Normal Femorotibial Rotational Alignment and Implications for Total Knee Arthroplasty: an MRI Analysis

Abstract

Background: Rotational alignment of prosthetic components in total knee arthroplasty (TKA) is important to successful outcomes. Component malrotation is a known cause of revision and understanding normal rotational alignment may help recreate normal joint kinematics. To date, no large MRI study assessing femorotibial rotational alignment in nonarthritic knees has been undertaken. Questions/ Purposes: Is Insall's tibial axis a reliable rotational landmark against common femoral rotational axes in the nonarthritic patient population? Methods: We reviewed 544 knee MRI scans performed for suspected soft tissue pathology and identified Insall's tibial rotational axis as well as the femoral clinical trans-epicondylar axis (TEAc), femoral surgical trans-epicondylar axis (TEAs), posterior condylar articular axis (PCA), and a modified Eckhoff's cylindrical axis. The perpendiculars of these axes were superimposed on Insall's tibial axis, and the angular differences were measured. Results: Insall's axis was internally rotated to the TEAc by 1.4°, externally rotated to Eckhoff's cylindrical axis by 1.8°, externally rotated to the TEAs by 2.7°, and externally rotated to the PCA by 3.5°. The mean deviation from 0°(optimal alignment for each femoral axis) was significantly greater for the PCA relative to all other femoral axis. Conclusion: Insall's axis is a reliable landmark for rotational positioning of the tibial component and may optimize femorotibial kinematics in fixed-bearing TKA.

Evaluation of tibial rotational axis in total knee arthroplasty using magnetic resonance imaging

“…In fact, the MTT technique could lead to excessive external rotation of the tibial component 2,26 . Our results show that MTT was externally rotated by 0.5° ± 4.4°, a similar result to the one obtained by Wernecke, that showed 1.4° ± 4.9° externally rotated 12 . Some studies have suggested that the alignment of the tibial component with the center of PTM could be beneficial for patellofemoral tracking and anterior knee pain 22 .…”

“…However, there have been considerable arguments regarding which rotational reference should be the standard for tibial alignment 10 . Traditionally, the anteroposterior (AP) axis is determined on tibial component during preoperative planning using various bony landmarks as references 11,12 . There are still arguments regarding whether the AP axis has the best reliability with the least variability, and also regarding the identification of the optimal AP axis of the tibial component 13 .…”

Tibiofemoral rotation alignment in the normal knee joints among Chinese adults: a CT analysis

“…In the 1990s, Insall [16] described an anteroposterior (AP) axis from the junction of the medial and the middle-thirds of the tibial tubercle to the PCL. Wernecke et al [20] performed MRI of 544 cases of normal knee joint and believed that Insall's axis was a reliable landmark for rotational alignment of the tibial component, which may optimize femorotibial kinematics in fixed-bearing TKA. Until date, the Insall's rotational axis for the tibial component in TKA has been generally accepted.…”

Tibiofemoral rotation alignment in the normal knee joints among Chinese adults: A CT analysis

“…axis from the junction of the medial and the middle-thirds of the tibial tubercle to the PCL. Wernecke et al [20] performed MRI of 544 cases of normal knee joint and believed that Insall's axis was a reliable landmark for rotational alignment of the tibial component, which may optimize femorotibial kinematics in fixed-bearing TKA. Until date, the Insall's rotational axis for the tibial component in TKA has been generally accepted.…”