Technology Breakthroughs in Spinal Implants

Despite—or perhaps because of—market saturation, spinal implant manufacturers continue to pursue product innovations. Frost & Sullivan has identified two paths along which future innovations in spinal implants—and indeed all of orthopedics—will be aligned: the use of stem cells and 3-D printing.

During its annual review of the global orthopedics industry in 2015, Frost & Sullivan valued the overall orthopedic implant market at $34 billion and projected it to be worth $38 billion this year. Of the 2015 total, spinal implants contributed an estimated $7.5 billion, or 22.3%, of the revenue. However, while overall orthopedics industry revenue was projected to increase at a compound annual growth rate of 3.3% between 2015 and 2021, the CAGR of the spinal implants segment during the same period was merely 1.7%.

Despite—or perhaps because of—market saturation, spinal implant manufacturers continue to pursue product innovations. There are a number of reasons for this. One is an ever-present demand for spinal implants due to an ageing population, which, incidentally, also necessitates longer implant life. Another driver has been the push, particularly in the United States, for the development of biomaterials with improved biocompatibility for better clinical outcomes.

The spinal implants market is broadly categorized into two product areas based on whether the implants are combined with bone grafts (fusion spinal implants) or not. Spinal implants are used to correct spinal deformities and stabilize and strengthen the spine. Some of the disorders treated using spinal implants are degenerative disc disease, scoliosis, kyphosis, spondylolisthesis and fracture.

Another classification—and a handy guide to track innovations in this space—is based on the material used to fabricate the implants. This creates three market segments:

Metallic Biomaterial Implants

The allure of biocompatible metals such as clinical-grade stainless steel, titanium and cobalt-based alloys has been due to the strength that they impart. Advances in metal implants include corrosion resistance, surface modification to make the implants bioactive, and increased porosity to provide space for revascularization and for osteocytes to grow. A particularly interesting class of metallic materials that has been researched for spinal implants is shape-memory alloys, sometimes referred to as smart metals. Alloys of nickel and titanium (NiTi) and copper-aluminum-nickel “remember” their shape at a specific temperature and return to that shape when the temperature is reached. OSSpine™ (DePuy Synthes) and 4Fusion (Stryker Corp.) are NiTi-based spinal implants cleared by the U.S. Food and Drug Administration (FDA).

Polymeric Implants

High-performance engineering polymers, most notably polyetheretherketone (PEEK), are used to manufacture lumbar and cervical spacers, screws and rods for spinal implants. Manufacturers favor PEEK’s properties that enable fine-tuning, biocompatibility, and compatibility with imaging modalities for post-operative diagnosis. With the advent of 3-D printing, the interest in polymeric implants has gone up, in the belief that it would be easy to custom-design implants based on patients’ specific needs.

In 2013, K7 Spine (Henderson, Nev.) brought the first-ever PEEK-based spinal implant into the market. The device was made using German materials major Evonik’s proprietary Vestakeep PEEK material. Within 4 years, the popularity of PEEK has increased tremendously, as evident from several FDA-cleared products in the market.

 Bioceramic Implants

The demand for spinal bone tissue replacements has fueled the emergence of bioceramics as excellent candidates for synthetic bones. Alumina and zirconia are popular bioinert ceramic materials that are increasingly used for spinal implants.  The current generation of bioceramics is known as bioactive materials, possessing the twin properties of bioactivity and biodegradability.  

Vitoss Bone Graft Substitute (Stryker Corp.) and Vitrium® (Bio2 Technologies, Inc.) are both made from novel resorbable orthobiomaterials, displaying properties of porosity, load bearing, bioactivity and osteoconductivity.

The Road Ahead

Frost & Sullivan has identified two paths along which future innovations in spinal implants—and indeed all of orthopedics—will be aligned: the use of stem cells and 3-D printing.

Stem cells are being researched for treating patients with complex neurological disabilities associated with spinal cord injuries. Belgium-based Bone Therapeutics is developing an allogenic, off-the-shelf cell therapy product for a variety of orthopedic indications, including spinal fusion procedures. The company’s product, ALLOB®, is in clinical trials. Despite regulatory hurdles, ethical concerns and difficulties in securing funding, companies and research organizations continue to hold stem cell-laden biomaterials in high regard.

3-D printing has already made its impact in the health care industry, enabling custom-designed stents, knee implants and airway splints. In the last few months, several 3-D-printed products have received regulatory clearance, and several more have been manufactured ad hoc, to provide life-saving options for patients. For instance, in February 2017, surgeons at the New Delhi-based hospital Medanta replaced a woman’s damaged vertebrae with a 3-D printed titanium implant. In June 2017, at least two companies—SI-BONE (San Jose, Calif.) and K2M, Inc. (Leesburg, Va.)—announced FDA clearance for their 3-D printed products. For SI-BONE, it was iFUSE-3D, a titanium implant for use in the sacroiliac joint, highlighted for enhanced porosity that resembles the natural surface of cancellous bones and believed be the appropriate environment for osteogenesis and ossification. K2M’s Mojave spinal lumbar cage is indicated to be used inside the body to help correct spinal defects.

A claim common to the surgery in New Delhi, the products released by SI-BONE and K2M, and several other innovations is the tag “first-ever.” Marketing claims aside, these cases may well be pointing to the fact that 3-D printing of spinal implants remains largely untapped, and several “firsts” are being achieved every day.

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