Diagnosis and treatment of back pain.

After completing this article, the reader should be able to:

* Describe the anatomy of the spine and explain why precise diagnosis of back pain is difficult.

* Summarize some of the ways in which psychosocial factors might influence back pain.

* Discuss which imaging studies are used to assist in diagnosis and what drawbacks exist to imaging in the absence of red flags.

* Address special considerations in imaging back pain patients.

* Explain different treatment options, including complementary treatments.

Back pain in its varied presentations is notoriously difficult to diagnose, and descriptions of diagnostic errors unfortunately abound. Imaging plays an increasing role in helping physicians pinpoint the cause of back pain, determine what treatments might be most appropriate and gain a better understanding of the processes underlying this all-too-common phenomenon.

About 10% of adults suffer from chronic pain, and back pain is the leading cause of chronic pain. Chronic pain predictably reduces the quality of life, increases anxiety and depression and now is associated with cognitive and morphological brain abnormalities. (1) Some researchers claim that the proportion of patients whose chronic low back pain (LBP) cannot be diagnosed properly would be reduced by as much as 50% if the potential of modern diagnostic techniques (ie, imaging) were recognized. (2) Imaging also is used to explore brain activity associated with pain, assisting scientists in obtaining a new understanding of the physiological changes associated with pain.

Still, obtaining an accurate diagnosis can be a long process. In 1 instance, a 71-year-old woman was referred to neurosurgeons following a history of LBP that had lasted for more than 10 years. (3) At first, as is typical practice, the woman's general practitioner attributed the back pain to a mechanical cause and recommended conservative treatment that resulted in some level of improvement. After 5 years, however, the pain worsened, and several other diagnoses were proposed, including arthritis, muscle strain and even psychosomatic pain. A full 10 years into the saga, the patient began to experience radiating pain near her knee, numbness and a decreased knee jerk. A neurological examination was otherwise normal, and lumbar-spine radiography showed only expected arthritic changes. Finally, magnetic resonance (MR) imaging permitted physicians to see a mass attached to a nerve root in the lumbar spine. Once the mass was removed, the patient experienced complete relief of her long-term symptoms. It had taken more than 10 years to achieve an accurate diagnosis and obtain true relief of her pain.

Sometimes, pain does not prompt diagnosis and treatment. In another case, a 29-year-old man who had no pain simply went for a Chinese massage, during which a mass was palpated in his right lower abdomen. Although he did not demonstrate any neurological impairment, an MR scan showed a large mass ventral to the spinal column (see Figure 1). The benign tumor was removed surgically without any adverse consequences. (4)

How Common Is Back Pain?

The only neurological complaint more common than back pain is headache. (5) Back problems are recurrent--rarely do they go away and stay away. (6) Between 5% and 10% of patients will develop chronic back pain. (7) Back pain generally is characterized as LBP or other, less common forms of back pain. With respect to acute LBP, the annual consultation rate is at least 35 per 1000 adults. (8) Americans spend more than $50 billion each year on LBP, which is the most common cause of job-related disability and a major contributor to missed work. (5) The American Academy of Orthopaedic Surgeons reported that back pain leads to nearly 12 million visits to physicians' offices each year and that 80% of the population will at some time experience some form of back pain. (9) Other estimates place the figure even higher, predicting that up to 95% of Americans will experience back pain during the course of their lifetimes. (10) Approximately 15% of all adults have recurring LBP, and at least 5% become disabled due to LBE. (11) In 1998, total expenditures associated with back pain in the United States were reported to be more than $90 billion. (12) In 2003, the most recent year data are available, that figure was reported to be a full $10 billion higher. (13)

Americans have not cornered the market on back pain. In the United Kingdom, direct costs associated with disability due to LBP in 1998 were estimated at around 1.6 billion [pounds sterling] per year, with approximately 120 million work days lost. (14) At least once a year, a full 7% of the UK adult population consults a physician regarding LBP. (15) Researchers claim that more than 70% of people in developed countries will experience LBP at some point. (7) In the Netherlands, the costs to society of LBP have been estimated to be 1.7% of the gross national product, with 64% of those costs attributed to absenteeism from work. (16)

