Determining Material Specifications for A Biocompatible Implantable Mechanism5262015OmarSheikhv2
1. Determining Material Specifications for A
Biocompatible Implantable Mechanism to
Enhance Grasping
Omar Sheikh
Department of Chemical, Biological, and
Environmental Engineering
College of Engineering; Honors College
Oregon State University
May 26, 2015
1
2. Definitions
Determining Material Specifications
• Selecting Materials
Biocompatible Implantable Mechanism
• Safety of device
Modifying Force Transmission Inside the Body
• Device will split forces to make grasp less forceful
• Takes advantage of biomechanics
To Enhance Grasping
• Aim to improve hand grasping
2
3. My Timeline in the RHCS Lab
• Joined RHCS Lab in April 2013
• Interest in medical devices
• First used Open Sim Software
• Realized that I was more
interested in biomaterials
• Difficulty with software
• Changed roles within RHCS Lab
to focus on biocompatible
materials
• Looked at safety of device in body
2013
2014
2015
Graduation
• Completed research in May 2015
3
4. Research Questions
1. What are all the different materials useful for implants
that attach soft tissues to other soft tissues and/or bone?
2. What materials should be used for the proposed
pulley, lever, and tendon network forearm implants if the
goal is site-specific biocompatibility as defined above?
• Essentially: pick safe and appropriate materials
3. Following implantation, how should postoperative
care be performed to prevent both tendon adhesions and
muscle damage while helping the patient adapt to their
new grasp?
• This device is intended to improve patient quality of life
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5. Tendon Transfer Surgery
• Surgical procedure
– Transfers tendon(s) from a dysfunctional
muscle to a functioning (donor) muscle to
restore joint function
• Conventional procedure sutures
the tendon to the muscle
– Forceful grasp that makes holding objects
difficult
• Image on right
– Postoperative care
• Must be complete or lose gains from
surgery
5
6. Proposed Device Types
• Lever has same needs as pulley
• Use plastic tendon network to
transmit force
• Needs screws to stay taut
Device 3: Tendon Network
Device 2: Lever
• Pulley system rerouting tendons
Device 1: Pulley
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7. Proposed Devices
• Shared Components
– Anti-adhesion coating
• Improve device efficacy
– Cabling to connect tendon to
device
– Encapsulating bag filled with
hyaluronic acid
• Device will move inside
the body
– Must be safe and biocompatible
Device Components
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8. Device Needs and Goals
• Grasp is critical to major life activities
– Definition of disability
– Solutions improve patient life quality
• Current tendon transfer procedures do not improve grasp
substantially enough
– May have adhesions form (Allan 2011)
• Reduce range of motion
– This implant fulfills this need
• Device empowers patients
– Improve life quality
– Gives patient satisfaction
The goal of this device to improve postoperative
grasp after tendon transfer surgery
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9. Initial Testing
Initial designs included:
• Cadaver testing
– Pulley design
– Basis for OpenSim model
– Biomechanical testing
• OpenSim testing
– Biomechanical
simulation
– Ignore biocompatibility
– Simple model (only ECRL)
– Show that finger flexion
improves
o Force production and
o Range of motion (degrees)
10. Concerns: Biocompatibility
• When a device is implanted,
proteins/cells attach to the
surface, a fibrous capsule
forms around it, and
inflammation occurs (Ratner
and Bryant 2004)
– Reflects poor biocompatibility
and lowers device efficacy
– Improper response
• Biocompatible materials
requires:
– Site specific and safe for
situation
– Appropriate for implant needs
(adapted from Ratner et. al
2007)
– Consider tissue healing 10
11. Concerns: Skin, Tendon, Muscle
Healing
Why is this important?
