Lumbar Spinal Stenosis

Definition/Description

Lumbar spinal stenosis is a common source of leg and back pain. It refers to a narrowing in the vertebra, in the areas of the central canal, lateral recess or the neural foramen.  When Lateral recess and neural foramen are stenosed, symptoms of lumbar radiculopathy may also be demonstrated. Despite its prevalence, currently, there is no universally accepted definition of lumbar spinal stenosis, and there is also a lack of generally accepted radiologic diagnostic criteria.

Lumbar spinal stenosis is a significant cause of disability in the elderly, and it is the most significant cause of spinal surgery in patients over 65 years of age.[1]

[2]

Clinically Relevant Anatomy 

SPINE ANATOMY.jpg

In spinal stenosis the spinal canal becomes comprimised.

The spinal canal is the cavity within the vertebral column which contains the spinal cord with its associated nerve roots and vessels.

The spinal canal becomes progressively narrower from its superior opening at the foramen magnum to its inferior opening at the sacral hiatus. The canal itself is primarily formed by the vertebral foramen of adjacent vertebrae. Allowing for variation, the spinal cord occupies the superior two-thirds of the spinal canal and terminates at approximately the middle of the L1 vertebral body .

Boundaries
  • anterior: vertebral bodies, intervertebral discs, posterior longitudinal ligament
  • posterior: ligamentum flavum lining the laminae
  • lateral: vertebral pedicles [3]

Epidemiology


Spinal stenosis is one of the most common causes of nontraumatic spinal cord injuries[4] in people older than 50 years.[5] Because of the aging of the population, incidence rates of acquired (or degenerative) spinal stenosis have been increasing. This kind of stenosis is due to the degenerative changes  (ligamentum flavum, discus intervertebrales and facet joints) related to aging and occurs at the age of 50 and beyond[6].

There are several types of spinal stenosis. Lumbar spinal stenosis and cervical spinal stenosis are the most common types and occur separately or combined. The thoracic spine is rarely involved. Epidemiological data suggests an incidence of 1 case per 100 000 for cervical spine stenosis and 5 cases per 100 000 for lumbar spine stenosis [7]. The incidence of both types increases during the aging process[8][9][10][11][12]

Etiology

Causes include

  • Degenerative spondylosis. With aging, wear-and-tear changes and traumas, amongst other factors, the intervertebral discs can degenerate and protrude posteriorly, causing increased loading of the posterior elements of the vertebrae. This can lead to posterior vertebral osteophyte formation (uncinate spurs), facet hypertrophy, synovial facet cysts, and ligamentum flavum hypertrophy, which in turn will cause spinal stenosis.
  • Degenerative spondylolisthesis. When degenerative changes of the spine occur, the pars interarticularis can be fractured, and the resulting instability can lead to forward translation of the vertebra.  Sufficient anterior slippage of one vertebra on top of the next vertebral segment (most commonly L4-on-L5) can narrow the spinal canal, leading to stenosis.
  • Other acquired conditions, although rarer than the aforementioned conditions, include space-occupying lesions, post-surgical fibrosis, and rheumatologic conditions as well as other skeletal diseases such as ankylosing spondylitis or diffuse idiopathic skeletal hyperostosis or be secondary to congenital causes such as achondroplasia, which can lead to short pedicles with medially placed facets.[1]

Characteristics/Clinical Presentation

  • Classically, lumbar spinal stenosis presents as pain exacerbated by prolonged ambulation, standing, and with lumbar extension, and is relieved by forward flexion and rest. Neurogenic claudication is an important feature of lumbar spinal stenosis.
  • Symptoms are typically bilateral, but usually asymmetric.
  • Low back pain, numbness, and tingling are present in a majority of patients.
  • Numbness and tingling in lumbar spinal stenosis involve usually the entire leg, and rarely involves only a single nerve root distribution. 
  • Approximately 43 percent of the patients experience weakness.
  • Patients may also report walking upstairs being easier than walking downstairs, as the back is forward flexed with stairs climbing.
  • If patients present with new-onset bowel or bladder dysfunction, saddle anesthesia, bilateral lower extremity weakness and/ or increased lower extremity, the patient may have developed cauda equina or conus medullaris syndromes

