In 2005 the most definitive modern textbook on
spinal instrumentation and surgical techniques was
published by Thieme. The 135th Chapter by Ray
and Jenny documented the clinical role of the Ray
cage in regard to spinal instrumentation.
The key word regarding this presentation is
the term "standalone." When first given full
market approval by the FDA on
September 23, 1996 the product labeling stated that titanium
cages were
approved for use as posterior interbody "standalone" devices.
Initially the
recommendation was to use 2 cages but use of one cage was also
included in the FDA approval at that time. The pioneers of
standalone cages predicted that because of associated segmental
energy absorption
there would be a lesser incidence of the "transitional syndrome"
as a cause of surgical failure.
These are two level bilateral
standalone BAK cages. Ten years after surgery
they are well healed with "sentinal" bone
surrounding them. The CT image shows bone
growth through the windows of the cage.
Shown to the left is a discogram
being performed on a patient who had twin standalone
L5-S1 BAK cages (seen at the bottom) implanted 10
years previously who had developed some back pain.
The discogram at L4-5 showed only slight
degeneration while at L3-4 the pattern was normal.
This patient's pain was satisfactorily treated by
physical therapy alone.
In 1995 Tencer and associates published their
studies on different cage
implant configurations (shown below). Their observations,
confirmed by other published
studies and multi-surgeon clinical experience, including that of
the Editor clearly demonstrated the scientifically demonstrated efficacy of
"standalone" posterior interbody cages. Their
major attraction being less invasive surgery, lower morbidity,
less surgical time, and less surgical cost.
It is an unfortunate observation that the majority
of spine stabilizations performed in the U.S. today are for the
treatment of "low back pain" rather than for the treatment of
individuals with progressive neurologic deficits who require
adequate surgical decompression first and sensible spine
stabilization second. It is a rare circumstance when spine
surgeons agree on the type of surgery for the patient. It
is even rarer when a spine surgeon presents a patient with a
review of the many options available.
A standalone posterior interbody
cage is an important option for patients to know
about. Much like skyscrapers which are built
with some degree of flexibility single Ray titanium
cages have been shown to have as much as 5 degrees
of energy absorbing movement.
The modern discipline of "spine arthroplasty" is predicated
on the concept of maintaining some spine flexibility in order to
avoid post-operative stress on other body structures producing
progression of impairment.
