Testing standard
ASTM F384
Standard Specifications and Test Methods for Metallic Angled Orthopedic Fracture Fixation Devices
Written and technically reviewed by Dak System Inc. engineeringLast reviewed
ASTM F384 combines specifications and test methods for metallic angled orthopedic fracture fixation devices. It carries two mechanical methods — a single cycle compression bend and a bending fatigue test — alongside requirements for materials, labelling and handling, and a scheme for classifying the geometry of angled devices.
At a glance
- Test type
- Fracture toughness
- Published by
- ASTM
- Edition
- F384-24
- Runs on
- Series 7200 and Series 9000
What the test does
The document covers two mechanical methods alongside its specification content. The single cycle compression bend loads the device statically across the junction between blade and plate, giving a bending strength and a bending stiffness determined from the load-displacement curve by the standard's own construction rules. The bending fatigue method cycles the same geometry at a chosen load to a defined run-out, recording either survival or the cycle at which failure occurred. All values are stated in SI units, with no other units included in the standard.
What it measures, and why it matters
How an angled fixation device behaves where it is weakest. The junction between the blade and the plate is a change of both section and direction, so it concentrates stress, and it is where these implants break. Both methods load bending across it deliberately. The pairing of static and fatigue results is the substance: a patient loads a fixation device thousands of times while a fracture unites, at forces well below single-cycle capacity, so strength alone says little. Stiffness matters for a third reason — a construct that deflects lets the fracture ends move, and a fracture that moves does not unite well.
The angle is the point
An angled device concentrates stress where the blade meets the plate. Both test methods load that junction deliberately.
- Single cycle compression bend
- A static methodEstablishes the strength and stiffness of the device across its angle.
- Bending fatigue
- A cyclic methodEstablishes whether it survives repeated loading, which is how these devices fail clinically.
- Also specifies
- Materials, labelling and handling requirementsIt is a specification as well as a set of test methods, which is why the title carries both words.
- Classification
- A scheme for the geometry of angled devicesConsistent geometric definitions are what make results from different designs comparable at all.
- Units
- SI onlyNo other units are included in the standard, so a report in inch-pound units is not in conformance.
- Photograph the fracture at the angle
- DakWhere a device broke relative to the blade-plate junction is what a designer acts on.
Fatigue is the clinically relevant mode. A patient loads a fixation device thousands of times before the fracture unites, so the single cycle test establishes capacity and the fatigue test establishes whether that capacity survives.
Test speed
- Static
- A controlled rate to the defined endpoint
- Fatigue
- A defined frequency and run-out
- Reported
- Strength and stiffness statically; survival or cycles at failure dynamically
- Verify dynamic force at frequency
- Dak
Calculations
Determined from the load-displacement curve by the method's construction rules
Not read by eye. The construction is defined so that two laboratories reach the same number from the same curve.
The slope of the linear region of the load-displacement curve
Reported alongside strength, because a device can be strong and compliant, and a fracture that moves does not unite well.
Survival at a stated load to a stated run-out, or the cycle at failure
Both the load and the run-out must be reported for a fatigue figure to be interpretable.
How the test runs
- 01Identify the device type and classify its geometry using the standard's scheme.
- 02Confirm the material and labelling requirements are met.
- 03Set up the bend fixture so the load is carried across the blade-plate angle.
- 04Select a load cell matched to the device, not to the frame.
- 05For the static test, load at the controlled rate to the defined endpoint.
- 06Determine bending strength and stiffness from the curve by the method's rules.
- 07For fatigue, verify the applied force dynamically at the test frequency.
- 08Cycle at the chosen load to the defined run-out.
- 09Record survival or the cycle at which failure occurred.
- 10Photograph the fracture relative to the angle.
- 11Report all values in SI units.
What the report has to contain
- Reference to ASTM F384 and the edition
- Device identification, material, and its classification under the standard's scheme
- Fixture geometry and how the load crossed the angle
- Static rate, or fatigue frequency and waveform
- Bending strength and bending stiffness
- Fatigue load, run-out and the outcome
- How dynamic force was verified
- Fracture location relative to the blade-plate junction
- Photographs of failed devices
- Confirmation that SI units were used
What the machine must be capable of
Static loading at a controlled rate and cyclic loading at a defined frequency, with a load cell matched to the device rather than to the frame — these implants are commonly tested at hundreds of newtons to a few kilonewtons, well below the capacity of a general-purpose frame. For the fatigue method the applied force must be verified dynamically at the test frequency, since a static calibration does not describe a machine in motion and any shortfall is inherited by every cycle of the run.
