2025 ISAKOS Biennial Congress Gong Show Poster

Difference in Optimal Rotational Alignment of Femoral Component According to Superficial Medial Collateral Ligament Management in Total Knee Arthroplasty

Samuel Jaeyoon Won, MD, Dongjak-Gu, Seoul KOREA, REPUBLIC OF
Wonseok Lee, MD, Seongnam-Si KOREA, REPUBLIC OF
Heeyoon Chung, M.D., Seongnam-Si, Gyeonggi-do KOREA, REPUBLIC OF
Chong Bum Chang, MD, PhD, Seongnam-Si, Gyeonggi-do KOREA, REPUBLIC OF
Seoul National University Bundang Hospital, Seongnam-si, Gyeonggi-do, KOREA, REPUBLIC OF

FDA Status Not Applicable

Summary

We found that clinical TEA was an optimal reference for TKA without sMCL release and surgical TEA for TKA with sMCL release to get balanced flexion gap without adverse effect on patellar tracking.

Abstract

Introduction

The posterior condylar axis (PCA) and transepicondylar axis (TEA) are typical references for femoral component (FC) rotation in TKA, and a rotation of 3º to 6º of external rotation (ER) relative to the PCA is generally considered acceptable. Superficial MCL (sMCL) release is often required to correct significant varus malalignment during TKA. However, sMCL release is known to have a greater effect on the flexion medial gap, so a usual ER can lead to medial instability in flexion after TKA. The TEA has been reported in two different forms: surgical TEA (sTEA) and clinical TEA (cTEA). Even though the two TEAs differ by 3º to 4º, both the sTEA and cTEA have been reported to be optimal rotational references. Therefore, it would be reasonable to set the FC rotation within the range of sTEA and cTEA for optimal flexion balance.
This study aimed to 1) Calculate the angles between the two TEAs and PCA in patients undergoing primary TKA due to varus knee osteoarthritis (OA). 2) Compare the amount of FC rotation between patients requiring sMCL release and those who did not. 3) Compare the patellofemoral tracking condition between patient groups with different sMCL management.

Methods

This study included 256 knees (198 patients) undergoing primary TKA due to varus knee OA. Preoperatively, we assessed angles between the PCA and two TEAs (sTEA and cTEA) in the CT images of the knee. During TKA, before sMCL release, we assessed the amount of FC rotation required to achieve a balanced flexion gap within 1 mm difference. If the amount exceeded the patient’s cTEA ~ PCA angle, we released sMCL, then reassessed and applied the amount of FC rotation required to achieve a balanced flexion gap. We recorded the amount of FC rotation and assessed patellar tracking condition. We developed two study groups: sMCL preserving group (MP group) and sMCL release group (MR group) and compared the amount of FC rotation, their relationship with the two TEAs, and patellar tracking condition.

Results

The mean ER of FC relative to the PCA for balanced flexion gap was 6.1 ± 1.4º in MR group and 2.0 ± 1.5º in MP group. In the MP group, 92.4% of patients’ ER were within the range between cTEA ± 1º. In the MR Group, 88.4% of patients’ ER were within the range between sTEA ± 1º. Patellofemoral tracking conditions and requirement of lateral release (1.2% in MP group vs.2.0% in MR group) were not significantly different between the two groups (p = 0.7065)

Conclusion