MRI-based Texture Analysis of Infrapatellar Fat Pad to Predict Knee Osteoarthritis Incidence

Abstract

Background Infrapatellar fat pad (IPFP) quality has been implicated as a marker for predicting knee osteoarthritis (KOA); however, no valid quantification for subtle IPFP abnormalities has been established. Purpose To investigate whether MRI-based three-dimensional texture analysis of IPFP abnormalities could help predict incident radiographic KOA. Materials and Methods In this prospective nested case-control study, 690 participants whose knees were at risk for KOA were included from the Pivotal Osteoarthritis Initiative MRI Analyses incident osteoarthritis cohort. All knees had a Kellgren-Lawrence grade of 1 or less at baseline. During the 4-year follow-up, case participants were matched 1:1 to control participants, with incident radiographic KOA as the outcome. MRI scans were segmented at the incident time point of KOA (hereafter, P0), 1 year before P0 (hereafter, P-1), and baseline. MRI-based three-dimensional texture analysis was performed to extract IPFP texture features. Least absolute shrinkage and selection operator and multivariable logistic regressions were applied in the development cohort and evaluated in the test cohort. The area under the receiver operating characteristic curve (AUC) was used to evaluate the discriminative value of the clinical score, IPFP texture score, and MRI Osteoarthritis Knee Score. Results Participants were allocated to development (n = 500, 340 women; mean age, 60 years) and test (n = 190, 120 women; mean age, 61 years) cohorts. In both cohorts, IPFP texture scores (AUC ≥0.75 for all) showed greater discrimination than clinical scores (AUC ≤0.69 for all) at baseline, P-1, and P0, with significant differences in pairwise comparisons (P ≤ .002 for all). Greater predictive and concurrent validities of IPFP texture scores (AUC ≥0.75 for all) compared with MRI Osteoarthritis Knee Scores (AUC ≤0.66 for all) were also demonstrated (P < .001 for all). Conclusion MRI-based three-dimensional texture of the infrapatellar fat pad was associated with future development of knee osteoarthritis. ClinicalTrials.gov registration no.: NCT00080171 © RSNA, 2022 Online supplemental material is available for this article. See also the editorial by Fischer in this issue.

Graphical abstract

Figure 1:

Flowchart shows the recruitment pathway for participant knees. One case knee would be excluded along with the matched control due to lack of MRI or other records. BL = baseline, OA = osteoarthritis, P0 = incident time point of knee OA, P-1 = 1 year before P0, POMA = Pivotal OAI MRI Analyses.

Figure 2:

Illustration shows the image processing pipeline for three-dimensional (3D) texture analysis and visualization of infrapatellar fat pad (IPFP) texture. Numbers in parentheses are the number of texture features. ITK-SNAP and MATLAB software were used in this process. GLCM = gray-level co-occurrence matrix, RLM = run-length matrix, VOI = volume of interest.

Figure 3:

Receiver operating characteristic curves show the performance of infrapatellar fat pad (IPFP) texture scores compared with clinical scores in both cohorts. The curves shown are averages of 1000 cross-validated runs at three time points. Incident radiographic knee osteoarthritis (KOA) was discerned by using clinical scores, IPFP texture scores, and composite scores at baseline (BL), 1 year before the incident time point of KOA (P-1), and the incident time point of KOA (P0).

Figure 4:

Receiver operating characteristic curves show the performance of infrapatellar fat pad (IPFP) texture scores compared with MRI Osteoarthritis Knee Score (MOAKS) imaging markers in both cohorts. The curves shown are averages of 1000 cross-validated runs at three time points. Incident radiographic knee osteoarthritis was discerned by using the IPFP texture score compared with the MOAKS imaging markers at three time points. * = Cartilage damage and bone marrow lesions were scored on an incorporating scale in five articular subregions of the medial tibiofemoral compartment. † = Meniscal damage was scored on an incorporating scale in the anterior horn, body segment, and posterior horn of the medial meniscus, involving intrameniscal signal changes, meniscal tears, and meniscal maceration. BL = baseline, BML = bone marrow lesion, P0 = incident time point of knee osteoarthritis, P-1 = 1 year before P0.

Figure 5:

Example images show IPFP texture maps classified into different severities of Hoffa synovitis using the MRI Osteoarthritis Knee Score (MOAKS). (A–C) MOAKS = 0, IPFP texture score = –0.6769. (D–F) MOAKS = 1, IPFP texture score = –0.1758. (G–I) MOAKS = 2, IPFP texture score = 0.4273. (J–L) MOAKS = 3, IPFP texture score = 0.9446. Higher IPFP texture scores correspond to more spatial heterogeneity.