How to evaluate acute and chronic low back pain?
Acute versus chronic low back pain represent two separate and distinct issues. Acute pain, regardless of location, is typically associated with tissue damage and serves a protective function. Chronic pain, in contradistinction, is typically thought of as pain that has outlived its purpose or protective function. In the case of chronic low back pain, the persistence of pain actually negatively impacts on the patient’s ability to participate in activities of daily living, as well as vocational and avocational activities.
Initial assessment of the patient with low back pain, regardless of acuity versus chronicity, should entail observation. Patients should be observed while they ambulate to the examining room. Significant data can be gleaned during this period of the physical exam, as the patient does not appreciate that the exam has already started, and as such more objective data may be obtained than during the formal exam. This is particularly true in the patient with chronic low back pain issues. Many maladaptive movements may be delineated during the initial observation period.
Once in the room, observation should continue during the history taking. Does the patient prefer to sit as opposed to stand? A patient who is comfortable sitting and prefers to sit and does not change position from sit to stand may well have lumbar stenosis, or posterior column issues, such as facet joint arthropathy. Patients who prefer to stand may well have anterior and middle column dysfunction related to lumbar vertebral disc issues. Patients who constantly change position during the interview may have underlying degenerative changes in their lumbar spine, but may be primarily symptomatic with reactive muscle spasm and dysfunction secondary to the underlying degenerative changes in the lumbar spine. A classic case would be the patient who notes limited sitting tolerance with marked low back pain and stiffness noted after arising from prolonged sitting, such as going to the movies. In this instance, reactive psoas muscle spasm secondary to chronic muscle shortening may well be the problem, and a physical therapy program designed to address this issue may work quite well.
Acute low back pain is typically associated with a distinct event specific inciting event. Lifting and twisting mechanisms are most common causes of acute low back pain. They may result in acute disc herniation, muscle strain, or possibly even compression fracture. The risk for compression fracture increases with age. Additionally, female gender ethnicity and slender body habitus also increase risk for compression fracture. In the patient with the correct demographics, acute low back pain that is localized to the back and worsened with sitting or bending forward is highly concerning for a compression fracture and does warrant immediate radiographic assessment. Correlative findings on x-ray confirm the clinical diagnosis and help guide treatment. In the acutely symptomatic lumbar compression, fracture management with a lumbosacral orthosis to limit flexion will be very helpful for managing pain and restoring patient mobility. Those patients experiencing frequent fractures should receive a workup for osteoporosis by their primary care physician or referred to an endocrinologist or rheumatologist.
Evaluation of the patient with acute low back pain should initially focus on mechanism in injury. Twisting type activities or twisting with lifting are common causes of acute disc herniation. Pertinent parts of the history should include what positions or activities intensify as well as relieve symptoms. Is there a pattern or distribution of pain? Does the patient note any weakness in the leg? What tasks are problematic? And lastly what is the status of bladder function? Typically in a patient where there is concern for a cauda equine spinal cord syndrome secondary to massive low lumbar disc extrusion, bladder incontinence will be more quickly noted than bowel dysfunction if for no other reason than it is more difficult to control liquids than solids. As such, careful questioning regarding bladder function is imperative when trying to determine if a patient may have a cauda equine syndrome. Alteration in saddle distribution sensation is also helpful, but less reliable. When truly present on physical examination, it is highly correlative, but as a subjective complaint much less so.