Medical Device Daily

The majority of the 30 million U.S. patients who report back pain each year usually resolve the problem with conservative treatments or just good old-fashioned rest — or a combination therof. But roughly 4.5 million fail these types of treatments and only 500,000 will commit to surgery.

The bad news extrapolated from this data: a population of around 4 million people who have to live with some type of chronic back pain.

The good news: help is possibly on the way in the form of a new spine stabilization device.

The FDA, under its Investigational Device Exemption protocol, has granted Applied Spine Technologies (AST; New Haven, Connecticut) permission to commence a multi-center, randomized, controlled clinical trial comparing posterior dynamic stabilization using the company’s Stabilimax NZ dynamic spine stabilization system to patients receiving traditional fusion stabilization to treat degenerative lumbar spinal stenosis.

The study will enroll a total of 266 Stabilimax NZ patients and 133 control patients, and is expected to start this month at 20 sites across the U.S.

The underlying premise of the Stabilimax NZ — the NZ for “neutral zone” — is that painful spine motion increases in the injured spine, and this abnormal motion is most pronounced in what is termed the neutral zone

“The device shrinks the neutral zone to normal, but allows for a free range of motion,” Thomas Wood, AST’s president/CEO told Medical Device Daily. “It adds stability without eliminating motion with a therapy which is less invasive than fusion or disk replacement. It is laterally inserted between the muscle plains and then anchored in place through pedicle fixation.”

The device requires no bone graft, site preparation, or harvesting from the patient.

The company defines this neutral zone as an “area of laxity” in the center portion of the spine’s range of motion, and increased laxity in this area can result in a range of problems.

To correct this, the Stabilimax uses a dual-spring mechanism with a feature that maximizes stiffness and support in the neutral zone, where the spine needs it most, thus serving to return the neutral zone to its normal, limited range, according to the company. The device uses traditional pedicle screw vertical anchors; but, unlike other implant systems, they are attached to the bone using two flexible joints.

The “give” allowed by the dual springs creates proper spine stabilization (with limited range of motion), and also reduces stress on the pedicle screws, decreasing the potential for screw failure. By eliminating abnormal motion, the design of Stabilimax NZ is intended to alleviate abnormal loading on surrounding muscles and tissues.

The company reports that in Europe, a clinical trial of Stabilimax NZ is already underway, and Rudolf Bertagnoli, MD, one of the most experienced motion-preservation spine surgeons in the world, has thus far implanted patients successfully.

Of note, Wood told MDD that Stabilimax NZ has just recently received CE-mark approval.

AST says it expects the U.S. trial to last at least 18 months, given the number of patients enrolled in the study, before any endpoints — decreased pain and increased in motion — are tabulated. Then there is the usual two-year follow-up period before any filing with the FDA will be considered.

One aspect of the trial that Wood is excited about is the training process for surgeons.

He characterizes this process as “very similar to fusion techniques already in place. We will just use a slightly different screwdriver.” He added, “There will be a rapid adaptation rate, and minimal invasive procedure.” In other words, the Stabilimax NZ is designed to be user-friendly – the users in this case both patient and surgeon.

AST is clearly focused on avoiding damage to areas around the spine. It says that the ultimate goal of spine surgery should be minimal collateral damage to the surrounding muscles and tissues with maximum relief and benefit to the patient.

That relief is often ameliorated by the trauma of surgical access involved in fusion surgery and the required surgical access. Adjacent-level disease and spine fusion disease are the two main complications of fusion and are as much a part of fusion surgery as the implants themselves.

“It is well-known that fusion implants promote adjacent level disease (ALD), while fusion techniques promote spine fusion disease (SFD),” said spine surgeon Hansen Yuan, MD, chairman of AST’s scientific advisory board. “What’s exciting about AST’s Stabilimax NZ implantation via a minimally invasive technique is that it avoids both of the main complications of fusion.”

“The concept of motion preservation, including dynamic stabilization with Stabilimax NZ, has the purpose of preventing or minimizing ALD,” Yuan explained. “In addition, it has been recently demonstrated that the morbidity and sometimes permanent impairment of spine healing and function that is associated with the posterolateral fusion can be greatly reduced with minimally invasive surgical (MIS) techniques. For example, fusion techniques that place bone for fusion in an anterior cage and simply place pedicle screw hardware without bone graft via MIS posteriorly are effective in reducing spine fusion disease.”

The Stabilimax NZ is the brainchild of AST’S scientific founder, Dr. Manohar Panjabi.

Until his recent retirement, Panjabi was a professor of Orthopedics & Rehabilitation, as well as Mechanical Engineering, at Yale University School of Medicine. As director of Yale’s Biomechanics Research Laboratory, Panjabi established himself as a spine authority for his work on spinal joint function and its implications for motion-preserving implants.

The company was founded in February 2004 with Series A funding of $4 million from Oxford Bioscience Partners and BioVentures Investors. About a year ago it closed on a $15 million Series B round of financing led by InterWest Partners, with De Novo Ventures also participating.

Wood told MDD that AST “hopes to raise $25 million” over