New vertebral fracture after vertebroplasty

Biomechanical comparison between unilateral and bilateral percutaneous vertebroplasty for osteoporotic vertebral compression fractures: A finite element analysis

Background and objective: The osteoporotic vertebral compression fracture (OVCF) has an incidence of 7.8/1000 person-years at 55–65 years. At 75 years or older, the incidence increases to 19.6/1000 person-years in females and 5.2–9.3/1000 person-years in males. To solve this problem, percutaneous vertebroplasty (PVP) was developed in recent years and has been widely used in clinical practice to treat OVCF. Are the clinical effects of unilateral percutaneous vertebroplasty (UPVP) and bilateral percutaneous vertebroplasty (BPVP) the same? The purpose of this study was to compare biomechanical differences between UPVP and BPVP using finite element analysis.

Materials and methods: The heterogeneous assignment finite element (FE) model of T11-L1 was constructed and validated. A compression fracture of the vertebral body was performed at T12. UPVP and BPVP were simulated by the difference in the distribution of bone cement in T12. Stress distributions and maximum von Mises stresses of vertebrae and intervertebral discs were compared. The rate of change of maximum displacement between UPVP and BPVP was evaluated.

Results: There were no obvious high-stress concentration regions on the anterior and middle columns of the T12 vertebral body in BPVP. Compared with UPVP, the maximum stress on T11 in BPVP was lower under left/right lateral bending, and the maximum stress on L1 was lower under all loading conditions. For the T12-L1 intervertebral disc, the maximum stress of BPVP was less than that of UPVP. The maximum displacement of T12 after BPVP was less than that after UPVP under the six loading conditions.

Conclusion: BPVP could balance the stress of the vertebral body, reduce the maximum stress of the intervertebral disc, and offer advantages in terms of stability compared with UPVP. In summary, BPVP could reduce the incidence of postoperative complications and provide promising clinical effects for patients.

Subsequent fractures after vertebroplasty in osteoporotic vertebral fractures: a meta-analysis

Percutaneous vertebroplasty (VP) provides substantial benefit to patients with painful osteoporotic vertebral compression fractures (OVCF). However, the reoccurrence of vertebral fracture after VP is a major concern. The purpose of this study is to conduct a meta-analysis on the incidence of subsequent fractures after VP in patients with OVCF. PubMed and EMBASE were searched. In addition, we scrutinized the reference list of all relevant articles to supplement the database search. We included original articles reporting on new fracture rates after VP in OVCF patients. Subsequent fracture rates were pooled across studies using a random-effects meta-analysis. Thirty-nine studies with a total of 8047 participants from 12 countries were included in this meta-analysis. Patients' age ranged from 64.2 to 94.6 years (reported by 31 studies). The median follow-up was 21 months (36 studies). Pooled estimate for subsequent fractures after VP was 23.4% (95% CI, 19.8-27.2%; I² = 93.0%, p < 0.01). New fractures after VP in 54.6% of cases occurred in the vertebral bodies adjacent to the treated vertebra (95% CI, 49.0-60.1%; I² = 66.0%, p < 0.01). A significant proportion of patients undergoing VP for OVCF experience new fractures after treatment, most of which are developed in the vertebral bodies adjacent to the treated vertebra.

Early Adjacent Vertebral Fractures after Balloon Kyphoplasty for Osteoporotic Vertebral Compression Fractures

Study Design

Retrospective cohort study.

Purpose

To evaluate the incidence and risk factors for early adjacent vertebral fractures following balloon kyphoplasty (KP).

Overview of Literature

KP is a safe and effective treatment for pain alleviation in patients with osteoporotic vertebral compression fractures (OVCF). However, some studies have reported that the risk of newly developed fractures increases at the adjacent vertebra after KP.

Methods

Total 123 consecutive patients with painful OVCF who underwent KP were enrolled from January 2009 to June 2016. Early adjacent vertebral fractures were defined as new fractures that had developed within 3 months after surgery. Sex, age, body mass index (BMI), bone mineral density (BMD), vertebral height, kyphotic angle, Visual Analog Scale score, cement amount, and leakage were evaluated as risk factors for adjacent vertebral fractures. Only cement leakage into the disc space was included in this study.