– Device could cause harm to patients
– Healing can be fibrotic or regenerative
Tendon Muscle Skin
Bear large forces Exert mechanical action Undergoes reconstruction
post injury
Immune system aids
healing
Immune system
involvement
Immune system
involvement
Hyaluronic acid modulates
healing
Release creatinine kinase
when damaged
Use silicone gel sheets to
limit damage
(Voleti et. al 2012) (Shin et. al 2014) (Ogawa 2011)
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12. Concerns: Aspects for Materials
• Metals release ions into body (Bianco et. al 1996)
– Could be toxic
– Measure in serum and urine
• Release of wear particles from polymer/metal is
toxic (Bracco et. al 2011)
– Harm bone/other tissues
• Ceramic materials can be brittle
– But biocompatible (Warashima et. al 2003)
– Use in device is generally questionable
• Device durability
– Device should not release possibly toxic particles
– Device should be durable
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13. Concerns: Other Factors
Bacterial Infection Importance of
Mechanical
Environment
Toxicology Postoperative
Care
Spurred by device
implantation
Cells convert
physical forces into
chemical signaling
Many implant
materials
dangerous in a raw
form
Tissue healing
important to
consider
Poor biocompatibility
can harm immune cells
Mechanical
environment
critical
Helps distinguish
unsafe materials
from safe ones
Biocompatibility
seeks to enhance
this care
(Biomaterials Associated
Infection)
(Stamenovic and
Ingber 2009)
(Wright and
Welbourn 2002)
(Killian et. al 2012)
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14. Data Collection of Materials And
Methods
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Search Terms
Biomaterials
Stent
Joint Implants and Biomaterials
Total knee replacement
Total joint replacement
Biocompatibility
Foreign Body Response
Prosthetic
15. Data Collection of Materials And
Methods (Cont.)
Exclusion Criteria Rationale
Drug-eluting devices are excluded, including drug-
eluting stents
This literature survey aims to specify materials for a
device lacking bioactivity and achieves its goals mainly
through mechanical action not chemical action.
External devices are excluded. An external device does not have the proper
mechanical or chemical environment to model the
forearm device.
Exclude devices relying solely upon cement (bone or
teeth).
Using cement to hold a device in place or together
constitutes a very different set of mechanical
requirements than are present in this device,
Exclude implants that are exposed to obvious fluid
flow (especially blood-contacting implants such as
stents, catheters, and prosthetic heart valves).
The environment with high fluid flow represents the
wrong mechanical environment because a shear
component due to fluid flow is introduced
(Yoganathan et. al 2004), which is quite different from
the environment in which the device will be
implanted.
Exclude implants that are just implantation of a
material (i.e. performed solely for the sake of an
experiment).
These implants are typically only performed for the
sake of assessing material biocompatibility but do not
necessarily capture the mechanical environment.
Exclude devices using sutures as the main linkage. Implants that rely primarily on sutures are typically
connections between soft tissue, which represents a
different physiological setting.
