(98 days)
In Anatomic:
The stem and head may be used by themselves, as a hemiathroplasty, if the natural glenoid provides a sufficient bearing surface, or in conjunction with the glenoid, as a total replacement.
The AETOS Shoulder System is to be used only in patients with an intact or reconstructable rotator cuff, where it is intended to provide increased mobility and to relieve pain. The AETOS Shoulder System is indicated for use as a replacement of shoulder joints disabled by:
- Rheumatoid arthritis
- Non-inflammatory degenerative joint disease
- Correction of functional deformity
- Fractures of the humeral head
- Traumatic arthritis
- Revision of other devices if sufficient bone stock remains
The coated humeral component is intended for uncement is intended for cement is intended for cemented use only.
In Reverse:
The AETOS Shoulder System is indicated for use as a replacement of shoulder joints for patients with a functional deltoid muscle and with massive and non-repairable rotator cuff-tear with pain disabled by:
- Rheumatoid arthritis
- Non-inflammatory degenerative joint disease
- Correction of functional deformity
- Fractures of the humeral head
- Traumatic arthritis
- Revision of devices if sufficient bone stock remains
The humeral liner component is indicated for use in the AETOS Shoulder System as a primary reverse total shoulder replacement and for use when converting an anatomic AETOS Shoulder System into a reverse shoulder construct. This facilitates the conversion without the removal of the humeral stem during revision surgery for patients with a functional deltoid muscle. The component is permitted to be used in the conversion from anatomic to reverse if the humeral stem is well fixed, the patient has a functional deltoid muscle; the arthroplasty is associated with a massive and non-repairable rotator cuff tear.
The coated humeral stem is indicated for uncemented use. The coated glenoid baseplate is intended for cementless application with the addition of screws for fixation.
Note: All implant components are single use.
The AETOS Shoulder System consists of:
In an anatomic configuration: A humeral stem (Titanium) with a plasma spray coating (Titanium), a compatible humeral head (CoCr) with a compatible glenoid (UHMWPE). The AETOS Shoulder System stem and head may be used by themselves for hemiarthroplasty.
In a reverse configuration: A humeral stem (Titanium) with a plasma spray coating (Titanium), a compatible liner (UHMWPE), glenoid baseplate (Titanium with Titanium plasma spray), glenosphere (CoCr with Titanium retaining component), peripheral screws (Titanium), center screw (Titanium), optional humeral spacer (Titanium), and optional post extension (Titanium with Titanium plasma spray).
This document is a 510(k) Premarket Notification from the FDA regarding the AETOS Shoulder System. It is primarily concerned with establishing substantial equivalence to previously cleared devices based on non-clinical performance data and technological similarities/differences.
Therefore, a study proving the device meets acceptance criteria related to AI/algorithm performance (as described in your prompt, e.g., sensitivity, specificity, human reader improvement) was not performed nor is it relevant to this specific FDA submission.
The document explicitly states: "Clinical performance data were not necessary to demonstrate substantial equivalence of the subject device."
Instead, the acceptance criteria for this device are established through engineering and mechanical testing, ensuring the physical device components meet design specifications and performance standards comparable to legally marketed predicate devices.
Here's how to interpret the available information in the context of your request:
1. A table of acceptance criteria and the reported device performance:
The acceptance criteria are implied by the non-clinical performance data testing listed, which assess the mechanical integrity and function of the shoulder system components. The "reported device performance" is that the device met these standards, demonstrating substantial equivalence to the predicate devices. This type of submission relies on the device performing as well as the predicate in relevant mechanical and material property tests to prove safety and effectiveness.
| Acceptance Criteria (Implied) | Reported Device Performance |
|---|---|
| Construct fatigue | Met standards |
| Dynamic glenoid loosening / dissociation per ASTM F2028 | Met standards |
| Range of motion evaluation | Met standards |
| Scapular notching evaluation | Met standards |
| Construct disassembly evaluation | Met standards |
| Total humeral offset evaluation | Met standards |
2. Sample size used for the test set and the data provenance:
- Sample Size: Not explicitly stated in terms of patient data. The "test set" here refers to the physical components of the shoulder system subjected to mechanical testing. The sample size for these engineering tests would typically be a specific number of manufactured components.
