ASTM F3223-17

Standard Guide for Characterization and Assessment of Tissue Engineered Medical Products (TEMPs) for Knee Meniscus Surgical Repair and/or Reconstruction

SIGNIFICANCE AND USE
5.1 Injuries to the knee meniscus are one of the most common orthopaedic problems. Meniscus injures include acute tears (such as occur in sports injuries), chronic degenerative tears, extrusion/subluxation, and/or degenerative dysfunction that occurs as part of the knee aging process or as a result of multiple meniscus surgeries. Knee arthroscopy for partial excision of the knee meniscus (partial meniscectomy) is the most commonly performed orthopaedic procedure.  
5.2 Complete or near complete excision of the meniscus in a young individual is associated with an early increased risk of knee osteoarthritis due to the loss of the meniscus chondroprotective effects. Lateral meniscal injuries tend to be more severe than medial injuries. Meniscus repair, augmentation, transplantation, and/or reconstruction is recommended in individuals to restore the chondroprotective effect of the meniscus, relieve pain, and prevent degenerative knee osteoarthritis. The potential of TEMPs to enhance the outcome of the surgical meniscus repair and/or reconstruction has been recognized.  
5.3 The knee joint and temporomandibular joint (TMJ) are examples of joints with meniscal structures.  
5.4 TEMPS may be used with the intent of enhancing the surgical outcome by improving the biological repair at the site of implantation, by providing mechanical function at a defect site, or by a combination of these mechanisms.  
5.5 Improving surgical outcome may include improving function relative to the pre-operative condition, shortening the recovery time after surgery, relieving pain, enabling return to normal daily activities, encouraging tissue growth into the defect site, restoring the mechanical function of the meniscus, delaying the progression of osteoarthritis, or any combination thereof.
SCOPE
1.1 This guide is intended as a resource for individuals and organizations involved in the production, delivery, and regulation of tissue engineered medical products (TEMPs) and other tissues intended for use in the surgical repair, replacement, and/or reconstruction of the knee meniscus.  
1.2 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.  
1.3 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

General Information

• Status: Published
• Publication Date: 28-Feb-2017
• ICS: 11.040.40 - Implants for surgery, prosthetics and orthotics
• Technical Committee: F04 - Medical and Surgical Materials and Devices
• Drafting Committee: F04.44 - Assessment for TEMPs

Relations

• Refers: ASTM F2312-11(2020) - Standard Terminology Relating to Tissue Engineered Medical Products
• Effective Date: 01-Feb-2020
• Refers: ASTM F2150-19 - Standard Guide for Characterization and Testing of Biomaterial Scaffolds Used in Regenerative Medicine and Tissue-Engineered Medical Products
• Effective Date: 01-Oct-2019
• Refers: ASTM F2739-19 - Standard Guide for Quantifying Cell Viability and Related Attributes within Biomaterial Scaffolds
• Effective Date: 01-Sep-2019
• Refers: ASTM F1635-16 - Standard Test Method for <emph type="bdit">in vitro</emph> Degradation Testing of Hydrolytically Degradable Polymer Resins and Fabricated Forms for Surgical Implants
• Effective Date: 01-Dec-2016
• Refers: ASTM F2739-16 - Standard Guide for Quantifying Cell Viability within Biomaterial Scaffolds
• Effective Date: 01-Oct-2016
• Refers: ASTM F2150-13 - Standard Guide for Characterization and Testing of Biomaterial Scaffolds Used in Tissue-Engineered Medical Products
• Effective Date: 01-Oct-2013
• Refers: ASTM F2312-11 - Standard Terminology Relating to Tissue Engineered Medical Products
• Effective Date: 01-Apr-2011
• Refers: ASTM F2212-11 - Standard Guide for Characterization of Type I Collagen as Starting Material for Surgical Implants and Substrates for Tissue Engineered Medical Products (TEMPs)
• Effective Date: 01-Apr-2011
• Refers: ASTM F1635-11 - Standard Test Method for <i>in vitro</i> Degradation Testing of Hydrolytically Degradable Polymer Resins and Fabricated Forms for Surgical Implants
• Effective Date: 01-Mar-2011
• Refers: ASTM F2210-02(2010) - Standard Guide for Processing Cells, Tissues, and Organs for Use in Tissue Engineered Medical Products (Withdrawn 2015)
• Effective Date: 01-Dec-2010
• Refers: ASTM F2312-10 - Standard Terminology Relating to Tissue Engineered Medical Products
• Effective Date: 01-Jun-2010
• Refers: ASTM F2212-09 - Standard Guide for Characterization of Type I Collagen as Starting Material for Surgical Implants and Substrates for Tissue Engineered Medical Products (TEMPs)
• Effective Date: 01-Aug-2009
• Refers: ASTM F2739-08 - Standard Guide for Quantitating Cell Viability Within Biomaterial Scaffolds
• Effective Date: 01-Aug-2008
• Refers: ASTM F2212-08e1 - Standard Guide for Characterization of Type I Collagen as Starting Material for Surgical Implants and Substrates for Tissue Engineered Medical Products (TEMPs)
• Effective Date: 01-Feb-2008
• Refers: ASTM F2212-08 - Standard Guide for Characterization of Type I Collagen as Starting Material for Surgical Implants and Substrates for Tissue Engineered Medical Products (TEMPs)
• Effective Date: 01-Feb-2008

