The biomaterial of next-gen spinal implants

Invibio looks at augmented biomaterial for the next generation of spinal implants. This includes regulatory clearances for PEEK- Optima HA Enhanced in the US and CE mark approval in Europe, plus encouraging pre-clinical study results and early clinical experience.

A wealth of research and clinical experience is confirming that the use of PEEK-Optima polymer-based spinal implants confers advantages that can, potentially, enhance the efficacy of spinal implants and improve patient outcomes. Combined data from three clinical studies that directly compared PEEK-Optima with titanium devices for cervical fusion showed fusion rates between 88-100% for PEEK-Optima versus 47-93% for titanium devices.1-3 The high-performing polymer was the first implantable PEEK and introduced by Invibio Biomaterial Solutions (Invibio) in 1999. Since that time the company has pioneered further innovations and supported its partner companies with pre-clinical study results and clinical outcome data to achieve regulatory clearances and to help educate the medical community.

One such recent PEEK-based innovation was Invibio´s PEEK-Optima HA Enhanced polymer. It combines PEEK-Optima polymer with hydroxyapatite (HA) for medical applications where bone on-growth is required.  Hydroxyapatite, a well-known osteoconductive material that enhances bone apposition and a constituent of human bone, is fully integrated, not coated, into the PEEK matrix, making it available on all surfaces of a finished device, which also eliminates the time and expense of applying coatings to the manufactured implant.

Invibio´s enhanced biomaterial offers all the clinical advantages of PEEK-Optima Natural, including a modulus close to that of human bone, reduced stress shielding, and artifact-free imaging, whether by X-ray, MRI or CT scanning, allowing clear visual assessment of the fusion mass. 

Pre-clinical studies demonstrate the potential benefits of PEEK-Optima HA Enhanced

The performance of PEEK-Optima HA Enhanced has been studied in pre-clinical studies, and has demonstrated a greater amount of new bone formation and a higher quality of new bone bridging, within early stages of treatment, compared with the results obtained when using PEEK-Optima Natural.

Invibio commissioned an independent cervical fusion study in sheep, to compare outcomes between interbody fusion devices composed of PEEK- Optima HA Enhanced, PEEK- Optima Natural and allograft bone. Results indicate that PEEK- Optima HA Enhanced may provide several advantages4:

  • Greater new bone formation. PEEK- Optima HA Enhanced resulted in greater new bone formation at six weeks, compared with PEEK- Optima Natural.
  • Higher quality new bone bridging. PEEK- Optima HA Enhanced provided a more favorable environment, with higher quality local bone at six and 12 weeks compared with PEEK-OPTIMA Natural.
  • Enhanced mechanical performance. PEEK- Optima HA Enhanced devices outperformed allograft, with fracture of the allograft devices in 6/13 (46%) instances.

A previous study had evaluated and compared the bone ongrowth that resulted from the use of the two implantable polymers in a bone defect model in sheep, and revealed that PEEK- Optima HA Enhanced resulted in approximately 75% direct bone apposition as early as four weeks following implantation compared with PEEK- Optima Natural.5

Early clinical experience with the novel material combination

A nine-patient case series was presented at the North American Spine Society (NASS) Annual Meeting in October 2016. These patients, male and female, were aged 39-76 and had varying levels of health, including pre-existing diseases or conditions, and experience of previous surgery.6 Patients also had various combinations of leg pain, cramping and weakness, and back pain necessitating lumbar fusion. All patients underwent a one- or two-level lumbar fusion utilising the same EVOS-HA Interbody device from Cutting Edge Spine, cage setup and pure iliac crest bone graft. The interbody fusion device used was made with PEEK- Optima HA Enhanced polymer. Anteroposterior and lateral X-rays were taken at six and twelve weeks post-op and CT scans at six months post-op.

At six months, post-op CT scans revealed solid fusion for eight of nine patients, with solid fusion at one year for a patient with a history of heart problems and smoking. One-year radiographs indicated solid fusion in all patients. There were no neurologic sequelae.

Highlights of the important clinical results presented included:

  • More than 50% back pain reduction
  • Nearly all leg pain resolved
  • No instrumentation failures
  • No reoperations

Timothy Bassett, MD, SouthEastern Spine Specialists, who assessed the patients' progress and outcomes concluded: "PEEK- Optima HA Enhanced polymer shows exciting potential for use in spinal lumbar fusions. In all nine cases, the PEEK- Optima HA Enhanced Interbody Fusion Device exhibited rapid bone fusion in the interbody region and very dense bone growth around the implant as early as six weeks, typically unseen with unfilled PEEK.

