Chronic pain following total hip arthroplasty: a nationwide questionnaire study L. NIKOLAJSEN 1,2 , B. BRANDSBORG 2 , U. LUCHT 3 , T. S. JENSEN 2 and H. KEHLET 4 1 Department of Anesthesiology, 2 Danish Pain Research Center and 3 Department of Orthopedic Surgery, Aarhus University Hospital, Aarhus, and 4 Section of Surgical Pathophysiology, Rigshospitalet, Copenhagen, Denmark Background: Chronic post-operative pain is a well-recognized problem after various types of surgery, but little is known about chronic pain after orthopedic surgery. Severe pre-operative pain is the primary indication for total hip arthroplasty (THA). Therefore, we examined the prevalence of chronic pain after THA in relation to pre-operative pain and early post-operative pain. Methods: A questionnaire was sent to 1231 consecutive patients who had undergone THA 12—18 months previously, and whose operations had been reported to the Danish Hip Arthroplasty Registry. Results: The response rate was 93.6%. Two hundred and ninety- four patients (28.1%) had chronic ipsilateral hip pain at the time of completion of the questionnaire, and pain limited daily activ- ities to a moderate, severe or very severe degree in 12.1%. The chronic pain state was related to the recalled intensity of early post-operative pain [95% confidence interval (CI), 20.4—33.4%] and pain complaints from other sites of the body (95% CI, 20.7—32.1%), but not to the pre-operative intensity of pain. Conclusion: Chronic pain after THA seems to be a significant problem in at least 12.1% of patients. Our results suggest that genetic and psychosocial factors are important for the develop- ment of chronic post-THA pain. Accepted for publication 14 November 2005 Key words: chronic pain; post-operative pain; risk factors; total hip arthroplasty (THA). # Acta Anaesthesiologica Scandinavica 50 (2006) T HE incidence of post-surgical pain is high after several operations, such as amputation, mastectomy, thoracotomy, sternotomy, gallbladder surgery and inguinal hernia repair (1, 2). Up to 60—80% of amputees experience phantom pain after amputation (3), and breast surgery is followed by chronic pain in 20—50% of patients (4). A similar high percentage of patients develop chronic pain after thoracotomy (5), sternotomy (6) and femoro- popliteal bypass surgery (7). Common operations, such as gallbladder surgery, inguinal hernia repair and Cesarean section, may also lead to chronic pain in approximately 12—30% of patients (8—10). The etiology behind the development of chronic pain after surgery is not fully known, but several risk factors have been identified (1). Pre-operative pain (11, 12) and acute post-operative pain (10, 13, 14) have been shown to increase the risk of chronic post-surgical pain. Intra-operative events, such as intra-operative nerve damage, may play a role in the development of chronic pain (15, 16), as well as genetic and various psychosocial factors (1). However, the relative importance of each of the above-mentioned risk factors for the development of chronic pain is not clear, and only a few data from well-controlled prospective studies exist. To gain more knowledge about post-surgical pain, we decided to study pain after total hip arthroplasty (THA) in a large-scale, register-based study for the following reasons. 1 Little is known about chronic pain after orthopedic surgery. 2 THA is a common surgical procedure. 3 Severe pre-operative pain is the primary indication for THA. 4 Early post-operative pain may be moderate/severe (17). 5 The risk of intra-operative nerve damage is low (18). Our aim was to identify various risk factors for the development of chronic pain, with specific attention being paid to the relationship between pre-operative pain, early post-operative pain and chronic hip pain. Acta Anaesthesiol Scand 2006; 50: 495—500 Copyright # Acta Anaesthesiol Scand 2006 Printed in Singapore. All rights reserved ACTA ANAESTHESIOLOGICA SCANDINAVICA doi: 10.1111/j.1399-6576.2006.00976.x 495