Results

Early adjacent vertebral fractures were identified in 20 (16.2%) of the 123 patients. The mean time to diagnosis of fractures was 1.7±0.7 months after KP. The average patient age was 78.0±0.7 years, average BMI was 23.06±3.83 kg/m², and mean BMD was −3.61±1.22 g/m². Cement leakage was present in 16 patients, and fractures developed in 11 (68.7%). In contrast, fractures developed in nine patients (8.2%) without cement leakage. There were no significant differences in terms of age, BMI, BMD, kyphotic angle, or vertebral body height ratio between the fracture and control groups.

Conclusions

Cement leakage into the disc increased the risk of early adjacent vertebral fractures after balloon KP.

How are adjacent spinal levels affected by vertebral fracture and by vertebroplasty? A biomechanical study on cadaveric spines

BACKGROUND CONTEXT

Spinal injuries and surgery may have important effects on neighboring spinal levels, but previous investigations of adjacent-level biomechanics have produced conflicting results. We use "stress profilometry" and noncontact strain measurements to investigate thoroughly this long-standing problem.

PURPOSE

This study aimed to determine how vertebral fracture and vertebroplasty affect compressive load-sharing and vertebral deformations at adjacent spinal levels.

STUDY DESIGN

We conducted mechanical experiments on cadaver spines.

METHODS

Twenty-eight cadaveric spine specimens, comprising three thoracolumbar vertebrae and the intervening discs and ligaments, were dissected from fourteen cadavers aged 67-92 years. A needle-mounted pressure transducer was used to measure the distribution of compressive stress across the anteroposterior diameter of both intervertebral discs. "Stress profiles" were analyzed to quantify intradiscal pressure (IDP) and concentrations of compressive stress in the anterior and posterior annulus. Summation of stresses over discrete areas yielded the compressive force acting on the anterior and posterior halves of each vertebral body, and the compressive force resisted by the neural arch. Creep deformations of vertebral bodies under load were measured using an optical MacReflex system. All measurements were repeated following compressive injury to one of the three vertebrae, and again after the injury had been treated by vertebroplasty. The study was funded by a grant from Action Medical Research, UK ($143,230). Authors of this study have no conflicts of interest to disclose.

RESULTS

Injury usually involved endplate fracture, often combined with deformation of the anterior cortex, so that the affected vertebral body developed slight anterior wedging. Injury reduced IDP at the affected level, to an average 47% of pre-fracture values (p<.001), and transferred compressive load-bearing from nucleus to annulus, and also from disc to neural arch. Similar but reduced effects were seen at adjacent (non-fractured) levels, where mean IDP was reduced to 73% of baseline values (p<.001). Vertebroplasty partially reversed these changes, increasing mean IDP to 76% and 81% of baseline values at fractured and adjacent levels, respectively. Injury also increased creep deformation of the vertebral body under load, especially in the anterior region where a 14-fold increase was observed at the fractured level and a threefold increase was observed at the adjacent level. Vertebroplasty also reversed these changes, reducing deformation of the anterior vertebral body (compared with post-fracture values) by 62% at the fractured level, and by 52% at the adjacent level.

CONCLUSIONS

Vertebral fracture adversely affects compressive load-sharing and increases vertebral deformations at both fractured and adjacent levels. All effects can be partially reversed by vertebroplasty.

Biomechanical Analysis of Intervertebral Cement Extravasation in Vertebral Motion Segments

Kyphoplasty is a therapeutic option for pain relief in the setting of compression fractures. Cement extravasation into adjacent disks is a common occurrence. The biomechanical and clinical consequences of cement in the disks currently are unknown. This study investigated the biomechanical effects of cement extravasation into the intervertebral disk in a human cadaveric model. Seven thoracolumbar and lumbar embalmed human cadaveric motion segments were evaluated in axial rotation, right and left lateral bending, and flexion and extension. Stiffness was calculated at baseline and following injection of 1 mL of cement into the intervertebral disk. There was a 13.4% (P=.041) increase in stiffness in axial rotation compared with preinjection motion segments. No significant difference was observed in lateral bending or flexion and extension. In this model, cement extravasation into the disk space increased stiffness in axial rotation. [Orthopedics. 2017; 40(2):e300-e304.].

