Soft tissue mineralization: roentgen analysis.

Numerous, incompletely understood, and undetermined physiologic factors may exert further but unappreciated influences on the development of ectopic calcification and ossification. In the former instance, in addition to serum calcium and phosphorous ion concentrations, tissue pH, blood supply, hormones, i.e., vitamin D, vitamin A, and various enzymes (e.g., alkaline phosphatase and pyrophosphatase) may all play significant, ancillary, time-dependent, but as yet undetermined roles. Ossification, like calcification, may occur in association with many types of disorders and under a variety of circumstances, some of which, such as trauma, have been reduplicated in the laboratory. However, experimental conditions that produce ectopic bone, as well as the species that are predilected do not always coincide with clinical observations in man. Not only are there differences between species in regard to susceptibility to ectopic bone production under particular circumstances, i.e., rabbits are the most susceptible and mice the least to mechanical injury, but there are differences between individuals. Individual variability in susceptibility to soft tissue ossification suggests either a personal or familial predilection. If such liability is inherited, this would be an example of an ecogenetic condition, in which someone is susceptible to an environmental agent by virtue of genetic constitution. Histocompatibility (HLS) antigens have provided substantiation of this concept. In the case of soft tissue ossification, causative environmental agents could include trauma, burns, hip replacement, and immobility secondary to neurological insults. In the case of soft tissue calcification, trauma, infections, or repeated injections could constitute the triggering environmental event. Not only do individuals at risk develop bone, but those that do tend to do so in characteristic places. Therefore, there is an additional differential susceptibility at various sites in the same individual. In cases with neurological conditions, thigh muscles are more susceptible than paraspinal muscles. The underlying condition is a further moderator, i.e., in paraplegics, thigh muscles are most apt to be involved. Elbows are most commonly affected after burns regardless of the site of the burn. Ectopic ossification also has a further predilection for distribution. Not only are muscle groups unequal in risk in terms of site, but the type of muscle affected is relevant, since skeletal muscles are involved in these same conditions to the exclusion of smooth muscles.(ABSTRACT TRUNCATED AT 400 WORDS)