Residency · Residency · Chronic Pain Management

Lumbar Spinal Stenosis: Conservative and Interventional Management

Introduction

Lumbar spinal stenosis (LSS) is the most common indication for spine surgery in patients over age 65, with a prevalence of 19-47% in the aging population based on imaging criteria. It is defined as narrowing of the central spinal canal, lateral recess, or neural foramen resulting in compression of neural elements. The hallmark clinical syndrome is neurogenic claudication — bilateral lower extremity pain, heaviness, and paresthesias that are exacerbated by standing and walking and relieved by sitting or lumbar flexion.

Pathophysiology and Classification

Types of Stenosis

Central canal stenosis results from narrowing of the central spinal canal, typically caused by disc bulging, ligamentum flavum hypertrophy, and facet joint enlargement. Lateral recess stenosis compresses the traversing nerve root within the lateral recess, which is bounded by the pedicle, superior articular process, and disc. Foraminal stenosis narrows the neural foramen and compresses the exiting nerve root, often from disc height loss and facet hypertrophy. Degenerative spondylolisthesis — forward slippage of one vertebra, most commonly L4 on L5 — frequently accompanies central stenosis.

Neurogenic Claudication vs. Vascular Claudication

Distinguishing neurogenic from vascular claudication is a fundamental clinical skill. Neurogenic claudication is exacerbated by extension (standing, walking downhill) and relieved by flexion (sitting, leaning on a shopping cart — the "shopping cart sign"). Walking distance is variable, and peripheral pulses are normal. Vascular claudication is exacerbated by exertion regardless of posture, relieved by rest in any position, produces a reproducible walking distance, and is associated with diminished pulses and an abnormal ankle-brachial index.

<image>Side-by-side medical illustration comparing a normal lumbar spinal canal cross-section at L4-L5 with a stenotic canal, demonstrating ligamentum flavum hypertrophy, facet joint enlargement, disc bulging, and resultant thecal sac compression with crowding of the cauda equina nerve roots, all structures clearly labeled</image>

Imaging Findings

MRI is the gold standard for diagnosis. Key findings include cross-sectional area of the dural sac less than 100 mm2 (moderate stenosis) or less than 75 mm2 (severe stenosis), ligamentum flavum thickness greater than 4 mm, facet hypertrophy, and the disc-thecal sac relationship. CT myelography is an alternative when MRI is contraindicated and offers excellent bony detail and dynamic assessment. Dynamic flexion-extension radiographs are essential for evaluating spondylolisthesis instability. An important caveat is that imaging severity correlates poorly with clinical symptoms, so treatment decisions must integrate the clinical presentation with the imaging findings.

Physical Therapy

Physical therapy is first-line management and should be initiated early. Flexion-based exercises (Williams flexion exercises) reduce lumbar lordosis and increase canal cross-sectional area and are strongly preferred over extension-based programs, which may worsen symptoms. Cycling and aquatic therapy are well-tolerated aerobic conditioning modalities that maintain lumbar flexion. Core stabilization through transversus abdominis and multifidus strengthening improves dynamic spinal stability. Manual therapy with lumbar distraction techniques and soft tissue mobilization complements the exercise program. Gait training with assistive devices such as a rolling walker facilitates community ambulation in a flexed posture. The SPORT trial observational cohort demonstrated that structured physical therapy produced meaningful improvement in approximately 33% of patients with LSS.

Pharmacotherapy

NSAIDs provide moderate short-term benefit for symptom management. Gabapentinoids — gabapentin at 300-1200 mg three times daily — may improve walking capacity and reduce leg symptoms, though evidence is mixed. Calcitonin, previously studied for neurogenic claudication, is no longer recommended based on updated Cochrane reviews. Opioids should be avoided for chronic management but may be considered for short-term flares.

Epidural Steroid Injections

Epidural steroid injections remain the most commonly performed intervention for LSS, and the three available approaches each offer distinct advantages.

Interlaminar Epidural Steroid Injection

The interlaminar approach uses a midline or paramedian technique with loss-of-resistance under fluoroscopic guidance and contrast confirmation. Its advantages include bilateral spread, technical familiarity, and suitability for central stenosis. Limitations include less target specificity and posterior epidural deposition that may not reach ventral pathology. Evidence supports short-to-intermediate term improvement in pain and walking capacity, though long-term benefit is limited.

Transforaminal Epidural Steroid Injection

The transforaminal approach accesses the epidural space via a subpedicular or retrodiscal (Kambin triangle) route, targeting the affected nerve root under fluoroscopy. Its advantages are target-specific delivery to the ventral epidural space and the affected nerve root, with a lower total steroid dose. It is indicated for lateral recess or foraminal stenosis with radicular symptoms and unilateral dominant symptoms. Digital subtraction angiography is recommended to detect intravascular uptake; particulate steroids are acceptable in the lumbar spine, but vigilance for vascular uptake remains essential.

