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Magnesium carries a great deal of potential in orthopedic applications. The inorganic element is naturally present in human tissue, so magnesium-based implants exhibit excellent biocompatible properties. They also possess high levels of mechanical strength and flexibility in design.
Drew Diaz, Bone Solutions CEO, said about 60% of magnesium in the body is stored in bone, and that it plays a significant role as a signaling agent for osteoblast activity. “Significant new bone forms around the implant site as a result of that signaling process and occurs through creeping substitution,” he explained.
Bone Solutions is one company that’s focused on developing magnesium-based orthopedic products that are not highly porous, so they don’t act like traditional scaffolds. Instead, they retain their structural integrity throughout the absorption process.
In February 2024, Bone Solutions received FDA 510(k) clearance to market OSTEOCRETE, a magnesium-based bone filler for use in the intervertebral body disc space during cervical, thoracic and lumbar fusion procedures. It was the first magnesium-based bone substitute to be cleared by FDA for this application. OSTEOCRETE has a compressive strength of 36 MPa and consistently remodels bone, even in challenging patient cases.
Diaz highlighted recently released clinical data that showed OSTEOCRETE’s torque-to-failure at four days is 58% higher than any comparable product on the market, including calcium-based cements, when used to augment pedicle screws or metal implants. He also noted that the bonding characteristics of OSTEOCRETE results in a pull-out strength at time zero — 14 minutes after placement — approximately 50% higher compared to using no augmentation or using calcium phosphate.
Bone Solutions is now using OSTEOCRETE’s base formula to introduce OSTEOPINS resorbable implants that can be 3D-printed or injection molded later this year. The 2.0mm and 4.0mm pins can be used for bone alignment and screws and anchors designed for various orthopedic applications.
The performance profile of the pins is strong, according to Diaz, who said they show resorption between 14 and 16 months, depending on anatomical location, patient health condition and the size of the implant.
Bone Solutions is using the same OSTEOCRETE formulation to develop OSTEOENHANCE, a coating solution for titanium implants.
Bone Solutions continues to discover more about the bonding and adhesive characteristics of its magnesium-based material. “One of the key features is that, once placed at the surgical site, the material remains stable without any risk of migration or movement,” Diaz said.
Another important advantage is that, because the product contains no sulfates, it’s shown no evidence of heterotopic ossification.
“We know OSTEOCRETE resorbs as designed, and we know what it’s going to do inside the body,” Diaz said. “My vision is that one day we will be competing with hydroxyapatite and other types of coatings in partnerships with strategics in the marketplace.”
Challenges Create Opportunities
Rob Ball, CEO of Magnesium Development Company (MDC), said there’s a clear demand in the orthopedic market for resorbable implants. MDC is developing headless compression screws for hallux valgus repair and humeral suture anchors for the shoulder. They received FDA’s Breakthrough Device designation for the screw in 2022.
Ball believes the challenges associated with current materials lie in mechanical performance in terms of strength, toughness and elongation, which affect how the material behaves under stress, and biocompatibility in terms of the way materials trigger inflammatory responses.
“Improving the mechanical properties of implant materials will likely improve device functionality and could expand the range of clinical applications,” Ball said. “And improving the body’s response to the materials creates a powerful one-two punch that could drive the development of a new generation of orthopedic implants.”
Mechanical strength is an inherent benefit of magnesium, but it also offers processing flexibility, which allows Ball’s team to tune the absorption profile and the mechanical strength of the material, depending on the application.
“That kind of tunability is incredibly valuable,” he said.
A common challenge that device engineers face when developing resorbable implants is related to insertion mechanics, which focus on the way devices are pushed, screwed or punched into place.
Ball explained that orthopedic device engineers are often limited by anatomical constraints, such as small bone structures, while simultaneously needing to account for dense cortical bone. That means enough material volume is needed to incorporate features like torsion resistance, which help seat the implant securely.
“If you’re working with polymers, those constraints can be limiting,” Ball said. “But with magnesium’s higher mechanical performance, you can maintain the necessary functionality with a smaller device footprint. That’s a big advantage, particularly for delicate or anatomically tight indications.”
Formula for Success
Magnesium boasts several properties that make it appealing, but Diaz said the formulation of the material matters most. “Using it successfully depends on how it’s blended, mixed and milled,” he said. “Each of these steps is critical to ensuring proper bone recall and resorption. It’s a highly specific and refined process.”
Ball noted that magnesium is not a one-size-fits-all material. “There’s a degree of specificity required in terms of the elemental composition and processing of the raw material, which directly impacts its mechanical properties, resorption profile and the body’s biological response,” he said.
Selecting the most effective magnesium composition therefore requires carefully matching the formulation and processing to the intended clinical application. For instance, magnesium behaves differently when used in cancellous bone versus cortical bone. The material also exhibits notable differences based on the type of tissue with which it interacts.
“These differences matter when designing implants for optimal performance in a given indication,” Ball said.
Additionally, environmental factors — such as the type of fluid surrounding the material and its flow characteristics — influence magnesium’s behavior. For instance, the response will vary in areas with high vascularity or exposure to synovial fluid, which must be accounted for in the design of devices.
The absorption of magnesium-based devices is fundamentally different. For example, Ball said, a cannulated pin will absorb fluid much faster than a non-cannulated pin. Understanding this difference is particularly important when designing magnesium devices, which release hydrogen during absorption.
“The body must manage the hydrogen released as the material degrades,” Ball said. “In some environments, the body handles this process effectively, while in others, it may struggle to manage the release efficiently. The thought process for designing magnesium-based implants therefore needs to differ from that of polymer-based devices.”
When considering the design of basic orthopedic devices like plates, screws and suture anchors, Ball said substantial work is needed from an evidentiary standpoint to prove that the potential benefits of magnesium outweigh the risks.
He noted that, unlike standard materials like titanium and cobalt chrome, there is no regulatory standard for the use of magnesium in the production of orthopedic implants. Each formulation of magnesium is different, so FDA requires clinical evidence to support the way the material responds in the body for individual applications.
“The key takeaway is that magnesium formulations that include elemental composition and mechanical properties must be managed carefully,” Ball said. “That also applies to the manufacturing method of the raw material.”
Proof Positive
Polymer-based devices typically absorb via hydrolysis, during which water breaks down the molecular chain and reduces its molecular weight.
“This leads to a relatively steady drop-off in mechanical properties until a certain threshold is reached, after which the properties degrade much more rapidly,” Ball said. “There will be continued demand for clinical evidence to support new formulations.
“Ultimately, each company that produces magnesium-based devices will need to conduct its own research and gather evidence to prove their safety and efficacy.”
