An improved spinal injury parameter model for underbody impulsive loading scenarios

Underbody blast events such as aircraft ejection, mine blast, and helicopter crashes pose a serious threat to occupants. These impulsive excitations exert substantial axial loads on the thoracolumbar spine causing severe injuries. The Dynamic Response Index (DRI), which is commonly used as the injury parameter for underbody loading scenarios, suffers from inherent disadvantages and has been reported to underpredict the chances of injury. The main reasons are the inability of the DRI model to account for bending loads and posture of the spine. Thus, a novel lumped full spine model capable of modelling the spine in different posture along the sagittal plane is formulated. The unavailable data for the model were obtained using inverse parameter identification approach by eigenfrequency matching. Each vertebra has three degrees of freedom: axial, shear, and rotary motion to model the flexion of the spine. A new injury parameter is proposed based on the sum of compressions caused due to axial and rotary springs at each vertebral level, to account for wedge compression and burst fractures. The results indicate that the model was able to predict the motions of vertebrae under different postures of the spine according to trends in literature.

Cortical Bone Trajectory Instrumentation with Vertebroplasty for Osteoporotic Thoracolumbar Compression Fracture

BACKGROUND

Osteoporotic spinal fractures commonly occur in elderly patients with low bone mineral density. In these cases, percutaneous vertebroplasty or percutaneous kyphoplasty can provide significant pain relief and improve mobility. However, studies have reported both the recurrence of vertebral compression fractures at the index level after vertebroplasty and the development of new vertebral fractures at the adjacent level that occur without any additional trauma. Pedicle screw fixation combined with percutaneous vertebroplasty has been proposed as an effective procedure for addressing osteoporotic thoracolumbar fractures. However, in osteoporotic populations, pedicle screws can loosen, pullout, or migrate. Currently, the efficacy of cortical bone trajectory screw fixation for osteoporotic fractures remains unclear. Thus, we assessed the effects of using cortical bone trajectory instrumentation with vertebroplasty on patient outcomes.

METHOD

We retrospectively reviewed data from 12 consecutively sampled osteoporotic thoracolumbar fracture patients who underwent cortical bone trajectory instrumentation with vertebroplasty. Patients were enrolled beginning in October 2015 and were followed for >24 months.

RESULT

The average age was 74 years, and the average dual-energy x-ray absorptiometry T-score was -3.6. The average visual analog scale pain scores improved from 8 to 2.5 after surgery. The average blood loss was 36.25 mL. All patients regained ambulation and experienced reduced pain post-surgery. No recurrent fractures or instrument failures were recorded during follow-up.

CONCLUSIONS

Our findings suggest that cortical bone trajectory instrumentation combined with percutaneous vertebroplasty may be a good option for treating osteoporotic thoracolumbar fractures, as it can prevent recurrent vertebral fractures or related kyphosis in sagittal alignment.

The association between sarcopenia and osteoporotic vertebral compression refractures

Sarcopenia was reported to be significantly associated with osteoporosis. In this study, we reported for the first time that sarcopenia was an independent risk predictor of osteoporotic vertebral compression refractures (OVCRFs). Other risk factors of OVCRFs are low bone mass density T-scores, female sex, and advanced age.

INTRODUCTION

The purpose of this study was to investigate the association between osteoporotic vertebral compression refractures (OVCRFs) and sarcopenia, and to identify other risk factors of OVCRFs.

METHODS

We evaluated 237 patients with osteoporotic vertebral compression fracture who underwent percutaneous kyphoplasty (PKP) in our hospital from August 2016 to December 2017. To diagnose sarcopenia, a cross-sectional computed tomography (CT) image at the inferior aspect of the third lumbar vertebra (L3) was selected for estimating muscle mass. Grip strength was used to assess muscle strength. Possible risk factors, such as age, sex, body mass index (BMI), bone mineral density (BMD), location of the treated vertebra, anterior-posterior ratio (AP ratio) of the fractured vertebra, cement leakage, and vacuum clefts, were assessed. The multivariable analysis was used to determine the risk factors of OVCRFs.

RESULTS

During the follow-up period, OVCRFs occurred in 64 (27.0%) patients. Sarcopenia was present in 48 patients (20.3%), including 21 OVCRFs and 27 non-OVCRFs patients. Sarcopenia was significantly correlated with advanced age, lower BMI, lower BMD, and hypoalbuminemia. Compared with non-sarcopenic patients, sarcopenic patients had higher OVCRFs risk. In univariate analysis, sarcopenia (p = 0.003), female (p = 0.024), advanced age (≥ 75 years; p < 0.001), lower BMD (p < 0.001), lower BMI (p = 0.01), TL junction (vertebral levels at the thoracolumbar junction) (p = 0.01), cardiopulmonary comorbidity (p = 0.042), and hypoalbuminemia (p = 0.003) were associated with OVCRFs. Multivariable analysis revealed that sarcopenia (OR 2.271; 95% CI 1.069-4.824, p = 0.033), lower BMD (OR 1.968; 95% CI 1.350-2.868, p < 0.001), advanced age (≥ 75 years; OR 2.431; 95% CI 1.246-4.744, p = 0.009), and female sex (OR 4.666; 95% CI 1.400-15.552, p = 0.012) were independent risk predictors of OVCRFs.

CONCLUSIONS

Sarcopenia is an independent risk predictor of osteoporotic vertebral compression refractures. Other factors affecting OVCRFs are low BMD T-scores, female sex, and advanced age.

Multiple vertebral compression fractures after sleeve gastrectomy and a subsequent pregnancy: a case report

We report that a 33-year-old woman developed multiple compression fractures several years after a sleeve gastrectomy followed by pregnancy. Despite normal areal BMD values assessed by dual-energy X-ray absorptiometry and no family history of osteoporosis, the patient demonstrated low lumbar spine trabecular bone score, as well as low peripheral trabecular volumetric BMD and deterioration of trabecular microarchitecture assessed by high-resolution peripheral quantitative computed tomography. Women of reproductive age should be provided with lifestyle management targeting bone health following bariatric surgery.

Vertebroplasty versus sham procedure for painful acute osteoporotic vertebral compression fractures (VERTOS IV): randomised sham controlled clinical trial

OBJECTIVE

To assess whether percutaneous vertebroplasty results in more pain relief than a sham procedure in patients with acute osteoporotic compression fractures of the vertebral body.

DESIGN

Randomised, double blind, sham controlled clinical trial.

SETTING

Four community hospitals in the Netherlands, 2011-15.

PARTICIPANTS

180 participants requiring treatment for acute osteoporotic vertebral compression fractures were randomised to either vertebroplasty (n=91) or a sham procedure (n=89).

INTERVENTIONS

Participants received local subcutaneous lidocaine (lignocaine) and bupivacaine at each pedicle. The vertebroplasty group also received cementation, which was simulated in the sham procedure group.

MAIN OUTCOME MEASURES

Main outcome measure was mean reduction in visual analogue scale (VAS) scores at one day, one week, and one, three, six, and 12 months. Clinically significant pain relief was defined as a decrease of 1.5 points in VAS scores from baseline. Secondary outcome measures were the differences between groups for changes in the quality of life for osteoporosis and Roland-Morris disability questionnaire scores during 12 months' follow-up.

RESULTS

The mean reduction in VAS score was statistically significant in the vertebroplasty and sham procedure groups at all follow-up points after the procedure compared with baseline. The mean difference in VAS scores between groups was 0.20 (95% confidence interval -0.53 to 0.94) at baseline, -0.43 (-1.17 to 0.31) at one day, -0.11 (-0.85 to 0.63) at one week, 0.41 (-0.33 to 1.15) at one month, 0.21 (-0.54 to 0.96) at three months, 0.39 (-0.37 to 1.15) at six months, and 0.45 (-0.37 to 1.24) at 12 months. These changes in VAS scores did not, however, differ statistically significantly between the groups during 12 months' follow-up. The results for secondary outcomes were not statistically significant. Use of analgesics (non-opioids, weak opioids, strong opioids) decreased statistically significantly in both groups at all time points, with no statistically significant differences between groups. Two adverse events occurred in the vertebroplasty group: one respiratory insufficiency and one vasovagal reaction.

