The mechanical testing of medical implants and prosthetics involves various methods to assess the implants strength, durability, and performance. Common tests include tension, compression, bend, fatigue, torsion and wear. These tests are crucial to ensuring the implants’ safety and efficacy. The U.S. Food and Drug Administration (FDA) categorizes medical devices into Class I, II, or III based on their risks and the regulatory controls necessary to provide a reasonable assurance of safety and effectiveness. Testing standards for medical devices are often developed for the specific medical device to be tested, as desired biomechanical properties per material and per application vary.
ADMET testing systems are trusted by leading medical device manufacturers, universities, and research laboratories to determine the mechanical properties and endurance limits of biomaterials, medical devices and implants. Our systems meet FDA 21 CFR part 11 requirements and are capable of performing static and fatigue tests in tension, compression, bending, torsion, axial-torsion and planar biaxial according to ASTM and ISO standards. Our ability to design a system to fit specific needs allows ADMET to provide testing solutions for even the most unique and demanding applications.
Common Medical Implants that Require Mechanical Testing
Bone Plates
Used to stabilize broken bones, bone plates are fixed to the bone with screws to hold it in the correct position as it heals. They are designed to be biocompatible and provide mechanical support. Mechanical testing of bone plates includes assessing their bending strength, bending stiffness, fatigue resistance, and compatibility with bone materials.
Bone Screws
Bone screws are used in surgical procedures to secure implants such as plates or rods, stabilize fractures, or facilitate bone fusion. They must be engineered with precise mechanical characteristics to enable secure fixation. Bone screws used in orthopedic applications undergo mechanical testing to assess their load-bearing capacity, pull-out strength, torque resistance, and fatigue behavior.
Dental Implants
A dental implant is a metal post, usually made of titanium, that replaces the root portion of a missing tooth. It serves as an anchor for artificial teeth and requires stringent mechanical testing to ensure stability and functionality. Dental implants are subjected to mechanical testing to evaluate their structural strength by calculating their load-bearing and bending capacity, and fatigue resistance.
Hip Implants
Hip implants are prosthetic devices used to replace a damaged or deteriorated hip joint. These orthopedic devices must be meticulously designed to mimic the natural movement of the hip and withstand long-term wear. Mechanical testing of hip implants is crucial to determine their load-bearing capacity, wear resistance and overall performance.
Knee Prosthesis
Knee prostheses are artificial substitutes for the knee joint used in knee replacement surgeries. These devices are designed to replicate the complex movements of the knee and provide durable functionality. Knee prostheses undergo mechanical testing to evaluate their durability, load-bearing capability, and fatigue resistance, showing the capability of the device to withstand the expected loads over a specified time.
Shoulder Implants
Shoulder implants are orthopedic prosthetic devices that are intended for use as a replacement to damaged shoulder joints. Shoulder implants must be designed to restore the full range of motion and bear the mechanical load associated with arm movement. Shoulder implants undergo mechanical testing to assess their load-bearing capacity, wear resistance, and overall stability.
Spinal Implants
Utilized in spinal surgeries to correct deformities or stabilize the spine, spinal implants may include rods, screws, plates, and cages. They must be designed to align with the complex biomechanics of the spine. Mechanical testing of spinal implants involves evaluating their fatigue resistance, stability, and load-bearing capacity.
Stents
There are multiple types of stents in use today. Intravascular stents are synthetic tubular structures intended for permanent implant in native or graft vasculature. Balloon expandable stents are stents that expand once they reach the intended location by a balloon catheter. A self-expanding stent’s diameter increases from its pre-deployed size to its post-deployed size in the absence of balloon inflation or other mechanical assistance.
Intraocular Lenses (IOLs)
An intraocular lens (IOL) is a small, artificial lens implanted inside the eye to replace or supplement the natural lens. Our testing systems perform the test methods of compression force, axial displacement in compression, and dynamic fatigue durability to determine the mechanical properties of intraocular lenses. Available testing systems are capable of measuring forces as low as 20 mg.
Common Medical Implant Test Types & Standards
Axial-Torsion Testing
Axial torsion testing assesses the performance of orthopedic implants under combined axial (linear) and torsional (rotational) loads. Essential for devices like bone screws or hip implants, this testing ensures that they can withstand both twisting and compressive forces in the body. It plays a crucial role in determining the device’s functionality, reliability, and safety.
