OTA 2006 Posters
Scientific Poster #93 Basic Science
Biomechanical Investigation of Locked versus Nonlocked Diaphyseal Fixation
of Plate Screw Constructs in a Nonosteoporotic Human Cadaveric Distal Femoral
Fracture Model
William M. Ricci, MD1; Yanming Zheng3;
Zakiyyah Walker3;
Mary Anthony3; Jeff Holbrook3; Paul Tornetta III,
MD2;
(all authors - a,e-Smith + Nephew)
1Washington University School of Medicine, St. Louis, Missouri,
USA;
2Boston University, Boston, Massachusetts, USA
3Smith & Nephew, Memphis, Tennessee, USA
Purpose: The mechanical properties and benefit of locked plate
devices in nonosteoporotic bone remain unknown. The purpose of this study
was to directly compare locked and nonlocked plate-screw fixation in nonosteoporotic
diaphyseal bone.
Methods: Five matched pairs of nonosteoporotic (bone mineral
density 0.864-1.194 g/cm2) human cadaveric femurs were instrumented
using a locked distal femur plate for an extra-articular metaphyseal fracture
with a 3-cm gap (OTA 33A3). The left and right femurs of each pair were
randomly assigned into two groups based on the diaphyseal fixation method:
LOCKED with four 4.5-mm locked screws or NONLOCKED with 4.5-mm nonlocked
screws in the closest and farthest holes from the fracture (Figure 1).
Figure 1
Distal fixation in both groups was with five 5.7-mm locking screws. All
specimens were subjected to a cyclic axial compressive load of 500 N with
a physiologic varus moment at 2 Hz for 500,000 cycles. Construct stiffness
was evaluated every 50,000 cycles. Load to failure was measured after 500,000
cycles.
Results: NONLOCKED constructs showed either similar or higher
average stiffness values at each of the 50,000 cycle intervals when compared
to the LOCKED constructs (Figure 2).
Figure 2
The average load to failure for the NONLOCKED group (303 lbf) was 11%
greater than for the LOCKED group (273 lbf), but this was not significant
(P = 0.12). The mode of failure observed was plate deformation
in all specimens; no diaphyseal screw failures occurred in either group.
Conclusions:
Nonlocked screw fixation exhibited equivalent or better mechanical properties
compared with locked screws for fixation in nonosteoporotic human diaphyseal
bone under cyclic loading conditions. These findings indicate that the use
of nonlocked diaphyseal screws may be advantageous in nonosteoporotic bone,
either alone or to augment locked fixation.
If noted, the author indicates something of value received.
The codes are identified as a-research or institutional support; b-miscellaneous
funding; c-royalties; d-stock options; e-consultant or employee; n-no conflicts
disclosed, and *disclosure not available at time of printing.
·
The FDA has not cleared this drug and/or medical device for the use
described in this presentation (i.e., the drug or medical device is being
discussed for an "off label" use). · · FDA
information not available at time of printing.
