Persistent pain is common 1 year after ankle and wrist fracture surgery: a register-based questionnaire study

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1 British Journal of Anaesthesia, 116 (5): (2016) doi: /bja/aew069 Pain PAIN Persistent pain is common 1 year after ankle and wrist fracture surgery: a register-based questionnaire study K. D. Friesgaard 1,2, *, K. Gromov 3, L. F. Knudsen 1, M. Brix 4, A. Troelsen 3 and L. Nikolajsen 1,2 1 Danish Pain Research Center, Department of Clinical Medicine, Aarhus University, Noerrebrogade 44, Building 1A, Aarhus 8000, Denmark, 2 Department of Anaesthesiology, Aarhus University Hospital, Aarhus, Denmark, 3 Department of Orthopaedic Surgery, Copenhagen University Hospital Hvidovre, Copenhagen, Denmark, and 4 Department of Orthopaedic Surgery, Odense University Hospital, Odense C, Denmark *Corresponding author. k.friesgaard@clin.au.dk Abstract Background: Substantial literature documents that persistent postsurgical pain is a possible outcome of many common surgical procedures. As fracture-related surgery implies a risk of developing neuropathic pain and complex regional pain syndrome (CRPS), further studies investigating the prevalence and pain characteristics are required. Methods: All patients undergoing primary surgery because of ankle or wrist fracture at Hvidovre and Odense University Hospitals, Denmark, between April 15, 2013 and April 15, 2014, were identified from the Danish Fracture Database. A questionnaire regarding pain characteristics was sent to patients 1 yr after primary surgery. Results: Replies were received from 328 patients, of whom 18.9% experienced persistent postsurgical pain defined as pain daily or constantly at a level that interfered much or very much with daily activities, 42.8% reported symptoms suggestive of neuropathic pain, and 4.0% fulfilled the diagnostic patient-reported research criteria for CRPS. Conclusions: Persistent postsurgical pain 1 yr after wrist and ankle fracture surgery is frequent, and a large proportion of patients experience symptoms suggestive of neuropathic pain and CRPS. Patients should be informed about the substantial risk of developing persistent postsurgical pain. Future studies investigating risk factors for persistent postsurgical pain that include both surgically and conservatively treated fractures are required. Key words: chronic pain; orthopaedics; pain; postoperative Substantial literature documents that persistent postsurgical pain (PPSP) is a possible outcome of many common surgical procedures, with incidence rates varying from 5 to 85% dependent on the type of surgery. 1 The aetiology behind the development of PPSP is not fully understood, but numerous risk factors have been identified, including pre- and postoperative pain, intraoperative nerve damage, co-morbidities, age, type of anaesthesia, and genetic and psychosocial factors. 2 5 Wrist and ankle fractures are among the most common surgically treated fractures in adults. 6 Despite the high frequency, data on PPSP after orthopaedic surgery are scarce As fracture-related surgery implies a risk of developing neuropathic pain and complex regional pain syndrome (CRPS), further studies investigating the prevalence and risk factors of this type of surgery are required. The use of personal identity numbers in Denmark enables the linkage of register data from the Danish Fracture Database with Accepted: January 7, 2016 The Author Published by Oxford University Press on behalf of the British Journal of Anaesthesia. All rights reserved. For Permissions, please journals.permissions@oup.com 655

2 656 Friesgaard et al. Editor s key points Persistent pain after fracture, including complex regional pain syndrome (CRPS), can be a major problem. Patients from a national database were assessed for persistent pain 1 yr after injury. Of the 328 (54.7%) patients who responded, 62 (18.9%) had clinically significant pain. Further work is needed to understand persistent pain after fracture, to minimize long-term problems. questionnaire data and thus a long-term follow-up of a large number of patients who have undergone surgery for wrist or ankle fracture. 