BB&T Contributing Editor

MONTREAL - The Global Symposium on Motion Preservation Technology was held here in May, sponsored by the Spine Arthroplasty Society (North Palm Beach, Florida). Its 1,600 attendees came from 33 countries, about half of them from the U.S.

Degenerative disc disease is a common disorder that causes chronic back pain. There are currently very few surgical procedures available to relieve discomfort from severe back pain while preserving spinal motion. It is estimated that 80% of the U.S. population will experience at least one episode of significant pain as a result of disc herniations or other spinal problems in their lifetime.

Dynamic stabilization is emerging as an alternative to spinal fusion for the treatment of symptomatic degenerative disc disease. Dynamic stabilization instrumentation is designed to provide stabilization and controlled motion with the ultimate goal of reducing the incidence of adjacent level degeneration often associated with fusion.

There is growing interest in endoscopic spine surgery as improvements are made in the design of endoscopes and in surgical technique. The ability to visualize and treat patho-anatomy using an endoscope has opened the door for foraminal access to the lumbar spine from T-10 to S-1. This was the subject of a poster presented by Drs. Anthony Yeung and Christopher Yeung from the Arizona Institute for Minimally Invasive Spine Care (Phoenix). Dr. Martin Knight heads the Spinal Foundation (Oldham, UK) and is a pioneer and strong advocate of keyhole spinal surgery. Most of his procedures are performed on patients with failed back surgery, which he treats endoscopically and claims to have a high success rate.

The recent decision by the Centers for Medicare & Medicaid Services (CMS; Baltimore) to reimburse the Charite lumbar artificial disc from DePuy Spine (Raynham, Massachusetts) has given a big boost of encouragement for developers of related products.

Dynamic stabilization devices & artificial discs

Applied Spine Technologies (New Haven, Connecticut) has begun recruiting clinical investigators in the U.S. for its Stabilimax NZ spinal motion preservation system. It is a dynamic pedicle screw-based motion preservation system that is designed to support the spine while preserving motion and flexibility. Its pedicle screw vertebral anchors are attached to a mechanism with flexible joints.

Cervitech (Rockaway, New Jersey) is clinically testing in 20 sites in the U.S. its porous-coated motion artificial cervical disc. The product is being sold in 24 international markets. The device is a two-part cobalt chrome and ultra-high molecular weight polyethylene semi-constrained total disc replacement. It features a double layer of a titanium porous coating with an additional outer la yer of calcium phosphate for rapid bone ingrowth.

Large and anatomically designed cobalt chrome endplates are shaped to maximize loading in the more dense lateral vertebral surfaces to allow for translational motion in an arc consistent with the natural motion of the cervical spine segment.

St. Francis Medical Technologies (Alameda, California) received FDA marketing clearance for its X Stop interspinous process decompression system, the first non-fusion treatment for lumbar spinal stenosis.

An alternative to laminectomy, it is implanted using a minimally invasive surgical procedure in which the X Stop device is placed between the spinous processes of the symptomatic disc levels, without fixation to bones or ligaments.

Impliant (Milford, Connecticut/Ramat Poleg, Israel) is clinically evaluating its TOPS system, a posterior motion preservation system, as an alternative to spinal fusion. The device is comprised of titanium plates and an articulating polyurethane construct.

TOPS is designed for use following decompression to stabilize, but not fuse, the affected vertebral level to alleviate pain. It is intended for patients with lower back pain and sciatica with or without spinal claudication who have not achieved relief with prior conservative care.

Outcome data was presented at the conference on 20 patients, including one-year follow-up data on five, who received the TOPS system for the treatment of facet arthrosis, spondylolisthesis and spinal stenosis. The data showed that the device is effective in alleviating pain stemming from the degeneration of the posterior elements of the spine.

Vertebron (Stratford, Connecticut) is developing motion preservation implant systems that offer intra-operative flexibility regarding the degree of constraint and range of motion. Its cervical artificial disc has a cobalt chrome articulating surface with titanium endplates that is coated with hydroxyapatite for bony ingrowth and added implant stability.

The company plans to initiate clinical trials on this device in South Africa by the end of the year. Vertebron markets demineralized allografts and has recently obtained worldwide distribution rights from medArtis (Basel, Switzerland) for tricalcium phosphate and hydroxyapatite synthetic bone graft materials.

LDR Spine (Austin, Texas), a subsidiary of LDR Medical (Troyes, France), markets internationally a line of fusion and non-fusion products. They have been used in clinical trials in 1,400 patients and include the one- and two-level Mobi-C artificial cervical disc with mobile insert and the Mobidisc artificial lumbar disc with mobile insert.

