The properties of shape memory alloys, specifically the equiatomic intermetallic NiTi, are unique and significant in that they offer simple and effective solutions for some of the biomechanical issues encountered in orthopedics. Pedicle screws, used as an anchoring point for the implantation of spinal instrumentations in the spinal fracture and deformity treatments, entail the major drawback of loosening and backing out in osteoporotic bone. The strength of the screw contact with the surrounding bone diminishes as the bone degrades due to osteoporosis. The SMArtTM pedicle screw design is developed to address the existing issue in degraded bone. It is based on the interaction of bi-stable shape memory-superelastic elements. The bi-stable assembly acts antagonistically and consists of an external superelastic tube that expands the design protrusions when body temperature is attained; also an internal shape memory wire, inserted into the tube, retracts the assembly while locally heated to above the body temperature. This innovative bi-stable solution augments the pull-out resistance while still allowing for screw removal. The antagonistic wire-tube assembly was evaluated and parametrically analyzed as for the interaction of the superelastic tube and shape memory wire using a finite element model developed in COMSOL Multiphysics®. The outcomes of the simulation suggest that shape memory NiTi inserts on the SMArtTM pedicle screw can achieve the desired antagonistic functionality of expansion and retraction. Consequently, a parametric analysis was conducted over the effect of different sizes of wires and tubes. The dimensions for the first sample of this innovative pedicle screw were determined based on the results of this analysis.

References

References
1.
Otsuka
K.
, and
Wayman
,
C. M.
, eds., 1998,
Shape Memory Materials
,
Cambridge University
,
Cambridge, England
.
2.
Lagoudas
,
D.
, ed., 2008,
Shape Memory Alloys: Modeling and Engineering Applications
,
Springer-Verlag
,
New York.
3.
Yoneyama
,
T.
, and
Miyazaki
,
S.
, eds., 2009,
Shape Memory Alloys for Biomedical Applications
,
Woodhead Pub.
, Cambridge, England.
4.
Petrini
,
L.
, and
Migliavacca
,
F.
, 2011, “
Biomedical Applications of Shape Memory Alloys
,”
J. Metall.
,
2011
, pp.
1
15
.
5.
Dai
,
K. R.
,
Zhang
,
X. F.
, and
Yu
,
C. T.
, 1983, “
Orthopedic Application of a Ni-Ti Shape-Memory Alloy Compression Staple
,”
Chin. J. Surgery
,
21
(
6
), pp.
343
345
.
6.
Dai
,
K.
, 2000, “
Ti-Ni-Mo Shape Memory Alloys for Medical Applications
,”
Shape Memory Implants
,
Y.
L’Hocine
, ed.,
Springer
,
New York
.
7.
Yang
,
P. J.
,
Zhang
,
Y. F.
,
Ge
,
M. Z.
,
Cai
,
T. D.
,
Tao
,
J. C.
, and
Yang
,
H. P.
, 1987, “
Internal Fixation With Ni-Ti Shape Memory Alloy Compressive Staples in Orthopedic Surgery: A Review of 51 Cases
,”
Chin. Med. J.
,
100
(
9
), pp.
712
714
. Available at http://www.ncbi.nlm.nih.gov/pubmed/3127144http://www.ncbi.nlm.nih.gov/pubmed/3127144
8.
Yang
,
P. J.
,
Tao
,
J. C.
,
Ge
,
M. Z.
,
Yang
,
Q. M.
,
Yang
,
H. B.
, and
Sun
,
Q.
, 1992, “
Ni-Ti Memory Alloy Clamp Plate for Fracture of Short Tubular Bone
,”
Chin. Med. J.
,
105
(
4
), pp.
312
315
. Available at http://www.ncbi.nlm.nih.gov/pubmed/1618014http://www.ncbi.nlm.nih.gov/pubmed/1618014
9.
Tang
,
R. G.
,
Dai
,
K. R.
, and
Chen
,
Y. Q.
, 1996, “
Application of a NiTi Staple in the Metatarsal Osteotomy
,”
Biomed. Mater. Eng.
