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ALIF with Posterior Lateral Fusion: Aspen™ Spinous Process Fixation for Posterior Instrumentation

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History

This is a 32-year-old female who presents with a 13-year history of progressive low back pain. She denies any history of injury or activity resulting in low back pain.

Her pain is reported to range from 2/10 to 9/10. It is described as sharp and achy with associated lower extremity weakness and numbness. Other symptoms include:

  • Middle low back pain radiating into the pelvis
  • At times, when walking, she cannot tell if her legs are moving
  • Pain worsens with coughing/sneezing, lying down, bending, lifting, and twisting
  • Pain improves with changing positions

She reports walking and swimming 5 to 6 times a week.

Examination

The patient is 5'-7" tall and weighs 155 pounds. Her body mass index is 24.36. She appears healthy, alert, and in no acute distress.

Pain:

  • Low back aching, stabbing; up to 10/10
  • Buttock pain; up to 9/10
  • Hip pain; up to 9/10

Oswestry Disability Index: 40% (Moderate Disability)

Beck Depression Score: 20/21

Muscle Strength: full power in the lower extremities in all muscle groups

Gait: non-antalgic; tandem walking is normal

Flexion/Extension
Back flexion is 100-degrees, extension 30-degrees, and right and left lean 20-degrees.

Reflexes
Right patellar: 2/4
Left patellar: 2/4
Right Achilles: 1/4
Left Achilles: 2/4

Sensory
There is decreased sensation to light touch and pinprick in the right foot.

Prior Treatment

  • Chiropractic manipulation
  • Physical therapy
  • Pain medication (oxycodone)
  • Epidural steroid injections
  • Spine exercises
  • Heat/ultrasound
  • Massage
  • Traction

Pre-treatment Images

pre-treatment lumbar sagittal MRIFigure 1. Sagittal MRI

pre-treatment lumbar axial MRI, L5-S1 levelFigure 2. Axial MRI, L5-S1 level

Diagnosis

Lumbar radiculitis; severe degenerative disc disease at L5-S1; failing to respond to conservative measures

 

Suggest Treatment

Indicate how you would treat this patient by completing the following brief survey. Your response will be added to our survey results below.

Selected Treatment

  • Anterior lumbar interbody fusion (ALIF) L5-S1, with intervertebral PEEK interbody biomechanical device, anterior plating L5-S1, allograft, and one small bone morphogenetic protein (BMP) sponge (Infuse®, Medtronic, Inc., Memphis, TN).
  • Posterior lateral fusion L5-S1, with Aspen interspinous posterior instrumentation, allograft, and BMP (Aspen™ Spinous Process Fixation System, LANX®).

Surgeon's Treatment Rationale
When used in conjunction with an anterior lumbar plate and interbody spacer, the Aspen device provides equal fixation of the lumbar spine to an ALIF with plate and bilateral pedicle screws.

Karahalios DG, Kaibara T, Porter RW, et al.  Biomechanics of a lumbar interspinous anchor with anterior lumbar interbody fusion. J Neurosurg Spine. 2010 Apr;12(4):372-80.

Post-operative Images

Lateral (Fig. 3A) and posteroanterior (Fig 3B) post-operative fluoroscopic images.

post-operative lumbar lateral fluoroscopic imageFigure 3A

post-operative lumbar posteroanterior (PA) fluoroscopic imageFigure 3B

Outcome

2 weeks post-op
The patient is doing well and reports some post-operative soreness and tenderness. She reports her pain is 3/10 and comments, "the surgery helped".

She had been taking oxycodone for back and leg pain and hydrocodone for incisional pain. There are no complaints of leg pain or weakness. She had a normal physical and neurological examination; muscle strength in all areas is 5/5 with no atrophy, fasciculations or spasticity.

4 months post-op
The patient has no pain (0/10), weakness, numbness or bowel/bladder issues. She returned to work and continues a home exercise program. She reports her legs become "restless" if she stands or walking for a long period of time. She is not taking pain medications.

She had a normal physical and neurological examination; muscle strength in all areas is 5/5 with no atrophy, fasciculations or spasticity.

Excellent fusion across the interspace with no movement on flexion or extension (Figs 4A-D).

4 months post-op, lumbar lateral x-ray, excellent fusionFigure 4A

4 months post-op, lumbar x-ray, excellent fusionFigure 4B

4 months post-op, lumbar x-ray, excellent fusionFigure 4C

4 months post-op, lumbar x-ray, excellent fusionFigure 4D

Plan
Post-operative follow-up is planned for two-years from the date of surgery. Follow-up will include a lumbar CT scan.

Case Discussion

The indications for this patient to undergo fusion surgery are very acceptable: severe chronic back pain due to single-level degenerative disc degeneration and failure of non-surgical treatments. Further conservative care seems unlikely to provide any lasting benefit based on her history of multiple previous non-operative treatment modalities.

