Subtypes of Low Back Pain
Many primary care providers use what has been termed the "black box" approach to back pain: Having excluded herniated disks requiring intervention and pertinent secondary pathology, all other back pain is treated conservatively and symptomatically. On the other hand, specialty groups often strive for much more specific diagnoses and direct therapies believed to be targeted to particular diagnoses (e.g., injection for trigger points). This study examined the subtypes of back pain seen in a group model HMO, population 54,000.
Subtypes of low back pain were delineated by a consensus group of representatives from the departments of family practice, internal medicine, orthopedics, neurosurgery, and physical therapy.
Over a nine-month period, 32% of acute back pain cases in this HMO were categorized as acute low back strain, characterized as related to a history of recent significant injury, accompanied by diffuse tenderness in the low back, a normal neurologic examination, and normal sacroiliac exam.
Radicular syndromes (presenting with leg pain in addition to back pain, limited straight leg raise, and motor or sensory nerve root signs) comprised 28% of patients. Posterior facet syndrome was defined as precipitated by twisting the spine or lifting in rotation, with recent onset of acute pain, tenderness 1-2 inches lateral to the spinous processes, worsening by extension or rotation, limited painful range of motion toward the involved side, and a normal neurological exam; 6% of cases fell into this category. Somewhat more common (10%) was sacroiliac syndrome, defined by tenderness over the sacrum or sacroiliac line, pain upon sacroiliac joint stress, and a normal neurologic examination. The remaining 10% of acute cases included trigger points, coccidynia, piriformis syndrome, and others, which the authors note have been reported substantially more prevalently in reports from specialty clinics.
Whether such a classification system will benefit the clinician or patient in approaching this clinical problem remains to be determined.
Newton W, et al. J Fam Pract 1997; 45:331-335.
Clinical Scenario: The 12-lead tracing shown in the figure was obtained at peak exercise during a stress test performed on a 73-year-old woman. Her chief complaint was shortness of breath during activities of daily living. The exercise test was stopped at the stage shown in the figure because of chest tightness. She had just completed nine minutes on the treadmill. Despite progressively increasing her workload during the test, her heart rate had not increased over the last three stages. The blood pressure response to exercise was normal. In view of the fact that this patient is not on any rate-slowing medications and is not known to have coronary disease, how would you interpret the results?
Interpretation: The history and peak exercise tracing shown in the figure are consistent with the diagnosis of chronotropic incompetence. Although baseline artifact makes interpretation of this peak exercise tracing more difficult, it is doubtful that there is anything more than slight ST segment flattening and minimal ST depression. Instead, the most remarkable finding in this patient who is not on any rate-slowing medication is the inappropriate heart rate response to exercise.
True chronotropic incompetence (in which failure to appropriately increase heart rate with progressive exercise is not the result of effort-limiting chest pain) is a relatively uncommon phenomenon. Froehlicher suggests that patients with chronotropic incompetence represent a mixed group with several explanations for their limited heart rate response.1 These include myocardial dysfunction, coronary disease with an anginal equivalent, and a normal variant. Whether this entity reflects a manifestation of sick sinus syndrome in some individuals is uncertain. In this particular case, given the marked impairment of exercise capacity in this 73-year-old woman, cardiac catheterization should be strongly considered to define her anatomy.
Reference
1. Froehlicher VF, et al. Exercise and the Heart, 3rd ed. St. Louis: Mosby; 1993:90-91.
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