Contains Nonbinding Recommendations 
Orthopedic Non-Spinal Metallic Bone 
Screws and Washers  Performance 
Criteria for Safety and Performance 
Based Pathway 
 
Guidance for Industry and  
Food and Drug Administration Staff  
 
Document issued on December 11, 2020. 
 
The draft of this document was issued on September 20, 2019. 
 
For questions about this document, contact the DHT6C: Division of Stereotaxic, Trauma and 
Restorative 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-2019-D-1652. 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 
19009 and complete title of the guidance in the request. 
 
    Contains Nonbinding Recommendations 
Orthopedic Non-Spinal Metallic Bone 
Screws and Washers  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 non-spinal metallic bone screws and their 
associated washers 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 non-spinal metallic bone screws and washers 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   
 
FDA's guidance documents, including this guidance, do not establish legally enforceable 
responsibilities.  Instead, guidances describe the Agencys current thinking on a topic and should 
be viewed only as recommendations, unless specific regulatory or statutory requirements are 
                                                 
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 
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 devices that are the subject of this guidance are Class II non-spinal metallic bone screws 
and washers regulated under 21 CFR 888.3040, product codes HWC (screw, fixation, bone) and 
HTN (washer, bolt nut), respectively.  
 
Intended Use/Indications for Use: The bone screws that fall within the scope of this guidance 
document are intended for orthopedic non-spinal fracture fixation, osteotomy, or small joint 
fusion or arthrodesis. The washers that fall within the scope of this guidance document are 
intended for use with bone screws only to aid in load distribution at the screw head/bone 
interface. Bone screws or washers that are intended for mandibular, maxillofacial, cranial and 
orbital fracture fixation or for use in the spine are outside the scope of this guidance document. 
Devices intended for use with suture or chord components (e.g., bone anchors, syndesmosis 
tight ropes) as part of an implant system are also outside the scope of this guidance document.  
 
Device Design Characteristics: Bone screws of varying designs (e.g., cancellous screws, 
cortical screws, cannulated screws, fully threaded screws, partially threaded screws) are 
included within the scope of this guidance. Devices that fall within the scope of this guidance 
document consist of bone screws and washers manufactured solely from one of the following 
materials 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)  
  ASTM F1472 Standard Specification for Wrought Titanium -6Aluminum -4Vanadium 
Alloy for Surgical Implant Applications (UNS R56400) . 
  ASTM F1295 Standard Specification for Wrought Titanium-6 Aluminum-7Niobium 
Alloy for Surgical Implant Applications (UNS R56700)  
  ASTM F67 Standard Specification for Unalloyed Titanium, for Surgical Implant 
Applications (UNS R50250, UNS R50400, UNS R50550, UNS R50700)  
  ASTM F138 Standard Specification for Wrought 18 Chromium-14 Nickel-2.5 
Molybdenum Stainless Steel Bar and Wire for Surgical Implants (UNS S31673) 
  ASTM F139-12 Standard Specification for Wrought 18 Chromium-14 Nickel-2.5 
Molybdenum Stainless Steel Sheet and Strip for Surgical Implants (UNS S31673)  
  ASTM F1537 Standard Specification for Wrought Cobalt-28-Chromium-6-Molybdenum 
Alloys for Surgical Implants (UNS R31537, UNS R31538, and UNS R31539) 
 
The inner diameter of a washer should be larger than the compatible screws thread diameter to 
allow screw passage and smaller than the diameter of the compatible screws head to allow for 
cortical load distribution. 
 
Implants with the following features are not eligible for the Safety and Performance Based 
Pathway via this guidance: 
  Combination products 
  Resorbable devices 
2 
  Contains Nonbinding Recommendations 
  Additively manufactured devices 
  Devices that utilize surgical techniques or associated instruments outside the standard of 
care 
  Devices with complex geometries or modularities (e.g., segmented, fenestrated) 
  Devices with other unique technological characteristics (e.g., screw thread designs that 
differ substantially from recognized consensus standards for orthopedic bone screws) 
 
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 determine whether the device is appropriate for the Safety and Performance Based 
Pathway, we encourage you to submit a Pre-Submission4 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, you do not need to provide direct comparison testing against a 
legally marketed predicate device 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)) identified for each test or evaluation below. 
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 Based Pathway.5 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.6 
 