Overview

ASTM F3223-17 provides standardized guidance for the characterization and assessment of Tissue Engineered Medical Products (TEMPs) intended for the surgical repair, replacement, augmentation, or reconstruction of the knee meniscus. Injuries to the knee meniscus are among the most common orthopedic issues, often resulting from trauma, degeneration, or repeated surgical intervention. This guide is an essential resource for manufacturers, healthcare providers, and regulatory authorities involved in the development, evaluation, and implementation of knee meniscus TEMPs.

Meniscus loss or significant damage is associated with an increased risk of early knee osteoarthritis, making restoration of meniscal function critically important. The use of TEMPs has shown promise in improving surgical outcomes by supporting tissue regeneration, restoring knee biomechanics, reducing recovery time, and helping to prevent the progression of degenerative joint disease.

Key Topics

• Scope and Purpose: This guide outlines best practices for the development and evaluation of TEMPs for the knee meniscus, focusing on their functional, structural, and biological properties.
• Tissue Composition and Properties:
  • Cell Types: The standard highlights the importance of characterizing allogeneic (donor) and autologous (patient-derived) cells used in TEMPs.
  • Extracellular Matrix Components: Guidance is provided on quantifying collagen (types I and II) and proteoglycan content, essential for TEMP performance.
• Mechanical and Physical Testing: Recommendations for tensile, compressive, viscoelastic, and wear testing ensure that products can withstand the biomechanical demands of the knee joint.
• Sterilization and Packaging: The importance of maintaining sterility and aseptic conditions during manufacture, storage, and transport is emphasized.
• Biological and Functional Integration: Evaluation of biologic responses, tissue integration, and chondroprotective effects are detailed for in vitro and in vivo testing.
• Patient Outcomes: The document addresses the importance of patient-reported outcome (PRO) measures to assess functional and quality-of-life improvements following meniscal repair with TEMPs.

Applications

The guidance in ASTM F3223-17 supports a wide range of applications in knee meniscus repair and regeneration:

• Clinical Use: Provides a framework for surgeons and clinicians to assess the suitability and effectiveness of TEMPs for meniscus repair, augmentation, or reconstruction.
• Product Development: Informs manufacturers on the necessary design, testing, and validation procedures to create consistent and reliable TEMP devices.
• Regulatory Submissions: Facilitates compliance with international standards and assists regulatory agencies in the review and approval of new tissue engineered medical products.
• Quality Assurance: Outlines criteria for the characterization and quality control of biomaterials, cells, and final products to ensure patient safety and product efficacy.
• Research: Serves as a reference for academic and industry research teams studying regenerative approaches to knee joint disease and injury.

