ARUP; ISBN: 978-0-9562121-5-3 - CMBBE 2012 - Cardiff University

Both types of plating produced larger strains in osteoporotic bone. The presence of a
fracture gap was seen to further increase strains around screw holes (Figs. 1 and 2). In
osteoporotic bone this increase was substantial. The use of compression plating in the
presence of a fracture gap and osteoporotic bone produced a combination of high tensile
strains on the distal side of the screw hole and high compressive strains on the proximal
side.
In a fully reduced fracture gap, the proportion of load transmitted by the LCP was
25.4% in healthy bone and 32.2% in osteoporotic bone at a load of 1891N. A similar
trend was observed in compression plating where plate preload was relieved faster in
osteoporotic bone; in this case the bone transmitted 90.4% of the applied load at 1891N
compared with 100% in healthy bone.
5. DISCUSSION
The study has shown that locking plates produced lower strains around screw hole
locations in osteoporotic bone than conventional plates. In healthy bone there was a
much smaller difference between locked plating and conventional plating.
An incomplete fracture reduction resulted in increased strain concentration and
therefore an increased likelihood of screw loosening. This effect was most pronounced
in compression plated osteoporotic bone which resulted in large regions of very high
levels of strain. In terms of strain distribution around screw holes healthy bone is
relatively unaffected by either plating system or the presence of a fracture gap.
While compressive strains may be reduced by the addition of more screws, the high
tensile strains caused by compression screw fastening will still be present regardless of
the number of screws used.
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