Biomechanical Effects of Component Alignment Variability in Total Knee Arthroplasty

111 Pages·2012·2.3 MB·English

by  Sean Paul Lemke

Biomechanical Effects of Component Alignment Variability in Total
Knee Arthroplasty: A Computer Simulation Study of an Oxford Rig

THESIS

Presented in Partial Fulfillment of the Requirements for the Degree Master of Science in
the Graduate School of The Ohio State University

By
Sean Paul Lemke, B.S.
Graduate Program in Mechanical Engineering

The Ohio State University
2012

Master's Examination Committee:
Robert A. Siston, Advisor
Matthew D. Beal
Ajit M.W. Chaudhari
Copyright by
Sean Paul Lemke
2012
Abstract

Success in total knee arthroplasty (TKA) depends on several factors including the
patient’s pre-operative condition, sex, and proper post-operative rehabilitation, but
perhaps the most crucial factor is proper component alignment. Alignment of the femoral
and tibial components in TKA is highly variable due to difficulty in identifying
anatomical landmarks and debate on how the components should be aligned. The purpose
of this thesis was to examine the biomechanical effects of the variability in femoral and
tibial component alignment in the three anatomical planes. This was done using a
forward-dynamic computer model of an Oxford Rig device with a cruciate-retaining
version of the Scorpio implant from Stryker Orthopaedics digitally implanted. The
Oxford Rig has 6 degrees of freedom at the knee and simulates flexed knee stance, which
is similar to what occurs during functional activities such as riding a bicycle or climbing
stairs.
In order to examine the relationship between femoral and tibial component
alignment and knee biomechanics, we ran three rounds of simulations: changing the
alignment of one component in one plane, changing alignment of both components in one
plane, and changing the alignment of one component in multiple planes. The effects of
component alignment were examined on patellofemoral kinematics and contact force,
tibiofemoral kinematics and contact force, ligament forces, and quadriceps force. The
alignment of the femoral component in the transverse plane had the greatest effect on a
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majority of the variables of interest including patellofemoral and tibiofemoral kinematics,
contact forces, and MCL force. Frontal plane alignment of the femoral and tibial
component impacts the forces in both collateral ligaments in early flexion. Sagittal plane
alignment of the tibial component has the greatest effect on the PCL. Alignment of the
femoral component in the sagittal plane has the greatest effect on quadriceps force.
The results of the simulations were used to develop mathematical models that can
be used to describe effects of changing component alignment at a given knee flexion
angle. In order to develop these equations, best fit polynomials were found for the curves
of the variable of interest with respect to knee flexion angle. The polynomial coefficients
were then regressed against component alignments. These mathematical models were
developed to make the information found using the Oxford Rig simulation more
accessible.
Our findings suggest that variability in component alignment, especially
transverse plane alignment of the femoral component and frontal plane alignment of both
components, can impact post-operative performance. This thesis highlights the
importance for properly establishing the rotational alignment of the femoral and tibial
components in TKA.

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Acknowledgments

There are several people that I would like to thank for their help throughout my time at
OSU.
• My advisor, Rob Siston, for all of his guidance.
• My committee members, Ajit Chaudhari and Matthew Beal, for their input and
advice.
• Steve Piazza for all of his help with the Oxford Rig simulation.
• Jeff Pan for his help with the data analysis process.
• Julie Thompson for helping me throughout the entire process whenever I had a
question.
• Megan Nesline for the helping me to run all of my simulations.
• All of my labmates in the Neuromuscular Biomechanics Lab.
• My friends and family.

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Vita

May 2006 .......................................................Pickerington High School North
May 2010 .......................................................B.S. Mechanical Engineering, Ohio
Northern University
September 2010 to September 2011 ..............University Fellow, The Ohio State
University
September 2011 to present ............................Graduate Research Associate, Department
of Mechanical Engineering, The Ohio State
University