Narrowing can occur at different sites. Anatomic/radiographic classification can be applied differentiating between:[13][6][14]:     
- Central stenosis: narrowing of the spinal canal
- Lateral recess stenosis: narrowing of the lateral recess (area underneath the facet joints)
- Foraminal stenosis: narrowing of the intervertebral foramen

One single or combination of anatomic variation(s) can occur[14].

  • In most cases stenosis occurs at the level of facet joints. At this level pathological changes in the disk and facets and hypertrophy of the ligamentum flavum cause the greatest amount of narrowing. At the level of the pedicles, stenosis is rather uncommon and indicates an underlying congenital of developmental stenosis of the bony canal[6].
  • Central stenosis can be caused by degeneration of the vertebral disc. This can lead to narrowing of the spinal canal around the cauda equina[15][16] . Symptoms usually involve buttocks and posterior thighs in a non-dermatomal distribution[17].
  • Lateral recess stenosis can be related to the lateral recess[15][16]. Symptoms are usually dermatomal because specific nerves are compressed. Patients may have more pain during rest and at night, but have more walking tolerance than patients with central stenosis[17].
  • Foraminal stenosis is related to a narrowing of the spinal foramina [16]. It can be the result of a reduced height of the intervertebral space. Foraminal stenosis is also related to age-related degenerative disease of the lumbar discs and/or lumbar facet joints. This increases bone deposition (i.e. osteophytes) due to abnormal redistribution of load bearing in the lumbar spine. Thickening of the joint capsule, osteoarthritis of the facet joints and cyst formation can also narrow the spinal canal or IV foramen[18].
  • Lateral and Foraminal Stenosis can lead to compression of the nerve roots leaving the spinal canal. The L4-L5 segment is most frequently affected by LSS[a], followed by L3-L4[a], L5-S1 and L1-L2[19]. Spinal stenosis can cause compression of the nerve roots of blood vessels, which can be related to the painful symptoms of spinal stenosis[20].

Differential Diagnosis

During the differential diagnosis, red-flag symptoms must be assessed. If such symptoms are present, further diagnostic workup is immediately warranted.

The differential diagnosis of spinal stenosis is broad and differentiation between several conditions may be complicated because of their frequent coexistence, certainly in the elderly. Include, but not limited to:

peripheral vascular disease (vascular claudication), cauda equina syndrome, nonspecific low back pain, degenerative disc disease, spondylosis, malignancy, infection, radiculopathy, distal polyneuropathy, osteoarthritis, inflammatory arthritis, spinal cord vascular malformations, and tethered cord syndrome.

Diagnostic Procedures

Diagnosis is made by a doctor based on patient history and physical examination. In addition, medical imaging can be performed to confirm the diagnosis.

X-rays are useful in searching for fractures due to trauma. It is also helpful in the evaluation of the alignment, loss of disc height and osteophyte formation. With oblique views a defect of the pars interarticaluris is detectable while instability is detectable with dynamic views. Instability is confirmed when the view shows a translation of more than 5 mm or a rotation of more than 10-15 degrees. Reversal of the normal trapezoidal disc geometry with widening posteriorly and a narrowing anteriorly can also indicate instability. The diagnosis of spinal stenosis can be made when bony narrowing, obliteration of epidural fat and deformities of the spine is detected on the X-ray[17].  

MRI (Magnetic Resonance Imaging) is used most frequently and gives the best results [21].

