Purpose: The purpose of our study is to record the composition and the viability of the cells from reaming products during intramedullary nailing of tibia or femur.

Material and Methods: We studied 21 fractures (13 tibia and 8 femur). The patients had mean age 27 years {1 9–67) and they didn’t face any systemic disease. The operation was done during the first 3 days from the injury and there was pro-operative x-ray check for measuring the medullar cavity. For 16 fractures we used reamers with diameter smaller or equal to the medullar cavity and for the rest 5 for biomechanical reasons we used bigger reamer. We take the products in aseptic condition in the operating room and after the proper elaboration they were been analyzed histo logically. The patients were followed up until the complete healing of the fractures.

Results: Our first observation was that in the very small reamers, which didn’t “touch” the endosteum there were non-viable marrow cells. After that with reamers till 1mm less than the intramedullary diameter there was viable bone mass 35–70% more than the non-viable. When the reaming exceeded this border microscopic analysis showed pieces (1–1, 5mm) of bone mass with few viable elements in the center of them and more compressed dead cells in the perimeter. From the p.o. follow-up it was remarkable that the patients whose bone was reamed didn’t exceed the intramedullary diameter showed primary callus formation in x-rays after 4–5 weeks, but the others after 5–7 weeks.

Conclusions: In conclusion, although our sample is not big enough, we can say that there are sighs that the reaming products cells are more viable when the reaming does not exceed the intramedullary diameter. This fact seems to have positive influence in the callus formation procedure.