6 The aim of the present study was to investigate the prevalence, characteristics, and risk factors of PPSP 1 yr after wrist or ankle fracture surgery. We hypothesized that 10% of all patients experienced PPSP 1 yr after surgery, and that a considerable number of these patients would report symptoms suggestible of neuropathic pain and CRPS. Methods Patients All patients were recruited from the Danish Fracture Database (see description below). The inclusion criteria were primary surgery because of ankle or wrist fracture at Hvidovre and Odense University Hospitals, Denmark, between April 15, 2013 and April 15, 2014, and age 18 yr. Patients meeting these criteria were sent a postal questionnaire with an invitation letter and a stamped envelope for reply between June 1, 2014 and March 1, Thus, the time of follow-up was 1 yr (range, weeks). In order to reduce response bias, patients were urged to respond regardless of whether they had experienced pain or not. Questionnaires that were returned later than after 1 month were not included in data analysis. The study was approved by the Danish Data Protection Agency ( ; HVH :02768) and the Committee of the Danish Fracture Database. Studies based on questionnaires or registers do not require the approval of the regional or national Committee on Health Research Ethics in Denmark. Questionnaire data A questionnaire in Danish was developed for the study and included questions about pain located to the operated ankle or wrist within the last month. The frequency of pain was described as constant, daily, with daily intervals, or no pain. Patients with pain (i.e. all patients except those who answered no pain ) were also asked about pain intensity and pain characteristics. Pain intensity (average and worst) was described using a numerical rating scale (NRS) ranging from 0 to 10, with 0=no pain and 10=worst possible pain; and the impact of pain on daily activities was described as very much, much, some, little,or no. Pain characteristics were described using the interview version of the Douleur Neuropathique 4 Questions (DN4), including the following seven items: burning, painful cold, electric shocks, tingling, pins and needles, numbness, and itching. A score of one is given to each positive item and a score of zero to each negative item, and the total score is calculated as the sum. The cut-off value for the tentative diagnosis of neuropathic pain is a total score of three out of the seven items. 14 In addition, patients were asked whether they experienced decreased sensitivity to touch, pinprick (hypoaesthesia), or pain caused or increased by brushing (allodynia) the scar area. In order to detect possible symptoms of CRPS, the questionnaire also included questions about skin colour changes, temperature asymmetry, swelling, and restricted movement of the operated ankle/wrist. In order to maximize specificity, a tentative diagnosis of CRPS was made according to the Budapest research criteria, which include the above-mentioned features. 15 Patients who reported pain with an average pain intensity more than three on the NRS over the past month and who indicated that they experienced temperature asymmetry, skin colour changes, or both were contacted by telephone or (whichever was preferred by the patient) and asked more thoroughly about symptom appearance. The patients were also asked whether they had received a medical diagnosis of CRPS. Pain catastrophizing, quality of life, consumption of analgesics because of pain located to the operated wrist/ankle, reoperation rate, and pain problems elsewhere were assessed in all patients regardless of pain status. Pain catastrophizing was assessed by means of the 13-item Pain Catastrophizing Scale (PCS), which measures thoughts and feelings when experiencing pain. 16 Elements of the PCS include scores of magnification, rumination, and helplessness. Together, these elements provide an overall score of catastrophizing (each item on a scale from 0 to 4, with a maximal score of 52). Quality of life was assessed by the European Quality of Life Questionnaire (EQ5D). It is a widely used instrument for measuring self-rated health on a visual analog scale (VAS, 0 100) and five dimensions describing mobility, self-care, usual activities, pain/discomfort, and anxiety/ depression. 17 The primary outcome was PPSP, which we defined as pain experienced daily or constantly within the last month at a level that interfered much or very much with daily activities, based on the two questions related to the frequency and impact of pain on daily life. Danish Fracture Database Baseline patient and surgery-related data were collected from the Danish Fracture Database, which was established in 2011 as an online database for registration of all fracture-related surgery. 6 The data are entered into the database by the surgeon immediately after the surgery and include patient-related, traumarelated, and surgery-related factors. All fractures are classified according to the Orthopaedic Trauma Association/Arbeitsgemeinschaft für Osteosynthesefragen (OTA/AO) classification. 