Multilevel Spinal Fusion for Low Back Pain

A multilevel spinal fusion surgery involves fusing 2 or more motion segments of the spine to become one single unit. This surgery is designed to improve spinal stability and reduce pain in conditions that cause spinal malalignment or spinal degeneration. 

 Typically, spine surgeons recommend multilevel spinal fusion when¹Smorgick Y, Park DK, Baker KC, et al. Single- versus multilevel fusion for single-level degenerative spondylolisthesis and multilevel lumbar stenosis: four-year results of the spine patient outcomes research trial. Spine (Phila Pa 1976). 2013;38(10):797-805. doi:10.1097/BRS.0b013e31827db30f:

• The patient’s quality of life is significantly affected due to lower back pain and functional limitations
• Nonsurgical pain management, such as medication, physical therapy, and injection treatments, have been tried for several months or longer without satisfactory improvement
• A spinal x-ray or magnetic resonance imaging (MRI) scan confirms degenerative changes or malalignment at more than one level

In the lower back, a multilevel spinal fusion surgery involves the fusion of two or more motion segments between the first lumbar vertebra, L1, and the first sacral vertebra, S1.

Overview of Spinal Fusion Surgery

The lumbar spine (low back) has 5 mobile spinal levels from L1 to S1, also known as motion segments. At each spinal level, motion is controlled by a disc and a pair of facet joints. The disc and motion segment are named by the vertebral body above and below; for example, the disc and motion segment between the L4 and L5 vertebrae are called the L4-L5 disc and the L4-L5 motion segment.

Fusion of a motion segment typically involves creating a living bone bridge between the two surrounding vertebrae, either behind the disc between the posterior bony elements, through the disc space, or both. This bridge stiffens the spine and stops any motion at the fused motion segment. A bone graft is commonly used to bridge the vertebral bones, which is then replaced by the patient with new native bone. Bone graft materials can be the patient’s own bone (autograft), donor bone from a bone bank (allograft), or synthetic materials commonly populated with a patient’s bone marrow. The bone graft facilitates bone growth through and around the disc, fusing the spinal bones (vertebrae) together, and immobilizing the motion segment. Surgery may also include fusing the spinal facet joints for added stability. Spinal instrumentation (typically screw and rod fixation) is commonly used to secure the fused segments.

Multilevel Spinal Fusion

Multilevel spinal fusion is almost always performed on contiguous spinal levels. The commonly fused spinal levels in the lower back typically include the motion segments in the lower half of the lumbar spine. These lowermost motion segments bear higher stresses than other parts of the spine, making them more prone to degenerative conditions.

• Two-level fusion is typically performed at¹Smorgick Y, Park DK, Baker KC, et al. Single- versus multilevel fusion for single-level degenerative spondylolisthesis and multilevel lumbar stenosis: four-year results of the spine patient outcomes research trial. Spine (Phila Pa 1976). 2013;38(10):797-805. doi:10.1097/BRS.0b013e31827db30f: 
  • L3-L5—which includes fusing L3-L4 and L4-L5
  • L4-S1—which includes fusing L4-L5 and L5-S1
• Three-level fusion is typically performed at L3-S1—which includes fusing L3-L4, L4-L5, and L5-S1¹Smorgick Y, Park DK, Baker KC, et al. Single- versus multilevel fusion for single-level degenerative spondylolisthesis and multilevel lumbar stenosis: four-year results of the spine patient outcomes research trial. Spine (Phila Pa 1976). 2013;38(10):797-805. doi:10.1097/BRS.0b013e31827db30f^,2Inage K, Ohtori S, Koshi T, et al. One, two-, and three-level instrumented posterolateral fusion of the lumbar spine with a local bone graft: a prospective study with a 2-year follow-up. Spine. 2011;36(17):1392-1396. doi:10.1097/BRS.0b013e3181f40e69 