- Data Provenance: This is not patient- or human-read data. It's likely from internal laboratory testing conducted by the manufacturer (Smith & Nephew, Inc. at Cordova, Tennessee). It's not retrospective or prospective clinical data.
3. Number of experts used to establish the ground truth for the test set and the qualifications of those experts:
This is not applicable. The "ground truth" for mechanical performance of an orthopedic implant is established through standardized engineering tests (e.g., ASTM standards) and material science principles, not expert consensus from medical professionals. The "experts" would be engineers, material scientists, and quality assurance personnel.
4. Adjudication method (e.g. 2+1, 3+1, none) for the test set:
Not applicable, as this refers to human expert review of clinical data, which was not the basis of this submission. The "adjudication" is met by demonstrating compliance with established engineering and material standards through testing.
5. If a multi-reader multi-case (MRMC) comparative effectiveness study was done, If so, what was the effect size of how much human readers improve with AI vs without AI assistance:
Not applicable. This device is a physical orthopedic implant, not an AI/software as a medical device (SaMD) that assists human readers.
6. If a standalone (i.e. algorithm only without human-in-the-loop performance) was done:
Not applicable. This is not an algorithm.
7. The type of ground truth used (expert consensus, pathology, outcomes data, etc.):
The "ground truth" for this device's acceptance is established through compliance with existing engineering standards and successful completion of specified mechanical and material property tests. These tests are designed to simulate physiological loads and conditions to ensure the device's durability and performance.
8. The sample size for the training set:
Not applicable. This device does not involve a training set for an algorithm.
9. How the ground truth for the training set was established:
Not applicable.
In summary: The provided document is a 510(k) clearance for a physical medical device (shoulder system). The "acceptance criteria" and "study" details you requested are tailored to AI/software products. For this device, acceptance is based on non-clinical (engineering) performance data demonstrating substantial equivalence to older, already cleared devices, rather than clinical trials or AI performance metrics.
{0}------------------------------------------------
Image /page/0/Picture/0 description: The image shows the logo of the U.S. Food and Drug Administration (FDA). The logo consists of two parts: the Department of Health & Human Services logo on the left and the FDA text logo on the right. The text logo has the FDA acronym in a blue square, followed by the words "U.S. FOOD & DRUG ADMINISTRATION" in blue.
June 7, 2023
Smith & Nephew, Inc. Patrick Hughes Senior Regulatory Affairs Specialist 7135 Goodlett Farms Parkway Cordova, Tennessee 38016
Re: K230572
Trade/Device Name: AETOS Shoulder System Regulation Number: 21 CFR 888.3660 Regulation Name: Shoulder joint metal/polymer semi-constrained cemented prosthesis Regulatory Class: Class II Product Code: KWS, HSD, KWT, PHX Dated: May 10, 2023 Received: May 10, 2023
Dear Patrick Hughes:
We have reviewed your Section 510(k) premarket notification of intent to market the device referenced above and have determined the device is substantially equivalent (for the indications for use stated in the enclosure) to legally marketed predicate devices marketed in interstate commerce prior to May 28, 1976, the enactment date of the Medical Device Amendments, or to devices that have been reclassified in accordance with the provisions of the Federal Food, Drug, and Cosmetic Act (Act) that do not require approval of a premarket approval application (PMA). You may, therefore, market the device, subject to the general controls provisions of the Act. Although this letter refers to your product as a device, please be aware that some cleared products may instead be combination products. The 510(k) Premarket Notification Database located at https://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfpmn/pmn.cfm identifies combination product submissions. The general controls provisions of the Act include requirements for annual registration, listing of devices, good manufacturing practice, labeling, and prohibitions against misbranding and adulteration. Please note: CDRH does not evaluate information related to contract liability warranties. We remind you, however, that device labeling must be truthful and not misleading.
If your device is classified (see above) into either class II (Special Controls) or class III (PMA), it may be subject to additional controls. Existing major regulations affecting your device can be found in the Code of Federal Regulations, Title 21, Parts 800 to 898. In addition, FDA may publish further announcements concerning your device in the Federal Register.