Risk factors for new vertebral compression fractures after vertebroplasty: a meta-analysis

BACKGROUND

The risk factors for new vertebral compression fractures (VCFs) after vertebroplasty are unclear. The aim of this meta-analysis was to identify potential risk factors.

METHODS

A systematic electronic literature search was performed using the following databases: PubMed, Embase and Cochrane Library; the databases were searched from the earliest available records in 1966 to May 2015. Pooled odds ratios (ORs) or standardized mean differences (SMDs) with 95% confidence intervals (CIs) were calculated using random- or fixed-effects models. The Newcastle-Ottawa scale was used to evaluate the methodological quality of the studies, and Stata 11.0 was used to analyse the data.

RESULTS

The primary factors that were associated with new fractures after vertebroplasty were low bone mineral density (SMD -0.375; 95% CI -0.579 to -0.171), steroid usage (OR 2.632; 95% CI 1.399 to 4.950) and the presence of multiple treated vertebrae (OR 2.027; 95% CI 1.442 to 2.851). The data did not support that age, sex, body mass index, non-steroidal anti-inflammatory drug usage, vacuum cleft, thoracolumbar junction, cement volume, kyphosis correction, or intradiscal cement leakage could lead to infection after vertebroplasty.

CONCLUSIONS

The present analysis demonstrated that low bone mineral density, the presence of multiple treated vertebrae and a history of steroid usage were associated with the new VCFs after vertebroplasty. Patients with these factors should be informed of the potential increased risk.

Risk factors of new symptomatic vertebral compression fractures in osteoporotic patients undergone percutaneous vertebroplasty

PURPOSE

This study evaluated the risk factors of new vertebral compression fractures (VCFs) following percutaneous vertebroplasty (PVP).

METHODS

From June 2005 to January 2011, patients with osteoporotic VCFs (OVCFs) who were treated with PVP and met this study's inclusion criteria were retrospectively reviewed. Observed parameters were age, sex, bone mineral density, body mass index, amount of bone cement, cement leakage into the disk, preoperative kyphosis, preoperative degree of anterior vertebral compression, preoperative degree of middle vertebral compression, kyphosis correction, anterior vertebral height restoration, middle vertebral height restoration, and number of initial symptomatic fractures (levels treated). The data were analyzed by univariate and multivariate analysis for the emergence of new fractures after PVP to determine related risk factors.

RESULTS

A total of 182 patients met the inclusion criteria. There were 155 female and 27 male patients with a mean age of 69.7 years (range 49-91 years). The follow-up period was 24-50 months (average 26.4 months). A total of 294 VCFs among 182 patients were observed, 28 new VCFs occurred in 21 patients (21/182, 11.5 %) during the follow-up period. Statistical analysis indicated that higher BMI (P = 0.004) and a greater number of initial symptomatic fractures (P = 0.017) were significantly associated with new VCFs after PVP. It is the most obvious that the risk of new fractures increased 2.518-fold (95 % CI 1.176-5.395), when the number of initial VCFs increased by one level.

CONCLUSIONS

The incidence of new symptomatic VCFs after PVP was higher in osteoporotic patients with initial multiple-level fractures.

Risk Factors of New Adjacent Compression Fracture after Percutaneous Vertebroplasty: Effectiveness of Bisphosphonate in Osteoporotic or Osteopenic Elderly Patients

OBJECTIVE

The purpose of this study is to investigate the incidence of new compression and to analyze factors that influence the fractures in adjacent levels after percutaneous vertebroplasty (PVP).