MRI is very sensitive to degeneration and is used for the evaluation of lateral recess stenosis. Sagittal T2-images focus on the foramen vertebrale and are used to diagnose central stenosis. A lack of fat around the root indicates foraminal stenosis. Axial T1-images are used to search for extraforaminal stenosis by showing an obliteration of the normal interval of fat between the disc and the nerve root. MRI findings should always be matched to the symptoms and signs of patients with neurogenic claudication of radiculopathy[17].

In many cases MRI replaces CT-scans[17].

Degenerative changes of the spine are visible on MRI and increase with age. These degenerative changes appear in nearly 100% of people over the age of 60. 21% of people over the age of 60 are diagnosed with spinal stenosis. The sensitivity of MRI is 87-96% and its specificity is 68-75%. Preferably an MRI is taken with the patient in upright position. This enables the visualization of the patho-anatomical changes which occur during axial loading [22].

CAT-scan (Computerized Axial Tomography)[22]

A myelogram, which requires an injection of liquid dye into the spinal canal, is useful when followed by a CT-scan. The combination of both displays a good image of the center lateral canal and defines any extradural cause of compression. This diagnostic procedure is preferred in case of dynamic stenosis, when there are contraindications for MRI or in the absence of suitable findings on MRI. Direct measurements of the bony canal on CT-scans should be interpreted with caution, because they often give an inaccurate assessment of the degree of stenosis[17].

Bone scan (shows where bone is breaking down or being formed)[23].

Outcome Measures 

Lumbar spinal stenosis is related to neurogenic claudication, which is a leading cause of pain and disability. Therefore, specific questionnaires can be used for the assessment of a patient with lumbar spinal stenosis (LSS)[24][25].

The Swiss Spinal Stenosis Questionnaire also known as The Zurich Claudication Questionnaire (ZCQ) consists of three subscales that measure symptom intensity, satisfaction with treatment and physical function. The physical function scale is used primarily to evaluate walking capacity, which is reduced in patients with lumbar spinal stenosis[20][26][27][28]. This questionnaire is a valid and reliable instrument for assessing patients with lumbar spinal stenosis[20][25][28].

The Oswestry Disability Index for assessing self-reported levels of disability and The Maine-Seattle Back Questionnaire (a modification of the Roland-Morris Disability Questionnaire) are commonly used for patients with LSS. They are also valid and reliable instruments for that population.[25][29][28].

Other frequently used questionnaires to determine the progression of symptoms, such as pain and other outcomes, such as level of satisfaction or disability are the Numeric Pain Rating Scale, the Patient Specific Functional Scale, the Oxford Spinal Stenosis Score and the Short Form 36 health survey (SF-36).[20][25][28][30][31].

Examination

Possible symptoms that occur during the examination are neurogenic claudication, which includes pain in the buttocks, thigh or leg during ambulation that improves during rest, or radicular leg symptoms with associated neurological deficits. These symptoms have to present themselves for at least 12 weeks. An older person with suspicion of spinal stenosis usually stoops forward while walking. Other possible symptoms should always be considered during the examination. Pedal pulses, pain on hip rotation and other tests should be performed depending on which symptoms occur and a full neurological examination should be done[32][23].


Following tests should be conducted: 

Bicycle Stress Test
During this test the patient first pedals on a cycle ergometer in upright position with preservation of neutral lumbar lordosis. The distance the patient has pedaled in a certain amount of time is recorded. The patient has to pedal a second time in a slumped position with lumbar delordosing. The distance the patient has pedaled in the same time is recorded again. If the patient can pedal further in slumped position than in upright position, lumbar spinal stenosis is indicated[23][32]

Upright posture with lumbar lordosis
Slumped posture with decreased lumbar lordosis

Upright posture with lumbar lordosis                                                        Slumped posture with decreased lumbar lordosis

Two-Stage Treadmill Test
This test is evaluated on a treadmill. When the patient walks on the flat (0°) treadmill their back is in an extended position. The walking distance in a certain amount of time is recorded. The patient walks on the treadmill a second time with an uphill slope, which means they walk in a flexed position. The walking distance in the same amount of time is recorded again. If the patient walks further on an uphill slope than on the flat treadmill, lumbar spinal stenosis is indicated[23][32].

