A newly created atlas for the scoring and assessment of osteoarthritis of the first metatarsophalangeal joint, using magnetic resonance imaging (MRI), has demonstrated really good intra- and inter-examiner reproducibility, suggesting that this system can be used to better understand the causes of, and develop treatment for, osteoarthritis pain of this joint. Results from this study were recently published in Arthritis Care and Research.

Investigators obtained MRI images from 60 participants: 30 with symptomatic first metatarsophalangeal joint osteoarthritis and 30 asymptomatic volunteers matched for sex, age, and body mass index (BMI). A radiologist developed MRI procedures, which were performed without contrast. Podiatrists and radiologists developed the MRI atlas to determine the included items and scoring.

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To determine reproducibility, 30 MRIs were randomly selected from the total sample. The selected images were from 19 women and 11 men (mean age 58.8±9.7 years) with a mean BMI of 28.7±5.0. Inter-examiner reproducibility was determined by 2 examiners who used the atlas to independently rate the MRIs. Eight to 12 weeks later, the same examiners repeated the process, without referencing the previous ratings, to determine the intra-examiner reproducibility.

Between both examiners, intra-examiner reproducibility was fair to perfect, with an agreement percentage ranging from 67% to 100% and Gwet’s AC1 values ranging from 0.38 to 1.00. Inter-examiner reproducibility was less than intra-examiner reproducibility — fair to almost perfect — with an agreement percentage ranging from 67% to 98% and Gwet’s AC1 values from 0.40 to 0.96. Overall, the only item that differed between examiners was bone marrow lesions of the sesamoids.

According to the researchers, this is the first study to develop and examine an MRI scoring system developed specifically for first metatarsophalangeal joint osteoarthritis that also includes assessment of the sesamoid complex and the direct assessment of cartilage loss. In addition, this is the first scoring system that “presents pictorial representations for each MRI feature.”

Limitations of the study included logistical constraints surrounding the use of an MRI machine with a 1.5 Tesla magnet; further studies must determine the reproducibility of the atlas when images are created with a higher-end MRI machine. Additionally, synovitis was not included as an independent item due to the lack of use of a contrast agent, and MRI procedures were not conducted with participants in a weight-bearing position.

“The development of a reproducible atlas…will allow for the quantification of the presence and severity of pathological change occurring in joint tissues in [first metatarsophalangeal joint osteoarthritis],” the researchers of the study concluded. “This has the potential to allow for a better understanding of the causes of pain…which may facilitate the development of more effective interventions for this condition.”

Reference

Munteanu SE, Pod B, Auhl M, et al. Development and reproducibility of a first metatarsophalangeal joint osteoarthritis magnetic resonance imaging scoring system [published online June 24, 2019]. Arthritis Care Res. doi:10.1002/acr.24016