[Biomechanical evaluation of TiNi shape-memory sawtooth-arm embracing plate and its effect on fracture healing].
OBJECTIVE
To investigate the detailed biomechanics of TiNi shape-memory sawtooth-arm embracing plate (TiNi SMA) by comparing with limited-contact dynamic compression plate (LC-DCP) and static interlocking intramedullary nail (SIiN), so as to provide theoretical evidence for clinical application.


METHODS
Eight paired cadaveric femurs immersed in formaldehyde were harvested from eight specimens of adults. After making X-ray films and modeling midpiece transverse fracture, one side randomly was fixed by TiNi SMA (group A) and SIiN (group C) orderly, the other side was fixed by LC-DCP (group B). The axial compression, three-point bending (pressed from plate side and opposite side both of group A and group B, from inside of group C), and torsion were tested, and the stress shielding rate was compared.


RESULTS
At every classified axial compression load, the strains of group A were greater than those of group B and group C (P < 0.05), the displacements of group A were greater than those of group B and group C (P < 0.05) except 100 N. At every classified three-point bending moment, the displacement of group A were greater than those of group B and group C pressed both from two sides, but there was no difference when pressing from two sides under the same load of group A (P > 0.05). At every torsion moment, the torsion angels of group A were greater than those of group B (P < 0.05), but equal to those of group C (P > 0.05). At 600 N of axial compression load, the stress shielding rates of groups A, B, C were 48.30% +/- 22.99%, 89.21% +/- 8.97%, 95.00% +/- 3.15%, respectively, group A was significantly less than group B and group C (P < 0.01).


CONCLUSIONS
The anti-bending ability of TiNi SMA is weaker than LC-DCP and SIiN; the anti-torsion ability of TiNi SMA is weaker than SIiN, but TiNi SMA is a center-type internal fixation, the superior stress shielding rate and micromovement promote the stress stimulation of fracture, which makes it an ideal internal fixation device.
Yan
Xuegang
X
The First College of Clinical Medical Science, Three Gorges University, Yichang Hubei, 443003, P.R. China.
Bao
Tongzhu
T
Zhao
Weidong
W
Yan
Fei
F
Liang
Dongzhu
D
Ding
Zhibing
Z
D000328:Adult; D001696:Biomechanical Phenomena; D001860:Bone Plates; D005264:Femoral Fractures / Q000601:surgery*; D005593:Fracture Fixation, Internal / Q000295:instrumentation*; D017102:Fracture Healing; D006801:Humans