Surgical Situations of Complex Decision-Making Abstract In the SFC approach to PDLS surgery, the surgeon assesses each patient as an individual case, factoring in the many clinical factors, and the radiographic presentation, in the attempt to make the appropriate therapeutic decision. The formulation of this decision can be complex in common scenarios. Patients often present with incapacitating claudication from stenosis at a level with degenerative spondylolisthesis. The decision for, or against, adjunctive stabilization at the time of decompression requires an evaluation for antigravity axial pain, and a thorough assessment of radiographic features. A significant number of these patients are stable; others are clearly not so, requiring stabilization. In those patients with radiographic ambiguity as to stability, the individual clinical features must have greater directive force for the surgeon. Sagittal alignment should be assessed in patients requiring multi-level decompression for stenosis, as significant SIB may predispose for poor outcomes secondary to low back pain. T1 pelvic axis (TPA) may be the best measure in this assessment. The decision for/against stabilization is relative to the extent of TPA abnormality and to individual clinical factors. Frequently, the PDLS surgeon is presented with a patient having chronic progressive incapacitating anti-gravity axial pain. The decision for therapeutic arthrodesis can be a difficult one, especially when there are multiple degenerative levels. In this situation, there is no present diagnostic capacity able to differentiate the pain-generator level. When there are one or two degenerative levels, then surgery can be considered, but only when a thorough clinical and radiographic evaluation reveals certain features. Keywords: lumbar stenosis, spondylolisthesis, Modic 1 changes, chronic axial lumbar pain, anti-gravity, sagittal imbalance, sagittal alignment Whoever thinks a faultless piece to see, Thinks what never was, nor is, nor ever shall be. Alexander Pope Symptomatic lumbar stenosis is commonly found with degenerative spondylolisthesis (DS) at the affected level. This stenosis most frequently results in primary radicular claudication involving the traversing root(s). There may be a chronic axial lumbar pain (CALP) component but this axial pain is likely related to underlying degenerative disc/interspace pathology. Spondylolisthesis is relatively prevalent and does not, of itself, contribute directly to lumbar pain either with or without spondylolysis. 1 The degenerative chronic axial lumbar pain, when coexistent with radicular pain, is most frequently antigravity pain (CALPag) to be distinguished from the sometimes para-axial lumbar pain (unilateral or bilateral) seen in stenosis induced by walking/standing, with or without overt LE (lower extremity) claudication (and may represent dorsal rami symptomatology). DS can be stable 2 and stabilization may not be required in selected patients. 3 Computed tomography (CT) scans may indicate arthrodesis in over 20% of cases, and such spontaneous fusion may be the common end-stage result in most instances. 4 The surgeon who is faced with decompression for stenosis, in the DS setting, must decide the likelihood of DS progression postoperatively, with potential recurrence of radicular symptoms. It must be acknowledged that noninstrumented decompression has the highest rate of survival without eventual need for secondary surgery when it can be done without significant risk for progressive slip. 5 The specific decompression technique may be factorial for this progression. 6 Furthermore, and as expected, decompression without fusion is significantly more cost effective. 7 A degeneratively fused segmental listhesis would need no prophylactic stabilization assuming judicious surgical removal of the posterior stability architecture. However, in the absence of such radiographic (CT) evidence of arthrodesis, the surgeon must rely on radiographic and clinical evidence of current “instability” though this term has not been clearly defined in this setting. The decision to fuse or not is multifactorial and individualized. The recommendations for fusion below are conservative, with other authors suggesting lower threshold for stabilization especially in regard to definition of translational instability. 