Accepted Manuscript Title: The Effect of Preoperative Intra-Articular Methylprednisolone on Pain after TKA: a Randomized Double-Blinded Placebo Controlled Trial in Patients with High-Pain Knee Osteoarthritis and Sensitization Author: Iben E. Luna, Henrik Kehlet, Claus M. Jensen, Thorbjørn G. Christiansen, Thomas Lind, Snorre L. Stephensen, Eske K. Aasvang PII: DOI: Reference:

S1526-5900(17)30674-0 http://dx.doi.org/doi: 10.1016/j.jpain.2017.07.010 YJPAI 3451

To appear in:

The Journal of Pain

Received date: Revised date: Accepted date:

24-4-2017 22-6-2017 25-7-2017

Please cite this article as: Iben E. Luna, Henrik Kehlet, Claus M. Jensen, Thorbjørn G. Christiansen, Thomas Lind, Snorre L. Stephensen, Eske K. Aasvang, The Effect of Preoperative Intra-Articular Methylprednisolone on Pain after TKA: a Randomized Double-Blinded Placebo Controlled Trial in Patients with High-Pain Knee Osteoarthritis and Sensitization, The Journal of Pain (2017), http://dx.doi.org/doi: 10.1016/j.jpain.2017.07.010. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

The effect of preoperative intra-articular methylprednisolone on pain after TKA A randomized double-blinded placebo controlled trial in patients with high-pain knee osteoarthritis and sensitization Iben E. Luna1,2,3*, Henrik Kehlet1,2, Claus M. Jensen3, Thorbjørn G. Christiansen3, Thomas Lind3, Snorre L. Stephensen3, Eske K. Aasvang1,2

1. Section of Surgical Pathophysiology, Rigshospitalet, University of Copenhagen, Denmark. 2. The Lundbeck Centre for fast-track Hip and Knee Arthroplasty, Denmark 3. Dep. of Orthopaedics, Gentofte-Herlev Hospital, University of Copenhagen, Denmark. *

Corresponding author: Iben E. Luna, Rigshospitalet, University of Copenhagen, Blegdamsvej 9, 2100

Copenhagen Ø, Denmark. Email:[email protected]. # 0045 3545 0802. Authors email addresses: [email protected], [email protected], [email protected], [email protected], [email protected], [email protected], [email protected]. Disclosure: The authors declare no conflict of interest. The study was supported by a grand from the Lundbeck Foundation, Hellerup Denmark (grant number: R25-A2702). The foundation is independent of the pharmaceutical company Lundbeck a/s and was not involved in designing or conducting the study.

Running title: Intra-articular methylprednisolone for TKA pain.

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Highlights   

Preoperative intraarticular steroid does not reduce acute post-TKA pain. Intraarticular steroid reduces preoperative joint IL-6. Intraarticular steroid does not reduce postoperative sensitization.

Abstract: In a randomized, double-blinded, placebo controlled trial, we investigated the postoperative analgesic effect of a single intra-articular injection of 40 mg methylprednisolone acetate (MP) administered one week prior to total knee arthroplasty (TKA). Forty-eight patients with high pain osteoarthritis (≥ 5 NRS during walk) and sensitization (pressure pain threshold < 250 kPa), aged 50 to 80 years and scheduled for primary unilateral TKA under spinal anaesthesia were included. The primary outcome was the proportion of patient with moderate/severe pain during a 5 meter walk test 24 hours postoperatively. Secondary outcomes included pain at 48 hours, during the first 14 days, sensitization (quantitative sensory testing with pressure pain threshold and wind up from temporal summation) and inflammatory changes (systemic CRP, intraarticular IL-6). No difference in proportion of patients with moderate/severe pain was found between MP/placebo groups at 24 hours (67% and 74%, χ2=0.2, p=0.63, odds ratio 0.7, 95% CI 0.2 to 2.8) or at 48 hours (57% and 68%, χ2=0.5, p=0.46, odds ratio 0.6 95% CI 0.2 to 2.3), and no difference between groups in postoperative sensitization was found (p > 0.4) despite reduced preoperative intra-articular inflammation (IL-6) in the MP group vs. placebo (median change in IL6: -70 pg/mL [IQR -466 to 0] vs. +32 pg/ml [IQR -26 to 75], p= 0.029). Alternative central or peripheral analgesic interventions in this high-risk group are required.

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Perspective: Peripherally driven inflammatory pain and nociceptive changes prior to TKA has been suggested a cause for increased acute postoperative pain. However, preoperative intra-articular MP in patients with high pain osteoarthritis and sensitization did not reduce acute post-TKA pain or sensitization despite a preoperative reduction of intra-articular inflammatory markers. The study was registered at ClinicalTrials.gov (NCT02253966) prior to patient enrolment. Keywords: Total knee arthroplasty, osteoarthritis, inflammation, postoperative pain, methylprednisolone.

