THE SIGNIFICANCE OF ENTHESOPATHY AS A SKELETAL PHENOMENON

Enthesophytes and enthesopathy, while easy to define, represent a phen omenon of unclear clinical significance. As the high frequency in skel etal populations suggests that enthesopathy may not be disease-specifi c, the nature of the reaction was assessed in 872 individuals from a r epresentative skeletal population, subdivided into groups characterize d by the presence or absence of rheumatoid arthritis, spondyloarthropa thy, calcium pyrophosphate deposition disease and diffuse idiopathic s keletal hyperostosis (DISH). Achilles, plantar fascia, patellar and il iac crest entheses were examined for evidence of calcific overgrowth o r ''erosions.'' Enthesophytes were found to be a phenomenon of aging i n individuals, and unrelated to the presence of inflammatory arthritis or DISH. The frequency increased with age, independent of sex or the site examined, plateauing infrequency after age 60. Enthesophytes in i ndividuals under age 60 were usually unrelated to any underlying disor der. The absence of effect of underlying forms of arthritis on the fre quency of enthesophytes at the patellar, Achilles and plantar sites su ggests that mechanical factors outweigh the ''enthesis calcifying '' i mpact of such disorders as spondyloarthropathy, calcium pyrophosphate deposition disease and DISH. Individuals with rheumatoid arthritis, ho wever, manifested a less severe iliac crest enthesial reaction, in kee ping with the minimal reactive new bone formation characteristic of it s erosions.Analysis of Achilles, plantar, and patellar enthesial react ions as a function of underlying inflammatory arthritis or DISH also r evealed no significant variation with the underlying process. Cortical discontinuity at enthesial sites was a relatively infrequent phenomen on. While calcaneal discontinuities were originally thought to be eros ive in nature, these observations suggest the possibility of tendon av ulsion injuries.