Contains Nonbinding Recommendations  
 
Facet Screw  Systems   Performance  
Criteria for Safety  and Performance  
Based Pathway  
 
Guidance  for  Industry and  
Food and Drug Administration  Staff   
 
Document issued on April 13, 2022.  
 
The draft of this document was issued on August 30, 2021.  
 
 
 
 
For questions  about  this document,  contact  OHT6: Office  of Orthopedic Devices/DHT6B: 
Division of  Spinal Devices at 301-796-5650.  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
U.S.Department of Health and Human  Services  
Food and Drug Administration  
Center for  Devices and Radiological Health  
  Contains Nonbinding Recommendations  
 
Preface  
 
Public Comment  
 
You may submit  electronic comments and suggestions at any time for Agency consideration to 
https://www.regulations.gov. Submit written comments  to  the Dockets Management  Staff, Food 
and Drug Administration, 5630 Fishers Lane,  Room  1061, (HFA-305), Rockville, MD  20852. 
Identify all comments with the  docket  number  FDA-2021-D-0604. Comments may not be acted 
upon by the  Agency until the document is next revised or updated.  
 
Additional Copies  
 
Additional copies are available from the Internet. You may also send an email request to CDRH-
Guidance@fda.hhs.gov  to receive a copy of the guidance.  Please include  the document number  
21001  and complete title of the guidance in the request.  
 
    Contains Nonbinding Recommendations  
 
Facet Screw  Systems   Performance  
Criteria for Safety  and Performance  
Based Pathway  
 
Guidance  for  Industry and  
Food and Drug Administration  Staff  
 
This guidance represents the current thinking of the Food and Drug Administration  (FDA  or  
Agency) on this topic.  It does  not  establish  any rights for any person and  is not binding on  
FDA or the  public.  You can use an alternative  approach if  it  satisfies the requirements of the 
applicable statutes and regulations.   To discuss  an alternative approach, contact  the FDA staff  
or Office responsible for  this guidance  as listed on the title  page.  
 
I.   Introduction  
This guidance provides  performance criteria for facet screw systems  in support of  the  Safety and 
Performance Based Pathway.1  Under this  framework, submitters  (you)  planning to submit  a  
510(k) using the  Safety and Performance Based Pathway  for facet screw systems  will have the  
option to use the performance criteria proposed in this guidance  to support substantial  
equivalence, rather than  a  direct  comparison  of  the performance of the subject device to that of a 
predicate device.   
 
For the current edition of the FDA-recognized consensus  standard(s) referenced in this  
document, see  the  FDA Recognized  Consensus Standards Database.2  For more information  
regarding use of consensus standards in regulatory submissions, please  refer to the  FDA 
guidance titled Appropriate Use of Voluntary Consensus Standards in Premarket Submissions  
for Medical  Devices.3    
 
The contents of this document do not have the force and effect of  law and are not  meant to bind 
the public in any way, unless specifically incorporated into a  contract. This document is intended 
only to provide clarity to the public regarding existing requirements under the law. FDA  
guidance documents, including this guidance, should be viewed only as recommendations,  unless 
 
1  Available  at  https://www.fda.gov/regulatory-information/search-fda-guidance-documents/safety-and-performance-
based-pathway 
2  Available  at  https://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfStandards/search.cfm   
3  Available  at  https://www.fda.gov/regulatory-information/search-fda-guidance-documents/appropriate-use-
voluntary-consensus-standards-premarket-submissions-medical-devices  
1  
  Contains Nonbinding Recommendations  
 
specific  regulatory or statutory requirements  are cited. The use of the word  should  in Agency 
guidance  means that something is suggested or  recommended, but not required.  
   
II.   Scope/Device Description  
The facet screw systems  that are the  subject of this guidance consist of metallic bone screws and  
optional  washer  components. These devices are unclassified and are identified with the  product  
code MRW (system, facet screw spinal device).   
 
Intended Use/Indications for Use:  
The facet screw systems  that fall within the scope of this guidance document are intended for  
bilateral immobilization of facet joints to stabilize the spine as an aid  to fusion. The optional 
washer components are intended for  use with the facet screw to aid in  load distribution  at the 
screw head/bone interface.   
 
