Failed Spinal Fusion Surgery

A spinal fusion surgery is considered unsuccessful when it fails to improve spinal stability and/or reduce pain either immediately after surgery or over time.

Several factors contribute to a failed spinal fusion surgery; the most important factors include the patient’s age and general health, type of surgery, number of fused levels, and use of spinal instrumentation.

Pseudoarthrosis: Failure to Achieve Solid Bony Fusion

If the surgery fails to achieve proper bony fusion between the fused segments, some patients may begin experiencing symptoms, which primarily include back pain. The pain is usually limited to the lower back and may also radiate to the leg and foot. This condition is called pseudoarthrosis.

Failed fusions may result in loss of function and increased usage of pain medication.¹Patel VV, Billys J, Okonkwo DO, He DY, Ryaby JT, Radcliff K. Three- and 4-level lumbar arthrodesis using adjunctive pulsed electromagnetic field stimulation: a multicenter retrospective evaluation of fusion rates and a review of the literature. Int J Spine Surg. 2021;15(2):228-233. doi:10.14444/8031 Fusion failure is typically more common in the L5-S1 spinal segment.²Tannoury C, Bhale R, Vora M, Saade A, Kortbawi R, Orlando G, Das A, Tannoury T. Pseudarthrosis Following Lumbar and Lumbosacral Fusion Using the Antepsoas Technique. Spine (Phila Pa 1976). 2021 Dec 15;46(24):1690-1695. doi: 10.1097/BRS.0000000000004115. PMID: 34474451.

Common causes for failed fusion are listed below.

Smoking

Smoking releases nicotine into the body, which causes imbalances in the body’s metabolic functions, decreases bone mineral density, reduces bone formation, and ultimately delays bone healing, which may result in failed fusion.³Cruz A, Ropper AE, Xu DS, et al. Failure in Lumbar Spinal Fusion and Current Management Modalities. Semin Plast Surg. 2021;35(1):54-62. doi:10.1055/s-0041-1726102

Certain nonsteroidal anti-inflammatory drugs (NSAIDs)

Some NSAIDs have been linked to pseudoarthrosis after spinal surgery. A common example is Ketorolac, a prescription medication that may effectively manage post-surgical pain, but delay bone healing when used in certain doses.³Cruz A, Ropper AE, Xu DS, et al. Failure in Lumbar Spinal Fusion and Current Management Modalities. Semin Plast Surg. 2021;35(1):54-62. doi:10.1055/s-0041-1726102

Choice of bone graft

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. In general, autografts from the iliac crest bone are considered the gold standard for spinal fusion surgeries,⁴Cohen JD, Kanim LE, Tronits AJ, Bae HW. Allografts and Spinal Fusion. Int J Spine Surg. 2021;15(s1):68-93. doi:10.14444/8056 but these grafts may not always be possible to harvest due to the risk of pain, infection, nerve injury, extended surgical time, and increased blood loss in some patients.¹Patel VV, Billys J, Okonkwo DO, He DY, Ryaby JT, Radcliff K. Three- and 4-level lumbar arthrodesis using adjunctive pulsed electromagnetic field stimulation: a multicenter retrospective evaluation of fusion rates and a review of the literature. Int J Spine Surg. 2021;15(2):228-233. doi:10.14444/8031

See Bone Graft for Spine Fusion

Allografts, such as cellular allografts and bone morphogenic protein, are effective alternatives to autografts because they are easy to get, can be easily used, and help with bone growth.⁴Cohen JD, Kanim LE, Tronits AJ, Bae HW. Allografts and Spinal Fusion. Int J Spine Surg. 2021;15(s1):68-93. doi:10.14444/8056

Choice of surgical approach

Research indicates that when the graft is placed under compression (such as in an interbody fusion), there’s a higher possibility of better fusion than when it’s placed under tension (such as in a posterolateral fusion). An interbody fusion provides increased surface area for bone contact and the ability of the graft to share the load on the front part of the spine. These factors usually translate to a more favorable fusion rate.¹Patel VV, Billys J, Okonkwo DO, He DY, Ryaby JT, Radcliff K. Three- and 4-level lumbar arthrodesis using adjunctive pulsed electromagnetic field stimulation: a multicenter retrospective evaluation of fusion rates and a review of the literature. Int J Spine Surg. 2021;15(2):228-233. doi:10.14444/8031