Introduction: Acute pain after total knee arthroplasty (TKA) is a substantial clinical problem with 75% of patients having moderate-severe pain on the first postoperative day and 30-40% after 2 weeks.3,13 Aside from the evident discomfort, pain has implications for recovery and is correlated to the development of persistent postsurgical pain.20,23-25 Intense preoperative pain has been associated with acute post-TKA pain,22,27 and in 35 % of patients with knee-osteoarthritis, preoperative pain is seen along with nociceptive changes including both central and peripheral sensitization.32,43,50,52 The underlying pathophysiological mechanisms for pain and hyperalgesia are not fully clarified, but in some patients central sensitization may be caused by peripheral nociceptive input and consequently potentially reversible if treated.8,19 The level of intra-articular inflammation in the knee has been correlated to both pre- and post-operative pain16,20,36,44 and physical function;45,49 suggesting an important role for inflammatory driven nociception in pre- and post TKA pain.5,7,20,35,52 Intra-articular methylprednisolone acetate is well-established to reduce pain in knee osteoarthritis.9 However, the analgesic effect of pre-operative administration of intra-articular methylprednisolone acetate on acute post-TKA pain has not been tested, although both intra-articular administration in arthroscopic

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surgery38,39 and periarticular31,33 and systemic30 administration in TKA have been shown to reduce postoperative pain. A preoperative downregulation of the intra-articular inflammation in patients with high-pain osteoarthritis and sensitization could potentially serve as a stratified preventive analgesic strategy in patients less responsive to the current standardized analgesic regimen and improve outcome in this subgroup of patients.32,50,52 Thus, we hypothesized that a single intra-articular dose of 40 mg methylprednisolone acetate administered one week prior to TKA would reduce acute postoperative pain in patients with preoperative high-pain kneeosteoarthritis and central sensitization.

Methods: Patients and study design: This prospective, randomized, placebo controlled, double-blinded clinical trial was approved by the Danish medicine agency (EudraCT nr. 2014-002744-40), the Danish Regional Ethics Committee (H-3-2014-089) and the Danish data protection agency and was registered at ClinicalTrials.gov (NCT02253966) prior to patient enrolment. It was conducted in accordance to the Helsinki declaration and reported following the CONSORT recommendations. Patients were consecutively included after verbal and written informed consent from the department of orthopedic surgery Gentofte University Hospital, Copenhagen, Denmark, from January 2015 to Marts 2016. Criteria for inclusion were planned primary unilateral TKA for osteoarthritis under spinal anesthesia, age 50 to 80 years, self-reported pain during walk for 10 minutes ≥ 5 on a numeric rang scale (NRS) from 0 to 10 (0 = no pain, 10 = worst pain imaginable), pressure pain threshold < 250 kPa on the volar surface of the dominant forearm (two standard deviations under the mean pressure pain threshold in a non-osteoarthritic population51) and ability to understand Danish. Criteria for exclusion were allergies or contraindications toward methylprednisolone or the analgesic regime, daily use of glucocorticoids, infection or

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immunodeficiency, insulin treated diabetes, potent anticoagulant treatment, pregnancy, alcohol abuse, American Society of Anesthesiologists classification > 3 or psychological or neurological disease hindering testing. The Danish capital regions hospital- pharmacy generated a random allocation sequence and prepared 48 identically looking medicine boxes consecutively labeled with study-ID numbers. 24 contained active treatment (40 mg methylprednisolone acetate47 (Depo-medrol®) (40 mg/ml) + 100 mg lidocaine (20 mg/ml) + 4 ml isotonic saline: a total of 10 ml) and 24 contained placebo (100 mg lidocaine (20 mg/ml) + 5 ml isotonic saline: a total of 10 ml). Patient information and enrolment, study-medicine administration and data collection were performed by the primary investigator (IL), and patients were consecutively assigned the next available study-ID number after inclusion. Upon administration of study medicine, the seal of the corresponding medicine box was broken by a research-nurse not otherwise involved in the study and the active treatment or placebo was prepared and delivered to the primary investigator in a syringe blinded by application of two sterile patches. Medicine boxes were kept at the orthopedic ward along with sealed envelopes with information of a given patients allocation in case of a need for unblinding. Surgery was performed by one of four orthopedic surgeons at consultant level specialized in knee arthroplasty. Patients, investigators, surgeons and care providers were all blinded to the patient’s allocation. Upon completion of data collection, the allocation to group A or group B was revealed by the hospital pharmacy and by termination of statistics and manuscript writing, the allocation to active treatment or placebo unblinded. Administration of study medicine: With no previous data on preoperative intra-articular corticosteroid prior to TKA, the timing and the dose of the intervention was based on conservative treatment standards. The study medicine was administered 7 to 9 days prior to TKA, since maximum effect of i.a. methylprednisolone acetate is seen after one week,9 and the dose chosen in accordance with usual practice in the literature9 and from local standards in the hospital were the study was undertaken. After subcutaneous installation of 5 ml 2% lidocaine a

