Influence of Screw Length and Cement Position Within the Injured Vertebra on Fixation Strength in Short-Segment Fixation of Osteoporotic Thoracolumbar Burst Fractures.

OBJECTIVE

The prevalence of osteoporotic vertebral fractures has increased with aging populations, necessitating effective treatments such as percutaneous kyphoplasty combined with posterior screw fixation. However, biomechanical research on the effects of using short screws on fixation stability and bone stress or on the impact of bone cement bonding to screws on structural strength is lacking. This study aimed to optimize short-segment fixation strategies for osteoporotic thoracolumbar burst fractures by analyzing the biomechanical effects of pedicle screw length and bone-cement augmentation.

METHODS

Four models of the thoracolumbar spine were established using computed tomography data of a female volunteer: 1) short screws in the injured vertebra without contact with the bone cement, 2) long screws without contact with the bone cement, 3) long screws in contact with the bone cement, and 4) long screws without the bone cement. The 4 fixation models were simulated under physiological loads. The range of motion, implant stress, and segmental stability were assessed.

RESULTS

The 3 groups containing the bone cement exhibited similar performances in terms of stability and stress distribution, whereas the group without the bone cement exhibited a poorer biomechanical performance. Incorporation of the bone cement enhanced the biomechanical properties of the structure, and short screws in the injured vertebra without contact with the bone cement did not significantly compromise the biomechanical performance.

CONCLUSIONS

Short screws in injured vertebrae without contact with the bone cement can achieve satisfactory stability and stress distribution. It is feasible to implant short screws in the injured vertebrae, reduce the number of bilaterally injured vertebrae, and inject bone cement through the non-pedicle approach during the surgical procedure, which simplifies the surgical process.