Three-dimensional finite element analysis of optimal distribution model of vertebroplasty

Space between bone cement and bony endplate can trigger higher incidence of augmented vertebral collapse: An in-silico study

BACKGROUND

The pathogenesis of postoperative complications in patients with osteoporotic vertebral compressive fractures (OVCFs) undergoing percutaneous vertebroplasty (PVP) is multifaceted, with local biomechanical deterioration playing a pivotal role. Specifically, the disparity in stiffness between the bone cement and osteoporotic cancellous bone can precipitate interfacial stress concentrations, potentially leading to cement-augmented vertebral body collapse and clinical symptom recurrence. This study focuses on the biomechanical implications of the space between the bone cement and bony endplate (BEP), hypothesizing that this interface may be a critical locus for stress concentration and subsequent vertebral failure.

METHODS

Leveraging a validated numerical model from our previous study, we examined the biomechanical impact of the cement-BEP interface in the L2 vertebral body post-PVP, simulated OVCF and PVP and constructed three distinct models: one with direct bone cement contact with both cranial and caudal BEPs, one with contact only with the caudal BEPs and one without contact with either BEP. Moreover, we assessed stress distribution across cranial and caudal BEPs under various loading conditions to describe the biomechanical outcomes associated with each model.

RESULTS

A consistent trend was observed across all models: the interfaces between the bone cement and cancellous bone exhibited higher stress values under the majority of loading conditions compared to models with direct cement-BEP contact. The most significant difference was observed in the flexion loading condition compared to the mode with direct contact between BEP and cement. The maximum stress in models without direct contact increased by at least 30%.

CONCLUSIONS

Our study reveals the biomechanical significance of interfacial stiffness differences at the cement-BEP junction, which can exacerbate local stress concentrations and predispose to augmented vertebral collapse. We recommend the strategic distribution of bone cement to encompass a broader contact area with the BEP for preventing biomechanical failure and subsequent vertebral collapse.

Biomechanical Study of Porcine Osteoporotic Vertebral Compression Fracture Model Strengthened by Trajectory-Adjustable Bone Cement Filling Device

OBJECTIVE

To establish a porcine osteoporotic vertebral compression fracture model and compare the impact of unilateral vertebroplasty using trajectory-adjustable bone cement filling device to traditional surgical tools on vertebral biomechanics.

METHODS

Twenty-four fresh adult porcine vertebrae were used to establish an osteoporotic vertebral compression fracture model. The specimens were divided into 4 groups (A, B, C, and D), each consisting of 6 vertebrae. Group A served as the control group without vertebral augmentation (percutaneous vertebroplasty [PVP]). Patients in Group B underwent unilateral PVP using conventional surgical tools, while patients in Group C underwent bilateral PVP using the same tools. In Group D, patients underwent unilateral PVP with a trajectory-adjustable bone cement filling device. Postoperative X-ray examinations were performed to assess cement distribution and leakage. The compressive stiffness and strength of each spinal unit were evaluated using an electronic mechanical testing machine.

RESULTS

In Groups B, C, and D, the percentages of total cement distribution area were 32.83 ± 3.64%, 45.73 ± 2.27%, and 47.43 ± 3.51%, respectively. The values were significantly greater in Groups C and D than in Group B (P < 0.05), but there was no significant difference between Groups C and D (P > 0.05). The stiffness after vertebral augmentation in Groups B, C, and D was 1.04 ± 0.23 kN/mm, 1.11 ± 0.16 KN/mm, and 1.15 ± 0.13 KN/mm, respectively, which were significantly greater than that in Group A (0.46 ± 0.06 kN/mm; P < 0.05). The ultimate compressive strengths in Groups B, C, and D were 2.53 ± 0.21 MPa, 4.09 ± 0.30 MPa, and 3.99 ± 0.29 MPa, respectively, all surpassing Group A's strength of 1.41 ± 0.31 MPa. Additionally, both Groups C and D demonstrated significantly greater ultimate compressive strengths than Group B did (P < 0.05).

CONCLUSIONS

A trajectory-adjustable bone cement filling device was proven to be an effective approach for unilateral vertebroplasty, restoring the biomechanical properties of fractured vertebrae. Compared to traditional surgical tools, this approach is superior to unilateral puncture and yields outcomes comparable to those of bilateral puncture. Additionally, the device ensures a centrally symmetrical distribution pattern of bone cement, leading to improved morphology.