Related Standards

ASTM F3223-17 references and aligns with several key standards and regulatory frameworks to promote harmonization and best practices:

• ASTM F2211 - Classification for Tissue Engineered Medical Products (TEMPs)
• ASTM F2150 - Guide for Characterization and Testing of Biomaterial Scaffolds Used in TEMPs
• ASTM F2212 - Guide for Characterization of Type I Collagen as Starting Material for Surgical Implants and TEMPs
• ISO 10993-1 - Biological Evaluation of Medical Devices
• ISO 13022:2012 - Medical Products Containing Viable Human Cells
• ISO 18362:2016 - Manufacture of Cell-based Health Care Products
• 21 CFR 820/1270/1271 - US FDA Current Good Manufacturing Practices (cGMP) for Human Tissues and Devices

By following ASTM F3223-17, stakeholders ensure that tissue engineered products for knee meniscus repair are safe, effective, and of high quality, ultimately supporting better patient outcomes and the advancement of regenerative orthopedics.

Standards Content (Sample)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: F3223 − 17
Standard Guide for
Characterization and Assessment of Tissue Engineered
Medical Products (TEMPs) for Knee Meniscus Surgical
Repair and/or Reconstruction
This standard is issued under the fixed designation F3223; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope F2211 Classification for Tissue Engineered Medical Prod-
ucts (TEMPs)
1.1 This guide is intended as a resource for individuals and
F2212 Guide for Characterization of Type I Collagen as
organizations involved in the production, delivery, and regula-
Starting Material for Surgical Implants and Substrates for
tion of tissue engineered medical products (TEMPs) and other
Tissue Engineered Medical Products (TEMPs)
tissues intended for use in the surgical repair, replacement,
F2312 Terminology Relating to Tissue Engineered Medical
and/or reconstruction of the knee meniscus.
Products
1.2 This standard does not purport to address all of the
F2386 Guide for Preservation of Tissue Engineered Medical
safety concerns, if any, associated with its use. It is the
Products (TEMPs) (Withdrawn 2013)
responsibility of the user of this standard to establish appro-
F2739 Guide for Quantifying Cell Viability within Bioma-
priate safety and health practices and determine the applica-
terial Scaffolds
bility of regulatory limitations prior to use.
2.2 ISO Standards:
1.3 This international standard was developed in accor-
ISO 10993-1 Biological evaluation of medical devices
dance with internationally recognized principles on standard-
ISO 13022:2012 Medical products containing viable human
ization established in the Decision on Principles for the
cells—Application of risk management and requirements
Development of International Standards, Guides and Recom-
for processing practices
mendations issued by the World Trade Organization Technical
ISO 18362:2016 Manufacture of cell-based health care
Barriers to Trade (TBT) Committee.
products—Control of microbial risks during processing
2. Referenced Documents
2.3 Code of Federal Regulations
CFR 610.12 General Biological Products Standards—
2.1 ASTM Standards:
Sterility
D570 Test Method for Water Absorption of Plastics
CFR 820 Current Good Manufacturing Practice for Quality
F1635 Test Method forin vitro Degradation Testing of Hy-
System Regulation
drolytically Degradable Polymer Resins and Fabricated
CFR 1270 Current Good Manufacturing Practice for Human
Forms for Surgical Implants
Tissue Intended for Transplantation
F2150 Guide for Characterization and Testing of Biomate-
CFR 1271 Current Good Manufacturing Practice for Human
rial Scaffolds Used in Tissue-Engineered Medical Prod-
Cells, Tissues, and Cellular and Tissue-Based Products
ucts
F2210 Guide for Processing Cells, Tissues, and Organs for
3. Terminology
Use in Tissue Engineered Medical Products (Withdrawn
2015)
3.1 Unless provided otherwise in 3.2, terminology shall be
in conformance with Terminology F2312.
3.2 Definitions of Terms Specific to This Standard:
This test method is under the jurisdiction ofASTM Committee F04 on Medical
3.2.1 ECM, n—extracellular matrix.
and Surgical Materials and Devices and is the direct responsibility of Subcommittee
F04.44 on Assessment for TEMPs.
Current edition approved March 1, 2017. Published June 2017. DOI: 10.1520/
F3223-17.
2 4
For referenced ASTM standards, visit the ASTM website, www.astm.org, or Available from International Organization for Standardization (ISO), ISO
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Central Secretariat, BIBC II, Chemin de Blandonnet 8, CP 401, 1214 Vernier,
Standards volume information, refer to the standard’s Document Summary page on Geneva, Switzerland, http://www.iso.org.
the ASTM website. Available from U.S. Government Printing Office, Superintendent of
