SpineUniverse Case Study Library

Recurrent Spondylolisthesis with Significant Risk of Pseudarthrosis

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A 62-year-old flight attendant presents with a seven-month history of progressive low back pain that radiates into and throughout her right buttock and leg. She describes her pain as cramping, aching and is often accompanied by numbness.

Standing exacerbates her symptoms; within 40 minutes, pain is intolerable. Sitting or leaning forward temporarily relieves pain. She experiences pain most of the day, and it disrupts her sleep at night.

A complete workup was performed, including lumbar x-rays and MRIs.


Physical examination demonstrated a positive straight-leg raise on the right at 40-degrees. The remainder of the examination was normal.

Pre-treatment Images
The lumbar MRI (Fig. 1) correlates with the patient’s back pain and neurogenic claudication, and is notable for a grade one spondylolisthesis at L4-L5, as well as severe right-sided stenosis due to a synovial cyst (red asterisk). Weight-bearing accentuates the slip.  She had degenerative changes at L3-L4 and L5-S1 but without any associated instability or stenosis.

sagittal mri, red asterisk denotes a synovial cyst
Figure 1. Sagittal MRI; red asterisk denotes a synovial cyst.

lateral weight-bearing x-ray
Figure 2. Lateral weight-bearing x-ray

Prior Treatment

Nonsurgical treatments did not provide adequate pain or symptom relief.

  • Physical therapy
  • Chiropractic
  • Three epidural steroid injections


  • Grade I spondylolisthesis at L4-L5
  • Right-sided stenosis due to a synovial cyst

Suggest Treatment

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Selected Treatment

Minimally invasive surgery included resection of the synovial cyst via laminectomy, and TLIF to treat the instability associated with spondylolisthesis. The patient’s spondylolisthesis improved with intra-operative positioning, and was further reduced after insertion of an intervertebral PEEK spacer (Fig. 3). Bone quality was osteopenic.

intra-operative radiograph shows slip reduction
Figure 3. Intra-operative radiograph shows slip reduction.

Post-operative Course
The patient’s initial post-operative course was uncomplicated and leg pain was improved. She was discharged home the first post-operative day.

Post-operatively (in the weeks that followed the surgery), she had a fall; her subsequent x-ray demonstrated that her lumbar alignment had migrated back to its pre-operative position with PEEK spacer subsidence (Fig. 4).


postop radiograph, slip recurrence
Figure 4. Post-op radiograph; slip recurrence

Recurrence of spondylolisthesis presaged a significant risk of pseudarthrosis due to instrumentation failure. Based on her lack of back or leg pain, no surgical intervention was recommended. Rather, lumbar bracing with external bone stimulation was initiated.


Five months post-op
Five months after surgery, the patient remained symptom-free. She was compliant with treatment using the external bone stimulator daily and wearing the lumbar brace when out of bed. Lumbar CT scans demonstrated a lack of fusion, but the instrumentation was stable (Figs. 5, 6 and 7). In the absence of fusion, activity restrictions were further imposed and use of the external bone stimulator and lumbar brace continued.

5 months postop, sagittal CT, no fusion
Figure 5. Sagittal CT at 5 months post-op; no fusion

5 months postop, axial CT, L4 pedicle screws
Figure 6. Axial CT at 5 months post-op, L4 pedicle screws

Ten months post-op
The patient continued to do well. She continued to be compliant using the external bone stimulator and lumbar brace. CT scans at this time revealed fusion; an improvement from the previous imaging study (Figs. 7 and 8).

10 months postop, coronal view
Figure 7. Coronal view at 10 months post-op

10 months postop, sagittal view
Figure 8. Sagittal view at 10 months post-op

Fusion being confirmed, the external bone stimulator and lumbar brace were discontinued. The patient was allowed to gradually resume activities. She was released and planned to return to work as a flight attendant.

