It is a common misconception that late-onset idiopathic scoliosis leads to cardiopulmonary disability and severe back pain. Untreated late-onset idiopathic scoliosis appears to progress throughout adulthood, with a change of about 1 degree per year. A prospective study by Weinstein and colleagues examines the natural history of late-onset idiopathic scoliosis, differing from studies that were flawed by the inclusion of heterogeneous types of scoliosis. Their study suggests that a better understanding of the true natural history of late-onset idiopathic scoliosis will guide preventive treatment decisions.

The cohort included 444 patients diagnosed with late-onset idiopathic scoliosis between 1932 and 1948. Patients with a history of fusions and those who had been misdiagnosed were excluded. Patients who were missing, had died, or refused to participate also were excluded, leaving 117 eligible patients and 62 matched control subjects. Outcome measures were mortality, back pain, pulmonary symptoms, general function, depression, and body image.

Of 117 patients, 104 (89 percent) were women. The authors documented curve type and Cobb angle. Except for persons with double curves, radiographs and Cobb angle did not differ significantly from the 27 patients who refused to participate. All patients included in the study filled out questionnaires.

Survival probability did not differ significantly among patients with scoliosis from the birth cohort. Results of physical examination were within normal limits except for diminished chest expansion in some patients. Of the 79 patients with current radiographs, 72 (91 percent) had evidence of arthritis or other radiographic changes. Twenty-two (22 percent) of 98 patients reported exertional shortness of breath compared with eight (15 percent) of 53 controls. A Cobb angle of greater than 50 degrees at skeletal maturity was associated with significantly increased odds of developing shortness of breath.

Both acute and chronic back pain were more prevalent in patients relative to controls, although there were no differences in duration or intensity among patients from either group who had pain. Ability to perform activities of daily living did not differ between groups. Thirty-seven (39 percent) of 94 patients said they had a disability compared with 16 (30 percent) of 53 controls, largely because of back problems in both groups. Patients with scoliosis were slightly dissatisfied to slightly satisfied with their body image, whereas control patients were slightly to moderately satisfied.

The authors find no evidence linking untreated late-onset idiopathic scoliosis to increased rates of mortality. Although untreated late-onset idiopathic scoliosis is associated with more back pain, it does not appear to cause excessive disability, and patients are able to work and perform activities of daily living as well as their peers. However, having a Cobb angle of greater than 50 degrees at skeletal maturity is highly predictive of pulmonary symptoms, whereas patients with curves of less than 30 degrees at skeletal maturity rarely get worse. Recommendations regarding bracing and surgery should be made in the context of accurate information about the natural history of the disease.

editor's note: This study confirms previous knowledge that curves of less than 30 degrees are unlikely to progress, whereas curves greater than 50 degrees tend to progress at a predictable rate. Although it is reassuring that late-onset idiopathic scoliosis rarely causes severe impairment or death, this study shows that some impairment and cosmetic defects are common. Given that bracing can alter this natural history and surgical intervention can correct some deformities, it is unclear how a full knowledge of the natural history would affect decision-making. There could even be untoward effects. Conceivably, an adolescent wary of bracing or surgery could use this information as an excuse to avoid stigmatization, only to regret later not having chosen intervention in a more timely fashion.—C.W.