Please be advised that FDA's issuance of a substantial equivalence determination does not mean that FDA has made a determination that your device complies with other requirements of the Act or any Federal
{1}------------------------------------------------
statutes and regulations administered by other Federal agencies. You must comply with all the Act's requirements, including, but not limited to: registration and listing (21 CFR Part 807); labeling (21 CFR Part 801); medical device reporting of medical device-related adverse events) (21 CFR 803) for devices or postmarketing safety reporting (21 CFR 4, Subpart B) for combination products (see https://www.fda.gov/combination-products/guidance-regulatory-information/postmarketing-safety-reportingcombination-products); good manufacturing practice requirements as set forth in the quality systems (QS) regulation (21 CFR Part 820) for devices or current good manufacturing practices (21 CFR 4, Subpart A) for combination products; and, if applicable, the electronic product radiation control provisions (Sections 531-542 of the Act); 21 CFR 1000-1050.
Also, please note the regulation entitled, "Misbranding by reference to premarket notification" (21 CFR Part 807.97). For questions regarding the reporting of adverse events under the MDR regulation (21 CFR Part 803), please go to https://www.fda.gov/medical-device-safety/medical-device-reportingmdr-how-report-medical-device-problems.
For comprehensive regulatory information about medical devices and radiation-emitting products, including information about labeling regulations, please see Device Advice (https://www.fda.gov/medicaldevices/device-advice-comprehensive-regulatory-assistance) and CDRH Learn (https://www.fda.gov/training-and-continuing-education/cdrh-learn). Additionally, you may contact the Division of Industry and Consumer Education (DICE) to ask a question about a specific regulatory topic. See the DICE website (https://www.fda.gov/medical-device-advice-comprehensive-regulatoryassistance/contact-us-division-industry-and-consumer-education-dice) for more information or contact DICE by email (DICE@fda.hhs.gov) or phone (1-800-638-2041 or 301-796-7100).
Image /page/1/Figure/4 description: The image shows a digital signature. The signature is from Joseph P. Russell. The date of the signature is 2023.06.07 15:52:32 -04'00'. The image also includes the word 'Sincerely,'.
For: Farzana Sharmin, Ph.D. Acting Assistant Director DHT6A: Division of Joint Arthroplasty Devices OHT6: Office of Orthopedic Devices Office of Product Evaluation and Quality Center for Devices and Radiological Health
Enclosure
{2}------------------------------------------------
Indications for Use
510(k) Number (if known) K230572
Device Name AETOS Shoulder System
Indications for Use (Describe)
In Anatomic:
The stem and head may be used by themselves, as a hemiathroplasty, if the natural glenoid provides a sufficient bearing surface, or in conjunction with the glenoid, as a total replacement.
The AETOS Shoulder System is to be used only in patients with an intact or reconstructable rotator cuff, where it is intended to provide increased mobility and to relieve pain. The AETOS Shoulder System is indicated for use as a replacement of shoulder joints disabled by:
- Rheumatoid arthritis
- · Non-inflammatory degenerative joint disease
- · Correction of functional deformity
- · Fractures of the humeral head
- · Traumatic arthritis
- · Revision of other devices if sufficient bone stock remains
The coated humeral component is intended for uncement is intended for cement is intended for cemented use only.
In Reverse:
The AETOS Shoulder System is indicated for use as a replacement of shoulder joints for patients with a functional deltoid muscle and with massive and non-repairable rotator cuff-tear with pain disabled by:
- Rheumatoid arthritis
- · Non-inflammatory degenerative joint disease
- · Correction of functional deformity
- · Fractures of the humeral head
- · Traumatic arthritis
- · Revision of devices if sufficient bone stock remains
The humeral liner component is indicated for use in the AETOS Shoulder System as a primary reverse total shoulder replacement and for use when converting an anatomic AETOS Shoulder System into a reverse shoulder construct. This facilitates the conversion without the removal of the humeral stem during revision surgery for patients with a functional deltoid muscle. The component is permitted to be used in the conversion from anatomic to reverse if the humeral stem is well fixed, the patient has a functional deltoid muscle; the arthroplasty is associated with a massive and non-repairable rotator cuff tear.
The coated humeral stem is indicated for uncemented use. The coated glenoid baseplate is intended for cementless application with the addition of screws for fixation.
Note: All implant components are single use.
Type of Use (Select one or both, as applicable)
X Prescription Use (Part 21 CFR 801 Subpart D)
Over-The-Counter Use (21 CFR 801 Subpart C)
{3}------------------------------------------------
CONTINUE ON A SEPARATE PAGE IF NEEDED.