Mechanical Bench Testing 
 
The following mechanical tests should be performed in conformance with the FDA currently-
recognized version of ASTM F543 Standard Specification and Test Methods for Metallic 
Medical Bone Screw. We recommend that you perform all testing on screw designs that 
represent worst-case (e.g., most likely to loosen or fail) final design versions. You should also 
provide a rationale identifying how you identified the worst-case design. Additionally, axial 
                                                 
4 Available at https://www.fda.gov/regulatory-information/search-fda-guidance-documents/requests-feedback-and-
meetings-medical-device-submissions-q-submission-program 
5 Available at https://www.fda.gov/regulatory-information/search-fda-guidance-documents/safety-and-performance-
based-pathway  
6 Available at https://www.fda.gov/regulatory-information/search-fda-guidance-documents/recommended-content-
and-format-non-clinical-bench-performance-testing-information-premarket  
3 
  Contains Nonbinding Recommendations 
pullout strength should be evaluated using an engineering analysis method described below.  
Acceptance criteria are listed below for each test.7 
 
For each mechanical test below, you should provide a report as specified in the relevant reporting 
sections of ASTM F543, 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: Torsional Strength 
Methodology: ASTM F543 Standard Specification and Test Methods for Metallic 
Medical Bone Screws 
Performance Criteria: The worst-case bone screw should be selected for mechanical 
testing:   
 
Nominal Major  Torsional Yield 
Diameter (mm)  Strength (Nm) 
1.5  0.16 
2  0.35 
2.5  0.60 
2.7  1.0 
3  1.0 
3.5  2.1 
4  2.3 
4.5  3.5 
5  4.3 
5.5  5.9 
6  9.5 
 
Note that the acceptance criterion is based on the torsional yield strength, which is a more 
conservative indicator of screw failure strength than the maximum torque strength 
identified in ASTM F543. 
 
Screws should be compared based on nominal diameter. For screws with nominal 
diameters that do not match a value in the table above, a comparison should be made to 
the next highest major diameter listed (e.g., a 4.25 mm screw should utilize the 4.5 mm 
acceptance criteria). 
 
                                                 
7 It should be noted that although ASTM F543 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.  See the supplementary information sheet for ASTM F543 for information on extent of recognition. 
4 
  Contains Nonbinding Recommendations 
Performance Criteria Source: Criteria are based on aggregated mechanical testing data 
submitted to FDA in 510(k) submissions for orthopedic bone screws 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 F543, a minimum of five samples 
should be tested. In addition, analysis of the data available to FDA on existing devices 
has shown that five samples should be adequate based on the mean torsional yield 
strength testing results compared to the criteria for each nominal diameter. To be 
considered a successful result, either: (1) All samples should meet or exceed the 
acceptance criteria listed above, (2) the average of all samples should meet or exceed the 
criteria above and the standard deviation should be  10% of the calculated average, or 
(3) the criteria derived from ASTM E122 Calculating Sample Size to Estimate, With 
Specified Precision, the Average for a  Characteristic of a Lot or Process should be met, 
as suggested in ASTM F543. The table value selected for the acceptance criterion should 
be based on the worst-case screw nominal major diameter.  If the nominal major diameter 
is not listed in this table, the next highest diameter torsional strength value should be used 
as the acceptance criterion.  
Submission Information: Results summary and DoC 
 
2.  Test name: Driving Torque 
Methodology: ASTM F543 Standard Specification and Test Methods for Metallic 
Medical Bone Screws 
Performance Criteria: The screw with the highest risk of failure during insertion (i.e., 
the screw with the lowest safety factor between the insertion torque and the yield torque) 
should be evaluated with Driving Torque testing results. Typically, the worst-case bone 
screw used in torsional strength testing should be tested in insertion and removal testing. 
However, tip geometry and surgical technique should also be considered in establishing 
the worst case. The maximum torque recorded in insertion and removal testing into a 
minimum of 20 pcf bone foam should be 50% of or less than the torsional yield strength 
of the bone screw. Additionally, visual inspection should be performed on screws 
following their removal, and images of the final test samples should be provided to 
demonstrate that the screw threads adequately resist damage, such as disassociation of the 
screw thread from the screw body. 
Performance Criteria Source: Criteria are based on aggregated mechanical testing data 
submitted to FDA in 510(k) submissions for orthopedic bone screws previously found to 
be substantially equivalent. 
Additional Considerations: A minimum of five samples should be tested. In order to be 
considered a successful result, all samples should meet or exceed the acceptance criteria 
listed above. 
Submission Information: Results summary and DoC 
 
