Valutazione in vitro dell’impatto dell’artroplastica totale di ginocchio sulla biomeccanica femoro-rotulea: confronto tra cinematica nativa e protesica, con e senza resurfacing rotuleo

Total knee arthroplasty (TKA) is a widely performed procedure for restoring joint function in patients with advanced cartilage degeneration. Despite its effectiveness, up to 20% of patients report dissatisfaction after surgery due to residual pain, instability or a foreign body sensation. One debated issue is whether a tricompartmental or bicompartmental prosthesis should be preferred. This in vitro study compared native patellofemoral kinematics with those observed after bicompartmental prosthesis implantation (B_TKA) and after patellar resurfacing (T_TKA). The influence of two femoral designs was also analyzed: a traditional one aimed at maximizing patellar stability, and a “patella-friendly” one conceived to accommodate greater variability in quadriceps activation. Twelve cadaveric knees from six donors were tested during passive flexion-extension under controlled patellar tendon loads. Kinematics were recorded with an optoelectronic system and analyzed with the Kruskal–Wallis test followed by post hoc analysis. Patellar motion was evaluated at five flexion angles (start, 30°, 60°, 90°, end). Results showed significant differences at 60° of flexion for patellar spin (rotation around the antero-posterior axis) (p = 0.005) and medio-lateral translation (shift) (p = 0.048) in T_TKA compared with native and B_TKA. The two femoral designs differed significantly in spin, tilt (rotation around the proximal–distal axis) and shift: spin within 0–30° (p < 0.005), tilt (p < 0.05) and shift (p < 0.001) from 60° to full flexion. The patella-friendly design reproduced native kinematics more closely at low flexion, whereas the traditional design approximated physiological behavior beyond 60°. These findings indicate that T_TKA modifies patellar motion, while the traditional design better reproduces native tilt and shift. The decision to perform patellar resurfacing should therefore be individualized, taking into account patient-specific characteristics and osteoarthritis.