This section applies only to requirements of the Paperwork Reduction Act of 1995.
DO NOT SEND YOUR COMPLETED FORM TO THE PRA STAFF EMAIL ADDRESS BELOW.
The burden time for this collection of information is estimated to average 79 hours per response, including the time to review instructions, search existing data sources, gather and maintain the data needed and complete and review the collection of information. Send comments regarding this burden estimate or any other aspect of this information collection, including suggestions for reducing this burden, to:
Department of Health and Human Services Food and Drug Administration Office of Chief Information Officer Paperwork Reduction Act (PRA) Staff PRAStaff(@fda.hhs.gov
"An agency may not conduct or sponsor, and a person is not required to respond to, a collection of information unless it displays a currently valid OMB number."
{4}------------------------------------------------
Section 5 - 510(k) Summary AETOS Shoulder System Line Extensions
| Sponsor | Smith & Nephew, Inc.Orthopedic Division7135 Goodlett Farms ParkwayCordova, Tennessee 38016 |
|---|---|
| Establishment Number | 3008744062 |
| Point of Contact | Patrick HughesSenior Regulatory Specialist352-359-7940 |
| Date | June 5, 2023 |
| Trade Name | AETOS Shoulder System |
| Common Name | Shoulder Prosthesis |
| Product Code | 1. KWS2. HSD3. KWT4. PHX |
| Regulation | 1. Shoulder joint metal/polymer semi-constrained cementedprosthesis (21 CFR 888.3660)2. Shoulder joint humeral (hemi-shoulder) metallic uncemented (21CFR 888.3690)3. Shoulder joint metal/polymer non-constrained cementedprosthesis (21 CFR 888.3650)4. Shoulder joint metal/polymer semi-constrained cementedprosthesis (21 CFR 888.3660) |
| Classification | Class II |
| Predicate Devices | Smith & Nephew AETOS Shoulder System: K220847 (Primary)Tornier, Inc. PERFORM Humeral System - Stem: K201315LimaCorporate SMR TT Augmented Glenoid System: K200171 |
| Reference Devices | Encore AltiVate Reverse Humeral Stem, AltiVate Reverse SmallSpacer, Altivate Reverse, Small Hemi-Adapter, AltiVate Reverse,Small Socket Insert: K172351Zimmer Trabecular Metal Reverse Shoulder System: K052906Univers Revers Shoulder Prosthesis System: K130129 |
| LimaCorporate Bone Screws dia. 5,0 mm: K210717 | |
| LimaCorporate SMR 40mm Glenosphere: K142139 | |
| Titan Reverse Shoulder System: K130050 | |
| Titan Reverse Shoulder System: K181999 | |
| Titan Modular Total Shoulder System Fin-Lock Glenoid: K152047 | |
| Classification Panel | Orthopedic |
| Device Description | The AETOS Shoulder System consists of:In an anatomic configuration: A humeral stem (Titanium) with aplasma spray coating (Titanium), a compatible humeral head (CoCr)with a compatible glenoid (UHMWPE). The AETOS ShoulderSystem stem and head may be used by themselves forhemiarthroplasty.In a reverse configuration: A humeral stem (Titanium) with a plasmaspray coating (Titanium), a compatible liner (UHMWPE), glenoidbaseplate (Titanium with Titanium plasma spray), glenosphere (CoCrwith Titanium retaining component), peripheral screws (Titanium),center screw (Titanium), optional humeral spacer (Titanium), andoptional post extension (Titanium with Titanium plasma spray). |
| Intended Use/ | The AETOS Shoulder System is intended for:Replacement of shoulder joints in primary anatomic or primary reverse arthroplasty. Replacement of shoulder joint devices in revision cases if sufficient bone stock is present. The AETOS Shoulder System also allows for conversions from anatomic to reverse in case of revision. |
| Indications for Use | In Anatomic:The stem and head may be used by themselves, as a hemiarthroplasty,if the natural glenoid provides a sufficient bearing surface, or in conjunction with the glenoid, as a total replacement.The AETOS Shoulder System is to be used only in patients with an intact or reconstructable rotator cuff, where it is intended to provide increased mobility and stability and to relieve pain. The AETOS Shoulder System is indicated for use as a replacement of shoulder joints disabled by:Rheumatoid arthritis Non-inflammatory degenerative joint disease |
| • Correction of functional deformity | |
| • Fractures of the humeral head | |
| • Traumatic arthritis | |
| • Revision of other devices if sufficient bone stock remains | |
| The coated humeral component is intended for uncemented use. Theglenoid component is intended for cemented use only. | |
| In Reverse:The AETOS Shoulder System is indicated for use as a replacement ofshoulder joints for patients with a functional deltoid muscle and withmassive and non-repairable rotator cuff-tear with pain disabled by: | |
| • Rheumatoid arthritis | |
| • Non-inflammatory degenerative joint disease | |
| • Correction of functional deformity | |
| • Fractures of the humeral head | |
| • Traumatic arthritis | |
| • Revision of devices if sufficient bone stock remains | |
