Concept and advantages of trochlear navigation for proper rotational alignment of the femur component in TKA

Background: Precise rotational alignment of the femoral component in total knee arthroplasty (TKA) is critical for flexion gap symmetry and optimal patellofemoral tracking. Conventional methods, including visual identification of the transepicondylar axis or fixed 3° external rotation, often fail to account for significant individual anatomical variability in the posterior condylar angle.

Objective: This study evaluates the reliability and reproducibility of trochlear navigation, a computer-assisted technique that aligns the prosthetic component by superimposing it onto the native trochlear anatomy.

Key Points: A prospective study of 145 patients underwent TKA using a navigation system that utilizes bone morphing to create a 3D model. The technique aligns the prosthetic trochlea with the native trochlea across 30°, 60°, and 90° of flexion. Results demonstrated high concordance between navigated rotational values and preoperative CT measurements, with an average posterior condylar angle of 5° (range 0°–11°). Postoperative analysis showed 98.7% of patients had centered patellar tracking. Furthermore, 78% of cases achieved a flexion gap differential of less than 1 mm between medial and lateral compartments. The study also noted that achieving optimal alignment required a mean component lateralization of 2.3 mm in 76% of cases.

Conclusion: Trochlear navigation provides a precise method for determining femoral component rotation and mediolateral positioning. By prioritizing the restoration of native patellofemoral anatomy, the technique ensures stable kinematics and a balanced flexion gap, effectively addressing the limitations of empirical rotational targets and inconsistent anatomical landmarks.