A new method of bone fracture fixation has been developed in which fixation darts (small diameter nails/pins) are driven across a fracture site at high velocity with a pneumatically powered gun. When fixation darts are inserted oblique to one another, kinematic constraints prevent fragment motion and allow bone healing to progress. The primary aim of this study is to determine if fixation darts can provide reasonable fixation stability compared to bone screws, which were used as a benchmark since they represent a simple, yet well-established, surgical technique. The first objective was to evaluate macro-level stability using different numbers of darts inserted parallel and oblique to each other; experimental comparisons were undertaken in a bone analog model. Experimental results showed fixation darts could not be substituted for screws on a one-to-one basis, but that a plurality of fixation darts provided comparable fixation to two bone screws while allowing for faster insertion and damaging less bone. A second objective was to evaluate micro-level stability; a finite element model was created in order to provide a detailed look at the stress state surrounding the fixation darts and the evolution of the fracture gap. Even with relatively weak fixation dart configurations, the fracture gap was maintained below physiological thresholds for bone healing. Most failures of the fixed fractures were attributed to fixation dart pullout from the cancellous structure. The final objective of the study was to characterize this mode of failure with separate fixation dart and screw pullout tests conducted in Sawbones® cancellous foam and fresh porcine cancellous bone. The results showed that the cancellous foam was an acceptable substitute for real bone and provided a conservative estimate of the fixation darts' performance relative to bone screws. A final comparison between experimental and numerically predicted pullout strengths provided confirmation that the model and experiments were consistent.

References

References
1.
Bartel
,
A.
,
Davey
,
D.
, and
Keaveny
,
T.
,
2006
,
Orthopedic Biomechanics: Mechanics and Design in Musculoskeletal Systems
,
Pearson Prentice-Hall
,
Upper Saddle River, NJ
, Chap. 8.
2.
Miller
,
D. L.
, and
Goswami
,
T.
,
2007
, “
A Review of Locking Compression Plate Biomechanics and Their Advantages as Internal Fixators in Fracture Healing
,”
Clin. Biomech.
(Bristol, Avon),
22
, pp.
1049
1062
.10.1016/j.clinbiomech.2007.08.004
3.
Claes
,
L.
,
Augat
,
P.
,
Suger
,
G.
, and
Wilke
,
H.-J.
,
1997
, “
Influence of Size and Stability of the Osteotomy Gap on the Success of Fracture Healing
,”
J. Orthop. Res.
,
15
, pp.
577
584
.10.1002/jor.1100150414
4.
Duda
,
G. N.
,
Kirchner
,
H.
,
Wilke
,
H.-J.
, and
Claes
,
L.
,
1998
, “
A Method to Determine the 3-D Stiffness of Fracture Fixation Devices and its APPLICATION to Predict Inter-Fragmentary Movement
,”
J. Biomech.
,
31
, pp.
247
252
.10.1016/S0021-9290(97)00115-2
5.
Claes
,
L. E.
, and
Heigele
,
C. A.
,
1999
, “
Magnitudes of Local Stress and Strain Along Bony Surfaces Predict the Course and Type of Fracture Healing
,”
J. Biomech.
,
32
, pp.
255
266
.10.1016/S0021-9290(98)00153-5
6.
Ezquerro
,
F.
,
Jiminez
,
S.
,
Perez
,
A.
,
Prado
,
M.
,
de Diego
,
G.
, and
Simon
,
A.
,
2007
, “
The Influence of Wire Positioning Upon the Initial Stability of Scaphoid Fractures Fixed Using Kirschner Wires: A Finite Element Study
,”
Med. Eng. Phys.
,
29
, pp.
652
660
.10.1016/j.medengphy.2006.08.005
7.
Gefen
,
A.
,
2002
, “
Optimizing the Biomechanical Compatibility of Orthopaedic Screws for Bone Fracture Fixation
,”
Med. Eng. Phys.
,
24
, pp.
337
347
.10.1016/S1350-4533(02)00027-9
8.
