ASTM F2706-08(2014)

Standard Test Methods for Occipital-Cervical and Occipital-Cervical-Thoracic Spinal Implant Constructs in a Vertebrectomy Model

SIGNIFICANCE AND USE
5.1 Occipital-cervical and occipital-cervical-thoracic spinal implants are generally composed of several components which, when connected together, form either an occipital-cervical spinal implant assembly or an occipital-cervical-thoracic spinal implant assembly. Occipital-cervical and occipital-cervical-thoracic spinal implant assemblies are designed to provide some stability to the spine during the process of arthrodesis. These test methods outline standard materials and methods for the evaluation of different spinal implant assemblies to facilitate comparisons between different designs.  
5.2 These test methods are used to quantify the static and dynamic mechanical characteristics of different designs of occipital-cervical and occipital-cervical-thoracic spinal implant assemblies. The mechanical tests are conducted in vitro using simplified load schemes and do not attempt to mimic the complex loads of the occipital-cervical and occipital-cervical-thoracic spine.  
5.3 The loads applied to the spinal implant assemblies  in vivo will, in general, differ from the loading configurations used in these test methods. The results obtained here cannot be used directly to predict in vivo performance. The results can be used to compare different component designs in terms of the relative mechanical parameters.  
5.4 Fatigue testing in a simulated body fluid or saline may cause fretting, corrosion, or lubricate the interconnections and thereby affect the relative performance of tested devices. This test should be initially performed dry (ambient room conditions) for consistency. The effect of the environment may be significant. Repeating all or part of these test methods in simulated body fluid, saline (9 g NaCl per 1000 mL water), a saline drip, water, or a lubricant should be considered. The maximum recommended frequency for this type of cyclic testing should be 5 Hz.  
5.5 The location of the longitudinal elements is determined by the intended in vivo location of the...
SCOPE
1.1 These test methods cover the materials and methods for the static and fatigue testing of occipital-cervical and occipital-cervical-thoracic spinal implant assemblies in a vertebrectomy model. The test materials for most combinations of occipital-cervical and occipital-cervical-thoracic spinal implant components can be specific depending on the intended location and intended method of attachment.  
1.2 These test methods are intended to provide a basis for the mechanical comparison among past, present, and future occipital-cervical and occipital-cervical-thoracic spinal implant assemblies. They allow comparison of occipital-cervical and occipital-cervical-thoracic spinal implant constructs with different methods of application to the spine. These test methods are not intended to define levels of performance, since sufficient knowledge is not available to predict the consequences of the use of a particular device.  
1.3 These test methods set out guidelines for load types and methods of applying loads. Methods for three static load types and two fatigue tests for the comparative evaluation of occipital-cervical and occipital-cervical-thoracic spinal implant assemblies are defined.  
1.4 These test methods establish guidelines for measuring displacements, determining the yield load, and evaluating the stiffness and strength of occipital-cervical or occipital-cervical-thoracic spinal implant assemblies.  
1.5 It may not be possible to test some occipital-cervical and some occipital-cervical-thoracic spinal constructs in all test configurations.  
1.6 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.  
1.7 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 ...

General Information

• Status: Historical
• Publication Date: 30-Sep-2014
• ICS: 11.040.40 - Implants for surgery, prosthetics and orthotics
• Technical Committee: F04 - Medical and Surgical Materials and Devices
• Drafting Committee: F04.25 - Spinal Devices

Relations

• Replaces: ASTM F2706-08 - Standard Test Methods for Occipital-Cervical and Occipital-Cervical-Thoracic Spinal Implant Constructs in a Vertebrectomy Model
• Effective Date: 01-Oct-2014
• Replaced By: ASTM F2706-17 - Standard Test Methods for Occipital-Cervical and Occipital-Cervical-Thoracic Spinal Implant Constructs in a Vertebrectomy Model
• Effective Date: 01-Mar-2017
• Referred By: ASTM F3292-19 - Standard Practice for Inspection of Spinal Implants Undergoing Testing
• Effective Date: 01-Oct-2014

Standards Content (Sample)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation: F2706 − 08 (Reapproved 2014)
Standard Test Methods for
Occipital-Cervical and Occipital-Cervical-Thoracic Spinal
Implant Constructs in a Vertebrectomy Model
This standard is issued under the fixed designation F2706; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope responsibility of the user of this standard to establish appro-
priate safety and health practices and determine the applica-
1.1 These test methods cover the materials and methods for
bility of regulatory limitations prior to use.
thestaticandfatiguetestingofoccipital-cervicalandoccipital-
cervical-thoracic spinal implant assemblies in a vertebrectomy
2. Referenced Documents
model. The test materials for most combinations of occipital-
cervical and occipital-cervical-thoracic spinal implant compo-
2.1 ASTM Standards:
nents can be specific depending on the intended location and
E4Practices for Force Verification of Testing Machines
intended method of attachment.