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superolateral retropatellar knee-puncture was performed under sterile conditions and synovial fluid aspirated for IL-6 analyses. Leaving the cannula in situ, the intra-articular administration of study medicine was performed, after which the patient was observed for acute adverse events for 20 minutes. Data collection: Data on age, gender, height, weight, preoperative pain and opioid consumption was collected at inclusion. Prior to surgery patients filled questionnaires including the validated pain catastrophizing scale (PCS)42 and hospital anxiety and depression scale (HADS)56 to characterize their psychological profiles. PCS rates pain coping strategies from 0 to 52 with 0 indication no catastrophizing and 52 maximum catastrophizing. HADS rates anxiety and depression on two subscales from 0 to 21 with 0 indicate no risk and 21 high risk of anxiety or depression. On each subscale patients are classified as having no risk of anxiety / depression (07), possible risk of anxiety / depression (8-10) or severe risk of anxiety / depression (11-21). Data were collected pre- and postoperatively with testing 7 and 1 days prior to TKA, on the day of surgery and on day 1 and 2 after TKA. In addition patients filled out a diary on pain and opioid consumption from day 1 to day 14 (figure 1). Adverse events to the study medicine were monitored by revision of patient charts for any related contacts with hospitals or emergency rooms 3 months after surgery and by a physical examination of the knee performed by the orthopedic surgeon at the 12 weeks follow up visit. Pain: The primary outcome measure was proportion of patients with moderate-severe pain during a standardized 5 meters walk test 24 hours after surgery.29 Patients were asked to walk as fast as possible allowing use of a walking aid if necessary and to rate their knee-pain on a 0-10 NRS (0 = no pain, 10 = worse pain imaginable) when taking the last step. Walk related pain and with a predefined maximum acceptable pain response was chosen due to the association to functional recovery.17,41 Secondary outcomes included: post-intervention pain 1 day prior to TKA (5 meters walk test), postoperative pain at 48 hours (5 meters walk test), pain recorded in a patient filled diary with daily ratings on a 0 to 10 NRS for: pain during walk, at

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rest, at worse and at average from day 1 to day 14 after TKA, use of opioids collected from the medical chart during hospitalization and from the diary after discharge. Inflammation: Intra-articular level of IL-6 was measured in two samples of synovial fluid. One collected prior to administration of the study medicine (7 to 9 days before TKA) and one taken by the orthopedic surgeon in the operating theater prior to incision. The synovial fluid was centrifuged and spun, supernatant removed and samples frozen within 30 minutes from extraction. By termination of data-collection the synovial fluid was thawed and hyaluronic acid degraded with hyaluronidase (Sigma-Aldrich ApS, Brøndby, Denmark) to reduce viscosity and secure a homogeneous solution. IL-6 concentrations were quantified with the human IL-6 Quantikine Immunoassay (R&D Systems, Bio-Teche, Abingdon,UK). For each sample double assessments were made and the median IL-6 level reported. Plasma CRP was measured on the day of administration of study medicine, on the day of surgery and at postoperative day 2 (figure 1). Nociceptive characteristics: Quantitative sensory function was examined 7 and 1 day before surgery and 2 days after surgery. Pressure pain threshold (PPT) was tested on the volar surface of the dominant forearm (general sensitization) and on the medial site of the knee to be operated (local sensitization), using a pressure algometer with a patient controlled switch (Somedic, Horby, Sweeden).51 A 1 cm2 probe was held at a perpendicular angle to the skin applying an increasing force at a rate of 10 kPa per second until a transition from sensation of pressure to pain was felt by the patient or until a maximum of 400 kPa was reached. This limit was chosen based on previous experiences to avoid skin injury prior to surgery. Three tests were done at each examination site, and the average calculated for each test location.52 Temporal summation to mechanical stimulation (wind-up): was tested on the volar surface of the nondominant forearm using seventeen progressively rigid von Frey fibers with buckling force from 0.04 to 100 grams (Stoelting, Illinois, USA). The tactile pain detection threshold was determined as the smallest fiber eliciting a sensation of pain in two repeated pinpricks. Subsequently, repetitive stimulation at 2 Hz for 60 seconds was performed with this fiber, while the patient was asked to assess pain on a 0-10 NRS for each

