Novel Radiation-Free Assessment of Scoliosis and the Cobb Angle
Part One of Two
The diagnosis of scoliosis in children and adolescents requires the use of full spinal x-rays on which the Cobb angle is measured. Growing patients with scoliosis in risk for curve progression may be radiographed up to 4-5 times per year for a total period of 3-5 years. This may amount to a significant dose of radiation. The exposure to radiation in these patients takes place during a critical period of rapid growth that may amplify the risk of ionizing radiation.
An integral part of the follow-up process in scoliotic patients is standing C1-S1 x-rays that are obtained until curve stabilization takes place. In scoliotic patients that need to undergo corrective surgery, x-rays are obtained for even a longer time. For this reason, adolescents with scoliosis are exposed to multiple diagnostic x-rays when the growing breast tissue, thyroid or other tissues may be highly sensitive to the carcinogenic effects of radiation.
It is not surprising therefore that higher incidence of breast cancer (1), thyroid cancer and leukemia have been reported in scoliosis patients undergoing multiple full spinal x-rays (2). It has been hypothesized that the period between Tanner stage breast-2 and the onset of menarche may be a particularly sensitive biologic period to radiation exposure (1).
Hoffman et al studied the potential hazard from low-dose, fractionated exposure during early breast development (3). 1,030 women with scoliosis who were followed at four Minneapolis-Saint-Paul medical centers in Minnesota for an ultra long time for their spinal deformity were studied. Age at diagnosis of scoliosis was 12.3 years. The mean number of x-rays per patient was 41.5! X-ray exposure spanned a period of 8.7 years. The average period of observation was 26 years. Eleven cases of breast cancer were reported in the entire group, compared to only 6 cases expected. Thus a 1.6-fold increase in the incidence of breast cancer was found in women with scoliosis who were exposed to multiple spinal x-rays.
Excess risk increased with time since exposure and was highest among those followed for more than 30 years. The mean radiation dose to the breast was estimated to be 13 rads. Risk for breast cancer increased with increased amount of radiation. In a larger study entailing 5,466 female patients from numerous medical centers across the United States (US) who had adolescent scoliosis, 77 patients died from breast cancer as compared to 45.6 deaths expected on the basis of the US mortality rates (4). Thus 69% excess in breast cancer mortality in scoliotic patients was found.
Goldberg et al studied a different aspect of radiation exposure in patients with scoliosis. These investigators reported that radiation exposure of the ovaries in patients with scoliosis adversely affected the future reproductive outcome (5).
The Cobb angle measurement is the 'gold standard' of scoliosis or kyphosis evaluation endorsed by the Scoliosis Research Society (SRS). Until recently, follow-up of adolescent scoliosis patients and particularly evaluation of the treatment prescribed (either bracing or surgery) relied heavily on full spinal x-rays on which the Cobb angle is measured.
One effective way to reduce radiation exposure in scoliotic patients is to perform postero-anterior (PA) x-rays of the spine rather than obtaining antero-posterior (AP) x-rays. This will reduce the risk of developing cancer from one-half to three-quarters (6). Although the use of PA rather than AP radiographs should be rigorously adopted, ionizing radiation is still employed.
Other recommendations to reduce the radiation dose include limiting the number of views to one (PA view), proper collimation, shielding, and reduction of repeat exposure due to poor image quality. Alternative methods to evaluate the deformed spine are the Moiré topography, integrated spinal imaging system scanning and other methods using non-radiation diagnostic systems (7). None of these systems have gained the expected accuracy or wide spread use. Other investigators have proposed the use of a specially designed MRI for the purpose of scoliosis follow-up (8), however the latter technique may have a prohibitive financial cost.Ortelius800®: A Radiation-Free Cobb Angle Measurement
Recently, a new non-invasive radiation-free three-dimensional (3-D) imaging system for the diagnosis and monitoring of scoliosis and other spinal deformities has been developed (Ortelius800®, Figure 1). This new device is based on direct measurement of the position of the tips of the spinous processes in space (Figure 2). A low intensity electromagnetic field records the spatial position of a sensor attached to the examiner's finger while palpating the patient's spinous processes. The entire examination is completed in a matter of a few minutes and can be performed by a nurse, physiotherapist or the managing medical doctor.
Figure 1. Ortelius800®
Practitioner examines a patient's spine using the Ortelius800® System.