Mylène Jansen

112 Chapter 6 which all patients in the present study provided. Official ethical approval was ruled as not required by the medical ethical review committee of the University Medical Center Utrecht (protocol number 17-005C) and all patients give written informed consent. In the open prospective study (OPS) and the 2 randomized controlled trials (RCTs), inclusion criteria were: medial tibiofemoral compartmental OA; intact knee ligaments; normal range-of- motion (min. of 120° flexion); normal stability; BMI <35; visual analogue scale of pain ≥60 mm, radiographic signs of joint damage and tibiofemoral OA (radiological joint damage KLG >2 as judged by the orthopedic surgeon). Exclusion criteria were (among others): presence or history of inflammatory or septic arthritis; severe knee malalignment (>10º) requiring surgical correction; psychological inabilities or difficult to instruct; joint prosthesis elsewhere in the body; not able to undergo MRI examination; post traumatic fibrosis due to fracture of the tibial plateau; surgical treatment of the involved knee <6 months ago; contra-lateral knee OA that needs treatment; primary patellofemoral OA. For the OPS the age was <60 years, for the RCTs <65 years. For the OPS and RCT versus TKA, all patients had to be considered for TKA. For the RCT versus HTO, all patients had to be considered for HTO, with medial compartmental knee OA with a varus deviation of <10°. All inclusion aspects have been described in detail for all 3 studies, previously. 8,13,14,16 All trials were granted ethical approval by the medical ethical review committee of the University Medical Center Utrecht (protocol numbers 04/086, 10/359/E, and 11/072) and registered in the Netherlands Trial Register (trial numbers NL419, NL2761 and NL2680). All patients gave written informed consent. Knee joint distraction treatment KJD was performed by fixating an external distraction device to the femur and tibia using 8 half pins according to a standardized surgical procedure. In all patients, a device was used consisting of 2 distraction tubes with internal springs, 1 placed medially and 1 laterally of the knee joint (Figure 1). The half pins (self-drilling, 5 mm diameter) used to fixate the distraction tubes were placed in pairs at 4 different locations (tibia/femur and medial/lateral), all placed outside the knee joint area to prevent complications during a potential future prosthesis surgery. 17 The medial femoral pins were positioned parallel to the knee joint line in an approximately 10° dorsomedial-ventrolateral direction (10° angulation to the frontal plane) to minimize interference of the half pins with the quadriceps muscles. The lateral femoral pins were placed parallel to the knee joint line, perpendicular to the tibial bone axis, and approximately in the frontal plane. The medial tibial half pins were positioned parallel to the knee joint space, and if possible perpendicular to tibial bone axis and the anteromedial tibial face, approximately at 35° to the frontal plane. The lateral tibial half pins used the same slope of approximately 35° to the frontal plane. Proper positioning and depth, with slight protrusion of the half pin (of the pointed tip only) through the second cortex, was checked using fluoroscopy (C-arm). After positioning the half pins and distraction tubes, according to standardized surgical procedures,