Lumbar spinal stenosis is a condition being recognized with increasing frequency as the population continues to age. It is defined as narrowing of the spinal canal, nerve root canal (lateral recess), or intervertebral foramina of the lumbar spine. 2 It is the most common diagnosis associated with lumbar spine surgery in patients older than 65 years. 31 In the United States alone, approximately one in 1000 individuals older than 65 years has a laminectomy for lumbar spinal stenosis, with estimated costs of approximately $1 billion. 10 Although surgical rates have increased rapidly as a result of numerous factors including improved diagnostic imaging, improved surgical techniques, and the aging of the population, the natural history of lumbar spinal stenosis is not necessarily one of progressive deterioration. 13,14,26 Conservative treatment is advocated in patients with mild to moderate symptoms of lumbar spinal stenosis, 5,13,14,21, 26,35 and may include therapeutic exercise. A program of therapeutic exercise must be based on an understanding of the pathoanatomic changes in patients with lumbar spinal stenosis, and must be tailored to each patient based on his of her clinical history and physical examination findings.
Anatomically, lumbar spinal stenosis can be classified as central or lateral. 2 Central stenosis involves narrowing of the spinal canal around the thecal sac containing the cauda equina, and occurs as a result of facet joint arthrosis and hypertrophy, thickening and bulging of the ligamentum flavum, bulging of the intervertebral disc, or spondylolisthesis. Lateral stenosis causes encroachment of the spinal nerve in the lateral recess of the spinal canal or in the intervertebral foramen, and results from facet joint hypertrophy, loss of disc height, intervertebral disc bulging, or spondylolisthesis. 2
In addition to being classified by the site of the anatomic narrowing, lumbar spinal stenosis can be classified based on the etiology. 32 Developmental or primary stenosis is caused by congenital malformations or defects in postnatal development, and is rare. The majority of lumbar spinal stenosis is considered acquired or secondary, and results from degenerative changes, spondylolisthesis, postsurgical scarring, intervertebral disc herniation, or from combinations of these conditions. 2 Other much less frequent causes of secondary stenosis include fractures, tumors, infection, or systemic diseases such as Paget’s disease. 32 Combinations of degenerative (secondary) stenosis and congenital (primary) stenosis have been classified as mixed.
Pathoanatomy and Pathophysiology
An understanding of the pathoanatomic and pathophysiologic factors that contribute to causing symptoms in patients with lumbar spinal stenosis is essential for understanding which types of therapeutic exercises are prescribed to help manage those symptoms. Anatomically, the pathology of lumbar spinal stenosis has a dynamic and a structural component. 12 Extension of the lumbar spine causes posterior protrusion of the intervertebral disc and bulging of the ligamentum flavum, resulting in additional narrowing of the central and lateral canals. Sortland et al 29 reported that in healthy subjects, the decrease in dural anteroposterior diameter during spinal extension was 9%; in patients with severe stenosis this decrease was 67%. Dai et al 6 reported that the capacity of the dural sac was significantly greater in flexion than in extension. Penning 23 refers to the “rule of progressive narrowing”, in which greater structural narrowing of the lumbar spine results in greater relative narrowing during spinal extension. Spinal extension also has been reported to cause a 20% reduction in the cross-sectional area of the intervertebral foramina in normal and degenerative spinal segments. 22 Axial loading has been reported to reduce the cross-sectional area of the spinal canal significantly. 27
The precise pathophysiologic effects that result from the above anatomic changes and lead to patient symptoms are unclear. Some authors have proposed a primarily vascular cause, 25 whereas others have emphasized direct mechanical compression as the process underlying the development of symptoms in lumbar spinal stenosis. 11,30
Not all patients with documented lumbar stenosis are symptomatic. 4,34 Even when symptoms develop, there may not be an association between the severity of pain and the degree of stenosis found. 1,19 Patients with lumbar spinal stenosis who are symptomatic often relate a long history of low back pain, which is not unexpected given that degenerative changes are the most common etiology. 16,31 Unilateral or bilateral leg pain is also a predominant symptom, and is reported to occur in approximately 90% of patients with lumbar spinal stenosis. 31 Although most patients report pain distal to the knees, some only may have symptoms in the proximal lower limb. 16 Patients report lower extremity sensory or motor disturbances or balance dysfunction less frequently. Approximately 65% of patients with lumbar spinal stenosis will present with neurogenic claudication (also referred to as pseudoclaudication), defined as poorly localized pain, paresthesias, or cramping of one or both lower extremities which is brought on by walking and relieved by sitting. 16,31 Very rarely, patients with lumbar spinal stenosis present with symptoms of cauda equina syndrome. 16
