Also known as “Adjacent Segment Disease”
The continuing dilemma in spine care is that multi-level rigid spine fixation typically creates adjacent stress-related pathology of adjacent spinal segments as well as stress-related problems directed to the pelvis; often related to the sacro-iliac joint. These are commonly referred to as “transitional syndromes.” These problems are not infrequently create more patient disability than the problem for which the fusion was initially performed to address. Often the treatment of transitional syndromes require additional surgery.
In the example shown above a “rigid” front and back five level (L2 to the sacrum) instrumented fusion has been performed.
This extensive surgery involved both anterior (in this case using femoral ring allografts) as well as posterior surgical approaches with placement of segmental pedicle screws and rods. Autogenous bone was then harvested from the patient’s pelvic crest (ileum) and placed dorso-laterally.
The yellow dots are placed on the thickened and sclerotic end plates of the degenerated segment above this rigid stabilization. Because of the stress generated from the rigid instrumentation the L2-3 disc interspace has collapsed. This represents a typical example of the “transitional syndrome.” In this case the patient’s complaints were those of only back pain. The transitional syndrome can also produce leg and sacral nerve root problems due secondary to disc herniation as well as stenosis (central, spinal recess and lateral spinal). When a transitional syndrome causes neurologic impairment this may necessitate additional surgery and additional surgical stabilization.
Failure of a surgeon to explain to a patient the possibility of a their developing a transitional syndrome means that the surgeon has not provided the patient with adequate informed consent. Mother Nature has been kind enough to demonstrate this phenomenon as shown on the left. This is an example of a congenital block vertebrae in a young adult. Because the spine did not normally segment during fetal development (see green dot) inordinate stress has been placed on the adjacent intervertebral discs producing not only degeneration (see red dots) but has also created a discogenic pain syndrome.
This is an example of a post-surgical transitional syndrome following a rigid multi-level fusion involving the L3. L4 and L5 vertebrae. It can be noted on the far left that this patient has an underlying genomic spine disorder. At the transitional level (L1-2) significant segmental dysfunction has developed with reactive changes. Note also the development of lateral spinal stenosis at this segment.
The drawing to the left illustrates a case provided by Elmer Nix where the force exerted by the pedicle screws was sufficient to actually fracture the sacrum itself in a elderly patient with osteoporosis.
Sacral and pelvic fractures are uncommon complications of rigid instrumented fusion but this occurrence helps to provide important evidence regarding the high degree of non-physiologic stress and loading which is directed by rigid fusions upon adjacent body structures.
There can be no question but that rigid instrumented spine fusions can be, for the right patient, a truly beneficial endeavor. The patients least well served are those who have multi-level degenerative disc problems to start with. This is particularly true when “back pain“, as opposed to progressive neurologic impairment, is the reason for such surgery. Adjacent segment degeneration studied on 217 consecutive fusion patients in 2001 showed that after an average of only 5 years 10% of patients had developed transitional changes requiring re-operation (Ghiselli et al, NASS, Seattle, November 1, 2001).
In this classic example of example of the “transitional syndrome” it resulted from inappropriate surgery to start with. The patient, a 64 year old retired window was talked into a five level front and back fusion as primary treatment for her low back pain. Back pain relief lasted for only 9 months before more disabling pain occurred. Two years after surgery this patient had developed a prominent transitional syndrome above the fusion associated with a developing retrolisthesis. An aberrant pedicle screw also present.
Rigid multi-level instrumented spine stabilization is inherently a non-physiological procedure. It is now clear from American Medical Association terminology that the term “fusion” is now obsolete having been replaced by the term “Arthrodesis.” In 1987 and in 1990 the Editor first introduced the concept of “flexible stabilization” and “non-metallic flexible stabilization systems” in spinal devices as means of extending the vistas of the spine surgeon (Burton CV: The Liabilities of Fusion. In Cauthen JC (editor) Lumbar Spine Surgery. Baltimore:Williams and Wilkins, 1987; Burton CV: Fusion: Where It’s Been and Where It’s Going. In Weinstein JN, Weisel SW (editors) The Lumbar Spine. Vol. 2. Philadelphia: W.B. Saunders Company, 1990).
In 1994 Henri Graff , of Lyon, France, pointed out that: “a fused” spine is not a normal state and introduced a spine stabilization system designed to provide better load-bearing. The Editor’s studies on flexible stabilization systems continue to show that the human body is a basically hostile environment for even biocompatible materials.
Scientific studies continue to support the observation that flexible implants significantly reduce motion at adjacent segments. With the establishment of the paradigm of the importance of flexible stabilization attention has also turned toward the better use of the patient’s own “biomaterials” for which the results are more rewarding and the price “is right.”