Farley
,
G. L.
,
2006
, “
Repairing Fractured Bones by Use of Bioabsorbable Composites
,” National Aeronautics and Space Administration, Langley Research Center, Hampton, VA, NASA Technical Brief No. LAR-16354-1.
9.
Fan
,
Y.
,
Xio
,
K.
,
Duan
,
H.
, and
Zhang
,
M.
,
2008
, “
Biomechanical and Histological Evaluation of the Application of Biodegradable Poly-L-Lactic Cushion to the Plate Internal Fixation for Bone Fracture Healing
,”
Clin. Biomech.
,
23
, pp.
S7
S16
.10.1016/j.clinbiomech.2008.01.005
10.
Board
,
T. N.
,
Yang
,
L.
, and
Saleh
,
M.
,
2007
, “
Why Fine-Wire Fixators Work: An Analysis of Pressure Distribution at the Wire-Bone Interface
,”
J. Biomech.
,
40
, pp.
20
25
.10.1016/j.jbiomech.2005.12.005
11.
Muller
,
M. E.
,
Allgower
,
M.
,
Schneider
,
R.
, and
Willeneger
,
H.
,
1979
,
Manual of Internal Fixation
,
2nd ed.
,
Springer-Verlag
,
New York
, Chap. 2.
12.
Prygoski
,
M. P.
,
Pasang
,
T.
,
Schmid
,
S. R.
, and
Lozier
,
A.
,
2011
, “
High Speed Insertion of Bone Fracture Fixation Pins: A Finite Element Penetration Model With Experimental Comparisons
,”
J. Mater. Sci.: Mater. Med.
,
22
(
12
), pp.
2823
2832
.10.1007/s10856-011-4461-x
13.
Gupta
,
A. P.
, and
Kumar
,
V.
,
2007
, “
New Emerging Trends in Synthetic Biodegradable Polymers—Polylactide: A Critique
,”
Eur. Polym. J.l
,
43
, pp.
4053
4074
.10.1016/j.eurpolymj.2007.06.045
14.
Yamadi
,
S.
, and
Kobayashi
,
S.
,
2009
, “
Effects of Strain Rate on the Mechanical Properties of Tricalcium Phosphate/Poly(L-Lactide) Composites
,”
J. Mater. Science: Mater. Med.
,
20
, pp.
67
74
.10.1007/s10856-008-3553-8
15.
Claes
,
L. E.
,
Ignatius
,
A. A.
,
Rehm
,
K. E.
, and
Scholz
,
C.
,
1996
, “
New Bioresorbable Pin for the Reduction of Small Bony Fragments: Design, Mechanical Properties and in vitro Degradation
,”
Biomaterials
,
17
(
16
), pp.
1621
1626
.10.1016/0142-9612(95)00327-4
16.
Staiger
,
M. P.
,
Pietak
,
A. M.
,
Huadmai
,
J.
, and
Dias
,
G.
,
2006
, “
Magnesium and its Alloys as Orthopedic Biomaterials: A Review
,”
Biomaterials
,
27
, pp.
1728
1734
.10.1016/j.biomaterials.2005.10.003
17.
Mueller
,
W.
,
de Mele
,
M.
,
Nascimento
,
M.
, and
Zeddies
,
M.
,
2009
, “
Degradation of Magnesium and its Alloys: Dependence on the Composition of the Synthetic Biological Media
,”
J. Biomed. Mater. Res.
,
90
(
A
), pp.
487
495
.10.1002/jbm.a.32106
18.
Witte
,
F.
,
Kaese
,
V.
,
Haferkamp
,
H.
,
Switzer
,
E.
,
Meyer-Lindenberg
,
A.
,
Wirth
,
C. J.
, and
Windhagen
,
H.
,
2005
, “
in vivo Corrosion of Four Magnesium Alloys and the Associated Bone Response
,”
Biomaterials
,
26
, pp.
3557
3563
.10.1016/j.biomaterials.2004.09.049
19.
Xu
,
L.
,
Yu
,
G.
,
Zhang
,
E.
,
Pan
,
F.