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16. Selected Implants
Types of Implants Connections Materials Used
MCP and IP Prostheses
(Goldner and Urbaniak 1973)
Stems (cemented with PMMA) Silicone implant, UHWMPE
Breast Implant
(Puskas and Chen, 2004)
S.A./Tissue Ingrowth Silicone; silicone rubber bag is filled with
silicone gel and backed with polyester
mesh to encourage tissue ingrowth
Total Knee Replacement
(Illalov et. al 2013;
Biomaterials Science; Jacobs
et. al 2005)
(cementless) use pegs, screws, and stems UHMWPE, Porous Tantalum (cementless)
Total Hip Replacement
(Hulbert and Megremis
1996; Shanhbag et. al 1993;
Biomaterials Science)
Ti-6Al-4V stems UHMWPE (acetabular surface) and
Cobalt alloy (femoral head) or Ti-6Al-4V
(femoral head)
Total (Intervertebral) Disk
Arthroplasty (Biomaterials
science)
Ti-6Al-4V screws (1) Co-Cr (endplates), UHMWPE (core);
(2) Stainless Steel, Co alloy (endplates);
(3) Cobalt alloy (ball-and-socket joints),
Cobalt alloy (spring between joints)
Zygomatic Implants
(Prithviraj et. al 2014)
Commercially Pure Ti screws N/A
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17. Material Specifications
Device Component Material Device
Pulley UHMWPE-Vitamin E Pulley
Cabling Kevlar Pulley, Lever, Tendon
Network
Screws Ti6Al4V Tendon Network
Device Coating Poly(ethylene oxide) Pulley, Lever, Tendon
Network
Lever UHMWPE-Vitamin E Lever
Tendon Network Silastic Tendon Network
Bag Silicone Pulley, Lever, Tendon
Network
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18. Alternative Specifications
Device Component Material Rationale
Pulley Acetals, PEEK Biocompatible; has
orthopedic uses
Cabling Nylon Used in Sutures
Screws Tantalum Biocompatible; has
orthopedic uses
Device Coating Phosphorylcholine,
Pluronics
Effective at anti-adhesion
Lever Acetals, PEEK Biocompatible; has
orthopedic uses
Tendon Network Silastic’ Medical Grade
Slicone
Biocompatible and has
orthopedic uses
Bag Dacron, PET, Gore-Tex Biocompatible, many kinds
of uses
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19. Postoperative Care
• Questions to consider:
– Tissue healing
• Device biocompatibility and motion
• Device force transmission
– Device goals
• Muscle control is complex
– Redundant system
• Therapeutic exercises (Bowers and Lasardi 2007)
– Minimize movement dysfunction
– Avoid stressing tissues
• Avoid tendon shortening and adhesions
• Avoid pain
– Own experience with physical therapy
– Retain/improve range of motion 19
20. Postoperative Care (Cont.)
• Encourage patient healing and grasping
– Need appropriate mechanical loading to encourage healing (Killian
et. al 2012)
– Passive motion over cast immobilization
• Active motion may be difficult
– Need to monitor device and progressively increase length of sessions
– Measure muscle strength: (Shin et. al 2014)
• Electromyogram
– Electrical flow after muscular contraction
• Muscle grading scheme
– Rating 1-5
– Track tendon healing and assess potential damage
• Ultrasound/MRI
20
21. Postoperative Care (Cont.)
• Utilize a splint to allow for movement but
provide stretch
• Should be beneficial for patient
• Personally relevant
21
22. Survey Limitations
• Assumed that more widely
used is better
• Ignored article year,
age of implant,
and culture of researchers
• Limited by what’s out there
• All three have a significant impact on the materials chosen
– Is a slightly weak but completely safe material okay?
– Or, must it be absolutely strong at the potential cost of
biocompatibility?
– Should the device be “bio-inactive” materials?
• Material specifications
0
0.1
0.2
0.3
0.4
0.5
1.00 2.00 3.00 4.00 5.00 6.00
NormalizedReferenceCount
Time Since 1950 (Decades)
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23. Lessons Learned
• Survey procedures
– Important to look past orthopedic devices despite
biomechanical needs
– Learn about cool materials like PEEK and acetals
– Culture may play a role in how materials are chosen
• Surveying can be enhanced
– Look more at pacemakers, IUDs, neural prostheses
May help understanding of biocompatibility
– Ex: Nexplanon
• Contraceptive device
• Only example of a forearm actual implant
23
24. Future Work
• Model device heating up
– Model heat transfer
– Find way to cool
• Model predictions about device motion
– Damaging to body?
• Proof-of-concept biocompatibility tests on
prototype
– Simple experiments outside of body
– Do immune cells attach?
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26. Concluding Remarks
• Another way to think about it
• “Going Out On A Limb About Regrowing An
Arm” (Ratner 2013)
– Regenerative healing to regrow arm
– Ultimate goal of our device
• Regain use of arm
• Grasping is the most critical arm function
– Want to return use of arm to patient
– Ultimately want integration of device with body
• Improve efficacy and keep safety
• Encourage device support from FDA
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27. Selected References
1. Allan, Christopher H. “Repair of Acute Digital Flexor Tendon Disruptions.” “Operative Techniques in Orthopedic Surgery.” Ed.
