Surgical Management
 of
Degenerative Lumbar Stenosis and Spondylolisthesis

Lumbar Spinal Stenosis

 First of all, what is “stenosis”? OK, do you have a ring on your finger? Well imagine if the ring thickened and did so inward as well as outward. Ouch!

Stenosis is a word that means that the hole in something is too small for what is supposed to be in it. or pass through it.

Coronary artery stenosis is when the arteries are too narrow for the blood flow that is required.

But bones can thicken as well. Injury can leave new bone piled up from healing fractures. But arthritic joints or joints just beaten down by wear & tear, can get knobby and thick the way you see on some folkes’ fingers.

Do you see that canal in the vertebral structure? In the lumbar spine a whole bunch of nerves pass through there going to where nerves go - taking exit through those side windows (foramina) as they reach their specific levels. Both the canal and those foramen exits are subject to being squeezed short of space by too much bone, or knobby bone. When that happens the narrowing squeezes nerves and can hurt.  It’s a broad generalized squeeze and so the symptoms are not so pin point specific as with a simple thingy pinching a nerve in one spot. On cross sectional scan, the canal goes from looking happy and triangularly round to unhappy clover leaf cramped.

The surgical management of lumbar spinal stenosis and degenerative spondylolisthesis is critically shaped by whether a spinal arthrodesis (that means bone fusion of the moving interfaces, instrumented or noninstrumented) is performed along with the decompressive procedure.

Although the conditions under which these choices are made have not been fully and absolutely defined, the literature provides positive guidelines once the disorders are definitively diagnosed. Differentiation of these conditions is therefore a first step towards optimal management.

Complaints from patients with lumbar stenosis and degenerative spondylolisthesis include
back and leg pain; neurologic symptoms such as numbness, tingling, dysesthesia (odd sensations or wrong sensation, dull feels sharp, or pin feels like sparks etc); and subjective weakness often exacerbated by either prolonged standing or walking.

Fixed neurologic deficits may be absent or subtle in the form of reflex changes and/or mild bowel or bladder difficulties. Significant fixed motor paralysis and/or significant bowel or bladder symptoms are less common, and may be seen in neglected cases or, even less commonly, in acute presentations. However, patient symptoms do not definitively differentiate pure lumbar stenosis from degenerative spondylolisthesis. Why? Well the same nerves can be abused by general squeezing as a ring getting tighter (stenosis) or by two adjacent rings shifting and shearing the transition closed.

Common nonoperative measures to treat a diagnosis of either stenosis or spondylolisthesis include active physical therapy, pharmacologic management, and injection techniques for steroid medications. Failure of an adequate and coordinated program of conservative care is an indication for consideration of operative treatment. Since rapid neurologic deterioration is relatively rare, the vast majority of surgery for lumbar stenosis/degenerative spondylolisthesis is elective. In other words, if you can stand it the surgeon can stand you standing it. Surgeons only get testy when the next sign or symptom is something that can’t be undone.

Radiologic Imaging

 The differentiation of pure lumbar stenosis from degenerative spondylolisthesis begins with plain radiographs and dynamic lateral flexion and extension x-rays. The patient’s symptoms should correlate with the pathologic anatomy noted on all preoperative imaging studies. Greater than 4 mm of anterior translation of the superior vertebral body on the inferior body constitutes degenerative spondylolisthesis. Standing lateral flexion and extension x-rays may provide additional evidence of dynamic instability to supine lateral flexion and extension views.

Neural compression is documented well by MRI imaging. Increased sophistication in the technology and interpretation of MRI scans, with or without supplemental CT images, has decreased the “mandatory” usage of CT-myelography (a way to see not just the bones but the nerves and spinal cord as well) for all surgical patients. Some radiologic facilities will supplement MRI images with select CT cuts through the spine areas where maximal compression has occurred. A CT image better defines the bony architecture of the spinal column, while an MRI scan better depicts the soft neural structures. The CT scan will also provide information on the extent of the neural compression due to bone involvement. Neural compression is usually due to a reduction of the spinal canal from posterior protrusion of the disc material, hypertrophy of both the facets and ligamentum flavum and from the listhesis.