METHODS

This retrospective study examined 206 patients who had undergone PVP for single level osteoporotic or osteopenic compression fractures during the last seven years in our department. After PVP, the patients were observed for at least over one year, and 29 patients showed new additional compression fractures in adjacent levels. One hundred seventy seven patients who did not show additional compression fractures were analyzed as the control group. Statistical comparisons were performed between the groups, in terms of age, gender, bone mineral density, whether bisphosphonate (BPP) was treated, preoperative kyphosis, preoperative wedge angle, change in wedge angle, amount of bone cement, existence of intradiscal bone cement leakage, and initial fracture levels.

RESULTS

The statistically significant factors that influence new compression fractures in adjacent levels after PVP were as follows: being female, initial thoracolumbar junction fracture, preoperative large kyphotic, preoperative large wedge angle, change in wedge angle, administration of BPP in osteopenia group, and intradiscal cement leakage.

CONCLUSION

This study identified many factors that influence newly developed compression fractures in adjacent levels after PVP. Interestingly, the administration of BPP in osteopenia group had positive influence on new fractures in this study. Therefore, we recommend early administration of BPP to patients with osteopenia.

Effect of vertebroplasty on the compressive strength of vertebral bodies

BACKGROUND CONTEXT

Percutaneous vertebroplasty has been used successfully for many years in the treatment of painful compressive vertebral fractures due to osteoporosis.

PURPOSE

To compare the effect of vertebroplasty on the compressive strength of unfractured vertebral bodies.

STUDY DESIGN

Biomechanical study on cadaveric thoracic vertebrae.

METHODS

Forty vertebral bodies from four cadaveric thoracic spines were used for this experiment. Before testing, each thoracic spine was submitted to bone density testing and radiographic evaluation to rule out any obvious fractures. Under image intensification, 6 mL of a mixture of polymethylmethacrylate (PMMA) with barium (8 g of barium/40 g of PMMA) was injected into every other vertebral body of each spine specimen. After vertebroplasty, all soft tissues were dissected from the spine, and the vertebral bodies were separated and potted for mechanical testing. Testing to failure was performed using a combination of axial compression and anterior flexion moments. Two pneumatic cylinders applied anterior and posterior loads at a distance ratio of 4:3 relative to the anterior vertebral body wall, whereas two additional cylinders applied lateral loads, each at a constant rate of 200 N/s.

RESULTS

The average failure loads for nonvertebroplasty specimens was 6724.02 ± 3291.70 N, whereas the specimens injected with PMMA failed at an average compressive force of 5770.50 ± 2133.72 N. No statistically significant difference in failure loads could be detected between intact specimens and those that had undergone vertebroplasty.

CONCLUSIONS

Under these specific loading conditions, no significant increase in compressive strength of the vertebral bodies could be documented. This suggests that some caution should be applied to the concept of "prophylactic" vertebroplasty in patients at risk for fracture.

Evaluation and management of vertebral compression fractures

Compression fractures affect many individuals worldwide. An estimated 1.5 million vertebral compression fractures occur every year in the US. They are common in elderly populations, and 25% of postmenopausal women are affected by a compression fracture during their lifetime. Although these fractures rarely require hospital admission, they have the potential to cause significant disability and morbidity, often causing incapacitating back pain for many months. This review provides information on the pathogenesis and pathophysiology of compression fractures, as well as clinical manifestations and treatment options. Among the available treatment options, kyphoplasty and percutaneous vertebroplasty are two minimally invasive techniques to alleviate pain and correct the sagittal imbalance of the spine.

Risk factors for new vertebral compression fractures after percutaneous vertebroplasty: qualitative evidence synthesized from a systematic review

STUDY DESIGN

Methodological systematic review.

OBJECTIVE

To identify the risk factors for new vertebral compression fractures (VCFs) in patients after percutaneous vertebroplasty (PVP) and to grade the evidence according to the quality of included studies.

SUMMARY OF BACKGROUND DATA

PVP is an effective procedure for the treatment of VCFs. A major concern after PVP in patients with osteoporosis is the occurrence of new VCFs in the untreated vertebrae. The risk factors for new VCFs after PVP reported thus far remain controversial. These risk factors have neither been well identified or summarized. This systematic review was performed to identify the risk factors for new VCFs after PVP.

