Title:
Clinical relevance of persistent postoperative pain after total hip replacement - a prospective observational cohort study.

Abstract:
The development of persistent postoperative pain may occur following surgery, including total hip replacement. Yet, the prevalence may depend on the definition of persistent pain. This observational cohort study explored whether the prevalence of persistent pain after total hip replacement differs depending on the definition of persistent pain and evaluated the impact of ongoing pain on the patient's quality of life 6 months after surgery.
Pre- and postoperative characteristics of 125 patients undergoing elective total hip replacement were assessed and 104 patients were available for the follow-up interview, 6 months after surgery.
Six months after surgery, between 26% and 58% of patients still reported hip pain - depending on the definition of persistent pain. Patients with moderate-to-severe persistent pain intensity (>3 on a numerical rating scale) were more restricted in their daily life activities (Chronic Pain Grade - disability score) but did not differ in reported quality of life (Short-Form 12) from those with no pain or milder pain intensity. Maximal preoperative pain intensity and body mass index were the only independent factors influencing daily function 6 months after total hip replacement.
These findings support a high prevalence of persistent postoperative pain after total hip replacement and a large variability depending on the definition used. There was a close relation between physical functioning and pain as well as relevance of the patient's psychological state at the time of the operation.