Conversion of External Fixation to Definitive Intramedullary Nailing in Experimental Tibial Fractures

ABSTRACT

Background and Purpose: Initial treatment with external fixation of tibial fractures is indicated in severely injuried multitrauma patients. A conversion procedure to secondary nailing is often performed later to enhance fracture repair. The aim of the study was to compare definitive treatment of experimental tibial fractures with external fixation to an early conversion to secondary intramedullary nailing with large and small diameter nails. Methods: Thirty male rats were subject to a standardized tibial shaft osteotomy initially stabilized with external fixation. On day 7, they were assigned to either the control group (group A, N = 10) or conversion to secondary nailing with a small (group B, N = 10) or large diameter nails (group C, N = 10). Evaluation at 60 days included radiography, dual energy radiographic absorptiometry (DXA), and mechanical bending testing. Results: All fractures healed radiographically with bridging of the fracture line and more or less visible periosteal callus formation. Group B demonstrated significantly increased mineralization and callus formation measured as DXA parameters, bone mineral content (BMC), and callus area (CA) compared to both the other two groups. This group also tended to have mechanically stronger bones with higher fracture energy compared to both the other two groups, but no significant difference in mechanical prioperties between the groups was found in our study. Interpretation: In conclusion, we found that conversion from external fixation of leg fractures in rats to intramedullary nailing did not improve bone healing significantly supporting external fixation as definitive fracture management.

Keywords: :

• initial external fixation
• secondary intramedullary nailing
• experimental rat model
• tibial diaphyseal fracture
• mechanical testing
• callus mineralization
• dual-energy X-ray absorptiometry

ACKNOWLEDGMENTS

Financial support for this study was provided by the University of Oslo, Faculty Division Akershus University Hospital and Institute of Surgical Research, Rikshospitalet University Hospital, Oslo. The authors whish to thank: Knut Rekdahl and the Engineering Workshop at University of Oslo for skilled mechanical craftsmanship; engineer Per Ludvigsen at Rikshospitalet University Hospital and researcher Lise Sofie Nissen-Meyer and engineer Hong Qu at University of Oslo for technical assistance in mechanical testing, measuring of DXA values, and microcomputer tomography imaging; radiographers Camilla Stolp and Helge Grindbakken at Rikshospitalet University Hospital for assistance in obtaining radiographs, and Department of Comparative Medicine, Rikshospitalet Medical Center for housing our research animals.