E6Terminology Relating to Methods of Mechanical Testing
E739PracticeforStatisticalAnalysisofLinearorLinearized
1.2 These test methods are intended to provide a basis for
Stress-Life (S-N) and Strain-Life (ε-N) Fatigue Data
the mechanical comparison among past, present, and future
E1823TerminologyRelatingtoFatigueandFractureTesting
occipital-cervical and occipital-cervical-thoracic spinal im-
F1582Terminology Relating to Spinal Implants
plant assemblies. They allow comparison of occipital-cervical
F1717Test Methods for Spinal Implant Constructs in a
and occipital-cervical-thoracic spinal implant constructs with
Vertebrectomy Model
different methods of application to the spine. These test
F2077TestMethodsForIntervertebralBodyFusionDevices
methodsarenotintendedtodefinelevelsofperformance,since
sufficient knowledge is not available to predict the conse-
3. Terminology
quences of the use of a particular device.
3.1 Definitions—For definitions of terms relating to these
1.3 These test methods set out guidelines for load types and
test methods, see Terminologies E6, F1582, and E1823.
methods of applying loads. Methods for three static load types
and two fatigue tests for the comparative evaluation of
3.2 Definitions of Terms Specific to This Standard:
occipital-cervical and occipital-cervical-thoracic spinal im-
3.2.1 active length of the longitudinal element, n—the
plant assemblies are defined.
straight line distance between the centers of rotation of the test
blocks.
1.4 These test methods establish guidelines for measuring
displacements, determining the yield load, and evaluating the
3.2.2 block moment arm, n—the perpendicular to the ap-
stiffnessandstrengthofoccipital-cervicaloroccipital-cervical-
pliedloadbetweentheinsertionpointofananchorandtheaxis
thoracic spinal implant assemblies.
of the hinge pin.
1.5 Itmaynotbepossibletotestsomeoccipital-cervicaland
3.2.3 compressive or tensile bending stiffness (N/mm),
some occipital-cervical-thoracic spinal constructs in all test
n—the compressive or tensile bending yield force divided by
configurations.
elastic displacement (see the initial slope of line BC in Fig. 1).
1.6 The values stated in SI units are to be regarded as
3.2.4 compressive or tensile bending ultimate load (N),
standard. No other units of measurement are included in this
n—the maximum compressive or tensile force in the X-Z plane
standard.
applied to an occipital-cervical or occipital-cervical-thoracic
spinalimplantassembly(seetheforceatPointEinFig.1).The
1.7 This standard does not purport to address all of the
ultimate load should be a function of the device and not of the
safety concerns, if any, associated with its use. It is the
load cell or testing machine.
These test methods are under the jurisdiction of ASTM Committee F04 on
Medical and Surgical Materials and Devices and are the direct responsibility of
Subcommittee F04.25 on Spinal Devices. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved Oct. 1, 2014. Published November 2014. Originally contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
approved in 2008. Last previous edition approved in 2008 as F2706-08. DOI: Standards volume information, refer to the standard’s Document Summary page on
10.1520/F2706-08R14. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
F2706 − 08 (2014)
FIG. 1 Typical Load Displacement Curve or Torque Angulation Curve
3.2.5 compressive or tensile bending yield load (N), n—the occipital-cervical-thoracic spinal implant assembly ineffective
compressive or tensile bending force in the X-Z plane neces- or unable to adequately resist load.
sary to produce a permanent deformation equal to 0.020 times
3.2.11 fatigue life, n—the number of loading cycles, N,ofa
the active length of the longitudinal element (see the force at
specified character that the occipital-cervical or occipital-
Point D in Fig. 1).
cervical-thoracic spinal implant assembly sustains before fail-
3.2.6 coordinate system/axes, n—three orthogonal axes are
ure of a specified nature occurs (see Terminology E1823).
defined in Figs. 2 and 3. The anterior-posterior axis is X with
3.2.12 hinge pin, n—the cylindrical rod connecting a test
positive being anterior. The medial-lateral axis is Y with left
blocktoasidesupport.Thesuperiorandinferioraspectsofthe
being positive when viewed posteriorly. The superior-inferior
test construct are each secured with a single 9.6-mm diameter
axis is Z with superior being positive.
pin.