The company’s fusion products are the Easyspine thoracic and lumbar spine posterior osteosynthesis system for posterior-lateral loading and integrated polyaxial locking, the MC+ cervical modular cage for fusion of a cervical spine segment using an anterior approach, and the ROI open radio transparent intersomatic implant used in degenerative lumbar spinal surgery.

N Spine (San Diego) is developing NFlex, a posterior dynamic fixation device that provide greater physiologic motion than currently available products. Tests on bovine lumbar spines were presented in a poster which showed that the device allowed greater motion than after rigid fixation. Clinical trials have not yet begun.

Nexgen Spine (Whippany, New Jersey) is developing the Physio-L lumbar disc. It is made from elastomeric polycarbonate polyurethanes and closely reproduces the mechanical properties and the normal motion of the natural disc, and provides shock absorption. Clinical trials are planned for later this year.

NuVasive (San Diego) is in clinical trials in the UK for its Neodisc cervical nucleus replacement device, which it acquired last year from Pearsalls (Taunton, UK). It is comprised of a silicone elastic core surrounded by an outer jacket made from polyester suture material.

Dr. Andre Jackowski of the Royal Orthopaedic Hospital (Birmingham, UK) reported from early clinical results that the Neodisc is simple to implant, is MRI-compatible, provides good pain relief and preserves a satisfactory range of motion. The company anticipates receiving CE mark approval for the device before obtaining FDA approval.

NuVasive featured its Maximum Access Surgery platform (MAS) platform, comprised of MaXcess minimally disruptive retractor system for direct visualization of the spine, NeuroVision nerve avoidance system for safe navigation around neural structures, and specialized implants. MAS enables new procedures such as XLIF, a minimally invasive spine surgery that accesses the spine through the side, rather than through the back.

NuVasive markets cervical and lumbar fusion products which include a sterile saline packaged allograft with color-coded instrumentation, a dynamic cervical plate system and a titanium surgical mesh. The company has the CE mark for fusion cages but they are not yet being sold.

A Total Facet Arthroplasty System (TFAS) from Archus Orthopedics (Redmond, Washington) was the subject of an 11-patient study at the Florida Spine Institute (Clearwater, Florida). Early data suggests that this articulating joint prosthesis successfully restores stability and range of motion to a functional spine unit with corresponding clinical improvement.

Paradigm Spine (New York) recently received an investigational device exemption (IDE) from the FDA for initiating clinical trials of its coflex posterior non-fusion interspinous dynamically-functional implant. The study will involve 450 patients with lumbar spinal stenosis and will compare the coflex device with pedicle screw fusion, the current standard of care.

The coflex device is a U-shaped titanium alloy available in five sizes and is indicated for use in patients with radiographically confirmed moderate-to-severe stenosis .

Facet Solutions (Logan, Utah) is developing implants and instrumentation for performing facet joint arthroplasty. The company recently was granted an IDE approval by the FDA for its anatomic facet replacement system and will be conducting clinical trials in the U.S. and Europe.

Its device provides patients with lumbar spinal stenosis and facet degeneration with a motion preserving alternative to spinal fusion. By reconstructing normal facet anatomy, physiologic motion is restored and pain is alleviated.

Spinal Kinetics (Redwood City, California) presented a poster on a finite element analysis of cervical total disc arthroplasty as an alternative for the management of cervical disc herniation or degeneration. Similar results were found in all modes of motion.

The issue of posterior disc replacement versus anterior disc replacement was the subject of a limited survey conducted by Biomedical Business & Technology among 15 spinal and neurosurgeons and the leading marketers of spinal implants. The opinions expressed by physicians were split, with some favoring posterior and others anterior surgical procedures. However, the industry executives queried overwhelmingly viewed posterior disc replacement as having an advantage over anterior disc replacement.

Nucleus replacement products

The nucleus pulposus is surrounded by fibrous tissue (annulus) and is located in the center of the vertebral disc It is composed of a gelatinous substance that serves as a cushion for the spinal column. If it herniates through the annulus, it may be removed by discectomy.

Several companies are developing synthetic nucleus pulposus replacement materials and were reviewed in a session on intradiscal repair. Nucleus replacement products offer an alternative to spinal fusion by preserving disc anatomy and restoring stability and motion to the spine.

Raymedica (Minneapolis) presented interim clinical results for its redesigned PDN-SOLO prosthetic disc nucleus. The study was conducted on 67 patients with degenerative disc disease, of which 63% reported improvement in pain.

The device is composed of a hydrogel core in a flexible, inelastic, woven polyethylene jacket. The hydrogel undergoes a cyclic swelling and shrinking, depending on the load. The PDN-SOLO is marketed outside the U.S. The company also introduced its redesigned HydraFlex nucleus arthroplasty system.