The last approved version of this historical standard is referenced on Documents, 732 N. Capitol St., NW, Washington, DC 20401-0001, http://
www.astm.org. www.access.gpo.gov.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
F3223 − 17
3.2.2 osteoarthritis (OA), n—a disease of the entire joint knee osteoarthritis due to the loss of the meniscus chondropro-
involving the cartilage, joint lining, ligaments, and underlying tective effects. Lateral meniscal injuries tend to be more severe
bone. than medial injuries. Meniscus repair, augmentation,
transplantation, and/or reconstruction is recommended in indi-
3.2.3 product, n—TEMPs, and other tissues or devices used
viduals to restore the chondroprotective effect of the meniscus,
in the surgical repair, replacement, augmentation and/or recon-
relieve pain, and prevent degenerative knee osteoarthritis. The
struction of the knee meniscus.
potential of TEMPs to enhance the outcome of the surgical
3.2.4 surgical reconstruction, n—surgical procedure to pro-
meniscus repair and/or reconstruction has been recognized.
mote healing of replacement meniscus structure.
5.3 The knee joint and temporomandibular joint (TMJ) are
3.2.5 surgical repair, n—surgical procedure to promote
examples of joints with meniscal structures.
healing of native meniscus structure.
5.4 TEMPS may be used with the intent of enhancing the
4. Summary of Guide surgical outcome by improving the biological repair at the site
of implantation, by providing mechanical function at a defect
4.1 It is the intent of this guide to provide a compendium of
site, or by a combination of these mechanisms.
informationthatmayberelatedtothefunctionalcharacteristics
5.5 Improving surgical outcome may include improving
of TEMPs, and other tissues or devices used in the surgical
function relative to the pre-operative condition, shortening the
repair, replacement, augmentation and/or reconstruction of the
recovery time after surgery, relieving pain, enabling return to
knee meniscus. TEMPs may be composed of biological prod-
normal daily activities, encouraging tissue growth into the
ucts (for example, cells, organs, tissues (both human and
defect site, restoring the mechanical function of the meniscus,
xenograft), derivatives, and processed biologics), biomaterials
delaying the progression of osteoarthritis, or any combination
(for example, substrates and scaffolds composed of polymers,
thereof.
extra-cellular matrices or collagen), and biomolecules (for
example, recombinant proteins, alginates, and hyaluronates)
6. Cells
(see Terminology F2312). Examples of TEMPs are listed in
Classification F2211.
6.1 Cell Types—Cell-seeded products may be used.The cell
populationmaybeallogenicorautologous.Celltypeshouldbe
4.2 The reader is referred to other documents that may
defined in order to provide accurate and comprehensive mate-
provide specific information that can be applied in the process-
rials and methods descriptions so that studies can be repeated,
ing and manufacture (Guide F2210, ISO 18362: 2016), char-
the mechanisms of action can be understood and clinical
acterization and testing (Guide F2150; ISO 10993-1) and the
feasibilityandregulatoryaspectscanbeascertained.Suggested
preservation, storage, transport, recovery, post-preservation
cell populations include: (a) meniscal fibrochondrocytes, (b)
processing, quality assurance, and process control (Guide
mesenchymal stem cells (MSCs)/induced pluripotent stem
F2386-04, ISO 13022:2012) of TEMPs. Section 2 lists refer-
cells (iPSCs)/embryonic stem cells (ESCs), or (c) synovio-
enced standards and particularly relevant Code of Federal
cytes. Cells may be allogeneic or autologous. Allogeneic cells
Regulations (CFR).
should be isolated, prepared, and stored at a cell/tissue bank.
4.3 The application of this guide does not guarantee clinical
These cells may have undergone substantial proliferation prior
success of a finished product but will help to ensure consis-
to being seeded into the TEMPs product, and the cell pheno-
tency in the properties, testing, and characterization of a given
type should be characterized and compared to a population of
TEMP or device developed for the purpose of enhancing
freshly isolated or early passage cells. It is intended that the
surgical repair, replacement, augmentation and/or reconstruc-
cells in the cell/tissue bank should have significant similarities
tion of the knee meniscus.
to the fresh or early passage cells, in particular for properties
4.4 This guide does not suggest that all the listed tests be that are critical for formation and function of the TEMPs, such
conducted. The decision regarding applicability or suitability as production of types I and II collagen and sulfated gly-
