Objective

To evaluate trochlear morphology as a potential risk factor for patellofemoral osteoarthritis, determined by morphological and quantitative measurements of cartilage degeneration using 3-T magnetic resonance imaging (MRI) of the knee.

Materials and methods

MRI of the right knees of 304 randomly selected subjects, aged 45-60 years, from the Osteoarthritis Initiative (OAI) progression cohort were screened for trochlear dysplasia, defined by an abnormal trochlear depth. Out of 304 subjects, n = 85 demonstrated a shallow trochlea (depth ≤3 mm; 28 %). In these, and also in a random sample of controls with normal trochlear depth (n = 50), the facet ratio and the sulcus angle were calculated and knee structural abnormalities were assessed by using a modified Whole Organ MR Imaging Score (WORMS). Cartilage segmentation was performed and T2 relaxation times and patellar cartilage volume were determined. ANOVA and multivariate regression models were used for statistical analysis of the association of MRI structural measures and trochlear morphology.

Results

Knees with a shallow trochlea showed higher patellofemoral degeneration (WORMS mean ± standard deviation, 11.2 ± 0.5 versus 5.7 ± 0.6; multivariate regression, P < 0.001) and lower patellar cartilage volume than controls (900 ± 664 mm(3) versus 1,671 ± 671 mm(3); P < 0.001). Knees with an abnormal medial-to-lateral facet ratio (<0.4) showed increased patellofemoral WORMS scores (12.3 ± 0.9 versus 8.3 ± 0.5; P < 0.001). Knees with an abnormal sulcus angle (>170°) also showed increased WORMS scores (12.2 ± 1.1 versus 8.6 ± 0.6; P = 0.003). T2 values at the patella were significantly lower in the dysplasia group with a shallow trochlea. However, significance was lost after adjustment for cartilage volume (P = 0.673).

Conclusion

Trochlear dysplasia, defined by a shallow trochlea, was associated with higher WORMS scores and lower cartilage volume, indicating more advanced osteoarthritis at the patellofemoral joint.

Purpose

To describe a scoring system for quantification of cartilage lesions (Cartilage Lesion Score [CaLS]), to determine its reproducibility, to examine the association of CaLS-detected longitudinal change with known risk factors for osteoarthritis (OA) progression by comparing a group of subjects with OA risk factors with a group of subjects without OA risk factors, and to compare the CaLS system with the established semiquantitative Whole-Organ Magnetic Resonance Imaging Score (WORMS) and Boston-Leeds Osteoarthritis Knee Score (BLOKS) systems in terms of detection of cartilage defect progression.

Materials and methods

All subjects provided written informed consent, and the local institutional review board approved this HIPAA-compliant study. Fifty-two subjects with and 25 subjects without risk factors for knee OA were randomly selected from the Osteoarthritis Initiative. Inclusion criteria were age of 45-60 years, body mass index of 19-27 kg/m(2), and no knee pain or OA on radiographs at baseline. Baseline and 24-month follow-up right knee 3-T magnetic resonance images were analyzed with WORMS, BLOKS, and CaLS systems. Progression of cartilage lesions with each scoring system was compared by using multilevel mixed-effects linear-regression models. κ values were calculated to determine reliability.

Results

Intraclass coefficient values for inter- and intraobserver reliability of the CaLS system were 0.86 and 0.91, respectively. Interobserver κ value range for individual features was 0.81-0.94. The CaLS system enabled significantly higher detection of cartilage lesion progression than did WORMS or BLOKS systems (P < .001); 51.8% (56 of 108), 17.6% (19 of 108), and 13.0% (14 of 108) of the lesions progressed when analyzed with the CaLS, WORMS, and BLOKS systems, respectively. With the CaLS system, subjects with OA risk factors had significantly higher odds of progression than did subjects without risk factors (odds ratio, 2.78; P = .005).

Conclusion

The CaLS system is a reproducible scoring system for cartilage lesions that yields an improved detection rate for monitoring progression when compared with detection rates of semiquantitative WORMS and BLOKS systems.

Purpose

To assess lesion detection and artifact size reduction of a multiacquisition variable-resonance image combination, slice encoding for metal artifact correction (MAVRIC-SEMAC) hybrid sequence (MAVRIC-SL) compared to standard sequences at 1.5T and 3T in porcine knee specimens with metal hardware.

Materials and methods

Artificial cartilage and bone lesions of defined size were created in the proximity of titanium and steel screws with 2.5 mm diameter in 12 porcine knee specimens and were imaged at 1.5T and 3T magnetic resonance imaging (MRI) with MAVRIC-SL PD and short T1 inversion recovery (STIR), standard fast spin echo (FSE) T2 PD, and STIR and fat-saturated T2 FSE sequences. Three radiologists blinded to the lesion locations assessed lesion detection rates on randomized images for each sequence using receiver operating characteristic (ROC). Artifact length and width were measured.

