Variability in Alignment and Bone Resections in Robotically Balanced Total Knee Arthroplasties

Area of Science:

• Orthopedic Surgery
• Robotics in Medicine
• Biomechanical Engineering

Background:

• Image-based robotic-assisted total knee arthroplasty (RA-TKA) enables 3D surgical planning using bone anatomy.
• Intraoperative adjustments in RA-TKA are guided by dynamic assessment of ligament laxity and gap balance.
• Understanding typical implant alignment and bone resection ranges is crucial for RA-TKA.

Purpose of the Study:

• To identify the ranges of implant alignment and bone resections utilized in robotic-assisted total knee arthroplasty (RA-TKA).
• To analyze how preoperative coronal alignment influences intraoperative planning metrics in RA-TKA.
• To provide data that may inform surgical decision-making in RA-TKA.

Main Methods:

• Retrospective review of 484 primary RA-TKA cases.
• Cases were stratified based on preoperative coronal alignment (valgus, neutral, varus).
• Demographic and intraoperative data were collected and analyzed using Chi-square and ANOVA tests.

Main Results:

• Planned limb, femoral, and tibial alignment showed a trend towards increased varus from valgus to neutral to varus knees (p < 0.001).
• External transverse rotation relative to the transepicondylar axis (TEA) and posterior condylar axis (PCA) differed significantly across cohorts (p < 0.001).
• Bone resections, particularly of the distal femur and posterior femur, were greater in the varus group; tibia resections also varied significantly by cohort.

Conclusions:

• Robotic-assisted total knee arthroplasty demonstrates distinct trends in planned alignment and bone resection metrics correlated with preoperative coronal knee alignment.
• Varus knees exhibited higher variability in planned metrics compared to valgus and neutral knees.
• These findings enhance the understanding of RA-TKA and can guide surgeons in preoperative planning and intraoperative execution.