The what? The ligawhatsis whoozis? We have shown bones with very few ligaments. The joints don’t just sit there exposed. The space between the vertebral posterior elements is spanned by a flat yellowish ligament (Latin: Ligamentum Flavum - yellow ligament).

It tries. It does. When things are slipping where they ought not be, this ligament will thicken and do its best to hold. But given failure, that thickening adds to the bulk of stuff landing on the nerves. It is part of what needs to be removed, at times.

And listhesis is the horrible word for slippage. Let’s take a time out here. These words are just awful. Back when there was bubonic plague and no television this is what kept some folks busy.

Spondylo = ‘of the spine’
Spondylo- lysis = a discontinuity or fracture in the integrity of the spine
              (but only on the back side, though).
Spondylo- listhesis = a slippage of one vertebra off the one below it by some amount.
Spondylo- sis? Well, osis means not doing so well, and in this usage by way of
             a knobby kind of arthritis.
Spondyl-itis? itis is an inflammation. Can be rheumatism or infection, more words
           needed to make clear.
No wonder you’re confused.

Surgical Intervention

 The purpose of any surgical intervention is to decrease pain, improve function, and prevent neurologic deterioration. The goal of surgical decompression is to decompress all of the neural elements that are producing the patient’s symptoms. Degenerative changes may span multiple vertebral levels on imaging studies, but not all levels may be involved in production of the patient’s symptoms at the time of examination.

Simple laminectomy (when the surgeon unroofs the canal at the tight point) alone is the standard surgical treatment for lumbar spinal stenosis that is not associated with spondylolisthesis or degenerative scoliosis. The goal of decompression is to relieve the thecal sac (The cord and nerves run within an envelope with several layers called the thecal sac. It bathes the contents with spinal fluid) and to decompress nerve roots (nerves that exit the sac en route to stuff they have to do) from any local impingements (jabbing, pressing, poking) causing pressure or irritation: centrally from the spinal canal, through the lateral recess, and into the neural foramen (the exit windows from the canal). When fusion is to be performed, there is less concern about the precise amount of facet removal. However, care must be taken to avoid destroying the pars interarticularis, which will unnecessarily destabilize the spine, potentially diminishing the fusion rate. 

 The lamina, hypertrophic ligamentum flavum, and osteophytic (bumps of bone) areas of facet joints may all contribute to the stenosis and therefore require removal. The excess ligamentum flavum should be removed prior to the facetectomy (removing the small facet joint). The facet joint may be removed by means of an undercutting of the medial aspects of both facets. Fusion must be considered if greater than 50% of either facet is removed. 

A limited laminectomy, or hemilaminectomy, has also been described for the treatment of spinal stenosis. In this procedure, the central portion of the neural arch is preserved. Thus, the interspinous and supraspinous ligaments remain intact, minimizing spinal instability. Hemilaminectomy is indicated for patients with unilateral stenosis and unilateral symptoms. However, this procedure potentially makes it difficult to decompress the contralateral side or to perform adequate decompression of ipsilateral foramen. This is, in part, due to the difficulty in angling instruments laterally to enter the foramen in the presence of intact spinous process and midline ligaments.

Some surgeons advocate this procedure through a smaller incision using a microscope. However, there is an increased risk of a dural (that thecal sac) tear with this approach due to working through a small access portal. If a dural tear does occur in this situation, a full bilateral laminectomy is needed for further exposure and subsequent repair of the dural tear so that spinal fluid does not go on leaking.

There are versions of surgeries you might hear about wherein the removal of substance requires bone graft with a body cast as mandatory postoperatively for a minimum of two weeks in order to avoid stress on the construct once up walking.

