Effects of cement augmentation on the mechanical stability of multilevel spine after vertebral compression fracture

A Deep Learning-Based Model for Classifying Osteoporotic Lumbar Vertebral Fractures on Radiographs: A Retrospective Model Development and Validation Study

Early diagnosis and initiation of treatment for fresh osteoporotic lumbar vertebral fractures (OLVF) are crucial. Magnetic resonance imaging (MRI) is generally performed to differentiate between fresh and old OLVF. However, MRIs can be intolerable for patients with severe back pain. Furthermore, it is difficult to perform in an emergency. MRI should therefore only be performed in appropriately selected patients with a high suspicion of fresh fractures. As radiography is the first-choice imaging examination for the diagnosis of OLVF, improving screening accuracy with radiographs will optimize the decision of whether an MRI is necessary. This study aimed to develop a method to automatically classify lumbar vertebrae (LV) conditions such as normal, old, or fresh OLVF using deep learning methods with radiography. A total of 3481 LV images for training, validation, and testing and 662 LV images for external validation were collected. Visual evaluation by two radiologists determined the ground truth of LV diagnoses. Three convolutional neural networks were ensembled. The accuracy, sensitivity, and specificity were 0.89, 0.83, and 0.92 in the test and 0.84, 0.76, and 0.89 in the external validation, respectively. The results suggest that the proposed method can contribute to the accurate automatic classification of LV conditions on radiography.

Impact of Aspiration Percutaneous Vertebroplasty in Reducing Bone Cement Leakage and Enhancing Distribution-An Ex Vivo Study in Goat Vertebrae

Osteoporosis-induced vertebral compression fracture (OVCF) occurs commonly in people over the age of 50, especially among menopausal women. Besides conservative therapy, minimally invasive percutaneous vertebroplasty (PVP) and kyphoplasty (PKP) have been widely used in clinical treatment and achieved good efficacy. However, the leakage of bone cement (CL) during vertebroplasty (PV) is a major risk that can cause (serious) complications such as compression of the spinal cord, pulmonary embolism, or even paraplegia. In this study, we introduced a new aspiration technique with standard PV procedures (APV) to ameliorate the risk of leakage with quantitative verifications of its effectiveness. APV intends to create a differential pressure to guide the direction of cement flow within the vertebrae. To test this technique, Nubian goats' ex vivo vertebral bodies (VBs) were used to simulate the PV surgical process in humans. Results show that the proposed APV has a lower leakage rate of 13% compared to the 53% of conventional PV. Additionally, the APV approach achieves more uniform cement distribution via the 9-score method with a value of 7 ± 1.30 in contrast to 4 ± 1.78 by conventional PV.

Three-dimensional surface strain analyses of simulated defect and augmented spine segments: A biomechanical cadaveric study

While several studies have investigated fracture outcomes of intact vertebrae, fracture properties in metastatically-involved and augmented vertebrae are still far from understood. Consequently, this study was aimed to use 3D digital image correlation (3D-DIC) method to investigate the failure properties of spine segments with simulated metastatic lesions, segments augmented with poly(propylene fumarate) (PPF), and compare the outcomes with intact spines. To this end, biomechanical experiments accompanied by 3D-DIC were performed on spine segments consisting of three vertebrae and two intervertebral discs (IVDs) at loading rates of 0.083 mm/s, mimicking a physiological loading condition, and 200 mm/s, mimicking an impact-type loading condition such as a fall or an accident. Full-field surface strain analysis indicated PPF augmentation reduces the superior/inferior strain when compared with the defect specimens; Presence of a defect in the middle vertebra resulted in shear band fracture pattern. Failure of the superior endplates was confirmed in several defect specimens as the superior IVDs were protruding out of defects. The augmenting PPF showed lower superior/inferior surface strain values at the fast speed as compared to the slow speed. The results of our study showed a significant increase in the fracture force from slow to fast speeds (p = 0.0246). The significance of the study was to determine the fracture properties of normal, pathological, and augmented spinal segments under physiologically-relevant loading conditions. Understanding failure properties associated with either defect (i.e., metastasis lesion) or augmented (i.e., post-treatment) spine segments could potentially provide new insights on the outcome prediction and treatment planning. Additionally, this study provides new knowledge on the effect of PPF augmentation in improving fracture properties, potentially decreasing the risk of fracture in osteoporotic and metastatic spines.