Results

Metal artifact sizes were largest in the presence of steel screws at 3T (FSE T2 FS: 28.7 cm(2) ) and 1.5T (16.03 cm(2) ). MAVRIC-SL PD and STIR reduced artifact sizes at both 3T (1.43 cm(2) ; 2.46 cm(2) ) and 1.5T (1.16 cm(2) ; 1.59 cm(2) ) compared to FS T2 FSE sequences (27.57 cm(2) ; 13.20 cm(2) ). At 3T, ROC-derived AUC values using MAVRIC-SL sequences were significantly higher compared to standard sequences (MAVRIC-PD: 0.87, versus FSE-T2 -FS: 0.73 [P = 0.025]; MAVRIC-STIR: 0.9 vs. T2 -STIR: 0.78 [P = 0.001] and vs. FSE-T2 -FS: 0.73 [P = 0.026]). Similar values were observed at 1.5T. Comparison of 3T and 1.5T showed no significant differences (MAVRIC-SL PD: P = 0.382; MAVRIC-SL STIR: P = 0.071).

Conclusion

MAVRIC-SL sequences provided superior lesion detection and reduced metal artifact size at both 1.5T and 3T compared to conventionally used FSE sequences. No significant disadvantage was found comparing MAVRIC-SL at 3T and 1.5T, although metal artifacts at 3T were larger. J. Magn. Reson. Imaging 2015;41:1291-1299. © 2014 Wiley Periodicals, Inc.

Purpose

To study the natural evolution of cartilage T2 relaxation times in knees with various extents of morphological cartilage abnormalities, assessed with 3 Tesla MRI from the Osteoarthritis Initiative.

Materials and methods

Right knee MRIs of 245, 45- to 60-year-old individuals without radiographic osteoarthritis (OA) were included. Cartilage was segmented and T2 maps were generated in five compartments (patella, medial and lateral femoral condyle, medial, and lateral tibia) at baseline and 2-year follow-up. We examined the association of T2 values and 2-year change of T2 values with various Whole-Organ MR Imaging Scores (WORMS). Statistical analysis was performed with analysis of variance and Students t-tests.

Results

Higher baseline T2 was associated with more severe cartilage defects at baseline and subsequent cartilage loss (P < 0.001). However, longitudinal T2 change was inversely associated with both baseline (P = 0.038) and follow-up (P = 0.002) severity of cartilage defects. Knees that developed new cartilage defects had smaller increases in T2 than subjects without defects (P = 0.045). Individuals with higher baseline T2 showed smaller T2 increases over time (P < 0.001).

Conclusion

An inverse correlation of longitudinal T2 changes versus baseline T2 values and morphological cartilage abnormalities suggests that once morphological cartilage defects occur, T2 values may be limited for evaluating further cartilage degradation.

Objective

To evaluate whether T2 relaxation time measurements obtained at 3 T MRI predict the onset of radiographic knee osteoarthritis (OA).

Materials and methods

We performed a nested case-control study of incident radiographic knee OA in the Osteoarthritis Initiative cohort. Cases were 50 knees with baseline Kellgren-Lawrence (KL) grade of 0 that developed KL grade of 2 or more over a 4-year period. Controls were 80 knees with KL grade of 0 after 4 years of follow-up. Baseline T2 relaxation time measurements and laminar analysis of T2 in deep and superficial layers were performed in all knee compartments. The association of T2 values with incident OA was assessed with logistic regression and differences in T2 values by case-control status with linear regression, adjusting for age, sex, body mass index (BMI) and other covariates.

Results

Baseline T2 values in all compartments except the medial tibia were significantly higher in knees that developed OA compared with controls and were particularly elevated in the superficial cartilage layers in all compartments. There was an increased likelihood of incident knee OA associated with higher baseline T2 values, particularly in the patella, adjusted OR per 1 SD increase in T2 (3.37 (95% CI 1.72 to 6.62)), but also in the medial femur (1.90 (1.07 to 3.39)), lateral femur (2.17 (1.11 to 4.25)) and lateral tibia (2.23 (1.16 to 4.31)).

Conclusions

These findings suggest that T2 values assessed when radiographic changes are not yet apparent may be useful in predicting the development of radiological tibiofemoral OA.

Purpose

To assess whether changes in knee cartilage MR-based T2 relaxation times are associated with weight loss in individuals with risk factors for knee osteoarthritis (OA) compared with controls with stable weight.

Materials and methods

One hundred twenty-seven individuals with risk factors for knee OA were studied: 62 subjects had a body mass index (BMI) decrease≥10% over 48 months and 65 controls had a BMI change <3%. Cartilage segmentation from five knee compartments at baseline and 48-month follow-up was performed, and T2 maps were generated. The association of change in T2 values over 48 months in the weight-loss group versus the control group was assessed using multiple linear regression models.

Results

Weight loss was associated with significantly smaller increases in cartilage T2 in the medial femoral condyle (P = 0.035) and overall medial compartment (P = 0.006) compared with the controls. In a subgroup analysis comparing weight-loss subjects who were obese (BMI≥30 kg/m(2) ) and overweight (BMI 25-30 kg/m(2) ) at baseline, obesity was associated with smaller increases in cartilage T2 values in the medial femoral condyle (P = 0.022), lateral femoral condyle (P = 0.015), patella (P = 0.002), and globally across all compartments (P = 0.002).

Conclusion

A decrease in BMI of ≥ 10% was associated with a slower progression of T2 values in individuals with risk factors for OA, suggesting a beneficial impact of weight loss on cartilage matrix degeneration.