Rickets

In rickets, defective bone growth results from retardation or suppression of normal epiphyseal cartilage growth and calcification. These changes result from a deficiency of calcium and phosphorus salts in the serum. Cartilage cells fail to complete their normal cycle of proliferation and degeneration, with subsequent failure of capillary penetration, which occurs in a patchy manner. The result is a frayed, irregular epiphyseal line at the end of the shaft. Failure of osseous and cartilaginous matrix to mineralize in the zone of preparatory calcification, followed by deposition of newly formed uncalcified osteoid, results in a wide, irregular, frayed zone of nonrigid tissue (the rachitic metaphysis.