Summary
Objectives
To compare the in vitro biomechanical effects of single loop cerclage wires, an intramedullary pin and the
combination thereof as applied to an oblique mid-diaphyseal osteotomy of canine tibiae.
Methods
Three groups of nine bones with long oblique osteotomies were repaired with the following
methods: 1) Three single loop cerclage wires and a transcortical skewer pin, 2) intramedullary
pinning with a smooth Steinmann pin, and 3) a combination of both methods. The repaired
constructs were tested in a single cycle four-point-bending test to failure. Load
displacement curves were drawn and the following parameters were calculated or extrapolated:
Stiffness, load at yield, and force resisted at 2 mm actuator displacement. The latter
was determined to demonstrate the difference in the amount of energy absorbed between
the different groups.
Results
The stiffness and force resisted at 2 mm displacement of the groups with cerclage
wires were significantly higher than the group with an intramedullary pin alone (p
≤ 0.05). The differences in stiffness (p = 0.15) and force required at 2 mm displacement
(p = 0.56) between cerclage wires and the combination of cerclage wires and intramedullary
pins were not significant.
Clinical relevance
Cerclage wire repair results in higher stiffness than repair with an intramedullary
pin. When cerclage wires are combined with an intramedullary pin, the intramedullary
pin does not provide protection to the cerclage wire repair and the wires or the bone
under the wires has to fail before the pin resists significant load.
Keywords Cerclage wires - intramedullary pin - oblique tibia osteotomy - biomechanics
