Mechanical Low Back Pain Clinical Presentation

Patients generally present with a history of an inciting event that produced immediate low back pain (LBP). The most commonly reported histories include the following:

• Lifting and/or twisting while holding a heavy object (eg, box, child, nursing home resident, a package on a conveyor)
• Operating a machine that vibrates
• Prolonged sitting (eg, long-distance truck driving, police patrolling)^[10]
• Involvement in a motor vehicle collision
• Falls

Commence the history by asking for the patient's age, hand dominance, and occupation. Also ask about the patient's current work status and last day he or she worked. If the back pain is the result of a work-related injury, ask the name of the employer and inquire how long the patient has worked for this particular employer. Sample questions are as follows:

• When did the current symptoms begin and what were you doing?
• What and where are your symptoms now? (A pain diagram is helpful for localizing the symptoms. The patient can draw on a figure and give the clinician an idea of the nature of the pain as neuropathic or nociceptive.)
• Rate the pain on a scale of 0 (none) to 10 (worst imaginable). This is a global pain rating that takes into account physiological and psychological aspects of the LBP.
• What makes the pain better (eg, sitting, standing, laying, medications, physical therapy)?
• What makes the pain worse (eg, sitting, standing, laying, medications, physical therapy)?
• What affect have these symptoms had on sleep, mood, work, activities of daily living, and/or social functioning?

Use open-ended questions to ascertain the maximum information about the patient's history. Establishing a rapport with the patient is essential to detect serious conditions, provide insights into the patient's concerns and expectations, and to achieve the optimum positive response to treatment.

In addition to the history of the present illness, the past medical history should be obtained to rule out infections (eg, septic arthritis), congenital abnormalities (eg, dysplasias, juvenile rheumatoid arthritis), metabolic disorders (eg, Paget disease), or previous traumatic causes (eg, athletic participation, military service).

The review of systems is helpful for relating the current symptoms to any other body parts or systems. Interruption in bowel or bladder function should be a reminder to consider more serious causes of back pain such as a tumor, infection, or fracture. Review of systems also should include a thorough medical history (including history of cancer, arthritis, infection, systemic disease that could increase susceptibility to infection, nocturnal pain, fever, drug use, depression, and symptoms suggestive of metabolic or metastatic disease). Ask for any history of headaches, peptic ulcer disease, prior cancer, or unexplained weight loss.

Assess for any history of previous treatments, such as the following:

• Surgery
• Medications: Obtain as complete a listing as possible, including reasons for discontinuation.
• Physical therapy
• Psychiatric or psychological therapy

Thoroughly screen for anxiety, depression, addiction, somatoform disorders, personality disorders, other prior psychiatric diagnoses, coping styles, and personality traits. Psychosocial factors (eg, depression, hypochondriasis, heavy alcohol consumption, tobacco use, menial work, poor job satisfaction, stressors at home and/or work) may accompany histories involving a work-related injury.

Assess the patient's vocational history. Look for consistency in the type of work and length of service with each employer since high school or college. Ask how many years the patient has been working for his or her current employer. Some cases have involved patients who have worked less than a week on a new job. Some work-related injuries are reported on a Monday or after a vacation. These are important dates for determining if the LBP was indeed work-related.

In a work-related LBP case, ask the patient about pending or planned litigation and related expectations.

Ask the patient what he or she thinks about the cause of the LBP.

Ask the patient what his or her goals are for the evaluation and treatment.

If the patient brought imaging study results (eg, plain radiographs, computed tomography [CT] scans, magnetic resonance imaging [MRI] scans), look for imaging evidence of herniated nucleus pulposus (seen in the images below), spinal stenosis, or other conditions associated with back pain.

An important part of the physical examination is the general observation of the patient. The patient presents with pain in the low back region and often places his or her whole hand against the skin to indicate a regional pain; however, in some cases the patient may indicate a more precise location.

Realize that much of the physical examination is subjective because a patient-generated response or interpretation to the examiner's questions or maneuvers is required. For example, sensory findings observed during the physical examination and reported symptoms in response to provocative testing are reliant on the patient's response and, hence, represent a somewhat subjective portion of the physical examination. A well-performed and well-documented physical examination, with consistent findings from one visit to the next, can yield important information that may be able to stand up to rigorous scrutiny by any involved third parties (eg, insurance company, attorney, workers' compensation judge). These physical examination findings would need to be put into the context of the patient's symptoms and diagnostic test results.

Equipment often used for the examination includes a stethoscope, goniometer, inclinometer, pinwheel or safety pin, tape measure, and reflex hammer.

Testing

Observe the patient walking into the office or examining room. Observe the patient during the history-gathering portion of the visit for development, nutrition, deformities, and attention to grooming.

