Clinical Study of the Valeo OL Interbody Fusion Device for Posterior Lumbar Interbody fusion versus PEEK: the Silicon Nitride and PEEK (SNAP) trial.

Fusion cages have become popular for use in interbody fusion procedures1.
These devices are strong enough to provide mechanical support for the normal
axial loads borne by the spine. They are also often used to restore the height
of the disc space and are generally designed to contain the bone graft which
encourages fusion of the adjacent vertebrae. Initially, fusion cages were
implanted in pairs via the traditional posterior lumbar interbody fusion (PLIF)
technique, but more recently, a single oblique cage has been used2;3.
Cages were originally titanium alloy but in the last ten years have more often
been made from polyetheretherketone (PEEK) plastic. PEEK is relatively inert,
and does not provoke a strong foreign body reaction in the body, generally
being surrounded by a thin fibrous tissue capsule4. In literature PEEK cages
have reported to promote spinal interbody fusion with high fusion rates and
have shown good to excellent clinical outcomes compared to other cages
26;27;28. These results confirm the safety and superiority of PEEK cages. They
are often used as the standard cages in interbody fusion procedures. PEEK is
invisible on x-ray and CT scan5; in order to be able to visualize the cages
during and after the procedure, radio-opaque metal markers are drilled or
molded into the cages. PEEK cages have an advantage over the earlier metal
cages: they do not cause artifacts on CT or MR scans. Follow-up imaging is
often important to determine the cause of ongoing symptoms and/or to verify
that fusion has occurred.

Silicon nitride, Si3Ni4, is a ceramic material with a compression strength
exceeding the plastic and metal materials used as interbody fusion spacers.
Unlike many ceramics, silicon nitride resists brittle fractures; its toughness
exceeds that of alumina, a material with 30+ years of use in joint
replacements7. Silicon nitride is highly compatible with standard spinal
imaging techniques. The material produces no artifacts on x-ray, CT or MR
images8. Several studies have demonstrated the biocompatibility of silicon
nitride9-11. One case report showed good clinical and radiological results in 2
patients one year after a transforaminal lumbar interbody fusion procedure with
use of the Si3Ni4 Valeo TL implant 29. An abstract presented at the 7th World
Biomaterials Congress in May 2004 demonstrated the results of a 10 year
follow-up of a clinical study in which 30 patients underwent anterior interbody
fusion of the lower spine using silicon nitride intervertebral spacers. They
showed a maintainence of interbody fusion in all cases after 10 years30.
Amedica Corporation has been manufacturing orthopedic implants from silicon
nitride for several years, and received the CE Mark and FDA marketing clearance
for its use as interbody spacers in 2008.

Primary Objective
The primary objective is to show that fusion with the Valeo OL spacer produces
similar improvement in MRDQ at all follow-up time points as compared to the
same procedure with PEEK cages.

Secondary Objectives
To show that the fusion rate of Valeo OL patients is similar to the fusion rate
of PEEK cages at 3 months, 6 months, 12 months and 24 months and to show that
Valeo OL shows more bone inside the cages at 12 month based on CT images.

This research project will be conducted on a prospective, randomized,
multicentre basis with a 2-year longitudinal follow-up with repeated
measurement analysis. Patient-recorded data will be entered by research nurses
or physicians who are blinded to the implant used.

All patients will be planned for spine surgery in which the Valeo or the PEEk
cage is used. Patient will be followed for 2-years (3 months, 6 months, 12
months and 24 months) for CT scans and to complete all te required
questionnaires. (SF-36/ MRMDQ/ VAS backpain /VAS legcomplaints/ EQ-5D).

As with any surgery, there are serious risks. These include, but are not
limited to pain, infection, blood clots, blood loss, allergic reaction and even
death. Other risks and discomforts that could happen because of the procedures
are: disassembly, breakage, degradation, or displacement (migration) of the
implant; collapse of the implant or graft into the vertebrae; spinal
instability; a change in the curvature of the spine; vessel damage/bleeding;
nerve injuries; tears or hardening of the tissue surrounding the disc; dural
tears; paralysis or a continuation of pain; numbness; tingling; sensory loss or
spasms; cauda equina syndrome; scar formation; urinary control changes;
postoperative changes in the curvature of the spine; bone loss; loss of spinal
mobility or function; non-union or delayed union of the spinal bone; fracture
or microfracture of the spinal bone or the bone graft material; sexual
dysfunction; development of respiratory problems (e.g. pulmonary embolism,
bronchitis, pneumonia, etc); change in mental status and death.
Risks associated with the use of allograft include but are not limited to:
failure of graft material resulting in nonunion; and allergic reaction to the
antibiotics or chemicals used during processing.
It is possible that the surgery will not reduce or relieve symptoms, and the
treatment may not result in therapeutic or direct health benefits. This cannot
be predicted for either the SiN or the PEEK implant. If the study implant does
not relieve symptoms or if there is a problem with the device, it is usually
possible to have it removed. This would require another surgery.
This research study involves additional exposure to radiation. The subject will
receive 3-5 mSv from the CT scan of the lumbar spine done after 12 months, and
1.5 mSv form each RSA visit done at baseline, 3, 6, 12 and 24 months. The
amount of background radiation that people receive during the course of their
daily lives is 3 mSv per year. Those that participate in this study will
receive approximately 3 times the average yearly dose over the course of 2
years.

In addition to the general risks of spine surgery, there are specific potential
risks associated with the use of the Valeo OL spacer: implant migration or
subsidence, implant fracture, and pseudarthrosis (fusion failure).
The potential benefits of PLIF procedures include the potential to dramatically
improve the patient*s quality of life by reducing back pain. The fusion
procedure also offers the possibility to stop the progression of
spondylolisthesis, preventing an increase in disability. The level of
potential improvement is also related to pre-existing medical conditions.