Predicting Success After Lumbar Spine Surgery
It's very confusing trying to figure out ahead of time which patients will benefit from back surgery. Surgeons are always looking for predictive factors to help them identify who should have surgery and who would be better off without surgery.

One of those predictors is the use of pain drawings. Patients draw lines, X's, dots, and use letters like N for numbness or S for muscle cramps on a picture of the human body. The various markings show where pain is located and what kind of pain it is.

The value of the pain drawing as a predictor of success versus failure with lumbar spinal fusion surgery remains unknown. Some studies show it is helpful; others do not. The authors of this study (spine researchers and surgeons from Denmark) took a closer look at the pain drawing as a predictive tool. They add their findings to the mix and offer some ideas about how to interpret the conflicting data.

One of the problems in comparing studies done in this area is the different type of pain problems included in the research. Some studies only include patients who have back but not buttock or leg pain.

Other studies include only patients with both back and leg pain. And like this study, the researchers allow patients with either or both. In fact, about three-fourths of the patients in this study had back and leg pain.

The reason this feature can be so confusing is that patients with both back and leg pain judge their improvement as greater and are more satisfied when there is an improvement in their pain. Patients with only back pain might also improve but it's not as noticeable as when the pain has two locations. The accumulation of pain in both sites can make it seem much worse than just back or just leg pain.

Another problem area in studying the use of the pain picture as a predictive factor in outcome after lumbar spinal fusion is the fact that patients with chronic low back pain who are potential candidates for fusion have different diagnoses. They could have pain associated with degenerative disc disease, spinal stenosis (narrowing of the spinal canal), or spondylolisthesis (tiny fracture or disruption of the supporting column of the vertebral bone).

They also have different levels of disability and severity of disease. It's possible that any one of these variables could have a direct link to the pain drawing but it's difficult to study just one of these differences at a time. They get all lumped together in the same study so no one knows which variable or combinations of differences affect the outcome or can be predicted by the use of a pain drawing.

In this study, only adults between the ages of 21 and 59 with back pain from spondylolisthesis or degenerative changes were included. They all filled out the pain drawing before surgery. They also completed several other standard and well known outcome measures (e.g., Dallas Pain Questionnaire, Low Back Pain Rating Scale).

Pain drawings can be classified as organic or nonorganic. Organic pain is presented as a clearly identifiable pattern. It occurs in the thoracic spine (middle part of the spine). Nonorganic has a strange pattern of pain all over the body with no clear pattern. Results for the two groups were compared to one another.

They found that women were more likely to have nonorganic pain. Likewise, patients who had a previous spine surgery were more likely to draw a picture of nonorganic pain. In this study, patients with nonorganic pain drawings expressed greater dissatisfaction with results of fusion surgery. On the other hand, patients with organic pain were more likely to report better results after surgery -- even when they had more levels fused than in the nonorganic group.

Work status (retired or on sick leave) and insurance or litigation claims were two other predictive factors of poor outcome -- these were the patients most likely to have nonorganic pain drawings. Patients who reported pain lasting more than two years, patients who smoked, and younger patients were also at risk for poor results after surgery.

What do the results of this study add to the debate about pain drawings as a predictive tool of results after spinal fusion? The key finding here may have to do with patient expectations. Patients with nonorganic pain drawings may have unrealistic expectations of surgery and end up disappointed as a result.

As mentioned, those with back and leg pain seem to get greater pain relief. This is especially true of patients with organic pain drawings. And improvement was greater from before to after surgery in patients with organic pain linked with a diagnosis of spondylolisthesis (tiny fracture defect in the supportive bone).

The authors conclude that the pain drawing is not a good tool to use when deciding who should have surgery. But it can be used along with other risk factors (e.g., work status, age, smoking, legal issues) to predict results. The more risk factors present, the greater the likelihood of poor outcomes. Likewise, the reverse may be true: the fewer risk factors, the better the chances for a good outcome.
Thomas Andersen, MD, PhD, et al. The Predictive Value of Pain Drawings in Lumbar Spinal Fusion Surgery. In The Spine Journal. May 2010. Vol. 10. No. 5. Pp. 372-379.