Chapter 7-7: Mechanical Low Back Pain

Textbook Presentation

The classic presentation is nonradiating pain and stiffness in the lower back, sometimes precipitated by heavy lifting or another muscular stress.

Disease Highlights

1. Can also have pain and stiffness in the buttocks and hips

2. Often occurs hours to days after a new or unusual exertion and improves when the patient is supine, but one-third of patients do not identify a specific precipitant

3. Can rarely make a specific anatomic diagnosis

4. New neurologic abnormalities on history or physical exam should prompt investigation of another diagnosis.

5. Lifetime prevalence of mechanical low back pain is 84%.

6. Prognosis

   1. 75–90% of patients improve within 1 month; of the subset with pain at 3 months, only 40% recover by 12 months.

   2. 25–50% of patients have additional episodes over the next year

   3. Risk factors for persistent low back pain, which occurs in 10–15% of patients, include

      1. Maladaptive pain coping behaviors

      2. High level of baseline functional impairment

      3. Low general health status

      4. Presence of psychiatric comorbidities

      5. Presence of “nonorganic signs” (signs suggesting a strong psychological component to pain, such as superficial or nonanatomic tenderness, overreaction, nonreproducibility with distraction, nonanatomic weakness or sensory changes)

Evidence-Based Diagnosis

1. The absence of all red flags is 99% predictive of a nonserious etiology of low back pain.

2. Many asymptomatic patients will have anatomic abnormalities on imaging studies.

   1. 20% of patients aged 14–25 have degenerative disks on plain radiographs.

   2. 20–75% of patients younger than 50 years have herniated disks on MRI.

   3. 40–80% of patients have bulging disks on MRI.

   4. Over 90% of patients older than age 50 have degenerative disks on MRI.

   5. 20–30% of patients over age 50 have spinal stenosis.

3. Even in symptomatic patients, anatomic abnormalities are not necessarily causative, and identifying them does not influence initial treatment decisions.

4. A specific pathoanatomic diagnosis cannot be made in 85% of patients with isolated low back pain.

5. Imaging does not improve clinical outcomes, such as pain or functional status, especially in patients with acute (< 4 weeks) or subacute (4–12 weeks) pain.

   Patients who have none of the clinical clues should not have any diagnostic imaging performed. If done, diagnostic imaging will often find clinically unimportant abnormalities. Multiple specialty societies recommend not imaging (spinal radiographs or MRI) in the absence of clinical clues.

Treatment

1. Acute low back pain

   1. The American College of Physicians has recently published evidence-based guidelines for the treatment of low back pain.

   2. Most people with acute low back pain improve over time, regardless of treatment.

   3. There is moderate quality evidence that nonsteroidal anti-inflammatory drugs (NSAIDs) or skeletal muscle relaxants are effective for acute low back pain; acetaminophen is not effective in clinical trials.

   4. Heat and spinal manipulation have been shown to reduce acute low back pain; acupuncture and massage may also help.

   5. The best approach is NSAIDs and heat during the acute phase with activity as tolerated until the pain ...