Upright posture with no incline
Flexed posture with incline

 Flat treadmill                                                                                           Uphill slope

Exercise stress testing on a treadmillThe study of Deen et al [33] determined that this test procedure is a save and easy way to asses baseline functional status and surgical outcome in patients with neurogenic claudication due to lumbar spinal stenosis. By comparing pre- and postoperative results they concluded that this test procedure provides objective outcomes. Thus, this study claims that surgery is beneficial in most cases and is helpful in guiding subsequent management of patients with residual symptoms. The latter is interesting for the physical examination in patients with spinal stenosis.
The test is performed on a treadmill at 0° ramp incline. There are two trials conducted for 15 minutes. The first time the patient should walk at a speed of 1,2 miles per hour and the second time the patient can walk at a pace of their own choosing. Between those two efforts there is a brief rest permitted to allow symptoms to return to baseline level.
The researchers have created a division in degrees on the basis of the occurrence of symptoms and their severity:
- Grade 1 = patients who were able to walk symptom-free
- Grade 2 = patients who were able to complete the test with some neurologic symptoms
- Grade 3 = patients who were able to walk 5 – 15 minutes
- Grade 4 = patients who were able to walk less than 5 minutes

Medical Management

Many therapeutic modalities could be used in the management of spinal stenosis. Treatment plans must be individualized based on each specific patient's presentation. Spinal stenosis rarely leads to progressive neurological injury. Therefor non-operative modalities should be attempted first.

Management for lumbar spinal stenosis is aimed at reducing symptoms and improving functional status. 

Conservative treatment is the first-line treatment for this condition. 

Conservative treatment options include physical therapy, oral anti-inflammatory medications, and epidural steroid injections. Although there is no standardized physical therapy regimen, many therapists focus on stretching and strengthening of the core muscles, which can lead to correction of posture and improved symptom.

Although there are short-term benefits, lumbar epidural steroid injections have not been shown to have long-term improvement of pain and disability in lumbar spinal stenosis patients, and there is no statistical difference between epidural injections with anesthetics alone versus a mixture of anesthetics with corticosteroids.

Lumbar corsets may also be trialed for temporary relief of pain[1]

Surgery

Barring emergencies such as cauda equina syndrome, surgical management for lumbar spinal stenosis is usually elective, as the goal of treatment is to improve function, rather than preventing neurologic impairment.

The most frequently performed surgical procedure is laminectomy. A randomized trial has shown that there is a greater improvement of symptoms in patients undergoing laminectomy compared to the non-surgical group, however, the symptom improvement between the surgical and non-surgical groups diminish over time. 

Laminectomy with fusion is typically reserved for patients with concurrent spondylolisthesis to provide further stability.

A less invasive approach is interspinous spacer implantation, this procedure is appropriate for patients with intermittent claudication symptoms without spondylolisthesis.[1]

Physical Therapy Management

Lee et al.[17] found that patients with moderate pain undergoing a conservative treatment will have 50% pain relief in less than 3 months. In total 60–90% of all patients experience symptom relief after surgical or conservative treatment.

Physical therapy is associated with reduced likelihood of patients receiving surgery within 1 year. Only symptomatic patients should be treated[34].

There are no significant differences between conservative treatment and surgery for pain up to 2-year follow-up. From then on the results of the study favour surgery over physical therapy for pain and disability[27]. Malmivaara et al favour surgery over physical therapy for all time points. Weinstein et al gave no differences between groups[27].

The study of Atlas et al.[34] concluded that at the end of the follow up period there is no difference in pain and overall satisfaction between patients who were treated with physical therapy or with surgery. Radicular symptoms did improve less after physical therapy. 

