Epidemiology and Natural History of Spondylogenic Backache

“It’ not so much the pain the man has, it is more the man who has the pain.”

–Ian Macnab (1950s)

Although backache (with or without sciatica) is a benign, often self-limiting condition, it drains up to $90 billion per year (18) from the American government’s health care budget. This has increased approximately $30 billion since the mid-1980s (7). The cost of both time lost from work (with loss of productivity) and medical care, as well as the cost of litigation and disability claims, make back pain an industry unto itself. Competing for attention for this “cash flow” are members of all manners of disciplines, each claiming to have the “answer.”

Facts and Factors

Epidemiologic studies generate two sets of statistics:

Facts: The incidence (new cases per period of time) and the prevalence (all cases) as a measure of the natural history of the disease
Factors: Environmental (especially industrial) and individual factors that affect the incidence of low back pain and can be altered to decrease morbidity

Facts

Low back pain is a high-profile symptom in industrialized societies. A study in England (8) revealed that 2% of the population annually sought medical care for back pain. Frymoyer et al. (9) have shown that during a lifetime, 70% of men will have an episode of low back pain.

Further facts that reveal the extent of low back pain as a problem for society are as follows:

In the United States, 2.5 million workers are injured per year (14).
Each year, 2% of all employees have a back injury (14).
Each year, 28.6 days per 100 workers are lost (14) (this amounts to 17 million work days per year in the United States).
At any one time, there are 1.2 million low-back-disabled adults in the United States (14).
In the United Kingdom, 1 in 25 men changes his job each year because of a low back injury (10).

In the industrial commission field, Snook and Jensen (24) have pointed out how difficult it is to calculate the cost of low back pain, because there are so many sources of payment to an injured worker. These include (a) wages that are paid during the waiting period before compensation from workmen’s compensation insurance, (b) group and individual health insurance plans, and (c) Social Security benefits. The direct cost of back injuries to the industrial commissions in the United States totals $11 billion per year (24). Back injuries account for 20% of all compensable injuries but incur one third of the cost per year. It is estimated that the average cost per case is $6,000 and that, within the category of low back pain, 25% of the injuries account for 90% of the costs.

Low back pain accounts for a considerable annual volume of surgery in the United States. Approximately 150,000 patients undergo a simple laminectomy for removal of a herniated disc, and another 150,000 per year undergo spine surgery for some other degenerative condition (5). As the number of specialists who call themselves spine surgeons increases, so does the number of operations. To date, no investigator has been able to determine if Americans are better off as a result of the increase in back-spine specialists (23).

Factors Affecting Incidence of Lumbar Disc Disease (Disc Degeneration and Disc Herniation)

Age

Low back pain is most prevalent between the ages of 35 and 55 years. However, most patients in this age group have had a prior episode of back pain before age 35 years. Most operations for low back degenerative conditions occur between the ages of 35 and 55: younger patients usually undergo operations at the L5-S1 level, whereas surgery for the older patient usually involves the L4–5 level (13).

A herniated nucleus pulposus is more likely to occur between the ages to 30 and 40 years (13,22), at which time the disc is on its way to degeneration through a decrease in its water content. In patients younger than the age of 30 years, the resilience of the disc protects it from herniation; in patients older than the age of 40 years, a disc has developed some degree of inherent stability through fibrous changes that occur with the loss of turgor (14). However, there are so many exceptions to these age rules that they serve as little more than general guidelines.

Sex

In the general population, the incidence of low back pain appears to be equally distributed between men and women. It is well known that workers exposed to heavy work, especially twisting and lifting, have a higher incidence of back pain. A female worker is more exposed to injury through these forces, but because there are so many more men in the heavy work force, the incidence of back injury in the working population is heavily weighted toward men (13).

Body Build (Anthropometry)

There does not appear to be any strong correlation between height, weight, body build, and the occurrence of low back pain (6).

Posture

Postural deformities such as scoliosis, kyphosis, hypo- and hyperlordosis, and leg length discrepancy do not predispose to low back pain.

Spine Mobility and Strength

After injury there is a decrease in low back strength and mobility (22

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