CONCLUSIONS

Percutaneous vertebroplasty did not result in statistically significantly greater pain relief than a sham procedure during 12 months' follow-up among patients with acute osteoporotic vertebral compression fractures.

TRIAL REGISTRATION

ClinicalTrials.gov NCT01200277.

Spatiotemporal characterization of microdamage accumulation in rat ulnae in response to uniaxial compressive fatigue loading

Repetitive fatigue loading can induce microdamage accumulation in bone matrix, which results in impaired mechanical properties and increased fracture susceptibility. However, the spatial distribution and time-variant process of microdamage accumulation in fatigue-loaded skeleton, especially for linear microcracks which are known to initiate bone remodeling, remain not fully understood. In this study, the time-varying process of the morphology and distribution of microcracks in rat ulnae subjected to uniaxial compressive fatigue loading was investigated. Right forelimbs of thirty four-month-old male Sprague-Dawley rats were subjected to one bout of cyclic ramp loading with 0.67 Hz at a normalized peak force of 0.055 N/g body weight for 6000 cycles, and the contralateral left ulnae were not loaded as the control samples. Ten rats were randomly euthanized on Days 3, 5, and 7 post fatigue loading. Our findings via two-dimensional histomorphometric measurements based on basic fuchsin staining and three-dimensional quantifications using contrast-enhanced micro-computed tomography (MicroCT) with precipitated BaSO₄ staining demonstrated that the accumulation of linear microcracks (increase in the amount of linear microcracks) on Day 5 was significantly higher than that on Day 3 and Day 7 post fatigue loading. Our histological and histomorphometric results revealed that linear microcrack density (Cr.Dn) in the tensile cortex at Days 3, 5 and 7 post fatigue loading was significantly higher than that in the compressive side, whereas linear microcrack length (Cr.Le) in the tensile cortex at Day 3 was significantly lower than that in the compressive cortex. Our findings revealed that microcrack accumulation exhibited a non-linear time-varying process at 3, 5 and 7 days post axial compressive fatigue loading (with observable peak Cr.Dn at Day 5). Our findings also revealed distinct distribution of microcrack density and morphology in rat ulnae with tensile and compressive strains, as characterized by more microcracks accumulated in tensile cortices, and longer cracks shown in compressive cortices.

Analysis of correlation between degeneration of lower lumbar paraspinal muscles and spinopelvic alignment in patients with osteoporotic vertebral compression fracture

BACKGROUND

A few studies have pointed that trunk extensors may affect the spinopelvic alignment; however, little is known about the exact association between degeneration of lower lumbar paraspinal muscles and spinopelvic parameters.

OBJECTIVE

The study aimed to analyze the relationship between degeneration of lower lumbar paraspinal muscles and spinopelvic alignment in patients with osteoporotic vertebral compression fracture (OVCF).

METHODS

Thirty-nine OVCF patients were involved in this study. All patients underwent a standing lateral radiographs of the entire spine and pelvis 6 months after kyphoplasty. Pelvic incidence, pelvic tilt, lower lumbar lordosis (LLL) were measured. On the MRI images, the cross-sectional areas of the erector spinae (ES), multifidus (MF), vertebral body and the signal intensity of ES, MF, subcutaneous fat were measured. Pearson's correlation coefficients was applied to analyze the correlation between the muscular degeneration degree (muscular atrophy and fatty infiltration) and spinopelvic parameters.

RESULTS

The fatty change degree of ES at L4 inferior endplate level was positively correlated with pelvis retroversion (r= 0.480, p< 0.05). The grade of fat infiltration of ES plus MF at L5 level was negatively related to LLL (r=-0.446, p< 0.05). The fatty change of ES at L5 level, atrophy of ES at L4 and L5 level did not correlate with pelvis back tilt. The fat infiltration of ES plus MF at L4 level, the atrophy degree of ES plus MF at L4 and L5 level had no correlation with LLL.

CONCLUSIONS

With the increase of fatty infiltration of the erector spinae, the degree of pelvis retroversion increases; the lower lumbar lordosis decreases with the increase of intramuscular adipose tissue of the erector spinae plus multifidus. The atrophy degree of the erector spinae and multifidus is not correlated with pelvis back tilt and lower lumbar lordosis.

Role of matrix behavior in compressive fracture of bovine cortical bone

In compressive fracture of dry plexiform bone, we examine the individual roles of overall mean porosity, the connectivity of the porosity network, and the elastic as well as the failure properties of the nonporous matrix, using a random spring network model (RSNM). Porosity network structure is shown to reduce the compressive strength by up to 30%. However, the load-bearing capacity increases with an increase in either of the matrix properties-the elastic modulus or the failure strain threshold. To validate the porosity-based RSNM model with available experimental data, bone-specific failure strain thresholds for the ideal matrix of similar elastic properties were estimated to be within 60% of each other. Further, we observe the avalanche size exponents to be independent of the bone-dependent parameters as well as the structure of the porosity network.

Stepwise resection of the posterior ligamentous complex for stability of a thoracolumbar compression fracture: An in vitro biomechanical investigation

To quantify the mechanical contribution of posterior ligamentous structures to the stability of thoracolumbar compression fractures.Twelve fresh human T11-L3 spinal specimens were harvested in this study. The 1/3 L1 vertebral body was resected in a wedged shape. After the preinjury had been created, the specimens were subjected to flexion-compression to create a fracture model. Resection of the ligaments was performed in a sequential manner from the bilateral facet capsule ligament (FCL), interspinous ligament, and supraspinous ligament (SSL) to the ligamentum flavum at the T12-L1 level. Then, for the intact specimen, fracture model, and ligament disruption steps, the range of motion (ROM) and neutral zone (NZ) of T12-L1 and L1-L2 were collected for each simulated movement.Sequential transection of the posterior ligamentous complex (PLC), ROM, and NZ were increased in all movements at the T12-L1 segment. In the flexion-extension (FE), the ROM and NZ demonstrated significant increases after the fracture model and resection of SSL and LF. In lateral bending (LB), the ROM increased after the fracture and removal of the LF, while the NZ showed a slight increase. In axial rotation, the fracture model and removal of the LF resulted in a significant increase in the ROM, and the NZ showed a slight change after step reduction. For the L1-L2 segment, resection of the FCL led to an increased ROM in LB.With rupture of SSL or LF, the stability of the segment decreased significantly compared with the intact and fracture model, particularly in FE motion, the function of the PLC was considered to be incompetent.

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.].

Vertebral bone attenuation on low-dose chest CT: quantitative volumetric analysis for bone fragility assessment

This study evaluated the use of low-dose chest computed tomography (LDCT) for detecting bone fragility. LDCT-measured vertebral bone attenuation by volumetric methods showed good correlation with bone mineral density (BMD) measured by dual-energy x-ray absorptiometry (DXA, and good diagnostic performance for identifying osteoporosis and compression fractures. The results of this study suggest the feasibility of obtaining comprehensive information on bone health in subjects undergoing LDCT.

INTRODUCTION

Osteoporosis is a prevalent but underdiagnosed disease that increases fracture risk. This study evaluated the utility of vertebral attenuation derived from low-dose chest computed tomography (LDCT) compared to dual-energy x-ray absorptiometry (DXA) for detecting bone fragility.

METHODS

A total of 232 subjects (78 men and 154 women) aged above 50 years who underwent both LDCT and DXA within 30 days were evaluated. LDCT-measured bone attenuation in Hounsfield units (HU) of four vertebrae (T4, T7, T10, and L1) was evaluated using volumetric methods for correlation with DXA-measured bone mineral density (BMD) and for the diagnosis of compression fractures, osteoporosis, and low BMD (osteoporosis or osteopenia) in men and women, with DXA measurements as the reference standard.