, and
Yang
,
K.
,
2007
, “
In Vivo Corrosion Behavior of Mg-Mn-Zn Alloy for Bone Implant Application
,”
J. Biomed. Mater. Res.
,
83
(
A
), pp.
703
711
.10.1002/jbm.a.31273
20.
O'Connor-Read
,
L. M.
,
Davidson
,
J. A.
,
Davies
,
B. M.
,
Matthews
,
M. G.
, and
Smirthwaite
,
P.
,
2008
, “
Comparative Endurance Testing of the Biomet Matthews Nail and the Dynamic Compression Screw, in Simulated Condylar and Supracondylar Femoral Fractures
,”
Biomed. Eng. Online
,
7
(
3
), pp.
1
7
.10.1186/1475-925X-7-3
21.
Viano
,
D. C.
, and
Stalnaker
,
R. L.
,
1980
, “
Mechanisms of Femoral Fracture
,”
J. Biomech.
,
13
, pp.
701
715
.10.1016/0021-9290(80)90356-5
22.
Atkinson
,
P. J.
, and
Haut
,
R. C.
,
2001
, “
Impact Responses of the Flexed Human Knee Using a Deformable Impact Interface
,”
ASME J. Biomech. Eng.
,
123
, pp.
205
211
.10.1115/1.1378576
23.
Sirbu
,
P. D.
,
Carata
,
E.
,
Petreus
,
T.
,
Asaftei
,
R.
, and
Botez
,
P.
,
2009
, “
Minimally Invasive Plate Osteosynthesis With Systems With Angular Stability in Complex Distal Femoral Fractures. Design, Biomechanics and Clinical Results
,”
IEEE Proceedings of the Advanced Technologies for Enhanced Quality of Life,
pp.
36
41
.
24.
Colton
,
C.
,
Gebhard
,
F.
,
Kregor
,
P.
, and
Oliver
,
C.
,
2011
, “
AO Surgery Reference: Distal Femur
,” AO Foundation, accessed 20 January 2011, www.aofoundation.org
25.
ASTM F1839
,
2008
, “
Standard Specification for Rigid Polyurethane Foam for Use as a Standard Material for Testing Orthopedic Devices and Instruments
,” ASTM International, West Conshohocken, PA.
26.
Kincaid
,
B.
,
Schroder
,
L.
, and
Mason
,
J.
,
2007
, “
Measurement of Orthopedic Cortical Bone Screw Insertion Performance in Cadaver Bone and Model Materials
,”
Exp. Mech.
,
47
, pp.
1
13
.
27.
Thompson
,
M. S.
,
McCarthy
,
I. D.
,
Lidgren
,
L.
, and
Ryd
,
L.
,
2003
, “
Compressive and Shear Properties of Commercially Available Polyurethane Foams
,”
ASME J. Biomech. Eng.
,
125
, pp.
732
734
.10.1115/1.1614820
28.
Hansen
,
U.
,
Zioupos
,
P.
,
Simpson
,
R.
,
Currey
,
J. D.
, and
Hynd
,
D.
,
2008
, “
The Effect of Strain Rate on the Mechanical Properties of Human Cortical Bone
,”
ASME J. Biomech. Eng.
,
130
, pp.
1
8
.10.1115/1.2838032
29.
Rincon-Kohli
,
L.
, and
Zysset
,
P. K.
,
2009
, “
Multi-Axial Mechanical Properties of Human Trabecular Bone
,”
Biomech. Model. Mechanobiol.
,
8
, pp.
195
208
.10.1007/s10237-008-0128-z
30.
Viceconti
,
M.
, “
Standard Femur Geometry
,” FEM Mesh Repository of the International Society of Biomechanics, Accessed August 2011, http://isbweb.org/data
31.
Morgan
,
E. F.
, and
Keaveny
,
T. M.
,
2001
, “
Dependence on Yield Strain of Human Trabecular Bone on Anatomic Site
,”
J. Biomech.
,
34
, pp.
569
577
.10.1016/S0021-9290(01)00011-2
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