Device Design Characteristics:   
The facet screw systems  that  fall within the scope of this guidance document consist of solid or  
cannulated screws with fully or partially threaded screw shafts, and optional washer  components,  
constructed  solely  from the following material in  conformance with the  associated FDA-
recognized consensus standard:  
   ASTM F136  Standard Specification for Wrought Titanium-6 Aluminum-4 Vanadium ELI  
(Extra Low Interstitial) Alloy  for Surgical Implant Applications (UNS R56401)   
 
A dimensional comparison of the subject device  should be performed, and the dimensions should 
fall within the dimensional ranges listed in Table 1. Washer  components  should have  an inner  
diameter that is larger than the thread diameter (major diameter) of the compatible screw and less  
than the diameter of  the screw head.   
 
Note: Based on review of historical submissions,  screws below 4.5 mm in diameter  and screws 
4.5 mm and above were  often indicated for different anatomical regions and have different  
design characteristics and different performance characteristics. Therefore, screw design  
characteristics and performance criteria are stratified in  this document based on these  diameter 
ranges.  
 
Table 1   Dimensional ranges  for facet screws*  
 
Facet Screws Parameters   < 4.5  mm  Diameter    4.5  mm Diameter   
 
Nominal Major Diameter   3.5-4.3 mm   4.5-6.0 mm  
Range  
Minimum Total Screw   6.0 mm   15 mm  
Length**   
 
Minimum Threaded Length   6.0 mm   12 mm  
* The  dimensional  ranges  listed were  derived from  historical  data  submitted to  FDA  in 510(k)  submissions  for  
devices  previously  found  substantially  equivalent.  
2  
  Contains Nonbinding Recommendations  
 
**  The maximum  facet  screw  length  reported  in  the historical  data was  60  mm.  However,  maximum  screw  
length  can  be  justified based on  the  anatomic  region into which the  subject  facet  screws  are  intended to be  
implanted.  
  
Facet screw  systems that fall within  the following categories are outside the scope  of this  
guidance  for the Safety and Performance Based Pathway:  
   Combination products  
   Resorbable devices  
   Device with coatings  
   Additively manufactured devices  
   Devices that  utilize surgical techniques or associated instruments outside the standard  of  
care  
   Devices with  complex geometries, or  unique  technological characteristics (e.g., unique  
screw thread, modularity, fenestrations)   
   Devices sterilized using  novel sterilization  methods as described in FDAs guidance 
Submission  and Review of Sterility Information  in Premarket Notification  (510(k)) 
Submissions for Devices Labeled as Sterile.4  
 
FDA may determine, on a case-by-case basis, that additional data are necessary  to evaluate 
whether the device is appropriate for the Safety and Performance Based Pathway. In situations  
where you  determine  that additional testing outside of those  identified  in this guidance are 
necessary to make a determination  regarding eligibility into the Safety  and Performance Based  
Pathway, we  would encourage sponsors to submit a Pre-Submission5  to engage in discussion 
with FDA prior to submission of  the  510(k).  
 
III.   Testing Performance Criteria  
If your device is appropriate for submission through  the Safety and Performance Based Pathway,  
and you choose to use  that option, we  do not  expect you  to provide  direct comparison testing 
against a legally  marketed  predicate to demonstrate substantially equivalent performance 
characteristics. To ensure that  the performance criteria outlined in this guidance remain  
contemporary and take into account  relevant data from  recent clearances, FDA recommends that  
you provide  a results summary for  all tests  evaluated in addition to the other submission 
information  (e.g., Declaration of Conformity  (DoC)) recommended below  for each test or 
evaluation. Consistent with FDA policy  for all 510(k) submissions,  for all 510(k) submissions  
under the Safety  and Performance Based Pathway, FDA may request  and review underlying data  
demonstrating that a new device meets the FDA-identified performance  criteria and testing  
methodology, as necessary. Unless otherwise identified in  the  submission  information sections  
below, test information  such as results summary,  test protocols, or complete test reports should  
be submitted as part of the 510(k) as described in  FDAs  guidance:  Safety  and Performance 
 
4  Available  at  https://www.fda.gov/regulatory-information/search-fda-guidance-documents/submission-and-review-
sterility-information-premarket-notification-510k-submissions-devices-labeled 
5  Available  at  https://www.fda.gov/regulatory-information/search-fda-guidance-documents/requests-feedback-and-
meetings-medical-device-submissions-q-submission-program  
3  
  Contains Nonbinding Recommendations  
 