RESULTS

The average attenuation of the four vertebrae showed strong correlation with DXA-measured BMD of the lumbar spine (r = 0.726, p < 0.05). In receiver-operating characteristic (ROC) analyses, the area under the curve (AUC) across LDCT-measured thresholds of the average attenuation to distinguish compression fractures was 0.827, and a threshold of 129.5 HU yielded 90.9 % sensitivity and 64.4 % specificity. Similarly, average attenuation showed high AUCs and good diagnostic performance for detecting osteoporosis and low BMD in both men and women. Among 44 subjects with compression fractures, the average bone attenuation showed strong negative correlation with both the worst fracture grade (r = -0.525, p < 0.05) and cumulative fracture grade score (r = -0.633, p < 0.05).

CONCLUSION

LDCT-measured bone attenuation by volumetric methods showed good correlation with BMD measured by DXA and good diagnostic performance for identifying bone fragility.

Efficiency of Balloon Kyphoplasty in the Treatment of Osteoporotic Vertebral Compression Fractures

Eighty-seven osteoporotic vertebral fractures of 82 patients were treated with balloon kyphoplasty. Preoperative, postoperative and follow-up outcomes of functional impairment, pain scores and vertebral height restorations of the patients were recorded and evaluated statistically. Seventy-two of the patients were female (87.8%) and 10 (12.2%) were male. Mean age of all patients were 66.4 years. Preoperative mean Anterior Vertebral Body Height of 48.20±13.94 % and Middle Vertebral Body Height of 59.40±14.26 % were recorded as 79.91±9.50 % and 86.90±8.38 % respectively postoperatively and noted to be 73.26±8.59 % and 84.65±8.19 % at last controls respectively. The mean Oswestry Disability Index and Visual Analog Pain Scale also improved significantly. Local Kyphosis of all the patients were also evaluated and a significant improvement was noted postoperatively. The long term results of this study suggest that balloon kyphoplasty is an effective and safe treatment option in osteoporotic vertebral fractures and should be considered for functional improvement, pain relief and height restoration.

Tuberculous Spondylitis Following Kyphoplasty: A Case Report and Review of the Literature

Tuberculous spondylitis of the augmented vertebral column following percutaneous vertebroplasty or kyphoplasty has rarely been described. We report an unusual case of tuberculous spondylitis diagnosed after percutaneous kyphoplasty (PKP). A 61-year-old woman presented to our institution complaining of back pain following a fall 7 days before. Radiologic studies revealed an acute osteoporotic compression L1 fracture. The patient denied history of pulmonary tuberculosis (TB) and there were no signs of infection. The patient was discharged from hospital 4 days after undergoing L1 PKP with a dramatic improvement in her back pain. Two years later, the patient was readmitted with a 1 year history of recurrent back pain. Imaging examinations demonstrated long segmental bony destruction involving L1 vertebra with massive paravertebral abscess formation. The tentative diagnosis of tuberculous spondylitis was made, after a serum T-SPOT. The TB test was found to be positive. Anterior debridement, L1 corpectomy, decompression, and autologous rib graft interposition, and posterior T8-L4 instrumentation were performed. The histologic examination of the resected tissue results confirmed the diagnosis of spinal TB. Anti-TB medications were administered for 12 months and the patient recovered without sequelae. Spinal TB and osteoporotic vertebral compression fractures are similar clinically and radiologically. Spinal surgeons should consider this disease entity to avoid misdiagnosis or complications. Early surgical intervention and anti-TB treatment should be instituted as soon as the diagnosis of spinal TB after vertebral augmentation is made.

Determination of the painful level in osteoporotic vertebral fractures--Retrospective comparison between plain film, bone scan, and magnetic resonance imaging

BACKGROUND

Determining the actual painful vertebral level is difficult when evaluating osteoporotic vertebral fracture, especially when there are acute and chronic fractures simultaneously. In this study, we retrospectively evaluated and compared the findings between plain film, bone scan, and magnetic resonance imaging (MRI) in the diagnosis of new fracture in osteoporotic vertebral fractures.

METHODS

This is a retrospective clinical study of patients who were diagnosed with osteoporotic vertebral fractures using plain film, bone scan, and MRI within a 1-month interval between February 2008 and December 2012. The findings in plain film, the extent of increased uptake in bone scan, and signal change in MRI were compared to evaluate the actual level of pain. All patients received percutaneous vertebroplasty according to MR finding. Pain scores (visual analog scale) of the study patients were compared prior to and after the procedure.

RESULTS

A total of 52 patients with a mean age of 79.1 years (range 59-92 years) were enrolled in this study, and were treated by vertebroplasty confirmed by MRI. It was observed that patient pain score (visual analog scale) improved from 7.6 to 2.8. Plain film examination revealed 79 vertebrae that were suspected to be compression fractures. Among the suspected vertebrae, 62 showed increased uptake in bone scan, and MRI showed bony edema change in 58 vertebrae. The consistency between bone scan and MRI was 96.9% in patients with single-level suspected fracture on plain film. There was moderate agreement (kappa was 0.56) in patients where multiple levels were noted. Fifteen vertebrae with vacuum cleft sign on plain film showed total concordance in both bone scan and MRI.

CONCLUSION

For patients with single-level compression fracture, the painful level in osteoporotic vertebral fractures can be determined by plain film and bone scan testing. Vacuum cleft sign noted on plain film may be enough to localize the level of pain. However, MRI testing is further needed in multiple osteoporotic vertebral fracture patients.

Effects of acceleration level on lumbar spine injuries in military populations

BACKGROUND CONTEXT

Clinical studies have indicated that thoracolumbar trauma occurs in the civilian population at its junction. In contrast, injury patterns in military populations indicate a shift to the inferior vertebral levels of the lumbar spine. Controlled studies offering an explanation for such migrations and the associated clinical biomechanics are sparse in literature.

PURPOSE

The goals of this study were to investigate the potential roles of acceleration loading on the production of injuries and their stability characteristics using a human cadaver model for applications to high-speed aircraft ejection and helicopter crashes.

STUDY DESIGN

Biomechanical laboratory study using unembalmed human cadaver lumbar spinal columns.

METHODS

Thoracolumbar columns from post-mortem human surrogates were procured, x-rays taken, intervertebral joints and bony components evaluated for degeneration, and fixed using polymethylmethacrylate. The inferior end was attached to a platform via a load cell and uniaxial accelerometer. The superior end was attached to the upper metal platform via a semi-circular cylinder. The pre-flexed specimen was preloaded to simulate torso mass. The ends of the platform were connected to the vertical post of a custom-designed drop tower. The specimen was dropped inducing acceleration loading to the column. Axial force and acceleration data were gathered at high sampling rates, filtered, and peak accelerations and inertia-compensated axial forces were obtained during the loading phase. Computed tomography images were used to identify and classify injuries using the three-column concept (stable vs. unstable trauma).

RESULTS

The mean age, total body mass, and stature of the five healthy degeneration-free specimens were 42 years, 73 kg, and 167 cm. The first two specimens subjected to peak accelerations of approximately 200 m/sec(2) were classified as belonging to high-speed aircraft ejection-type and the other three specimens subjected to greater amplitudes (347-549 m/sec(2)) were classified as belonging to helicopter crash-type loadings. Peak axial forces for all specimens ranged from 4.8 to 7.2 kN. Ejection-type loaded specimens sustained single-level injuries to the L1 vertebra; one injury was stable and the other was unstable. Helicopter crash-type loaded specimens sustained injuries at inferior levels, including bilateral facet dislocation at L4-L5 and L2-L4 compression fractures, and all specimens were considered unstable at least at one spinal level.