3.2.7 displacement at 2 % offset yield (mm), n—the dis-
3.2.13 insertion point of an anchor, n—the location where
placement of a construct measured via the actuator that
the anchor is attached to the test block. The insertion points
produces a permanent deformation equal to 0.020 times the
shown in Figs. 4-7 are to be adhered to, if possible. In
active length of the longitudinal element (distance OA in Fig.
situations where the design of the occipital-cervical or
1).
occipital-cervical-thoracic spinal implant assembly or the
3.2.8 elasticangulardisplacement(degrees),n—theangular
manufacturer’s surgical instructions for installation dictate
displacement at 2% offset yield (see PointAin Fig. 1) minus
otherwise, the attachment points may deviate from these
the2%offsetangulardisplacement(seePointBinFig.1)(that
dimensions.
is, the distance between Point A and Point B in Fig. 1).
3.2.14 intended method of application, n— occipital-
3.2.9 elastic displacement (mm), n—the displacement at
cervical and occipital-cervical-thoracic spinal implant assem-
2% offset yield (see Point A in Fig. 1) minus the 2% offset
blies contain different types of anchors. Each type of anchor
displacement (see Point B in Fig. 1). (The distance between
has an intended method of application to the spine.
Point A and Point B in Fig. 1.)
3.2.10 failure, n—permanent deformation resulting from 3.2.15 intended occipital-cervical spinal location, n—the
fracture, plastic deformation, or loosening beyond the ultimate anatomicregionofthespineintendedfortheapplicationofthe
displacementorlooseningthatrenderstheoccipital-cervicalor occipital-cervical spinal implant assembly. Spinal implant
F2706 − 08 (2014)
FIG. 2 A Standard Bilateral Construct Containing Screw, Rod and Screw
assemblies are developed for specific spinal locations such as The longitudinal direction is generally in the superior-inferior
the posterior occipital-cervical spine. direction and therefore, generally parallel to the Z-axis.
3.2.16 intended occipital-cervical-thoracic spinal location, 3.2.19 maximum runout load, n—the maximum load that
n—the anatomic region of the spine intended for the applica- can be applied to an occipital-cervical or occipital-cervical-
tion of the occipital-cervical-thoracic spinal implant assembly. thoracic spinal implant assembly where all of the tested
Spinal implant assemblies are developed for specific spinal constructs have withstood 5000000 cycles without a failure.
locations such as the posterior occipital-cervical-thoracic
3.2.20 occipital-cervical spinal implant assembly, n—a
spine.
complete occipital-cervical spinal implant configuration as
3.2.17 longitudinal axis offset (mm), n— distance in the X intended for surgical use. An occipital-cervical spinal implant
direction between the centerline of the longitudinal element assembly will contain anchors, interconnections, and longitu-
and the insertion point of the anchors on the polyacetal test dinal elements and may contain transverse elements (see Figs.
block. 2-7).
3.2.18 longitudinal direction, n—the initial spatial orienta- 3.2.21 occipital-cervical spinal implant construct, n—a
tion parallel to the longitudinal element of the occipital- completeoccipital-cervicalspinalimplantassemblyattachedto
cervical or occipital-cervical-thoracic spinal implant assembly. the appropriate test blocks.
F2706 − 08 (2014)
FIG. 3 A Bilateral Hook, Rod, Screw, and Transverse Element Construct
3.2.22 occipital-cervical-thoracic spinal implant assembly, theinitialunloadedconditionasmeasuredviatheactuatorafter
n—a complete occipital-cervical-thoracic spinal implant con-
the applied load, moment, or torque has been removed.
figuration as intended for surgical use. An occipital-cervical-
3.2.27 test block, n—thecomponentofthetestapparatusfor
thoracic spinal implant assembly will contain anchors,
mounting the occipital-cervical or occipital-cervical-thoracic
interconnections, and longitudinal elements and may contain
spinal implant assembly. A specific design of test block is
transverse elements (see Figs. 2-7).
requiredforeachintendedspinallocationandintendedmethod
3.2.23 occipital-cervical-thoracic spinal implant construct,
ofapplication.Figs.5-7describetherecommendeddesignsfor
n—a complete occipital-cervical-thoracic spinal implant as-
the test blocks; however, alternate designs can be used as long
sembly attached to the appropriate test blocks.
as equivalent performance is demonstrated.