Degenerative changes typically occur at L4-L5, making this the most common spinal motion segment recommended for fusion surgery.¹Smorgick Y, Park DK, Baker KC, et al. Single- versus multilevel fusion for single-level degenerative spondylolisthesis and multilevel lumbar stenosis: four-year results of the spine patient outcomes research trial. Spine (Phila Pa 1976). 2013;38(10):797-805. doi:10.1097/BRS.0b013e31827db30f 

Fusing two or three levels of the spine is typically preferred over fusing more than 3 levels. Fusion of more than three levels may compromise the stability of the spine, increasing the risk of post-surgical complications.³Li T, Shi L, Luo Y, Chen D, Chen Y. One-level or multilevel interbody fusion for multilevel lumbar degenerative diseases: a prospective randomized control study with a 4-year follow-up. World Neurosurgery. 2018;110:e815-e822. doi:10.1016/j.wneu.2017.11.109 Four-level fusion (L2-S1) and full lumbar fusion (typically T10-S1) are uncommon but may be performed in the treatment of advanced degeneration with multilevel instability and spinal deformity. 

Common Indications for Multilevel Spinal Fusion

The 4 main indications for multilevel spinal surgeries are³Li T, Shi L, Luo Y, Chen D, Chen Y. One-level or multilevel interbody fusion for multilevel lumbar degenerative diseases: a prospective randomized control study with a 4-year follow-up. World Neurosurgery. 2018;110:e815-e822. doi:10.1016/j.wneu.2017.11.109:

1. Degenerative changes in the spine: changes resulting from aging and wear and tears of the spine, such as degenerative spondylolisthesis and degenerative disc disease . These degenerative changes are often accompanied by spinal stenosis with neurologic compression, and the fusion is done along with decompression surgery (such as laminectomy).
2. Spinal deformity or malalignment: a deviation in the normal spinal alignment, such as scoliosis or kyphosis.
3. Spinal defects: conditions such as spondylolysis, where a defect in the pars interarticularis (a small segment of bone joining the facet joints in the back of the spine) causes the vertebral bone to slip forward and alter the normal alignment of the spine. This type of forward slippage of the vertebra is called isthmic spondylolisthesis. 
4. Revision lumbar surgery: patients with prior lumbar decompression and/or fusion surgery with either failure of fusion healing and/or development of degeneration or instability in the adjacent motion segment.

Multilevel spinal fusions may also be a part of the treatment of less common conditions that can affect more than one level of the spine, such as spinal fractures, tumors, and infections.

Potential Benefits of Multilevel Spinal Fusion

The primary goals of fusing more than one level of the spine are to improve stability and reduce pain. This surgery is intended to control the further progression of spinal degeneration or malalignment. Surgeons fuse more than one spinal level only if the benefit of fusing the segments outweighs the potential risks associated with this extensive procedure.

Long-Term Outcomes of Spinal Fusion Surgeries

Most patients who undergo lumbar multilevel spinal fusion experience some degree of improvement in their back pain. Factors that influence the outcome typically depend on the presence of underlying conditions, the health of the other segments of the spine that are not being fused, the number of levels being fused, and the age of the patient.  

A study evaluating long-term outcomes in 101 patients with multilevel spinal fusion found⁴Ibrahim JM, Singh P, Beckerman D, et al. Outcomes and Quality of Life Improvement After Multilevel Spinal Fusion in Elderly Patients. Global Spine J. 2020;10(2):153-159. doi:10.1177/2192568219849393:

• 77% of the patients had reported some improvement in back pain 
• 51% of patients were satisfied with their surgical outcome
• 24% of the patients needed revision surgery within 2 to 5 years due to a complication
• 19% of the patients had a major neurological complication
• 48% of patients were admitted to the intensive care unit due to an adverse event

Multilevel fusion surgeries are mostly elective (unless indicated due to a medical emergency), meaning it’s up to the patient to decide whether or not to have surgery. The most common indication for considering this surgery is unremitting and disabling lower back pain unresponsive to all attempts at non-surgical treatment including pain management. Leg pain, numbness, tingling, and weakness may also be part of the patient’s symptoms.

It is advisable for patients to discuss the potential surgical benefits, risks, surgical alternatives, and recovery with their surgeon prior to scheduling the procedure.