain questionnaires preoperatively, several times daily postoperatively until hospital discharge, and 6 weeks and 6 months after surgery.

RESULTS: Results showed that the best model had four different acute postoperative pain trajectories and a significant quadratic term. The trajectories varied in terms of initial pain intensity levels and rates of decline/increase in pain over the first 4 postoperative days. Significant predictors of pain trajectory membership were preoperative pain disability and anxiety as well as cumulative morphine consumption 24 h following surgery. Pain trajectories were significantly associated with levels of pain intensity and anxiety at 6 weeks but not at 6 months postoperatively.

CONCLUSION: This study showed that during the postoperative period patients differed in terms of pain intensity profiles and that these differences were associated with outcomes for up to 6 weeks following surgery. Pain trajectories were not predictive of persistent postoperative pain status at 6 months. Nonetheless, these results highlight the importance of patient heterogeneity in acute postoperative pain and pain-related outcomes months after THA.