Vertebral fractures over the metal structure in patients with osteoporosis. Can we prevent these injuries?

Thematic justification Compression stress fractures of the vertebrae at the upper border with a metal structure are a serious problem, especially in extensive stabilization and in patients with osteoporosis. Nowadays, there is a lack of information on prevention of the fracture of the vertebrae adjacent to the metal structure. Purpose Compare experimentally the efficiency of cemented vertebroplasty and laminar band fixation of the cranial vertebra adjacent to the TPF level for prevention of fractures in osteoporosis. Study design Biomechanical cadaver study. Materials and methods We used the cadaver material obtained from females in the age from 66 to 81 years. The extension of the blocks withdrawn was from Th10 to L4 (7 vertebrae). L1 fracture was simulated in all the blocks by its mechanical destruction. A total of 15 blocks were studied divided into 3 groups of five units each: group 1 - controls (cemented TPF of Th12-L2); group 2 - cemented TPF of Th12-L2 + Th11laminar fixation with the «Universal Clamp»; group 3 - cemented TPF of Th12-L2 and preventive vertebroplasty of Th11 and L3. We used the axial load with a universal servo-hydraulic testing machine «Walter + bay ag» LFV-10-T50 (Switzerland). Compression was carried out until graphic signs of fracture were displayed. We took X-rays of blocks before and after the study. Results The control group revealed the appearance of vertebral fractures just above the metal structure (Th11). The first graphic signs of fracture were detected in the range of 0.78-0.94 kN (mean 0.86 ± 0.13784). The group with laminar fixation using the «Universal Clamp» revealed fractures of Th10 and Th11. The first graphic oscillations corresponding to a fracture were detected in the range of 1.12-1.48 kN (mean 1.21 ± 0.385227). The group with preventive vertebroplasty of Th11 and L3 revealed fractured vertebrae adjacent to the vertebroplasty (Th10). In this case, the first graphic oscillations corresponding to a fracture were detected in the range of 1.78-2.05 kN (mean 1.898 ± 0.222441). Conclusion The overlying vertebra is at increased risk of fracture when transpedicular fixation is used. The use of laminar fixation with the «Universal Clamp» does not prevent vertebral fracture over the pedicle system (Th11) but provides an increase of resistance to the vertebral fracture by 1.5 times. Preventive vertebroplasty of overlying vertebra is an effective way to prevent a pathological fracture (Th11), and also increases the resistance of the overlying (Th10) vertebra to fracture by 2-2.5 times.