18 Nineteen hospitals across Denmark, covering 90% of the population, currently participate in Danish Fracture Database collaboration, with registered procedures. Data extracted from the database included age, sex, ASA score, fracture diagnosis (OTA/AO classification), Gustillio type (open vs closed), type of operation (open reduction and internal fixation vs external fixation), use of tourniquet (yes or no), perioperative complications (yes or no), and educational level of the surgeon and supervisor, if available. The follow-up data were obtained using the patient questionnaire. Data analysis and handling In order to find a 10% prevalence of chronic pain for each fracture with a 95% confidence level and a 5% margin of error, the estimated sample size (n) needed was: (1 0.1)/ =138 patients for each fracture. During the inclusion period, a total of 717 patients (including those who did not fulfil theinclusion

3 Persistent pain after fracture-related surgery 657 criterion of primary surgery) were operated at Hvidovre and Odense University Hospitals for ankle fracture (355 patients) and wrist fracture (362 patients). 6 To compensate for exclusion and a potentially low response rate, an inclusion period of 1 yr was chosen. If patients returned questionnaires with data missing on the two questions defining the primary outcome, these data were obtained by telephone interview. Otherwise, analysis was based on available data, and missing data were not treated as expected values. Data from the questionnaires were manually entered into Microsoft Access and subsequently merged with registry data. All statistical analyses were conducted using STATA version 13.1 (StataCorp, College Station, TX, USA). Categorical data are reported as number (percentage) with 95% confidence intervals (CIs) and compared using the χ 2 test. Medians with interquartile ranges (IQRs) are given for continuous skewed data and compared with the Mann Whitney U-test, whereas means with CIs for normally distributed data were compared with Student s unpaired t-test. The following predictive factors were used in the regression: age, sex, ASA score, fracture diagnosis (OTA/AO classification: wrist 23-A, 23-B, and 23-C; ankle 44A, 44B, and 44C), Gustillio type, type of operation (open reduction and internal fixation vs external fixation), use of tourniquet (yes or no), perioperative complications, and educational level of the surgeon and supervisor. A logistic regression model was used to assess whether these selected factors predicted the outcome of pain at follow-up. Factors were considered suitable for inclusion in the analysis if they could correct for unknown confounders (age, sex) or were clinically relevant and there were enough data to allow inclusion in analysis. All results were considered significant at P<0.05. Results The patient flow is presented in Fig. 1. Replies were received from 328 patients (response rate, 54.7%), of whom 193 patients were operated at Hvidovre University Hospital (ankle fracture, n=87; wrist fracture, n=104) and 137 at Odense University Hospital (ankle fracture, n=65; wrist fracture, n=72). Non-responders were more likely to be men (53.1 vs 39.5%, P=0.001) and younger [51.5 yr (95% CI ) vs 59.0 yr (95% CI ), P=0.0001] 599 patients operated for ankle and wrist fracture 330 patients answered questionnaire 2 patients with incomplete questionnaires 328 patients available for analysis 196 patients had pain at follow-up 132 (40.2%) patients had no pain at follow-up 62 (18.9%) patients had persistent pain* 134 (40.9%) patients had less severe pain 2 patients did not complete DN4 38 patients (61.3%) with possible neuropathic pain 45 patients (34.1%) with possible neuropathic pain Fig 1 Patient flow and proportion of patients with possible neuropathic pain. DN4, the neuropathic pain diagnostic questionnaire, Douleur Neuropathique 4 questions. *Persistent pain defined as pain experienced daily or constantly within the last month at a level that interfered much or very much with daily activities.

4 658 Friesgaard et al. than responders, whereas they did not differ with regard to any of the other variables extracted from the Danish Fracture Database. Only a few questionnaire data were missing, mainly answers about postoperative immobilization. The exact number of patients who answered each question is displayed next to each outcome in the tables. One hundred and thirty-two of 328 patients had not experienced pain located to the operated extremity within the last month (Table 1). In the remaining 196 patients, average and worst pain intensity (NRS) during the last month was 4 (IQR 3 6) and 6 (IQR 4 7), respectively. Sixty-two of the 196 patients (18.9%; 95% CI ) experienced PPSP defined