Inadequate preparation of the surgical site

A successful fusion depends on adequate preparation of the surgical site, which includes removal of all soft tissue, proper placement of the bone graft, and preparation of the bony surfaces of the vertebrae to receive the bone graft. In general, a larger contact area between the vertebral bone and the graft provides a better possibility for a solid fusion.⁵Cheng L, Nie L, Zhang L. Posterior lumbar interbody fusion versus posterolateral fusion in spondylolisthesis: a prospective controlled study in the Han nationality. Int Orthop. 2009;33(4):1043-1047. doi:10.1007/s00264-008-0588-x

Number of fused levels

Multilevel fusions containing 3 or more levels have a significantly higher risk of developing pseudoarthrosis compared to fusing 1-2 levels.¹Patel VV, Billys J, Okonkwo DO, He DY, Ryaby JT, Radcliff K. Three- and 4-level lumbar arthrodesis using adjunctive pulsed electromagnetic field stimulation: a multicenter retrospective evaluation of fusion rates and a review of the literature. Int J Spine Surg. 2021;15(2):228-233. doi:10.14444/8031

Implant Failure

Spinal fusion can fail if there is not enough support to hold the spine while it is fusing. Therefore, spinal implants, such as pedicle screws and rods, may be used as an internal splint to hold the spine while it fuses after spine surgery. However, like any other metal, spinal instrumentation can fatigue and break.

Implant failure (loosening or breakage of the screw or rod) may be associated with fusion failure and a poor clinical outcome. In the lower back, common implant-related problems include pedicle screw loosening, especially of the screws at S1, and infection. Some patients with pedicle screw loosening may develop back pain and need revision surgery to fix/remove the hardware.⁶Röllinghoff M, Schlüter-Brust K, Groos D, et al. Mid-range outcomes in 64 consecutive cases of multilevel fusion for degenerative diseases of the lumbar spine. Orthop Rev (Pavia). 2010;2(1):e3. doi:10.4081/or.2010.e3

Adjacent Segment Disease

Mobile spinal levels surrounding the fused segments bear additional stresses as motion is restricted across the fusion. This additional stress is felt to contribute to a higher incidence of degeneration of adjacent segments, which could result in pain and the need for additional surgery in the future. This condition is known as adjacent segment disease. The stress seen by an adjacent level and the risk of adjacent segment disease is felt to be progressively higher with more levels stiffened by fusion. For this reason, multilevel spinal fusions may have a higher risk of adjacent segment disease than single-level fusions.⁶Röllinghoff M, Schlüter-Brust K, Groos D, et al. Mid-range outcomes in 64 consecutive cases of multilevel fusion for degenerative diseases of the lumbar spine. Orthop Rev (Pavia). 2010;2(1):e3. doi:10.4081/or.2010.e3

Research indicates that at least 30% of patients with lumbar spinal fusion may develop adjacent segment disease over time.⁶Röllinghoff M, Schlüter-Brust K, Groos D, et al. Mid-range outcomes in 64 consecutive cases of multilevel fusion for degenerative diseases of the lumbar spine. Orthop Rev (Pavia). 2010;2(1):e3. doi:10.4081/or.2010.e3 In the lower back, the fusion of the L4-L5 spinal segment is associated with a higher risk of adjacent segment disease.⁷Lee JC, Choi SW. Adjacent Segment Pathology after Lumbar Spinal Fusion. Asian Spine J. 2015;9(5):807-817. doi:10.4184/asj.2015.9.5.807

Loss of Stability in the Adjacent Segment

It is common for surgeons to decompress a spinal level above or below a fused segment.⁸Smorgick 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 Decompression is a surgical procedure that is performed to alleviate sciatica symptoms caused by pinched spinal nerves. During a lumbar decompression back surgery, a small portion of the bone over the nerve root and/or disc material from under the nerve root is removed to give the nerve root more space and provide a better healing environment.

When decompression is performed above a fused segment, the integrity of the strong spinal ligaments, which act as tough bands to support and stabilize the spine (especially while bending forward), can be compromised due to excision, eventually leading to segmental instability in the region.⁸Smorgick 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