Back pain is so widespread that it is the most common cause of work disability and early retirement, with patients getting younger and younger. Children are now diagnosed with postural deformity, tilted pelvis, scoliosis, or kyphosis at preschool age. To help physicians find the exact cause of the pain and prescribe effective therapies, Diers International (Schlangenbad, Germany; www.diers.de) has developed the 3- or 4-D "formetric" method, which measures the spine by taking a stereographic image of the back. First developed in cooperation with several universities and the European Union, the original goal was to build a radiation-free biomechanical measuring method that would spare children with scoliosis from frequent x-ray exposure.
A grid is projected on the patient's back with a light beam and scanned with a camera. From the image, the system calculates anatomical landmarks such as the seventh cervical vertebra or the "pelvic dimples" and derives the spine posture from these data at an accuracy of one- to two-tenths millimeter. During the measurement, the patient stands in an upright position about 2 m from the height-adjustable scanner. The image-acquisition time of 40 ms accommodates the fact that children, in particular, never stand absolutely still. Diers uses the uEye series UI-1540-M USB 2.0 camera from IDS Imaging Development Systems (Obersulm, Germany; www.ids-imaging.com), which can obtain high-resolution images for dynamic measurements such as on a treadmill--an activity that requires a capture rate of 10 frames/s.