,
6
(
4
), pp.
307
312
.
10.
Drugacz
,
J.
,
Lekston
,
Z.
,
Morawiec
,
H.
, and
Januszewski
,
K.
, 1995, “
Use of TiNiCo Shape-Memory Clamps in the Surgical Treatment of Mandibular Fractures
,”
J. Oral Maxillofac. Surg.
,
53
(
6
), pp.
665
671
.
11.
Musialek
,
J.
,
Filip
,
P.
, and
Nieslanik
,
J.
, 1998, “
Titanium-Nickel Shape Memory Clamps in Small Bone Surgery
,”
Arch. Orthop. Trauma Surg.
,
117
(
6-7
), pp.
341
344
.
12.
Kuo
,
P. P.
,
Yang
,
P. J.
,
Zhang
,
Y. F.
,
Yang
,
H. B.
,
Yu
,
Y. F.
,
Dai
,
K. R.
,
Hong
,
W. Q.
,
Ke
,
M. Z.
,
Cai
,
T. D.
, and
Tao
,
J. C.
, 1989, “
The Use of Nickel-Titanium Alloy in Orthopedic Surgery in China
,”
Orthopedics
,
12
(
1
), pp.
111
116
. Available at http://www.ncbi.nlm.nih.gov/pubmed/2915940http://www.ncbi.nlm.nih.gov/pubmed/2915940
13.
Dai
,
K. R.
,
Hou
,
X. K.
,
Sun
,
Y. H.
,
Tang
,
R. G.
,
Qiu
,
S. J.
, and
Ni
,
C.
, 1993, “
Treatment of Intra-Articular Fractures With Shape Memory Compression Staples
,”
Injury
,
24
(
10
), pp.
651
655
.
14.
Barouk
,
L. S.
, 2000, “
The Double Compressive Nickel-Titanium Shape-Memory Staple in Foot Surgery
,”
Shape Memory Implants
,
Y.
L’Hocine
, ed.,
Springer
,
New York
.
15.
Zhang
,
C. C.
, 1989, “
Treatment of Patellar Fracture Using an Internal Fixator of Shape-Memory Alloy
,”
Chin. J. Surg.
,
27
(
11
), pp.
692
695
. Available at http://www.ncbi.nlm.nih.gov/pubmed/2632205http://www.ncbi.nlm.nih.gov/pubmed/2632205
16.
Wu
,
X.
,
Dai
,
K.
, and
Qiu
,
S.
, 1995, “
A Comparative Study of Effects on Bone Healing and Remodeling Between Embracing Fixator and Bone
,”
Chin. J. Surg.
,
33
(
8
), pp.
481
484
. Available at http://www.ncbi.nlm.nih.gov/pubmed/8706565http://www.ncbi.nlm.nih.gov/pubmed/8706565
17.
Mereau
,
T. M.
, and
Ford
,
T. C.
, 2006, “
Nitinol Compression Staples for Bone Fixation in Foot Surgery
,”
J. Am, Podiatr. Med. Assoc.
,
96
(
2
), pp.
102
106
. Available at http://www.japmaonline.org/content/96/2/102.shorthttp://www.japmaonline.org/content/96/2/102.short
18.
Zhao
,
D. L.
, 1984, “
Use of the Artificial Joint of NT-2 Shape-Memory Alloy for Cervical Intervertebral Articulation in Cervical Spondylosis in the Anterior Decompressive Operation
,”
Chin. J. Surg.
,
22
(
7
), pp.
410
412
. Available at http://www.ncbi.nlm.nih.gov/pubmed/6518895http://www.ncbi.nlm.nih.gov/pubmed/6518895
19.
Ricart
,
O.
, 2000, “
The Use of a Memory-Shape Staple in Cervical Anterior Fusion (About 100 Human Implantations)
,”
Shape Memory Implants
,
Y.
L’Hocine
, ed.,
Springer
,
New York
.
20.
Kim
,
Y.