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10 seconds of stimulation. The wind-up was calculated as the difference in pain during the 60 seconds (wind-up = NRSt60 – NRSt0).1 Anesthesia and analgesia: TKA was performed in a standardized fast track set-up by an orthopedic consultant using a medial approach and tourniquet under spinal anesthesia with hyperbaric bupivacaine (0.5%, 2.0-3.0 ml) and supplemental propofol sedation (1 to 5 mg per kg per hour) as needed. Local infiltration analgesia was administered intraoperatively.4 The analgesic regimen included preoperative treatment with acetaminophen 1 g and celecoxib 400 mg approximately one hour prior to surgery and postoperative treatment with acetaminophen 1 g / 6 hours, ibuprofen 400 mg / 8 hours and oxycodone as needed throughout the study period. In case of opioidresistant pain, an adductor canal block (ACB) was performed. Hospital discharge followed previously described well-defined medical and physiotherapeutic fast-track criteria.21 Statistics: The sample size was estimated based on a previous study with a similar protocol for anesthesia, analgesia and surgical technique, which found 75 % of patients having moderate / severe pain (NRS > 3) upon ambulation 24 hours after TKA. A 50% reduction in proportion of patients with moderate-severe pain 24 hours after TKA was considered clinically relevant. To achieve a power of 80%, a 5% significance level and a 10% expected drop out, 48 patients (2 x 24) were included. The primary outcome measure was proportion of patients with moderate-severe pain during the standardized 5 meters walk test 24 hours after surgery. Data were dichotomized as mild pain (NRS 0-3) or moderate-severe pain (NRS 4-10) and between groups difference tested with the chi-square test. Analyses

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were also performed for pain during the 5 meters walk test 1 day prior to surgery and 48 hours after surgery. Data on opioid consumption from day 1 to day 14 were converted to equipotent amount of per oral morphine (mg) and area under the curve (AUC) for opioid and diary data on pain day 1 to day 14 after surgery calculated. Change in synovial-IL-6 concentration from before until 1 week after application of MP was calculated (∆IL6 = day-1 minus day-7). Plasma-CRP was measured on day -7 and change until day -1 and day +2 calculated. Changes in sensory function (pressure pain threshold and wind-up pain) was assessed as change after administration of study medicine (∆QST-preoperative=day-1 minus day-7) and change after TKA (∆QSTpostoperative=day+2 minus day-7). For pressure pain threshold positive values indicated an increased threshold i.e. reduced sensitization, whereas positive values for wind-up ratio indicated an increased temporal summation pain and thus increased sensitization. Continuous numeric outcome data were tested for normal distribution visually and by the KolmogorovSmirnov test. This was accepted for AUC for diary pain scores and for AUC for opioid consumption after log2 conversion but not for data on inflammation or sensory function. Data are presented as mean with standard deviation (SD) or median with interquartile range (IQR: the 25th and 75th percentile) and between group differences were tested with the unpaired t-test or the Mann-Whitney rank-sum test when appropriate. Aiming to assess the hypothesized association between intra-articular inflammation, sensitization and acute post-operative pain, per protocol analyzes were performed, but with intention to treat analyzes added for the primary outcome measure. Data were analyzed in SAS version 9.4 and graphs and figures constructed in IBM SPSS statistics 22. A 5% significance level was chosen.

Results: 264 patients were assessed for eligibility and 48 were included in the study (figure 2).

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All included patients received their allocated intervention. 22 in the MP-group and 21 in the placebo group were tested for pain during the 5 meters walk test 24 hours after surgery (primary outcome measure) and analyzed according to the intension to treat principles. In the MP-group one patient had surgery postponed 6 weeks due to infection in a finger and one patient had missing data. In the placebo-group one patient was re-operated on the first post-operative day due to a dislocation of the prosthesis-insert causing a rupture of the cruciate ligaments, one patients withdrew his informed consent on the day of surgery and one patient had missing data (figure 2). Additional 3 patients were excluded from per protocol analyzes due to violation of the anesthetic and analgesic protocol: two patients were intraoperatively converted to general anesthesia (one in each group) and one was treated with preoperative systemic high dose methylprednisolone (placebo). Finally, one patient failed to complete the preoperative HADS questionnaire and one patient failed to return the pain and analgesic diary (figure 2). The patients in the study had a mean age of 68 years (range 50 - 80) and the male:female ratio was 17:23. Baseline characteristics on demographics, pain, nociception, inflammation and psychological profile were similar in the two treatment groups, aside from sex, where 11 of 17 men were allocated in the placebo group (table 1). Six patients (2 MP and 4 placebo) were treated with an ACB due to severe opioid resistant pain on the first post-operative day and 4 (2 in each group) had their opioid treatment converted from oxycodone to ketobemidone before discharge due to insufficient effects from the standard regimen. Pain: There was no statistically significant difference in moderate-severe pain during the 5 meters walk test for patients treated with MP or placebo 24 hours after surgery (67% and 74% moderate-severe pain respectively, χ2=0.2, p=0.63, odds ratio 0.7, 95% CI 0.2 to 2.8) or 48 hours after surgery (57% and 68% moderate-severe pain respectively, χ2=0.5, p=0.46, odds ratio 0.6, 95% CI 0.2 to 2.3) (table 2). Nor was there a statistically significant between group difference in median NRS during the 5 meters walk test 24 hours after surgery (median NRS 4 [IQR 3 to 7] and NRS 5 [IQR 3 to 6] respectively, p=0.73) or 48 hours after