3.2.24 offset angular displacement at 2 degrees offset, n—a
3.2.28 test block load point, n—the location on the test
permanentangulardisplacementinthe X-Yplanemeasuredvia
block at which the resultant load is transmitted from the test
the actuator equal to 0.020 times the torsional aspect ratio (for
apparatus.
example: 1.95° for 1.70 × 0.02 × 180°/pi) (see Point B in Fig.
1).
3.2.29 tightening torque, n—the specified torque that is
3.2.25 offset displacement (mm), n—a permanent deforma-
applied to the various threaded fasteners of the occipital-
tion measured via the actuator equal to 0.020 times the active
cervical or occipital-cervical-thoracic spinal implant assembly.
lengthofthelongitudinalelement(forexample:1.52mmfora
3.2.30 torsional aspect ratio, n—the active length of the
76 mm active length of the longitudinal element) (see Point B
longitudinalelementdividedbythedistancefromthecenterof
in Fig. 1).
rotationtotheinsertionpointofananchoronthecervicalblock
3.2.26 permanent deformation, n—the displacement (mm)
(for example: in Fig. 2, 1.70 for a 76-mm active length, X=40
or angular displacement (degree) of the occipital-cervical or
mm and Y = 40/2 mm).
occipital-cervical-thoracic spinal implant construct relative to
F2706 − 08 (2014)
FIG. 4 Occipital-Cervical Bilateral Construct Test Setup for Occipital Screws or Bolts
L L
3.2.34 yield displacement (distance OA—Fig. 6), n—the
A 5 5 (1)
2 2 1/2
D x 1y displacement (mm) or angular displacement (deg) when an
~ !
assembly has a permanent deformation equal to the offset
where:
displacement or the offset angular displacement.
L = active length of longitudinal element,
3.2.35 yield torque (N-m), n—the torque in the X-Y plane
D = distance to insertion point,
required to produce a permanent displacement of 0.020 times
x = x distance to insertion point, and
the torsional aspect ratio (the torque at Point D in Fig. 1).
y = y distance to insertion point.
3.2.36 zero displacement intercept (mm), n— the intersec-
3.2.31 torsional stiffness (N-m/degree), n— the yield torque
tion of the straight line section of the load-displacement curve
(N-m) divided by elastic angular displacement (degrees) (the
and the zero load axis (the zero displacement reference Point 0
initial slope of line BC in Fig. 1).
in Fig. 1).
3.2.32 torsional ultimate load (N-m), n— the maximum
torque in the X-Y plane applied to an occipital-cervical or
4. Summary of Test Methods
occipital-cervical-thoracic spinal implant assembly (the torque
4.1 Similar test methods are proposed for the mechanical
at Point E in Fig. 1). The ultimate torque should be a function
evaluation of all occipital-cervical and occipital-cervical-
of the device and not of the load cell or testing machine.
thoracic spinal implant assemblies (see Fig. 4).
3.2.33 ultimate displacement (mm), n—the displacement
associated with the ultimate load, ultimate bending load or 4.2 A vertebrectomy model is used for the evaluation of
ultimate torque (the displacement at Point F in Fig. 1). both occipital-cervical and occipital-cervical-thoracic systems.
F2706 − 08 (2014)
FIG. 5 Occipital Bilateral Polyacetal Block for Occipital Screws or Bolts
The spinal hardware is attached at the superior and inferior Occipital-cervical and occipital-cervical-thoracic spinal im-
aspects to polyacetal homopolymer (polyacetal) test blocks
plant assemblies contain different types of anchors. Each type
separated by a large gap.The polyacetal homopolymer used to
of anchor has an intended method of application to the spine.
manufacture the test blocks should have a tensile breaking
For example, one assembly may include screws and rods (see
strengthnolessthan61MPa.Theuseofpolyacetaltestblocks
Fig. 2), while another assembly may contain screws, hooks,
(see Figs. 5-8) eliminates the effects of the variability of bone
rods, and transverse elements (see Fig. 3). The block moment
geometry and material properties associated with cadaveric
arm of a test configuration will be independent of the intended
testing.Alternate designs of test blocks may be used as long as
method of application of a spinal implant assembly, thereby
equivalent performance is demonstrated.
allowing the user to compare devices for a given load.