Although the symptoms of lumbar spinal stenosis clearly are variable, they tend to be consistently posture-dependent. Symptoms typically worsen with lumbar extension or weightbearing, and improve with sitting or standing with lumbar flexion and with lying. 16,23,30 As a result, patients often sit or stand with a stooped posture, are more comfortable when walking uphill rather than downhill, and usually are able to ambulate for greater distances if they are bent forward. 24 To help maintain their lumbar spine in a flexed position, patients often will ambulate with the assistance of a walker or shopping cart. 5,11,20
Clinical Examination Findings
Physical findings in patients with symptomatic lumbar spinal stenosis often are minimal and nonspecific, and do not appear to be particularly helpful in ruling in or ruling out the diagnosis of lumbar spinal stenosis. 8 The most common finding has been reported to be decreased spinal extension. 18 Decreased or absent ankle reflexes may be found in approximately 50% of patients, 31 whereas objective weakness has been reported to vary from 23% to 51% in patients with lumbar spinal stenosis. 1 Sensory deficits have been found to be present in 51% of patients, 1,31 although a positive straight leg raise may be observed in approximately ½ of all patients with lumbar spinal stenosis. 31
In light of the importance of postural and mechanical factors that contribute to causing symptoms in patients with lumbar spinal stenosis, it is surprising that the flexibility of the lower limb muscles are not routinely assessed or mentioned in studies describing typical examination findings in these patients. 1,16,31 Because of their attachments to the pelvis, the hip flexors and extensors have a significant influence on the position of the lumbar spine. Adequate hip muscle flexibility allows for motion at the hip independent of lumbar segmental motion. Reduced flexibility or shortening of the hip flexors (iliopsoas and rectus femorus) leads to excessive anterior tilt of the pelvis, and causes excessive extension of the lumbar spine. In addition, the hip extensor muscles (gluteus maximus and hamstrings) are lengthened and therefore placed at a mechanical disadvantage, which leads to early recruitment of the lumbar extensor muscles and also may lead to excessive lumbar extension. 33 Therefore, lower extremity flexibility testing should be assessed carefully and routinely in all patients with lumbar spinal stenosis. Similarly, spinal range of motion is assessed to differentiate lumbar spine restrictions from those attributable to reduced lower extremity flexibility. The prescription of proper therapeutic exercises should be based on the specific limitations detected during the physical examination.
The flexibility of one-joint and two-joint hip flexor muscles (for example, iliopsoas and rectus femorus, respectively) can be evaluated by performing a Thomas test. One-joint hip flexors are considered to be shortened when the tested hip is unable to extend to a neutral position while the pelvis maintains a posteriorly tilted position. A posterior pelvic tilt is a position of the pelvis in which the vertical plane through the anterosuperior spines is posterior to a vertical plane through the symphysis pubis. Two-joint hip flexor muscles are considered shortened when the knee is unable to reach 80° flexion without increasing hip flexion. 17
Manual muscle testing of the hip extensor muscles in patients with lumbar spinal stenosis is important because of the potential imbalance created by tight hip flexors described above. Gluteal strength is assessed with the patient prone, with 90° knee flexion, and with resistence applied to the posterior thigh as the patient performs hip extension. 17 Assessing the strength of the abdominal muscles also should be performed routinely in patients with lumbar spinal stenosis, because weakened abdominal muscles permit an anterior pelvic tilt and a lordotic posture. 17 Muscle testing of the upper abdominal muscles is performed with the patient supine with his or her legs extended. The patient raises the trunk forward, with the arms extended, folded on chest, or behind the head. The ability of the spine to flex segmentally without substitution of the hip flexors is observed. The oblique abdominal muscles are tested in the same manner; however, the trunk is raised diagonally. Lower abdominals typically are tested with leg lowering with the patient supine while the pelvis is maintained in a posterior tilt 17; however, this may need to be modified in patients with lumbar spinal stenosis because of the strong anterior pull of the hip flexors that encourage lumbar spine extension. A modified test can be done with the patient supine with his or her knees bent, extending one leg at a time while the pelvis is maintained posteriorly tilted.
