Session Type: Abstract Submissions (ACR)
Statistical Shape Modeling (SSM) is a promising tool that has the ability to characterize complex shapes in a brief feature vector. The application of SSM in 2D imaging is widely used, though 3D MRI application is still a challenge. Injury of the anterior cruciate ligament (ACL) is a high risk factor for developing post-traumatic osteoarthritis (OA). The aim of this study is to analyze the longitudinal shape changes of the tibia and femur in patients with ACL injuries using a novel MR-based SSM algorithm. We hypothesized that distinct shape changes are present one year following ACL injury.
Bilateral knees were scanned using a 3T MRI scanner (GE Healthcare) for 15 patients (29.3 ± 4.2 yrs, 5 female) with ACL injuries prior to surgical reconstruction, and at 6 and 12 months after reconstruction. 10 controls (30.5 ± 5.2 yrs , 3 female) with no history of knee injuries underwent MR imaging at baseline and 12 months later. The imaging protocol included sagittal T2 fast spin-echo (FSE) images with TR/TE = 4000/49.3 ms, resolution 0.39×0.39×1.5 mm, slice spacing of 1.5 mm. The SSM is extracted individually from the segmentation of tibia and femur. Each principal component analysis (PCA)’s mode of the model describes a different aspect of the bone shape. Starting from the mean mode’s vector we can return to the space domain after the perturbation of a single mode. This method allows for the identification of the specific shape feature that is described in each mode. The first 20 modes were analyzed. The difference in mode values between baseline, 6-month, and 12-month follow-up were compared to the changes in the control knees from baseline to 12 months. Unpaired t-tests were used to compare longitudinal changes in ACL-injured and control knees, with significance set at alpha less than 0.05.
The variation in Mode 10 for the tibia from baseline to 12 months is significantly different between injured (19.46 ± 28.83) patients and controls (-11.68 ± 22.18). The change in Mode 10 in the injured group occurs primarily in the second 6 months, as the variation between 6 and 12 month is 18.17± 33.31, which is significantly different as well. The variation of the same mode in the first 6 months is not significantly different (1.29 ± 22.18). A decrease of this mode is related with an expansion and elevation of the lateral tibial plateau.
The variation in Mode 12 for the femur from baseline to 6 months and 12 months is significantly different between injured patients (6 months: 15.28 ± 28.67, 12 month 21.67 ± 21.86) and controls (-4.85 ± 17.79). The change Mode 12 in the injured group occurs primarily in the first 6 months. A decrease of the mode value is related to a flattening of the lateral femoral condyle, and to an increase of the height in the intercondylar notch.
In this study the longitudinal shape changes in the femur and tibia in ACL patient was analyzed. The observed expansion and elevation of the lateral tibial plateau is similar to previously observed radiographic changes in patients with OA. Significant differences are also observed in the shape of the lateral femoral condyle following ACL injury. This novel methodology may lead to the development of imaging biomarkers for post-traumatic OA.
D. A. Lansdown,
C. B. Ma,
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ACR Meeting Abstracts - https://acrabstracts.org/abstract/osteoarthritis-like-changes-are-present-in-the-tibia-and-femur-1-year-following-acl-reconstruction/