4.3 Threestaticmechanicaltestsandtwodynamictes
...

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: F2706 − 08 F2706 − 08 (Reapproved 2014)
Standard Test Methods for
Occipital-Cervical and Occipital-Cervical-Thoracic Spinal
Implant Constructs in a Vertebrectomy Model
This standard is issued under the fixed designation F2706; 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
1.1 These test methods cover the materials and methods for the static and fatigue testing of occipital-cervical and
occipital-cervical-thoracic spinal implant assemblies in a vertebrectomy model. The test materials for most combinations of
occipital-cervical and occipital-cervical-thoracic spinal implant components can be specific depending on the intended location and
intended method of attachment.
1.2 These test methods are intended to provide a basis for the mechanical comparison among past, present, and future
occipital-cervical and occipital-cervical-thoracic spinal implant assemblies. They allow comparison of occipital-cervical and
occipital-cervical-thoracic spinal implant constructs with different methods of application to the spine. These test methods are not
intended to define levels of performance, since sufficient knowledge is not available to predict the consequences of the use of a
particular device.
1.3 These test methods set out guidelines for load types and methods of applying loads. Methods for three static load types and
two fatigue tests for the comparative evaluation of occipital-cervical and occipital-cervical-thoracic spinal implant assemblies are
defined.
1.4 These test methods establish guidelines for measuring displacements, determining the yield load, and evaluating the stiffness
and strength of occipital-cervical or occipital-cervical-thoracic spinal implant assemblies.
1.5 It may not be possible to test some occipital-cervical and some occipital-cervical-thoracic spinal constructs in all test
configurations.
1.6 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.7 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.
2. Referenced Documents
2.1 ASTM Standards:
E4 Practices for Force Verification of Testing Machines
E6 Terminology Relating to Methods of Mechanical Testing
E739 Practice for Statistical Analysis of Linear or Linearized Stress-Life (S-N) and Strain-Life (ε-N) Fatigue Data
E1823 Terminology Relating to Fatigue and Fracture Testing
F1582 Terminology Relating to Spinal Implants
F1717 Test Methods for Spinal Implant Constructs in a Vertebrectomy Model
F2077 Test Methods For Intervertebral Body Fusion Devices
3. Terminology
3.1 Definitions—For definitions of terms relating to these test methods, see Terminologies E6, F1582, and E1823.
3.2 Definitions of Terms Specific to This Standard:
These test methods are under the jurisdiction of ASTM Committee F04 on Medical and Surgical Materials and Devices and are the direct responsibility of Subcommittee
F04.25 on Spinal Devices.
Current edition approved Aug. 1, 2008Oct. 1, 2014. Published September 2008November 2014. Originally approved in 2008. Last previous edition approved in 2008 as
F2706-08. DOI: 10.1520/F2706-08.10.1520/F2706-08R14.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
F2706 − 08 (2014)
3.2.1 active length of the longitudinal element, n—the straight line distance between the centers of rotation of the test blocks.
3.2.2 block moment arm, n—the perpendicular to the applied load between the insertion point of an anchor and the axis of the
hinge pin.
3.2.3 compressive or tensile bending stiffness (N/mm), n—the compressive or tensile bending yield force divided by elastic
displacement (see the initial slope of line BC in Fig. 1).
3.2.4 compressive or tensile bending ultimate load (N), n—the maximum compressive or tensile force in the X-Z plane applied
to an occipital-cervical or occipital-cervical-thoracic spinal implant assembly (see the force at Point E in Fig. 1). The ultimate load
should be a function of the device and not of the load cell or testing machine.
3.2.5 compressive or tensile bending yield load (N), n—the compressive or tensile bending force in the X-Z plane necessary to
produce a permanent deformation equal to 0.020 times the active length of the longitudinal element (see the force at Point D in
Fig. 1).