Caudal Epidural Steroid Injection

The caudal approach places the needle through the sacral hiatus into the caudal epidural space, using a higher volume (10-20 mL) to achieve cephalad spread. It is technically straightforward, avoids needle placement near the conus medullaris, provides bilateral spread, and is useful in patients with prior lumbar surgery or difficult interlaminar access. Limitations include unpredictable cephalad spread, diluted steroid concentration from the higher volume, and lack of target specificity.

<image>Comparative fluoroscopic images in lateral view demonstrating needle placement and contrast spread patterns for three epidural approaches in lumbar spinal stenosis: interlaminar (midline posterior approach with dorsal epidural spread), transforaminal (subpedicular approach with ventral epidural and nerve root sleeve opacification), and caudal (sacral hiatus entry with cephalad epidural flow), with anatomical landmarks labeled</image>

MILD Procedure (Minimally Invasive Lumbar Decompression)

The MILD procedure is indicated for neurogenic claudication due to central stenosis with ligamentum flavum hypertrophy of at least 2.5 mm confirmed on MRI, particularly in patients who are poor surgical candidates or wish to avoid open decompression. The technique involves a percutaneous approach through a 6-gauge cannula under fluoroscopic guidance, using tissue sculpting tools to debulk the hypertrophied ligamentum flavum and small amounts of laminar bone, thereby increasing central canal cross-sectional area. Advantages include minimal invasiveness, performance under local anesthesia with sedation, preservation of spinal stability, and the absence of any implant. The MILD 1-year RCT and 2-year follow-up studies demonstrated statistically significant improvements in the Oswestry Disability Index, Numeric Pain Rating Scale, and Zurich Claudication Questionnaire standing and walking domains compared to epidural steroid injection. The procedure is not appropriate for foraminal stenosis, spondylolisthesis greater than grade 1, or patients who are surgical candidates with severe stenosis. The complication rate is low (less than 1%), with rare dural tear or epidural hematoma.

Vertiflex Interspinous Spacer (Superion)

The Vertiflex interspinous spacer is indicated for moderate lumbar spinal stenosis at one or two levels (L1-L5) in patients with neurogenic claudication who achieve relief with lumbar flexion and who are not surgical candidates or prefer a less invasive option. The device limits extension at the treated segment, maintaining the foramen and central canal in a relatively flexed (open) position — essentially mimicking the postural relief patients naturally experience with forward flexion. Insertion is percutaneous, between adjacent spinous processes under fluoroscopic guidance, and is performed as an outpatient procedure. The FDA IDE trial demonstrated non-inferiority to surgical decompression at two years for clinical success based on the Zurich Claudication Questionnaire composite score, with five-year data supporting durability of outcomes. Contraindications include spondylolisthesis greater than grade 1, spinous process fracture, osteoporosis with high fracture risk, and prior laminectomy at the target level. Complications include spinous process fracture (5-10%), device migration, and recurrent stenosis requiring surgical decompression.

<image>Medical illustration showing a sagittal cross-section of the lumbar spine with a Vertiflex interspinous spacer deployed between the L4 and L5 spinous processes, demonstrating how the device limits extension and opens the spinal canal and neural foramina, with before-and-after comparison of canal diameter and labeled anatomical structures</image>

Clinical Pearls

The "shopping cart sign" is highly suggestive of neurogenic claudication — patients instinctively lean forward to relieve symptoms while walking. Neurogenic claudication must always be distinguished from vascular claudication; ankle-brachial index testing is a simple screening tool. Imaging severity does not reliably predict symptom severity, and cross-sectional area measurements should be interpreted in clinical context. The MILD procedure and Vertiflex spacer occupy a treatment niche between failed conservative therapy and open surgical decompression, but patient selection is critical. Flexion-based physical therapy is the cornerstone of conservative management, and extension-based programs may actually worsen symptoms. Shared decision-making is essential: the SPORT trial showed that both surgical and conservative management can produce meaningful improvement, with surgery offering more rapid symptom relief.

References

1. Kreiner DS, Shaffer WO, Baisden JL, et al. An evidence-based clinical guideline for the diagnosis and treatment of degenerative lumbar spinal stenosis (update). Spine J. 2013;13(7):734-743.
2. Weinstein JN, Tosteson TD, Lurie JD, et al. Surgical versus nonsurgical therapy for lumbar spinal stenosis. N Engl J Med. 2008;358(8):794-810.
3. Benyamin RM, Staats PS, MiDAS ENCORE Investigators. MILD is an effective treatment for lumbar spinal stenosis with neurogenic claudication: MiDAS ENCORE randomized controlled trial. Pain Physician. 2016;19(4):229-242.
4. Patel VV, Whang PG, Haley TR, et al. Superion interspinous process spacer for intermittent neurogenic claudication secondary to moderate lumbar spinal stenosis: two-year results from a randomized controlled FDA-IDE pivotal trial. Spine. 2015;40(5):275-282.

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