Experimental Substantiation of the Possibility of Prevention of Vertebral Fractures Related to the Level of Transpedicular Fixation
Authors: Basankin Igor , Tahmazyan Karapet , Afaunov Asker , Ptashnikov Dmitry , Ponkina Olga , Shapovalov Vladimir 
Published: May 2015

Introduction

Compression stress fractures of the vertebrae adjacent to the fixed steel structure is a serious problem. Especially, it is observed in patients with osteoporosis. The biomechanical studies proving any method of preventing such complications are not found in the literature. The objective was the recognition of the possible ways of preventing adjacent vertebral fractures in the conditions of the cement transpedicular osteosynthesis while having osteoporotic.

Materials and Methods

The postmortem graft of women aged 66 to 81 years was used. The length of the blocks withdrawn from Th10 to L4. A total of 10 blocks were removed and then they were equally divided into two groups. In both the groups, the fracture of L1 vertebra was simulated by its mechanical destruction. We implanted transpedicular system Th12 to L2 with augmentation. Besides the described interventions nothing more was done in the control group. In the exploring group, the bone cement was injected to the vertebrae adjacent to the transpedicular system (Th11 and L3) in a volume 20 to 25% of the vertebra (7–8 mL). Tests were held with the help of compressive load along the longitudinal axis of the spine on the universal servohydraulic testing machine “Walter + bay ag” LFV-10to T50 (Switzerland). The strength of the vertical mechanical impact on the unit the graphical display of the fracture was investigated. After performing a mechanical test, all blocks were exposed to X-ray examination to visualize the fracture.

Results

Destabilization of the system and vertebral fractures in which screws were implanted with cement (Th12 and L2) was not observed in any case in both the groups. In the control group of the experimental units (without prophylactic vertebroplasty), fractures of the overlying vertebra over the pedicle system (Th11) were diagnosed. The first graphic indications of fracture were defined in the range 0.78 to 0.94 (average, 0.84 ± 0.39831) kN. Further strengthening of the load led to the formation of deformation and obvious destruction of Th11 vertebra. These changes were recorded within 1.24 to 1.6 (average, 1.47 ± 0.39831) kN. In the exploring group of blocks (with a prophylactic vertebroplasty up and underlying vertebrae), fractures of these vertebrae (Th11 and L3) were not found. In this case, the first graphical oscillations corresponding to the fracture were detected in the range of 1.78 to 2.05 (average, 1.91 ± 0.40566) kN. The more marked graphic changes were detected within 2.12 to 2.88 (average, 2.51 ± 0.40566) kN. After the testing X-ray examination, the fracture of the proximal end of the block vertebra (Th10) was revealed. Adjacent caudal vertebrae (L3 and L4) were not destroyed in any case, in both the groups.

Conclusion

Although using the PSF with augmentation at increased risk of fracture there is the overlying vertebra. Prophylactic vertebroplasty of the overlying vertebra is an effective way to prevent its pathological fracture. Vertebral fracture of the cranial level of preventive vertebroplasty occurs when the average load is 2 to 2.5 times higher than the fracture of adjacent vertebrae TPV without prophylactic vertebroplasty. Prophylactic vertebroplasty of the underlying vertebra is impractical because of its low risk of fracture.