Compositional evaluation of lesion and parent bone in patients with juvenile osteochondritis dissecans of the knee using T₂* mapping

Abstract

Juvenile osteochondritis dissecans (JOCD) lesions contain cartilaginous, fibrous and osseous tissues which are difficult to distinguish with clinical, morphological magnetic resonance imaging (MRI). Quantitative T2* mapping has earlier been used to evaluate microstructure and composition of all aforementioned tissues as well as bone mineral density. However, the ability of T2* mapping to detect changes in tissue composition between different JOCD lesion regions, different disease stages, and between stable and unstable lesions has not been demonstrated. This study analyzed morphological and T2* MRI data from 25 patients (median age, 12.1 years) with 34 JOCD‐affected and 13 healthy knees. Each lesion was assigned a stage reflecting the natural history of JOCD, with stages I and IV representing early and healed lesion, respectively. T2* values were evaluated within the progeny lesion, interface and parent bone of each lesion and in the control bone region. T2* was negatively correlated with JOCD stage in progeny lesion (ρ = −0.871; p < 0.001) and interface regions (ρ = −0.649; p < 0.001). Stage IV progeny showed significantly lower T2* than control bone (p = 0.028). T2* was significantly lower in parent bone than in control bone of patients with stable lesions (p = 0.009), but not in patients with unstable lesions (p = 0.14). Clinical significance: T2* mapping enables differentiation between different stages of JOCD and quantitative measurement of the ossification degree in progeny lesion and interface. The observed T2* decrease in healed and stable lesions may indicate increased bone density as a result of the active repair process. T2* mapping provides quantitative information about JOCD lesion composition.

Longitudinal 3T MRI T2* mapping of Juvenile osteochondritis dissecans (JOCD) lesions differentiates operative from non‐operative patients—Pilot study

“…A fellowship‐trained musculoskeletal radiologist with 15 years of experience evaluated the MRI scans for adequate image quality, absence of artifacts and assigned each lesion to a JOCD stage (I–IV) (Figure 2) according to a previously reported staging system 6,17 . The reproducibility of the staging system has been reported in our previous T 2 * study 17 with high inter‐rater agreement (88%). The radiologist had access to the morphological MRI and short TE GRE images with CT‐like contrast but was blinded to the patient name, age, date of the study, and the T 2 * maps.…”

“…The included JOCD patients ( n = 13, mean age: 12.3 years, range: 5–18 years, 4 females) (Table 1) had no signs of knee osteoarthritis or malignancy, no previous surgery and no significant artifacts were detected on MRI. Six baseline patients and six follow‐up patients included into this study were previously published 17 . However, there was absolutely no overlap in data analysis, and the outcomes are completely different as the current study evaluates longitudinal changes in JOCD lesion volumes with T 2 * mapping.…”

“…A multislice multiecho gradient recalled echo (GRE) sequence (Table 2) was acquired to calculate T 2 * relaxation times. The contrast in GRE images with the shortest attainable echo time (acquired within this sequence) was inverted to provide the CT‐like contrast, a contrast similar in appearance to what is known as ‘bone window' in CT 6,17 (Figure 2).…”

“…Manual 3D segmentations of the entire JOCD lesion volume were performed on the GRE images with the shortest TE using ITK‐SNAP, 17,28 with the reader having access to morphological MRI but not to the T 2 * maps. As reported previously, 17 three distinct regions within the JOCD lesion complex including progeny lesion, the adjacent parent bone and interface between them were segmented as shown in (Figure 3A). The control bone region was segmented within trabecular bone of the contralateral, lesion‐free, femoral condyles (Figure 3A) and contralateral healthy knees of included patients with bilateral knee MRI.…”

“…Ellermann et al introduced a new staging system for JOCD and hypothesized that the system captured the natural history of the disease from epiphyseal cartilage origin (stage I) to osseous manifestation (stages II–IV) utilizing the concept of short TE sequences with CT‐like contrast., including quantitative T 2 * mapping 6 . It has been subsequently demonstrated in a recent cross‐sectional study 17 that T 2 * values were negatively correlated with JOCD stage in progeny lesion and interface and decreased T 2 * in healed and stable lesions indicated increased bone density because of the active osseous repair.…”