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Aligning Success: Insights From 85,000 CT Scans on Trochlear Groove Positioning With Kinematic Alignment
Reece I Vesperman1, Jacob A Fox, Courtney E Baker
1From the Department of Orthopaedic Surgery (Dr. Vesperman, Dr. Fox, Dr. Baker, Dr. Martin), Vanderbilt University Medical Center, Nashville, TN, the Vanderbilt University School of Medicine (Wong), Nashville, TN, the Restor3D (Atkins), Durham, North Carolina, and the Department of Orthopedic Surgery (Dr. Faschingbauer), Clinic Penzing, Vienna Healthcare Group, Wein, Austria.
Many total knee arthroplasty patients experience patellar maltracking due to implant positioning. This study found significant trochlear groove malalignment with kinematic alignment, necessitating better implant designs.
Area of Science:
- Orthopedic surgery
- Biomechanical engineering
- Medical imaging analysis
Background:
- Patellar maltracking is a common issue after total knee arthroplasty (TKA), leading to pain and dissatisfaction.
- Femoral component internal rotation and trochlear groove (TG) malpositioning are frequent causes of patellar maltracking.
- Current alignment classifications like CPAK lack 3D anatomical consideration, and kinematic alignment (KA) may increase maltracking risk with standard implants.
Purpose of the Study:
- To evaluate trochlear groove (TG) orientation in axial and coronal planes.
- To assess TG orientation after virtual kinematic alignment (KA) placement of a standard femoral component.
- To analyze TG orientation relative to the quadriceps line of force (QLF) and ideal tracking parameters in a large TKA cohort.
Main Methods:
- Analysis of 85,604 CT scans from patients undergoing primary TKA.
- Calculation of standard alignment parameters (LDFA, MPTA, HKA) and CPAK classification.
- Virtual implantation of a femoral component using KA principles (6° lateral TG) and measurement of TG orientation relative to the QLF.
Main Results:
- Significant proportion of patients (41%) exhibited a TG medial to the QLF, indicating potential maltracking.
- Certain CPAK types (2, 3, 6) showed higher incidences of internal rotation and medial TG orientation.
- Achieving KA in ~30% of patients required >3° internal rotation and valgus tilt, with ~2% needing >5°.
Conclusions:
- A substantial number of patients display TG malpositioning and excessive internal rotation when using mechanical alignment-designed implants with KA.
- Current alignment methods may not adequately address 3D anatomy, increasing the risk of patellar maltracking.
- Development of 3D classification systems and alignment-specific implant designs or guardrails is crucial to prevent malpositioning.
