The characteristic symptom of lumbar spinal stenosis (LSS) is neurogenic claudication (spinal claudication). When walking, the patient experiences pain (which usually starts in the back and radiates to the legs), numbness and/or weakness.
If the symptoms are tolerable and the patient's functional capacity is intact, the first-line management option is conservative treatment (including e.g. analgesia and physiotherapy).
Consider surgery, if needed, after 3-6 months of conservative treatment.
Indications for surgery include
unbearable or clearly interfering pain not relieved with conservative treatment
gradually shortening walking distance
progressing neurological deficit - LSS may be behind paraparesis
cauda equina syndrome (a rare situation: LSS usually progresses slowly).
In rapidly progressive strength weakness, paraparesis, intolerable treatment-resistant pain or cauda equina situation, make an emergency referral; if the situation is unclear, consider a telephone consultation with an orthopaedist.
Definition and epidemiology
Lumbar spinal stenosis denotes a stricture (stenosis) in the lumbar spine region, which may be either
a central stenosis (compression of the cauda equina in the spinal canal) or
a lateral stenosis (nerve root compression in the root canal or intervertebral foramen).
Degenerative changes are the most common cause of stenosis (ostephyte formation or ligament hypertrophy). Disc protrusion or prolapse may also be present.
Division into central and lateral forms is a radiological differentiation; mixed form LSS is the most common type.
Prevalence and incidence increase with age. The prevalence of LSS in adults is at least 11%, and LSS causes symptoms in more than 100 million people worldwide 5359.
LSS is the most common reason for spinal surgery.
The prevalence of LSS is increasing because MRI and CT scans are carried out more than before and the population is ageing.
Symptoms and history
The most common symptom is neurogenic (spinal) claudication; when walking, the patient experiences pain (which usually starts in the back and radiates to the legs), numbness and/or weakness. The pain is usually relieved by sitting or leaning forward and worsened by extension.
Pain which is caused by chronic compression of a nerve root (”chronic sciatica”) is more persistent or manifests itself as numbness and paraesthesia; the symptoms may be localised to the affected dermatome or be more widespread.
The symptoms of LSS may be unilateral or bilateral. The intensity of pain often shows variation both from day to day and over the long term.
Patients may describe the symptoms in very different ways, and it is important to ask carefully about the location and nature of symptoms experienced during walking, exercise or at rest.
What distance can the patient walk on level ground without stopping? Does he/she stop due to referred pain or for another reason?
Leaning forward for a prolonged period, exercise and even sitting may worsen the symptoms of LSS, particularly back pain. As is the case with all degenerative low back problems, reduced exercise tolerance of the back should be identified by taking a careful history, particularly when the symptoms threaten the patient's work capacity, since a physical examination of a patient with LSS may produce only a few findings.
Remember cauda equina symptoms and other critical "red flag" symptoms Low Back Pain.
Clinical findings
Patients with LSS-induced neurogenic claudication may be relatively asymptomatic when examined at rest, and findings of neurological examination may be completely normal. The importance of the history is thus emphasized.
If LSS is characterised with chronic nerve root compression, the patient may have pain when moving his/her back, and the SLR (straight leg raising) and Lasègue tests may be positive.
In the SLR test, the examiner raises the patient's straightened leg upwards by supporting it at the underside of the ankle so that the ankle remains free. In the Lasègue test the examiner has a hold on the patient's foot and keeps the ankle dorsiflexed in straight angle (90°) while raising the leg. In both tests, the examiner's other hand lies on the anterior surface of the patient's thigh to keep the knee straight.
Extension test: the patient is asked to fully extend his/her back whilst standing with the knees straight. The posture is held for 30-60 seconds. Low back pain/numbness provoked by the posture supports the diagnosis of LSS. The specificity of the test is not known.
Approximately half of the patients with LSS have sensory or reflex defects.
The pulses of the dorsal pedis artery and the posterior tibial artery should be palpated. A significant vascular occlusion may be excluded if the pulses are present, which will strengthen the suspicion of back problems as the cause of claudication.
Consider performing digital rectal examination (cauda equina compression; carcinoma of the prostate as the cause of back pain).
Workup
Plain X-ray examination of the spine is not necessary before MRI and does not provide sufficient information for the diagnosis of LSS.
Generally, a specialist makes the decision to perform an MRI (to optimize the correct targeting of the imaging, interpretation of the report and further treatment).
The MRI referral should include the laterality of the symptoms and the presumed level(s) of the entrapment in the lumbar spine.
In the SPORT study 42, stenosis occurred at the lumbar vertebral levels as follows: 28% L2-3, 66% L3-4, 92% L4-5 and 26% L5-S1.
The findings on MRI in the supine position with the knees slightly bent may be milder than in the actual situation in the upright position, especially in the case of disc protrusions 5860.
Differential diagnosis
Back pain; differential diagnosis as for normal back pain Low Back Pain
Lower limb symptoms; differential diagnosis should take into account the possibility of local aetiology and other factors
Pain usually in the calf and relieved by resting (flexing forward does not relieve pain); bicycling triggers claudication. Often abnormalities in pulse palpation.
Disc prolapse in the lumbar spine
Often a symptom that has appeared fairly rapidly in a younger patient. A positive nerve stretch test (Lasègue, femoral stretch test) is suggestive of a prolapse but does not exclude LSS.
Muscle trigger points at the lumbar spine/buttock/lower limb areas may cause local pain. Occasionally they will only cause non-specific reflex abnormalities (absent).
