Assessing pain in patients undergoing joint replacement Dr Vikki Wylde Research Associate Musculoskeletal Research Unit, University of Bristol

Outline Chronic pain definition Chronic post-surgical pain Pain assessment methods Clinician-administered tools Patient-reported outcome measures Quantitative Sensory Testing Recent innovations in pain assessment methods

What is chronic pain? International Association for the Study of Pain Definition: “an unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage” Chronic pain: present for 3-6 months

Chronic pain and total knee replacement (TKR) Osteoarthritis is leading cause of chronic pain in Europe - Cited by 34% of people as cause of self-reported chronic pain1 Primary aim of joint replacement is to relieve chronic pain2 Some patients continue to experience chronic pain after joint replacement 1Breivik et al. Eur J Pain 2006;10:287-333 2Scott et al. J Bone Joint Surg Br 2012;94:974-81

Chronic pain and TKR Systematic review found that 20% of patients experience moderate-extreme pain in their replaced knee1 Over 60,000 TKRs performed in NHS each year = 12,000 new cases of chronic pain after TKR every year Likely to increase with rise in projected need for TKR2 Chronic post-surgical pain not unique to TKR3 1 Beswick et al. BMC Open, 2012 2 Kurtz et al. J Bone Joint Surg Am, 2007 89:780-5 3Macrae et al. Br J Anaesth, 2008 101:77-86

Chronic pain and TKR Interview study with 28 patients experiencing chronic pain after TKR1 “. . .It’s disappointing because you think it’s gonna be so much better after you’ve had it done, and really you’re not” “Depressed, totally depressed, sad, miserable, charred off, all the things that go with that that you can think of” “. . . I just don’t know what to do with it.. . . I was in so much pain I said to my husband, and it’s only him I’d tell, I wouldn’t tell the family, I said if I don’t do something I shall, well I shall jump off the bridge” 1Jeffery et al 2011, Arthritis Care and Research. 63, 2, 286–292

Assessment of pain Clinician-administered tools Patient-report outcome measures Quantitative Sensory Testing Recent innovations

Clinician-administered tools Completed by healthcare professional Often composite measures e.g. American Knee Society Score includes assessment of range of motion, stability, alignment, pain, function Discrepancies between clinician and patient ratings of health1 Clinicians often underestimate their patients’ pain severity2 – most marked with moderate-severe pain 1Hewlett S. J Rheumatology, 2003; 30, 877-79 2Mantyselka et al. British Journal of General Practice, 2001; 51, 995-97

Patient-reported outcome measures Generic questionnaires Measure general health SF-36 – general bodily pain Disease-specific questionnaires Measure pain characteristic of a particular condition ICOAP – aching and sharp pain of osteoarthritis Joint-specific questionnaires Measure pain in a particular joint Oxford knee score – knee pain

Patient-reported outcome measures Pain domains assessed by questionnaires Pain severity e.g. WOMAC pain scale Pain qualities e.g. McGill Pain Questionnaire Neuropathic pain e.g. PainDETECT Pain-related disability e.g. Chronic Pain Grade

Patient-reported outcome measures Many different pain assessment tools available 54 different tools used over 10 year period1 Advantages Capture patients perception of pain Efficient Cost-effective Disadvantages People can experience difficulties in expressing their pain on a standardised questionnaire format 1 Wylde et al. Arthritis Care and Research, under review

Patient-reported outcome measures Think aloud study1: 20 patients with painful TKR completed the Chronic Pain Grade Difficulties indentified: Fluctuating nature of pain Accounting for co-morbidities and pain elsewhere Adjustment to pain Could distort estimates of pain severity and impact 1Wylde et al. Osteoarthritis and Cartilage 2012; 20, 102-5

Quantitative Sensory Testing (QST) Can be used to investigate pain mechanisms Assesses participants’ responses to external stimuli to identify abnormalities in pain processing Pain thresholds commonly measured Has been used to demonstrate patients with knee OA have central pain sensitisation, which is associated with chronic pain after TKR1 1Wylde et al. Rheumatology. 2012 ;51(3):535-43

Recent innovations: colour and pain Group interviews with 17 patients with painful knee OA Associations between colour and pain: High intensity pain = red Absence of pain = colours associated with emotion Aching pain = dull colours Sharp pain = bright colours Majority of patients could envisage using colour to talk about their pain with healthcare professionals 1Wylde et al. Musculoskeletal Care, in press

Conclusions Chronic pain after TKR is prevalent Many patients experience psychological distress from this pain Many different pain assessment methods available - none are perfect Awareness of these different methods could improve pain assessment in a clinical setting

Thank you for your attention Musculoskeletal Research Unit School of Clinical Sciences, University of Bristol, Avon Orthopaedic Centre E-mail: V.Wylde@bristol.ac.uk