What goes wrong in practice
Reporting a fatigue result without both the load and the run-out, which makes it uninterpretable — surviving a hundred thousand cycles and a million at the same load are different claims. Reading strength off the curve by eye instead of by the standard's construction rules. Omitting the geometric classification, without which the result cannot be compared with another design. Verifying force only statically. And presenting mechanical results as evidence of clinical performance, which this document does not support: bone quality, fracture pattern, surgical technique and how hard a particular patient loads the limb all sit outside what any bench test can reach.
ASTM F384 or ASTM F1264
| ASTM F384 | ASTM F1264 | |
|---|---|---|
| Devices | Angled — blade plates and similar | Intramedullary nails and rods |
| Static methods | Single cycle compression bend | Four-point bend and torsion |
| Fatigue | Bending fatigue | Bending fatigue, plus locking screws |
| Both are | Specification and test methods | Specification and test methods |
Two device families with parallel documents. Both combine a specification with test methods, and both are explicit that they characterise mechanics rather than predict clinical outcome.
Questions we are asked about this test
What is ASTM F384?
It is the ASTM document for metallic angled orthopedic fracture fixation devices — blade plates and similar implants used in surgical internal fixation of the skeleton. It is both a specification, covering materials, labelling and handling, and a set of test methods: a single cycle compression bend and a bending fatigue test. The current designation is ASTM F384-24.
Why do both methods load the device across its angle?
Because that is where these devices break. An angled implant has a junction between the blade and the plate, and the change of section and direction concentrates stress there. Loading the device anywhere else would measure a region that does not govern its life. Both the static and the fatigue method are arranged to carry bending across that junction deliberately.
Why is a fatigue test needed as well as a static one?
Because fixation devices fail by fatigue, not by overload. A patient loads an implant thousands of times while the fracture unites, at forces well below the single-cycle capacity, and a device that is strong enough on the first cycle can still crack after several hundred thousand. The static test establishes capacity; the fatigue test establishes whether that capacity survives the clinical loading history.
Why does the standard include a classification scheme?
Because angled devices vary enormously in geometry — blade length, angle, plate length, hole pattern — and without consistent definitions the results from two designs cannot be compared. Classifying the geometry, and reporting the classification alongside the mechanical results, is what turns a set of individual measurements into a body of comparable data.
What does SI only mean in practice?
That the standard states its values in SI units with no other units included, so a report in inch-pound units is not in conformance with it. This differs from the many ASTM standards with a dual designation, where the two systems are used independently. It is worth checking when transcribing older data, since some historical device testing was recorded in inch-pound units.
Why report stiffness as well as strength?
Because a device can be strong and compliant, and that combination is clinically poor. A fixation construct that deflects appreciably lets the fracture ends move relative to one another, and a fracture that moves too much does not unite well even if nothing breaks. Strength describes what it takes to fail the device; stiffness describes how it behaves at loads it survives.
Does a good result predict clinical success?
No. Like the other ASTM implant documents, this one characterises mechanical behaviour under defined laboratory conditions so devices can be compared with one another. Bone quality, fracture pattern, surgical technique and patient loading all sit outside it. A submission that presents mechanical results as evidence of clinical performance is claiming more than the method supports.
Running ASTM F384 on the Series 7200 and Series 9000
Dak verifies against whichever standard the method names, and where a class applies our frames sit a class tighter than it asks.
| The method asks for | Dak supplies | |
|---|---|---|
| Capacity | Moderate — angled fixation devices are commonly tested at hundreds of newtons to a few kilonewtons | Load cells from 1 kg to 60 ton on the Series 7200, and 0.5 to 100 kN on the Series 9000 |
| Force accuracy | ASTM E4 statically, with dynamic force verification for the fatigue method | Verified to ASTM E4, and to ISO 7500-1 Class 0.5 |
| Gripping | A compression bend fixture that loads the device across its angle, and a fatigue arrangement of the same geometry | Our a fixture built for this method, built to the specimen |
| Environment | 23 ± 2 °C standard laboratory atmosphere | 3009 series chambers, −150 °C to +400 °C — temperature only |
This page describes the method as practised. The governing text is the current edition from the issuing body. Tell us what you are testing and we will answer with the machine, the fixture and a quotation.