Cartilage lesion score: comparison of a quantitative assessment score with established semiquantitative MR scoring systems

Abstract

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.

Figure 1:

Illustrations show definitions of depth and shape scores, as well as diameter, with the CaLS system. Black = cartilage, gray = subchondral bone. A, A superficial lesion (less than 50% deep) is scored as 1. B, A lesion deeper than 50% is scored as 2. C, A full-thickness lesion is scored as 3. D, If maximum depth occupies less than 50% of the lesion, it is scored as 0.5. E, If maximum depth occupies 50% or more of the lesion, it is scored as 1. F, The largest diameter (double arrow) is measured.

Figure 2:

MR images show definitions of depth and shape scores, as well as diameter, with the CaLS system. A, A superficial lesion (<50% deep) (arrows) was given a depth score of 1 in a 53-year-old man. B, A lesion deeper than 50% (arrows) was given a depth score of 2 in a 55-year-old woman. C, A full-thickness lesion (arrows) was given a depth score of 3 in a 53-year-old woman. D, If maximum depth (arrows) occupies less than 50% of the lesion, as in this 55-year-old man, it is scored as 0.5. E, Otherwise, maximum depth (arrows) is scored as 1, as in this 52-year-old woman. F, Largest diameter (double arrow) is measured in a 56-year-old woman.

Figure 3:

Sagittal intermediate-weighted fast spin-echo MR images of the right knee in a 49-year-old woman from the OAI incidence cohort show a patellar lesion that progressed with the CaLS system but not with the WORMS or BLOKS systems. At both, A, baseline and, B, 24-month follow-up, the lesion was scored as WORMS grade 3 and BLOKS grade 2. With the CaLS system, the lesion measured 11 mm at baseline and had a partial thickness of less than 50%; at 24-month follow-up, the lesion measured 14 mm and had a partial thickness of more than 50%.