## INTRODUCTION

Key Clinical Questions

• What are the key questions that an examiner should ask when approaching a patient with acute back pain?

• What should the examiner look for on physical examination?

• What are “red flag” findings that should heighten your level of concern when approaching a patient with acute back pain?

• What are some nonspinal etiologies of back pain?

Back pain has a major impact on patient well-being and health care budgets in developed nations. It is the fifth leading cause of hospital admissions and the third most common reason for surgical procedures. Back pain ranks second only to upper respiratory tract infections as a reason for primary care physician office visits. The annual prevalence of chronic low back pain ranges from 15% to 33%, and 7% of adult patients may have low back pain at any given time. In the United States, back pain, including chronic low back pain, is the leading cause of disability in subjects younger than 45 years of age. Individuals with spine pain in the United States account for nearly $90 billion yearly in direct health care expenditures with an additional$20 billion yearly in indirect costs related to lost productivity with approximately 2% of the US workforce compensated for back injuries each year.

Roughly 95% of visits for back pain stem from benign causes. However, in hospitalized patients, the percentage with serious pathology may be higher, so clinicians have to have a high index of suspicion. This chapter focuses on the initial evaluation of acute low back pain in patients admitted to the hospital as well as patients hospitalized for other reasons who develop back pain as a complication of hospitalization.

## PATHOPHYSIOLOGY

The function of the anterior spine is to absorb the shock of body movements such as walking and running. The function of the posterior spine is to protect the spinal cord and nerves, and to stabilize the spine by providing sites for attachment of muscles and ligaments. The normal alignment of the spine is notable for the following:

• Lumbar and cervical lordosis and thoracic kyphosis on lateral view

• Straight column on anterior view

Movements of the cervical and lumbar regions are greater than the thoracic regions during activity. The elasticity of vertebral disks—largest in the cervical and lumbar regions—allows the bony vertebrae of the spine to move easily upon one another. Elasticity declines with age.

CASE 76-1 ACUTE ABDOMINAL AND BACK PAIN IN AN EMERGENT SETTING

An 81-year-old man with a history of myocardial infarction 10 years ago presented with new-onset low back pain and crampy abdominal pain that had begun 2 hours prior. He had never had this type of back pain before. His exam revealed a blood pressure of 110/70 mm Hg. His creatinine was 2.5 mg/dL with a glomerular filtration rate of < 35/mL/1.73 m2 which is his baseline ...

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