| The humeral liner component is indicated for use in the AETOSShoulder System as a primary reverse total shoulder replacement andfor use when converting an anatomic AETOS Shoulder System into areverse shoulder construct. This facilitates the conversion without theremoval of the humeral stem during revision surgery for patients witha functional deltoid muscle. The component is permitted to be used inthe conversion from anatomic to reverse if the humeral stem is wellfixed, the patient has a functional deltoid muscle; the arthroplasty isassociated with a massive and non-repairable rotator cuff tear. | |
| The coated humeral stem is indicated for uncemented use. The coatedglenoid baseplate is intended for cementless application with theaddition of screws for fixation. | |
| Note: All implant components are single use. | |
| NonclinicalPerformance Data | • Construct fatigue |
| • Dynamic glenoid loosening / dissociation per ASTM F2028 | |
| • Range of motion evaluation | |
| • Scapular notching evaluation | |
| • Construct disassembly evaluation | |
| • Total humeral offset evaluation | |
| Clinical PerformanceData | Clinical performance data were not necessary to demonstratesubstantial equivalence of the subject device. |
| TechnologicalSimilarities andDifferencesCompared toPredicate | The subject submission represents line extensions to the AETOSShoulder System as follows:AETOS +15 Full Wedge BaseplatesAETOS +15 Full Wedge Baseplates have the same intended use aspredicate AETOS baseplates: to resurface glenoid bone as part ofreverse total shoulder arthroplasty. Like predicate AETOS baseplates,AETOS +15 Full Wedge Baseplates are manufactured from Ti6Al4Vand have an unalloyed titanium plasma spray coating as well as screw and post features for uncemented fixation. Like all AETOSbaseplates, AETOS +15 Full Wedge Baseplates mate with compatibleglenospheres via peripheral taper. AETOS +15 Full WedgeBaseplates have the same centered configuration, diameter, screw-hole configuration, and post extension compatibility as predicateaugmented AETOS baseplates but differ in that they provide anadditional five degrees of augmentation. AETOS +15 Full WedgeBaseplate components use packaging configurations and sterilizationprocesses identical to cited predicates.AETOS 38mm +3mm Eccentric GlenospheresAETOS 38mm +3mm Eccentric Glenospheres have the sameintended use as predicate AETOS glenospheres: to provide aspherical surface for articulation with AETOS Shoulder Systemhumeral liners as part of a reverse shoulder implant construct. Likepredicate AETOS glenospheres, AETOS 38mm +3mm EccentricGlenospheres are manufactured from CoCrMo and attach tocompatible baseplates with a retainer and screw manufactured fromTi6Al4V. AETOS 38mm +3mm Eccentric Glenospheres have thesame articulating radius, lateralization, and eccentricity as predicateAETOS 42mm +3mm Eccentric Glenospheres but differ in that theyfeature a smaller diameter. AETOS 38mm +3mm EccentricGlenospheres use packaging configurations and sterilizationprocesses identical to cited predicates.AETOS Reverse Humeral SpacersAETOS Reverse Humeral Spacers have the same intended use aspredicate and reference humeral spacers: to provide a method forlateralizing reverse shoulder arthroplasty implant constructs on thehumeral side by introducing additional material between humeral stems and humeral liners. Like predicate Tornier PerFORM humeral |
| spacers, AETOS Reverse Humeral Spacers are manufactured fromTi-6Al-4V, provide 9mm of thickness, are available in two sizes, andmate with compatible stems via Morse taper. AETOS ReverseHumeral Spacers differ from predicate and reference devices in thatcompatibility with humeral stems on the distal aspect andcompatibility with humeral liners on the proximal aspect requireconnection geometry specific to their respective systems. Likepredicate Tornier PerFORM humeral spacers, AETOS ReverseHumeral Spacers are provided sterile via gamma irradiation. | |
| Conclusion | Substantial equivalence of the AETOS Shoulder System to citedpredicates can be demonstrated based on the following:The subject and predicate devices have the same intended useand similar or the same Indications for Use. The subject and predicate devices share similar functional andtechnological characteristics via the same operationalprinciples. The subject and predicate devices are made from the samematerials and packaged and sterilized using the same methods. Bench testing supports that any minor dimensional differencesbetween subject and predicate devices do not introduce or exacerbateany potential issues of safety and effectiveness. As a result Smith &Nephew concludes the subject AETOS Shoulder System LineExtensions are substantially equivalent to cited predicate devices. |
{5}------------------------------------------------
{6}------------------------------------------------
{7}------------------------------------------------
{8}------------------------------------------------
§ 888.3660 Shoulder joint metal/polymer semi-constrained cemented prosthesis.
