Sensitivity analysis of biomechanical effect in vertebral body of two different augmenters

BACKGROUND

Transvertebral Bone Graft and Augmentation (TBGA) has achieved good clinical effects in the treatment of osteoporotic vertebral compression fractures (OVCFs). This study aimed to investigate the postoperatively biomechanical effects of TBGA and compare the biomechanical sensitivity of two different augmenters: a cylindrical enhancement device (CED) and bone cement.

METHODS

Finite element models of the spine segment T11-L3 were created, including one model based on normal segment and the other three with L1 augmentation for pathological conditions. Three treatments were simulated including CED implant treatment A, CED implant treatment B, and bone cement treatment. The stress distribution and maximum displacement of the four models under different treatments were analyzed. A method of linear fitting of dummy variables was used to analyze the sensitivity of biomechanical parameters to the degree of osteoporosis (DO) and load.

FINDINGS

The reduction of stress with increasing DO in augmented and adjacent vertebral bodies under bone cement augmentation was less than that under CED augmentation. The stress of augmented vertebral body and the adjacent vertebral body was most sensitive to extension and rotation loading conditions. As DO increasing, the bone cement augmentation significantly increased the stress level on the upper and lower endplates.

INTERPRETATION

When the degree of osteoporosis increased, CED outperforms bone cement in terms of the stress reduction in augmented vertebral and adjacent vertebral, which could be beneficial for avoiding re-fracture. Using TBGA to treat OVCFs, especially with Plan B method, the condition of the pathological spine is closer to the original status in terms of the sensitivity to stress and the spinal range of motion. The TBGA treatment is sensitive to lateral bending and torsion, therefore patients should be advised to avoid high-risk motions like lateral bending and rotation.

A COMPARATIVE ANALYSIS OF THE EFFECTS OF TWO AUGMENTERS ON THE SENSITIVITY OF VERTEBRAL BIOMECHANICAL BEHAVIOR IN VERTEBROPLASTY

The treatment of osteoporotic vertebral compression fractures (OVCFS) by transvertebral bone graft and augmentation (TBGA) has achieved satisfactory clinical results, but its biomechanical effects are not clear. The purpose of this study was to investigate the biomechanical effects of TBGA and compare the biomechanical sensitivity of the augmenter used in TBGA — a cylindrical enhancement device (CED) with bone cement. The finite element (FE) model of healthy segments T11-L3 (M1) was built, and two other models with L1 augmentation (M2, M3) were established to simulate CED and bone cement treatment, respectively. The stress and displacement distribution of the three models under five physiological loads were calculated and analyzed by the FE method. Based on the results, the sensitivities of biomechanical parameters to the degree of osteoporosis (DO) and loads were analyzed by linear fitting method using dummy variables. With the increase of DO, the CED is superior to bone cement in preventing the fractures of the augmented vertebral and the adjacent vertebral under the set loading conditions. Simulating TBGA method, the model 2 with L1 reconstructed was closer to the normal T11-L3 model in terms of sensitivity of stress and displacement under different loading conditions.

CaCO3–Polymer Nanocomposite Prepared with Supercritical CO2

A novel process for generation of a CaCO3–polymer nanocomposite with a controlled three-dimensional shape was developed. Specifically, a nanocomposite with a high CaCO3 content was produced by introducing supercritical CO2 into a polymer matrix containing Ca ions. A mixture of poly(vinyl alcohol), Ca acetate, and poly(acrylic acid) was poured into a mold, the mold was placed in an autoclave, and CO2 was introduced to precipitate CaCO3 within the polymer matrix. Laser Raman spectroscopy and transmission electron microscopy showed that this process produced a nanocomposite containing highly dispersed CaCO3 (aragonite) nanoparticles. The flexural strength of the nanocomposite was larger than the flexural strengths of limestone and CaCO3 produced by hydrothermal hot pressing. The use of supercritical CO2 facilitated CO2 dissolution, which resulted in rapid precipitation of CaCO3 in the polymer matrix. The above-described process has potential utility for fixation of CO2.

New Technology for Surgical Treatment of Osteoporotic Vertebral Compression Fractures: The Transvertebral Bone Graft and Fixation

OBJECTIVE

To introduce an innovative surgical technique, transvertebral bone graft and augmentation (TBGA), to and evaluate its clinical efficacy in treating osteoporotic vertebral body compression fractures (VCFs), with balloon kyphoplasty (BKP) as a control.

METHODS

A total of 81 patients with a single-level osteoporotic VCF underwent TBGA (n = 38) or BKP (n = 43) at our hospital between October 2012 and January 2015. The average duration of follow-up period was 27.9 months. The patients were evaluated with plain radiography, computed tomography, and magnetic resonance imaging preoperatively, immediately postoperatively, at 3- and 6-month follow-ups, and every 6 months thereafter. Clinical status was assessed using the Oswestry Disability Index (ODI) and a visual analog scale (VAS). In addition, parameters of anterior vertebral body height (AVBH), kyphosis angle (KA), adjacent segment degeneration (ASD), and complications were also compared between the 2 groups.

RESULTS

Significant clinical improvements in ODI, VAS scores, AVBH, and KA were seen in both the TBGA and BKP groups after surgery (P < 0.05). However, the differences in improvements in ODI and VAS between the TBGA and BKP groups were not statistically significant (P > 0.05). The improvements in AVBH and KA were significantly better in the TBGA group (P < 0.05). Furthermore, the rates of ASD and complications were significantly lower in the TBGA group during the follow-up period (P < 0.05).

CONCLUSIONS

TBGA is an effective and safe surgical technique that appears to be a promising alternative to BKP for the surgical treatment of osteoporotic VCFs.

Transvertebral Bone Graft and Augmentation Versus Posterior Spinal Instrumentation in the Treatment of Simple Thoracolumbar Compression Fractures

OBJECTIVE

This retrospective cohort study was performed to investigate clinical efficacy of TBGA compared with pedicle screw fixation (PSF).

METHODS

A total of 86 eligible patients with single-level simple thoracolumbar compression fracture (TLCF) received TBGA (n = 41) or PSF (n = 45) from January 2013 to July 2015. The patients were evaluated using plain radiography, computed tomography, and magnetic resonance imaging preoperatively. The radiologic examinations were performed at each time point postoperatively. Clinical status was assessed using the Oswestry Disability Index (ODI) and visual analog scale (VAS) scores. In addition, anterior vertebral body height (AVBH), kyphosis angle (KA), radiologic adjacent segment pathology (RASP), and complication rates were also compared between the 2 groups. The average follow-up period of patients was 26.1 months.

RESULTS

Significant clinical improvements in ODI, VAS, AVBH, and KA were achieved in both TBGA and PSF groups after surgery, respectively (P < 0.05). There was no statistical difference in improvements of ODI and VAS between the TBGA and PSF groups (P > 0.05). Similarly, improvements of AVBH and KA showed no statistical difference between the 2 groups (P > 0.05). In addition, the rates of RASP and complications in PSF group were significantly higher than the TBGA group during the follow-up period (P < 0.05).

CONCLUSIONS

TBGA can achieve satisfactory clinical effects in treatment of simple TLCF. TBGA involves shorter operative time, less blood loss, lower RASP, and lower complication rates and could be more suitable for the surgical treatment of simple TLCF.