of any particular test method remains the responsibility of the cosaminoglycans (sGAGs). Autologous cells may be isolated
supplier, user, or regulator of the material based on applicable and re-implanted during the same surgical procedure, or
regulations, characterizations, and preclinical/clinical testing. undergo proliferation prior to re-implantation. However, like
the allogeneic cells, the autologous cells should be managed to
5. Significance and Use undergo minimal changes during manipulation.
5.1 Injuries to the knee meniscus are one of the most 6.2 Cell Performance Requirements—Cell lines should be
commonorthopaedicproblems.Meniscusinjuresincludeacute established, maintained, and supplied in line with existing
tears (such as occur in sports injuries), chronic degenerative recommendations (1, 2, 3, 4, 5). In formation of theTEMPs in
tears, extrusion/subluxation, and/or degenerative dysfunction vitro,thecellswillbecombinedwithbiomaterials,andmustbe
that occurs as part of the knee aging process or as a result of able to attach to the biomaterial and/or extracellular matrix
multiple meniscus surgeries. Knee arthroscopy for partial (ECM) of the TEMPs. For some TEMPs, the cells should be
excision of the knee meniscus (partial meniscectomy) is the able to proliferate and secrete a functional ECM in vitro.When
most commonly performed orthopaedic procedure.
5.2 Complete or near complete excision of the meniscus in
The boldface numbers in parentheses refer to the list of references at the end of
a young individual is associated with an early increased risk of this standard.
F3223 − 17
implanted, the cells may be required to synthesize an ECM in V and VI all reported in meniscal tissue. However type I
vivo, function in biologic repair, or resorb, but the implanted collagen is the most abundant type accounting for over 90% of
cells and biomaterials should not induce immune or inflamma- collagen in the meniscus, with type II being the second most
tory responses that prevent meniscus repair. Both allogeneic abundant. Type I collagen is primarily organized into circum-
and autologous cells that undergo expansion and proliferation ferential fibers within the peripheral zone of the meniscus and
in vitro should be characterized for their differentiation capac- helps the meniscus resist hoop stresses. Type II collagen is
ity into a fibrochondrogeneic phenotype (producing type I and primarily found in the more highly compressed inner, white
II collagen and sGAGs). zone. Total collagen content of the TEMPs can be determined
by papain digestion of the tissue constructs. Collagen content
7. Attachment and Incorporation
can be measured using a hydroxyproline assay with trans-4-
7.1 Attachment in vivo—The product should provide or be
hydroxyproline standards (6, 7, 8). However, this assay does
adaptable to clinically applicable anchoring or fixation meth-
not distinguish between types of collagen. Immunohistochemi-
ods to enable attachment to the extent needed to enable
cal staining can be utilized to identify the specific collagen
function. Fixation methods include anchoring via sutures,
types, such as types I, II, III, V, and VI. The orientation and
specifically designed meniscus fixation devices, anchors,
arrangement of collagen fibrils within the TEMP is also
screws, and bone blocks to enable attachment to the meniscal
important for functional tissue. Therefore, picrosirius red
remnant, capsule, and/or bone.The products should be capable
staining may be used to assess collagen alignment and orga-
of retaining sutures, fixation devices, or anchors in a manner
nizationthroughouttheTEMPs.ThereaderisreferredtoGuide
that is appropriate for the surgical procedure. Once implanted
F2212 for the characterization of Type I collagen as a starting
and fixed, the product should be retained in place for the time
material for TEMPs.
required for it to complete its functional requirements and
10.3 Proteoglycans/Glycosaminoglycans—Proteoglycans
maintain or at least restore the ability of the structure to
are the second major component of the meniscus (~0.8% of the
withstandphysiologicalhoopstressesandprovidechondropro-
wet weight); however, they are found primarily in the inner,
tection.
white zone of the meniscus and are approximately eightfold
less common than that found in articular cartilage. The most
8. Sterilization
common large sulfated glycosaminoglycans found in the me-
8.1 Theproductshallbeprovidedsteriletotheclinicalfield.
niscus are chondroitin-6-sulfate, chondroitin-4-sulfate, derma-
Acellular products may be sterilized after manufacture by a
tan sulfate, and keratin sulfate. The most common large
number of different techniques, some examples of which are:
proteoglycan is aggrecan, with decorin and biglycan being the