CONCLUSIONS

These findings suggest that the severity of spinal injuries increase with increasing acceleration levels and, more importantly, injuries shift inferiorly from the thoracolumbar junction to lower lumbar levels. Acknowledging that the geometry and load carrying capacity of vertebral bodies increase in the lower lumbar spine, involvement of inferior levels in trauma sparing the superior segments at greater acceleration inputs agree with military literature of caudal shift in injured levels. The present study offers an experimental explanation for the clinically observed caudal migration of spinal trauma in military populations as applied to high-speed aircraft ejection catapult and helicopter crashes.

Surgical versus non-surgical treatment for vertebral compression fracture with osteopenia: a systematic review and meta-analysis

BACKGROUND

Surgical and non-surgical interventions are the two categories for treatment of vertebral compression fractures (VCFs). However, there is clinical uncertainty over optimal management. This study aimed to examine the safety and effectiveness of surgical management for treatment of VCFs with osteopenia compared with non-surgical treatment.

METHODS

We conducted a systematic search through electronic databases from inception to June 2014, with no limits on study data or language. Randomized controlled trials (RCTs) evaluating surgical versus non-surgical interventions for treatment of patients with VCFs due to osteopenia were considered. Primary outcomes were pain and adverse effects. A random-effects model was used to calculate the pooled mean difference (MD) or risk ratios with 95% confidence interval (CI).

RESULTS

Sixteen reports (11 studies) met the inclusion criteria, and provided data for the meta-analysis with a total of 1,401 participants. Compared with conservative treatment, surgical treatment was more effective in reducing pain (short-term: MD -2.05, 95% CI -3.55 to -0.56, P=0.007; mid-term: MD -1.70, 95% CI -2.78 to -0.62, P=0.002; long-term: MD -1.24, 95% CI -2.20 to -0.29, P=0.01) and disability on the Roland-Morris Disability score (short-term: MD -4.97, 95% CI -8.71 to -1.23, P=0.009), as well as improving quality of life on the Short-Form 36 Physical Component Summary score (short-term: MD 5.53, 95% CI 1.45 to 9.61, P=0.008) and the Quality of Life Questionnaire of the European Foundation for Osteoporosis score (short-term: MD -5.01, 95% CI -8.11 to -1.91, P=0.002). Indirect comparisons between vertebroplasty and kyphoplasty found no evidence that the treatment effect differed across the two interventions for any outcomes assessed. Compared with the sham procedure, surgical treatment showed no evidence of improvement in pain relief and physical function. Based on these two comparisons, no significant difference between groups was noted in the pooled results for adverse events.

CONCLUSION

Compared to conservative treatment, surgical treatment was more effective in decreasing pain in the short,mid and long terms. However, no significant mid- and long-term differences in physical function and quality of life was observed. Little good evidence is available for surgical treatment compared with that for sham procedure. PV and BK are currently used to treat VCFs with osteopenia, with little difference in treatment effects. Evidence of better quality and from a larger sample size is required before a recommendation can be made.

SYSTEMATIC REVIEW REGISTRATION

http://www.crd.york.ac.uk/PROSPERO PROSPERO registration number: CRD42013005142.

Activities of everyday life with high spinal loads

Activities with high spinal loads should be avoided by patients with back problems. Awareness about these activities and knowledge of the associated loads are important for the proper design and pre-clinical testing of spinal implants. The loads on an instrumented vertebral body replacement have been telemetrically measured for approximately 1000 combinations of activities and parameters in 5 patients over a period up to 65 months postoperatively. A database containing, among others, extreme values for load components in more than 13,500 datasets was searched for 10 activities that cause the highest resultant force, bending moment, torsional moment, or shear force in an anatomical direction. The following activities caused high resultant forces: lifting a weight from the ground, forward elevation of straight arms with a weight in hands, moving a weight laterally in front of the body with hanging arms, changing the body position, staircase walking, tying shoes, and upper body flexion. All activities have in common that the center of mass of the upper body was moved anteriorly. Forces up to 1650 N were measured for these activities of daily life. However, there was a large intra- and inter-individual variation in the implant loads for the various activities depending on how exercises were performed. Measured shear forces were usually higher in the posterior direction than in the anterior direction. Activities with high resultant forces usually caused high values of other load components.

[Analysis of clinical effects of percutaneous vertebroplasty and percutaneous kyphoplasty in treating osteoporotic vertebral compression fracture]

OBJECTIVE

To explore the clinical outcomes of percutaneous vertebroplasty (PVP) and percutaneous kyphoplasty (PKP) in treating osteoporotic vertebral compression fracture (OVCF).

METHODS

From January 2007 to February 2010, the data of 40 patients with osteoporotic vertebral compression fracture underwent treatment were retrospectively analyzed. Of them,20 patients were treated with PVP (PVP group), there were 8 males and 12 females with an average age of (66.37 +/- 2.34) years old (54 to 81); 20 patients were treated with PKP (PKP group), there were 11 males and 9 females with an average of (65.12 +/- 3.21) years old (56 to 79). Postoperative at 1 week, 12 weeks, 1 year, pain and daily life function were respectively assessed by visual analogue scale (VAS) and Barthel index (BI); and anterior height of responsibility vertebra, Cobb angle were measured by X-rays.

RESULTS

In PVP group, 1 case complicated with bone cement leakage without clinical symptoms and no operation to treat. No postoperative infection and deep vein thrombosis were found between two groups. All patients were followed up more than 1 year, pain and daily life function has obviously improved than preoperative (P < 0.01); and there was no significant difference on 1 week, 12 weeks, 1 year after operation (P > 0.05); there was no significant difference between two groups (P > 0.05). In PVP group, there was no significant difference in anterior height of responsibility vertebra, Cobb angle before and after operation;and in PKP group, postoperative data has obviously improved than preoperative (P < 0.01), but there was no significant difference postoperative at 1 week, 12 weeks, 1 year (P > 0.05); there was no significant difference between two groups at 1 week, 12 weeks, 1 year after operation.

CONCLUSION

Both the methods can obviously relieve pain and completely or partly recover daily life function in treating OVCF. But PKP has advantages of recovery of anterior height of responsibility vertebra and correction of Cobb angle, especially for serious compression.

Scores on the Safe Functional Motion test predict incident vertebral compression fracture

The Safe Functional Motion test (SFM) was developed to document movement strategies used to perform everyday activities that may increase the risk for osteoporotic fracture. After adjusting for variables known to predict vertebral compression fracture (VCF), baseline score on the SFM was a significant independent predictor of incident VCF at 1- and 3-year follow-ups.

INTRODUCTION

Functional movements may contribute to risk for VCF. We hypothesize that scores on the SFM, a performance-based test of physical function, are associated with incident VCF.

METHODS

An osteoporosis clinic database was queried for men and women ≥ 50 years with an initial SFM and corresponding data for prevalent VCF, history of injurious falls, femoral neck bone mineral density (fnBMD), osteoporosis medication use, and incident morphometric VCF at 1-year (n = 878) and 3-year follow-ups (n = 503). Multiple logistic regressions, adjusted for gender, age, injurious fall(s), fnBMD, prevalent VCF at baseline, and osteoporosis medication use, were used to determine whether SFM score was associated with incident VCF at follow-up visits.

RESULTS

Baseline SFM score was a significant independent predictor of incident VCF at 1-year follow-up (adjusted odds ratio (95 % confidence intervals (CI)) = 0.818 (0.707, 0.948); p < 0.008) and 3-year follow-up (adjusted odds ratio (95 % CI) = 0.728 (0.628, 0.844); p < 0.0001). Baseline fnBMD and osteoporosis medication use were significant predictors at 1-year (p = 0.05 and < 0.0001, respectively) and 3-year (p < 0.01 and 0.001, respectively) follow-ups. At 3-year follow-up, gender and prevalent VCF were also significant predictors (p = 0.003 and 0.007, respectively).

CONCLUSIONS

For every 10-point increase in SFM score, the odds of future VCF decreases by 18 % at 1 year and 27 % at 3 years after adjusting for known covariates. The SFM may aid in the identification of modifiable functional risk factors for VCF.

