Feasibility study of using viscoplastic bone cement for vertebroplasty: an in vivo clinical trial and in vitro cadaveric biomechanical examination.

STUDY

DESIGN

An in vivo clinical trial, and an in vitro cadaveric biomechanical and micromorphologic analysis.

OBJECTIVE

To find the feasibility of using viscoplastic bone cement for vertebroplasty.

SUMMARY OF BACKGROUND DATA: Vertebroplasty involved in bone cement reinforcement of fractured vertebra has shown promising clinical results. The most frequently observed complication of vertebroplasty is the cement leakage during surgery. Many methods were proposed and were successful at reducing the risk of leakage, such as creating a void within vertebra to reduce the injection pressure, increasing the cement viscosity to reduce the cement infiltration, etc. Nevertheless, a more cost-effective and safer surgery method is still the goal for many spine surgeons and researchers.

METHODS

To deliver the viscoplastic bone cement into the vertebra, a unipedicular tract and a void in the vertebra was created using a curette. The viscoplastic bone cement was then delivered into the void piece by piece and tamped for compactness with a blunt end tool. For the in vitro biomechanical test, 7 thoracic vertebrae were used. The intact specimens were compressed to lose 25% of its intact height, and then augmented with viscoplastic bone cement. Postaugmentation CT scanning was taken to examine the cement distribution, leakage path, and cement filling ratio within the vertebra. Postaugmentation compression test was conducted to examine the vertebral strength and stiffness, and then compared with the intact ones. Finally, the vertebrae were cut into slices for micromorphologic analysis.

RESULTS

The 6 in vivo clinical trials were all successfully operated with significant pain relief and showed no leakage during and after the surgery. The in vitro biomechanical test showed the cement augmentation significantly increased the vertebral strength (pre 3164 (229) N vs. post 3905 (484) N, P < 0.003), but tentatively decreased the vertebral stiffness (pre 1074 (74) N/mm vs. post 801 (370) N/mm, P = 0.081). The postaugmentation CT scanning showed the cement was well confined within the vertebra and the cement filling ratio was 21% (ranged from 15% to 29%). The depth that the viscoplastic bone cement infiltrated into the cancellous bone was 3.5 (0.6) mm, which is less than the depth [8.3 (2.2) mm, P < 0.001] of standard viscous bone cement vertebroplasty.

CONCLUSION

Vertebroplasty using viscoplastic bone cement is clinically feasible and can effectively improve the vertebral strength and reduce the cement infiltration depth. The risk of cement leakage can also be decreased by using viscoplastic bone cement.