Therapeutic exercise is one of numerous treatments that have been proposed for the conservative treatment of patients with lumbar spinal stenosis. However, difficulty arises when trying to determine the potential benefit a patient may obtain from therapeutic exercise, or from any form of conservative treatment, because there are presently no randomized controlled studies available in which the outcomes of conservative versus surgical treatment are compared. 31 Conservative treatment of lumbar spinal stenosis may be a valid alternative to surgery and has been advocated in patients with mild to moderate symptoms. 5,13,14,21,26,35 Although many forms of conservative treatment have been reported to be efficacious, 7–9,19–21,28 including nonsteroidal antiinflammatory medications, epidural steroid injections, pelvic traction, and rigid corsets, the potential benefits of therapeutic exercise for patients with lumbar spinal stenosis will be discussed.
Although some authors have proposed therapeutic programs using lumbar flexion and extension exercises, 19 several authors advocate only the use of flexion exercises because of the spinal canal and neuroforaminal narrowing produced by lumbar extension. 7,9,28 General activity and conditioning exercises, and aquatic therapy, 9 also have been advocated in the treatment of patients with lumbar spinal stenosis. Currently there are no randomized controlled studies in which the beneficial effects of therapeutic exercise in patients with lumbar spinal stenosis are evaluated. 8 Until such data exist, it seems reasonable to prescribe a therapeutic exercise program based on the patient’s history and physical examination, and on an understanding of the pathoanatomic changes contributing to the clinical picture.
The therapeutic exercise program should be tailored to each patient to accommodate limitations imposed by other existing medical problems, especially given the high likelihood of comorbidity in this patient population. A prescribed program may need to be modified so that it does not exacerbate any coexisting orthopaedic conditions such as osteoarthritis of the hips or knees, while still being effective. A history of cardiovascular or pulmonary disease may necessitate medical clearance before a therapeutic exercise program is started, and the patients should be monitored closely during the program. Patients who are obese should be counseled about the importance of weight reduction before beginning a therapeutic exercise program. Patients who are obese are at risk for increased symptoms of lumbar spinal stenosis for numerous reasons. Increased abdominal girth leads to increased length of the abdominal muscles, which weakens these muscles by placing them at a mechanical disadvantage, and also makes strengthening difficult. This may lead to an increased lumbar lordosis, which counteracts the intended effect of the therapeutic exercise program. In addition, obesity increases axial loading of the spine, which may lead to an additional reduction in cross-sectional area of the canal. 27
Therapeutic exercise includes stretching, strengthening, conditioning, and postural education (Table 1). The goal of prescribed stretching and strengthening exercises is to decrease the extension forces on the lumbar spine attributable to agonist muscle tightness, antagonist weakness or both, which results in a decreased lumbar lordosis. Conditioning exercises may include walking on a treadmill, on level and inclined surfaces, riding a stationary bicycle, and pool exercises, with the goal of increasing general fitness. Education in proper posture and body mechanics for daily functional activities is essential to maintain the gains made through the therapeutic exercise program. Referral to a physical therapist not only ensures that the patient receives proper instruction and education in the appropriate therapeutic exercise program, but that the patient also is monitored closely and advanced in their program as tolerated.
A general warm-up period and the application of topical heat to the muscle being stretched may facilitate stretching. Low load, long duration stretches favor more permanent muscle elongation. 15 Care must be taken to isolate the stretch to the intended muscle. The position in which specific stretches are performed depends on the ability of the patient to avoid compensatory movements, especially lumbar extension. Hip flexors can be stretched with the patient supine in the Thomas test position (Fig 1), progressing to side-lying, half-kneeling, and eventually to unilateral standing with extension of the opposite hip while holding the ankle (Fig 2). The stretch should be held for 15 to 30 seconds, as tolerated, and repeated three to five times. These stretches are more effective when the pelvis is maintained in a posterior pelvic tilt throughout each stretch, which minimizes the tendency for compensatory hyperextension of the lumbar spine.
The hamstrings are best stretched with the patient supine, with a pelvic tilt performed before beginning the stretch. One leg is grasped at the posterior thigh with both hands, the hip is flexed to 90°, and the knee is extended until a stretch is felt in the hamstring region (Fig 3). A duration of 30 seconds has been shown to be the most effective time for stretching of hamstrings. 3 This stretch should be repeated three to five times.