Considerations on evolution and healing of vertebral fractures

Only little is known when talking about the evolution of a vertebral fracture. From the few studies available in the literature, we can deduce that the risk a vertebral compression fracture has to worsen its deformity is consistent. It is important to try to make a prognosis on how the fracture is going to heal based on the type of fracture encountered. A chapter of its own is the occurrence of a vertebral fracture non-union that is difficult to diagnose and treat, but comes along with a poor prognosis.

Clinical measurement of intravertebral pressure during vertebroplasty and kyphoplasty

BACKGROUND

Vertebroplasty (VP) and kyphoplasty (KP) are emerging procedures for almost immediate pain relief when treating osteoporotic or osteolytic fractures. The main reported complication is polymethylmethacrylate (PMMA) leakage, which may lead to compression of neural structures or embolism. Different authors have proposed that intravertebral pressure (IP) is an important factor determining the risk for leakage, although so far only limited information has been gathered from clinical and experimental studies. There is also a lack of understanding of the IP during conventional interventions in VP and KP in the clinic.

OBJECTIVE

(1) To compare the intravertebral pressures of compressed vertebrae and adjacent normal vertebrae. (2) To measure the IP of compressed vertebrae during VP and KP.

SETTING

An interventional pain management practice, a medical center, major metropolitan city, in the People's Republic of China.

METHODS

Thirty-five patients (with 40 compressed vertebrae and 35 adjacent normal vertebrae) were randomly allocated for intravertebral pressure measurements. Cannulas were placed bipedicularly into the posterior third of each vertebral body. Either PMMA or a balloon was injected into the vertebral body through the right cannula. A manometer was connected to the cannula in the left pedicle, and heparin was injected to verify the pressure measurement system.

RESULTS

The range (minimum-maximum), average IP, and the standard deviation of the compressed vertebrae were 0-39 mm Hg and 24.5 ±11.3 mm Hg; and that of adjacent normal vertebrae were 3-16 mm Hg, 7.3 ± 4.2 mm Hg. Furthermore, the average IP for Phase 1 (before PMMA injection) for VP was 23 ±11.9 mm Hg; the maximum IP recorded during injection was 169 ± 46.8 mm Hg and the IP for 10 minutes after injection was 33 ±9.4 mm Hg. Meanwhile, the highest IP recorded for KP patients was 142 ±39.6 mm Hg. The average IP for Phase 1 (before balloon inflation) was 24 ±12.7 mmHg; Phase 2 (peak IP during the balloon inflation) was 63 ± 25.8 mm Hg; and Phase 3 (after balloon inflation/before PMMA injection) was , and 18 ± 10.8 mm Hg. The IP for 10 minutes after injection in KP patients was 36 ± 8.5 mm Hg.

LIMITATIONS

The flow rate was manually controlled, which is in line with clinical routine, and was kept at approximately 0.1 mL/s. Because the speed of injection was controlled by hand, an exact injection rate could not be assured, leading to some inaccuracy when comparing the IP of VP and KP patients. Each patient was injected with a different PMMA volume. Because PMMA injection was performed to a satisfactory vertebral body filling and limited by any signs of extravasation, it was difficult to maintain a constant injection volume, unlike in vitro studies. Other factors such as the damage to the vertebral shell or the degree of osteoporosis might also have affected the intravertebral pressure.

CONCLUSION

This study showed that the IP of compressed vertebrae was significantly higher than that of adjacent normal vertebrae. There was a significant increase in IP during the PMMA filling in VP and KP; the IP of compressed vertebrae was not significantly reduced by the balloon inflation in KP, and no statistically significant differences in IP were found during all common stages of PMMA filling in VP and KP.

Long-term skeletal consequences of childhood acute lymphoblastic leukemia in adult males: a cohort study

OBJECTIVE

Long-term health sequelae of childhood-onset acute lymphoblastic leukemia (ALL) remain largely unknown. Low bone mineral content (BMC) and bone mineral density (BMD) are recognized complications, but it is unknown whether these persist until adulthood. We evaluated skeletal characteristics and their association with ALL therapy in long-term male ALL survivors.

DESIGN

This cross-sectional cohort study included 49 long-term male ALL survivors and 55 age-matched healthy males.

METHODS

BMD and compression fractures were assessed by dual-energy X-ray absorptiometry; blood biochemistry was obtained for parameters of calcium homeostasis.

RESULTS

The ALL survivors (median age 29 years, range 25-38 years), assessed 10-38 years after ALL diagnosis, had lower lumbar spine (P<0.001), femoral neck (P<0.001), and whole-body (P=0.017) BMD than expected based on normative values. When compared with the controls (median age 30 years, range 24-36 years), the ALL survivors had lower lumbar spine BMC (P=0.014), lower whole-body BMC (P<0.001), and lower whole-body BMD (P<0.001), but the differences were partly explained by differences in height. Altogether, 20% of the ALL survivors had spinal compression fractures, but these were equally prevalent in the controls. Males diagnosed with ALL before age 5 years had significantly lower BMD values. Other recognized risk factors included untreated hypogonadism, vitamin D deficiency, hypophosphatemia, low IGF-binding protein-3, and low physical activity.

CONCLUSIONS

At young adulthood, long-term male ALL survivors have significantly reduced BMC and BMD and a high prevalence of spinal compression fractures. Careful follow-up and active treatment of the recognized risk factors are warranted.

Spinal loads during position changes

BACKGROUND

Recommendations exist how patients should change from one body position to another in order to keep the spinal loads low. However, until now it is not clear whether the loads are in fact lower if the patients follow these recommendations. The aim was to measure the loads while changing the body position.

METHODS

Telemeterized vertebral body replacements have been inserted into 5 patients who had a severe compression fracture of a lumbar vertebral body. The acting loads were measured during a changing of the body position while lying and when moving from lying to sitting, from sitting to standing and vice versa.

FINDINGS

When the lying patients changed their position according to the physiotherapist's recommendations, the resultant force was nearly as high as it was during relaxed standing. Otherwise, the force was nearly twice as high. Changing from a lateral lying position to sitting and vice versa caused forces of about 180% of those seen for standing when the recommendations were heeded. Without instructions, the loads were about 70% higher. Use of a trapeze bar mounted to the bed did not increase the loads. Rising from a chair with the arms hanging down laterally led to average resultant forces of 380% related to standing. Placing the hands on armrests reduced this value to 180%.

INTERPRETATION

High forces may act on the spine when changing from one body position to another. These loads can be minimized when following the physiotherapist's instructions and when supporting the upper body by the arms.

Analysis of micro fracture in human Haversian cortical bone under compression

A procedure to investigate local stress intensity factors in human Haversian cortical bone under compression is presented. The method combines a customised experimental setting for micro-compression tests of millimetric bone specimens and a finite element contact model conforming to the bone morphology that tracks advancing microcracks. The non-interpenetration conditions along the crack edges are ensured by penalty constraints of which the parameters are optimised for minimum contact pressure error with respect to the crack orientations. A cohesive crack opening law is implemented in the wake of the crack tips to remain consistent with the progressive tearing of collagen fibrils. The displacement solution is searched by a Newton-Raphson scheme containing a double loop first on the displacements and second on the frictional contact and cohesive condition updates at the crack interfaces. The experimental Dirichlet boundary conditions are acquired by digital image cross-correlation of bone light microscopy observations and then imported into the model. The local mechanical elastic moduli are measured by nanoindentation and microextensometry. The comparison of the macroscopic stress-strain numerical response with the experiment reveals the existence of narrow diffuse damaged zones near the major cracks where the local stress intensity factors can be calculated.

