2015 ISAKOS Biennial Congress ePoster #1339

Alterations in In Vivo Knee Cartilage Contact After Anterior Cruciate Ligament Reconstruction and Correlations to Clinical Outcomes and Cartilage Morphology

Eric Thorhauer, BS, Seattle, WA UNITED STATES
Kimberly Sass, BS, Pittsburgh, PA UNITED STATES
Andrew Sivaprakasam, BS, Pittsburgh, PA UNITED STATES
James J. Irrgang, PT, PhD, FAPTA, Pittsburgh, PA UNITED STATES
Freddie H. Fu, MD, Pittsburgh, PA UNITED STATES
Scott Tashman, PhD, Pittsburgh, PA UNITED STATES

University of Pittsburgh, Pittsburgh, PA, USA

FDA Status Not Applicable

Summary: Early detection of alterations in articular cartilage contact during functional tasks and the morphological response of the cartilage is an essential component in understanding the processes that initiate osteoarthritis and provide insight into its underlying causes and possible avenues for treatment.

ePoster Not Provided
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Abstract:

Introduction

Accurately quantifying changes in joint behavior and cartilage thickness is an important step to better understand the development of post-traumatic osteoarthritis. It is unknown whether anatomic anterior cruciate ligament (ACL) reconstruction can fully restore knee function and prevent the degradation of the joint. The purpose of this study was to assess in vivo knee cartilage morphology and behavior during a functional, dynamic activity following anatomic ACL reconstruction.

Methods

Anatomic quadriceps bone block ACL reconstructions (ACL-R) were performed on 50 patients (mean age 22±7.5 years). All patients were assessed using the IKDC and KOOS scales and performed kinematic testing (gait/running) 6 months after reconstruction. Tibiofemoral kinematics and cartilage contact were derived using a dynamic stereo x-ray method. Compartmental contact area, contact centroid, and cartilage strain were calculated for the early to midstance phases. Articular cartilage thickness was measured from MRI. Differences between limbs were assessed using a repeated-measures ANOVA model (limb state x % gait cycle) for contact area and centroid location, while paired t-tests were employed to compare side-to-side differences in regional strains and cartilage thicknesses. Pearson correlations explored relationships between patient-reported outcomes scores, joint contact/kinematics, and cartilage thickness (alpha=0.05).

Results

Contact area in the medial compartment was smaller in ACL-R knees than contralateral limbs (p=0.075). Contact centroids were not significantly different. Strain was significantly decreased in ACL-R medial (p=0.014) and increased in lateral (p=0.013) femoral weight-bearing regions. Lateral tibia posterior region strain decreased (p=0.006), while other lateral compartment regions saw increased strain (all p<0.05). KOOS Activities of Daily Living scores were positively correlated with increased lateral compartment (R=0.38, p=0.01) and medial compartment (R=0.36, p=0.017) contact area. Increased medial contact area was correlated with better KOOS Pain Scores (R=0.31, p=0.04). ACL-R femoral cartilage thickness was 3.4-8.3% thinner. A mixture of swelling and thinning occurred in tibial cartilage. More anterior translation was correlated with medial tibial anterior (R=0.32, p=0.03) thickening (8.3%) and medial tibial internal compartment (R=0.53, p<0.001) cartilage thickening (14.8%).

Discussion

These results indicate relationships between altered knee kinematics/joint contact and cartilage morphological response early (6 months) after anatomic ACL reconstruction. Shifts in joint contact, whereby previously underloaded cartilage now bears greater load and vice versa, are thought to be the catalysts for osteoarthritis initiation. The correlations between increased area of contact and improved activity and pain scores support the idea that maintaining pre-injury levels of joint contact, and therefore load distribution across the joint, is important for good patient outcomes. The changes in strain patterns and cartilage thickness are multifactorial, and whether these initial trends persist and the implications they have for cartilage and meniscal degradation will be assessed with 2-year follow-up quantitative MRI and kinematic testing.