3.2.6 coordinate system/axes, n—three orthogonal axes are defined in Figs. 2 and 3. The anterior-posterior axis is X with positive
being anterior. The medial-lateral axis is Y with left being positive when viewed posteriorly. The superior-inferior axis is Z with
superior being positive.
3.2.7 displacement at 2 % offset yield (mm), n—the displacement of a construct measured via the actuator that produces a
permanent deformation equal to 0.020 times the active length of the longitudinal element (distance OA in Fig. 1).
3.2.8 elastic angular displacement (degrees), n—the angular displacement at 2 % offset yield (see Point A in Fig. 1) minus the
2 % offset angular displacement (see Point B in Fig. 1) (that is, the distance between Point A and Point B in Fig. 1).
3.2.9 elastic displacement (mm), n—the displacement at 2 % offset yield (see Point A in Fig. 1) minus the 2 % offset
displacement (see Point B in Fig. 1). (The distance between Point A and Point B in Fig. 1.)
3.2.10 failure, n—permanent deformation resulting from fracture, plastic deformation, or loosening beyond the ultimate
displacement or loosening that renders the occipital-cervical or occipital-cervical-thoracic spinal implant assembly ineffective or
unable to adequately resist load.
3.2.11 fatigue life, n—the number of loading cycles, N, of a specified character that the occipital-cervical or occipital-cervical-
thoracic spinal implant assembly sustains before failure of a specified nature occurs (see Terminology E1823).
FIG. 1 Typical Load Displacement Curve or Torque Angulation Curve
F2706 − 08 (2014)
FIG. 2 A Standard Bilateral Construct Containing Screw, Rod and Screw
3.2.12 hinge pin, n—the cylindrical rod connecting a test block to a side support. The superior and inferior aspects of the test
construct are each secured with a single 9.6-mm diameter pin.
3.2.13 insertion point of an anchor, n—the location where the anchor is attached to the test block. The insertion points shown
in Figs. 4-7 are to be adhered to, if possible. In situations where the design of the occipital-cervical or occipital-cervical-thoracic
spinal implant assembly or the manufacturer’s surgical instructions for installation dictate otherwise, the attachment points may
deviate from these dimensions.
3.2.14 intended method of application, n— occipital-cervical and occipital-cervical-thoracic spinal implant assemblies contain
different types of anchors. Each type of anchor has an intended method of application to the spine.
3.2.15 intended occipital-cervical spinal location, n—the anatomic region of the spine intended for the application of the
occipital-cervical spinal implant assembly. Spinal implant assemblies are developed for specific spinal locations such as the
posterior occipital-cervical spine.
3.2.16 intended occipital-cervical-thoracic spinal location, n—the anatomic region of the spine intended for the application of
the occipital-cervical-thoracic spinal implant assembly. Spinal implant assemblies are developed for specific spinal locations such
as the posterior occipital-cervical-thoracic spine.
3.2.17 longitudinal axis offset (mm), n— distance in the X direction between the centerline of the longitudinal element and the
insertion point of the anchors on the polyacetal test block.
F2706 − 08 (2014)
FIG. 3 A Bilateral Hook, Rod, Screw, and Transverse Element Construct
3.2.18 longitudinal direction, n—the initial spatial orientation parallel to the longitudinal element of the occipital-cervical or
occipital-cervical-thoracic spinal implant assembly. The longitudinal direction is generally in the superior-inferior direction and
therefore, generally parallel to the Z-axis.
3.2.19 maximum runout load, n—the maximum load that can be applied to an occipital-cervical or occipital-cervical-thoracic
spinal implant assembly where all of the tested constructs have withstood 5 000 000 cycles without a failure.
3.2.20 occipital-cervical spinal implant assembly, n—a complete occipital-cervical spinal implant configuration as intended for
surgical use. An occipital-cervical spinal implant assembly will contain anchors, interconnections, and longitudinal elements and
may contain transverse elements (see Figs. 2-7).
3.2.21 occipital-cervical spinal implant construct, n—a complete occipital-cervical spinal implant assembly attached to the
appropriate test blocks.
3.2.22 occipital-cervical-thoracic spinal implant assembly, n—a complete occipital-cervical-thoracic spinal implant configu-
ration as intended for surgical use. An occipital-cervical-thoracic spinal implant assembly will contain anchors, interconnections,
and longitudinal elements and may contain transverse elements (see Figs. 2-7).
