Measuring Tibial Component Rotation Following Total Knee Arthroplasty: What Is the Best Method?

Tibial component malrotation is associated with pain, stiffness, and altered patellofemoral kinematics in total knee arthroplasty (TKA). However, measuring tibial component rotation following TKA is difficult. Proposed protocols utilizing computed tomography (CT) lack validity and can be time-consuming. This study aimed to (1) compare the reproducibility of the Berger (two-dimensional CT) and Mayo (three-dimensional CT) protocols and (2) validate a simple measurement technique using an anatomical distance on two-dimensional axial CT-the Center of the Tibial tray to the tip of the Tibial Tubercle (CTTT).

Rotational alignment of 70 TKA patients was evaluated by 3 independent observers using the Berger, Mayo, and CTTT protocols. The inter-rater and intra-rater interclass correlation coefficients, mean difference between measurements, and the mean measurement times were calculated.

The intra-rater reliability for all 3 protocols was rated as "very good" (Mayo 0.96, Berger 0.85, and CTTT 0.85). The inter-rater reliability for the Mayo and the Berger method was rated as "very good" (0.87 and 0.83, respectively), and the CTTT was rated as "good" (0.79). Comparing the CTTT to the Mayo method produced an r² value of 0.73 with 92% of CTTT measurements ≤6 mm having <9° of tibial component internal rotation and 93% of patients with a CTTT ≥10 mm having ≥9° internal rotation.

Three-dimensional CT is the gold standard for measuring tibial component rotational alignment. The CTTT has the strongest correlation to the Mayo method and can be reliably used as a rapid screening tool.