as pain daily or constantly at a level that interfered much or very much with daily activities; 134 reported pain but less frequently or with less impact on daily life, or both. A higher proportion of patients with PPSP consumed analgesics daily compared with patients who had less severe or no pain [30.6% (95% CI ) vs 3.5% Table 1 Baseline characteristics of patients. CI, confidence interval; EQ5D, the European Quality of Life Questionnaire; IQR, interquartile range; NRS, numerical rating scale; VAS, visual analog scale All patients, n=328 n Percentage Age [yr (95% CI)] 58.9 ( ) Sex (male/female) 105/223 32/68 Department (Odense/Hvidovre) 137/191 42/58 Fracture (ankle/wrist) 152/176 46/54 Postoperative immobilization [weeks, n=258, median (95% CI)] 6.3 ( ) Pain intensity in the last month [NRS (0 10), n=196, median (IQR)] Average 4 (3 6) Worst 6 (4 7) Frequency of pain in the last month (n=328) None Not every day Every day Constantly Impact on daily life (n=328) None A little Some Much Very much EQ5D [any problems, n=317] Mobility Self-care Usual activities Pain/discomfort Anxiety/depression Self-rated health [VAS (0 100), 80 (60 90) n=306, median (IQR)] Pain catastrophizing scale [(PCS), 7(1 17) n=284, median (IQR)] Consumption of analgesics because of pain located to the operated wrist/ankle (n=318) Reoperation rate (n=328) Pain problems elsewhere (n=319) (95% CI ), P=0.001]. Patients with PPSP did not differ with regard to age [56.1 yr (95% CI ) vs 59.6 yr (95% CI ), P=0.13], pain problems elsewhere [51.7% (95% CI ) vs 39.5% (95% CI ), P=0.09], reoperation rate [14.5% (95% CI ) vs 8.6% (95% CI ), P=0.16] or duration of postoperative immobilization [7.2 weeks (95% CI ) vs 6.0 weeks (95% CI ), P=0.09] compared with patients who had less severe or no pain. Pain was the main cause of reoperation (65.6% of 32 patients), whereas joint malalignment (6.2%), infection (12.6%), neurovascular complications (6.2%), and suboptimal osteosynthesis (9.4%) accounted for the rest. Patients with ankle fracture were more likely to report PPSP compared with patients with wrist fracture [23.7% (95% CI ) vs 14.8% (95% CI ), P=0.04]. One hundred and ninety-four patients completed the DN4 interview, of whom 83 patients reported symptoms suggestible of neuropathic pain (42.8%; 95% CI ). Frequent symptoms were electric shocks (56.7%; 95% CI ) and pins and needles in the same area as the operated extremity (47.9%; 95% CI ). Thirty-eight of 62 patients with PPSP (61.3%; 95% CI ) reported symptoms suggestive of neuropathic pain (Table 2). Reviewing the questionnaires for symptoms of CRPS, 22 patients had constant pain with a pain intensity >3 on the NRS, temperature asymmetry, or colour changes. Attempts to contact six patients were unsuccessful. Of these, three fulfilled enough patient-reported criteria for CRPS based on the questionnaire alone. Of the remaining 16 patients, 10 patients fulfilled the diagnostic research criteria for CRPS. Only one patient had received a medical diagnosis of CRPS before the telephone contact. That is, in total 13 patients (4.0%; 95% CI ) fulfilled the diagnostic patient-reported research criteria for CRPS (all women). Their average pain intensity (NRS) during the last month was 8 (IQR 6 9). Eight patients with suspected CRPS had an ankle fracture. According to the OTA/AO classification, five patients were classified as 44-B and three patients as 44-C, suggesting articular involvement. A high proportion of patients with PPSP reported problems with their physical and mental health in the EQ5D (Fig. 2). Patients with PPSP had higher scores on the PCS compared with patients who had less severe pain [22.5 (IQR 10 35) vs 7 (IQR 2 16), P=0.0001] or no pain [22.5 (IQR 10 35) vs 2(IQR 0 9.5), P=0.0001]. Similar differences were found on rumination [9 (IQR 3 12) vs 3 (IQR 0 6), P= and 9 (IQR 3 12) vs 0 (IQR 0 4), P=0.0001], magnification [3 (IQR 1 7) vs 1 (IQR 0 3), P= and 3 (IQR 1 7) vs 0 (IQR 0 2), P=0.0001], and helplessness [10 (IQR 5 15) vs 4 (IQR 1 7), P= and 10 (IQR 5 15) vs 1 (IQR 0 3.5), P=0.0001]. None of the risk factors for PPSP used in the regression analysis could predict the occurrence of PPSP, except females with wrist fracture (odds ratio, 3.74 ( ), P=0.04). The data set was not suited for multivariate analysis because of the relatively small sample size. Discussion In this prospective questionnaire-based cohort study, we found that 18.9% (95% CI ) of patients experienced PPSP 1 yr after surgically treated ankle or wrist fracture, with a high proportion of patients experiencing symptoms suggestive of neuropathic pain. In addition, 4.0% (95% CI ) fulfilled the diagnostic patient-reported research criteria for CRPS. Self-reported health measures (EQ5D and PCS) were significantly lower among patients with PPSP than among patients without PPSP. This suggests that long-term complications after these fractures are

