Unreamed nailing with solid tibial nails is an accepted method of treatment
for open tibial shaft fractures up to grade III and of closed tibial fract
ures with severe soft tissue damage. However, fatigue failure of the distal
locking bolts is a frequent complication. We report a mechanical study inv
estigating the fatigue limit of six different types of locking bolts used i
n solid tibial nails (Biorigid Tibial nail/aap, UTN/ace, STN/Howmedica, TLN
/ Howmedica, Delta R & T Tibial nail/Smith & Nephew, AO/ASIF UTN/Synthes).
Our results prove a direct correlation between the bolt's diameter and mech
anical properties. Further more we found that bolts with a continuing threa
d were weaker than bolts of the same diameter with only a short thread and
an increased diameter at the nail's aperture. Our results suggest that mobi
lization with half of the average body weight (350N) allows osseous consoli
dation without fatigue failure of any of the tested locking bolts. Some of
the tested locking bolts may even withstand full weight-bearing in a physio
logical walking cycle, but will not withstand the stress of a running cycle
.