Mechanical failure begins preferentially near resorption cavities in human vertebral cancellous bone under compression

The amount of bone turnover in the body has been implicated as a factor that can influence fracture risk and bone strength. Here we test the idea that remodeling cavities promote local tissue failure by determining if microscopic tissue damage (microdamage) caused by controlled loading in vitro is more likely to form near resorption cavities. Specimens of human vertebral cancellous bone (L4, 7 male and 2 female, age 70±10, mean±SD) were loaded in compression to the yield point, stained for microscopic tissue damage and submitted to three-dimensional fluorescent imaging using serial milling (image voxel size 0.7×0.7×5.0 μm). We found the resulting damage volume per bone volume (DV/BV) was correlated with percent eroded surface (p<0.01, r(2)=0.65), demonstrating that whole specimen measures of resorption cavities and microdamage are related. Locations of microdamage were more than two times as likely to have a neighboring resorption cavity than randomly selected sites without microdamage (relative risk 2.39, 95% confidence interval of relative risk: 2.09-2.73), indicating a spatial association between resorption cavities and microdamage at the local level. Individual microdamage sites were 48,700 (40,100; 62,700) μm(3) in size (median, 25th and 75th percentiles). That microdamage was associated with resorption cavities when measured at the whole specimen level as well as at the local level provides strong evidence that resorption cavities play a role in mechanical failure processes of cancellous bone and therefore have the potential to influence resistance to clinical fracture.

Endovascular cooling for severe hyperthermia in cervical spine injury

BACKGROUND

Sustained severe hyperthermia in patients with high cervical spinal cord injuries may have many etiologies, from infection to autonomic dysregulation. When uncontrolled, it has been seen to have a high morbidity and mortality.

METHODS

We present two patients with high cervical spinal cord injury (SCI) who had sustained severe hyperpyrexia, of possible autonomic origin. The temperature stayed above 40°C and was uncontrolled with conventional methods of temperature management.

RESULTS

We employed endovascular cooling for therapeutic normothermia which was successful in effective control of temperature in both the patients. The first patient suffered complications from deep vein thrombosis and pulmonary embolism which may be attributed to the presence of the cooling catheter in spite of chemical and mechanical thromboprophylaxis.

CONCLUSIONS

The use of endovascular cooling in the management of severe life threatening hyperthermia in patients with cervical SCI may be an useful intervention. There must be a high suspicion for the possibility of deep vein thrombosis in this subgroup, however.

Biomechanics of vertebral compression fractures and clinical application

Local biomechanical factors in the etiology of vertebral compression fractures are reviewed. The vertebral body is particularly vulnerable to compression fracture when its bone mineral density (BMD) falls with age. However, the risk of fracture, and the type of fracture produced, does not depend simply on BMD. Equally important is the state of degeneration of the adjacent intervertebral discs, which largely determines how compressive forces are distributed over the vertebral body. Disc height also influences load-sharing between the vertebral body and neural arch, and hence by Wolff's Law can influence regional variations in trabecular density within the vertebral body. Vertebral deformity is not entirely attributable to trauma: it can result from the gradual accumulation of fatigue damage, and can progress by a quasi-continuous process of "creep". Cement injection techniques such as vertebroplasty and kyphoplasty are valuable in the treatment of these fractures. Both techniques can stiffen a fractured vertebral body, and kyphoplasty may contribute towards restoring its height. The presence of cement can limit endplate deformation, and thereby partially reverse the adverse changes in load-sharing which follow vertebral fracture. Cement also reduces time-dependent "creep" deformation of damaged vertebrae.

Sensorimotor experience influences recovery of forelimb abilities but not tissue loss after focal cortical compression in adult rats

Sensorimotor activity has been shown to play a key role in functional outcome after extensive brain damage. This study was aimed at assessing the influence of sensorimotor experience through subject-environment interactions on the time course of both lesion and gliosis volumes as well as on the recovery of forelimb sensorimotor abilities following focal cortical injury. The lesion consisted of a cortical compression targeting the forepaw representational area within the primary somatosensory cortex of adult rats. After the cortical lesion, rats were randomly subjected to various postlesion conditions: unilateral C5-C6 dorsal root transection depriving the contralateral cortex from forepaw somatosensory inputs, standard housing or an enriched environment promoting sensorimotor experience and social interactions. Behavioral tests were used to assess forelimb placement during locomotion, forelimb-use asymmetry, and forepaw tactile sensitivity. For each group, the time course of tissue loss was described and the gliosis volume over the first postoperative month was evaluated using an unbiased stereological method. Consistent with previous studies, recovery of behavioral abilities was found to depend on post-injury experience. Indeed, increased sensorimotor activity initiated early in an enriched environment induced a rapid and more complete behavioral recovery compared with standard housing. In contrast, severe deprivation of peripheral sensory inputs led to a delayed and only partial sensorimotor recovery. The dorsal rhizotomy was found to increase the perilesional gliosis in comparison to standard or enriched environments. These findings provide further evidence that early sensory experience has a beneficial influence on the onset and time course of functional recovery after focal brain injury.

[Fenestration operation for treatment of acetabular parastyle fracture combined with articular facet compression and collapse of acetabular top involving weight-bearing dome]

OBJECTIVE

To analyze the fenestration operation for treatment of acetabular parastyle fracture combined with articular facet compression and collapse of acetabular top involving weight-bearing dome.

METHODS

From July 2005 to February 2007, 52 cases of acetabular parastyle fracture combined with articular facet compression and collapse of acetabular top involving weight-bearing dome were treated by two methods. Among them, 24 cases were treated by fenestration operation for articular facet reduction, bone grafing, anatomical reconstruction of the acetabular parastyle with internal fixation, included 17 males and 7 females with an average age of (35.2 +/- 6.4) years old; the other 28 cases were treated only anatomical reconstruction of the acetabular parastyle with internal fixation, included 19 males and 9 females with an average age of (36.4 +/- 4.8) years old. All the patients were evaluated with modified d'Aubigne-Postel clinical evaluation standard.

RESULTS

All patients gained bone healing. There were only 1 patient occurenced femoral nerve injury and recovered 2 months later. There were no other complications. All patients were followed up from 12 to 51 months (averaged in 31.5 months). According to modified d'Aubigne-Postel clinical evaluation standard, there were statistic difference between the two groups of patients in pain, walking, range of motion and total score. In fenestration operation group, the results were excellent in 13 patients, good in 9, fair in 1, poor in 1; in parastyle reduction group,the results were excellent in 9 patients, good in 11, fair in 6, poor in 2 (u=0.613, P<0.05).

CONCLUSION

Fenestration operation for treatment of acetabular parastyle fracture combined with articular facet compression and collapse of acetabular top involving weight-bearing dome is a feasible method for the recovery of hip joint function.

[Three-dimensional finite element model of thoracolumbar spine with osteoporotic vertebral compression fracture]

OBJECTIVE

To build a three-dimensional finite element model of thoracolumbar spine with osteoporotic vertebral compression fracture (OVCF) and analyze its biomechanical change.

METHODS

The T10-L2 segment data were obtained from computed tomography (CT) scans of an elderly female with a single T12 OVCF. A three-dimensional finite element model of thoracolumbar spine was constructed with the MIMICS and ABAQUS software. The model was composed of bony vertebrae, articulating facets, intervertebral disc and associated ligaments. The basic stress analysis of T10-L2 motion segment was made for different material properties of bone, ligaments and facet joints contacting frictional property. The stress on the annulus fiber, nucleus pulposus, endplate and facet joints under axial pressure (0.3 MPa, 1.0 MPa, 4.0 MPa) were analyzed.

RESULTS

A three-dimensional finite element model of human T12-L2 motion segment had 617468 elements. And the stress was higher in vertebral body than posterior structure. The distribution of pressure stresses in intervertebral disc was asymmetrical. The stress increased with a rising axial pressure.

CONCLUSION

3D finite element model of thoracolumbar OVCF and adjacent segments are successfully established. The results of stress analysis are both feasible and reliable.

