Joost Peerbooms

86 Chapter 6 METHODS This double-blind randomized trial included 100 consecutive patients with lateral epicondylitis for injection therapy in 2 Dutch training hospitals (St Elisabeth Hospital and Haga Hospital) between May 2006 and January 2008. The PRP preparation was done using the Recover system (Biomet Biologics, Warsaw, Indiana). This device uses a desktop-size centrifuge with disposable cylinders to isolate the platelet and leukocyte- rich fraction from a small volume of the patient’s anticoagulated blood drawn at the time of the procedure. Both PRP and corticosteroids were injected into the common extensor tendon using a 22-gauge needle and a peppering technique. Further information on the study design, power analysis, enrolment criteria, and treatment methods can be found in the 1-year follow-up report. 20 The Medical Ethical Committee and the National and Institutional Review Board approved the study. This trial is registered with identifier number 2007-004947-31 at http:// www.clinicaltrials.gov. Instruments Patients completed 2 self-report instruments at every time point: The Disabilities of the Arm, Shoulder and Hand (DASH) outcome measure and a visual analogue scale (VAS) for pain. The DASH is a 30-item, self-report questionnaire designed to assess physical function and symptoms in persons with any of several musculoskeletal disorders of the upper limbs. 3,32 The items assess the degree of difficulty in performing various physical activities because of an arm, shoulder, or hand problem (21 items), the severity of each of the symptoms of pain, activity-related pain, tingling, weakness, and stiffness (5 items), and the problem’s effect on social activities, work, and sleep, and its psychological effect (4 items). The DASH also contains 2 optional 4-item scales concerning the ability to perform sports and/or to play a musical instrument (sport/music scale), and the ability to work (work scale). In this study, the 2 optional scales were not used in the analyses. A 5-point Likert scale ranging from 1 (no difficulty or no symptom) to 5 (unable to perform activity or very severe symptom) is used. The scores for all items are then used to calculate a total scale score ranging from 0 (no disability) to 100 (severest disability). The psychometric properties of the DASH outcome measure are adequate to good. 3,32 A VAS is a measurement instrument to quantify the amount of pain reported by the patient. Scores can range from 0 (no pain) to 100 (severest pain). Data concerning type of treatment (corticosteroids or PRP), type of reintervention, complications, side, sex, and age were retrieved from medical files.