Grade IV Ismthic Spondylolisthesis
The patient is a 32-year-old female who underwent in situ fusion (L4-S1) for grade II spondylolisthesis at age 16. She presents with increasing low back pain and bilateral L5 radiculopathy.
Her neurological examination revealed bilateral 4+/5 extensor hallicus longus. Otherwise, she is neurologically intact.
Figure 1A. Lateral x-ray, neutral, showing Grade IV spondylolisthesis
Figure 1B. Extension
Figure 1C. Flexion
Figure 1D. Lumbar AP x-ray
Figure 2A. AP x-ray, long cassette 36"
Figure 2B. Lateral x-ray, long cassette 36"
Figure 4A. Axial CT scan, L5
Figure 4B. Axial CT scan, L5-S1
Grade IV isthmic spondylolisthesis, L4-L5, L5-S1 pseudarthrosis.
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The patient underwent a laminectomy at L4-L5, L5-S1, L4-S1 pedicle screw placement, and L5-S1 TLIF with reduction of the spondylolisthesis.
At 1-year postop, there was complete resolution of symptoms and neurological deficit.
Figure 5A. Standing AP x-ray, 1-year postop
Figure 5B. Lateral x-ray, 1-year postop
Figure 6A. AP at 1-year postop, long cassette 36"
Figure 6B. Lateral at 1-year postop, long cassette 36"
Doctor Shaffrey obtained a nice reduction of this high grade spondylolisthesis. A deformity of this magnitude certainly warrants an interbody fusion. This construct demonstrates the impressive results that can be obtained from a posterior-only approach. Had this patient fused following her initial surgery, I suspect that a circumferential procedure would have been required.
This case represents two of the most debated concepts in deformity surgery: (1) The necessity to reduce spondylolisthesis and, (2) the need for iliac fixation. Certainly in a case such as this where there already is L5 nerve root compression, the risk of reduction causing further neuropraxic injury is great. Many surgeons would advocate EMG monitoring for reduction of high grades slips such as this. Reduction provides for indirect decompression of the L5 nerve root. The quality of the fusion construct is also optimized when the deformity is corrected. Reduction may also improve the patient's self-image and appearance. Even if a patient does fuse without reduction, the fusion mass can elongate and the slippage may progress. If it can be done safely, there is little reason not to reduce a spondylolisthesis of this nature. Certainly, a partial reduction is more favorable than none at all, especially in a mobile segment.
Where a pseudofusion has previously occurred, and when coronal deformity is likewise present, iliac fixation is justified. Biomechanical data supports the use of iliac fixation to back-up sacral screws and some studies have shown this pelvic fixation to be more important than anterior column support. Although tricortical fixation was obtained at S1 in this case, certainly the pelvic fixation provides additional stability with little added risk in experienced hands.
In complex revision cases such as this, aggressive reduction and supplemental fixation can help ensure a successful outcome with benefits far outweighing the risks.
I appreciate Dr. Highsmith's insightful comments.
Considering her history of prior nonunion, we considered a TLIF, or transpsoas instrumentation and fusion procedure, could have been considered at the L4-L5 level as well. I was considered about a loss of fixation, or additional L5 nerve root stretch, if a TLIF was performed. Fortunately, the surgical result has been satisfactory and solid arthrodesis appears to have been achieved at 2-year follow-up.