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Patello-femoral Tracking Optimization in Robotic-Assisted Total Knee Arthroplasty
Hemant Reddy1, Catherine Di Gangi1, Guillermo DeGuzman1
1Department of Orthopedic Surgery, NYU Langone Health, New York, New York.
The Journal of Arthroplasty
|April 1, 2026
Summary
Robotic-assisted total knee arthroplasty (RA-TKA) shows planned femoral internal rotation (IR) does not impact long-term outcomes. However, excessive valgus and IR in RA-TKA may increase patellar complications.
Area of Science:
- Orthopedic Surgery
- Biomechanical Engineering
- Medical Robotics
Background:
- Robotic-assisted total knee arthroplasty (RA-TKA) enables personalized component alignment.
- Standard trochlear designs may lead to femoral internal rotation (IR) relative to the transepicondylar axis (TEA) during kinematic alignment.
- The impact of femoral component alignment on patellar tracking in RA-TKA requires investigation.
Purpose of the Study:
- To determine the effect of femoral component alignment on patellar tracking in robotic-assisted total knee arthroplasty.
- To evaluate patient-reported outcomes based on femoral component rotation and coronal alignment.
- To identify potential risks associated with specific femoral alignment configurations in RA-TKA.
Main Methods:
- Retrospective review of 932 RA-TKA cases using a CT-based robotic platform.
- Femoral component rotation defined relative to the transepicondylar axis (TEA) as internal (IR) or external (ER).
- Femoral coronal alignment classified as varus (Var) or valgus (Val); patient outcomes analyzed using ANOVA and Chi-square tests.
Main Results:
- The majority of cases were Varus-External Rotation (Var-ER) (48%) and Valgus-External Rotation (Val-ER) (26%).
- Femoral internal rotation (IR) was associated with Valgus alignment (Val-IR cohort).
- All three patella-related complications, including reoperations, occurred exclusively in the Val-IR cohort (P < 0.001).
- Short-term (six-week) Knee Injury and Osteoarthritis Outcome for Joint Replacement (KOOS, JR) scores were lowest in the Var-ER cohort.
Conclusions:
- Planned femoral IR in RA-TKA did not significantly affect patient-reported outcomes beyond six weeks postoperatively.
- A significant association was found between combined valgus alignment and internal rotation (Val-IR) and patellar complications.
- Surgeons should exercise caution regarding excessive combined valgus and IR with specific femoral implant designs.
