Mylène Jansen

User-friendliness of a dedicated KJD device 133 7 Table 2 : Inclusion and exclusion criteria for knee joint distraction treatment in this study Inclusion criteria Exclusion criteria Age <65 years Varus/valgus malalignment >10 degrees BMI <35 kg/m 2 History of inflammatory or septic arthritis VAS pain >40 mm Primary patellofemoral OA Kellgren & Lawrence grade ≥2 Surgical intervention within past 6 months prior to KJD Persistent medication and conservative treatment resistant tibiofemoral pain Osteopenia hampering proper pin fixation Physiological inabilities to cope with the treatment Arthroplasty of other joints, or expected need within 6 months Flexion contracture Vascular and/or soft-tissue abnormalities Body mass >130 kg BMI: body mass index; KJD: knee joint distraction; OA: osteoarthritis; VAS: Visual Analogue Scale. The 2 device types generally require the same anatomical sites and method of fixation as described previously, except for device specific differences. 1 In short, the external fixation device was surgically fixated to the femur and tibia using 8 self-drilling, 5 mm half pins. The CD device consisted of two rigid distraction tubes (Monotubes, see above), while the DD device (KneeReviver) was non-rigid to allow more user-friendly positioning around the joint (Figure 1). Both devices contain internal springs. After positioning of the pins and frame, 2 mm distraction distance was provided intra-operatively and extended with 1 mm per day to reach 5 mm distraction, confirmed radiographically. Afterwards, patients were discharged from the hospital and allowed full weight-bearing, supported with crutches if needed, and after 6 weeks of distraction the frame and pins were removed. All patients were treated within the University Medical Center Utrecht, Utrecht, The Netherlands (UMC Utrecht), where ethical approval was obtained from the ethical committee for a prospective study design (protocol number 17-293). No randomization of patients between the 2 devices was allowed, since the DD device for KJD was available for standard care at the start of the study. It was anticipated in advance that the DD device was of added value, therefore, the ethical committee considered that randomization to an inferior device (viz. the CD device) would be non-ethical. As such, patients that had been treated with the CD device previously with written permission for future use of their data in retrospect, were included for analysis. The study was performed in accordance with the ethical principles from the Declaration of Helsinki and all patients gave written informed consent. Data collection As a measure for user-friendliness of the devices for the orthopedic surgeons, the duration of the intervention was collected from the surgery reports in the electronic medical records, defined as the time between the first incision and the end of the procedure as registered in clinical practice. Complications as a result of KJD treatment were assessed from medical records as well. After treatment, patients filled out a customized questionnaire, composed with a patient