ethylene oxide, gamma irradiation, or plasma irradiation. If the
most common small proteoglycans. Total glycosaminoglycan
product is cellular, the product may be maintained aseptic
content of the TEMPs can be determined by papain digestion
during manufacture using a closed culture system.
of the tissue constructs overnight at 65°C. Total sulfated
9. Packaging glycosaminoglycan content can be determined using a 1,
9-dimethylmethylene blue (DMMB) assay and reported nor-
9.1 The product shall be packaged so that it can be stored
malizedtowetordryweightofthetissue(9).Theassayshould
and transported to the clinical site, while remaining sterile/
be performed at a pH of 1.5 to avoid interference with
aseptic and functional.
polyanions such as hydroxyproline or RNA (10). Bovine
10. Biochemical Composition and Tests
trachea chondroitin-4-sulfate type A standards are included to
allow calculation of the sGAG content and absorbance should
10.1 Extracellular Matrix Composition—The native menis-
be read within 5 min of DMMB addition at 525 nm. Individual
cus is a fibrocartilaginous matrix composed primarily of
types of glycosaminoglycan can be determined using immu-
collagen, proteoglycans, cells, adhesion glycoproteins (<1%),
nohistochemistry or specific gene expression assays; however,
and elastin (<1%). It is recognized that TEMPs may produce
are not often needed. The proteoglycan profile can be more
ECM that differs in content and distribution relative to the
extensively characterized by extraction of the proteoglycans
native tissue, but nonetheless the produced ECM should
from theTEMPs, proteolytic degradation, and chromatography
function similarly to the native meniscal tissue. Regardless,
or electrophoresis to characterize the sGAG composition in
produced collagen, glycosaminoglycans and cells within
comparison to native meniscus tissue (11).
TEMPs should be quantified with time in vivo or in culture.
The extracellular matrix of TEMPs is often a collagen-based
10.4 DNA—The amount of DNA in meniscal products that
hydrated material also containing proteoglyans, elastin, and
contain live cells should be quantified with time in culture or
other proteins and glycoproteins. These components can be
with time in vivo to determine cellular content or proliferation.
quantified, and usually their amounts are expressed per wet
DNA can be quantified by simple colorimetric biochemical
weight or dry weight. Composition assessments can be rela-
assays such as PicoGreen or Hoechst DNA and normalized to
tively simple (for example, protein content), or can be highly
wet weight or dry weight of the product (12).
specific (quantitation of a specific molecule). In all measure-
10.5 Water Content—The meniscus is ~72% water. The
ments of TEMP composition, comparison to native meniscus
percent water content of TEMPs can be determined by mea-
tissue composition is necessary.
suring the wet weight of the constructs followed by lyophiliza-
10.2 Collagen (by types)—The meniscus is primarily com- tion and measurement of the dry weight. Techniques as
posed of collagen (~22% of the wet weight), with type I, II, III, described in Test Method D570 can also be used.
F3223 − 17
10.6 Metabolic Activity—Metabolic activity of TEMPs that (v)functionalperformanceofthestructurewithinthejoint,and
contain live cells can be assessed by reference to techniques (vi) an ability to withstand physiological hoop stresses.
outlined in Guide F2739. Tests include an assessment of
11.3 Tests should be conducted on the terminally sterilized
mitochondrial dehydrogenase activity, which is a measure of
(or aseptic) product, and should capture the time zero proper-
cell proliferation or viability using the BioVision Quick Cell
ties as well as the change in those properties with time. The
Proliferation Assay Kit, which measures the cleavage of
change of properties with time can be captured either by
2-(4-Iodophenyl)-3-(4-nitrophenyl)-5-(2,4-disulfophenyl)-2H-
mechanically testing samples after in vivo implantation, or
tetrazolium monosodium salt (WST-1) (13). Metabolic activity
after artificial ageing. In the case of degradable products,
of cells within TEMPs can also be determined throughout in
mechanical tests should capture the change in mechanical
vitro culture using colorimetric assays such as AlamarBlue or
properties as a function of rate of degradation. In the case of
MTT. It is important that proper controls are always run with
non-degradable materials mechanical tests should capture the
these assays to account for variability due to color. Further
characteristics of the construct to handle both static and cyclic,
these assays should be used to measure metabolic activity and
fatigue-type loads.
