GROWTH-PLATE MODIFICATIONS AFTER DRILLING

Thirty 5-week-old male rats were used to discern the local modificatio ns of the growth plate after drilling. A 1-mm wide drill hole was made on the right femur from the intercondylar notch to the diaphysis cros sing the growth plate, with the left femur acting as a sham-operated c ontrol. Animals were killed in four five-unit groups at 1, 2, 8, and 1 6 weeks, respectively, after the surgical procedure. Soft tissues were removed and bone length measured. Distal growth plates of both femora were histologically, histomorphometrically, and histochemically studi ed. There were no significant differences in length or growth-plate he ight between drilled bones and their controls. Drill holes were filled by bony trabeculi formed progressively from metaphyses and adjacent c artilage metaplasia. This bone bridge grew wider as time passed after the surgical procedure. These experimental findings suggest that cauti on should be taken when pinning fractures through the growth plate. Fa iled attempts can produce permanent epiphysiodesis bridges.