Compression fractures with anterior wedging of the vertebral body are the most frequent fractures of the thoraco-lumbal spine. As yet, there is no fracture classification that has achieved general clinical acceptance. A classification is presented that defines fractures as A, B, and C types, according to their pathomorphology and mechanical stability. The main types are subdivided into A1-A2, B1-B2 and C1-C2. The A fractures incorporated a compression lesion of the anterior column with minimal or moderate loss of anterior height of the vertebral body. An intact intervertebral disc defines the A1 lesion. With loss of disc function through disc rupture into the fractured body, the vertebral segment is biomechanically destabilized and the lesion is classified as A2. The B-type wedge compression fracture defines a disc and bone lesion of the anterior column with severe wedging combined with a distraction lesion of the posterior column involving mostly ligaments. Not infrequently, the middle column presents with a dorso-cranial wall fragment, which may be dislocated into the spinal but without endangering the cord. Isolated lesions of the anterior and posterior columns are considered B1 lesions. B2 lesions incorporate an additional stable osseous lesion of the middle column. Wedge compression fractures of the C type are mechanically and neurologically unstable three-column lesions producing cord compression by way of dislocated fragments of the dorso-cranial vertebral body, which compromises the spinal canal. C1 fractures are like B fractures in the degree of severity of the anterior and posterior column lesions.(ABSTRACT TRUNCATED AT 250 WORDS)