Three‑dimensional finite element analysis: Anatomical splint fixation for Colles fractures

With the rapid development of digital research in clinical orthopedics, the efficacy and safety of splint fixation can be better evaluated through biomechanical analysis based on a three-dimensional (3D) finite element model. It is essential to address the current gap in understanding the biomechanical implications of anatomical splint fixation for Colles fractures. By employing advanced 3D finite element analysis, the present study aimed to provide a comprehensive evaluation, offering valuable insights that can contribute to enhancing the effectiveness of anatomical splint fixation in the clinical management of Colles fractures. The 3D finite element models of the forearm and hand were constructed using Mimics 15.0 according to data from computed tomography of a patient with a Colles fracture. After the validity of the model was verified, the corresponding material properties of the models were adjusted to simulate a Colles fracture. Subsequently, the reduction functions, such as radial inclination and ulnar deviation, of the simulated fracture were completed and the mechanical changes of the tissues surrounding the fracture were calculated. Anatomical splints were then placed on the surfaces of the 3D finite element models of Colles fractures at various positions to analyze the changes in the stress cloud diagram, such as for the soft tissue and anatomical splints. In the present study, the constructed 3D finite element models were accurate and valid. The maximum stress of the anatomical splints and soft tissues was 2.346 and 0.106 MPa in pronation, 1.780 and 0.069 MPa in median rotation and 3.045 and 0.057 MPa in supination, respectively. Splint stress reached the highest level in supination and soft tissue stress achieved the highest level in pronation. The peak of splint stress occurred during supination, which contrasts to the peak of soft tissue stress observed in pronation, suggesting splint fixation median rotation can effectively avoid compression of the local soft tissue.

Correlation Study Between Bone Cement Distribution and Adjacent Vertebral Fractures After Percutaneous Vertebroplasty

OBJECTIVE

We investigated the correlation between bone cement distribution and adjacent vertebral fractures (AVFs) after percutaneous vertebroplasty (PVP).

METHODS

We retrospectively analyzed patients who underwent single-segment PVP for osteoporotic compression fractures in our hospital from January 2016 to January 2021 and divided the patients into 2 groups, A and B, on the basis of the criterion of whether there were AVFs of the operated vertebrae within 1 year after surgery. We compared the general data of the 2 groups, assessed the ability of 3 simple X-ray-based evaluation methods to predict the occurrence of AVF within 1 year after surgery and derived a simple and accurate evaluation method.

RESULTS

A total of 570 patients were included in this study: 511 patients in group A and 59 patients in group B. There were no statistical differences in the general data such as age, gender, and fracture site between the 2 groups. The posterior-anterior (PA), lateral (LAT), and PA and LAT methods showed receiver operating characteristic curve (ROC) predicted postoperative AVF of 0.611, 0.691, and 0.714, respectively. The difference between the area under curve (AUC) of the PA method and LAT method was statistically significant (P = 0.0307), the difference between the AUC of PA method and PA and LAT method was statistically significant (P < 0.001), and the difference between the AUC of LAT method and PA and LAT method was not statistically significant (P = 0.3308).There was no statistical difference between the 2 groups of patients with PA method point of 1 and statistically different between patients with points of 2 and 3. There was statistical difference in points of 1, 2 and 3 in the LAT method between the 2 groups. There was a positive correlation between cement distribution scores and AVF by linear regression analysis of the 3 evaluation methods.

CONCLUSIONS

The 3 evaluation methods reliably predict AVF after PVP, with the LAT method, PA and LAT method being more predictive than the PA method, but the LAT method is simpler, with bone cement being widely distributed after crossing the midline in the PA method and contact with the upper and lower end plates in the LAT method being a risk factor for AVF.

Effect of different bone cement distributions in percutaneous kyphoplasty on clinical outcomes for osteoporotic vertebral compression fractures: A retrospective study

Osteoporotic fractures and their complications are becoming increasingly harmful to the elderly. This study aimed to evaluate the clinical results of connected or unconnected bilateral cement after bilateral percutaneous kyphoplasty (PKP) in patients with osteoporotic vertebral compression fractures (OVCF). The clinical data of 217 patients with single-segment OVCF were retrospectively collected. Patients were allocated into 2 groups according to the bilateral bone cement in the vertebrae was connected or unconnected after surgery. The surgery-related indexes of the 2 groups were compared, including operation time; bone cement injection volume; contact situation between bone cement and the upper and lower endplates of the vertebral body; visual analogue scale (VAS) scores before surgery, 1 week and 1 year after surgery; Oswestry disability index (ODI) before surgery, 1 week and 1 year after surgery; local kyphosis angle (LKA) before surgery, 1 week and 1 year after surgery; postoperative vertebral body height at 1 week and 1 year after surgery; vertebral body height restoration rate (HRR) at 1 week and 1 year after surgery. The follow-up results of all patients were recorded. The postoperative VAS, ODI, vertebral body height, LKA and other indexes of the 2 groups were significantly improved compared with those before the operation (P < .05), and there was no significant difference between the 2 groups (P > .05). At the same time, there were no significant difference in vertebral body HRR and bone cement leakage rate between the 2 groups (P > .05). X-ray examination showed that 21 of 217 patients (21/217, 9.8%) had a refracture of the injured vertebral body, including 16 cases (16/121, 13.2%) in the unconnected group and 5 cases (5/96, 5.2%) in the connected group (P < .05). Adjacent vertebrae fractures occurred in 25 cases (25/217, 11.5%), while 19 cases (19/121, 15.7%) were in the unconnected group and 6 cases (6/96, 6.3%) were in the connected group (P < .05). PKP has a good therapeutic effect on OVCF no matter whether the bilateral bone cement is connected or not. However, if the bilateral cement inside the vertebra was connected, the risk of recollapse of the injured vertebrae and the new fracture of adjacent vertebrae could be reduced.

