Clinical Series of Spondylolisthesis Reductions

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Part 4: Isthmic Spondylolisthesis: Reduction vs. In-Situ Fusion?
In order to evaluate the issue, the author's institution began a clinical series of Spondylolisthesis reductions approximately 18 months ago utilizing the SOCON Spondylolisthesis Reduction System. To date, 41 patients with grade 2 and 3 Spondylolisthesis have undergone surgical treatment after failure of conservative treatment. There were 22 attempted Isthmic Spondylolisthesis Reductions and 19 attempted Degenerative Spondylolisthesis Reductions within this group. Within the isthmic Spondylolisthesis subgroup there were 13 men and nine women with an average age of 43 years (range 12–75). There were 13 grade 2 Spondylolistheses and 9 grade 3 Spondylolistheses. All isthmic Spondylolisthesis patients presented with back pain and significant L5 root symptoms, except for one patient who presented with severe back pain only. Preoperatively, 17 patients presented with varying degrees of L5 root motor deficits, while 20 patients presented with L5 root sensory deficits. There was no preoperative cauda equina symptomatology, with the exception of a 45-year-old woman with intermittent delayed initiation of micturation and occasional incontinence.

The isthmic defects were located in the L5 segment in 19 patients, while the Spondylolisthesis was at the L4-5 segment in three patients. All patients underwent a Gill procedure at the involved segment and aggressive débridement of the pars interarticularis defects. During the same operative session, the patients underwent reduction of their Spondylolisthesis, utilizing the SOCON reduction instrumentation followed by SOCON pedicular instrumentation, and posteriorlateral fusion, utilizing iliac or local autogenous bone. In addition, all patients except one 12-year-old girl were treated with an interbody graft at the Spondylolisthesis site; there were 14 posterior lumbar interbody fusions and 7 anterior lumbar interbody fusions (see Figs. 8 and 9).

pre- and post-op x-rays grade 2 spondylolisthesis
Figure 8a,b:
A typical patient in this series with a nicely reduced
grade 2 Spondylolisthesis. a) Preoperative X-ray; b) postoperative X-ray

pre- and post-op x-rays grade 2 spondylolisthesis, SOCON Spondylolisthesis Reduction Instrumentation
Figure 9a, b:
Grade 3 isthmic Spondylolisthesis patient with a safe near-anatomic
reduction utilizing the SOCON Spondylolisthesis Reduction Instrumentation.
a) Preoperative X-ray; b) postoperative X-ray

Follow-up ranged from 3 to 18 months (average 10 months). Anatomic reduction of the Spondylolisthesis was defined as a reduction with 3 mm or less remaining Spondylolisthesis. Based on this definition, 19 of the 22 patients demonstrated anatomic reduction at last follow-up. There was only one case of instrumentation failure, in a 12-year-old girl with a grade 3 L5/S1 Spondylolisthesis who had undergone isolated posterior-lateral fusion after anatomic reduction without an interbody graft. The reduction was lost when the instrumentation failed. This patient underwent repeat reduction and instrumentation revision followed by an anterior lumbar fusion. At 18 months of follow-up she is complaining of back pain, and radiographs reveal maintenance of her anatomic reduction at L5/S1, but a grade 1 degenerative Spondylolisthesis has developed at L4–5. One patient developed an L5 pedicle fracture during reduction and it was elected to abandon the reduction and proceed with an in-situ fusion. Finally, there was a 39-year-old woman with a grade 3 Spondylolisthesis who underwent anatomic reduction during her procedure; however, the L5 roots appeared excessively tight and it was elected to lessen her reduction to 50 %.

Intraoperative complications, including one dural tear, were treated with repair without postoperative sequelae. Average blood loss was 422 cc (range 100–725 cc) with an average operative time of 3 hours and 45 minutes (range 152–295 minutes). There were no wound infections. One urinary tract infection developed one week after the patient was discharged from the hospital.

There was no neurologic deterioration in any patient in response to the reduction. All patients experienced relief of their preoperative radiculopathy, with the exception of a 47-year-old woman who reported continued preoperative right L5 radicular leg pain at 12 months followup. All patients demonstrated complete resolution of their preoperative neurologic deficits. The above-mentioned patient with preoperative bladder symptoms reported immediate resolution of her symptomatology following her procedure. 20 of the 22 patients reported marked improvement in their preoperative symptoms and were pleased with their result.

Solid fusion was defined as trabeculated bone across the interbody graft with no motion seen at the time of superimposition of flexion and extension films obtained at their 6 months followup. Posterior-lateral bone formation was variable and was not used in the classification of arthrodesis. 16 patients were followed up for a minimum of 6 months, and 15 of these exhibited a solid fusion. The remaining patient exhibited faint radiolucent lines around his interbody graft at 12 months follow-up, but complete stability was noted on the flexion and extension films.

Backup, 2-2002, Aesculap AG & Co. KG Tuttlingen

Updated on: 09/26/12
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Discussion: Isthmic Spondylolisthesis: Reduction vs. In-Situ Fusion?

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Todd J Albert, MD
This series of short papers on isthmic spondylolisthesis is well-written, concise, and well-referenced. I agree almost universally with the points raised by Dr. Kozak. In our center we also add free run EMG monitoring for the lumbosacral roots during reduction of isthmic spondylolisthesis. While many techniques have been described, the technique of distraction/translation and levered reduction appear to be the two most popular and enjoy the lowest complication rates, albeit certainly not zero. The reader should not forget the possibility of performing an in situ arthrodesis with a fibula drilled from sacrum through the endplate and into the body of L5 (modified Speed procedure) for high grade slips. This can be supplemented by posterior instrumentation and posterolateral fusion and also enjoys a very high success rate without a substantive neurologic complication rate. Dr. Kozak is to be complimented on his thoughtful and comprehensive reviews. The surgeon should be mindful of the challenges of these procedures prior to translating the results of surgeon advocates to their own practice.
Baron S. Lonner, MD
Dr. Kozak provides a thorough, yet concise review of the entity of isthmic spondylolisthesis. The various etiologies of nerve root compression from the disorder are well-described, as is the risk of neurological deterioration with reduction of high-grade slippage. Emphasis should be placed on visualization and assessment of tension and compression of the involved nerve roots (i.e. L5 in L5/S1 spondylolisthesis) during reduction. Shortening of the spinal column with a sacral dome osteotomy for example, and avoidance of large structural interbody grafts, may help to lessen the incidence of deficits related to tension on the nerve roots. Although we routinely employ free-running EMGs at our institution, they may not detect stretch injuries at the time of surgery. Direct nerve root stimulation has been advocated as a technique to assess the integrity of the nerve root at the time of reduction (Shufflebarger, et al.) and may be more effective in that regard. The importance of the lumbosacral ligament is not often alluded to and is a valuable point of this article. In previous series, L4-sacrum or more cephalad levels of arthrodesis was often advocated for lumbosacral spondylolisthesis. The advantage of a reduction maneuver is that monosegmental fusion can be achieved perhaps lessening the long-term consequences of adjacent segment degeneration. More important than translation reduction is the restoration of sagittal alignment as measured by slip angle. As pointed out by Dr. Kozak, long-term studies will perhaps point to the benefits of reduction of isthmic spondylolisthesis.
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