CT-based structural analyses of vertebral fractures with polymeric augmentation: A study of cadaveric three-level spine segments

Pathologic vertebral fractures due to metastasis can occur under normal physiologic activities, leading to pain and neurologic deficit. Prophylactic vertebroplasty is a technique used to augment vertebral strength and reduce the risk of fracture. Currently, no technique is available to objectively assess vertebral fracture risk in metastatically-involved vertebral bodies. The aim of the current study was to develop an image-based computational technique to estimate fracture force outcomes during bending. To this end, mechanical testing was performed on intact, simulated defect, PMMA-augmented, and PPF-augmented 3-level spine segments from both sexes under a compression/flexion-type loading condition. The augmentation performance of poly(methyl methacrylate) (PMMA) and poly(propylene fumarate) (PPF) were also evaluated and compared. Cylindrical defects were created in 3-level spine segments with attached posterior elements and ligaments. Using CT images of each segment, a rigidity analysis technique was developed and used for predicting fracture forces during bending. On average, PPF strengthened the segments by about 630 N, resulting in fracture forces similar to those observed in the intact and PMMA-augmented groups. Female spines fractured at about 1150 N smaller force than did male spines. Rigidity analysis, along with age, explained 66% variability in experimental outcomes. This number increased to 74% when vertebral size and age were added to the rigidity analysis as explanatory variables. Both PPF and PMMA similarly increased fracture strength to the level of intact specimens. The results suggest that PPF can be a suitable candidate for augmentation purposes and rigidity analysis can be a promising predicting tool for vertebral fracture forces.

Kambin triangle approach in percutaneous vertebroplasty for the treatment of osteoporotic vertebral compression fractures

The aim of this study was to evaluate the safety and efficacy of percutaneous vertebroplasty (PVP) in Kambin triangle approach for the treatment of osteoporotic vertebral compression fractures (OVCFs).Between November 2017 and September 2018, 109 patients (144 vertebral bodies) with OVCFs, with a mean age of 76.7 ± 9.9 years (55-96 years), underwent PVP in Kambin triangle approach. The time of operation, the volume of bone cement, the incidence of complication, the Visual Analog Scale (VAS) and Oswestry Disability Index (ODI) score, the position of puncture needles, and the spread of polymethylmethacrylate (PMMA) in vertebral body (VB) were recorded.All patients had been completed the operation successfully and were followed up 9.1 ± 2.9 months. The average operation time of each VB was 24.0 ± 3.5 minutes. The average volume of cement was 4.8 ± 0.6 ml. The mean VAS scores were 8.4 ± 0.7 preoperatively, 1.6 ± 0.6 at the first day postoperatively, and 1.2 ± 0.6 at the last follow-up. The mean ODI scores were 70.97 ± 7.73 preoperatively, 27.99 ± 4.12 at the first day postoperatively, and 19.65 ± 3.49 at the last follow-up. The position of puncture needles in the VB was: 119 vertebral puncture needles reached the midline, 15 were close to the midline, and 10 exceeded the midline. The spread of PMMA in the VB was: type 1 in 81 levels (56.3%), type 2 in 37 (25.7%), type 3 in 18 (12.5%), type 5 in 8 (5.5%), and no case in type 4. One case developed pneumothorax after operation. No other complications (hematoma, cement embolism, spinal cord, and nerve injury) occurred.Kambin triangle approach in PVP, which can deliver the puncture needle to the midline of VB easily and with excellent cement distribution, is a safe and effective method.