, and
Zhang
,
H.
, 2006, “
Shape Memory Implant (KIMPF-DI Fixing) System
,”
Dynamic Reconstruction of the Spine
,
D.
Kim
,
F.
Cammisa
, and
R.
Fessler
, eds.,
Thieme Medical Publishers Inc.
,
New York
.
21.
Silberstein
,
B. M.
, and
Gunter
,
V.
, 2000, “
Shape Memory Implants in Spinal Surgery: Long-Term Results (Experimental and Clinical Studies)
,”
Shape Memory Implants
,
Y.
L’Hocine
, ed.,
Springer
,
New York
.
22.
Kujala
,
S.
,
Ryhänen
,
J.
,
Jämsä
,
T.
,
Danilov
,
A.
,
Saaranen
,
J.
,
Pramila
,
A.
, and
Tuukkanen
,
J.
, 2002, “
Bone Modeling Controlled by a Nickel-Titanium Shape Memory Alloy Intramedullary Nail
,”
Biomaterials
,
23
, pp.
2535
2543
.
23.
Xu
,
W.
,
Frank
,
T. G.
,
Stockham
,
G.
, and
Cuschieri
,
A
, 1999, “
Shape Memory Alloy Fixator System for Suturing Tissue in Minimal Access Surgery
,”
Annals Biomed. Eng.
,
27
(
5
), pp.
663
669
.
24.
Tomitsuka
,
K.
, 1991, “
Study of Mechanical Properties of Shape Memory Alloy Plate for Internal Fixation of Jaws
,”
J. Stomatol. Soc.
,
58
(
1
), pp.
59
73
.
25.
Dai
,
K. R.
,
Ni
,
C.
, and
Wu
,
X. T.
, 1994, “
An Experimental Study and Preliminary Clinical Report of Shape-Memory Saw Tooth-Arm Embracing Internal Fixator
,”
Chin. J. Surg.
,
32
(
10
), pp.
629
632
. Available at http://www.ncbi.nlm.nih.gov/pubmed/7750426http://www.ncbi.nlm.nih.gov/pubmed/7750426
26.
Sanders
,
J. O.
,
Sanders
,
A. E.
,
More
,
R.
, and
Ashman
,
R. B.
, 1993, “
A Preliminary Investigation of Shape Memory Alloys in the Surgical Correction of Scoliosis
,”
Spine
,
18
(
12
), pp.
1640
1646
.
27.
Veldhuizen
,
A. G.
,
Sanders
,
M. M.
, and
Cool
,
J. C.
, 1997, “
A Scoliosis Correction Device Based on Memory Metal
,”
Med. Eng. Phys.
,
19
(
2
), pp.
171
179
.
28.
Wever
,
D. J.
,
Elstrodt
,
J. A.
,
Veldhuizen
,
A. G.
, and
Horn
,
J. R.
, 2002, “
Scoliosis Correction With Shape-Memory Metal: Results of an Experimental Study
,”
Eur. Spine J.
,
11
, pp.
100
106
.
29.
Schmerling
,
M. A.
,
Wilkov
,
M. A.
,
Sanders
,
A. E.
, and
Woosley
,
J. E.
, 1976, “
Using the Shape Recovery of Nitinol in the Harrington Rod Treatment of Scoliosis
,”
J. Biomed. Mater. Res.
,
10
(
6
), pp.
879
892
.
30.
Jinfang
,
G.
,
Ping
,
I.
,
Jifang
,
W.
, and
Li
,
S.
, 1990, “
Scoliosis Correction Rods of Ti-Ni Alloy and Clinical Application
,” Proceedings of the International Symposium of Shape Memory Alloys, Guilin, China, 1986,
China Academic Publisher
, Beijing, China.
31.
Melton
,
L. J.
, 1997, “
Epidemiology of Spinal Osteoporosis
,”
Spine
,
22
(
24S
), Supp.
2S
11S
.
32.
Glassman
,
S. D.
, and
Alegre
,
G. M.
, 2003, “
Adult Spinal Deformity in the Osteoporotic Spine: Options and Pitfalls
,”
Instr. Course Lect.