- ASTM F543 Standard Specification and Test Methods for Metallic Medical Bone Screws
- Four test methods to measure the vertical torsion (A1), the insertion/removal torque (A2), the pullout strength (A3), and the axial compression load force (A4) of self-tapping bone screws
- ISO 6495 Implants for surgery — Metal bone screws with asymmetrical thread and spherical under-surface — Mechanical requirements and test methods
- Torsion test methods to measure the breaking torque and rotation at failure of metal bone screw
Bend Testing
Orthopedic implants such as bone screws and dental implants require bend testing to evaluate their structural strength. Bend tests can be performed as static tests or dynamic (fatigue) tests. Bend test results include important mechanical properties such as bending (flexural) strength, flexural strain, bending moment, and bending stiffness.
- ASTM F382 Metallic Bone Plates
- Four-point bending fatigue test method to characterize and compare the fatigue performance of different bone plate designs
- ISO 9585 Implants for surgery — Determination of bending strength and stiffness of bone plates
- Bend test method for determining the bending strength and stiffness of bone plates
- ISO 14801 Dynamic loading test for endosseous dental implants
- Fatigue testing method to measure the maximum load and maximum bending moment of dental implants
Fatigue Testing
Fatigue testing simulates the repetitive loads or motions that medical devices experience in the body to evaluate their longevity and reliability. This is vital for devices like orthopedic implants and vascular stents that endure millions of cycles throughout their lifespans. The process involves applying controlled loads, stresses, or strains, mimicking physiological conditions.
Compliance with rigorous standards like ASTM and ISO ensures uniformity in evaluating durability and safety. Fatigue testing results include fatigue resistance, fatigue limit, fracture toughness and more. Analysis of fatigue testing results provides insights into lifespan, potential failure modes, and design improvements.
- ASTM F382 Metallic Bone Plates
- Four-point bending fatigue test to characterize and compare the fatigue performance of different bone plate designs
- ASTM F1717 Spinal Implant Test Methods
- Three static and one fatigue (compression bending) test methods on spinal implant specimens
- ASTM F1800 Standard Practice for Cyclic Fatigue Testing of Metal Tibial Tray Components of Total Knee Joint Replacements
- Fatigue test method to quantify the fatigue strength and lifetime of knee prostheses
- ASTM F2028 Standard Test Methods for Dynamic Evaluation of Glenoid Loosening or Disassociation
- Fatigue test methods to measure how much a prosthetic reverse glenoid component rocks or pivots following cyclic articulation with a mating humeral liner
- ASTM F2077 Standard Test Methods for Intervertebral Body Fusion Devices
- Static and dynamic in vitro test methods of different designs of intervertebral body fusion device assemblies
- ISO 7206 – Determination of endurance properties and performance of stemmed femoral components
- Fatigue test methods to measure the loads hip implant specimens can withstand over a number of cycles
- ISO 14801 – Dynamic loading test for endosseous dental implants
- Fatigue testing method to measure the maximum load and maximum bending moment of dental implants
- ISO 14879-1 Implants for surgery — Total knee-joint prostheses — Part 1: Determination of endurance properties of knee tibial trays
- Fatigue test method reporting the number of cycles applied and mode of failure to examine the defects caused by the loading on knee prostheses
In Vitro Testing
In vitro testing involves evaluating medical devices outside the human body, often in a controlled laboratory environment that simulates physiological conditions. This testing is crucial for understanding how devices like orthopedic implants, stents, or catheters will interact with biological tissues and fluids. It allows for thorough assessments of biocompatibility, functionality, and long-term performance.
- ASTM F2077 Standard Test Methods for Intervertebral Body Fusion Devices
- Static and dynamic in vitro test methods of different designs of intervertebral body fusion device assemblies
Shear Testing
Shear properties can be calculated via different test types including tension, flexion, and compression as well as different test set ups such as the V-notched rail method, short beam method, and more. The most common measurement obtained from a shear test is the shear strength, shear modulus, shear strain, and shear yield stress.
