Mechanical Testing of Shoulder Prostheses
ASTM F1378 sets specifications and guidelines for the mechanical testing of shoulder prostheses for total or hemiarthroplasty. Shoulder prostheses have a functional design to replace and mimic the function articulated by glenoid and humeral components. This function can significantly improve the quality of life and mobility of patients with shoulder impairments.
Shoulder replacements are not as common as lower extremity replacements, nor do shoulder prosthetics have the same wear test requirements as hip or knee prosthetics. They must adhere to ASTM guidelines that consider the dynamic kinematic biology of shoulder mechanics and how they must endure regular wear to treat severe fractures, joint problems, or arthritis effectively. ASTM F1378 specifies mechanical strength, range of motion, and surface finish requirements for the prosthesis.
Artificial shoulder prostheses must have exceptional performance that is demonstrated before it is accepted in clinical settings. For FDA approval, device manufacturers must provide empirical evidence that their prosthesis does not fail under normal axial loads in vitro. The testing methodology required falls under ASTM F1378.
This specification includes modular prostheses and can either be constrained, partially constrained, or unconstrained. However, devices intended for custom applications are not covered under ASTM F1378.
ASTM F1378: Testing Methods
Testing includes fatigue assessments, glenoid loosening and glenoid shear, and shoulder constraint evaluations. The unique biomechanics of the shoulder include joint stability, muscle balance, and coordination. Testing prostheses against in vitro elements such as balance, ligamentous restraint, joint geometry, and bone structure is essential to determine a design’s clinical viability.
In order to be considered for approval from the FDA, any prosthetic design must adhere to ASTM standards. F1378 establishes the mechanical properties of the implant in conjunction with supporting bone structure. This specification includes modular prostheses. However, devices intended for custom applications are not covered under ASTM F1378.
Some new implants are manufactured from alternative materials that have no clinical precedent. In these scenarios, shoulder prosthetics built with alternative materials must prove equivalency. The wear rates of this different material cannot exceed the current standard of CoCrMo alloy against UHMWPE under physiological load conditions.
Accurate in-vivo replication of a prosthetic’s range of motion and loading is achieved by using a tri-axial simulator of motion in conjunction with three variable loading axes. Unlike hip and knee replacements where the gait cycle controls loading profiles and motion, the range of motion and dynamics of shoulder prosthetics can vary widely due to the shoulder joint’s kinematic variability. Because of the variability, there is more choice in testing when it comes to profile selection. The selected testing profile should still replicate a clinically significant wear situation to assess and measure the shoulder prosthetic’s performance directly. No matter which loading profiles are utilized, they must all be tested within the same set of parameters and frequency established by ASTM F1378 specifications.
Working with Empirical Technologies Corp.
If you have a shoulder prosthetic device that you are preparing to submit to the FDA, ASTM F1378 mechanical testing is an essential step to seeking approval. Through a series of tests, the shoulder prosthetic’s performance will be examined thoroughly, allowing for the improvement of flaws or inefficient design features.
At Empirical Technologies Corp, we have significant expertise in shoulder prosthetic testing. We years of experience helping businesses and individuals take their prosthetic design to the final stage. Our expert engineering and testing team has the resources and knowledge to preserve ideal testing conditions from start to finish. Contact us today to request an estimate, and learn how partnering with Empirical Technologies Corp can help you meet your goals.
Please refer to the ASTM website for the most up to date information on ASTM F1378 or visit our Quality Standards page for more information on our offerings.