,
52
, pp.
579
588
. Available at http://www.ncbi.nlm.nih.gov/pubmed/12690884http://www.ncbi.nlm.nih.gov/pubmed/12690884
33.
Shigeru
,
S.
,
Shiba
,
R.
,
Kondo
,
H.
, and
Murota
,
K.
, 1991, “
An Experimental Study on Transpedicular Screw Fixation in Relation to Osteoporosis of the Lumbar Spine
,”
Spine
,
16
(
11
), pp.
1335
1341
.
34.
Hu
,
S. S.
, 1997, “
Internal Fixation in the Osteoporotic Spine
,”
Spine
,
22
(
24S
), Supp.
43S
48S
.
35.
Gaines
,
R. W.
, 2000, “
The Use of Pedicle-Screw Internal Fixation for the Operative Treatment of Spinal Disorder
,”
J. Bone Jt. Surg., Am.
,
82
, pp.
1458
1476
.
36.
Inceoglu
,
S.
, 2004, “
Failure of Pedicle Screw-Bone Interface: Biomechanics of Pedicle Screw Insertion and Pullout
,” Ph.D. thesis, Cleveland State University, Cleveland, OH.
37.
Yuan
,
H. A.
,
Garfin
S. R.
,
Dickman
,
C. A.
, and
Mardjetko
,
S. M.
, 1994, “
A Historical Cohort Study of Pedicle Screw Fixation in Thoracic, Lumbar, and Sacral Spine Fusion
,”
Spine
,
19
(20S), Supp. pp.
2279S
2296S
.
38.
Hasegawa
,
K.
,
Takahashi
,
H. E.
,
Takahashi
,
H. E.
,
Uchiyama
,
S.
,
Hirano
,
T.
,
Hara
,
T.
,
Washio
,
T.
,
Sugiura
,
T.
,
Youkaichiya
,
M.
, and
Ikeda
,
M.
, 1997, “
An Experimental Study of a Combination Method Using a Pedicle Screw and Laminar Hook for the Osteoporotic Spine
,”
Spine
,
22
(
9
), pp.
958
962
.
39.
Chiba
,
M.
,
McLain
,
R. F.
,
Yerby
,
S. A.
,
Moseley
,
T. A.
,
Smith
,
T. S.
, and
Benson
,
D. R.
, 1996, “
Short-Segment Pedicle Instrumentation: Biomechanical Analysis of Supplemental Hook Fixation
,”
Spine
,
21
, pp.
288
294
.
40.
Sarzier
,
J. S.
,
Evans
,
A. J.
, and
Cahill
,
D. W.
, 2002, “
Increased Pedicle Screw Pullout Strength With Vertebroplasty Augmentation in Osteoporotic Spine
,”
J. Neurosurg.
,
96
, pp.
309
312
.
41.
Zdeblick
,
T. A.
,
Kunaz
,
D. N.
,
Cook
,
M. E.
, and
McCabe
,
R.
, 1993, “
Pedicle Screw Pull-Out Strength: Correlation With Insertional Torque
,”
Spine
,
18
, pp.
1673
1676
.
42.
Battula
,
S.
,
Schoenfeld
,
A. J.
,
Sahai
,
V.
,
Vrabec
,
G. A.
,
Tank
,
J.
, and
Njus
,
G. O.
, 2008, “
The Effect of Pilot Hole Size on the Insertion Torque and Pullout Strength of Self-Tapping Cortical Bone Screws in Osteoporotic Bone
,”
J. Trauma; Inj. Infect., Crit. Care
,
64
(
4
), pp.
990
995
.
43.
Daftari
,
T. K.
,
Horton
,
W. C.
, and
Hutton
,
W.C.
, 1994, “
Correlations Between Screw Hole Preparation, Torque of Insertion, and Pullout Strength for Spinal Screws
,”
J. Spinal Disord.
,
7
, pp.
139
145
.
44.