- ASTM F1829 Static Evaluation of the Glenoid Locking Mechanism in Shear
- Shear test method for evaluating the performance of metal or composite-backed anatomic glenoid prostheses’ locking mechanism
- ASTM F2077 Standard Test Methods for Intervertebral Body Fusion Devices
- Static and dynamic in vitro test methods of different designs of intervertebral body fusion device assemblies
Tensile Testing
Materials used in the making of orthopedic implants require tension testing to provide information on their strength, ductility and superelasticity. These attributes are vital for understanding how a material or device will perform under stretching or pulling forces in the body.
- ASTM F2516 – Standard Test Method for Tension Testing of Nickel-Titanium Superelastic Materials
- Tensile test method of superelastic nickel-titanium (nitinol) materials to determine the upper plateau strength, lower plateau strength, residual elongation, tensile strength, and elongation.
What equipment do I need for medical implant mechanical testing?
To perform mechanical testing on medical implants, you will need a testing frame equipped with the appropriate fixture to clamp the test specimen, a load cell, and a controller. The type of testing system required will be dependent on the orthopedic implant tested, the type of test, and the required calculations.
eXpert 5900
Electromechanical Fatigue Testing Machine
The eXpert 5900 is ideal for performing fatigue testing on orthopedic implants that require an axial fatigue load. The 5900 series systems can be equipped with special fixturing to mount a variety of orthopedic implants.
Common Orthopedic Implants and Standards Tested:
- Hip – ISO 7206
- Knee – ASTM F2777
- Spinal Implants – ASTM F1717, ASTM F1798, ASTM F2077
- Dental – ISO 14801
- Bone Plates – ASTM F382
- Intramedullary Rods – ASTM F1264
eXpert 8000
Axial-Torsion Testing Machines
The eXpert 8600 is ideal for performing static testing on orthopedic implants that require both an axial and torsional load.
Our eXpert 8900 series systems are ideal for performing fatigue testing on orthopedic implants that require both an axial and torsional load.
Common Orthopedic Implants and Standards Tested:
- Bone Screws – ASTM F543
- Bone Plates – ASTM F382, ASTM F384
- External Skeletal Fixation Device – ASTM F1541
- Small Bore Connectors – ISO 80369
- Spinal Implants – ASTM F1717, ASTM F1798, ASTM F2077
eXpert 3000
Torsional Testing Machine
The eXpert 3000 series torsional testing machines feature a variety of grips and fixtures to accommodate testing of orthopedic devices such as bone screw testing, spinal constructs, and intramedullary rods.
Common Orthopedic Implants and Standards Tested:
- Spinal – ASTM F1717, ASTM F2077
- Bone Screws – ASTM F543 A1 & A2, ISO 6475
- Intramedullary Rods – ASTM F1264
eXpert 1900
Fatigue Testing Machine
The eXpert 1900 series servo-hydraulic fatigue testing machine is ideal for orthopedic implants that require high-force fatigue testing. They can be equipped with special fixturing to mount hip implant specimens.
Common Orthopedic Implants and Standards Tested:
- Hip – ISO 7206
- Knee – ASTM F2777
- Spinal – ASTM F1717, ASTM F2077
- Dental – ISO 14801
- Bone Plates – ASTM F382
- Intramedullary Rods – ASTM F1264
Test Setups & Fixtures For Medical Implant Testing
Orthopedic devices—such as hip, knee, shoulder, dental, and spinal implants—are among the most commonly encountered in our experience at ADMET. We specialize in providing advanced material testing systems with full fixturing that rigorously evaluate the mechanical integrity and safety of these crucial medical components, ensuring they meet or exceed regulatory standards. Below we will explore the types of orthopedic implant tests and the required fixturing to perform them.
Hip Implant Test Setup per ISO 7206 on eXpert 1900 Hydraulic Fatigue Testing Machine 
Metallic Bone Screws Torsion Test Setup per ASTM F543 on eXpert 8900 
Bone plate bending fatigue testing on eXpert 8900 Axial-Torsion Fatigue Testing Machine Intervertebral Body Fusion Devices Test Setup per ASTM F2077 on eXpert 5955 Electrodynamic Testing Machine 
eXpert 8900 – ASTM F1717 Spinal Implant Test Fixture 
ISO 14801 Fiture in a Temperature-Controlled Bath 
Shoulder Implant Test Setup on eXpert 1900 Hydraulic Fatigue Testing Machine
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