Based Pathway.6  For additional information regarding the submission of non-clinical bench 
testing information, please see FDAs guidance Recommended Content and Format of Non-
Clinical Bench Performance Testing  Information  in Premarket Submissions.7  
 
Mechanical Testing  
To assess mechanical strength of  the worst-case facet screw(s) in the system, static cantilever 
bending testing should be performed on your final, finished device  in conformance with the FDA  
currently-recognized version of ASTM F2193  Standard Specifications  and Test Methods for  
Components Used in the  Surgical Fixation of  the  Spinal Skeletal System-Annex 4:  Test Method 
for Measuring the static and fatigue  bending strength of metallic spinal screws. To assess screw  
fixation, axial pullout strength should be  evaluated using the  engineering analysis method 
described below.8  Mechanical  testing and engineering analyses should be  performed  on  devices 
that represent the  worst-case (e.g., most  likely to loosen or fail). You should also  provide a  
rationale identifying how you identified the worst-case design  for each test/evaluation. All 
mechanical  testing should be performed on the  final, finished  versions of the devices unless 
certain processes (e.g., sterilization)  can be rationalized to have no impact on the  mechanical  
strength of  the device.  Acceptance criteria are listed below for each test.  
 
For  the  mechanical test  below, you should provide a report as specified in the relevant reporting 
section of ASTM F2193, in addition to a Declaration of Conformity (DoC) to  the consensus 
standard.  Any protocol  deviations should be thoroughly described and justified; however, note  
that certain  protocol deviations may  invalidate  comparison to the performance criteria listed  
below, resulting in the need for submission of a Traditional, Special, or  Abbreviated 510(k), as  
appropriate.  
 
1.   Test name:  Static Cantilever Bending  
Methodology:  FDA-recognized  version of  ASTM F2193 Standard Specifications and 
Test Methods for Components Used in the Surgical Fixation of the Spinal Skeletal  
System-Annex 4: Test  Method for  Measuring the static and fatigue bending strength of  
metallic spinal screws  
Performance Criteria:   
 
6  Available  at  https://www.fda.gov/regulatory-information/search-fda-guidance-documents/safety-and-performance-
based-pathway 
7  Available  at  https://www.fda.gov/regulatory-information/search-fda-guidance-documents/recommended-content-
and-format-non-clinical-bench-performance-testing-information-premarket 
8  It  should  be  noted that  although ASTM  F2193 is  FDA-recognized  in full,  FDA  believes  that  for  the  purposes  of  the  
Safety  and  Performance Based  Pathway,  the  testing,  methods  and  criteria  identified  in  this  section  on  mechanical  
bench testing represent  the  least  burdensome  approach to  demonstrating substantial  equivalence  for  this  pathway,  
although  alternative  or  additional  methods  or  acceptance  criteria  are  identified in the  recognized consensus  standard 
for some  tests.   
4  
  Contains Nonbinding Recommendations  
 
 
Table 2   Static cantilever bending  acceptance criteria for facet screw  systems  
 
Test Parameter   <  4.5 mm diameter    4.5  mm diameter  
(Cervical)   (Lower  
Thoracic/Lumbar)  
 
Static Cantilever  
Bending Yield  2.6   3.7  
Moment  (Nm)  
 
 
Performance Criteria Source:  Criteria are based on aggregated mechanical testing data 
submitted to FDA in 510(k) submissions for facet  screw systems previously found to be  
substantially equivalent.  It should be  noted that the values  in the table above were  
rounded to be the most inclusive and accurate based on the final data.  
Additional Considerations: As specified in ASTM F2193, a minimum of five samples  
should be tested. In order to be considered a successful result, either: (1) all samples  
should meet  or exceed  the acceptance criteria listed above, or (2) the average of all  
samples should meet or  exceed the criteria above and the standard deviation should be   
10% of the calculated average.   
Submission Information: Results summary and DoC  
 
2.   Test name:  Axial Pullout Strength   
Methodology:  An engineering  analysis is recommended to  assess axial pullout strength  
using the  equation described by Chapman et al., 1996.9  Note that for this analysis  to be  
appropriate,  the instrumentation identified in the associated surgical technique manual 
should allow for close to idealized  thread engagement.  If  this assumption is not accurate 
for your scenario,  then the identified engineering analysis may not be appropriate  for the  
assessment  of the proposed device as identified in this guidance.  
 
