When the word “chocolate” is spoken it is typically associated in most minds with “Hershey Bar” even though there are many other chocolate products. A similar situation exists in spine surgery when the word “fusion” is used. It is often simply assumed that this refers to rigid pedicle screw and rod fixation.
This common phenomenon is a narrow-minded exercise as many other alternatives exist for patient treatment. This failure to be informed of the other options is a leading cause of the “Failed Back Surgery Syndrome“. It is important for patients to understand that the word “fusion” has a narrow context and, as such, is therefore often misleading. Because the first fusions were performed only by orthopedic surgeons they thought of it in a manner similar to the setting of long bones where rigid healing (arthrosis) was good and non-rigid healing (pseudoarthosis) was bad. Simply put, the human spine is not a rigid long bone and a non-rigid stabilization, which is more physiologic, is often better therapy for the patient. Canadian Orthopedic Surgeon David Kuntz has expressed it more eloquently.
The intent of the classic bone “fusion” was to create a solid union between vertebral segments in order to correct segmental dysfunction or instability. Due to this unique mind-set the goal of “rigid fixation” has been the credo of most spine surgeons during the 20th century. It was only toward the end of that century that some first began to realize that multi-level rigid fixation (shown on the left) was not always optimal for everyone and that rigid fixation could carry with it a number of important liabilities for the patient. Because rigid fixation is inherently non- physiologic there are always associated stresses placed on adjacent segments.
We know that when individuals are born with congenital fusion of spinal segments this abnormality typically produces stress related degeneration on adjacent spinal segments. Physician created rigid fusions produce the same result. Instrumented rigid fusions consisting of pedicle screws and rods may be optimal for the purpose of stabilization in the treatment of spinal trauma where the risks are small and the benefits are high. What then are the risk factors for multi-level rigid pedicle screw and rod systems?
Fracture of pedicle causing nerve root irritation or injury requiring surgical revision. Screw malposition producing nerve irritation or injury requiring additional surgery. Post-healing need to remove painful instrumentation. Additional surgery or fusion because of stress-related transitional changes. Extensive devitalization of paraspinal tissues. Instrumentation producing artifact and not allowing meaningful follow-up MRI imaging.
These risks are not insignificant. How often is true informed consent provided to these patients? The stress factors produced by rigid instrumentation are so significant that iatrogenically produced fractures of the sacrum and pelvis are known to occur as well as “transitional degeneration.”As one medical student pointed out: some spine surgeons have created their own equivalent of a “full-employment” law where performing a rigid multi-level instrumented fusion almost guarantees a need for additional surgery in the future.
These issues become even more important when multi-level instrumented rigid procedures are employed in individuals with multi-level disc degeneration to start with. Many inappropriate multi-level instrumented arthrodeses are being recommended and performed in patients with genomic spine problems. It is only now that more than a handful of spine surgeons are finally looking at more physiologic answers to the correction of spinal dysfunction and instability. As we enter the 21st century the paradigm of “fusion” is finally giving way to the more appropriate concept of “stabilization.
There are few areas of medical care where William of Occam’s principle of “it is needless to do more when less will suffice” is more needed than in the field of spine care, particularly in spine surgery. Many times front and back surgeries are performed when a posterior approach alone would not only do the job but, also create a better result for the patient. The added risks of an unneeded anterior surgery are many. The anterior dissection often strips away important aortic arterial feeders to the vertebral column increasing the risk of infection and, in males, there is always the possibility of creating problems with erection and ejaculation.
Because medical devices are big business and because spinal fixation systems are very big business in today’s world M2H factors continue to play an important role in directing the type of spinal surgery being performed. Unnecessary instrumentation is costly from many viewpoints. It remains for the discerning consumer to sort through the hype in order to make reasonable and cost-effective decisions regarding their own health. Inherent in this is having a health care system which places the patient in the “driver’s seat” so that that it is the patient’s decision as to whether the treatment being recommended is reasonable and cost-effective and not having this decision be made by uninterested third party whose hidden agenda is financial self-interest.
Types Of Spine Stabilization:
Shown below is the 2004 Edition of the American Medical Association “Current Procedural Terminology” where the word “fusion” has now been relegated to the archaic, achieves and has been replaced by the correct term “arthrodesis” (Athro-joint, Desis-to bind). Arthrodesis refers to the entire spectrum of stabilization including flexible, as well as rigid procedures.
As a means of providing better orientation regarding the forms of spinal “arthrodesis” The various forms of it are outlined below: