Long-term inflammation can have the effect of removing calcium from the bones, weakening and shrinking them. According to one web site, "Inflammation-mediated bone loss is a problem of major clinical and economic significance; it occurs in various diseases such as periodontal disease, osteo- and rheumatoid arthritis and some forms of osteoporosis."
In dentistry it is recognised that bone loss caused by gum inflammation can eventually lead to teeth falling out. Also inflammation and the resulting loss of bone can cause dental implants to fall out.
Years of inflammation around the coccyx can have the same effect. Several people who have had their coccyxes removed have been told by their surgeons that the coccyx crumbled when they removed it.
My coccyx didn't crumble when my surgeon was removing it, but I have two reasons for believing that it was very weak:
Another cause of loss of bone strength that could be of interest to coccydynia sufferers is the use of corticosteroids. It is known that these drugs can cause loss of bone in sufferers from inflammatory bowel disease (IBD), who have to take these drugs daily. I don't know whether the injections of corticosteroids given to relieve coccyx pain could also cause bone loss. Possibly these drugs will not have any serious effect on the coccyx because they are usually given no more frequently than once every three months.
One site about inflammatory bowel disease says: "In IBD patients who require corticosteroids, the effects on bone mineral density are seen within the first three to six months... Alternate day dosing does not protect bone. . . Gastroenterologists should determine baseline bone mineral density in all IBD patients and give them calcium and vitamin D," said Dr. Cohen. Weight-bearing exercise, and eliminating smoking and excessive alcohol are important to preventing bone loss as well. Dr. Cohen reviewed the medical options for preventing and treating osteoporosis. These include: hormone replacement therapy; calcitonin, which is now available in a nasal spray; and biphosphonates--compounds that inhibit bone loss, such as alendronate. "It's clear from randomized clinical trials that biphosphonates are effective. Compliance is poor, however. You have to take these drugs with a full glass of water, sitting up, and they have been shown to cause esophageal irritation and ulcers."