The Effect of Patellar Positioning on Femoral Component Rotation when Performing Flexion Gap Balancing Using a Tensioning Device for Total Knee Arthroplasty

There is an increasing interest in new devices such as tensiometers for flexion gap balancing during total knee arthroplasty (TKA). The purpose of this study was to determine the influence of patella positioning during flexion gap balancing on femoral component rotation. We prospectively evaluated 32 consecutive knees in 31 patients who underwent primary TKA for degenerative osteoarthritis and where soft tissue balancing was performed using the same tensiometer. Preoperative measurements included valgus/varus deformation, mechanical axis, epicondylar axis, and tibial slope. Intraoperatively, measurement of femoral component rotation in 90 degrees of knee flexion was conducted in three different positions of the patella: (1) patella reduced, (2) patella dislocated but not everted, and (3) patella dislocated and everted. The femoral component had significantly higher rotation when the patella was reduced compared with a dislocated patella (4.9 ± 2.1 degrees vs. 4.2 ± 2.2 degrees; p = 0.006) and compared with a dislocated and everted patella (4.9 ± 2.1 degrees vs. 4.1 ± 2.3 degrees; p = 0.006). Varus knees (n = 22) demonstrated significantly increased femoral component rotation if the patella was reduced (5.3 ± 2.2 degrees) compared with dislocated patella without eversion (4.7 ± 2.3 degrees; p = 0.037) and with eversion (4.4 ± 2.5 degrees; p = 0.019). As such, the measurement of the mediolateral flexion gap stability with a laterally dislocated patella leads to a statistically significant overestimation of the lateral ligament stability and an underestimation of the external rotation positioning of the femoral component of approximately 1 degree, which is aggravated in varus knees. This is a Level II, prospective consecutive series study.

Femoral component rotation angle after unicompartmental knee arthroplasty using the anatomical tibial component cutting technique with computer-assisted surgery by CT-scan

Complication following UKA in medial compartment OA knee often related to rotatory malposition of the femoral component The purpose of this study was to study outcome following Femoral component rotation angle after unicompartmental knee arthroplasty using the anatomical tibial component cutting technique with computer-assisted surgery by CT-scan measurement in Rajavithi hospitalRetrospective descriptive study of 16 patients performed medialUKA in Rajavithi Hospital Bangkok Thailand.Single orthopedic surgeon and using computer-assisted with anatomical tibia cutting technique(tibial resection in 3-degree varus).The femoral component rotation was assessed in an axial cut CT scan. measure angle between Epicondylar axis and Posterior condylar axisThe authors analyzed 16 knees with mean age about 56 years, male 2 Female 14 and the mean BMI was 24 kg/m 2 (average body weight 63 kg)Mean of Femoral component rotation angle in this study is 2.94-degree internal rotation(internal rotation compare with Epicondylar axis). A range of femoral component internal rotation was 0-6 degree .mean varus-valgus angle was 1.81-degree varus and mean flexion-extension angle was 5.56-degree flexionFemoral component rotation angle in unicompartmental knee arthroplasty(UKA) in medial compartment osteoarthritis knee with using of the computer-assisted with anatomical tibia cutting technique have a favorable result (Mean = 2.94-degree internal rotation 1.81-degree varus and 5.56-degree flexion).