3.  Test name: Axial Pullout Strength 
Methodology: An engineering analysis is recommended to assess axial pullout strength 
using the equation described by Chapman et al., 1996.8 Note that for this analysis to be 
                                                 
8 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 
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  Contains Nonbinding Recommendations 
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 screws, 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 
quantify thread engagement and calculate the theoretical pullout strengths for the smallest 
axial thread lengthened screws in the device system using the following equation: 
 
 
 
Fs = predicted shear faiFFluFFre= foSSrceAA (N=)  {SSLLDDDDDDDDDDDDTTSSFF}
S = material ultimate shear stress (MPa) 
A = thread shear area (mm2) 
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 value of 3.395 MPa (representative of 20 pcf bone 
foam) in your analysis. 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 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. 
 
 
 
 
 
 
 
 
 
 
 
6 
  Contains Nonbinding Recommendations 
Performance Criteria:  
 
Nominal Major  Theoretical Pullout 
Diameter (mm)  Strength (N) 
1.5  45.6 
2  50.5 
2.5  55.5 
2.7  79.5 
3  92.0 
3.5  112.5 
4  148.4 
4.5  152.3 
5  230.7 
5.5  336.0 
6  468.6 
6.5  503.5 
 
Screws should be compared based on nominal diameter. For screws with nominal 
diameters that do not match a value in the table above, a comparison should be made to 
the next highest major diameter listed (e.g., a 4.25 mm screw should utilize the 4.5 mm 
acceptance criteria). 
 
Performance Criteria Source: Criteria are based on aggregated mechanical testing data 
and device description information submitted to FDA in 510(k) submissions for 
orthopedic bone screws previously found to be substantially equivalent. 
Submission Information: Results summary and engineering analysis 
 
 
Sterilization (devices labeled as sterile) and Reprocessing (end-user sterilized) Validation 
 
4.  Test name: Sterilization (devices labeled as sterile) and Reprocessing (end-user 
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 products  Radiation  Part 1: 
Requirements for development, validation, and routine control of a sterilization 
process for medical devices 
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  Contains Nonbinding Recommendations 
  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. 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. 
Performance Criteria Source: FDAs guidance: 
  Submission and Review of Sterility Information in Premarket Notification 
(510(k)) Submissions for Devices Labeled as Sterile9 
  Reprocessing Medical Devices in Health Care Settings: Validation Methods and 
Labeling10 
Submission Information: If using an Established Category A sterilization method, you 
should provide the information described 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; 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 Center for Devices and Radiological Healths (CDRH) 
guidance Use of International Standard ISO 10993-1, Biological evaluation of medical devices  
Part 1: Evaluation and testing within a risk management process,11 referred to in the rest of this 
document as the CDRH Biocompatibility 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 CDRH Biocompatibility Guidance. 
  Cytotoxicity 
  Sensitization 
  Irritation or Intracutaneous Reactivity 
  Acute Systemic Toxicity 
  Material-Mediated Pyrogenicity 
  Sub-acute/Sub-chronic Toxicity 
  Genotoxicity 
  Implantation 
  Chronic Toxicity 
  Carcinogenicity 
                                                 
9 Available at https://www.fda.gov/regulatory-information/search-fda-guidance-documents/submission-and-review-
sterility-information-premarket-notification-510k-submissions-devices-labeled  
10 Available at https://www.fda.gov/regulatory-information/search-fda-guidance-documents/reprocessing-medical-
devices-health-care-settings-validation-methods-and-labeling  
11 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  
8 
  Contains Nonbinding Recommendations 
 
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 CDRH 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, per Attachment E of the CDRH 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 and require 
submission of a Traditional, Special, or Abbreviated 510(k). 
 
5.  Test name: Biocompatibility endpoints (identified from CDRH Biocompatibility 
Guidance) 
Methodology: FDA currently-recognized versions of biocompatibility consensus 
standards 
Performance Criteria: All direct or indirect tissue contacting components of the device 
and device-specific instruments should be determined to have an acceptable biological 
response. 
Performance Criteria Source: The CDRH 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 CDRH Biocompatibility 
Guidance. For standard biocompatibility test methods that include comparison device 
control samples, the legally marketed comparison device control samples should perform 
as expected, as specified above for the subject device samples. 
Submission Information: Refer to CDRH Biocompatibility Guidance 
9