The general consensus on the indications for arthroplasty is that the segment to be treated should not have extensive degenerative changes such as facet arthropathy or complete disc space collapse. This patient does not appear (on axial MRI) to have any significant facet arthropathy, though there is near complete disc space collapse with extensive Modic degenerative changes. These findings, along with the published reports that fail to demonstrate any clear advantage over a single level fusion, make arthroplasty a less desirable choice.

The treatment that was performed for this patient can be regarded as very aggressive. There does not appear to be any pre-operative instability such as a grade I or higher spondylolisthesis, scoliosis, or significant congenital or iatrogenic bony defect. Therefore, the need for anterior plating and/or additional posterior fusion when threaded is very debatable and controversial. Allograft femoral rings or dowels as stand-alone fusion implants do have a high level of pseudoarthrosis, and the benefit of additional instrumentation has been proven. Results with threaded titanium cages without additional instrumentation are far better. We do not yet have sufficient evidence to warrant using PEEK intradiscal implants with bone morphogenetic protein. Thus, we don't really know the benefit or need of an anterior lumbosacral screw/plate fixation in this scenario. A stand-alone anterior lumbar interbody fusion (ALIF) is the most cost-effective treatment that yields very high results.

Though there may be a slight advantage in terms of rate of successful arthrodesis, the medical evidence does not show any clear additional clinical benefit for the combined circumferential procedure done in this young patient with single-level degenerative disc disease. In terms of cost of operating room time, added risk of infection with two operations, anesthesia time for the patient, implant and surgeons fees - the difference is very significant. It is highly likely that Medicare or private insurance coverage for these extra components to this patient's surgery will soon no longer be provided due to the lack of medical evidence of any benefit over a simpler one-stage procedure (done either anteriorly or posteriorly).

If the patient had a highly unstable traumatic diagnosis, or had spondylolisthesis, additional fixation or a combined anterior-posterior procedure rather a stand-alone interbody cage ALIF may be reasonable.

Author's Concluding Commentary

I appreciate Dr. Rodts discussion and agree that conservative care is unlikely to produce a long-lasting impact on the patient's pain. Therefore we both are in agreement that fusion is the appropriate surgical treatment. The next decision is the method of fusion. Anterior, posterior, minimally invasive, pre-sacral, facet screws, pedicle screws, posterior lateral, and interbody are the main options. Which method to employ continues to be a subject of controversy in the spine literature.

Although ALIF is widely applied in treatment of discogenic back pain, there is a faulty assumption among some surgeons that anterior lumbar interbody fusion with anterior plating is sufficient and that "most" patients do "well". The literature is replete with retrospective reviews of surgeons' self-reported outcomes. Neither of these class III studies, nor surgeons' self-reported statements in hallways or at meetings, serves as useful data on which one can counsel patients regarding expected outcomes. The best way to objectively evaluate clinical outcomes on ALIF patients is to look at multi-center randomized studies in which validated outcome surveys are administered by blinded objective non-surgical observers. Some of the cleanest data comes from control groups in artificial disc studies.1 Five-year follow-up results in the Charité trials submitted to the FDA reported the overall clinical success rate in the BAK (cage) group to be 51.2%. Admittedly these patients did not have anterior plating and underwent iliac crest autograft, but these factors were not the only reason for almost a 50% failure rate.

Supplementation with posterior instrumentation must therefore be considered with the goal of improved immediate mobilization of the motion segment. In a construct consisting of ALIF (without plate) and pedicle screws placed posteriorly, we observed reduced range of motion to 20% of intact. This appears to be the gold standard of immobilization. If an Aspen interspinous anchor (ISA) is used posteriorly, after an ALIF with a plate, mean range of motion is reduced to 13% of the intact specimen, 7% less than the gold standard.2 This may be partially explained by the fact that there is relatively more cortical bone in the spinous process, and the advantageous design of the Aspen, with an interspinous bumper, and teeth to grip the spinous process.

In this case example, the cause of the patient's pain is discogenic. Continued pain is presumably from micromotion at the involved segment. Maximal immobilization is therefore desirable, and the placement of an Aspen interspinous anchor achieves similar immobilization to pedicle screws while eliminating surgical time, radiation exposure, and surgical risk (nerve injury, bowel or vessel perforation with K-wires) with the placement of pedicle screws. The final proof in this patient is in the excellent surgical outcome, but larger prospective series are needed.

References

1. Guyer RD, McAfee PC, Banco RJ, et al. Prospective, randomized, multicenter Food and Drug Administration investigational device exemption study of lumbar total disc replacement with the CHARITÉ artificial disc versus lumbar fusion: Five-year follow-up. The Spine Journal. 9 (2009), pp 374-386.

2. Karahalios DG, Kaibara T, Porter RW, et al. Biomechanics of a lumbar interspinous anchor with anterior lumbar interbody fusion. J Neurosurg Spine. 2010 Apr;12(4):372-80.

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