Use of a novel magnetic resonance imaging based modeling technique to investigate differences in tibiofemoral articular cartilage contact area In subjects with moderate knee osteoarthritis
Date
2009
Authors
Henderson, Christopher
Journal Title
Journal ISSN
Volume Title
Publisher
University of Delaware
Abstract
Knee osteoarthritis (OA) detrimentally impacts the lives of millions of
older Americans through pain and decreased functional ability. Unfortunately, the
pathomechanics and associated changes that OA patients experience are not well
understood. Mechanical stress in the knee joint may play an essential role in OA;
however existing literature in this area is limited. Purpose: The purpose of this study
was two-fold. First, we wanted to evaluate an existing magnetic resonance imaging
(MRI) based modeling method’s estimation of articular cartilage contact area in vivo.
Secondly, we wanted to apply this method to a cohort of subjects with moderate knee
OA and compare their medial compartment articular cartilage contact area estimates
with healthy, age matched controls. Methods: In order to establish confidence in the
modeling method’s ability to estimate articular cartilage contact area, imaging data on
a single, healthy subject were collected and compared to existing contact area
estimates in the literature. Intra-observer reliability and sensitivity studies were also
performed in an attempt to further establish confidence in the method. In the second
half of this study, MRIs of the knee at 0°, 15°, and 30° flexion were collected during
partial-weightbearing in subjects with moderate knee OA (n = 11) and healthy, age
matched controls (n = 11). Articular cartilage contact area estimates were normalized
to an approximation of the surface area of the tibial plateau in order to account for
joint size differences between subjects. The relationship between medial compartment
articular cartilage contact area and knee flexion was investigated in each group.
Results: The single healthy subject was found to have articular cartilage contact areaestimates similar to those reported in the literature. The method was found to be
sensitive to changes in the cartilage tracings on the peripheries of the compartment and
demonstrated an intra-observer reliability of 0.95 when assessed using Pearson’s
correlation coefficient. In the second half of the study, medial compartment articular
cartilage contact area in the healthy controls was found to be significantly correlated
with knee flexion angle (p ≤ 0.01), while no such correlation was found in the
moderate OA subjects (p = 0.34). Linear regression analysis found that the moderate
knee OA subjects had higher articular cartilage contact areas than their healthy, control
counterparts across all flexion angles considered. Conclusions: Confidence was
established in the MRI based knee modeling method’s ability to estimate articular
cartilage contact area through a series of assessments and comparison with existing
literature on healthy subjects. Healthy subjects were found to have a significant
correlation between medial compartment articular cartilage contact area and knee
flexion, which agreed with the literature. The moderate OA subjects did not show the
same relationship between medial compartment articular cartilage contact area and
knee flexion. Regression analysis found that they had higher medial compartment
articular cartilage contact area estimates in all instances when compared with healthy
controls. Increased contact area may be a biomechanical adaptation in response to OA
in order to decrease the mechanical stress applied across the painful joint.