Measure blood pressure, pulse, respirations, temperature, height, and weight.

Inspect the back for signs of asymmetry, lesions, scars, trauma, or previous surgery.

Note chest expansion. If it is less than 2.5 cm, this finding can be specific, but not sensitive, for ankylosing spondylitis.

Take measurements of the calf circumferences (at midcalf). Differences of less than 2 cm are considered normal variation.

Measure lumbar range of motion (ROM) in forward bending while standing (Schober test).

The neurologic examination should test 2 muscles and 1 reflex representing each lumbar root to accurately distinguish between focal neuropathy and root problems.

Measure leg lengths (anterior superior iliac spine to medial malleolus) if side-to-side discrepancy is suspected.

Using the inclinometer, measure forward, backward, and lateral bending. With the goniometer positioned in a horizontal plane over the axial skeleton (ie, over the head), measure trunk rotation.

The AMA Guides to the Evaluation of Permanent Impairment (5th edition) include reference tables for all motions, but these figures are not based on empiric data, only on consensus.^[12] The ROM measurements in the AMA Guides do not correlate with disability and are not consistent within the document itself.

Palpate the entire spine to identify vertebral tenderness that may be a nonspecific finding of fracture or other cause of low back pain (LBP). Note any asymmetry, misalignment, or step-off between vertebral bodies. Remember also to palpate the sacroiliac joints.

Test for manual muscle strength in both lower extremities. The Medical Research Council rating is an ordinal scale used for this purpose (0 = absent strength, 1 = trace muscle movement, 2 = poor muscle strength [less than antigravity], 3 = fair muscle strength [antigravity strength through normal arc of motion], 4 = good strength, and 5 = normal strength).

Table 1. Functional Muscle Testing (Open Table in a new window)

Test for sensation and reflexes using 0-2 ordinal scale for pinprick sensation (0 = no sensation, 1 = diminished sensation, and 2 = normal sensation), and 0-4 ordinal scale to rate reflexes (0 = no reflex, 1 = hyporeflexic, 2 = normal reflex, 3 = hyperreflexic, and 4 = hyperreflexic with clonus).

Table 2. Dermatomal Sensory and Reflex Testing (Open Table in a new window)

Clinical tests for signs of sciatic nerve tension are as follows:

• Supine straight leg raising (SLR) test - Reproduction of pain caused by elevation of the contralateral limb raises the probability of a disk herniation to 98%. Remember that the SLR test result can be negative in persons with spinal stenosis.
• Sitting SLR (knee extension) test (for lower roots) - The patient should sit on the table edge with both hips and knees flexed at 90° and extend the knee slowly. This maneuver stretches the nerve roots as much as a moderate degree of supine SLR. The SLR test result, if positive, reproduces symptoms of sciatica with pain that radiates below the knee.
• The prone SLR test (also called the reverse SLR test or the femoral nerve stretch test) assesses the upper lumbar roots, a less common site of radiculopathy worth remembering.

Nonphysiologic testing (Waddell signs) should be performed. The presence of 3 or more positive findings out of the 5 types may be clinically significant in terms of psychosocial issues or poor surgical outcome. Isolated positive signs are of limited value.

Nonorganic tenderness consists of the following:

• Superficial - Skin tenderness to light pinch over a wide area of lumbar surface
• Nonanatomic - Deep tenderness over a wide area, often extending cephalad to the thoracic spine or caudad to the sacrum

Simulation tests give the patient the impression that a particular examination is being conducted, including the following:

• Axial loading - Vertical loading over the patient's head while he or she is standing, producing LBP
• Rotation - Back pain when the shoulders and pelvis are rotated passively in the same plane with the feet together

Distraction tests indicate a positive finding when the patient's attention is distracted.

• SLR - Observing an improvement of 30-40° when the patient is distracted, compared with formal testing.
• Flip test - The patient is seated with the legs dangling over the examination table. Instruct the patient to steady himself or herself by holding the edge of the table. When the affected leg is flipped up quickly, the patient falls back and lets go, placing both hands behind him or her on the table.

Regional disturbances that do not correlate with anatomy include the following:

• Weakness - Cogwheeling (giving way) of many muscle groups upon manual muscle testing of strength
• Sensory - Diminished light touch or pinprick sensation in a stocking pattern, rather than a dermatomal pattern, in an individual who is not diabetic
• Nonanatomic sensory loss

Overreaction during the examination may be observed in several manifestations (eg, disproportionate verbalization, facial grimacing, muscle tension and tremor, collapsing, sweating). Care must be taken to account for cultural variations.

In addition, evaluate the patient's function. Observe ROM and flexibility, ability to dress and undress, and ability to rise from a chair or the examination table.