For all  facet  screw sizes,  extract the relevant  dimensions below (i.e.,  screw major  
diameter,  screw minor diameter,  screw pitch, and axial  thread length). These dimensions  
will be used  to calculate theoretical pullout strengths for the worst-case screws in the 
device system using the  following equation:  
 
                         
 
Fs = predicted shear  faiFFluFFre= f oSSrceAA (N=)   {SSLLDDDDDDDDDDDDTTSSFF} 
S = material ultimate shear stress (MPa)  
A = thread shear area (mm2)  
 
9  Chapman,  J.  R.  (1996).  Factors  Affecting  the  Pullout  Strength of  Cancellous  Bone  Screws.  Journal  of  
Biomechanical Engineering,118(3),  391.  doi:10.1115/1.2796022  
 
5  
  Contains Nonbinding Recommendations  
 
L =  axial thread  length  (mm) including only threads that have the nominal major diameter 
where complete purchase is expected (e.g., excluding the screw tip)  of thread engagement  
in material  
Dmajor =  major diameter (mm)  
TSF = Thread Shape Factor (dimensionless) = (0.5 + 0.57735 d/p)  
d = thread depth (mm) = (Dmajor   Dminor)/2  
Dminor =  minor (root) diameter (mm)  
p = thread pitch (mm)  
 
Use a material ultimate shear stress (S) value of  3.395 MPa, which is representative of  
Grade 20 polyurethane foam material (per  FDA currently-recognized version of ASTM  
F1839 Standard Specification for Rigid Polyurethane Foam for Use as a Standard 
Material  for Testing Orthopaedic Devices and Instruments). The resulting theoretical  
pullout strength value obtained for  the device  should be equivalent or greater  to the  
following values depending on the nominal major  diameter of the worst-case screws. A 
justification should be provided to support why the evaluated facet screws  selected are  
worst-case. Axial pullout performance is heavily influenced by amount of interface. 
Factors such as decreasing outer diameter  and decreasing  axial thread  length may help  
identify  the worst-case.    
 
Dimensions used for calculations should be clearly listed for each theoretical outcome.  
Dimensional values used in this  calculation should be consistent with the  values  listed on 
the screw engineering drawings.  
 
Performance Criteria:  The  resulting theoretical pullout strength values  obtained for  
your worst-case devices should meet  or exceed  to the values listed in Table 3 depending  
on the major diameter of the screw being evaluated.  
 
  Table  3    Axial pullout strength  acceptance criteria for  facet screw  systems  
 
Nominal Major  Diameter   Theoretical Pullout Strength  
(mm)   in Grade 20 Foam  (N)  
< 4.5  mm   190  
 4.5  mm   390  
 
 
Performance Criteria Source:  Criteria are based on aggregated mechanical testing data 
and device description  information  submitted to FDA in 510(k) submissions for facet 
screws previously found to be substantial equivalent.  
Submission Information:  Results summary and engineering analysis  
 
Sterilization (devices labeled as sterile) and Reprocessing (end-user  sterilized) Validation  
 
3.   Test name:  Sterilization (devices labeled as sterile) and Reprocessing  (end-user   
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  Contains Nonbinding Recommendations  
 
sterilized)   
Methodology:  FDA currently-recognized versions of the  following consensus standards  
(as applicable):  
   International Organization for Standardization  (ISO) 17665-1 Sterilization of  
health care products    Moist heat   Part 1: Requirements for the development,  
validation, and routine  control of  a sterilization process for  medical devices   
   ISO 11135-1 Sterilization of health care products    Ethylene oxide- Part 1:  
Requirements for development, validation, and routine control of a sterilization  
process for medical devices  
   ISO 11137-1 Sterilization of health care productsRadiationPart 1:   
Requirements for development, validation, and routine control of a sterilization 
process for medical devices  
   ISO 11607-1 Packaging for terminally sterilized  medical devices   Part 1:   
Requirements for materials, sterile barrier systems and packaging systems  
   ISO 11607-2 Packaging for terminally sterilized  medical devices   Part 2:  
Validation requirements for forming, sealing and assembly processes  
Performance Criteria:  Validation testing should demonstrate the cleanliness and    
sterility of,  or the ability to  clean and sterilize to  a sterility assurance level of 10-6, the  
device and device-specific instruments.   
Performance Criteria Source:  FDA guidance:  
   Submission  and Review of Sterility Information  in Premarket Notification   
(510(k)) Submissions for Devices Labeled as Sterile10  
   Reprocessing Medical Devices in Health Care Settings: Validation Methods and   
Labeling11   
Submission Information: You should provide a  description of the packaging (sterile  
barrier system) and how  it will maintain the devices sterility,  and a description of the  
package test methods, but not package test data.  With  respect to the Established  
Sterilization Method, whether  using an Established Category A  or Established Category 
B sterilization method, you should provide  the information in Section V.A. of the FDA  
guidance  Submission and Review of Sterility Information in  Premarket Notification  
(510(k)) Submissions for Devices Labeled as Sterile; generally, the validation data itself 
is not needed to demonstrate substantial equivalence.   
 