 Discectomy is generally not required. True herniations are uncommon. However, the surgeon should assess each case for the possibility of a concomitant disc herniation or hard ridge which might compress the root. In the presence of a markedly bulging disc or in the case of a true soft disc herniation that is contributing to significant nerve root compression, a discectomy may be needed This being said, a discectomy may also cause subsequent spinal instability, since both anterior and posterior elements are sacrificed. In this circumstance, some surgeons recommend arthrodesis at the time of surgery. Spinal stability should be maintained during decompression by preserving both the pars interarticularis and the facet joints. However, in many cases, much of the facet joint may need to be removed for adequate decompression of the involved nerve root. If more than 50% of the facet joint is removed, postoperative instability may occur. In addition, excessive removal or thinning of the pars interarticularis may lead to postoperative fracture and/or instability. If postoperative instability is suspected based on the degree of decompression performed, then arthrodesis is recommended in addition to decompression.

 Surgeons are often faced with the question of whether to decompress stenotic levels that are not symptomatic. In general, if a given stenotic area is not believed to be contributing to a patient’s symptoms, decompression of that particular level is not considered mandatory.  Certain patients may present with a clear monoradiculopathy (single nerve pinch) with multilevel stenosis. An isolated single unilateral decompression can sometimes be performed. Most patients present with more complex symptoms. A preoperative selective nerve root block may assist in confirming the symptomatic level or side.

Decision-making in Surgical Intervention

 First and foremost, decision-making in lumbar stenosis involves differentiating between the two entities of stenosis and spondylolisthesis as the cause of the patient’s woe. Pure lumbar stenosis is frequently found in combination with significant osteoarthritic changes, often with large osteophyte (knobs of extra bone) formations similar to those on gnarly fingers. Pure degenerativespondylolisthesis is frequently manifested as a Grade I spondylolisthesis of L4 on L5, and is more frequent in females than males. There is an overlap of radiologic findings between these two entities which requires further categorization. Each level of the lumbar spine can be assessed preoperatively for individual stability based on disc height, angular motion of the endplates, translation as measured on plain radiographs, or fixed or mobile translation as evaluated on dynamic radiographs. Unfortunately, the pre-operative assessment of stability loses significance after destabilizing decompressive procedures are performed.

Surgical Outcome for Spinal Stenosis

Surgical outcome for lumbar spinal stenosis is quite varied. In a prospective, nonrandomized observational cohort study of patients with spinal stenosis followed for one year, 55% of surgical patients reported definite improvement. This was in contrast to the non-surgical patients, of whom only 28% reported a satisfactory outcome.[4] In a prospective study of 105 consecutive patients undergoing decompressive laminectomy, a 63-67% rate of satisfactory results was reported at 2 years. This result deteriorated to 52% at 5-year follow-up.[5] Sixteen percent of these patients underwent re-operation for severe back pain and/or recurrence of their stenosis during the 5-year period. Risk factor for poor outcome was correlated to a preoperative duration of symptoms of more than 4 years, significant comorbidity, and preoperative back pain. In another series of 140 patients treated surgically, at an average follow-up of three years, 71% reported an improvement in back pain and 82% improvement in leg pain.[6] In a longer follow-up of 2.8 to 6.8 years of 88 patients with decompression laminectomy, Katz concluded 11% of patients had poor results at 1 year.[7] This poor satisfactory result later increased to 43% with a re-operation rate of 17% at final follow up. Again, poor outcome was correlated to preoperative comorbidities and limited decompression. Turner et al. performed a meta-analysis of the lumbar stenosis literature and noted a 64% mean proportion of good to excellent results over the long term.[8]

 Most studies indicate that decompression alone is adequate in pure lumbar stenosis without significant spondylolisthesis or other deformity. In a prospective randomized study, by Grob et al., 45 patients underwent decompression or decompression with arthrodesis for pure stenosis. There was no significant difference in clinical outcome among patients.[9] Overall satisfactory results were 78% for patient-related outcome data in all groups, including decompression without arthrodesis, decompression plus fusion of the most significant stenotic segment, and decompression with arthrodesis of all stenotic levels. They concluded that lumbar spine decompression alone changed the natural history of this disease with improvement in quality of life. They also determined that arthrodesis is indicated when stenosis is associated with degenerative spondylolisthesis, scoliosis or kyphosis, recurrent stenosis at the same level, stenosis adjacent to a prior fusion, aggressive facetectomy, or need for a disc excision. Other prospective randomized studies have concurred on the role of fusion for stenosis associated with degenerative spondylolisthesis.[10,11]