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surgery (median NRS 4 [IQR 2 to 4] and NRS 4 [IQR 3 to 5] respectively, p=0.37). Results were equally insignificant when analyzed according to intention to treat principles. There was no significant between-group difference in diary-reported pain during walk, on average, at worse or at rest from postoperative day 1 to 14 (table 2) or in opioid-consumption from day 1 to day 14 (mean 893 mg/14 days vs 1111 mg/14 days, mean difference -218 mg/14days (95% CI -544 to 106), p=0.19) (table 2, figure 3 and 4). No between-group difference in pain during the 5 meters walk test one day prior to surgery was observed (odds ratio 0.3, 95% CI 0.0 to 1.8, p=0.23). Inflammation: Analyzes of change in synovial IL-6 level were feasible in 35 patients (8 patients had a “dry knee” at time of administration of study medicine, 4 patients at the day of surgery, and 1 sample was lost due to technical difficulties in the laboratory). A significant decrease in intra-articular IL-6 was observed in the MP group compared to the placebo group (median ∆IL6 = -70 pg/mL [IQR -466 to 0] vs. +32 pg/ml [IQR -26 to 75], MP vs. placebo respectively, p= 0.029) (figure 5). No between group differences were seen for plasma-CRP neither from prior to administration of study medicine until day of surgery (median ∆CRP = 0 mg/L [IQR -1 to 1] vs. 1 mg/L [IQR 0 to 2], MP vs. placebo, respectively, p=0.327), or between prior to injection until postoperative day 2 (median ∆CRP = 198 mg/L [IQR 144 to 231] vs. 162 mg/L [IQR 82 to179], MP vs. placebo, respectively, p=0.130). Nociceptive characteristics: The study-intervention had no significant effect on QST measurements from day 7 prior to surgery till day 2 after surgery (table 3). However, from day 7 till day 1 prior to surgery, there was a significant between groups difference in median change in wind-up with patients treated with MP having increased pain during

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the testing at day -1 (increased central sensitization) (median change in NRS 2 (IQR 0 to 3) and 0 (IQR -1 to 1), respectively, p=0.03). Likewise, a nonsignificant trend was seen for pressure pain algometry tested on the

medial side of the knee to be operated at day 7 and 1 prior to surgery with decreased PPT in the MP-group (increased peripheral sensitization) (table 3). Adverse events and follow up: Five patients had an in hospital length of stay > 4 post-operative days. One patient (placebo group) was admitted for 9 days with disperse bullae on the surgical-leg and observation for erysipelas. He was treated with intravenous dicloxacillin for 5 days and subsequently per oral flucloxacillin for 20 days without surgical soft tissue revision. There were no clinical or biochemical signs of infection at the 12 weeks follow up examination. One patient was admitted for 14 days and discharged to a rehabilitation home due to development of a pulmonary embolism (MP group) and one patient 6 days due to a deep vein thrombosis (placebo group). Finally two patients were admitted for 6 days due to severe postoperative pain and inadequate mobilization (one in each group). During the three month follow up, two patients had a knee manipulation under anesthesia (brisement forcé) (one in each group) and one patient in the MP group with known ischemic heart disease and arrhythmias died at day 87 due to sustained nonconvertible ventricular fibrillation.

Discussion: This is the first study to evaluate the analgesic effect of a pre-TKA downregulation of intra-articular inflammation in patients with high-pain knee-osteoarthritis and signs of central sensitization. Aside from pain during standardized testing and patient reported diaries, our multifactorial assessment included evaluation of nociceptive function by QST and inflammation with CRP and intra-articular IL-6. Our study is one of few to test interventions in specific sensitized high-risk pain patients with knee osteoarthritis.5,28