METHODS

Noninterventional studies evaluating the risk factors for new VCFs of patients with osteoporosis after PVP were searched in MEDLINE, EMBASE, ScienceDirect, and OVID databases (all up to November 2012). Only observational studies with eligible data were included. Quality of included studies was assessed by a modified quality assessment tool, which was previously designed for observational study. The effects of studies were combined with the study quality score using a model of best-evidence synthesis.

RESULTS

Twenty-four observational studies involving 3789 patients were included. These articles were published between 2004 and 2012. According to the quality assessment criteria for included studies, 8 studies were deemed as high-quality studies, 6 as moderate-quality studies, and 10 as low-quality studies. There were strong evidences of 3 risk factors, including lower bone mineral density, lower body mass index, intradiscal cement leakage, and vertebral height restoration. We also identified 6 moderate-evidence factors including lower body mass index, number of pre-existing vertebral fractures, thoracolumbar junction in initial VCFs, cement distraction, older age, and number of treated vertebrae. Thirteen factors were classified into the limited-evidence risk factors.

CONCLUSION

Although there is no conclusive evidence for new VCFs of patients with osteoporosis after PVP procedure, these data provide evidence to guide the surgeon and develop optimal preventions for new VCFs after PVP. Special attention should be paid to the 3 strong-evidence risk factors. Further studies were still required to evaluate the effects of the earlier mentioned risk factors.

LEVEL OF EVIDENCE

2.

Hypothermic manipulation of bone cement can extend the handling time during vertebroplasty

Background

Polymethylmethacrylate (PMMA) is commonly used for clinical applications. However, the short handling time increases the probability of a surgeon missing the crucial period in which the cement maintains its ideal viscosity for a successful injection. The aim of this article was to illustrate the effects a reduction in temperature would have on the cement handling time during percutaneous vertebroplasty.

Methods

The injectability of bone cement was assessed using a cement compressor. By twisting the compressor, the piston transmits its axial load to the plunger, which then pumps the bone cement out. The experiments were categorized based on the different types of hypothermic manipulation that were used. In group I (room temperature, sham group), the syringes were kept at 22°C after mixing the bone cement. In group 2 (precooling the bone cement and the container), the PMMA powder and liquid, as well as the beaker, spatula, and syringe, were stored in the refrigerator (4°C) overnight before mixing. In group 3 (ice bath cooling), the syringes were immediately submerged in ice water after mixing the bone cement at room temperature.

Results

The average liquid time, paste time, and handling time were 5.1 ± 0.7, 3.4 ± 0.3, and 8.5 ± 0.8 min, respectively, for group 1; 9.4 ± 1.1, 5.8 ± 0.5, and 15.2 ± 1.2 min, respectively, for group 2; and 83.8 ± 5.2, 28.8 ± 6.9, and 112.5 ± 11.3 min, respectively, for group 3. The liquid and paste times could be increased through different cooling methods. In addition, the liquid time (i.e. waiting time) for ice bath cooling was longer than for that of the precooling method (p < 0.05).

Conclusions

Both precooling (i.e. lowering the initial temperature) and ice bath cooling (i.e. lowering the surrounding temperature) can effectively slow polymerization. Precooling is easy for clinical applications, while ice bath cooling might be more suitable for multiple-level vertebroplasty. Clinicians can take advantage of the improved injectability without any increased cost.

Subsequent vertebral fracture after vertebroplasty: incidence and analysis of risk factors

STUDY DESIGN

A retrospective review and analysis of consecutive patients who underwent single-level vertebroplasty at our institute between March 2002 and March 2006.

OBJECTIVE

To analyze the risk factors for subsequent fractures after vertebroplasty and to predict the postoperative fracture-free time and rate. The effect of bone cement volume injected was also evaluated.

SUMMARY OF BACKGROUND DATA

Previous studies of subsequent fractures after vertebroplasty showed conflicting conclusions about risk factors. The frequency of refracture also varied, ranging from 12% to 52%. Most new fractures occurred at adjacent levels, with different risk factors identified. No data were available on the effect of injected bone cement volume, and no consensus had been reached as to the optimal cement volume.

