Abstract
INTRODUCTION
The purpose of our work was to evaluate changes in clinical scores, passive knee kinematics and stability after mobile bearing TKA surgery.
MATERIAL AND METHODS
60 patients were treated with a mobile bearing prosthesis (Gemini, Waldemar Link, Hamburg, Germany). PCL was always resected. Inclusion criteria were BMI >30, age range 60–80 yrs. Preoperative KSS, KOOS and SF36 scores were recorded. Surgeries were performed with a navigation system (BLU-IGS, Orthokey Italia, Firenze, Italy) to verify bone cuts, ligament balancing and implant positioning. Kinematic tests were executed to determine: tibial rotation and femoral translation through flexion range. Stability tests were performed using varus-valgus stress in extension and at 30° of flexion and drawer test. Acquisition were perfomed with menisci and cruciate ligaments intact, and repeated after final implant fixation. Clinical scores were recorded at 6 months follow-up.
RESULTS
All clinical scores showed increased value at 6 months follow up. KSS changed from 35±16.6 to 89.6±17.2; KOOS changed from 45.1 ±15.7 to 89.4 ±20.6; SF 36 changed from 42.5±21.4 to 85.1±24.6. Average preoperative kinematics showed a rotation pattern of 10° during flexion, mostly occurring at first 30° of flexion. All tibiae resulted externally rotated preoperatively. After TKA the similar rotational pattern was maintained; screw-home was slighlty reduced, but tibial external rotation was corrected. Traslation patterns showed no statistically differences. VV stability was reduced in extension but not at 30° of flexion. AP stability at 90° of flexion increased after TKA (from 8.2 mm ± 4.9 to 13.2 mm ± 5.4).
DISCUSSION
Mobile bearing PCS TKA was effective in increasing funtionality of the patients. Clinical scores improved after implant. Kinematics didn't change significantly. The correction of preoperative external rotation was noted, and similar AP translation pattern was obtained. Screw-home mechanism was reduced, and IE rotation pattern is more distributed throughout the flexion range. Stability in extension was restored, while it was not at 30° of flexion, as also drawer test resulted increased after TKA. This may be due to the absence of both cruciate ligaments.