"As a result of PEEK- Optima HA Enhanced's quick bond, patients are less likely to require anterior posterior reconstructions and can return to everyday function and exercise regimes sooner and with greater confidence."

Brad Prybis, MD, Carrollton Orthopaedic Clinic, Carrollton, reported on an eight-patient case series that tested whether PEEK- Optima HA Enhanced provides better bony on-growth and fusion: "I observed pain and neurologic function and took anteroposterior, lateral and flexion extension radiographs at six months post-op."7

Patients included males and females aged 43-66 with chronic neck, arm, hand and finger pain, numbness and weakness. Some patients also reported loss of control, coordination and balance in the affected areas. Diagnoses included various levels and combinations of cervical radiculopathy, cervical myelopathy, myeloradiculopathy, central stenosis with spinal cord impingement, foramenal stenosis, and chronic pain.

All patients underwent a two-level Anterior Cervical Discectomy and Fusion (ACDF) with a device made with PEEK- Optima HA Enhanced. As part of this procedure, Dr. Prybis utilized a high-speed burr to maintain good bone-cage contact and some endplate bleed, when preparing the endplates for a PEEK- Optima HA Enhanced spacer.

Radiographic Fusion Results:

  • Six-month, post-op follow-up showed solid fusion at 17 of the 17 levels.

Neurologic Function Results:

  • Improved neurologic function in all 8 patients
  • Residual numbness in 3 of 8 patients
  • Residual weakness in 1 of 8 patients

Clinical Results:

  • Arm pain resolved in all 8 patients
  • Neck pain resolved in 5 of 8 patients
  • Neck pain improved in 7 of 8 patients
  • Neck pain unresolved in 1 patient

Dr. Prybis concludes: "All eight cases utilizing the HA enhanced devices provided as good or better clinical and radiographic results than traditional PEEK Interbody Fusion Devices. Patients healed quicker and could return to normal activity after only two weeks. I’m convinced that HA integration does make a big difference in clinical outcomes."

Regulatory approvals carry PEEK- Optima HA Enhanced to market

Increasingly, PEEK- Optima HA Enhanced is being granted regulatory clearance and CE mark approval for entry into the medical device markets in both the US and Europe, respectively.

In 2017, the potential advantages of PEEK-OPTIMA HA Enhanced devices were highlighted when Innovasis was the first company to receive FDA 510(k) clearance for a standalone ALIF (anterior lumbar interbody fusion) system made from the polymer. This system is an intervertebral fusion device for use in patients with degenerative disc disease (DDD) at one or two contiguous levels of the lumbar spine (L2-S1). Used to facilitate fusion in the lumbar spine and inserted using an anterior lumbar interbody fusion (ALIF) procedure, the device meets all the surgical requirements of implant stability (anti-migration), ease of implantation, and straightforward assessment of the fusion process

Previously, in 2015, the Atlanta, GA-based Meditech Spine received (FDA) 510(k) clearance for the next generation Talos line of cervical intervertebral fusion devices, made from PEEK- Optima HA Enhanced. These Talos-C (HA) Cervical Intervertebral Body Fusion (IBF) devices take the form of cages intended for use in skeletally mature patients with Degenerative Disc Disease (DDD) of the cervical spine at one level from C2-T1.

The selection of the biomaterial was made after looking extensively at the PEEK- Optima HA Enhanced data, and after discussing its characteristics with many surgeons. Research helped steer the decision at Meditech Spine to add the enhanced polymer to the company's product portfolio since it gives surgeons and their patients the best of both worlds: PEEK- Optima, a proven polymer with a modulus of elasticity close to human bone, plus HA, a material known to enhance and accelerate bone on-growth.

PEEK- Optima implants poised for rapid uptake

For over 15 years, Invibio's PEEK- Optima Natural polymer has delivered convincing results as a biomaterial for surgical implants. The addition of hydroxyapatite (HA) to form Invibio's PEEK- Optima HA Enhanced allows all the advantages of PEEK- Optima Natural to be retained by spinal implants, but with HA exposed on all surfaces of the device, for enhanced bone apposition. Pre-clinical and clinical outcome data indicate that there is the potential to accelerate the fusion and healing processes, while enhancing the quality and density of new bone on-growth. These results indicate a potential for improved patient outcomes, with all that implies for an improved quality of life. An increased number of regulatory clearances in the US and CE mark approvals in Europe will help to ensure that innovative devices made from PEEK- Optima HA Enhanced achieve quick and effective market up-take.