Objective. To determine the clinical, radiologic, and histologic featu
res of calcific tendinitis with cortical bone erosion. Methods. The re
cords of 6 patients with paradiaphyseal calcific tendinitis and adjace
nt bone cortex erosion were reviewed. Results. Calcific tendinitis inv
olved the linea aspera in 4 patients, the bicipital groove in 1 patien
t, and the deltoid insertion in another, Calcium deposits were associa
ted with cortical bone erosions, revealed on plain radiographs in 4 pa
tients and computed tomography scans in 2. Bone scans were performed i
n 2 patients and showed local hyperfixation of the isotope. In 4 patie
nts, suspicion of a neoplasm led to a biopsy. Calcium deposits appeare
d to be surrounded by a foreign body reaction with numerous giant cell
s. Apatite crystals were identified by transmission electron microscop
y and elemental analysis in 1 surgical sample. Conclusion. Paradiaphys
eal calcific tendinitis with cortical bone erosion is an uncommon pres
entation of apatite deposition disease.