Can in vitro systems capture the characteristic differences between the flexion–extension kinematics of the healthy and TKA knee?

Varadarajan, Kartik M.; Harry, Rubash E.; Johnson, Todd; Li, Guoan

doi:10.1016/j.medengphy.2009.06.005

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Volume 31, Issue 8 , Pages 899-906, October 2009

Can in vitro systems capture the characteristic differences between the flexion–extension kinematics of the healthy and TKA knee?

Kartik M. Varadarajan
- Bioengineering Laboratory, Department of Orthopaedic Surgery, Massachusetts General Hospital and Harvard Medical School, Boston, MA, United States
- Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, MA, United States
Rubash E. Harry
- Bioengineering Laboratory, Department of Orthopaedic Surgery, Massachusetts General Hospital and Harvard Medical School, Boston, MA, United States
Todd Johnson
- Zimmer Inc., Warsaw, IN, United States
Guoan Li
- Bioengineering Laboratory, Department of Orthopaedic Surgery, Massachusetts General Hospital and Harvard Medical School, Boston, MA, United States
- Corresponding author at: Bioengineering Laboratory, MGH/Harvard Medical School, 55 Fruit St., GRJ 1215, Boston, MA 02114, United States. Tel.: +1 617 726 6472; fax: +1 617 724 4392.

Received 7 January 2009; received in revised form 7 April 2009; accepted 17 June 2009. published online 13 July 2009.

Abstract

In vitro systems provide a powerful means to evaluate the efficacy of total knee arthroplasty (TKA) in restoring normal knee kinematics. The Oxford knee rig (OKR) and the robotic knee testing system (RKTS) represent two systems that have been extensively used to study TKA biomechanics. Nonetheless, a frequently asked question is whether in vitro simulations can capture the in vivo behavior of the knee. Here, we compared the flexion–extension kinematics of intact knees and knees after TKA tested on the OKR and RKTS, to results of representative in vivo studies. The goal was to determine if the in vitro systems could capture the key kinematic features of knees in healthy subjects and TKA patients. Results showed that the RKTS and the OKR can replicate the femoral rollback and ‘screw home’ tibial rotation between 0° and 30° flexion seen in healthy subjects, and the reduced femoral rollback and absence of ‘screw home’ motion in TKA patients. The RKTS also replicated the overall internally rotated position of the tibia beyond 30° flexion. However, ability of the OKR to replicate the internally rotated position of the knee beyond 30° flexion was inconsistent. These data could aid in validation of new in vitro systems and physiologic interpretations of in vitro results.

Keywords: Knee kinematics, Oxford knee rig, Robotic testing system, Total knee arthroplasty