Biomechanical evaluation of calcium phosphate-based nanocomposite versus polymethylmethacrylate cement for percutaneous kyphoplasty

BACKGROUND CONTEXT

Polymethylmethacrylate (PMMA) is the most commonly used filling material when performing percutaneous kyphoplasty (PKP) for the treatment of osteoporotic vertebral compression fractures. However, there are some inherent and unavoidable drawbacks with the clinical use of PMMA. PMMA bone cement tends to leak during injection, which can lead to injury of the spinal nerves and spinal cord. Moreover, the mechanical strength of PMMA-augmented vertebral bodies is extraordinary and this high level of mechanical strength might predispose to adjacent vertebral fractures. A novel biodegradable calcium phosphate-based nanocomposite (CPN) for PKP augmentation has recently been developed to potentially avoid these issues.

PURPOSE

By comparison with PMMA, the leakage characteristics, biomechanical properties, and dispersion of CPN were evaluated when used for PKP.

STUDY DESIGN

Biomechanical evaluation and studies on the dispersion and anti-leakage properties of CPN and PMMA cements were performed and compared using cadaveric vertebral fracture model, sheep vertebral fracture model, and simulated rigid foam model.

METHODS

Sheep vertebral bodies were decalcified by ethylenediaminetetraacetic acid disodium salt (EDTA-Na₂) to simulate osteoporosis in vitro. After compression to create wedge-shaped fractures using a self-designed fracture creation tool, human cadaveric vertebrae and decalcified sheep vertebrae were augmented by PKP. In addition, three L5 vertebral bodies from human cadavers were used in a contrast vertebroplasty (VP) augmentation experiment. Occurrence of cement leakage was observed and compared between CPN and PMMA during the process of vertebral augmentation. Open-cell rigid foam model (Sawbones#1522-507) was used to create a simulated leakage model for the evaluation of the leakage characteristics of CPN and PMMA with different viscosities. The augmentation effects of CPN and PMMA were evaluated in human cadaveric and decalcified sheep vertebral models and then compared to the results from solid rigid foam model (Sawbones#1522-23). The dispersion abilities of CPN and PMMA were evaluated via three methods as follows. The dispersion volume and dispersion ratio were calculated by three-dimensional reconstruction using human vertebral body CT scans; the ratio of cement area to injection volume was calculated from three-dimensional sections of micro-CT scans of a sheep vertebra; and the micro-CT images of cement dispersion in open-cell rigid foam model (Sawbones#1522-507) were compared between CPN and PMMA. This study was funded by the National Natural Science Foundation of China (No. 81622032, 190,000 dollars and No. 51672184, 90,600 dollars), Principal Project of Natural Science Research of Jiangsu Higher Education Institutions (No. 17KJA180011, 22,000 dollars), and Jiangsu Innovation and Entrepreneurship Program (146,000 dollars).

RESULTS

There was no significant difference in vertebral height between CPN and PMMA during PKP augmentation and both cements restored the vertebral height after augmentation. In PKP augmentation experiment, posterior wall cement leakage occurred in 75% of human vertebrae augmented with PMMA; however, no leakage occurred in human vertebrae augmented with CPN. Anterior leakage occurred in all vertebrae augmented by PMMA, while in only 75% of vertebra augmented by CPN. Furthermore, CPN and PMMA had completely different leakage patterns in the simulated rigid foam model whether administered at the same injection speed or under the same injection force, suggesting that CPN has anti-leakage characteristics. The augmentation in human cadaveric vertebrae was lower with CPN compared to PMMA (1,668±816 N vs. 2,212±813 N, p=.459, respectively), but this difference was not significant. The augmentation force in sheep vertebral bodies reached 1,393±433 N when augmented with PMMA, but 1,108±284 N when augmented with CPN. The dispersion of CPN was better, and the dispersion volume and ratio were greater, with CPN than with PMMA. Imaging of the open-cell rigid foam model showed completely different dispersion modes for CPN and PMMA. After injection, the PMMA cement formed a contracted clump in the open-cell rigid foam model. However, the CPN cement extended many antennae outward, appearing to spread to the surrounding area. The surface areas of the CPN cement blocks with different liquid-to-solid ratios were significantly larger than the surface area of the PMMA cement in the open-cell rigid foam model (p<.05).

