Pulmonary fat embolism after reamed and unreamed nailing of femoral fractures.

Abstract

To determine whether reamed or unreamed intramedullary nailing of femoral fractures results in higher incidence of pulmonary fat embolism, three different methods of intramedullary nailing were compared in sheep. To analyze the presence of bone marrow fat embolism in pulmonary arteries, histological evaluation was undertaken using a quantitative computer-assisted measurement system. In this experimental model of 27 female Swiss alpine sheep, an osteotomy of the proximal femur was conducted in each animal. Then, the animals were divided into three groups according to the method of treatment: two different reamed intramedullary nailing techniques and an unreamed nailing technique were used. In the first group "ER" (experimental reamer; n=9), the nail was inserted after reaming with an experimental reamer; in the second group "CR" (conventional reamer; n=7), the intramedullary nail was inserted after reaming with the conventional AO-reamer. In the third group "UN" (unreamed; n=8) unreamed nailing was performed. During the operation procedure intramedullary pressure was measured in the distal fragment. After sacrificing the animals, quantitative histological analyses of bone marrow fat embolism in pulmonary arteries were done using osmium tetroxide fixation and staining of the fat. The measurement of intramedullary pressure showed significantly lower values for reamed nailing than for the unreamed technique. The quantitative histological evaluation of lung vessels concerning bone marrow fat embolism revealed a statistically significant difference between reamed and unreamed insertion of the nail: 7.77%±6.93 (ER) and 6.66%±5.61 (CR) vs. 16.25%±10.05 (UN) (p<0.05) of the assessed lung vessels were filled with fat emboli. However, no difference was found between the traditional and experimental reamer. Intramedullary nailing after reaming is a safe procedure with low systemic embolisation when compared to the unreamed insertion of the nail.