Page 66 - Imaging of Osteoarthritis and Rheumatoid Arthritis in Hand Joints
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                                Chapter 4
Background Magnetic resonance imaging (MRI) is increasingly used for research in hand osteoarthritis, but imaging the thin cartilage layers in the hand joints remains challenging. We therefore assessed the accuracy of MRI in detecting cartilage loss in patients with symptomatic osteoarthritis of the first carpometacarpal (CMC1) joint.
Methods Twelve patients scheduled for trapeziectomy to treat severe symptomatic osteoarthritis of the CMC1 joint underwent a preoperative high resolution 3D spoiled gradient (SPGR) MRI scan. Subsequently, the resected trapezium was evaluated histologically. The sections were scored for cartilage damage severity (Osteoarthritis Research Society International OARSI score), and extent of damage (percentage of surface area). Each MRI scan was scored for the area of normal cartilage, partial cartilage loss and full cartilage loss. The percentages of the total surface area with any cartilage loss and full-thickness cartilage loss were calculated for both MRI and histology.
Results MRI and histology both identified large areas of overall cartilage loss. The median (IQR) surface area of any cartilage loss on MRI was 98% (82%-100%), and on histological assessment 96% (87%-98%). However, MRI underestimated the extent of full-thickness cartilage loss. The median (IQR) surface area of full- thickness cartilage loss on MRI was 43% (22%-70%), and on histology 79% (67%-85%). The difference was caused by a thin layer of high signal on the articulating surface which was interpreted as damaged cartilage on MRI but which was not identified on histology.
Conclusions 3D SPGR MRI of the CMC1 joint visualizes overall cartilage damage, but underestimates full-thickness cartilage loss in patients with advanced osteoarthritis.

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