Fields of Study

Major Field: Mechanical Engineering

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Table of Contents
Abstract ............................................................................................................................... ii
Acknowledgments.............................................................................................................. iv
Vita ...................................................................................................................................... v
Table of Contents ............................................................................................................... vi
List of Tables ................................................................................................................... viii
List of Figures ..................................................................................................................... x
Chapter 1: Introduction ....................................................................................................... 1
1.1 Osteoarthritis and Total Knee Arthroplasty .............................................................. 1
1.2 Surgical technique of TKA component orientation .................................................. 2
1.3 Significance of Research ........................................................................................... 5
1.4 Focus of Thesis .......................................................................................................... 8
1.5 Overview of Thesis ................................................................................................... 8
Chapter 2: Methods ........................................................................................................... 10
2.1 Data Analysis .......................................................................................................... 14
Chapter 3: Results ............................................................................................................. 16
3.1 General Regression Analysis .................................................................................. 16
3.2 Knee Varus/Valgus angle ........................................................................................ 17
3.3 Knee Internal/External angle ................................................................................... 21
3.4 Patellar Tilt .............................................................................................................. 26
3.5 Patellar Medial/Lateral Location ............................................................................. 30
3.6 Medial Collateral Ligament (MCL) Force .............................................................. 35
3.7 Lateral Collateral Ligament (LCL) Force ............................................................... 39
3.8 Posterior Cruciate Ligament (PCL) Force .............................................................. 43
3.9 Quadriceps Force ..................................................................................................... 48
3.10 Tibiofemoral Contact Force .................................................................................. 54
3.11 Patellofemoral Contact Force ................................................................................ 57
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3. 12 Mathematical Models ........................................................................................... 61
3.12.1 Knee Varus/Valgus Angle .............................................................................. 62
3.12.2 Knee Internal/External Angle ......................................................................... 65
3.12.3 Medial Collateral Ligament (MCL) Force ..................................................... 69
3.12.4 Lateral Collateral Ligament (LCL) Force ...................................................... 74
3.12.5 Posterior Cruciate Ligament (PCL) Force ...................................................... 77
3.12.6 Quadriceps Force ............................................................................................ 80
3.13 Discussion ............................................................................................................. 84
Chapter 4: Conclusions ..................................................................................................... 89
4.1 Contributions ........................................................................................................... 90
4.2 Additional Applications .......................................................................................... 91
4.3 Future work ............................................................................................................. 92
4.4 Summary ................................................................................................................. 93
References ......................................................................................................................... 94

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List of Tables

Table 1: Number of simulations ran for the first two rounds. ....................................................... 13
Table 2: Number of simulations ran for the third round. .............................................................. 14
Table 3: Alignment factors contributing to Biomechanical Parameters (largest coefficient in
bold) ............................................................................................................................................... 16
Table 4: Regression coefficients for knee varus/valgus angle. Coefficient units are (degrees knee
varus/valgus)/(degrees component rotation). ................................................................................. 17
Table 5: Regression coefficients for knee internal/external angle. Coefficient units are (degrees
knee internal/external)/(degrees component rotation). .................................................................. 22
Table 6: Regression coefficients for patellar medial/lateral tilt. Coefficient units are (degrees
patellar tilt)/(degrees component rotation). .................................................................................... 26
Table 7: Regression coefficients for patellar medial/lateral location. Coefficient units are
(mm)/(degrees component rotation). ............................................................................................. 31
Table 8: Regression coefficients for MCL force. Coefficient units are (N)/(degrees component
rotation). ......................................................................................................................................... 35
Table 9: Regression coefficients for LCL force. Coefficient units are (N)/(degrees component
rotation). ......................................................................................................................................... 39
Table 10: Regression coefficients for PCL force. Coefficient units are (N)/(degrees component
rotation). ......................................................................................................................................... 43
Table 11: Regression coefficients for quadriceps force. Coefficient units are (N)/(degrees
component rotation). ...................................................................................................................... 49
Table 12: Regression coefficients for tibiofemoral contact force. Coefficient units are
(N)/(degrees component rotation). ................................................................................................. 54
Table 13:Regression coefficients for patellofemoral contact force. Coefficient units are
(N)/(degrees component rotation). ................................................................................................. 58
Table 14: List of coefficients used to determine knee varus/valgus angle at a given knee flexion
angle (x). ........................................................................................................................................ 62
Table 15: Evaluation of the difference between simulation data and model estimates for knee
varus/valgus angle. ......................................................................................................................... 64
Table 16: List of coefficients used to determine knee internal/external angle at a given knee
flexion angle (x). ............................................................................................................................ 66
Table 17: Evaluation of the difference between simulation data and model estimates for knee
internal/external angle. ................................................................................................................... 68
Table 18:List of coefficients used to determine MCL force at a given knee flexion angle (x)..... 70
Table 19: Evaluation of the difference between simulation data and model estimates for MCL
force ............................................................................................................................................... 71
Table 20:List of coefficients used to determine LCL force at a given knee flexion angle (x). ..... 75
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Table 21: Evaluation of the difference between simulation data and model estimates for LCL
force. .............................................................................................................................................. 76
Table 22: List of coefficients used to determine PCL force at a given knee flexion angle (x). .... 78
Table 23: Evaluation of the difference between simulation data and model estimates for PCL
force ............................................................................................................................................... 79
Table 24: List of coefficients used to determine quadriceps force at a given knee flexion angle
(x). .................................................................................................................................................. 81
Table 25: Evaluation of the difference between simulation data and model estimates for PCL
force ............................................................................................................................................... 83

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