A Biomechanical Study on Cortical Bone Trajectory Screw Fixation Augmented With Cement in Osteoporotic Spines

Abstract

Study Design A biomechanical study. Objective To evaluate the efficacy and feasibility of cement-augmented cortical bone trajectory (CBT) screw fixation. Methods Forty-nine CBT screws were inserted into lumbar vertebrae guided by three-dimensionally printed templates, and then injected with 0, .5, or 1.0 mL of polymethylmethacrylate. The screw placement accuracy, cement dispersion, and cement leakage rate were evaluated radiologically. Biomechanical tests were performed to measure the axial pull-out strength and torque value. Results Overall, 83.67% of the screws were inserted without pedicle perforation. In the 1.0 mL group, cement dispersed into the pedicle zone and formed a concentrated mass more often than in the .5 mL group, but not significantly more often (P > .05). The total cement leakage rate was 18.75%. Compared with the control group, the torque value was slightly higher in the .5 mL group (P = .735) and significantly higher in the 1.0 mL group (P = .026). However, there was no significant difference between the .5 and 1.0 mL groups (P = .431). The maximal pull-out force (Fmax) was increased by 52.85% and 72.73% in the .5 and 1.0 mL groups, respectively, compared with the control group (P < .05). However, the difference was not significant between the 2 cemented groups (P = .985). Conclusions Cement augmentation is a useful method for increasing CBT screw stability in osteoporotic spines. The cement injection volume is recommended to be 1 mL for each screw, and the cement should disperse into the vertebral body than the pedicle zones.

A Novel Calcium Phosphate–Based Nanocomposite for Augmentation of Cortical Bone Trajectory Screw Fixation

“…In a biomechanical study, we had demonstrated that PMMA augmentation is capable of increasing CBT screw stability, 29 and in previous studies on the augmentation of cannulated pedicle screws, CPN demonstrated biomechanical strength similar to that of PMMA. 27 , 28 In this study, we tried to apply the CPN for CBT screw augmentation to integrate the advantages of both the novel nanomaterial and the unique trajectory fixation system.…”

“…To further enhance the anchorage of CBT screws in the spine with reduced bone stock, we conducted a biomechanical study on PMMA-augmented CBT screws. 29 According to our results, PMMA augmentation is a useful method for increasing CBT screw stability, and the cement injection volume is recommended to be 1 mL for each screw. In the current study, we also showed that the cemented screws had significantly higher biomechanical strength than the nonaugmented screws, which further verified the feasibility and effectiveness of this combined technique.…”

“…Because the inclusion of nanomaterials can effectively supplement the deficiency of existing cement, a reinforced but injectable nanocomposite consisting of the self-curing bioabsorbable CPC with a nanoscale starch network was designed. [26][27][28] In a biomechanical study, we had demonstrated that PMMA augmentation is capable of increasing CBT screw stability, 29 and in previous studies on the augmentation of cannulated pedicle screws, CPN demonstrated biomechanical strength similar to that of PMMA. 27,28 In this study, we tried to apply the CPN for CBT screw augmentation to integrate the advantages of both the novel nanomaterial and the unique trajectory fixation system.…”

“…On the axial view of CT scans, the morphology of the distributed cement was described as a concentrated (C) type, in which the cement was concentrated around the screw in a kind of round mass, or a scattered (S) type, where the injected cement was randomly scattered, spotted, or linearly distributed around the screw with some radiolucent space in the cement. 29 The radiological evaluation of cement-augmented CBT screws was shown in Figure 2 .

Figure 2 Radiological evaluation of cement-augmented cortical bone trajectory (CBT) screws.

…”