METHODS

All enrolled patients were treated with single-level vertebroplasty and followed a standardized postoperative care protocol. Data from medical records and radiographs were collected and analyzed. Variables included patient constitutional factors, radiographic parameters, and volume of injected bone cement.

RESULTS

A total of 166 patients (76 men, 90 women) with a mean age of 73.4 years were enrolled in this study. The mean follow-up time was 15.3 months. The overall refracture rate was 38%, with a mean fracture-free interval of 32 months. Both a greater volume of bone cement injected and a greater degree of vertebral height restored contributed significantly to the risk of subsequent adjacent fracture. No risk factor for subsequent remote fracture was identified. A greater volume of bone cement injected was positively correlated with deformity correction after vertebroplasty.

CONCLUSION

Most subsequent fractures occurred at the adjacent level within the first 3 months. Patient preoperative condition did not help predict refracture. Although a greater volume of bone cement injected when performing vertebroplasty contributed to the risk of subsequent adjacent fracture, it resulted in a greater improvement of kyphosis.

Correlation of kyphosis and wedge angles with outcome after percutaneous vertebroplasty: a prospective cohort study

PURPOSE

To evaluate the correlation of kyphosis and wedge angles with pain relief and functional outcome after percutaneous vertebroplasty (PV).

METHODS

15 men and 19 women aged 41 to 85 (mean, 62) years who presented with osteoporotic wedge compression fractures of the dorsolumbar spine below T5 and had failed conservative treatment were included. Patients were assessed before and one year after PV. Kyphosis and wedge angles were measured on standardised radiographs. Pain and function were assessed using the visual analogue scale (VAS) score and the Ronald Morris Disability Questionnaire (RMDQ) score, respectively. Patients were dichotomised based on their preoperative kyphosis (≤ 10 vs. >10 degrees) and wedge angles (≤ 7 vs. >7 degrees). Outcomes were classified as excellent, fair, and poor in terms of VAS scores (<3, 3-6, >6) and RMDQ scores (<8, 8-16, >16). Correlations between the kyphosis and wedge angles and VAS and RMDQ scores were assessed.

RESULTS

VAS and RMDQ scores correlated positively with the kyphosis and wedge angles; the highest correlation was between the VAS score and kyphosis angle (r=0.93). A significantly greater proportion of excellent outcomes (in terms of RMDQ and VAS scores) were noted in patients with preoperative kyphosis and wedge angles of ≤ 10 and ≤ 7 degrees, respectively.

CONCLUSION

PV is a viable treatment for vertebral compression fractures with regard to pain relief and improvement of function. Preoperative kyphosis and wedge angles were predictive of post-PV outcomes in terms of VAS and RMDQ scores.

The proper volume and distribution of cement augmentation on percutaneous vertebroplasty

OBJECTIVE

The purpose of this study was to determine the optimal volume of injected cement and its distribution when used to treat vertebral compression fractures, and to identify factors related to subsequent vertebral fractures.

METHODS

A retrospective analysis of newly developing vertebral fractures after percutaneous vertebroplasty was done. The inclusion criteria were that the fracture was a single first onset fracture with exclusion of pathologic fractures. Forty-three patients were included in the study with a minimum follow up period of six months. Patients were dichotomized for the analysis by volume of cement, initial vertebral height loss, bone marrow density, and endplate-to-endplate cement augmentation.

RESULTS

None of the four study variables was found to be significantly associated with the occurrence of a subsequent vertebral compression fracture. In particular, and injected cement volume of more or less that 3.5 cc was not associated with occurrence (p = 0.2523). No relation was observed between initial vertebral height loss and bone marrow density (p = 0.1652, 0.2064). Furthermore, endplate-to-endplate cement augmentation was also not found to be significantly associated with a subsequent fracture (p = 0.2860) by Fisher's exact test.

CONCLUSION

Neither volume of cement, initial vertebral height loss, bone marrow density, or endplate-to-endplate cement augmentation was found to be significantly related to the occurrence of a subsequent vertebral compression fracture. Our findings suggest that as much cement as possible without causing leakage should be used.