Much of back pain can be attributed to lifestyle choices: obesity, sedentary work and home environments and lack of consistent exercise. For some, including health care workers, back pain may be an occupational risk. Given the inherent costs to society, some argue that back pain should be demedicalized and in the absence of clear pathology and red flags indicating probable complications patients should be referred for physical therapy and prescribed exercise programs. (8) That argument might be bolstered by the results of some studies that have shown that about 90% of patients with LBP will have stopped conulting their primary care physician within 3 months. (17)

[FIGURE 1 OMITTED]

Early and accurate diagnosis of back pain and targeting appropriate treatment will reduce patient suffering and the medical and work-related costs of back pain. Diagnostic accuracy is essential for effective treatment. With respect to disk pain, pain patterns provide minimal diagnostic information, and the practice of diagnosing back pain based solely on patients' pain maps or drawings has been shown to have little real success. (2) Rarely can physical examinations distinguish between pain caused by a disk problem and some other cause. In children and adolescents, it is essential to rule out an organic etiology as a cause of back pain. (18) Thus, imaging has an important role to play in refining diagnoses and choosing a treatment. This article focuses on when and how imaging can contribute to a better solution to the problem of back pain.

Anatomy of the Back

Back pain is difficult to diagnose, largely due to the back's complex anatomical structure. It is composed of bone, muscle, ligaments, tendons and a network of neurological components. (19) The spine, or spinal column, which is made up of more than 30 vertebrae, supports the weight of the upper body and surrounds and protects the spinal cord. (5) More than 50 nerve roots enter and exit the spinal cord through spaces between the vertebrae; the intervertebral spaces are maintained by circular, spongy pads of cartilage known as intervertebral disks. (5) These cushioning disks allow flexibility in the lower back and act as a form of shock absorber. Facet joints are the places on each vertebra where the bone articulates with another vertebra, rib or both. (10,20) In the lower back, facet joints carry from 10% to 15% of the compressive load. (10) Ligaments and tendons hold the vertebrae in place and attach muscles to the spinal column.

[FIGURE 2 OMITTED]

The vertebrae are divided into 4 sections: There are 7 cervical (neck) vertebrae (C1-7), 12 thoracic (upper back) vertebrae (Tl-12), 5 lumbar (lower back) vertebrae (L1-5), and a group of bones fused together at the base of the spine known as the sacrum and coccyx (see Figure 2). (5) When the anatomical structure of the spine is altered so that the various parts cannot interact properly, dysfunction results and pain can occur. Predictably, most back pain is found in the lumbar area, which is responsible for supporting the majority of the upper body's weight. This is also the area of the spine that exhibits the most movement. Lumbar spinal motion is quite varied: The healthy lumbar spine flexes, extends, bends laterally and rotates on its axis. (10)

The lumbar disks are composed of:

* An outer rim or annulus fibrosus, which is made up of fibrous tissue.

* The core or nucleus pulposus. A healthy core is approximately 70% water.

* The top and bottom of the disk, also known as the cartilaginous end plates, which are the portions that rest against the neighboring vertebrae. (21)

Disks are the largest structures without a vascular system in the body. Blood vessels lie on the surface only, and so they obtain nutrition from diffusion through the end plates. In addition, disks are only minimally innervated; nerve endings are found only on the surface of the disk. (21)

Disks are designed with crisscrossing fibers that permit them to withstand twisting and other dynamic loads, but they still can tear and cause "discogenic" pain. Lumbar disk herniations are one of the most common diagnoses, and there is significant controversy concerning what treatment is most appropriate for herniated disks. When a disk becomes herniated, either the core or the outer rim of the disk protrudes through its confining membrane. (20) Sometimes these bulges impinge on nerve roots, resulting in pain. Often, however, they are asymptomatic. (21)

The Varied Faces of Pain