Surgical Treatment of Isthmic Spondylolisthesis

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Part 2: Isthmic Spondylolisthesis: Reduction vs. In-Situ Fusion?
The literature is replete with reports of studies on various surgical treatments of isthmic Spondylolisthesis. Some surgeons routinely decompress the neural elements via a Gill procedure and foraminotomy, while others utilize decompression only in the face of substantial neurologic deficit. Arthrodesis options include isolated anterior fusion, isolated posterior fusion, or circumferential fusion via ALIF, PLIF or TLIF. Most surgeons utilize pedicular fixation when arthrodesis of adult isthmic Spondylolisthesis is undertaken.

Other options for surgical reconstructive treatment include in-situ fusion or reduction with subsequent fusion. For decades, proponents of reduction have cited the advantages of improved clinical results, restoration of normal anatomy, improved fusion rates due to better apposition of the vertebral bodies, and superior loading of the chosen bone grafts, as well as improved appearance. Those surgeons who elect to avoid reduction typically agree with these advantages, but they are unwilling to accept the described neurologic risk associated with reduction of isthmic Spondylolisthesis.

The neurologic risk associated with reduction of isthmic Spondylolisthesis ranges in the literature from 0% to 20% [2,3,5,7,11]. Molinara et al. conducted a review of 33 patients treated surgically for grade 3–4 isthmic Spondylolisthesis and reported 4/26 (15 %) patients with neurologic deficits attributed to their reduction (average reduction of two Meyerding grades) [11]. Two of these patients' neurologic deficits were temporary; one required re-operation and the other exhibited a permanent footdrop. Ani and Steffee reported a neurologic injury rate of 4/41 patients (10 %) who underwent Spondylolisthesis reduction (average reduction of 68 % preoperative slip to 6% postoperative slip), two of whom exhibited permanent footdrop [2]. Bradford et al. described neurologic injury of 19 % in the reduction of grade 3–4 Spondylolisthesis; one deficit was permanent (average reduction of 89% preoperative slip to 29 % postoperative slip) [7]. Recently, Bradford et al. published a different approach whereby minimal correction of the Spondylolisthesis was attempted but substantial correction of the slip angle was accomplished [18]. The reported neurologic deficit rate was 15 % and all deficits were temporary. Boos et al. reported a neurologic deficit rate of 20 % at the time of Spondylolisthetic reduction, but all deficits were temporary (average of 78 % preoperative slip to 39 % postoperative slip) [3]. Albrecht et al. reported a detailed analysis of attempted Spondylolisthesis reductions and found neurologic deficits in two of 54 grade 1–2 reductions (both temporary), in none of three grade 3 reductions, and in eight of 11 grade 4–5 reductions (three were permanent) [1]. Interestingly, the neurologic deficits in Albrecht's series all developed more than 72 h postoperatively. The exact amount of reduction is not recorded in their article.

Lehmer et al. described the Gaines procedure, i.e., L5 vertebral body resection in an effort to reduce neurologic complications associated with grade 4–5 Spondylolisthesis [6]. This procedure is a major undertaking and the reported complication rate is as high as 75 % [9]. It has been said that the neurologic complication rate may be as high with this procedure as with traditional Spondylolisthesis reduction (J.P. Kostuik 2002, personal communication).

The literature provides interesting information regarding the role of an interbody graft in patients who undergo arthrodesis for treatment of Spondylolisthesis. In Molinari's paper, a 45 % rate of pseudarthrosis was seen in patients who underwent isolated posterior-lateral in situ arthrodesis [11]. A non-union rate of 29 % and an instrumentation failure rate of 29 % were seen in patients who underwent reduction and posterior-lateral fusion. Finally, a pseudarthrosis rate of 11 % and an instrumentation failure rate of 16 % were seen in patients treated with reduction and circumferential fusion.

Hu and Bradford reported a 25 % instrumentation failure and pseudarthrosis rate in partially reduced patients with an isolated posterior-lateral arthrodesis [7].

Boos reported a pseudarthrosis rate of 91 % in patients with reduction followed by isolated posterior-lateral fusion, but they achieved a 0% pseudarthrosis rate when a circumferential fusion was chosen [3]. John Kostuik has extensive experience with Spondylolisthesis reduction and concurs that an interbody graft is mandatory (J.P. Kostuik 2002, personal communication). Therefore, it would seem that a circumferential fusion is a reliable mechanism to minimize the chance of pseudarthrosis.

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

Updated on: 09/26/12
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Evaluation of Neural Tension at the Time of Spondylolisthesis Reduction

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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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