Does patellofemoral geometry in TKA affect patellar position in mid-flexion?

Area of Science:

• Orthopedic surgery
• Biomechanical engineering
• Medical device design

Background:

• Total knee arthroplasty (TKA) aims to restore knee function.
• Patellar tracking is crucial for successful TKA outcomes.
• Different TKA designs may influence patellar behavior.

Purpose of the Study:

• To compare patellar positioning at 90° flexion between two TKA models with identical tibiofemoral geometry but different patellofemoral designs.
• To test the hypothesis that a deeper trochlear design leads to more natural patellar positions.

Main Methods:

• Intra-operative navigation data from 22 TKA cases (9 HLS Noetos, 13 HLS KneeTec) were analyzed.
• Both implants were cemented, postero-stabilized TKAs with mobile tibial inserts and patellar resurfacing.
• Relative femoral, tibial, and patellar positions were recorded pre- and post-operatively.

Main Results:

• No significant differences in femoral rotation or translation were observed between the two TKA designs.
• Significant differences in patellar position were found at 90° flexion post-operatively.
• Patellar flexion was significantly different (Noetos 6.3°, KneeTec 23.5°, p = 0.031), with KneeTec showing greater flexion.

Conclusions:

• Tibiofemoral kinematics remain unchanged by different patellofemoral designs.
• Patellofemoral design significantly impacts patellar position at 90° flexion.
• The KneeTec design offers a mechanical advantage to the quadriceps compared to the Noetos design, potentially aiding patients with quadriceps weakness or patellar instability.