Biocompatibility Evaluation:  
 
To identify the biocompatibility endpoints to include as part  of your biocompatibility evaluation 
you should use Attachment A of the  FDA  guidance  Use of International Standard ISO 10993-1, 
Biological evaluation of medical devices   Part 1: Evaluation and testing within a risk  
management process,12  referred to  in the rest of this document as the FDA  Biocompatibility  
 
10  Available  at  https://www.fda.gov/regulatory-information/search-fda-guidance-documents/submission-and-review-
sterility-information-premarket-notification-510k-submissions-devices-labeled 
11  Available  at  https://www.fda.gov/regulatory-information/search-fda-guidance-documents/reprocessing-medical-
devices-health-care-settings-validation-methods-and-labeling 
12  Available  at  https://www.fda.gov/regulatory-information/search-fda-guidance-documents/use-international-
standard-iso-10993-1-biological-evaluation-medical-devices-part-1-evaluation-and  
 
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Guidance for brevity.  FDA considers the  devices covered by this guidance  to  be categorized as 
Implanted  Devices in contact with tissue/bone with a permanent  contact duration of > 30 days  
and you should assess the endpoints  below per Attachment A of the  FDA  Biocompatibility 
Guidance.  
   Cytotoxicity  
   Sensitization  
   Irritation or Intracutaneous Reactivity  
   Acute Systemic Toxicity  
   Material-Mediated Pyrogenicity  
   Sub-acute/Sub-chronic Toxicity  
   Genotoxicity  
   Implantation   
   Chronic Toxicity  
   Carcinogenicity  
 
Rationale in Lieu of Testing: If the subject device is manufactured from the identical raw  
materials using identical  manufacturing processes as a predicate device with the same type and  
duration of tissue contact, and any changes in geometry are not expected to impact the  biological  
response, this is typically sufficient to establish substantially equivalent biocompatibility if 
documentation such as that outlined in Attachment F of the  FDA  Biocompatibility  Guidance is  
also provided.  
 
Testing: In  rare cases,  if you determined that  testing is needed to address some or all of the 
identified biocompatibility endpoints, FDA recommends  that complete  test reports be provided 
for all tests  performed unless a declaration of conformity without supplemental information  can  
be appropriately provided, as discussed in  Attachment E of the  FDA  Biocompatibility Guidance. 
Any test-specific positive, negative, and/or reagent controls should perform as expected, and 
protocol deviations should be thoroughly described and justified; however, note that certain 
protocol deviations may invalidate  comparison to the performance criteria listed below., 
resulting in the need for  submission of a Traditional, Special, or Abbreviated 510(k).  
 
4.   Test name:  Biocompatibility endpoints (identified from FDA  Biocompatibility   
Guidance)   
Methodology:  FDA currently-recognized versions of biocompatibility consensus   
standards  
Performance Criteria:  All direct  tissue contacting components of the device and device-
specific instruments should  be determined  to have an acceptable biological response.  
Performance Criteria Source:  The  FDA  Biocompatibility Guidance  
Additional Considerations: For  any biocompatibility test samples with an adverse  
biological  response, the  biocompatibility evaluation should explain why the level of  
toxicity seen is acceptable. Some comparison testing against  a legally marketed predicate 
may be necessary (and is considered  acceptable under the Safety and Performance Based  
Pathway) to support such a rationale  as explained  in the  FDA  Biocompatibility Guidance. 
For standard biocompatibility test methods that include comparison device control  
samples, the legally marketed comparison device control samples should  perform as 
expected.  
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Submission Information: Refer to  FDA  Biocompatibility Guidance   
9