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

• There was no overall difference in medial and lateral posterior tibial slopes.
• The difference in medial and lateral posterior slopes exceeded three degrees in 41% of knees.
• Medial coronal slope was greater than lateral coronal slope in all groups.
• Females had less distance from the ACL footprint to the anterior tibial cortex.
• A monoblock bicruciate-retaining tibia may not reproduce anatomy in all patients.

BackgroundRestoration 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.MethodsWe 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.ResultsThere 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)).ConclusionsDue to highly variable proximal tibial topography, a monoblock bicruciate-retaining tibial baseplate may not reproduce normal anatomy in all patients.Level of EvidenceLevel IV - Anatomic research study.