Sam W. Wiesel. Philadelphia: Lippincott Williams & Wilkins, 2011. Print.
2. Bianco, P.D., P. Ducheyne, and J.M. Cuckler. “Local accumulation of titanium released from a titanium implant in the absence of
wear.” Journal of Biomedical Materials Research 31.2 (1996): 227-234. Print.
3. Bowers, Donna M., and Michelle M. Lusardi. “Motor Learning and Motor Control in Orthotic and Prosthetic Rehabilitation.”
Orthotics and Prosthetics in Rehabilitation Second Edition. Eds. Michelle M. Lusardi and Caroline C. Nielsen. St. Louis, Missouri:
Saunders Elsevier, 2007. 93-108. Print.
4. Bracco, Pierangiola and Ebru Oral. “Vitamin E-stabilized UHMWPE for Total Joint Implants.” Clin Orthop Relat Res 469(2011):
2286-2293. Print.
5. Bryers, James D. and Buddy D. Ratner. “Bioinspired Implant Materials Befuddle Bacteria.” ASM News 70.5(2004): 232-237.
Print.
6. Killian, Megan L., Leonardo Cavinatto, Leesa M. Galaltz, and Stavros Thomopoulos. “The role of mechanobiology in tendon
healing.” Journal of Shoulder and Elbow Surgery 21 (2012): 228-237.
7. Ogawa, Rei. “Mechanobiology of scarring.” Wound Repair and Regeneration (2011) 19: S2-S9. Print.
8. Biomaterials Associated Infection: Immunological Aspects and Antimicrobial Strategies. Eds. T. Fintan Moriarty, Sebastian A.J.
Zaat, and Henk J. Busscher. New York: Springer, 2013. Print.
9. Ratner, Buddy D. “A paradigm shift: biomaterials that heal.” Polymer International 56 (2007):1183-1185. Print.
10. Ratner, Buddy D. “Going out on a limb about regrowing an arm.” Journal of Materials Science – Materials in Medicine 24.11
(2013): 2645-2649. Print.
11. Biomaterials Science: An Introduction to Materials in Medicine. Eds. Ratner, Hoffman, Schoen, and Lemons. Academic Press,
2004.
12. Shin, Emily H., Edward J. Caterson, Wesley M. Jackson, and Leon J. Nesti. “Quality of healing: Defining, quantifying, and
enhancing skeletal muscle healing.” Wound Repair and Regeneration 22 (2014): 18-24. Print.
13. Stamenovic, Dimitrije and Donald Ingber. “Tensegrity-guided self assembly: from molecules to living cells.” Soft Matter 5.6
(2009). Print.
14. Tseng, Po-Yuan, Shyam S. Rele, Xue-Long Sun, and Elliot L. Chaikof. “Membrane-mimetic films containing thrombomodulin and
heparin inhibit tissue factor-induced thrombin generation in a flow model.” Biomaterials 27 (2006): 2637-2650. Print.
15. Warashima, Hideki, Shinji Sakano, Shinji Kitamura, Ken-Ichi Yamauchi, Jin Yamaguchi, Naoki Ishiguro, and Yukiharu Hasegawa.
“Biological reaction to alumina, zirconia, titanium, and polyethylene particles implanted onto murine calvaria.” Biomaterials 24
(2003): 3655-3661. Print.
16. Wright, David A. and Pamela Welbourn. Environmental Toxicology. Cambridge: Cambridge University Press, 2002. Pgs 249-
348.Print.
17. Voleti, Pramod B., M.R. Buckley, and L.J. Soslowsky. “Tendon Healing: Repair and Regeneration.” Annu Rev Biomed Eng 14
(2012):47-71. Print.
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