Spine Wave (Shelton, Connecticut) is developing products for nucleus replacement, compression fracture repair and spinal fusion. Its NuCore injectable protein-based nucleus replacement and augmentation material is based on patented tissue adhesive technology from its collaborative partner, Protein Polymer Technologies (San Diego). It cures rapidly into a tissue-adhesive gel when injected into the disc nuclear space. A bolus is injected that is larger than the surgical entry site and forms a mechanical barrier to extrusion.

The company received an IDE from the FDA in February and has initiated a pilot clinical trial of NuCore in the U.S. for the indications of microdiscectomy. A second pilot trial studying degenerative disc disease is expected to begin in mid-year.

Spine Wave’s StaXx XD expandable device recently received FDA 510(k) clearance, and the company expects to build a sales force and initiate beta site sales in the U.S. this summer. Its StaXx FX fracture repair system is being studied clinically outside the U.S.

TranS1 (Wilmington, North Carolina) is developing an axial lumbar percutaneous access nucleus replacement (PNR) device for degenerative disc disease. The in situ curing silicone is implanted using the company’s presacral percutaneous access technique that allows for motion preservation without disruption of vital soft tissue structures.

Investigators from Santa Rita Hospital (Sao Paulo, Brazil) reported on a 15-patient study of the PNR implant and found that it provides a robust discectomy and relief of pain without compromising the abdomen or paraspinal soft tissues.

The company’s axial lumbar interbody fusion (AxiaLIF) system enables lumbar fusion to be performed with complete preservation of the disc annulus and all the paraspinal soft tissue structures. It was approved in the U.S. in January 2005 and also has the CE mark. It has been used in more than 500 patients, with less than a 15-patient complication rate.

Replication Medical (Cranbury, New Jersey) presented a review paper of its NeuDisc anisotropic synthetic hydrogel for nucleus replacement that is currently under clinical investigation by Dr. Anthony Yeung at the Arizona Institute for Minimally Invasive Spine Care. It is comprised of a hydrolyzed polyacrylonitrile hydrogel that is pre-formed and requires no mixing or polymerization steps at the time of surgical introduction. The hydrated elliptically shaped implant closely approximates the size and shape of the nuclear cavity.

Disc Dynamics (Eden Prairie, Minnesota) presented two-year data from the clinical trials of its Dascor disc arthroplasty system, a nucleus replacement for the lumbar spine that is designed to relieve pain and restore function. The device is delivered under controlled pressure via an injection pump and cures in situ. The polyurethane polymer fills the void left by removal of the nuclear material. Its disc has CE mark approval but is not yet approved for sale in the U.S.

Cryolife (Kennesaw, Georgia) presented at a workshop its BioDisc nucleus pulposus replacement product that is undergoing clinical evaluation by Dr. Douglas Wardlaw at Woodend Hospital (Aber-deen, Scotland). BioDisc comprises an in situ polymerizing protein hydrogel.

Pioneer Surgical Technology (Marquette, Michigan) filed an IDE with the FDA for its Nubac disc arthroplasty system, an artificial nucleus device implanted by a minimally invasive procedure using a lateral approach for treating discogenic back pain. The product has a CE mark and the company plans to soon begin selling the implant in Europe.

Surgical adhesion barrier and mesh products

FzioMed (San Luis Obispo, California) featured its Oxiplex, an absorbable gel for use in preventing perivascular adhesions in artificial disc surgery. One of the risks in revision surgery is the possibility of perivascular adhesion formation after the first surgery. The gel consists of carboxymethylcellulose and polyethylene oxide. It was developed to reduce the formation of epidural post-surgical adhesions following laminectomies and laminotomies. The product is in clinical trials in the U.S. but is being sold internationally by DePuy Spine, a Johnson & Johnson (New Brunswick, New Jersey) company, and Medtronic Sofamor Danek (Memphis , Tennessee).

Anulex Technologies (Minnetonka, Minnesota) displayed its Inclose surgical mesh for use as a barrier in soft tissue repair of the annulus in patients undergoing spinal discectomy surgery for a herniated disc. Inclose is fabricated from polyethylene terephthalate.

Spinal surgery guidance system

Mazor Surgical Technologies (Caesarea, Israel) has developed SpineAssist, a miniature robotic spinal surgery guidance system for a growing spectrum of spinal surgeries that demand great skill and precision.

The company introduced version 4 at the Spine Arthroplasty Society meeting. The upgrade significantly minimizes the amount of fluoroscopy radiation exposure required for minimally invasive lumbar surgeries and other new features that enhance speed, precision and power. This represents a 50% improvement over the limited X-ray exposure required by the previous SpineAssist Guidance system, which was introduced into the U.S. earlier this year.