Clinical Orthopaedics and Related Research®

, Volume 472, Issue 1, pp 248–253

Abnormal Axial Rotations in TKA Contribute to Reduced Weightbearing Flexion

  • Bradley Meccia
  • Richard D. Komistek
  • Mohamed Mahfouz
  • Douglas Dennis
Symposium: 2013 Knee Society Proceedings

DOI: 10.1007/s11999-013-3105-5

Cite this article as:
Meccia, B., Komistek, R.D., Mahfouz, M. et al. Clin Orthop Relat Res (2014) 472: 248. doi:10.1007/s11999-013-3105-5

Abstract

Background

Previous in vivo fluoroscopy studies have documented that axial rotation for patients having a TKA was significantly less than those having a normal knee. In fact, many subjects having a TKA experience a reverse axial rotation pattern where the femur internally rotates with increasing flexion. However, no previous studies have been conducted to determine if this reverse axial rotation pattern affects TKA performance.

Questions/purposes

The purposes of this study were: (1) Do normal and reverse axial rotation patterns of a TKA affect the maximum flexion angle postoperatively? (2) Does the axial rotation angle of the knee at maximum flexion during weightbearing impact the magnitude of the maximum flexion achieved in weightbearing?

Methods

One hundred twenty patients having TKA, previously analyzed under in vivo conditions using fluoroscopy and a three-dimensional model-fitting software package, were further evaluated to determine if reverse axial rotation patterns limit weightbearing TKA flexion. In this retrospective cohort, we identified 58 patients who had a normal axial rotation pattern (greater than 15° normal rotation). Sixty-two patients experienced greater than 3° of reverse axial rotation, defined as internal rotation of the femur relative to the tibia.

Results

Patients having a normal axial rotation achieved greater weightbearing knee flexion than those with reverse axial rotation (115° versus 109°, p = 0.02). Additionally, patients with greater than 3° of normal axial rotation at maximum flexion had more flexion than those with less than 3° of normal axial rotation at ending flexion (115° versus 107°, p < 0.001).

Conclusions

These findings show reverse axial rotation and a smaller magnitude of normal axial rotation reduce weightbearing knee flexion. This is likely the result of increased posterior movement of the lateral condyle and is an important consideration in future implant designs.

Level of Evidence

Level III, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

Copyright information

© The Association of Bone and Joint Surgeons® 2013

Authors and Affiliations

  • Bradley Meccia
    • 1
  • Richard D. Komistek
    • 1
  • Mohamed Mahfouz
    • 1
  • Douglas Dennis
    • 2
  1. 1.Department of Mechanical, Aerospace & Biomedical EngineeringUniversity of TennesseeKnoxvilleUSA
  2. 2.Colorado Joint ReplacementDenverUSA