5 Persistent pain after fracture-related surgery 659 Table 2 Pain characteristics. Persistent pain is defined as pain experienced daily or constantly and with much or very much impact on daily activities. Less severe pain is pain of any intensity but not present daily or constantly, or with no, little, or only some impact on daily activities. DN4, the neuropathic pain diagnostic questionnaire, Douleur Neuropathique 4 questions ; IQR, interquartile range; NRS, numerical rating scale. *Derived from the first seven questions in the DN4 interview (burning, painful cold, electric shocks, tingling, pins and needles, numbness, and itching) Patients with less severe pain (n=132) Patients with persistent pain (n=62) n Percentage n Percentage P-value Pain intensity in the last month (NRS, 0 10), median (IQR): Average 3 (2 5) 6(5 8) P= Worst 4 (3 7) 7.5 (6 9) P= DN4: does the pain have one or more of the following characteristics? Burning P=0.29 Painful cold P=0.03 Electric shocks P=0.006 DN4: is the pain associated with one or more of the following symptoms in the same area? Tingling P=0.002 Pins and needles P=0.01 Numbness P=0.006 Itching P=0.16 Hypoaesthesia to touch P=0.24 Hypoaesthesia to prick P=0.04 In the painful area, can pain be caused or increased by brushing? P=0.002 Neuropathic pain, at least three out of seven questions* P= No pain Less severe Persistent pain Any problem (%) VAS (0 100) Mobility* Self-care* Usual activities* Pain/discomfort* Anxiety/depression* VAS* Fig 2 EQ5D, the European Quality of Life Questionnaire. Perceived health was rated on a visual analog scale (VAS, 0-100; 0=worst imaginable health state, 100=best imaginable health state). *P-value <0.05.

6 660 Friesgaard et al. common and that patients should be informed thoroughly about this before surgery. The prevalence of PPSP varies according to the definition and type of surgery, and unfortunately, there are no validated procedure-specific methods to capture PPSP. Most published data on PPSP with or without a neuropathic component focus on thoracic, breast, abdominal, and gynaecological surgery, whereas the orthopaedic field mainly focuses on elective surgery In a recent study of 1305 patients who had undergone 25 different orthopaedic surgical procedures, 48% had PPSP 3 months after surgery. The prevalence of PPSP for fracture-related surgery was 61%, and a neuropathic component was reported in 43% of patients. Persistent postsurgical pain was defined as NRS 1 at rest 3 months after surgery, and the information about the neuropathic pain was obtained from the DN4 interview. 13 The prevalence of PPSP in our study was lower, presumably reflecting a longer follow-up period and stricter definition. However, it can be argued that the follow-up period of 3 months used in the other study is too short to evaluate the true presence of PPSP after surgical procedures, because full recuperation cannot be expected so quickly even after uncomplicated surgical procedures. A debilitating complication seen after trauma, surgery, or both to the extremities is the development of CRPS. In our study, 4% fulfilled the diagnostic patient-reported research criteria for CRPS. The incidence of CRPS depends crucially on the diagnostic criteria used. In a study of 596 patients with mixed fractures (wrist, scaphoid, ankle, or metatarsal), 7% developed CRPS according to the most recent International Association for the Study of Pain (IASP) criteria. The upper extremity was affected in 52.2% of patients and the lower extremity in 47.8%. Dislocation, an intra-articular fracture, and the location of the fracture (ankle) contributed significantly to the prediction of CRPS. 12 In our study, eight of 13 patients with CRPS had an ankle fracture, and all fractures were partly or completely articular (six patients OTA/AO classified as 44-B and two patients as 44-C). We found that PPSP after surgery was associated with impaired quality of life and more symptoms of anxiety and depression, which is in accordance with other studies. For example, a recent French nationwide survey on 3165 persons showed that subjects with chronic pain and neuropathic characteristics presented greater impairment of quality of life and sleep and more symptoms of anxiety and depression than the general population. 