Surgeon’s Rationale: PEMF

Multiple factors can adversely influence bone healing and increase the risk of pseudarthrosis. These factors include smoking, osteoporosis, malnutrition, multilevel surgery, diabetes, rheumatoid arthritis, steroid use, NSAID use, spondylolisthesis, and history of radiation therapy.

This case presentation highlights a healthy, active woman who underwent uncomplicated surgery. Her risk factors of spondylolisthesis and osteopenia were compounded by a post-operative fall, which placed her at risk for pseudarthrosis. Despite loss of spondylolisthesis correction and significant risk of eventual pseudarthrosis, the patient’s fusion construct was salvaged by use of an external bone stimulator, and lumbar brace.

As demonstrated in the PEMF Stimulator Open Trial1,2 a pseudarthrosis can be managed without revision surgery by using external bone stimulation.

1 Simmons JW, Mooney V, Thacker I. Pseudarthrosis after Lumbar Spine Fusion: Non-operative Salvage with Pulsed Electromagnetic Fields. Am J Orthop. 2004. Jan;33(1):27-30.

2 Mooney V. A Randomized Double-blind Prospective Study of the Efficacy of Pulsed Electromagnetic Fields of Interbody Lumbar Fusions. Spine. 1990. 15(7):708-12.


The Spinal-Stim® is a noninvasive electromagnetic bone growth stimulator indicated as a spinal fusion adjunct to increase the probability of fusion success and as a nonoperative treatment of salvage of failed spinal fusion, where a minimum of nine months has elapsed since the last surgery.

Physician’s Disclosure
Jon Krumerman, MD received remuneration for his case presentation.


Case Discussion

This 62-year-old female had neurogenic claudication due to a facet cyst with a Grade I spondylolisthesis at L4-L5. She also has degenerative changes at L5-S1 with a retrolisthesis and collapse of the disc space. Nonoperative treatment consisted of physical therapy, chiropractic care and three epidural injections, which I completely agree with. Due to her failure to improve, surgery was indicated; I agree with the indication. She underwent a minimally invasive TLIF procedure with pedicle screws. It looks like a Capstone PEEK cage was inserted. While there is no mention of what was put into the cage, presumptively, I would think BMP, but this has not been mentioned.

On the patient's post-operative x-rays, everything looks to be in very good position, including the screws, reduction of the spondylolisthesis and placement of the cage at L4-L5. However, she suffered a fall and now has dislodgement of the cage into the neuroforamen and posteriorly into where the nerves are, and a loss of reduction. Furthermore, the L5-S1 space looks much more collapsed after her fall.

Treatment for this patient consisted of bracing and an external bone growth stimulator to treat the dislodgement of the cage and loss of reduction of her spondylolisthesis. CT scans at 10-months post-op show fusion mass, but still loss of sagittal balance. This furthers my review. I do agree with the index procedure; a decompression and fusion at L4-L5. Obviously, there are many ways of handling it, and a minimally invasive TLIF is an acceptable procedure.

From the post-operative x-rays, I think everything looks to be in very good position. However, I disagree with the post-operative management. The patient has a cage that is dislodged. The cage appears to be into the neuroforamen. I would like to see an axial view to determine if the cage is impinging upon the nerve. I feel that it is very aggressive to rely on a bone growth stimulator and a brace to treat this patient. I would have revised this procedure. I do advocate, and personally prescribe the stimulator that was used in this case. I think it is an excellent adjuvant to surgical intervention, both for cervical and lumbar fusions, especially in patients with comorbidities that increase the likelihood of pseudoarthrosis, as in this patient. However, I would not rely on a bone growth stimulator to treat a patient who has frank instability after a fall and hope that would alleviate her problem. I think that is asking a lot of any adjuvant to fusion.

Author's Response

This case was approached with pragmatism, not orthodoxy. Although this patient had migration of the PEEK spacer from its intra-operative position, she was not symptomatic for radiculopathy or exacerbated back pain. Based on her favorable clinical status, re-exploration was not advocated in favor of brace compliance and external bone stimulation. This approach spared her re-exploration surgery and possible extension of her fusion and instrumentation to adjacent levels.


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