Callus formation in teamed and unreamed femoral nailing: an experimental study

This was a prospective randomized baboon animal study,the study protocol wa s approved by the ethical committee according to the international guidelin es for animal research projects. In 8 animals a midschaft femoral osteotomy was stabilized with reamed femoral interlocking nailing and in 8 animals b y unreamed locked femoral nailing. Polychrome sequence bone labeling was do ne 5 weeks postop. with calcein-green, 8 weeks postop. with xylenol-orange and 10 weeks postop. with oxytetracycline. 10 weeks postop. the animals wer e sacrificed, the femurs explanted and planimetric and epifluorescence hist omorphometric evaluation of serial transverse sections were done. In planimetric histomorphometric evaluation in unreamed femoral nailing a m ean endostal callus formation was recorded with 28.0+/-9.9 mm(2) per sectio n and in reamed femoral nailing with 11.5+/-5.0 mm(2) (p<0.001). Periostal callus formation was recorded in the unreamed group with 238.7+/-87.1 mm(2) per section and in the reamed group with 142.1+/-71.9 mm(2) (p<0.001). In epifluorescence histological evaluation endostal as well as periostal callu s formation was more extensive and earlier after unreamed than reamed femor al nailing. Endostal callus formation was found in all animals after unream ed femoral nailing, and was present in 2 out of 8 specimen in the reamed gr oup. Also 1 out of 8 animals in the reamed group developed a non-union. Unreamed femoral nailing with low diameter interlocking nails proved to be safe regarding bone healing in this experimental model with obvious advanta ges both in amount and time course of callus formation compared to reamed f emoral nailing. Based on this results unreamed femoral nailing techniques c an be recommended for femoral fractures.