Low Back Stretch.png

Conservative treatment and especially physical therapy includes a combination of different interventions: 

  • Flexion-based exercise programs [27][34]
     -Lumbar flexion exercises are done to reduce the lumbar lordosis. This is the most comfortable position for the patient because the symptoms reduce in combination with a decrease of the epidural pressure in the lumbar spinal canal.
     -Single and double leg knees to chest in supine position. This position should be held maintained for 30 seconds. In the single leg exercise the patient should alternate the legs. Double knee is a progressive exercise.
     -This exercise program should have a stepwise logistic regression during the first 6 weeks.
     -Treadmill walking is the final step in this program.
  • Manual therapy[27]
  • Lumbar isometric and stretching exercises[27]
  • Static and dynamic postural exercises [27]
  • Individualized muscle strengthening [27]
  • In the over 70 age bracket a graded rehabilitation approach focusing on improving ambulation showed significant pain reduction[35]. See the reference for comprehensive outline of rehabilitation exercises.
  • Endurance exercises [27]
  • Stabilization of abdominal and back muscles to avoid excessive lumbar extension [27]
  • Postural and ergonomic advice 
  • Falls prevention intervention in seniors with LSS. Seniors with chronic low back pain have a significantly higher risk of falls[36]
  • Aerobic fitness [17]
  • Cycling exercises[27]
  • Home exercises[34]
  • Education (Back school) and counselling [27][34]
  • An aquatic walking and jogging program has a beneficial effect on muscle function tests, the BERG balance scale and the fall efficacy scale. The ankle range of motion also increased. This program still has to be investigated[37].
  • Corsets may help to maintain a posture of slight lumbar flexion to avoid atrophy of paraspinal muscles but it should be worn only for a limited number of hours per day. It also promotes back extension. A lumbar corset is significantly better than no corset for pain and walking capacities[27].
The youtube below shows some good exercises to use in treating clients with LSS.
[38]

Whitman et al. [39] found that a program of spine manipulation, the pelvis and lower extremities, muscle strengthening exercises and body-weight supported treadmill walking had superior outcomes compared to a program that included lumbar flexion exercises, non-thermal ultrasound to the lumbar area, and a treadmill walking program in treating patients with spinal stenosis. The study also concludes that additional improvements in disability, satisfaction and treadmill walking tests can be realized by the inclusion of manual physical therapy interventions, exercise and a progressive body weight supported treadmill walking program[39]. They also found that manual therapy in addition to flexion exercises and walking had similar effects to those of flexion exercises and walking alone[39].

The study of Pua et al.[27]showed that body-weight supported treatment was not significantly better than cycling for short term pain and disability.

Koc et al.[40]found that the addition of modalities (eg.ultrasound, TENS) to the conservative treatment are effective in reducing pain and improving function in patients with LSS. Goren et al. [27] found that an exercise program plus modalities was significantly better than no exercise in short term for back pain, leg pain and disability.

Fritz et al. [34] says that if the recommended initial management strategies are not effective, aggressive conservative interventions should be pursued. This study also confirms that patients who take physical therapy treatment in the first six weeks are less likely to undergo surgery at one year follow up. They found higher levels of patient, who had physical therapy during 6 weeks, self-rated major improvements at 3 – 6 months and 1 year. They also had a greater reduction in leg pain after 1 year[34].

Clinical Bottom Line

Lumbar spinal stenosis is a common disease process. These patients have symptoms such as leg pain and low back pain. The cause of this condition is most likely secondary to chronic wear-and-tear damages to the vertebral column.

Because there is no evidence to demonstrate the superiority of surgical versus non-surgical treatments of lumbar spinal stenosis, it is important to take a interprofessional team-based cooperative model.

Primary physicians must recognize the patient's presentation, the care of the patient must be coordinated with pain management, orthopedist, and/ or neurosurgeons (if there is a neurosurgical emergency) and physical therapists.

Physical therapy is the mainstay in the conservative treatment of this condition. 

References

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