Prevention Of Osteoporotic Vertebral Fractures Research Articles

Vertebral Endplate Fractures: An Indicator of the Abnormal Forces Generated in the Spine After Vertebroplasty

Vertebroplasty alters spinal biomechanics and may lead to incident vertebral fractures. The endplate localization of prevalent and incident fractures was evaluated in 86 patients. In the absence of vertebroplasty, superior endplate fractures predominate. After the procedure, inferior endplate fractures are disproportionately common in adjacent vertebrae immediately above the treated level, potentially supporting a causative relationship between vertebroplasty and incident fractures. To determine retrospectively whether new-onset fractures after vertebroplasty tend to cluster in the endplate immediately adjacent to the cemented vertebra. Institutional Review Board approval and patient consent for use the use of medical records were obtained for this study. We performed a retrospective review of patients with new (incident) vertebral fractures after vertebroplasty. The median age for these patients was 72.5 years, and 58 (67.4%) were women. Fractures were diagnosed on the basis of MRI or bone scan and were catalogued based on their location within the vertebral body (superior endplate, inferior endplate, or holo-vertebral). Chi(2) and generalized estimating equation (GEE) analyses were used to compare the distribution of fracture subtypes among pre-existing (prevalent) and incident fractures. The patients had 313 prevalent osteoporotic vertebral fractures and were treated at 137 vertebral levels. Among prevalent fractures, superior endplate fractures predominated (57% superior, 11% inferior; p < 0.0001). After vertebroplasty, 186 incident fractures developed in these 86 patients. Seventy-seven (41%) of these incident fractures occurred adjacent to treated vertebrae. Nonadjacent, incident fractures, like prevalent fractures, occurred predominantly along superior endplate. Incident fractures immediately above treated levels, however, localized disproportionately to the inferior endplate (30% superior, 57% inferior; p < 0.0001). There are an increased number of inferior endplate fractures of the vertebral body immediately cephalad to the treated level.

In vivo BMP-7 (OP-1) enhancement of osteoporotic vertebral bodies in an ovine model

Background context Prevention of osteoporotic vertebral fractures could help at-risk individuals avoid the pain and morbidity associated with these fractures. Currently, patients with osteoporosis are treated with systemic medications to reduce fracture risk. Although effective, these therapies do not eliminate fractures and also tend to have a gradual time-dependent effect on fracture risk. The mechanism of action of the bone morphogenetic protein (BMP) family theoretically makes these molecules candidates for rapidly enhancing local bone structure. Study design An in vivo study analyzing the effects of BMP-7 (osteogenic protein 1 [OP-1]) treatment on osteopenic ovine vertebral architecture and biomechanics. Purpose We tested the hypothesis that local injection of OP-1 into osteopenic ovine vertebrae will improve bone mass and trabecular distribution, thereby reducing bone fragility and fracture risk. We specifically evaluated compressive biomechanics and morphology of osteopenic ovine vertebral bodies 6 months after local OP-1 treatment. Study design In vivo animal study. Methods Skeletally mature sheep (n=24) underwent ovariectomy and were placed on low cation relative to anion diet. These interventions reduce bone density and induce skeletal fragility. After 6 months, sheep were randomly assigned to six treatment groups based on OP-1 dose (370 mg or 0 mg) and carrier with 4 animals/treatment group. Carriers A and B were poly- l-glycolic acid (PLGA) biospheres with different release kinetics (B allowing sustained BMP release); Carrier C was carboxymethylcellulose. After creating an 8-mm-diameter defect in the midvertebral body, sheep underwent intravertebral body implantation at two nonadjacent levels. Animals were euthanized 6 months after implantation and bone mineral density (BMD), biomechanics, and histomorphometry were assessed. Two-way analysis of variance was used to determine effects of OP-1 (α=0.05). Results An 81.9%, 333.2%, and 39.9% increase in stiffness was seen for OP-1 treated vertebra with Carriers A, B, and C respectively. Although these effects did not reach statistical significance, trends toward improvement were evident. Histology showed varied degrees of bony healing in the injection sites. Histomorphometrically, OP-1 treated vertebrae showed improvements in percent bone of up to 38% and star volume of up to 55% (with Carrier B). Improvements in whole vertebral body BMD were not detected for any treatment. Conclusion In this study, local OP-1 treatment showed a positive trend in improving mechanical strength and histomorphometric parameters of osteopenic vertebra, despite the absence of consistent change in BMD. Controlled slow release of OP-1 using PLGA microspheres appeared to be the most effective method of protein delivery. In conclusion, we feel that the pilot data suggest that the use of OP-1 in the treatment of vertebral osteoporosis in an attempt to enhance bone strength merits further study.

Prevention of vertebral fractures by strontium ranelate in postmenopausal women with osteoporosis.

The antifracture efficacy of strontium ranelate, a compound with a novel mechanism of action on bone, has been assessed in two large, randomized, controlled trials conducted in postmenopausal women. Strontium ranelate was given at a daily dose of 2 g, and all women received calcium and vitamin D supplements. In women with established osteoporosis there was a 41% reduction in vertebral fractures over 3 years' treatment [relative risk (RR) 0.59; 95% confidence interval (CI) 0.48-0.73; P<0.001]; significant reductions were also seen after only 1 year of treatment. The beneficial effect was also seen for clinical vertebral fractures: over 3 years there was a significant reduction in new clinical vertebral fractures (RR 0.62; 95% CI 0.47-0.83; P<0.001); this reduction was also observed during the first year of treatment (RR 0.48; 95% CI 0.29-0.80; P=0.003). Over the 3-year treatment period significantly fewer patients had height loss and fewer patients reported new or worsening back pain in the treated group than in the control group. These results demonstrate that strontium ranelate is a new therapeutic option in the prevention of osteoporotic vertebral fractures in postmenopausal women.

Determination of the modulus of elasticity of bone material by an acoustical approach at the forearm distinguishes women with and without vertebral fractures independent of bone mineral density.

The modulus of elasticity is a parameter characterizing fracture stability of bone independent of bone mineral density. Measurement of acoustical properties of the forearm by determination of the resonant frequency of the ulna in longitudinal direction as a function of sound transmission velocity after adjustment of the measuring result by ulna length yields information about the modulus of elasticity. It was the aim of this study to investigate whether this parameter may distinguish between subjects with and without vertebral fractures independent of bone mineral density. Fifty females (61.1 +/- 9.1 years) were enrolled into the study, 25 with, and 25 age-matched without prevalent osteoporotic vertebral fracture(s). Especially low bone mineral density was not considered an exclusion criteria for enrollment into the control group. Resonant frequency of the ulna multiplied by ulna length was significantly lower in the group with prevalent fractures (53.6 +/- 6.8 m/s versus 56.8 +/- 5.2 m/s) after adjustment for age and after additional adjustment for forearm bone mineral density. Linear regression analysis showed complete independence of the acoustical parameter from bone mineral density. This study demonstrates that the modulus of elasticity of bone material is an independent risk factor for osteoporotic fractures. Acoustical measurement at the forearm by analyzing the resonant frequency of the ulna and correcting it by ulna length as geometrical parameter is capable of determining the modulus of elasticity in vivo.