Complications associated with surgical intervention for lumbar stenosis are more common in cases of increased preoperative morbidities, advancing age, and complex surgical procedures. Two studies have demonstrated a relationship between mortality rate and age. One study showed a higher mortality rate of 0.6% in patients older than 75 yrs (about nine-fold compared to patients under 75 yrs) with a complication rate of 17.7% (compared to 9.1%).[12] The second study showed similarly increased rates for patients over 80 years of age.[13] The most commonly cited comorbidities in the literature are osteoarthritis, cardiac disease, rheumatoid arthritis, and chronic pulmonary disease. However, the risk factors most closely correlated with a poor outcome are preoperative complaints of predominantly low back pain, followed by preoperative comorbidities. Complications of decompression procedures are postoperative neurologic deficit, dural tear, CSF fistulas and pseudomeningoceles, facet fractures, infection, and vascular injury.

 When conservative measures have failed, stenosis is a condition aptly managed by a surgical decompressive procedure: a full or limited laminectomy, a double hemilaminotomy, or a laminoplasty. The majority of patients report a satisfactory outcome following surgery, though the absolute duration of long-term benefits has not been established. If stenosis is associated with an uncommonly found disc herniation, significant degenerative spondylolisthesis, degenerative scoliosis, or aggressive decompression, arthrodesis is recommended.

Spinal Stenosis with
Degenerative Spondylolisthesis

 Degenerative spondylolisthesis is described as the anterior translation of one vertebral body over another adjacent vertebra in the absence of a defect of the pars interarticularis.  The listhesis may cause lower back pain, radicular pain (pain shoots down a narrow strip of the leg, like a stripe on a candy cane), and/or symptoms of neurogenic claudication (aches with walking to the point of nasty cramp). The main goal of treatment in spinal stenosis with degenerative spondylolisthesis is decompression of both the exiting and traversing nerve root. The role of arthrodesis, with or without instrumentation, in the treatment of spinal stenosis with degenerative spondylolisthesis is controversial. In a retrospective review of 290 patients who underwent decompression laminectomy with 10-year follow-up, the reported outcome was excellent in 69%, good in 13%, fair in 12%, and poor in 6%. Re-operation rate for pseudoarthrosis (failed fusion) was only 2.7%.[14] A prospective randomized study conducted by Herkowitz and Kurz compared the results at 3-years follow-up of decompression alone versus decompression and intertransverse arthrodesis in patients with one level of spinal stenosis and degenerative spondylolisthesis.[10] Only 44% of patients with decompression without fusion reported a satisfactory outcome compared with 96% of patients reporting the same outcome who received decompression plus fusion. Patients who underwent concomitant arthrodesis had significantly better results. Moreover, despite the pseudoarthrosis rate of 36% in patients who underwent decompression and in-situ fusion, all had good to excellent results. Significant progression of the slip did not occur in either group. The authors concluded that those patients with degenerative spondylolisthesis and stenosis should undergo concomitant arthrodesis at the time of decompression.

 An attempted meta-analysis of the literature on degenerative spondylolisthesis was performed by Mardjetko et al.[15] This analysis:

 An instrumented arthrodesis has been shown to produce higher fusion rates; however, the clinical outcome of decompression with instrumented spinal fusion for this entity is not completely known.[16] Fishgrund et al. examined 67 patients undergoing decompression and arthrodesis with or without instrumentation.[17] Patients undergoing the instrumented arthrodesis demonstrated an 87% fusion rate while those patients undergoing a non-instrumented arthrodesis had a 45% fusion rate. However, the higher fusion rate of the instrumented group did not improve their clinical outcome.  A landmark follow-up study of longer duration by Kornblum et al. reviewed 47 of the original patients who were diagnosed with 7 years and 8 months :

Because fusion performed with instruments will improve the likelihood of a solid fusion, this would suggest that an instrumented arthrodesis in the treatment of degenerative spondylolisthesis is preferred over noninstrumented fusion.

