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Objectives. The use of two implants to manage concomitant ipsilateral femoral
shaft and proximalfemoral fractures has been indicated, but no
studies address the relationship of dynamic hip screw (DHS) side
plate screws and the intramedullary nail where failure might occur
after union. This study compares different implant configurations
in order to investigate bridging the gap between the distal DHS
and tip of the intramedullary nail. Methods. A total of 29 left synthetic femora were tested in three groups:
1) gapped short nail (GSN); 2) unicortical short nail (USN), differing
from GSN by the use of two unicortical bridging screws; and 3) bicortical
long nail (BLN), with two angled bicortical and one unicortical bridging
screws. With these findings, five matched-pairs of cadaveric femora
were tested in two groups: 1) unicortical long nail (ULN), with
a longer nail than USN and three bridging unicortical screws; and
2) BLN. Specimens were axially loaded to 22.7 kg (50 lb), and internally
rotated 90°/sec until failure. Results. For synthetic femora, a difference was detected between GSN and
BLN in energy to failure (p = 0.04) and torque at failure (p = 0.02),
but not between USN and other groups for energy to failure (vs GSN,
p = 0.71; vs BLN, p = 0.19) and torque at failure
(vs GSN, p = 0.55; vs BLN, p =
0.15). For cadaveric femora, ULN and BLN performed similarly because
of the improvement provided by the bridging screws. Conclusions. Our study shows that bicortical angled screws in the DHS side
plate are superior to no screws at all in this model and loading
scenario, and suggests that adding unicortical screws to a gapped
construct is probably beneficial