Abshire
,
B. B.
,
McLain
,
R. F.
,
Valdevit
,
A.
, and
Kambic
,
H. E.
, 2001, “
Characteristics of Pullout Failure in Conical and Cylindrical Pedicle Screws After Full Insertion and Back-Out
,”
Spine J.
,
1
,
408
414
.
45.
Zindrick
,
M. R.
,
Wiltse
,
L. L.
,
Widell
,
E. H.
,
Thomas
,
J. C.
,
Holland
,
W. R.
,
Field
,
F. T.
, and
Spencer
,
C. W.
, 1986, “
A Biomechanical Study of Intrapedicular Screw Fixation in the Lumbosacral Spine
,”
Clin. Orthop.
,
203
, pp.
99
112
.
46.
Lotz
,
J. C.
,
Hu
,
S. S.
,
Chiu
,
D. F. M.
,
Yu
,
M.
,
Colliou
,
O.
, and
Poser
,
R. D.
, 1997, “
Carbonated Apatite Cement Augmentation of Pedicle Screw Fixation in the Lumbar Spine
,”
Spine
,
22
, pp.
2716
2723
.
47.
Wuisman
,
P. I. J. M.
,
Dijk
,
M. V.
,
Staal
,
H.
, and
Royen
,
B. J.
, 2000, “
Augmentation of (Pedicle) Screws With Calcium Apatite Cement in Patients With Severe Progressive Osteoporotic Spinal Deformities: An Innovative Technique
,”
Eur. Spine J.
,
9
(
6
), pp.
528
533
.
48.
Moore
,
D. C.
,
Maitra
,
R. S.
,
Farjo
,
L. A.
,
Graziano
,
G. P.
, and
Goldstein
,
S. A.
, 1997, “
Restoration of Pedicle Screw Fixation With an In Situ Setting Calcium Phosphate Cement
,”
Spine
,
22
, pp.
1696
1705
.
49.
Hasegawa
,
T.
,
Inufusa
A.
,
Imai
,
Y.
,
Mikawa
,
Y.
,
Lim
,
T.
, and
An
,
H.
, 2005, “
Hydroxyapatite-Coating of Pedicle Screws Improves Resistance Against Pull-Out Force in the Osteoporotic Canine Lumbar Spine Model: A Pilot Study
,”
Spine J.
,
5
, pp.
239
243
.
50.
Sandén
,
B.
,
Olerud
,
C.
,
Johansson
,
C.
, and
Larsson
,
S.
, 2000, “
Improved Extraction Torque of Hydroxyapatite-Coated Pedicle Screws
,”
Eur. Spine J.
,
9
, pp.
534
537
.
51.
Sandén
,
B.
,
Olerud
,
C.
, and
Larsson
,
S.
, 2001, “
Hydroxyapatite Coating Enhances Fixation of Loaded Pedicle Screws: A Mechanical In Vivo Study in Sheep
,”
Eur. Spine J.
,
10
, pp.
334
339
.
52.
Cook
,
S. D.
,
Salkeld
,
S. L.
,
Stanley
,
T.
,
Faciane
,
A.
, and
Miler
,
S. D.
, 2004, “
Biomechanical Study of Pedicle Screw Fixation in Severely Osteoporotic Bone
,”
Spine J.
,
4
, pp.
402
408
.
53.
Waits
,
C.
,
Burton
,
D.
,
McIff
,
T.
,
Asher
,
M.
, and
Glattes
,
R.
, 2007, “
Cement-Augmentation of Pedicle Screw Fixation Using Novel Cannulated Cement Insertion Device
,”
Spine J.
,
7
(
5
), Supp. 1, pp.
25S
26S
54.
Eriksson
,
A. R.
, and
Albrektsson
,
T.
, 1983, “
Temperature Threshold Levels for Heat-Induced Bone Tissue Injury: A Vital-Microscopic Study in the Rabbit
,”
J. Prosthet. Dent.
,
50
(
1
), pp.
101
107
.
You do not currently have access to this content.