The trigger point may be anaesthetised as a diagnostic and therapeutic test.
Treatment
The outcome of patients with LSS is moderately good without surgery, and conservative treatment should therefore always be tried at first. ”Watchful waiting” may be sufficient for some patients 5363.
Surgical treatment of peroneal paresis due to lumbar degenerative disease (stenosis and disc protrusion) is recommended within one month of the onset of symptoms 55.
Decompressive surgery and, if needed, fusion is more effective in symptomatic patients if 3 to 6 months of conservative treatment has failed.
The better results (pain, functional ability) achieved with surgical treatment in symptomatic LSS patients may last for up to 4 years. The benefit is reduced during 8 to 10 years of follow-up.
Conservative treatment
Indications for conservative treatment
The patient is able to tolerate the symptoms and daily functional capacity is adequate.
The patient does not want to be operated; assessment of surgery-related risks takes place usually within specialized care.
Encouragement to normal daily activities; appropriate aerobic exercise (e.g. "Nordic walking" with special walking poles similar to ski poles, cycling 49, swimming or other pool exercise avoiding hyperextension of the back)
Reduction of significant overweight and cessation of smoking
At work: positions that alleviate pain, ergonomics, recovery pauses, rotation of work tasks
A lumbar corset may increase walking distance by over 30% and alleviate symptoms during strain.
Physiotherapy
Physiotherapy may reduce the need for surgical treatment within one-year follow-up.
Physiotherapeutic guidance twice a week for 6 weeks (manual therapy, stretches, exercises, cycling, walking mat) relieves symptoms better than home exercises alone 6162.
Individually tailored easing of the pain and tightness of the myofascial tissues in the lower back and gluteal and thigh area, muscle activation exercises, self-care training programme
An accentuated lumbar lordosis (saddle back) can increase stenosis changes in the same way as a lower back retroflexion. A brace, hip flexor stretching and especially abdominal and posterior thigh muscle exercises can be tried to recude the lordosis. Abdominal obesity can cause lordosis to become more accentuated, in which case weight loss will help the symptoms.
Ultrasound and TNS therapies are not effective 54.
Analgesic medication
Analgesics (paracetamol, NSAIDs, mild opioids if necessary); dosage according to the intensity and appearance of symptoms, taking into account other medication and diseases
Nerve pain medications, especially gabapentin 300-2 400 mg/day 50 and also pregabalin, can relieve pain symptoms when combined with conventional analgesic medication, exercise and corset treatment. Duloxetine relieves chronic low back pain 6451.
Long-term use of opioids may be considered in refractory pain (whilst monitoring the response) after the diagnosis is verified if, for example, the patient will not benefit from surgery.
Strong opioids for long-term use should be initiated in specialist care (a physiatrist, a surgeon, a doctor at a pain clinic).
The treatment should be monitored according to local protocols.
Epidural anaesthetic blocks may provide short-term relief of pain and improvement of functional ability, but they have been associated with a risk of worse prognosis (pain, functional ability) in 4-year follow-up.
Check local guidance on medical statement requirements for working-age individuals with LSS.
Surgical treatment
Surgical treatment for LSS has been shown to be effective and cost-effective in 2-year and 4-year follow-up as compared to conservative treatment 42. Surgical treatment should be considered after 3 to 6 months of conservative treatment that has failed, unless the symptoms give reason to do so earlier 524148. Results of surgery (functional capacity, symptoms, satisfaction with surgery) become poorer if the preoperative symptoms that require surgery become prolonged 56.
Preoperative use of analgesic drugs for more than 12 months is predictive of worse functional result in LSS patients who undergo surgery. Delaying the operation is hence not recommended, if the symptoms are severe and clinical-radiological indication exists.
Surgery is considered on the basis of radiologically confirmed stenosis compatible with the patient history and/or clinical findings.
Indications for surgery in LSS are considered to be
clearly disturbing or intolerable pain or significant functional impairment that are not relieved with conservative management
gradually shortening continuous walking distance (< 200-300 m).
The walking distance should, however, be set in proportion to other symptoms, diseases and the age of the patient. In a younger patient, a milder symptom may be relatively more impairing, and surgical treatment may occasionally be used even if the patient were able to walk over a kilometre.
About two out of three patients treated surgically are reported to have good to excellent outcomes. Cessation of smoking improves recovery from surgery. Attention should be pain on treatment of depressive symptoms both pre- and postoperatively because they are predictive of worse recovery. In LSS, preoperative factors predicting a better postoperative outcome include
pronounced constriction of the spinal canal
better walking ability and general health as assessed by the patient.
Factors predicting a worse postoperative outcome or complication risk include
preoperative lumbar scoliosis
cardiovascular diseases
overweight (increases the risk of infection in the operative site)
concomitant disease affecting walking ability (e.g. in concomitant hip osteoarthritis one should evaluate as to what extent the symptoms are caused by LSS and whether the patient will benefit from back operation).
Diabetes is associated with a risk of postoperative complications during and after hospitalization but not with an increased risk of wound infection 56.
A history of previous back operation as well as age over 75 years predict lower satisfaction with the operation, but the functional result in these patients is comparable to others 47.
Simply being older (over 80) does not increase the risk of complications.
It is not possible, however, to conclude from the predictive factors who warrants surgery.
Active postoperative rehabilitation on an outpatient basis may improve the functional treatment results, as well as pain in the back and lower extremities.
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