Simple bone cyst. Treatment by trepanation and studies on bone resorptive factors in cyst fluid with a theory of its pathogenesis.

Simple bone cysts were treated by trepanation. The technique consists of drainage of cyst fluid, lavage of the cystic cavity with saline, and the making of multiple drilling holes through the cortical and the medullary bone of the cyst wall. Injection of corticosteroid was omitted. In 11 cases treated by this method, the clinical outcome was good. Biochemical analyses of the cyst fluid showed bone-resorptive factors, i.e., prostaglandins, interleukin 1, proteolytic enzymes. Electrophoretic analysis of proteolytic enzymes in polyacrylamide gel containing sodium dodecyl sulfate and polymerized gelatin showed proteins with molecular weights of about 130,000, 92,000, 72,000, and lower than 50,000. Increase in such bone-resorbing activities seems to be one of the causative factors in simple bone cysts. The technique was effective in decompressing the internal pressure of the cysts, improving the blood flow through the medullary bone of the cyst wall, stimulating the periosteum to induce bone formation, and eliminating bone destruction.