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The intervention with 40 mg intra-articular methylprednisolone acetate 7 days prior to surgery did not reduce acute postoperative pain, either in the primary outcome measure (number of patients with moderate-severe pain during walk-test 24 hours after surgery) or in secondary outcome measures (pain during walk-test 48 hours after surgery and diary-reported pain during walk, on average, at worse or at rest as well as opioid-consumption from day 1 to day 14). The lack of an analgesic effect of the intervention is probably not explained by the dose of methylprednisolone being too low causing an insufficient reduction of inflammation, since we demonstrated a significant decrease in intra-articular IL-6 one week after injection. However, despite using the recommended dose known to be effective in conservative treatment of knee osteoarthritis9 we found no difference in occurrence of moderate/severe pain 6 days after injection and 1 day prior to surgery when tested with the standardized 5 meters walk test. This questions the analgesic effect of the intervention in a conservative setting. However, a type two error cannot be ruled out, since the limited walking distance in the test, which serves to differentiate patients in the postoperative period, probably is not physically strenuous enough in the preoperative period, reflected by low pain scores during the test (mean NRS MP group = 2, mean NRS placebo group 2.13).14 Similarly, the anti-inflammatory effect of MP was not reflected in the QST results, where no difference between groups was observed. Thus, the hypothesized association between intra-articular inflammation (resulting in preoperative nociceptive sensitization) and acute postTKA pain6,7,10,53 could not be confirmed by the demonstrated local anti-inflammatory effect of MP, and the causality is debatable,55 or a longer pre-operative treatment period is required to reduced sensitization as suggested by other studies.49 The discrepancy between our results, the above mentioned hypotheses and previous findings of an analgesic effect of intra-articular MP in arthroscopic knee surgery38,39 might be explained by the substantial surgical trauma and acute stress response in TKA18,30 exceeding any benefits from downregulation of intraarticular inflammation. Moreover, the MP was administered perioperatively in the arthroscopic

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procedures, aiming to reduce postoperative inflammation and not preexisting nociceptive changes. Whether a different approach in downregulation of preexisting inflammation (e.g. in an earlier phase of osteoarthritis, with a greater time-delay to TKA or repeated dosages) would be effective, or if patients with high pain osteoarthritis and signs of central sensitization would benefit from perioperative intervention against the acute surgical stress response with intravenous high-dose MP30 remains unsolved. However, previous data in TKA patients have reported signs of central sensitization as predictive of acute post-TKA pain,26,29,37 and although our study did not find an effect from pre-operative reduction of inflammation, an RCT with the selective COX-2 inhibitor etoricoxib reduced pain and central sensitization in patients with knee OA,5 suggesting than a longer duration of treatment or a centrally acting pain modulation may be needed.11,12 Whether symptomatic treatment of sensitization with centrally acting drugs or peripherally acting drugs with anti-inflammatory effects or peripheral blockade of ascending nociception are effective, remains to be established.46,54 Nevertheless, since approximately 70% of patients reporting moderatesevere pain during ambulation 24 hours after surgery and a median pain score during walk > 3 throughout the study period, the clinical need for improvement remains evident, calling for further studies on intensified analgesic treatments aimed at underlying pathophysiological mechanisms. The selected subgroup of osteoarthritic patients included in this study had signs of central sensitization when screened for inclusion (pressure pain threshold < 250kPa). None of the groups had normalization of their nociception when measured after intervention or after surgery, but the MP group had a trend toward worse local- (pressure pain threshold on surgical leg) and central sensitization (wind up from temporal summation) after injection of study medicine. With a median change in pain from temporal summation (wind-up pain) of 2 NRS points, the clinical relevance of the finding can be questioned, but might be caused by an irritative effect from the local injection of methylprednisolone acetate.15 Summarizing QST results, our study did not find an effect on local or central sensitization from reduced intra-articular inflammation, either due to other mechanisms for sensitization, too short treatment duration, or the need for central acting agents.

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The thorough multifactorial assessment in our study combining clinical outcomes on pain with pathophysiological understanding of inflammation and nociception strengthens our negative findings and adds to the knowledge on the potential association between inflammation, hyperalgesia and pain. The aim of our study was to examine patients with high pain osteoarthritis and central sensitization, deliberately reducing the inclusion-rate. However, the number of patients excluded for other reasons might limit the external validity, but to minimize the risk of adverse events in this first explorative study on the analgesic effect of preoperative intra-articular MP prior to TKA, precaution was prioritized. The number of patients refusing to participate was high (the majority due to reluctance to get the intra-articular injection) potentially causing selection bias, although no systematic differences between included and excluded patients were observed. As an independent risk factor for increased acute post-TKA pain,2 the inclusion of patients with a preoperative daily use of opioids is a potential confounder, but to address the clinical problem of pain management in these patients, they were included. Our aim of a 50% reduction in pain can be criticized for being over-optimistic, and that a less ambitious effect and thus a larger cohort could have been chosen, but given the potential severe adverse effects and the unpleasant nature of the intra-articular injection; a large pain reduction was needed to justify the intervention. However, since no trend towards a difference in pain between groups was found, we do not believe the study to be underpowered and consider the risk of a type II error negligible. The safety of intra-articular MP prior to primary TKA remains a topic of debate. Thus a meta-analysis of data from 1474 total primary hip- or knee patients found no increased risk of infection in patients preoperatively injected with MP (risk difference 0.02, 95% CI -0.02 to 0.07),48 nor did a systematic review on primary THA patients,34 although there may be an increased risk from post-THA injections.40 In accordance, none of the patients in this study had deep infections, and the one patient treated due to suspicion of superficial infection was in the placebo group. However, our study is not powered for adverse events and may not have been identified, but could be irrelevant in the current setting since the lack of effect from the methylprednisolone injection does not warrant this technique for clinical use to reduce postoperative pain. The expected drop-out of 10% was exceeded in the study and

