Effects of static fixation and dynamization after interlocking femoral nailing locked with an external fixator: an experimental study in dogs.
OBJECTIVE
To determine bone healing at 20 weeks, after either static fixation (SG) or after dynamization (DG) at 4 weeks in osteotomized canine femurs repaired with an interlocking nail (ILN) secured with a type I external skeletal fixator (ESF).


METHODS
Experimental study.


METHODS
Ten adult beagle dogs.


METHODS
After mid-diaphyseal femoral osteotomy, femurs in 10 dogs were repaired with an ILN secured with 4 (2 proximal, 2 distal) threaded custom pins (TP; 2.7-mm-diameter cortical screw with a 2-mm shaft attached to the screw head) to which 2 parallel connecting bars were attached in a type I ESF configuration. In 5 dogs, dynamization was performed at 4 weeks by removing the connecting bars and 2 distal screws. Limb function, range of motion of the stifle joint (ROMSJ), radiographic evidence of bone healing, and complications were studied for 20 weeks.


RESULTS
Full limb function was achieved between 8 and 10 weeks in SG dogs, but a decreased ROMSJ was observed from 5 to 8 weeks. In DG dogs, full limb function occurred between 5 and 6 weeks except in 1 dog, and ROMSJ was considered normal in all dogs. Bone healing was not affected by dynamization. Average healing time for SG was 12.8 weeks, and for DG it was 13.6 weeks. Periosteal reaction at TP insertion points, osteolysis around the thread and head of TPs were observed in both groups. A windshield-wiper effect was observed at the tip of 1 ILN.


CONCLUSIONS
ILN locked with a type I ESF can be used for fixation of mid-shaft femoral fractures. Dynamization at 4 weeks did not affect bone healing but did prevent stifle ankylosis and promoted earlier limb function.


CONCLUSIONS
ILN locked with a type I ESF is seemingly a feasible method for repair of mid-shaft femoral fractures and may decrease risk of nail failure.
Durall
Ignacio
I
Departamento de Medicina y Cirugía Animal, Facultad de Veterinaria, Universidad Autónoma de Barcelona, Barcelona, Spain. Ignacio.Durall@uab.es
Falcón
Carmelo
C
Díaz-Bertrana
M Carmen
MC
Franch
Jorge
J
D000818:Animals; D001858:Bone Nails / Q000662:veterinary*; D004285:Dogs / Q000293:injuries* / Q000601:surgery*; D016267:External Fixators / Q000662:veterinary*; D005264:Femoral Fractures / Q000000981:diagnostic imaging / Q000601:surgery / Q000662:veterinary*; D005594:Fracture Fixation, Intramedullary / Q000379:methods / Q000662:veterinary*; D017102:Fracture Healing; D008297:Male; D011859:Radiography; D016059:Range of Motion, Articular