are only a baseline of viability. Live-dead assays or DNA
quantification should be performed for more accurate analysis
11.4 Tensile Properties—In defining the test setup, the
of viability prior to implantation.
following should be reported: method of gripping the speci-
10.7 Growth Factors—Growth factors have been applied to
mens ends, specimen geometry, method of measuring cross-
TEMPs to enhance proliferation, migration, matrix production,
sectional area and displacement, loading rates and/or displace-
and phenotype maintenance or differentiation, the most com-
ment rates used, environmental conditions, and, in the case of
mon of which include transforming growth factor beta-1 and
an anisotropic product specimen, orientation (circumferential,
beta-3 (TGF-β1 and TGF-β3), basic fibroblast growth factor
radial, or axial). Examples of tensile test methodology using
(b-FGF), platelet derived growth factor (PDGF)-AB, insulin-
dumbbell-shaped meniscal tissue explants are available in (14
like growth factor (IGF)-1), epidermal growth factor (EGF),
and 15). An example of tensile test methodology as applied to
and hepatocyte growth factor (HGF). The concentration of
strips of scaffolds for meniscal repair are available in (16).
growth factor used can have significant effects on desired
Depending on the test employed, the following results can be
cellular responses and cytotoxicity, thus dose/concentration
reported: stress-strain plot, modulus, yield and failure stress,
should always be reported. Growth factors that are secreted
and yield and failure strain, and degree of anisotropy. The
from TEMPs can be detected by Western blot and quantified
meniscus has an anisotropic and inhomogeneous collagenous
using enzyme linked immunosorbent assays (ELISAs) specific
structure, which results in anisotropic and inhomogeneous
for the growth factors of interest.
properties (17); a comparison to those properties should be
made.
11. Mechanical Properties and Tests
11.1 The high load environment of the knee joint combined
11.5 Compressive Properties—In defining the test setup, the
with its exposure to millions of loading cycles per year places
following should be reported: specimen orientation
importance on assessing the response of products for meniscal
(circumferential, radial, or axial), boundary conditions (con-
augmentation, repair, or replacement to physiologically rel-
fined or unconfined), loading platen configuration, specimen
evant loads. In designing such tests, it should be recognized
geometry, method of measuring displacement, loading rates
that the force magnitudes experienced by a product inserted
and/or displacement rates used, and environmental conditions.
into a meniscal defect will be dependent on the intended
Examples of compression tests on the native meniscus using
compartmentforimplantation,thelocationwithinthecompart-
indentationtestingtechniquesarefoundin(14, 18, 19,and 20).
ment where the product is positioned, and its method of
Examples of compression tests on the native meniscus using
fixation to the host tissue. As such, the mechanical tests
confined compression techniques are found in (15). Examples
conducted on the product should be dictated by their intended
of compression tests on the native meniscus using unconfined
function within the joint and the expected duration for which
compression techniques are found in (21 and 22). Depending
that function must be maintained.
on the test employed, the following results can be reported:
11.2 A broad range of tissue mechanical properties for the
stress-strain plot, modulus, permeability, maximum stress, and
normal ‘uninjured’ human meniscus have been reported in
maximum strain. Depending on the product and its intended
literature. The effect of property variation on mechanical
function, permeability, aggregate modulus, and dynamic
function of the meniscus as a structure is as yet unclear; thus
modulus should be reported.
there are no current guidelines as to the range of properties that
11.6 Viscoelastic Characteristics—The viscoelastic charac-
products intended for meniscal repair must exhibit in order to
teristics of the material should be reported through an analysis
mechanicallyfunctioninthejoint.Nonetheless,toenableafull
of the creep, stress-relaxation, or dynamic response of the
characterization of the material and structural properties of a
scaffold or implant. Such testing can be conducted using
product intended for meniscal repair, augmentation, or
indenters (23), under confined compression conditions (24). In
replacement, mechanical tests should enable the following
features to be quantified: (i) material properties in tension and describing the test setup, the following should be reported:
specimen orientation (circumferential, radial, or ax
...