20 Given that our results arose from a selected patient cohort, the findings should be interpreted with caution. The parameters from the Danish Fracture Database could not predict the occurrence of PPSP, presumably because of the small sample size. Previous studies have found an association between outcome and risk factors such as age, ASA classification, open fracture, and severity of fracture. It is unknown how the choice of surgical technique affected the outcome, because we only investigated surgically treated fractures. In adults with surgically fixated wrist fractures, the proportion of fractures treated with open reduction and internal fixation has increased from 16% in 2004 to 70% in 2010, at the expense of the use of closed reduction and external fixation, which has decreased from 71 to 16% during this period. 23 Such changes in treatment modalities can potentially change not only complication rates with respect to reoperations, but also with respect to patient-reported outcomes and persistent pain. However, in our study, we were not able to detect a difference in the prevalence of PPSP after surgically treated wrist and ankle fractures, depending on the surgical treatment modality. Our study has some limitations. First, the prevalence of PPSP depends on the definition applied. The IASP has defined PPSP as a persistent pain state that is apparent more than 2 months after surgery that cannot be explained by other causes and does not arise from a pre-existing problem. We used another definition in an attempt not to overestimate the prevalence of PPSP. Ideally, we should have used a validated procedure-specific assessment scale. Second, despite a good sensitivity (81.6%) and specificity (85.7%), the modified self-administered DN4 questionnaire was not followed up with a clinical examination, which limits the validity of our results. If a clinical examination had been included, the prevalence of PPSP and its characteristics could have been verified. However, this was not possible because of the large number of patients and the large geographical inclusion area. Moreover, a prospective investigation of well-known pre-, intra-, and postoperative risk factors would have elucidated how PPSP develops after wrist and ankle fracture surgery and who is at greater risk of developing PPSP. 24 Third, our response rate was only 54.7%, and differences between responders and non-responders might have introduced bias. The response rate was, however, comparable with similar studies Fourth, the Danish Fracture Database only registers surgically treated fractures; therefore, we cannot compare our results with results on the development of persistent pain after conservatively treated ankle or wrist fractures and support one treatment choice over another. Previous studies have, however, failed to find any difference in outcome between conservatively and surgically treated ankle and wrist fractures Further studies are required to investigate the role of surgical treatment of a fracture for the development of PPSP, CRPS, or both. Fifth, we did not explore the impact of the quality of postoperative pain treatment on the development of PPSP, because we were unable to retrieve patient data from the early postoperative phase. Sixth, in order to ensure data quality, we decided only to include patients from orthopaedic departments where the Danish Fracture Database was fully implemented. At the time of planning the study, this was the case in only two of 19 contributing Danish hospitals, and therefore, the results do not reflect patient data from the entire present database. Last, none of the risk factors for PPSP extracted from the Danish Fracture Database could predict the occurrence of PPSP, which is most likely to be because of the small sample size. However, the study was powered to support only our primary outcome. Conclusion In this prospective questionnaire-based cohort study, 18.9% of all patients experienced PPSP 1 yr after wrist or ankle fracture surgery, and a high proportion of patients experienced symptoms suggestive of neuropathic pain. In addition, 4.0% fulfilled the diagnostic patient-reported research criteria for CRPS. Patients undergoing surgical treatment for wrist and ankle fractures should be informed about the substantial risk of developing PPSP. Future studies should include a higher number of patients and investigate risk factors for PPSP after both surgically and conservatively treated fractures. Authors contributions Conception and design: K.D.F., K.G., L.K., M.B., A.T., L.N. Analysis and interpretation of data: K.D.F., K.G., L.N. Drafting the article: K.D.F. Critical revision of the article for important intellectual content: K.G., L.K., M.B., A.T., L.N. Final approval of the version to be published: K.D.F., K.G., L.K., M.B., A.T., L.N.