Chondrosis of the disc - risk factor for osteoporotic vertebral fractures (biomechanical analysis)

Based on biomechanical analysis, we present an until now unrecognised new view on pathological interactive relations in basic functional motor segments of the spine (vertebra - disc - vertebra), elevating the risk of osteoporotic vertebral fractures. They are classified as follows: 1. Degenerative alterations of intervertebral disc (chondrosis); 1a) decrease of intervertebral disc viscoelasticity; 1b) increase of compressive and tensile stress in the intervertebral disc. Loading the spine increases the compressive and tensile stress in the disc, afflicted by chondrosis, beyond physiological values. This increase conditions the non-physiological elevation of reaction compression forces in adjacent vertebrae, representing a fracture risk for endplates of these vertebrae. 2. Osteoporosis of vertebrae; 2a) decrease of vertebra elasticity and strength; 2b) phenomenon of local elevated compressive stress in the vertebra fracture site. In the vertebral body endplate infraction or fracture site develop a locus minoris of resistance and it contributes to the progression of breaking the vertebra and its whole compression by loading the spine with compressive force. With regard to the fact that above-mentioned risk factors are influenceable, we suggest preventive measures.

A parametric study of hard tissue injury prediction using finite elements: consideration of geometric complexity, subfailure material properties, CT-thresholding, and element characteristics

OBJECTIVE

The objectives of this study were to examine the axial response of the clavicle under quasistatic compressions replicating the body boundary conditions and to quantify the sensitivity of finite element-predicted fracture in the clavicle to several parameters.

METHODS

Clavicles were harvested from 14 donors (age range 14-56 years). Quasistatic axial compression tests were performed using a custom rig designed to replicate in situ boundary conditions. Prior to testing, high-resolution computed tomography (CT) scans were taken of each clavicle. From those images, finite element models were constructed. Factors varied parametrically included the density used to threshold cortical bone in the CT scans, the presence of trabecular bone, the mesh density, Young's modulus, the maximum stress, and the element type (shell vs. solid, triangular vs. quadrilateral surface elements).

RESULTS

The experiments revealed significant variability in the peak force (2.41 +/- 0.72 kN) and displacement to peak force (4.9 +/- 1.1 mm), with age (p < .05) and with some geometrical traits of the specimens. In the finite element models, the failure force and location were moderately dependent upon the Young's modulus. The fracture force was highly sensitive to the yield stress (80-110 MPa).

CONCLUSION

Neither fracture location nor force was strongly dependent on mesh density as long as the element size was less than 5 x 5 mm(2). Both the fracture location and force were strongly dependent upon the threshold density used to define the thickness of the cortical shell.

Vertebroplasty for vertebral compression fracture

The patients with intensive pain caused by the vertebra body fracture were treated by application of bone cement under local or general anesthesia, by means of diascopy through unilateral transpedicular approach. The intensity of pain was followed-up on the VAS scale before surgery, 24 hours after surgery and three months after surgery. The cement was applied in 55 patients (43 women, 12 men). The average age of the tests was 68.43 years (38 to 82 years). Fifty five procedures were implemented on 85 vertebrae, i.e. 32 metastatic fractures and 23 osteoporotic fractures. The procedures were applied on 28 thoracal and 57 lumbar vertebrae. The average VAS before surgery was 8.36 and 2.23 (p < 0.005) 24 hours after surgery, and it remained almost unchanged three months later. There were 1 serious complication, a paraparesis caused by the leakage of cement into the spinal canal, which was partially recovered after decompression and rehabilitation treatment, and 2 superficial infections with S. epidermidis which were cured by means of antibiotics. By means of Wilcoxon paired test a significant difference was found between the preoperative VAS and the value 24 hours after surgery (n = 55, Z = 6.451, p < 0.00001) and 3 months after surgery (Z = 6.45, p < = 0.00001), while there was a compliance between two VAS measurements after surgery (Z = 1.308, p = 0.191) which indicates that the fast pain reduction remained stable during the 3 month follow-up. The vertebroplasty is a safe and efficient surgical method in treatment of compressive vertebrae fractures which do not react to the conventional method of treatment. The achieved analgesic effect 24 hours after surgery is a good predictor of pain intensity 3 months after surgery.

Efficacy of percutaneous vertebroplasty for multiple synchronous and metachronous vertebral compression fractures

BACKGROUND AND PURPOSE

Limited data exists regarding the efficacy of percutaneous vertebroplasty for multiple synchronous and metachronous vertebral compression fractures. The purpose of this study was to evaluate whether the number of vertebral levels treated during percutaneous vertebroplasty procedures or the number of separate vertebroplasty procedures performed on a given patient affect clinical outcomes.

MATERIALS AND METHODS

We defined 3 patient populations in our retrospective study. Group 1 included 328 patients who underwent 1 single-level vertebroplasty procedure. Group 2 included 226 patients who underwent a single procedure in which 2 or more vertebral levels were treated. Group 3 included 101 patients who underwent 2 or more separate vertebroplasty procedures. Follow-up was performed between 1 week and 2 years postoperatively. Clinical outcomes were assessed through analysis of quantitative measurements of pre- and postoperative levels of pain with and without activity (0-10) as well as mobility improvement. The Kruskal-Wallis rank sum test was used to evaluate the differences among groups. Univariate and chi(2) analyses were performed to show the proportion of underlying diseases in each group.

RESULTS

Mean pain improvement with/without activity at 2-year follow-up was 5.8/3, 4.9/3.7, and 5.4/3.1 in groups 1, 2, and 3, respectively; and mean mobility improvement in 2-year follow-up was 0.67, 0.63, and 0.65 for groups 1, 2, and 3, respectively.

CONCLUSIONS

There was no significant difference in pain relief and mobility improvement in patients treated for multiple synchronous or metachronous vertebral compression fractures in comparison with those treated for solitary isolated fractures.

Tissue-level failure accumulation in vertebral cancellous bone: a theoretical model

Vertebral compression fractures are a potentially severe injury, which is characteristic to osteoporotic elderly. Despite being a significant healthcare problem, the etiology of compression fractures is not fully understood, and there are no biomechanical models in the literature that describe the development of these fractures based on cancellous bone failure accumulation. The objective of this study was therefore to develop a computational model of tissue-level failure accumulation in vertebral cancellous bone, which eventually leads to compression fractures. The model predicts the accumulated percentage of broken trabeculae delta in a vertebral region of interest (ROI) over 60 years, by employing Euler's theory for elastic buckling. The accumulated failure delta is calculated as function of the daily activity characteristics and rate of annual bone loss (RABL) with aging. An RABL of unity represents the normal bone loss attributed to aging per se, whereas RABL>1 is assumed to represent pathological bone metabolism such as osteoporosis. Simulations were conducted for a range of RABLs, to determine the effect of changes in bone metabolism on the accumulation of bone failure. Results showed that bone failure rapidly increased with RABL. Generally, trabecular failure was shown to become more severe for RABL>4. Total failure was exhibited at RABL=7.5 for the central ROI, and at RABL=8.5 for the sub-endplate ROI. We concluded that vertebral compression fractures advance monotonically between the age of 50-55 years and 70 years, and may accelerate thereafter if RABL is high (~8). Additionally, the model identified weight lifting as the action that most dramatically accelerated the destruction of osteoporotic spinal cancellous bone. The present biomechanical model is useful for understanding the etiology of compression fractures, and potentially, depending on further experimental characterization of RABL, for considering the effects of medications that influence bone metabolism on patient prognosis.

Effect of bone density on vertebral strength and stiffness after percutaneous vertebroplasty

STUDY DESIGN

An ex vivo biomechanical study using cadaveric vertebral bodies.

OBJECTIVE

To determine how bone mineral density (BMD) affects mechanical strength and stiffness of the vertebral body after vertebroplasty, and to determine how the association between mechanical properties and BMD varies with amount of cement injected.

SUMMARY OF BACKGROUND DATA

Adverse events associated with vertebroplasty include cement leakage and adjacent fractures. Understanding effects of bone density and cement volume on mechanical properties may be important clinically to identify the minimum cement volume that will benefit the patient while minimizing risks of adverse events.

