An experimental model of hidden high-energy femoral fractures with disrupted callus formation

Abstract

Objective To explore ways to prevent lack of callus formation by establishing an experimental model of hidden high-energy femoral fractures with disrupted callus formation.Methods Twenty adult dogs were randomly divided into 2 equal groups to create models of closed transverse or short oblique fracture at the left hind legs after anaesthetized.The periosteum and muscles surrounding the fracture ends were stabbed by the ends longitudinally 10 times till the ends overlapped 1.5 cm.Group A was subjected to immediate open reduction and internal fixation with an 8-hole plate while group B to manual reduction and temporary fixation with a fine percutaneous Kirschner wire to stabilize the bone ends through the greater trochanter for 10 days followed by delayed open reduction and internal fixation with an 8-hole plate.At 2,4,6,8 and 12 weeks post-treatment,2 dogs in each group were sacrificed to harvest fracture specimens to observe callus growth by gross and histological examinations.Results In group A,a necrotic exudate cavity appeared around the fracture at 2 weeks,the exudate cavity narrowed and whitish bone ends were covered by no tissue at 4 weeks,the exudate disappeared and the bone ends were absorbed at 6 weeks,and no internal or external callus growth was observed at 8 to 12 weeks and the bone ends were further absorbed,indicating an experimental model of lack of femoral callus formation was successfully created.In group B,lateral callus sprouting was observed at 2 weeks,direct callus sprouting began at 4 weeks,callus formation at both ends was observed to meet each other at 6 weeks,and the callus growth bridged the fracture gap at 8 to 12 weeks.X-rays showed widened fracture gaps due to absorbed bone ends in group A and steady bridging of the gaps by callus growth in group B.Conclusions The present experiment successfully established an experimental model of hidden high-energy femoral fracture with disrupted callus formation caused by early open reduction and internal fixation.Delayed surgery may prevent lack of callus formation. Key words: Femoral fractures; Bony callus; Models, animal; Delayed operation