An unusual osteochondral body in association with calcium pyrophosphate dihydrate crystal deposition disease.

Abstract

Chronic pyrophosphate arthropathy is a recognized subset of osteoarthritis (OA) characterized by deposition of calcium pyrophosphate dihydrate (CPPD) crystals (McCarty, 1976). Typically a disease of the elderly, there is symptomatic and radiographic involvement of characteristic sites, including the patellofemoral, radiocarpal and glenohumeral joints (McCarty & Haskin, 1963; Resnick & Resnick, 1983). CPPD deposition in cartilage (chondrocalcinosis) occurs particularly in the articular and the meniscal cartilages of the knee, the symphysis pubis and the triangular ligament of the wrist (McCarty & Haskin, 1963; Resnick & Resnick, 1983). It has been postulated that sporadic pyrophosphate arthropathy may represent a hypertrophic response to joint insult (Doherty et al, 1984), with CPPD crystal formation being a marker of high extra-cellular pyrophosphate production reflecting increased cellular biosynthetic activity (Caswell et al, 1983). Osteochondral bodies, arising in synovium by enchondral ossification of islands of chondroid metaplasia, are a common accompaniment to OA and may be particularly florid in the subset of pyrophosphate arthropathy (McCarty & Haskin, 1963; Resnick & Resnick, 1983). Such bodies form by a process of layered growth (Milgram, 1977b), and possibly reflect a generalized hyperplastic response (i.e. attempted repair) by joint tissues. We present a patient with CPPD arthropathy who developed an osteochondral body that showed features both of ossification and chondrocalcinosis.