Tibial component considerations in bicruciate-retaining total knee arthroplasty: A 3D MRI evaluation of proximal tibial anatomy

Background Restoration of normal anatomy and proper ligament balance are theoretical prerequisites for reproducing physiological kinematics with bicruciate-retaining total knee arthroplasty (TKA). The purpose of this study was to use a 3D MRI technique to evaluate the topography of the proximal tibia and outline considerations in tibial component design for bicruciate-retaining TKA. Methods We identified 100 consecutive patients (50 males and 50 females) between ages 20 and 40 years with knee MRIs without arthritis, dysplasia, ACL tears, or prior knee surgery. A novel 3D MRI protocol coordinating axial, coronal, and sagittal images was used to measure: 1) medial and lateral posterior tibial slopes; 2) medial and lateral coronal slopes; and 3) distance from the anterior tibia to the ACL footprint. Results There was no overall difference in medial and lateral posterior tibial slopes (5.5° (95% CI 5.0 to 6.0°) vs. 5.4° (95% CI 4.8 to 6.0°), respectively (p = 0.80)), but 41 patients had side-to-side differences greater than 3°. The medial coronal slope was greater than the lateral coronal slope (4.6° (95% CI 4.0 to 5.1°) vs. 3.3° (95% CI 2.9 to 3.7°), respectively (p < 0.0001)). Females had less clearance between the anterior tibia and ACL footprint than males (10.8 mm (95% CI 10.4 to 11.2 mm) vs. 13.0 mm (95% CI 12.5 to 13.5 mm), respectively (p < 0.0001)). Conclusions Due to highly variable proximal tibial topography, a monoblock bicruciate-retaining tibial baseplate may not reproduce normal anatomy in all patients. Level of Evidence Level IV - Anatomic research study.