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Discussion: Isthmic Spondylolisthesis: Reduction vs. In-Situ Fusion?

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Part 5: Isthmic Spondylolisthesis: Reduction vs. In-Situ Fusion?
Discussion
The issue of neurologic compromise is at the forefront of every surgeon's mind when reduction of Spondylolisthesis is entertained. The cited literature indicates that reduction of grade 3 and 4 Spondylolistheses and Spondyloptoses typically produces neurologic L5 root symptoms in 10 %–20 % of patients.

The study of published approaches to the reduction of Spondylolisthesis reveals evidence of substantial but poorly controlled force being applied to the interspace in the form of posteriorally directed translation as well as distraction. The exact degree of distraction during reduction is not recorded in any of the abovementioned literature. Petraco's study reveals a severe increase in L5 root tension at the time of disc distraction [14]. Their study does show substantial increase in the distance between the L5 pedicle and anterior upper sacrum at the time of reduction. However, the study fails to consider other causes of L5 root injury such as intraoperative trauma to the root, inadequate neural decompression, or lumbosacral ligament compression. The study also assumes that the length of the L5 root is the same as the distance from the pedicle to the anterosuperior border of S1. It should be realized that the total spinal canal length (from L1 to S1) is significantly shortened at the time of reduction. Furthermore, one should appreciate that nerve roots typically slide in and out of the foramen throughout activities of daily living. Actual L5 root tension results from canal lengthening, L5 root stretch, L5 root mobility, degree of disc distraction, and reduction of kyphosis.

The key to a safe reduction is to utilize carefully controlled force and limited distraction amounting to no more than physiological disc space height. Our case series of 22 patients with grade 2 and 3 isthmic Spondylolisthesis reduction utilizing the SOCON Spondylolisthesis Reduction System produced no neurologic deficits. It should be noted that anatomic reduction in 19 of our 22 patients was achieved, whereas all other groups excepting that of Ani have achieved only one third to one half average reduction of the Spondylolisthesis. The SOCON Spondylolisthesis Reduction System achieves precise and controlled reduction through levered forces applied to the L5 and S1 bodies. Simultaneous translation and slip angle correction is achieved via the mechanism of derotation. Studies with long-term follow-up are necessary to clearly substantiate the relative merits and disadvantages of Spondylolisthesis reduction.

Clearly, reduction of grade 4 and 5 Spondylolisthesis is problematic. This study does not address this challenging problem. Substantial evidence has been accumulated to suggest that a significant portion of the surgical trauma involving the L5 roots at the time of Spondylolisthesis reduction may be associated with compression of the L5 roots underneath the lumbosacral ligament. Until the exact etiology of L5 root trauma during Spondylolisthesis reduction is established, routine release of the lumbosacral ligament via an anterior or posterior approach during attempted reduction of grade 4 and 5 Spondylolisthesis seems prudent.

Literature
1. Albrecht S, Kleihues H, Gill C, Reinhardt A, Noack W (1988) Repositionsverletzungen der Nervenwurzel L5 nach operativer Behandlung hohergradiger Spondylolisthesen und Spondylooptosen In Vitro Untersuchungen. Z Orthop 136:182–191.

2. Ani N, Keppler L, Biscup RS,Steffee AD (1991) Reduction of high-grade slips (grade III-IV) with VSP instrumentation, report of a series of 41 cases. Spine 16:S302–S310.

3. Boos N, Marchesi D, Zuber K, Aebi M (1993) Treatment of severe spondylolisthesis by reduction and pedicular fixation, a 4- to 6-year follow-up study. Spine 12:1655–1661.

4. Danforth MS, Wilson PD (1925) The anatomy of the lumbosacral region in relation to sciatic pain. J Bone Joint Surg 7 A:109–160.

5. Dick WT, Schnebel B (1988) Severe spondylolisthesis, reduction and internal fixation. Clin Orthop 232:70–79.

6. Gaines RW, Nichols WK (1985) Treatment of spondyloptoses by two-stage L5 vertebrectomy and reduction of L4 onto S1. Spine 10:680–686.

7. Hu SS, Bradford DS, Transfeldt EE, Cohen M (1996) Reduction of high-grade spondylolisthesis using Edwards instrumentation. Spine 21:367–371.

8. Kleihues H, Albrecht S, Noack W (2001) Topographic relations between the neural and ligamentous structures of the lumbosacral junction: in vitro investigation. Eur Spine J 10:124–12.

9. Lehmer SM, Steffee AD, Gaines RW (1994) Treatment of L5-S1 spondyloptosis by staged L5 resection with reduction and fusion of L4 onto S1 (Gaines procedure). Spine 17:1916–1925.

10. Maurice HD, Morley TR (1989) Cauda equina lesions following in situ and decompressive laminectomy for severe spondylolisthesis. Four case reports. Spine 14:214–216.

11. Molinari RW, Bridwell KH, Lenke LG, Ungacta FF, Riew KD (1999) Complications in the surgical treatment of pediatric high-grade isthmic spondylolisthesis: a comparison of three surgical approaches. Spine 24:1701–1711.

12. Nathan H, Weizenbluth M, Halperin N (1982) The lumbosacral ligament, with special emphasis on the "lumbosacral tunnel" and the entrapment of the fifth lumbar nerve. Int Orthop 6:197–202.

13. Olsewski JM, Simmons EH, Kallen FC, Mendel FC (1991) Evidence from cadavers suggestive of entrapment of fifth lumbar spinal nerves by lumbosacral ligaments. Spine 16:336–347.

14. Petraco DM, Spivak JM, Cappadona JG, Kummer FJ, Neuwirth MG (1996) An anatomic evaluation of L5 root stretch in spondylolisthesis reduction. Spine 21:1133–1138.

15. Saraste H (1987) Long-term clinical and radiological follow-up of spondylolysis and spondylolisthesis. J Pediatr Orthop 7:631–638.

16. Sasso RC, Kozak JA, Dickson JH (1993) Release of the lumbosacral ligament via an anterior approach. Spine 18:2127–2130.

17. Schoenecker PL, Cole HO, Herring JA, Capelli AM, Bradford DS (1990) Cauda equina syndrome after in situ arthrodesis for severe spondylolisthesis at the lumbosacral junction. J Bone Jt Surg Am 72:369–377.

18. Smith JA, Deviren V, Berven S, Kleinstueck F, Bradford DS (2001) Clinical outcome of transsacral interbody fusion after partial reduction for high-grade L5-S1 spondylolisthesis. Spine 26:2227–2234

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

Updated on: 12/10/09

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Todd 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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