Articulating Total Wrist Implants
Movement that occurs in the wrist joints includes abduction, flexion, and extension adduction. Unlike the hip or knee, the wrist is a complex joint that implants can mimic through careful testing of their implant designs so that they can be approved for use in clinical settings.
The articular cartilage of the joint can wear out or accumulate damage, leading to conditions such as rheumatoid arthritis, osteoarthritis, infection, and injury. Total wrist implants are used in wrist arthroplasty to create a pain-free and stable joint that has a functional movement range. Implants must be able to pass specific standards to ensure their in vitro performance can withstand kinematic and dynamic forces of regular activity. A wrist implant lasts between 10-15 years and is a non-weight bearing joint, meaning that it must be designed for the specific kinematic environment of its implantation location.
ASTM F1357 provides specifications for total wrist implants with radial carpal components with articulation function. This standard does not cover one-piece elastomeric implants, custom application implants, and implants with porous or ceramic coated surfaces. Constrained, partially constrained, and unconstrained joint implants are covered by ASTM F1357.
The testing guidelines established by ASTM F1357 include testing for wear, range of motion, in vitro laboratory assessments, and polymeric creep testing, also known as cold flow. Cast metallic implants are radiographed, and metallic implants undergo fluorescent penetrant inspection.
Total Wrist Implant Articulation
ASTM F1357 sets a guideline of the provisionary physical characteristics of total wrist replacements for manufacturers that are seeking approval for their prototype for clinical use. They are intended for use in patients with a fully matured skeletal structure. They must be fit for the imposition of dynamic loads, corrosive environments, and at bearing surfaces must attain continuous motion.
Artificial wrist prostheses have two primary components: the radial component and the distal component. The radial component is made of two pieces: a stemmed flat metal component with attachment capabilities in the bone canal and a fitted plastic cup on the metal piece, which forms a socket.
The distal component mimics the function of small wrist bones. This globe-shaped component is made of metal and designed to fit the plastic socket. Two metal stems attach the distal component through hollow bone marrow cavities of metacarpal and carpal bones of the hand. The curvature of the natural wrist is established through the ellipsoidal head, which provides functional and natural wrist movement.
ASTM F1357 further specifies the specific materials used to manufacture total wrist implants, which include:
- Unalloyed titanium
- Wrought cobalt-20chromium-15tungsten-10nickel alloy
- Cobalt-28chromium-6molybdenum alloy
- Wrought titanium-6aluminum-4vanadium extra low interstitial alloy
- Wrought cobalt-20nickel-20chromium-3.5molybdenum-3.5tungsten-5iron
- Wrought 35cobalt-35nickel-20chromiu-10molybdenum alloy
Range-of-motion data of the device will be collected as well, along with other performance considerations, dimensions, component performance, and finish and markings of the prosthetic.
Working with Empirical Technologies Corp.
Empirical Technologies Corp. is available to assist in testing your device, according to ASTM F1357 specifications. Our trusted team of engineers has years of experience in providing meticulous testing for prosthetic devices, and we have helped individuals and businesses alike through the process of seeking FDA approval.
ASTM F1357 requires stringent specifications, which can be hard to account for without the help of professionals who are industry veterans in prosthetic standards testing. We have the expertise needed to accomplish these technical and detail-oriented goals and will advise you on how to modify the prototype should that be deemed necessary. Contact us today and request an estimate for testing for your prototype.
Please refer to the ASTM website for the most up to date information on ASTM F1357 or visit our Quality Standards page for more information on our offerings.