A computational analysis of a novel therapeutic approach combining an advanced medicinal therapeutic device and a fracture fixation assembly for the treatment of osteoporotic fractures: Effects of physiological loading, interface conditions, and fracture

The occurrence of periprosthetic femoral fractures (PFF) has increased in people with osteoporosis due to decreased bone density, poor bone quality, and stress shielding from prosthetic implants. PFF treatment in the elderly is a genuine concern for orthopaedic surgeons as no effective solution currently exists. Therefore, the goal of this study was to determine whether the design of a novel advanced medicinal therapeutic device (AMTD) manufactured from a polymeric blend in combination with a fracture fixation plate in the femur is capable of withstanding physiological loads without failure during the bone regenerative process. This was achieved by developing a finite element (FE) model of the AMTD together with a fracture fixation assembly, and a femur with an implanted femoral stem. The response of both normal and osteoporotic bone was investigated by implementing their respective material properties in the model. Physiological loading simulating the peak load during standing, walking, and stair climbing was investigated. The results showed that the fixation assembly was the prime load bearing component for this configuration of devices. Within the fixation assembly, the bone screws were found to have the highest stresses in the fixation assembly for all the loading conditions. Whereas the stresses within the AMTD were significantly below the maximum yield strength of the device's polymeric blend material. Furthermore, this study also investigated the performance of different fixation assembly materials and found Ti-6Al-4V to be the optimal material choice from those included in this study.

Clinical Evaluation of Unilateral Vertebroplasty for OVCF

Objective

To investigate the clinical evaluation of unilateral vertebroplasty for OVCF.

Methods

A retrospective analysis was performed on 60 patients treated with PVP from January 2020 to December 2021. Patients were divided into two groups according to the treatment method, 30 patients in the PVP group received PVP and 30 patients in the PCVP group received PCVP. The VAS score, ODI score, bone cement dosage, and leakage were compared between the two groups preoperatively, immediately postoperatively, and 7 and 30 days postoperatively.

Results

VAS scores in the PCVP and PVP groups before, immediately after, and 7 days after surgery were P > 0.05, and the difference was not statistically significant; ODI score in group 1 before surgery was not statistically significant (P > 0.05); bone cement injection volume in the PVP group was significantly higher than that in the PCVP group (P < 0.05), and the difference was statistically significant; the difference in bone cement leakage between the two groups was not statistically significant (P > 0.05).

Conclusion

Under the same puncture conditions, the PCVP group used the method of injection while retreating to achieve a better bone cement dispersion effect by using less bone cement and achieving uniform dispersion of bone cement. It can relieve the patients' back pain and improve the back function.

A finite element analysis on different bone cement forms and injection volumes injected into lumbar vertebral body in percutaneous kyphoplasty

Background

To investigate the stress changes between different bone cement forms and injection volumes in adjacent vertebrae after percutaneous kyphoplasty (PKP) by establishing a three-dimensional finite element model of osteoporosis.

Methods

A male healthy volunteer was selected. CT of scans L1 to L3 vertebrae were imported into Mimics 21.0 software.The vertebral model of osteoporosiswas established based on previous literature reference. The models were divided into three groups: unilateral, bilateral integration and bilateral separation groups, with each group injecting 2 ml, 4,ml and 6 ml of bone cement, respectively. In all models, a vertical compressive load of 500 N, anterior flexion/posterior extension, left/right bending, and left/right rotation were applied with a moment of 7.5 N/m, of which 85% was applied to the anterior mid-column and 15% to the posterior column. The stress changes between adjacent vertebrae under different conditions were calculated.

Results

After percutaneous kyphoplasty was applied to the L2 vertebral body, some differences can be found between the effects of different cement injection volumes and cement morphology on adjacent structures. There was no major difference between the groups when the bone cement injection volume was 2 ml. When the amount of bone cement injected was 4 ml, the bone cement morphology of the bilateral integration group (BIG) produced less stress between adjacent vertebral bodies. The minimum stress was 14.95 MPa in the L3 vertebral body in posterior extension. Whereas the stress levels on adjacent intervertebral structures, BIG shaped bone cement shows some superiority. In addition, the adjacent vertebrae and intervertebral structures are subjected to less stress during left and right rotation.