(a)
Identification. A shoulder joint metal/polymer semi-constrained cemented prosthesis is a device intended to be implanted to replace a shoulder joint. The device limits translation and rotation in one or more planes via the geometry of its articulating surfaces. It has no linkage across-the-joint. This generic type of device includes prostheses that have a humeral resurfacing component made of alloys, such as cobalt-chromium-molybdenum, and a glenoid resurfacing component made of ultra-high molecular weight polyethylene, and is limited to those prostheses intended for use with bone cement (§ 888.3027).(b)
Classification. Class II. The special controls for this device are:(1) FDA's:
(i) “Use of International Standard ISO 10993 ‘Biological Evaluation of Medical Devices—Part I: Evaluation and Testing,’ ”
(ii) “510(k) Sterility Review Guidance of 2/12/90 (K90-1),”
(iii) “Guidance Document for Testing Orthopedic Implants with Modified Metallic Surfaces Apposing Bone or Bone Cement,”
(iv) “Guidance Document for the Preparation of Premarket Notification (510(k)) Application for Orthopedic Devices,” and
(v) “Guidance Document for Testing Non-articulating, ‘Mechanically Locked’ Modular Implant Components,”
(2) International Organization for Standardization's (ISO):
(i) ISO 5832-3:1996 “Implants for Surgery—Metallic Materials—Part 3: Wrought Titanium 6-aluminum 4-vandium Alloy,”
(ii) ISO 5832-4:1996 “Implants for Surgery—Metallic Materials—Part 4: Cobalt-chromium-molybdenum casting alloy,”
(iii) ISO 5832-12:1996 “Implants for Surgery—Metallic Materials—Part 12: Wrought Cobalt-chromium-molybdenum alloy,”
(iv) ISO 5833:1992 “Implants for Surgery—Acrylic Resin Cements,”
(v) ISO 5834-2:1998 “Implants for Surgery—Ultra-high Molecular Weight Polyethylene—Part 2: Moulded Forms,”
(vi) ISO 6018:1987 “Orthopaedic Implants—General Requirements for Marking, Packaging, and Labeling,” and
(vii) ISO 9001:1994 “Quality Systems—Model for Quality Assurance in Design/Development, Production, Installation, and Servicing,” and
(3) American Society for Testing and Materials':
(i) F 75-92 “Specification for Cast Cobalt-28 Chromium-6 Molybdenum Alloy for Surgical Implant Material,”
(ii) F 648-98 “Specification for Ultra-High-Molecular-Weight Polyethylene Powder and Fabricated Form for Surgical Implants,”
(iii) F 799-96 “Specification for Cobalt-28 Chromium-6 Molybdenum Alloy Forgings for Surgical Implants,”
(iv) F 1044-95 “Test Method for Shear Testing of Porous Metal Coatings,”
(v) F 1108-97 “Specification for Titanium-6 Aluminum-4 Vanadium Alloy Castings for Surgical Implants,”
(vi) F 1147-95 “Test Method for Tension Testing of Porous Metal,”
(vii) F 1378-97 “Standard Specification for Shoulder Prosthesis,” and
(viii) F 1537-94 “Specification for Wrought Cobalt-28 Chromium-6 Molybdenum Alloy for Surgical Implants.”