Procedures: Lumbar Spine Fusion

Keywords
Spine fusion
Back fusion
Spinal fusion

Definition
Fusion is the uniting of two or more motion segments (disc space and paired facet joint = a single motion segment) together by the placement of bone graft. Fusion is not the immediate result of placement of bone graft linking the two motion segments but occurs over time as the result of the body's healing process. Modern lumbar fusion surgery attempts to enhance the body's healing potential to promote the fusion process. This may be accomplished by the use of instrumentation (internal brace), biologic properties (stimulating the biochemistry of converting the raw materials of bone graft into a solid union of bone), and/or electrical stimulation of the bone graft to increase the tendency to form a solid uinon of bone. The ultimate goal of fusion is the elimination of motion between the motion segments and thus pain elimination or reduction from the sources of pain (anatomic sites) in the motion segment.

Indications
Lumbar spine fusion is commonly used to promote stability between unstable motion segements of the spine, correct deformity among the segments, and restore the architecture within a segment producing pain within the structure.

Classic Lumbar Fusion Indications:

Deformity	Spondylolisthesis	Schliosis	Kyphosis
Fracture	Destruction of bone with pressure produced on the neurological structures	Destruction of bone with disruption of the spine architecture leading to instability
Tumor	Destruction of bone with pressure produced on the neurological structures	Destruction of bone with disruption of the spine architecture leading to instability	Removal of tumor (benign to cure) or selected malignant tumors
Infection	Destruction of bone with pressure produced on the neurological structures	Destruction of bone with disruption of the spine architecture leading to instability	Establishing the infection when non-invasive diagnosis has not worked and/or removal of infected material to eliminate infection
Instability	angulation	Translation	rotational
Degenerative Disc Disease	Painful anatomic sites within the motion segment

Technical Considerations
There are only so many anatomic sites on the vertebra to link one vertebra to another thus uniting the motion segments. The technical aspect of fusion is the use of bone graft to link the specific geography of one vertebra to another with the final result of eliminating motion between the vertebra (motion segment) once fusion is achieved. In addition, to linkage sites for bone graft, the vertebra serves as a place to anchor instrumentation serving as a scaffold to permit fusion and aid in the elimination of motion between segments.

The table below lists different techniques that are utlized in lumbar spine fusion.

Posterolateral Fusion	Posterior Lumbar Interbody Fusion PLIF	Transforaminial Poster Lateral Interbody Fusion TLIF
Posterior Lumbar Instrumentation and Fusion	Anterior Lumbar Fusion	Anterior Interbody Cages
Anterior-Posterior Fusion	Electrical Stimulation of bone grafts	Types of bone grafts

Literature Review
Historical Perspective:
In 1911, two surgeons reported performing a lumbar spine fusion for infection (tuberculosis). (ref # 12) Since then the reasons for lumbar fusion have expanded to include those listed above: tumor, fractures, instability, deformity and degenerative disc disease.

Current Concept:
Although there are many reasons for lumbar spine fusions as listed above, the most common reason is related to degenerative disc disease. A recent study on spine fusion and degenerative disc disease has brought the issue of fusion and degenerative disc disease into a new focus. (ref #1) For the first time, a scientifically valid study has supported the use of fusion in the treatment of back pain and leg pain due to degenerative disc disease. (ref #1) All of the patients in this study had back pain for at least 2 years, degenerative disc changes on xray, and pain 7/10. (ref #1) 98% of the patients were examined at 2 years from surgery and compared to the patients who did not have surgery. (ref #1) 3 different types of fusion were used: posterolateral fusion alone, posterolateral fusion with supplemental posterior instrumentation and interbody fusion (anterior or posterior interbody fusion). (ref #1) The results of the study are listed in the table below.

Comparison Categories	Fusion Group	No Fusion Group: Conservative Care
Back pain reduction	33%	7%
Disability	25%	6%
Patient perception of overall improvement	63%	29%
Back to work after treatment	36%	13%
Undergo the same treatment again	75%	53%

Complications
The complications of lumbar fusion depend on the technique used and the anatomic approach to the vertebra. (ref #4) In general, failure to improve with surgery, problems at motion segments above a fusion, complications of approach to the spine (anterior or posterior surgery), failure to obtain a successful fusion and instrumentation problems are the general complications of lumbar fusion surgery. (ref #4)

Author’s Comment
Lumbar spine fusion has a role in the treatment of lumbar spine disease. The most clear cut reasons for lumbar fusion involve the traditional ones: deformity, fracture, tumor, instability and infection. Each of these categories will have specific subgroups with percentage of benefit from surgery. In the case of degenerative disc disease, the role of fusion is evolving. The natural history of back pain and degenerative disc disease is often a smoldering pattern of symtpoms with periods of no pain. There are patients with enough disability, and persistence of pain to be considered for lumbar spine fusion. However in the study noted above, 37% were not improved with lumbar spine fusion and even in those with "successful" results from surgery, there still was an element of low back pain. "Better but not perfect" were the results of this group with chronic disabling back pain for at lease 2 years prior to lumbar fusion. (ref #1) (ref #2) (ref #3) (ref #4) (ref #5) (ref #6) (ref #7) (ref #8) (ref #9) (ref #10) (ref #11) (ref #12)

References
1. Fritzell, P. e. a. (2001). "2001 Volvo Award Winner in Clinical Studies: Lumbar Fusion Versus Nonsurgical Treatment for Chronic Low Back Pain."
Spine 26(23): 2521-2532.
2. Hanley, E. N. e. a. (1999). "Lumbar Arthrodesis for the Treatment of Back Pain." J.B.J.S. 81-A(5): 716-730.
3. Gibson, J. N., et al. (1999). "The Cochrane review of surgery for lumbar disc prolapse and degenerative lumbar spondylosis." Spine 24: 1820-32.
4. Brown, C. A., et. al., (1998). "Complications in Spinal Fusion." Orthop Clin North Am 29(4): 679-699.
5. Boden, S. D. (1998). "The Biology of Posterolateral Lumbar Spinal Fusion." Orthop Clin North Am 29(4): 603-619.
6. Sandhu, H. S., et. al. (1998). "Biologic Enhancement of Spinal Fusion." Orthop Clin North Am 29(4): 621-631.
7. Gelalis, I. D., et al. (1998). "Thoracic and Lumbar Fusions for Degenerative Disorders." Orthop Clin North Am 29(4): 829-842.
8. Abraham, D. J., et al. (1998). "Indications for Thoracic and Lumbar Spine Fusion and Trends in Use." 1998 29(4): 803-811.
9. Hellman, E. W., et al. (1998). "Clinical Outcome After Fusion of the Thoracic or Lumbar Spine in the Adult Patient." Orthop Clin North Am 29(4): 859-869.
10. Deyo, R. A., et al. (1993). "Lumbar spinal fusion: a cohort study of complications, reoperations, and resource use in the Medicare population." Spine 18: 1463-70.
11. Turner, J. A., et al. (1992). "Patient outcomes after lumbar spinal fusions." JAMA 268: 907-911.
12. Esses, S. I., et al. (1991). "Indications for Lumbar Spine Fusion in the Adult." C.O.R.R. 279(June 1982): 87-100.

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