CONCLUSIONS

CPN has anti-leakage properties, which might be related to its high viscosity and viscoplasticity. CPN had a slightly lower augmentation force than PMMA when used in cadaveric vertebrae, decalcified sheep vertebrae, and in the standard rigid foam model. However, CPN diffused more easily into cancellous bone than did PMMA and encapsulated bone tissue during the dispersion process. The excellent dispersion of CPN generated better interdigitation with cancellous bone, which may be why the augmentation effect of CPN is similar to that of PMMA.

CLINICAL SIGNIFICANCE

Biodegradable CPN is a potential alternative to PMMA cement in PKP surgery, in which CPN is likely to reduce the cement leakage during the surgery and avoid the post-surgery complications caused by excessive strengths and nondegradability of PMMA cement.

Polymethylmethacrylate distribution is associated with recompression after vertebroplasty or kyphoplasty for osteoporotic vertebral compression fractures: A retrospective study

BACKGROUND

Osteoporotic vertebral compression fracture, always accompanied with pain and height loss of vertebral body, has a significant negative impact on life quality of patients. Vertebroplasty or kyphoplasty is minimal invasive techniques to reconstruct the vertebral height and prevent further collapse of the fractured vertebrae by injecting polymethylmethacrylate into vertebral body. However, recompression of polymethylmethacrylate augmented vertebrae with significant vertebral height loss and aggressive local kyphotic was observed frequently after VP or KP. The purpose of this study was to investigate the effect of polymethylmethacrylate distribution on recompression of the vertebral body after vertebroplasty or kyphoplasty surgery for osteoporotic vertebral compression fracture.

METHODS

A total of 281 patients who were diagnosed with vertebral compression fracture (T5-L5) from June 2014 to June 2016 and underwent vertebroplasty or kyphoplasty by polymethylmethacrylate were retrospectively analyzed. The X-ray films at 1 day and 12 months after surgery were compared to evaluate the recompression of operated vertebral body. Patients were divided into those without recompression (non-recompression group) and those with recompression (recompression group). Polymethylmethacrylate distribution pattern, including location and relationship to endplates, was compared between the two groups by lateral X-ray film. Multivariate logistic regression analysis was performed to assess the potential risk factors associated with polymethylmethacrylate distribution for recompression.

RESULTS

One hundred and six (37.7%) patients experienced recompression after surgery during the follow-up period. The polymethylmethacrylate distributed in the middle of vertebral body showed significant differences between two groups. In non-recompression group, the polymethylmethacrylate in the middle portion of vertebral body were closer to endplates than that in the recompression group (upper: t = 31.41, p<0.001; lower: t = 12.19, p<0.001). The higher percentage of the height of polymethylmethacrylate in the middle portion of vertebral body indicates the lower risk of recompression (odds ratio [OR]<0.01, p<0.001). The recompression group and non-recompression group showed significant difference in "contacted" polymethylmethacrylate distribution pattern (polymethylmethacrylate contacted to the both upper/lower endplates) (χ2 = 66.23, p<0.001). The vertebra with a "contacted" polymethylmethacrylate distribution pattern has lower risk of recompression (OR = 0.09, p<0.001).

CONCLUSIONS

Either more polymethylmethacrylate in the middle portion of vertebral body or "contacted" polymethylmethacrylate distribution pattern had a significantly less incidence of recompression. The findings indicated that the control of polymethylmethacrylate distribution during surgery may reduce the risks of recompression after vertebroplasty or kyphoplasty.