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challenges our power-calculation, but since no trend towards a between group difference was seen and since the occurrence of moderate-severe pain in our primary outcome measure was high, the risk of a type II error was considered negligible. In conclusion: Our study does not support the use of methylprednisolone acetate administered 1 week preoperatively to reduce moderate-severe post-TKA pain in patients with high pain osteoarthritis and signs of central sensitization. The need for an improved analgesic strategy in this subgroup of patients is emphasized, and alternative mechanism based interventions should be explored.

Acknowledgements: The authors wish to thank Malene Rohr Andersen, MSc, PhD, and Pal Szecsi, MD, DMSci, Department of Clinical Biochemistry, Gentofte-Herlev Hospital, Denmark, for their valued effort enabling the analyzes of IL6 concentrations in synovial fluid; Alice Lundgaard Rosendahl, MSc, The Danish capital regions hospitalpharmacy, Denmark, for generating allocation sequence and preparing study medicine and Heidi Raahauge Wede, BSc in nursing, Department of Orthopedic Surgery Gentofte-Herlev Hospital, Denmark, for her help administering the study medicine.

Author contribution: Study conceptualization: H. Kehlet. Study design: I.E. Luna, H. Kehlet, C.M. Jensen, E.K. Aasvang. Study-medicine administration and data collection: I.E. Luna. Total knee arthroplasty: C.M. Jensen, T.G. Christiansen, T. Lind, S.L. Stephensen. Statistical analyzes: I.E. Luna.

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First draft of manuscript: I.E. Luna. Supervision of data-collection, statistical analyses and manuscript writing: H. Kehlet, E.K. Aasvang. All authors revised the manuscript critically and approved the final version. I.E. Luna ([email protected]) takes responsibility for the work as a whole, from inception to finished article.

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Figure 1: Administration of study medicine and data collection during the study Legend: TKA = total knee arthroplasty, IL-6 = interleukin 6, CRP = C-reactive protein.

Figure 2: Flow diagram of patients assessed for eligibility and patients included in the study. Legend: NRS = numeric rang scale 0 – 10 (0=no pain, 10=worse pain imaginable), PPT = pressure pain threshold, MP = methylprednisolone acetate, GA = general anesthesia.

Figure 3: Patient reported pain from day 1 to day 14 after total knee arthroplasty Legend: NRS = numeric rang scale 0 – 10 (0=no pain, 10=worse pain imaginable).

Figure 4: Opioid consumption from day 1 to day 14 after total knee arthroplasty Legend: Mean daily opioid dose (converted to oral morphine equivalents in mg) with 95% confidence intervals in patients treated with intra-articular methylprednisolone acetat (MP) or placebo.

Figure 5: Change in intra-articular level of IL-6 from prior to 7 days after administration of study Legend: Change in post- vs. preoperative intra-articular IL-6 levels (pg/mL) converted to a logarithmic scale between total knee arthroplasty patients treated by intra-articular injection with 40 mg methylprednisolone acetat (MP) vs. placebo.

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Table 1: Baseline- and preoperative patient characteristics for patients in per protocol analyzes. Variable

MP

group

Placebo group

Sex 6/15 11/8 (male/female) Age 68 67 (years) (range) (51 - 80) (50-80) BMI 28.8 (5.6) 28.2 (6.0) (kg/m2) ASA 9/13/2 15/6/3 (I/II/III) OP-side 13/8 10/9 (right/left) Knee pain during walk > 10 minutes 6 (5, 7) 7 (5, 8) (NRS 0-10) Pain during 5 meters paced walk test 2 (1, 3) 2 (1, 4) (NRS 0-10) Daily use of strong opioids 18/3 15/4 (no/yes) Daily use of NSAIDs 13/8 11/8 (no/yes) Daily use of Acetaminophen 8/13 10/9 (no/yes) Pressure pain treshold arm 124 (84, 161) 125 (79, 244) (kPa) Pressure pain treshold surgery-knee 143 (113, 195) 160 (89, 236) (kPa) Temporal summation: windup 1 (0, 2) 1 (0, 2) (NRS 0-10) PCS 11 (8, 22) 15 (8, 25) (score: 0-52) HADS anxiety 16/4/0 15/3/1 (no (0-7) /possible (8-10) /severe (11-21)) HADS depression: 20/0/0 18/1/0 (no (0-7) /possible (8-10) /severe (11-21)) Legend: Data are expressed as count, mean (standard deviation) or median (inter-quartile range). MP = methylprednisolone-acetate. BMI = body mass index. NRS = numeric rang scale 0 – 10 (0=no pain, 10=worse pain imaginable). ASA = American society of anesthesiologists physical status. NSAIDs = Non steroid anti-inflammatory drugs. kPa = kilopascal. PCS = pain catastrophizing scale. HADS = hospital anxiety and depression scale.

