Selective imaging parameters and a newly created scoring scheme were found to correlate with disc degeneration as determined in a morphological manner. Surprisingly, radiographic parameters were able to distinguish different stages of degeneration, whereas MRI could only detect advanced stages of disc degeneration. We conclude that X-rays may remain a cost-effective, non-invasive in vivo-grading method to detect early disc degeneration, and, combined with MRI, correlate best with morphological and biochemical assessment of disc degeneration.

A high indirect correlation between the density of openings in the osseous endplate (particularly of the size of the capillary buds) and the morphologic degeneration grade of the disc support the hypothesis that occlusion of these openings may deprive the cells of nutrients, leading to insufficient maintenance of the extracellular matrix and disc degeneration.

V ertebroplasty, which is the percutaneous injection of bone cement into vertebral bodies has recently been used to treat painful osteoporotic compression fractures. Early clinical results have been encouraging, but very little is known about the consequences of augmentation with cement for the adjacent, non-augmented level. We therefore measured the overall failure, strength and structural stiffness of paired osteoporotic two-vertebra functional spine units (FSUs). One FSU of each pair was augmented with polymethyl-methacrylate bone cement in the caudal vertebra, while the other served as an untreated control. Compared with the controls, the ultimate failure load for FSUs treated by injection of cement was lower. The geometric mean treated/untreated ratio of failure load was 0.81, with 95% confidence limits from 0.70 to 0.92, (p < 0.01). There was no significant difference in overall FSU stiffness. For treated FSUs, there was a trend towards lower failure loads with increased filling with cement (r 2 = 0.262, p = 0.13). The current practice of maximum filling with cement to restore the stiffness and strength of a vertebral body may provoke fractures in adjacent, non-augmented vertebrae. Further investigation is required to determine an optimal protocol for augmentation.

IntroductionOsteoporosis is a disease characterized by low bone mass, which leads to increased susceptibility to fractures. It is a common condition in the elderly, affecting predominantly women over the age of 65 [2]. The spine is the most common site of fracture in patients with osteoporosis. In the United States, 25% of women over the age of 70 and 50% of women over the age of 80 show evidence of vertebral fractures, the majority of which occur in the midthoracic region and the thoracolumbar junction [16,20]. The potential sequelae include disabling pain, vertebral collapse, and progressive loss of physiologic spinal alignment [22]. Declines in physical function and changes in appearance contribute to social isolation and loss of self-esteem, thus impairing quality of life. Significant neurological compromise due to spontaneous fracture of osteoporotic vertebrae has been described [12,19]. The morbidity associated with osteoporosis and vertebral fractures represents an enormous socio-economic cost [2].Abstract Recent clinical trials have reported favorable early results for transpedicular vertebral cement reinforcement of osteoporotic vertebral insufficiencies. There is, however, a lack of basic data on the application, safety and biomechanical efficacy of materials such as polymethylmethacrylate (PMMA) and calciumphospate (CaP) cements. The present study analyzed 33 vertebral pairs from five human cadaver spines. Thirty-nine vertebrae were osteoporotic (bone mineral density <0.75 g/cm 2 ), 27 showed nearly normal values. The cranial vertebra of each pair was augmented with either PMMA (Palacos E-Flow) or experimental brushite cement (EBC), with the caudal vertebra as a control. PMMA and EBC were easy to inject, and vertebral fillings of 20-50% were achieved. The maximal possible filling was inversely correlated to the bone mineral density (BMD) values. Cement extrusion into the spinal canal was observed in 12% of cases.All specimens were subjected to axial compression tests in a displacement-controlled mode. From loaddisplacement curves, the stiffness, S, and the maximal force before failure, F max, were determined. Compared with the native control vertebrae, a statistically significant increase in vertebral stiffness and F max was observed by the augmentation. With PMMA the stiffness increased by 174% (P=0.018) and F max by 195% (P=0.001); the corresponding augmentation with EBC was 120% (P=0.03) and 113% (P=0.002). The lower the initial BMD, the more pronounced was the augmentation effect. Both PMMA and EBC augmentation reliably and significantly raised the stiffness and maximal tolerable force until failure in osteoporotic vertebral bodies. In nonporotic specimens, no significant increase was achieved.