The lumbar paraspinal muscles can be stretched while the patient is in the supine position or sitting. When the patient is supine, the posterior thighs are grasped after being brought up to the chest one at a time, while the patient exhales and performs a posterior pelvic tilt (Fig 4). The patient also can be instructed to raise his or her head at the same time to effect a greater stretch. This stretch is held for 10 seconds. When the patient is sitting, with his or her feet flat on the floor, the patient gently flexes his or her trunk forward. To achieve a greater stretch of the unilateral paraspinals, the ipsilateral shoulder is approximated to the contralateral knee (Fig 5). This stretch is held for 10 seconds, after which the abdominals are contracted to maintain a posterior pelvic tilt while the patient returns to the starting position. These should be repeated three times to each side.
Stretching exercises are followed by strengthening exercises, which primarily target the abdominal and gluteal muscles. The abdominal muscles are strengthened by posterior tilts, which can be performed with the patient supine, with the patient on his or her hands and knees, or with the patient standing against a wall. Pelvic tilts are held for 6 seconds and repeated 10 times. Trunk raising then is performed forward and diagonally to each side (Fig 6), targeting the rectus abdominus and oblique abdominal muscles, respectively. These are begun with the patient supine, with his or her knees bent to prevent anterior pull on the pelvis from tight hip flexors. The patients’ arms are extended forward as the head and shoulders are raised. Instructions should be given to raise and lower the trunk slowly. Ten repetitions should be performed while the patient avoids holding his or her breath.
Bridging exercises strengthen the gluteal muscles and are begun with the patient supine with his or her knees bent. A posterior pelvic tilt is performed to reduce the lumbar lordosis as the patient lifts the pelvis by extending the hips (Fig 7). This position is held for 6 seconds and repeated 10 times.
Conditioning exercises are included in the program for general fitness, and can be done in such a manner as to provide symptom relief. Walking on an inclined treadmill encourages lumbar flexion and is better tolerated than walking on level surfaces. A free reciprocal arm swing should be encouraged to simulate a natural gait and to help loosen the paraspinal muscles. 20 Likewise, exercise on a stationary bicycle also is well tolerated as patients lean forward to increase lumbar flexion and obtain symptomatic relief. If these types of exercises are not well tolerated, swimming and exercises performed in a pool allow for reduced axial loading of the spine. 9 Pelvic tilts and walking against the resistance of the water are advised. Certain swimming strokes such as the sidestroke may be well tolerated; however, the breast stroke and crawl are best avoided, because these may encourage lumbar extension. 20
Instruction in proper posture and body mechanics for activities of daily living and leisure activities completes the program. Patients should be advised to maintain a posterior pelvic tilt routinely during activities involving reaching, lifting, or carrying. Rigid braces and corsets may be used on a temporary basis to help maintain a reduced lumbar lordosis, especially before abdominal strength is sufficient to accomplish this naturally. 7 The use of a stepping stool and the placing of frequently used household items on countertops or below shoulder level may eliminate or limit the amount of overhead reaching required during the course of a day. Proper lifting techniques should be used at all times, and lifting of heavy objects should be avoided.
Patients should be advised to perform their therapeutic exercise program at home on a daily basis initially, and at least every other day thereafter. Precautions are given to discontinue any prescribed exercise or activity that leads to recurrent symptoms. Periodic reevaluation by a physical therapist often is useful to modify or advance the exercise program as appropriate.
Lumbar spinal stenosis is being recognized more frequently as a cause of pain and disability, particularly in older patients. Therapeutic exercise is one of numerous conservative measures that have been proposed to be beneficial for patients with mild to moderate symptoms of lumbar spinal stenosis. A program of therapeutic exercise is primarily intended to increase lumbar flexion and reduce lumbar lordosis, resulting in a reduction in patient symptoms and an increase in functional status. The specific therapeutic exercise program prescribed should be based on the patient history and physical examination findings, and must take any comorbidity into account. Randomized controlled studies are needed to clarify the indications for conservative versus surgical treatment, to determine which components of the therapeutic exercise program are most beneficial, and to compare outcomes after conservative or surgical measures.
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Kenneth K. Hansraj, MD; and Patrick F. O’Leary, MD Guest Editors