Conclusions

The present finite element study suggested that bilateral integration bone cement is a suitable form of cement injection, and when the injection volume is 4 ml, reduces stress on adjacent segments by approximately 15% while maintaining the stability of the injected vertebral body.

Clinical Outcomes of Fracture Haemorrhage Aspiration for Percutaneous Vertebroplasty in Treating Osteoporotic Vertebral Compression Fractures

Background

A retrospective study aimed to introduce a new method for improving the diffusion degree of bone cement and to observe its clinical efficacy in percutaneous vertebroplasty treating osteoporotic vertebral compression fractures (OVCFs).

Methods

From January 2019 to March 2020, a total of 83 patients were enrolled and reviewed. The patients were divided into two groups according to the operation method. The clinical and radiographic parameters were recorded and compared between these two groups. Those who received percutaneous vertebroplasty with haemorrhage aspiration were recorded as group A (n=42). In group A, the haemorrhage in the vertebral fracture was aspirated compared with conventional percutaneous vertebroplasty. Patients who underwent conventional percutaneous vertebroplasty were classified as group B (n=41).

Results

Visual analogue scale (VAS) values and Oswestry Disability Index (ODI) scores showed no significant difference between the two groups preoperatively, postoperatively or at the final follow-up (FU) (P>0.05). The intraoperative VAS score (bone cement injection) in group A was significantly lower than that in group B (3.83±0.79 vs 5.44±1.32, P < 0.01). The local kyphotic angle (LKA) (final follow-up), LKA loss, fractured vertebral anterior height loss (FVAHL) and anterior vertebral height loss ratio (AVHLR) were significantly lower in group A than in group B. The anterior vertebral height ratio (AVHR) at the final FU in group A was higher than that in group B (P=0.013). The distribution of bone cement was significantly different (P=0.034). By analysing the distribution pattern of bone cement, it was found that the values of LKA loss, FVAHL and AVHLR were superior in the type A bone cement distribution to those in types B and C.

Conclusion

Compared with traditional surgical methods, bone haemorrhage aspiration could improve the diffusion degree of bone cement and reduce the height loss and deformity of injured vertebrae. This method provides a feasible new scheme for improving the dispersion of bone cement.

Finite Element Method for the Evaluation of the Human Spine: A Literature Overview

The finite element method (FEM) represents a computer simulation method, originally used in civil engineering, which dates back to the early 1940s. Applications of FEM have also been used in numerous medical areas and in orthopedic surgery. Computing technology has improved over the years and as a result, more complex problems, such as those involving the spine, can be analyzed. The spine is a complex anatomical structure that maintains the erect posture and supports considerable loads. Applications of FEM in the spine have contributed to the understanding of bone biomechanics, both in healthy and abnormal conditions, such as scoliosis, fractures (trauma), degenerative disc disease and osteoporosis. However, since FEM is only a digital simulation of the real condition, it will never exactly simulate in vivo results. In particular, when it concerns biomechanics, there are many features that are difficult to represent in a FEM. More FEM studies and spine research are required in order to examine interpersonal spine stiffness, young spine biomechanics and model accuracy. In the future, patient-specific models will be used for better patient evaluations as well as for better pre- and inter-operative planning.

Finite element analysis of wedge and biconcave deformity in four different height restoration after augmentation of osteoporotic vertebral compression fractures

Purpose

Biomechanical comparison of wedge and biconcave deformity of different height restoration after augmentation of osteoporotic vertebral compression fractures was analyzed by three-dimensional finite element analysis (FEA).

Methods

Three-dimensional finite element model (FEM) of T11-L2 segment was constructed from CT scan of elderly osteoporosis patient. The von Mises stresses of vertebrae, intervertebral disc, facet joints, displacement, and range of motion (ROM) of wedge and biconcave deformity were compared at four different heights (Genant 0–3 grade) after T12 vertebral augmentation.

Results

In wedge deformity, the stress of T12 decreased as the vertebral height in neutral position, flexion, extension, and left axial rotation, whereas increased sharply in bending at Genant 0; L1 and L2 decreased in all positions excluding flexion of L2, and T11 increased in neutral position, flexion, extension, and right axial rotation at Genant 0. No significant changes in biconcave deformity. The stress of T11-T12, T12-L1, and L1-L2 intervertebral disc gradually increased or decreased under other positions in wedge fracture, whereas L1-L2 no significant change in biconcave fracture. The utmost overall facet joint stress is at Genant 3, whereas there is no significant change under the same position in biconcave fracture. The displacement and ROM of the wedge fracture had ups and downs, while a decline in all positions excluding extension in biconcave fracture.

Conclusions

The vertebral restoration height after augmentation to Genant 0 affects the von Mises stress, displacement, and ROM in wedge deformity, which may increase the risk of fracture, whereas restored or not in biconcave deformity.