CALCIUM PYROPHOSPHATE DIHYDRATE CRYSTAL DEPOSITION DISEASE AND PSEUDOGOUT OF THE ACROMIOCLAVICULAR JOINT - RADIOGRAPHIC AND PATHOLOGICAL FEATURES

Objective. To correlate the radiographic and pathologic findings in ca lcium pyrophosphate dihydrate (CPPD) crystal deposition disease and th e pseudogout syndrome in the acromioclavicular (AC) joint, a relativel y infrequent, but clinically important site. Methods. We describe a ca se with a definite diagnosis of CPPD crystal deposition leading to pse udogout of the AC joint. We also identified 17 other patients with CPP D crystal deposition disease who showed intraarticular or periarticula r calcification in this joint and investigated the radiographic findin gs in 26 AC joints in these 17 patients. We then correlated the result s with the pathologic findings in 2 cadavers with AC joint manifestati ons of the disease. Results. Intradiscal calcification, mainly linear or punctate in configuration, was found between adjacent bony margins in 9 of 26 AC joints (35%) or between the bony margins and extending a bove the upper articular bony margin in 14 AC joints (54%). Two joints (8%) showed diffuse calcification within the discs between, above, an d below the articular bony margins. The remaining joint (3%) had intra discal calcification only above the upper bony margins of the AC joint . All the joints with calcifications above the articular margins had a ssociated globular or tumor-like soft tissue masses. A pseudogout atta ck at the AC joint may have nonspecific shoulder pain as its presentin g symptom. Conclusion. CPPD crystal deposition disease leading to pseu dogout syndrome of the AC joint is a clinically significant condition. We emphasize that careful assessment of the AC joint and adjacent sof t tissue using intensive bright light on routine shoulder radiographs may increase the sensitivity of detecting discal and capsular calcific ations in patients with pseudogout of the shoulder.