3.2.23 occipital-cervical-thoracic spinal implant construct, n—a complete occipital-cervical-thoracic spinal implant assembly
attached to the appropriate test blocks.
3.2.24 offset angular displacement at 2 degrees offset, n—a permanent angular displacement in the X-Y plane measured via the
actuator equal to 0.020 times the torsional aspect ratio (for example: 1.95° for 1.70 × 0.02 × 180°/pi) (see Point B in Fig. 1).
3.2.25 offset displacement (mm), n—a permanent deformation measured via the actuator equal to 0.020 times the active length
of the longitudinal element (for example: 1.52 mm for a 76 mm active length of the longitudinal element) (see Point B in Fig. 1).
3.2.26 permanent deformation, n—the displacement (mm) or angular displacement (degree) of the occipital-cervical or
occipital-cervical-thoracic spinal implant construct relative to the initial unloaded condition as measured via the actuator after the
applied load, moment, or torque has been removed.
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FIG. 4 Occipital-Cervical Bilateral Construct Test Setup for Occipital Screws or Bolts
3.2.27 test block, n—the component of the test apparatus for mounting the occipital-cervical or occipital-cervical-thoracic spinal
implant assembly. A specific design of test block is required for each intended spinal location and intended method of application.
Figs. 5-7 describe the recommended designs for the test blocks; however, alternate designs can be used as long as equivalent
performance is demonstrated.
3.2.28 test block load point, n—the location on the test block at which the resultant load is transmitted from the test apparatus.
3.2.29 tightening torque, n—the specified torque that is applied to the various threaded fasteners of the occipital-cervical or
occipital-cervical-thoracic spinal implant assembly.
3.2.30 torsional aspect ratio, n—the active length of the longitudinal element divided by the distance from the center of rotation
to the insertion point of an anchor on the cervical block (for example: in Fig. 2, 1.70 for a 76-mm active length, X = 40 mm and
Y = 40/2 mm).
L L
A 5 5 (1)
2 2 1/2
D ~x 1y !
where:
L = active length of longitudinal element,
D = distance to insertion point,
x = x distance to insertion point, and
y = y distance to insertion point.
F2706 − 08 (2014)
FIG. 5 Occipital Bilateral Polyacetal Block for Occipital Screws or Bolts
3.2.31 torsional stiffness (N-m/degree), n— the yield torque (N-m) divided by elastic angular displacement (degrees) (the initial
slope of line BC in Fig. 1).
3.2.32 torsional ultimate load (N-m), n— the maximum torque in the X-Y plane applied to an occipital-cervical or
occipital-cervical-thoracic spinal implant assembly (the torque at Point E in Fig. 1). The ultimate torque should be a function of
the device and not of the load cell or testing machine.
3.2.33 ultimate displacement (mm), n—the displacement associated with the ultimate load, ultimate bending load or ultimate
torque (the displacement at Point F in Fig. 1).
3.2.34 yield displacement (distance OA—Fig. 6), n—the displacement (mm) or angular displacement (deg) when an assembly
has a permanent deformation equal to the offset displacement or the offset angular displacement.
3.2.35 yield torque (N-m), n—the torque in the X-Y plane required to produce a permanent displacement of 0.020 times the
torsional aspect ratio (the torque at Point D in Fig. 1).
3.2.36 zero displacement intercept (mm), n— the intersection of the straight line section of the load-displacement curve and the
zero load axis (the zero displacement reference Point 0 in Fig. 1).
4. Summary of Test Methods
4.1 Similar test methods are proposed for the mechanical evaluation of all occipital-cervical and occipital-cervical-thoracic
spinal implant assemblies (see Fig. 4).
4.2 A vertebrectomy model is used for the evaluation of both occipital-cervical and occipital-cervical-thoracic systems. The
spinal hardware is attached at the superior and inferior aspects to polyacetal homopolymer (polyacetal) test blocks separated by
a large gap. The polyacetal homopolymer used to manufacture the test blocks should have a tensile breaking strength no less than
61 MPa. The use of polyacetal test blocks (see Figs. 5-8) eliminates the effects of the variability of bone geometry and material
properties associated with cadaveric testing. Alternate designs of test blocks may be used as long as equivalent performance is
demonstrated.
4.3 Three static mechanical tests and two dynamic tests will evaluate the
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