Assessment of osteoporotic spine deformity

Abstract

For the objective assessment of the severity and progression of osteoporotic deformities of the spine, a mathematical model has been developed which permits evaluation of a single set of radiographs of the spine without reference to absolute values of vertebral height. The model was based on measurements of anterior, central and posterior heights of the vertebrae Th4 to L5 of 50 subjects, aged 20 to 50 years, without a history or radiologic signs of osteoporosis or other metabolic bone disease and without traumatic deformities. The model follows a simple sinusoidal function which describes the general form of the spine, adapted to the individual's height and build. A spine fracture index (SFI) is produced and the method allows calculation of the total number of vertebral deforming events (VDE), and vertebral deformation score (VDS) in an objective manner. The method has been used prospectively in 178 spine radiographs of 109 subjects (60 healthy early postmenopausal women and 49 with osteoporosis). Sensitivity and specificity of SFI in identifying osteoporotic patients were 94 and 88% respectively. In all 109 persons, densitometry of the spine was performed by dual photon absorptiometry at the same time. In the osteoporotic patients the examination was repeated once or twice during fluoride therapy for osteoporosis. The SFI and the total score of VDE and VDS correlated significantly with lumbar bone mineral content (r = -0.38 P < 0.001). The method offers the advantage of being objective, not dependent on projection errors, and adaptable to the shape of the individual spine.