Ceramic Modular Dual Mobility in Primary Total Hip Arthroplasty (THA)

Cobalt ion levels in blood serum in measured in [µg/L], Comparison between the two groups

Chromium ion levels in blood serum in measured in [µg/L], Comparison between the two groups

The Harris Hip Score (HHS) is one of the most used scores in total hip arthroplasty, mainly combining range of motion questions with questions regarding daily life activities. The HHS is a measure of dysfunction so the higher the score, the better the outcome for the individual. Results can be recorded and calculated online. The maximum score possible is 100, any result <70 is considered a poor result; The HHS is an outcome measure administered by a qualified health care professional, such as a physician or a physical therapist.

The gait lab analysis involves a high amount of recorded data and variables. Gait lab analyses are performed with the patients between the preoperative state, 3 months after surgery and 1 year postoperative. The Gait Profile Score (GPS) is used as a measure for the deviation in gait kinematics from a healthy patient population to compare the two treatment groups.

Lower score values can be considered as a sign of better restoration of the physiological gait kinematics.

Patient is asked for satisfaction with surgery result with a 4-point scale: very satisfied, satisfied, unsatisfied, very unsatisfied

Inclination is the orientation of the cup in the coronal plane. The target acetabular cup inclination is a "safe zone" between 30-50° abduction (assessed on antero-posterior (ap) x-rays of the hip). The comparison of the intraoperatively achieved inclination and the inclination at different follow-up examinations allows prediction on longterm success.

Centre of Rotation (CoR) is defined as the zero position for the measurement of potential cup migration. Horizontal: Distance of CoR to ipsilateral teardrop; Vertical: Distance CoR to Inter-teardrop line; The comparison of the intraoperatively center of rotation and the center of rotation at different follow-up examinations allows prediction on longterm success.

Bony Osseointegration or conspicuous features of the cup are assessed on anterior-posterior and lateral x-rays of the cup and will be analysed according to the zones defined by Charnley. "Charnley" zones of the acetabular component are distinct zones used in assessment of aseptic loosening in total hip joint replacements. The radiolucencies are categorized to "none", "less than or equal to 2mm" and "more than 2 mm"

Brooker classification divides heterotopic ossifications that form following total hip replacement to four classes. Class I: islands of bone within soft tissues around hip; Class II: bone spurs in pelvis or proximal end of femur leaving ≥1 cm between the opposing bone surfaces; Class III: bone spurs that extend from pelvis or the proximal end of femur, which reduce the space between the opposing bone surfaces to <1cm; Class IV: ankylosis of the hip on x-ray