Pain after spinal fusion may be from post-surgical muscle damage

Many people have successful spinal surgery. Some do not. There are many reasons why someone will have a failed spinal surgery. One reason among the many causes can be the muscle damage caused by the fusion surgery itself.

Back muscle degeneration in lumbar fusion patients

A team of surgeons published a paper (1) examining the post-surgical phenomena of back muscle degeneration in lumbar fusion patients. The goal was to find answers for failed back surgery syndrome. What the surgeons found was Up to 25% of patients report unimproved or worse pain and up to 40% are not happy with the outcome of lumbar fusion. 

  • up to 25% of patients report unimproved or worse pain and up to 40% are not happy with the outcome of lumbar fusion.
  • While the researchers acknowledged that there are many possible reasons for poor results, including instrumentation failure, inadequate surgical technique, and poor patient selection, they were looking for the relationship between back muscle injury after surgery and the patient’s chronic back pain.

The relationship was found. In patients who had continued pain after back surgery, muscle biposies revealed:

Atrophy of paraspinal muscles,

Loss of muscular support leading to disability and increased biomechanical strain,

and possibly failed back syndrome.

“It is well established that posterior spinal surgery results in damage to the paraspinal musculature.”

A team of German and Canadian researchers (2) sought to understand the problem of failed fusion as a result of muscle damage, saying: “It is well established that posterior spinal surgery results in damage to the paraspinal musculature.” The researchers found that axial (mechanical) compressive forces at the adjacent (fusion) levels increased after surgical muscle damage. The results suggest that the paraspinal muscles of the lumbar spine play an important role in adjacent segment loading of a spinal fusion. If the muscles are damaged, adjacent segment disease or failed fusion is more likely.

Patients who had pain 7 – 11 years after spinal fusion had a “27% reduction in muscle density”

Doctors at Oslo University Hospital examined patients who had continued pain 7 to 11 years after spinal fusion.(3) The purpose was to test their observations that reduced muscle strength and density observed at one year after lumbar fusion may deteriorate more in the long term. The results: 27% reduction in muscle density.

In earlier research from Norwegian researchers,(4) patients with chronic low back pain who followed cognitive intervention and exercise programs improved significantly in muscle strength compared with patients who underwent lumbar fusion. In the lumbar fusion group, muscle density decreased significantly at L3–L4 compared with the exercise group.

After failed back surgery muscle and fascia are unexplored pain-generating tissue

A study from April 2020 (5) went to find the answer of pain after failed back surgery in the soft tissue and muscles of the spine. Lead by the Weill Cornell Center for Comprehensive Spine Care, the study authors “reviewed the pathophysiology and functional aspects of muscle-related back pain. (Through) case presentations (they) demonstrated the utility of evaluation and treatment of sensitized muscles to eliminate pain in failed back surgery patients post-minimally invasive spinal surgery.”

Here is more of what the authors wrote: “In our quest to improve outcomes for minimally invasive spinal surgery, muscle and fascia are unexplored pain-generating tissue. The role of muscle in possibly causing postoperative pain is not simply the effect of sparing of soft tissue. It requires recognizing the possibility that muscle generated pain was a contributing factor presurgically as well as postsurgically and also has effects on muscle function.

The absence of the study of the pathophysiology of muscle pain in medical education impairs the appreciation of the presence of muscle generated pain as an important etiology in assessing surgical candidates.”

Paraspinal muscle changes (atrophy) after single-level posterior lumbar fusion

A February 2020 paper (6) examined the “widely accepted surgical technique,” posterior lumbar fusion that had been related to the possibility of paraspinal muscle atrophy after surgery. In this study the research surgeons  investigated one-year postoperative changes in the paraspinal muscle to assess atrophy. These patients underwent a single level fusion at L4-L5.


Highlighted below is the multifidus muscle

In this study, atrophy of the multifidus muscle was prominent; this, the researchers noted was consistent with the findings of previous studies. Because the multifidus muscle is an important stabilizer of the lumbar spine, multifidus muscle atrophy is considered to be related to low back pain.

Interestingly the researchers also noted: “In our study, the association between low back pain and severe multifidus muscle atrophy during the one-year follow-up was unclear. Considering the stabilizing effect of the PLIF surgery, it is difficult to observe the correlation between muscle atrophy and low back pain in the short term follow-up. However, given that previous studies have stated that the reduction of paraspinal muscle volume is associated with pain, the apparent post-operative multifidus muscle atrophy observed in our study may have a negative impact on the long-term clinical results.”

Minimally invasive surgery or open surgery. Which causes more muscle damage?

One of the perceived benefits of minimally invasive spinal surgery is that the minimally invasive surgery will cause less muscle damage. A 2020 paper offered a comparison. (7)

“Laminotomy and transforaminal lumbar interbody fusion (TLIF) is usually used to treat unstable spinal stenosis. Minimally invasive surgery can cause less muscle injury than conventional open surgery. The purpose of this study was to compare the degree of postoperative fatty degeneration in the paraspinal muscles and the spinal decompression between conventional open surgery and Minimally invasive surgery based on MRI.

