Effect of vertebroplasty on the compressive strength of vertebral bodies

Background context Percutaneous vertebroplasty has been used successfully for many years in the treatment of painful compressive vertebral fractures due to osteoporosis. Purpose To compare the effect of vertebroplasty on the compressive strength of unfractured vertebral bodies. Study design Biomechanical study on cadaveric thoracic vertebrae. Methods Forty vertebral bodies from four cadaveric thoracic spines were used for this experiment. Before testing, each thoracic spine was submitted to bone density testing and radiographic evaluation to rule out any obvious fractures. Under image intensification, 6 mL of a mixture of polymethylmethacrylate (PMMA) with barium (8 g of barium/40 g of PMMA) was injected into every other vertebral body of each spine specimen. After vertebroplasty, all soft tissues were dissected from the spine, and the vertebral bodies were separated and potted for mechanical testing. Testing to failure was performed using a combination of axial compression and anterior flexion moments. Two pneumatic cylinders applied anterior and posterior loads at a distance ratio of 4:3 relative to the anterior vertebral body wall, whereas two additional cylinders applied lateral loads, each at a constant rate of 200 N/s. Results The average failure loads for nonvertebroplasty specimens was 6724.02±3291.70 N, whereas the specimens injected with PMMA failed at an average compressive force of 5770.50±2133.72 N. No statistically significant difference in failure loads could be detected between intact specimens and those that had undergone vertebroplasty. Conclusions Under these specific loading conditions, no significant increase in compressive strength of the vertebral bodies could be documented. This suggests that some caution should be applied to the concept of "prophylactic" vertebroplasty in patients at risk for fracture

Non-purulent low-grade infection as cause of pain following shoulder surgery: preliminary results

Low-grade infection was systematically searched for in all revision shoulder surgeries by harvesting tissue samples. Ten consecutive patients were identified with a non-purulent low-grade infection of the shoulder. All of these patients suffered from pain and eight were stiff. Preoperative aspiration in eight patients yielded bacterial growth in only one case. Serum C-reactive protein levels were normal in seven out of 10 cases. Propionibacterium acnes was identified in seven, coagulase-negative Staphylococcus in two and Staphylococcus saccharolyticus in one case. The delay between harvesting the tissue samples and detection of bacterial growth averaged eight days (range, 2-17). After debridement and antibiotic treatment for a mean of 4.5 months, tissue samples were repeatedly harvested in nine patients due to persistent pain. The infection was microbiologically eradicated in six out of nine cases that had a repeated biopsy. However, nine out of 10 patients continued to suffer from moderate to severe pain. Low-grade infection of the shoulder can be a cause of persistent pain and stiffness. The results of antibiotic treatment are disappointing. Further studies are necessary to analyse this difficult pathology