2015 ISAKOS Biennial Congress ePoster #1229

Outcomes Following ACL Injuries And Reconstructions – A Comprehensive Evaluation Using Quantitative MRI Techniques.

C. Benjamin Ma, MD, San Francisco, CA UNITED STATES
Drew Lansdown, MD, San Francisco, CA UNITED STATES
Valentina Pedoia, PhD, San Francisco, CA UNITED STATES
Brian Chei-Fai Lau, MD, Durham, NC UNITED STATES
Favian Su, BS, Pittsburgh, PA UNITED STATES
Richard Souza, PhD, San Francisco, CA UNITED STATES
Xiaojuan Li, PhD, San Francisco, CA UNITED STATES
University of California, San Francisco, San Francisco, CA, USA

FDA Status Not Applicable

Summary: Quantitative MR imaging to evaluate knee kinematics, bone shape and cartilage health allow us to determine outcomes following ACL injured and reconstructed knees. Anterior tibial translation in extension, lateral tibial slope can predispose early cartilage injuries and persistent joint laxity. Cartilage health of posterolateral tibia after injury, female and age can affect outcomes after ACL

Abstract:

Introduction

Injuries to the ACL have been shown to lead to early osteoarthritic changes, persistent knee symptoms and loss of function. Quantitative kinematic MRI measures knee kinematics with anterior tibial translation and tibial rotation under load. Bone shape modeling investigate specific bone shape that predisposes patients to ACL injuries and persistent laxity. Lastly, quantitative T1? MR imaging can allow us to evaluate cartilage health prior to macromolecular changes. Our current project is an early report of a 3 year NIH funded study to evaluate outcomes following ACL injuries and reconstructions. We hypothesize that changes in knee kinematics can lead to early cartilage damage and specific bone shape can predispose patients to ACL injuries and persistent laxity.

Methods

The study group consisted of 54 patients who suffered an acute ACL tear and subsequently underwent ACL reconstruction. Subjects were evaluated after ACL-injury (54 pts), 6 months (42 pts) 1- year (30 pts), 2-years (10 pts) following ACL reconstructions with 3.0T MRI . Knee kinematic measurements including anterior tibial translation (ATT) and internal tibial rotation (ITR) were calculated from T2 fast spin echo MR images. To compute the statistical bone shape model, a three-dimensional triangulated mesh was extracted from the tibia and femur cloud points. The statistical shape modeling was extracted from these landmarks to generate 20 modes. These modes were considered for the description of the tibia and femur shapes. T1? relaxation times were quantified using in-house semi-automatic software into defined subcompartments. Patient reported outcomes were obtained with the KOOS survey at each time point. Statistical evaluation was performed between parameters in knee kinematics, different shape modes, T1? cartilage health of each subcompartments and KOOS outcome. A p-value of less than 0.05 was defined to have statistical significance.

Results

One year following ACL reconstruction, for the side-to-side difference of the tibial position in the extended state. A more posteriorly positioned tibia correlated with the side-to-side difference in cartilage T1? in the pMFC [Rho= -0.636 p=0.048]. For statistical shape modeling, mode Tibia 14 (T14) emerged as the most important mode in the prediction of both ATT in extension and side to side difference in ATT at baseline. When considering only the ten patients that completed the 2 years visit, the longitudinal correlation of ATT showed no significance between baseline and 1 year (R2=0.21, p>0.05), but showed a significant correlation between baseline and 2 years (R2=0.48, p=0.27). Baseline cartilage injury to the posterior lateral-tibia measured by T1? was a predictor of 1 year KOOS Pain, ADL, and Sport subscores. The strongest predictor was gender for KOOS sport score; being female was associated with a KOOS sport score that was 10.8 points lower than men. Women had significantly lower KOOS sport (p=0.01) and KOOS symptoms (p=0.02) and had significantly greater cartilage damage.

Discussion

This is a preliminary report for the 3 year longitudinal study. Increase ATT correlated with cartilage degeneration seen in the medial compartment. This is consistent with clinical findings, however, changes were evident at one year. The T14 mode, related to an increase in lateral tibial slope, correlates positively with increase ATT at baseline and 2 years. Acute cartilage degeneration as detected by T1? imaging at the posterolateral tibia, age, and gender in ACL-injured subjects was predictive of patient-reported outcomes at 1 year. The ability to predict which patients may have poorer outcomes or prolonged recovery will assist clinicians in setting realistic expectations and identify at risk population following injury and surgery