Conclusions

 For patients who are indicated for surgery for either degenerative lumbar stenosis or spondylolisthesis, the choice and combination of procedures planned is critically tied to a careful diagnosis supported by a thorough correlation of symptoms and radiographic evaluation. As well in the perioperative planning, there must be a consideration of the extent of disease, adequacy of decompression, and instability that may be surgically produced. Pure lumbar stenosis may be managed by simpler surgical procedures with risk of fewer complications, but if the stenosis is already complicated by degenerative or instability from some prior procedure, arthrodesis should at least be considered. If stenosis is accompanied by degenerative spondylolisthesis, arthrodesis is strongly indicated. For the primary condition of degenerative spondylolisthesis, the choice of fusion is unambiguous, with instrumentation being weighed in the balance. Most recently, however, research appears to indicate that an instrumented arthrodesis, as opposed to a noninstrumented procedure may provide the patient’s best opportunity for long-term clinical benefit. Finally with the SPORT study we have high levels of evidence to support surgical intervention in patients who have failed conservative treatment.

References

• 1) Wiltse LL, Newman PH, Macnab I: Classification of spondylolisis and spondylolisthesis. Clin Orthop 117:23--29, 1976.
• 2) Postacchini F, Cinotti G, Perugia D, et al. The surgical treatment of central lumbar stenosis. Multiple laminotomy compared with total laminectomy. J Bone Joint Surg Br 75:386--392, 1993.
• 3) Matsui H, Tsuji H, Sekido H, et al: Results of expansive laminoplasty for lumbar spinal stenosis in active manual workers. Spine 17:S37--S40, 1992
• 4) Atlas SJ, Deyo RA, Keller RB, et al: The Maine Lumbar Spine Study, Part III. 1-year outcomes of surgical and nonsurgical management of lumbar spinal stenosis. Spine 21(15):1787--1794, 1996.
• 5) Jonsson B, Annertz M, Sjoberg C, et al: A prospective and consecutive study of surgically treated lumbar spinal stenosis, Part II. Five year follow-up by an independent observer. Spine; 22:2938--2944, 1997.
• 6) Herron LD, Mangelsdorf C: Lumbar spinal stenosis. J Spinal Disord 4:26--33, 1991
• 7) Katz JN, Lipson SJ, Larson MG et al: The outcome of decompressive laminectomy for degenerative lumbar spinal stenosis. J Bone Joint Surg Am 73:809--813, 1991.
• 8) Turner JA, Ersek M, Herron L et al: Surgery for lumbar spinal stenosis: Attempted meta-analysis of the literature. Spine 17:1--8, 1992.
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• 10) Herkowitz HN, Kurz LT: Degenerative lumbar spondylolisthesis with spinal stenosis. A prospective study comparing decompression with decompression and intertransverse process arthrodesis J Bone Joint Surg Am 73:802--807, 1991.
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• 12) Deyo RA, Cherkin DC, Loeser JD et al: Morbidity and mortality in association with operations on the lumbar spine. The influence of age, diagnosis, and procedure. J Bone Joint Surg Am 74(4):536--543, 1992.
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• 17 Fischgrund JS, Mackay M. Herkowitz HN et al: 1997 Volvo Award winner in clinical studies. Degenerative lumbar spondylolisthesis with spinal stenosis: a prospective randomized study comparing decompressive laminectomy and arthrodesis with and without spinal instrumentation. Spine 22:2807--2812, 1997.
• 18 Thomsen K, Christensen FB, Eiskjaer SP et al: 1997 Volvo Award winner in clinical studies. The effect of pedicle screw instrumentation on functional outcome and fusion rates in posterolateral lumbar spinal fusion: a prospective, randomized clinical study. Spine. 22(24):2813--2822, 1997.
• 19 Zdeblick TA: A prospective, randomized study of lumbar fusion. Preliminary results. Spine 18(8):983--991, 1993.