Using four different clinical tools as predictors for pain after total hip arthroplasty: a prospective cohort study

BACKGROUND: Treatment of postoperative pain remains a significant clinical problem, and prediction of patients with a risk of higher postoperative pain levels is an important focus. We aimed to identify patients undergoing total hip arthroplasty (THA) with risk of higher pain levels at 24 h postoperatively by using four simple and easily available clinical tools. METHODS: This prospective observational cohort study included 102 patients having THA at Zealand University Hospital in Denmark. The following predictive tools were investigated for identifying patients with higher postoperative pain levels at 24 h postoperatively, both at rest and during mobilization: preoperative pain by peripheral venous cannulation (PVC) (dichotomized according to numerical rating scale pain ≤ 2/> 2 (PVC-Low/PVC-High) (primary outcome); the post anesthesia care unit (PACU) nurses’ expectations of patients pain levels; patients early pain levels at the PACU; and patients own forecast of postoperative pain levels. The Mann-Whitney U test was used to analyze comparisons between prediction groups. For the primary outcome we considered a p-value < 0.01 as statistically significant and for other outcomes a p-value of 0.05. RESULTS: We found no significant differences between the PVC groups for pain during mobilization at 24-h postoperatively: PVC-Low: 6 (4–8) (median, (IQR)) versus PVC-High: 7 (5–8) (median, (IQR)), p = 0.10; and for pain at rest: PVC-Low 2 (0–3) (median, (IQR)) versus PVC-High 3 (2–5) (median, (IQR)), p = 0.12. Other comparisons performed between predictive groups did not differ significantly. CONCLUSIONS: In this prospective cohort study of 102 THA patients, we did not find that preoperative pain by PVC, when using a cut-off point of NRS ≤ 2, were able to predict postoperative pain at 24 h postoperatively. Neither did PACU nurses’ prediction of pain, patients forecast of pain, nor did maximum pain levels at the PACU. TRIAL REGISTRATION: Retrospectively registered 20th February 2018 at ClinicalTrials.gov (NCT03439566).