8 CT scan: Evidence of facet fusion. Lateral and/or anterior osteophytes. Interspace: anterior elevation (“fish-mouthing”), parallel, anterior collapse. Magnetic resonance imaging (MRI) scan: Stenosis. Facet gapping = size of facet effusion 9 and size/shape and angle of facet orientation. Degree of anterolisthesis in the supine position. Modic changes. Standing lateral lumbar radiographs with flexion 10: Progression of listhesis from the supine position (MRI or CT scan) to the standing position. Increased translation in the flexed position. Rotation degree at the level of listhesis. Bone quality. Radiographic sagittal alignment (SA) evaluation: Sagittal vertical axis (SVA) and T1 pelvic axis (TPA); pelvic incidence-lumbar lordosis differential (PI-LL). If listhesis is “fish-mouthed,” then measurement of degree (vs. parallel endplates). Flexing/erecting: grade level of antigravity pain. Size/habitus of patient. CT evidence of stabilization: facet arthrodesis, disc height loss, fused bridging osteophytes, end plate sclerosis, ossification of anterior or posterior disc/ligament complex. No induced translational slip greater than 3 mm. No abnormal disc angle change with standing or flexion (physiologic rotation). Low grade antigravity pain (grade 0 or 1). Induced translational slip of greater than 3 mm and/or MRI facet effusion > 3.5 mm. 12 Rotational disc angle change resulting in loss of anterior disc height of at least 50%. Axial antigravity pain of at least grade 3. Measurable but less than 3 mm of induced translational slip (especially at L4–L5). 8 Obesity (BMI [body mass index] > 40). Maintained disc height (greater than 10 mm). 13 Axial antigravity pain of grade 2 with Modic I changes. Any facet effusion (T2 enhancement on MRI). Reduction is rarely necessary (with decompression) and can be detrimental. 14 Consideration of sagittal imbalance (SIB) as a causative factor. If interspace is “fish-mouthed” (representing bilateral pars defects), this may represent stress response to a preslip SIB and so interbody spacer and/or reduction may reduce its lordotic benefit (and throw patient back into a SIB). It is not necessary to extend an L4–L5 fusion to the sacrum when there is degenerative disc disease at L5–S1. 15 Noninstrumented fusion (with autograft) may be warranted in cases of osteoporosis or small pedicles. In a large retrospective cohort analysis, noninstrumented and instrumented fusions have been shown to have similar long-term complication and reoperation rates (with decreased costs of noninstrumentation). 16 In the acute postoperative phase, posterolateral fusion (PLF) alone has reduced complications and length of stay/charges compared to PLF in combination with interbody placement. 17 As stated earlier, sagittal alignment (SA) parameters must be given consideration whenever the surgeon anticipates the need for fusion. Patients with lumbar stenosis should also have sagittal parameters evaluated. Patients with neurogenic claudication will compensate by reducing their LL in order to increase ambulatory comfort. This may cause characteristic gate when the patient leans forward with flexed knees. Such standing posture will obviously distort SA parameters often resulting in measured SIB. With surgical decompression, there will be an improvement in the reactively diminished lumbar lordosis and SA as the patient can resume normal lordotic posture of the lumbar spine without pain. 18, 19 These studies suggested that both the LL and the TK (thoracic kyphosis) curves increase after decompression. The LL curves increased to a greater extent with positive net effect on SA, depending on the number of levels decompressed: 3 to 4 degrees with one to two levels and 6 to 7 degrees with three to four levels. In the place of SVA preoperatively, the measurement of TPA may prove to be a better preoperative measurement assessing the underlying intrinsic sagittal alignment and thus the need for correction beyond that provided by laminectomy alone. As the TPA is independent of pelvic compensation mechanisms (i.e., retroversion), any net corrective effect (LL-TK) will be reflected directly and proportionately in the TPA. However, the use of TPA in this setting is not as yet confirmed. As SIB can be an independent factor for LBP, 20 residual SIB (>50 mm) after lumbar decompression for stenosis would be expected to yield inferior results, especially in regard to pain and functional measurement. This has been shown to be the case and a delineation of preoperative SA > 80 mm (severe SIB) portends this possibility. 21 However, studies attributing postoperative LBP to SIB must take into account other LBP etiologies unaffected by sagittal balance. These possibilities would include residual radicular pain and/or degenerative discogenic pain. 22 The evaluation of neurogenic claudication from lumbar stenosis should include the following. MRI scan: Number of levels (including potential remote development). Central (hypertrophic ligamentum flavum) versus lateral recess stenosis. Radiologic SA evaluation/compensation: SVA, PI-LL, TPA. Sacrofemoral axis (as evidence for hip flexion). PT (pelvic tilt), PS (pelvic shift), KFA (knee flexion angle). Plain X-rays: AP (anteroposterior)/lateral L spines. Standing flexion/extension laterals.
10.1 Lumbar Stenosis with Degenerative Spondylolisthesis (L3–L4 or L4–L5): Fusion or Not
10.1.1 Introduction
10.1.2 Image Evaluation
10.1.3 Physical Examination
10.1.4 Stability of Spondylolisthesis 11
10.1.5 Major Indications for Consideration of Fusion
10.1.6 Relative Indications for Consideration of Fusions
10.1.7 Technical Considerations in Fusion
10.2 Lumbar Stenosis with Severe Sagittal Imbalance: Sagittal Correction or Not
10.2.1 Introduction
10.2.2 Image Evaluation
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