Abstract
Different femoral designs in TKA have shown multiple effects on the conformity of the patella-femoral joint. Historically, this anatomical relationship may interfere with clinical results. The objective of this study was to compare the reproducibility of a correct patello-femoral conformity in patients underwent TKA utilizing modern femoral implants.
MATERIALS AND METHODS
We performed 50 consecutives TKA in fifty patients affected by knee arthritis utilizing the PFC Sigma System (De Puy, Warsaw, USA) with a new femoral design, having a prolonged anterior flange and a “smoother” throclea. The surgical procedure was performed utilizing the Sigma HP instrumentation to allow 3 degrees of external rotation of the femoral component and the “balanced gaps technique” was chosen. All patellae were replaced. All patients were evaluated preoperatively and at six months follow-up both clinically with the Knee society Score as well as radiografically: standing 30x90 cm. view, Merchant view, standard lateral view and a CT-scan with two millimeters cuts (Berger Protocol) at 20 degrees of flexion were all done. Particular attention was paid to the following CT measurements: patellar tilt, patellar conformity angle, patellar lateralization, femoral component external-rotation in relation to the patellar sitting. Statistical analysis was performed utilizing the t-test e the Wilcoxon test (p<.05).
RESULTS
Any patient was dropped from the study group. Femoral component positioning in relationship to the trans-epicondilar axis showed at follow-up an external rotation of 2.74° (± 2.10°) respect to a preoperative value of 5.7 ° (± 1.80°). Average patellar conformity angle was at follow-up 12.5 (range, -2.5 ° - 28.2 °) respect to an average preoperative value of 10.3° (range, 1.5 – 25.6). Average patellar tilt at follow-up was 2.8°(±7.5°) respect to a preoperative average value of 18.5° (±8.5 °). Average lateralization index was at follow-up 2.7 mm (range, - 3.4 – 7.1 mm) respect to a preoperative value of 12.2 mm (± 4.8 mm).
CONCLUSION
This study highlighted that a correct utilization of a modern instrumentation and a femoral design with softer edges and a prolonged femoral groove allow for a correct reproducibility of the patello-femoral conformity. TC scan is a reliable method to evaluate the patella-femoral compartment after TKA.