7 Persistent pain after fracture-related surgery 661 Declaration of interest None declared. Acknowledgements The authors would like to thank Helle O. Andersen (Danish Pain Research Center, Aarhus, Denmark) for English language revision. Funding Small project grants from The Danish Society of Polio and Accident Victims and The Health Research Fund of Central Denmark Region. References 1. Macrae WA. Chronic post-surgical pain: 10 years on. Br J Anaesth 2008; 101: Perkins FM, Kehlet H. Chronic pain as an outcome of surgery. A review of predictive factors. Anesthesiology 2000; 93: Kehlet H, Jensen TS, Woolf CJ. Persistent postsurgical pain: risk factors and prevention. Lancet 2006; 367: VanDenKerkhof EG, Peters ML, Bruce J. Chronic pain after surgery: time for standardization? A framework to establish core risk factor and outcome domains for epidemiological studies. Clin J Pain 2013; 29: Borsook D, Kussman BD, George E, Becerra LR, Burke DW. Surgically induced neuropathic pain: understanding the perioperative process. Ann Surg 2013; 257: Gromov K, Brix M, Kallemose T, Troelsen A. Early results and future challenges of the Danish Fracture Database. Dan Med J 2014; 61: A Nikolajsen L, Brandsborg B, Lucht U, Jensen TS, Kehlet H. Chronic pain following total hip arthroplasty: a nationwide questionnaire study. Acta Anaesthesiol Scand 2006; 50: Lundblad H, Kreicbergs A, Jansson KA. Prediction of persistent pain after total knee replacement for osteoarthritis. J Bone Joint Surg Br 2008; 90: Beswick AD, Wylde V, Gooberman-Hill R, Blom A, Dieppe P. What proportion of patients report long-term pain after total hip or knee replacement for osteoarthritis? A systematic review of prospective studies in unselected patients. BMJ Open 2012; 2: e Liu SS, Buvanendran A, Rathmell JP, et al. A cross-sectional survey on prevalence and risk factors for persistent postsurgical pain 1 year after total hip and knee replacement. Reg Anesth Pain Med 2012; 37: Bjørnholdt KT, Brandsborg B, Søballe K, Nikolajsen L. Persistent pain is common 1 2 years after shoulder replacement. Acta Orthop 2015; 86: Beerthuizen A, Stronks DL, Van t Spijker A, et al. Demographic and medical parameters in the development of complex regional pain syndrome type 1 (CRPS1): prospective study on 596 patients with a fracture. Pain 2012; 153: Fuzier R, Rousset J, Bataille B, Salces YNA, Magues JP. One half of patients reports persistent pain three months after orthopaedic surgery. Anaesth Crit Care Pain Med 2015; 34: Bouhassira D, Attal N, Alchaar H, et al. Comparison of pain syndromes associated with nervous or somatic lesions and development of a new neuropathic pain diagnostic questionnaire (DN4). Pain 2005; 114: Harden RN, Bruehl S, Stanton-Hicks M, Wilson PR. Proposed new diagnostic criteria for complex regional pain syndrome. Pain Med 2007; 8: Sullivan MJ, Thorn B, Haythornthwaite JA, et al. Theoretical perspectives on the relation between catastrophizing and pain. Clin J Pain 2001; 17: EuroQol Group. EuroQol a new facility for the measurement of health-related quality of life. Health Policy 1990; 16: Marsh JL, Slongo TF, Agel J, et al. Fracture and dislocation classification compendium : Orthopaedic Trauma Association Classification, Database and Outcomes Committee. J Orthop Trauma 2007; 21: S Haroutiunian S, Nikolajsen L, Finnerup NB, Jensen TS. The neuropathic component in persistent postsurgical pain: a systematic literature review. Pain 2013; 154: Attal N, Lanteri-Minet M, Laurent B, Fermanian J, Bouhassira D. The specific disease burden of neuropathic pain: results of a French nationwide survey. Pain 2011; 152: SooHoo NF, Krenek L, Eagan MJ, Gurbani B, Ko CY, Zingmond DS. Complication rates following open reduction and internal fixation of ankle fractures. JBoneJointSurgAm 2009; 91: Navarro CM, Pettersson HJ, Enocson A. Complications after distal radius fracture surgery: results from a Swedish nationwide registry study. J Orthop Trauma 2015; 29: Wilcke MK, Hammarberg H, Adolphson PY. Epidemiology and changed surgical treatment methods for fractures of the distal radius: a registry analysis of 42,583 patients in Stockholm County, Sweden, Acta Orthop 2013; 84: Kehlet H, Rathmell JP. Persistent postsurgical pain: the path forward through better design of clinical studies. Anesthesiology 2010; 112: Johansen A, Romundstad L, Nielsen CS, Schirmer H, Stubhaug A. Persistent postsurgical pain in a general population: prevalence and predictors in the Tromsø study. Pain 2012; 153: Donken CC, Al-Khateeb H, Verhofstad MH, van Laarhoven CJ. Surgical versus conservative interventions for treating ankle fractures in adults. Cochrane Database Syst Rev 2012; 8: CD Ju JH, Jin GZ, Li GX, Hu HY, Hou RX. Comparison of treatment outcomes between nonsurgical and surgical treatment of distal radius fracture in elderly: a systematic review and metaanalysis. Langenbecks Arch Surg 2015; 400: Handling editor: L. Colvin