Page 70 - Imaging of Osteoarthritis and Rheumatoid Arthritis in Hand Joints
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                                Chapter 4
subluxated when 33% or more of the metacarpal surface area was not aligned with the trapezial surface area in the coronal or sagittal plane. Synovitis was not scored as we did not use a contrast agent.
Tissue preparation
During surgery the trapezium bone was extracted as a whole or in multiple parts. If the trapezium was not extracted in one piece, care was taken that the articular area of the trapezium facing the 1st metacarpal bone was kept intact by splitting the trapezium horizontally leaving at least 5 mm of the distal trapezium intact. The resected trapezium was fixed in neutral buffered 10% formalin in the operating room. Trapezium bones were decalcified in formic acid. Large decalcified specimens were cut in half, and all samples were embedded in paraffin. Each millimeter, a five μm thick sections was cut in the sagittal direction of the bone, mounted and stained with thionin.16
All histological sections were scored for cartilage damage by a trained researcher (MS). To determine the reproducibility of these scores, 10 patients were also scored by GvO, an experienced cartilage researcher. The scorers were blinded to the results of the MRI evaluation. All available sections were scored for severity and extent of cartilage damage. Severity of cartilage damage was scored according to the semi-quantitative grading and staging system devised by the Osteoarthritis Research Society International (OARSI) working group.17 Grade, defined by depth of cartilage damage, and stage, defined by the horizontal extent of cartilage damage were assessed. The OARSI grading system consists of six grades that describe increasing depth of cartilage damage. Grades 1-4 are subsequently described as: grade 1, edema or cell changes with an intact surface; grade 2, small surface discontinuities; grade 3, vertical fissures; and grade 4, delamination of the superficial zone. For comparison with MRI we defined grades 1-4 together as “cartilage with (near) normal thickness”. Grade 4.5 is described as mid-zone excavation, and was defined by us as “partial thickness loss of cartilage” for comparison with MRI. Grades 5 and 6 are described as: grade 5, complete erosion of hyaline cartilage to the level of mineralized bone; and grade 6, deformation and change in the contour of the articular surface. For comparison with MRI we defined grades 5 and 6 together as “full-thickness cartilage loss” (see Fig. 1 for examples).

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