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Table 2: Pain and opioid consumption after total knee arthroplasty Moderate-severe pain at 5 meters walk test Placebo group χ2 Risk-difference Odds ratio (NRS > 3) (p-value) (95%CI) (95%CI) 24 hrs. after TKA 74% 0.2 (p=0.63) -7% (-35% to 21%) 0.7 (0.2 to 2.8) 48 hrs. after TKA 68% 0.5 (p=0.46) -11% (-41% to 18%) 0.6 (0.2 to 2.3) Pain day 1 to day 14 after TKA MP group Placebo group Mean diff. P-value Mean (95% CI) Mean (95% CI) (95% CI) AUC: pain during walk 50 (40 to 59) 54 (43 to 66) -4.9 (-19.5 to 9.7) 0.50 AUC: average pain 52 (44 to 60) 52 (41 to 63) -0.3 (-13.6 to 13.1) 0.97 AUC: worse pain 75 (64 to 85) 73 (60 to 86) 1.1 (-15.1 to 17.3) 0.89 AUC pain at rest 38 (28 to 47) 43 (32 to 54) -5.4 (-19.2 to 8.5) 0.44 Opioid-use day 1 to day 14 after TKA MP group Placebo group Mean diff. P-value Mean (95% CI) Mean (95% CI) (95% CI) AUC: use of opioids 893 (687 to 1099) 1111 (842 to 1382) -219 (-545 to 106) 0.18 Between group differences are tested with the chi square test (dichotomized data) and the unpaired t-test MP group (NRS > 3) 67% 57%

(continues data). AUC = area under the curve. Risk-difference = the risk of having moderate severe pain being in intervention group (methylprednisolone) compared to placebo group. Mean diff = Difference in mean between groups. MP = methylprednisolone-acetate, NRS = numeric rang scale 0 – 10 (0=no pain, 10=worse pain imaginable), χ2 = chi square. Opioid consumption is reported as equipotent amount of per oral morphine.

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Table 3: Quantitative sensory testing (QST) with pressure pain threshold (PPT) and wind-up from temporal summation.

MP group Placebo group

Day -7

Day -1

124 (84, 161) 125 (79, 244)

111 (75, 173) 119 (86, 161)

-1 (-70 to 19) -2 (-62 to 10)

Day -7

Day +2

Δ (-7,+2)

124 (84, 161) 125 (79, 244)

94 (89, 139) 150 (53, 224)

2 (-45 to 20) -13 (-31 to 32) 0.83 (0.41)

0.04 (0.97)

Z (p-value)

MP group Placebo group

PPT arm (kPa) Δ (-7,-1)

Day -7

Day -1

143 (113,195) 160 (89,236)

125 (81,172) 162 (123,204)

Z (p-value)

PPT leg (kPa) Δ (-7,-1) -18 (-44 to -5) -1 (-15 to 35) 1.81 (0.07)

Day -7

Day +2

Δ (-7,+2)

143 (113,195) 160 (89,236)

114 (60,184) 133 (71,199)

-25 (-69 to 3) -25 (-79 to 24) 0.24 (0.81)

Wind up (NRS) Δ (-7,-1)

Day -7 Day -1 Day -7 Day +2 Δ (-7,+2) 1 (0,2) 2 (1,4) 2 (0 to 3) 1 (0,2) 1 (1,2) 0 (-1 to 2) MP group 1 (0,2) 1 (0,3) 0 (-1 to 1) 1 (0,2) 1(0,3) 0 (-1 to 1) Placebo group -2.19 (0.03) -0.55 (0.58) Z (p-value) Legend: Patients were tested with QST 7 days prior, 1 day prior and 2 days after primary total knee arthroplasty. Changes in QST were calculated as change in PPT or windup from day -7 until day -1 or day +2 respectively (∆QST(-7,-1)=day-1 minus day-7 or ∆QST(-7,+2)=day+2 minus day-7). Results are reported as medians with interquartile range (25th percentile and 75th percentile). Between groups differences in the delta-values are tested with the Wilcoxon-Mann-Whitney test. kPa = kilopascal, MP = methylpredinisolone, NRS = numeric rang scale.

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