ObjectivesWe aimed to further evaluate the biomechanical characteristics
of two locking screws versus three standard bicortical
screws in synthetic models of normal and osteoporotic bone.MethodsSynthetic tubular bone models representing normal bone density
and osteoporotic bone density were used. Artificial fracture gaps
of 1 cm were created in each specimen before fixation with one of
two constructs: 1) two locking screws using a five-hole locking
compression plate (LCP) plate; or 2) three non-locking screws with
a seven-hole LCP plate across each side of the fracture gap. The
stiffness, maximum displacement, mode of failure and number of cycles
to failure were recorded under progressive cyclic torsional and
eccentric axial loading.ResultsLocking plates in normal bone survived 10% fewer cycles to failure
during cyclic axial loading, but there was no significant difference
in maximum displacement or failure load. Locking plates in osteoporotic
bone showed less displacement (p = 0.02), but no significant difference
in number of cycles to failure or failure load during cyclic axial loading
(p = 0.46 and p = 0.25, respectively). Locking plates in normal
bone had lower stiffness and torque during torsion testing (both
p = 0.03), but there was no significant difference in rotation (angular
displacement) (p = 0.84). Locking plates in osteoporotic bone showed
lower torque and rotation (p = 0.008), but there was no significant difference
in stiffness during torsion testing (p = 0.69).ConclusionsThe mechanical performance of locking plate constructs, using
only two screws, is comparable to three non-locking screw constructs
in osteoporotic bone. Normal bone loaded with either an axial or
torsional moment showed slightly better performance with the non-locking
construct.
The combination of skeletal and chest injuries does not seem to amplify the pulmonary morbidity and mortality compared with chest injury alone. The quantity of the skeletal injury and the time to fixation of structures affecting mobilization seem to have an effect on pulmonary morbidity and mortality. Better scientific studies on the effects of skeletal injury and timing to fixation in relation to pulmonary morbidity and mortality are required.
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