Forty-six patients received laminotomy and TLIF (21 conventional open surgery, 25 Minimally invasive surgery). . . Lumbar MRI was performed within 3 months before surgery and 1 year after surgery to compare muscle-fat-index (MFI) change of the paraspinal muscles and the dural sac cross-sectional area (the dural surrounding the spinal cord to assess stenosis compression) change.

The average muscle-fat-index (more fat meaning less muscle meaning more degeneration) change at L2-S1 erector spinae muscle was significantly greater in the conventional open surgery group. A significant muscle-fat-index change difference between the conventional open surgery and minimally invasive spinal surgery group was also found in the erector spinae muscle at the caudal (lower spine) adjacent level.”

Here are the trade-offs

  • Dural sac cross-sectional area improvement (meaning less stenosis) was significantly greater in the conventional open surgery group
  • However, conventional open surgery is associated with more prominent fatty degeneration of the paraspinal muscles.
  • Statically significant post-operative muscle-fat-index change was only noted in erector spinae muscle at caudal adjacent level and L2-S1 mean global level.
  • Conventional open surgery produces a greater area of decompression (better surgical result) on follow up MRI than minimally invasive surgery with no statistical significance.

The open surgery in this study was considered better than the minimally invasive surgery for stenosis decompression and the muscle damage was limited to the lower spine at L2-S1.

Post-fusion treatment options

At our practice we utilize Platelet-Rich Plasma as one of our injection treatments for the patient with chronic low back pain. We may also utilize bone marrow derived stem cell therapy. The decision as to which one of these care options to use is based on an examination in the office and an assessment of the person’s pain and functional difficulties along with the patient’s goal of treatment. Someone who needs to return to work as a landscaper will have a different treatment priority than a retired individual with lesser physical demands on his/her back.

PRP treatments involve collecting a small amount of your blood and spinning it in a centrifuge to separate the platelets from the red cells. The collected platelets are then injected back into the injured or post-surgical areas of the spine to stimulate healing and regeneration. PRP utilizes specific components or your blood, specifically platelets, which act as wound and injury healers.

Bone marrow derived stem cell therapy maybe used to treat problems of back pain and muscle problems stemming from degenerative disc disease of the spine, and tendon and ligament injury. For the patient suffering from back pain after spinal fusion, nothing about their life is typical except in the common question they ask, “Can your treatments really help me?” There has to be a realistic expectation of what our treatment can do and what they can’t do. If there are issues of continued pain following a fusion surgery, stem cells and PRP treatments may be effective in helping pain if there are issues with ligament and tendon instability causing segment disease above and below the fusion.

To make the spinal muscles strong, and build your “core,” you would need resistance training. A problem following fusion surgery is that not only are the muscles damaged, but the muscle tendons are damaged as well. Resistance training or post-surgical rehabilitation cannot be successful if the tendons and muscles are not strong enough to flex and contract enough to build new muscle. Further, the muscle will shrink and atrophy making the spine that much more painful.

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1 Ohtori S, Orita S, Yamauchi K, et al. Classification of Chronic Back Muscle Degeneration after Spinal Surgery and Its Relationship with Low Back Pain. Asian Spine Journal. 2016;10(3):516-521.
2 Malakoutian M, Street J, Wilke HJ, Stavness I, Dvorak M, Fels S, Oxland T. Role of muscle damage on loading at the level adjacent to a lumbar spine fusion: a biomechanical analysis. Eur Spine J. 2016 Sep;25(9):2929-37. doi: 10.1007/s00586-016-4686-y. Epub 2016 Jul 27.
3 Froholdt A, Holm I, Keller A, Gunderson RB, Reikeraas O, Brox JI. No difference in long-term trunk muscle strength, cross-sectional area, and density in patients with chronic low back pain 7 to 11 years after lumbar fusion versus cognitive intervention and exercises. Spine J. 2011 Aug;11(8):718-25. doi: 10.1016/j.spinee.2011.06.004. Epub 2011 Aug 3.
4. Keller A, Brox JI, Gunderson R, Holm I, Friis A, Reikerås O. Trunk muscle strength, cross-sectional area, and density in patients with chronic low back pain randomized to lumbar fusion or cognitive intervention and exercises. Spine (Phila Pa 1976). 2004 Jan 1;29(1):3-8.
5. Marcus NJ, Schmidt FA. Soft Tissue: A Possible Source of Pain Pre and Post Minimally Invasive Spine Surgery. Global Spine Journal. 2020 Apr;10(2_suppl):137S-42S.
6 Cho SM, Kim SH, Ha SK, Kim SD, Lim DJ, Cha J, Kim BJ. Paraspinal muscle changes after single-level posterior lumbar fusion: volumetric analyses and literature review. BMC musculoskeletal disorders. 2020 Dec;21(1):1-7.
7 Fu CJ, Chen WC, Lu ML, Cheng CH, Niu CC. Comparison of paraspinal muscle degeneration and decompression effect between conventional open and minimal invasive approaches for posterior lumbar spine surgery. Scientific reports. 2020 Sep 3;10(1):1-8.

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