Pattern of advancement in the zone of calcified cartilage detected in hand osteoarthritis.

Objective: Using high definition macroradiography the pattern of advancement in the zone of calcified cartilage (termed a ZCC step) was detected in osteoarthritic hand joints of patients and compared to the joint space width (JSW) measurement.

Design: X5 macroradiographs were obtained of the osteoarthritic hands of 44 patients at baseline and at 18 months. The incidence of ZCC steps, identified as an advancement in the mineralized cartilage front into articular cartilage, was assessed at each articular surface. JSW was measured and was used to determine the difference in JSW between hands and groups of joints with and without ZCC steps at both X-ray visits.

Results: ZCC steps were found at the convex articular surfaces in only 42 (48%) hand joints in 28 (64%) patients. Here, ZCC steps were present in 36 joints in the non-dominant hand, compared with 30 joints in the dominant hand. In the former, they were present in 22 DIP, six PIP and eight MCP joints and in 12 DIP, eight PIP and 10 MCP joints in the dominant hand. By 18 months, new ZCC steps had formed in 15 hands with and 17 hands without previous ZCC steps. At both X-ray visits no statistically significant difference in JSW was found between the hands and joint groups with and without ZCC steps.

Conclusion: In patients with ZCC steps, the pattern of distribution in the hand appeared to be related to that due to vascular changes, such as hyperlipidaemia, rather than to that associated with mechanical forces.