METHODS

The bone mineral density of 13 vertebral columns from adult white female cadavers was measured with DEXA. Vertebral bodies (n = 126) were assigned to 5 groups based on cement treatment: intact, untreated, 4% fill, 12% fill, and 24% fill. Treated specimens were first loaded asymmetrically to simulate a wedge compression fracture before injection with polymethylmethacrylate cement. Strength and stiffness were measured in axial compression.

RESULTS

Only the highest cement dose used (24% fill, 7 mL on average) had an effect on mechanical stiffness or strength. Within this group, stiffness was improved relative to untreated fractures but not restored to prefracture levels, and strength was enhanced beyond intact values. These improvements in stiffness and strength depended significantly on bone density, with highly osteoporotic samples benefitting the least.

CONCLUSION

Results suggest that highly osteoporotic patients may receive the least amount of improvement in mechanical properties after vertebroplasty. It is recommended, therefore, that cement volume be restricted to the amount needed for fracture reduction only because there may be a limit to the mechanical benefits that additional cement can offer, depending on patient bone density. Understanding these limitations can potentially minimize risks of adverse events.

Influence of geometrical personalization on the simulation of clavicle fractures

Finite element body models enable the evaluation of car occupant protection. In general, these models represent average males and inter-individual geometry variability is not taken into account. As the most frequent shoulder injury during car lateral accidents is a clavicle fracture, the purpose of this study is to investigate whether clavicle geometry has an influence on bone response until failure, and whether geometrical personalization of clavicle models is required. Eighteen clavicles from 9 subjects (5 males and 4 females, mean age: 76 +/- 12 years) were harvested. Six clavicles were scanned, enabling the development of subject-specific models and the quantification of geometrical features defining shape and cortical thickness. Bone mineral densities (BMD) were measured through double X-ray absorptiometry. Then, the general clavicle responses to dynamic compression until failure were studied. Simulations of the compression tests were carried out with the subject-specific models to assess the sensitivity of force-deflection clavicle responses to geometrical features. Clavicle fractures occurred at an average velocity of 1.41 +/- 0.4 ms(-1), with a fracture force of 1.48 +/- 0.46 kN and a deflection of 5.4 +/- 1.1 mm. A significant difference was found between male and female clavicle force values at rupture although their BMDs were not significantly different. Simulations with subject-specific models led to the conclusion that cortical bone thickness and bone shape have large effects on bone responses until failure and on fracture location. This study highlights the need for a geometrical personalization of clavicle models in order to take into account both gender discrepancies concerning clavicle shape and aging effects affecting cortical thickness.

A biomechanical investigation of vertebroplasty in osteoporotic compression fractures and in prophylactic vertebral reinforcement

STUDY DESIGN

Cadaveric single vertebrae were used to evaluate vertebroplasty as a prophylactic treatment and as an intervention for vertebral compression fractures.

OBJECTIVE

To investigate the biomechanical characteristics of prophylactic reinforcement and postfracture augmentation of cadaveric vertebrae.

SUMMARY OF BACKGROUND DATA

Percutaneous vertebroplasty is a treatment option for osteoporotic vertebral compression fractures. Short-term results are promising, but longer-term studies have suggested a possible accelerated failure rate in the adjacent vertebral body. Limited research has been conducted into the effects of prophylactic vertebroplasty in osteoporotic vertebrae. This study aims to elucidate the biomechanical differences between the 2 treatment groups.

METHODS

Human vertebrae were assigned to 2 scenarios: Scenario 1 simulated a wedge fracture followed by cement augmentation; Scenario 2 involved prophylactic augmentation using vertebroplasty. Micro-CT imaging was performed to assess the bone mineral density, vertebral dimensions, fracture pattern, and cement volume. All augmented specimens were then compressed under an eccentric flexion load to failure.

RESULTS

Product of bone mineral density and endplate surface area gave a good prediction of failure strength when compared with actual failure strength of specimens in Scenario 1. Augmented vertebral bodies showed an average cement fill of 23.9% +/- 8.07%. There was a significant postvertebroplasty increase in failure strength by a factor of 1.72 and 1.38 in Scenarios 1 and 2, respectively. There was a significant reduction in stiffness following augmentation for Scenario 1 (t = 3.5, P = 0.005). Stiffness of the vertebral body in Scenario 2 was significantly greater than observed in Scenario 1 (t = 4.4, P = 0.0002).

CONCLUSION

Results suggest that augmentation of the vertebrae postfracture significantly increases failure load, while stiffness is not restored. Prophylactic augmentation was seen to increase failure strength in comparison to the predicted failure load. Stiffness appears to be maintained suggesting that prophylactic vertebroplasty maintains stiffness better than vertebroplasty postfracture.

Single Balloon Kyphoplasty Using Far-lateral Extrapedicular Approach

OBJECTIVES

The authors have performed a single-balloon kyphoplasty using far-lateral extrapedicular approach in the treatment of osteoporotic vertebral compression fractures. The authors introduce its surgical technique and early clinical results.

METHODS

Clinical outcomes were determined by comparison of preoperative and postoperative visual analog scale score. Radiographic assessment included vertebral height restoration rate (%) and correction of kyphosis.

RESULTS

Thirty-one consecutive patients with 37 vertebrae were treated during a 5-month period and followed up for more than 6 months. Twenty-nine of 31 patients (95%) improved the visual analog scale pain score postoperatively (P<0.001). The average anterior body height was 60.85 +/- 14.27% of estimated height before procedure and 81.86 +/- 12.78% of estimated height after procedure (P<0.007). The average middle body height was 63.14 +/- 14.42% of estimated height before procedure and 80.94 +/- 18.44% of estimated height after procedure (P<0.001). The mean height restoration ratio was 31.72 +/- 20.98%. The kyphotic deformity was corrected from 16.06 +/- 5.24 degree to 8.84 +/- 3.89 degree (P<0.001). There was no surgery and device-related complications.

CONCLUSIONS

Single-balloon kyphoplasty using far-lateral extrapedicular approach is less invasive procedure that produces comparable therapeutic effects with the conventional 2-balloon technique.

Experimental hyperhomocysteinemia reduces bone quality in rats

BACKGROUND

Recently, hyperhomocysteinemia (HHCY) has been suggested as a new risk factor for osteoporosis. This study investigated if HHCY is a causal osteoporotic factor in vivo.

METHODS

We used 3 groups of rats: a control group (n = 20), a moderate HHCY group (induced by a 2.4% methionine-enriched diet, n = 10), and an intermediate HHCY group (induced by a 2% homocystine-enriched diet, n = 10). We measured bone fragility [maximum force of an axial compression test (F(max))], bone area as percentage of total area (BAr/TAr, histomorphometry), and biochemical bone turnover markers [osteocalcin (OC) and collagen I C-terminal crosslaps (CTx)].

RESULTS

Compared with controls, 3 months of moderate or intermediate HHCY increased mean (SD) bone fragility at the femoral neck by 18% (6%) in methionine-fed (P = 0.001) and 36% (13%) in homocystine-fed rats (P <0.001). Mean (SD) BAr/TAr at the distal femur in methionine and homocystine groups was decreased by 45% (21%; P = 0.001) and 93% (9%; P = 0.001), respectively. At the femoral neck, BAr/TAr was decreased by 19% (11%; P <0.001) and 55% (19%; P <0.001). At the lumbar spine, the reduction of BAr/TAr was 17% (23%; P = 0.099) and 44% (19%; P <0.001). Plasma OC (bone formation marker) was decreased by 23% (20%; P = 0.006) and 34% (21%; P <0.001). Plasma CTx (bone resorption marker) did not differ between groups.

CONCLUSION

Bone quality is consistently decreased in the presence of increased circulating homocysteine. The results provide evidence that HHCY is a causal osteoporotic factor.

Neural space and biomechanical integrity of the developing cervical spine in compression

STUDY DESIGN

A factorial study design was used to examine the biomechanical and neuroprotective integrity of the cervical spine throughout maturation using a postmortem baboon model.

OBJECTIVE

To investigate changes with spinal development that affect the neuroprotective ability of the cervical spine in compressive loading.

SUMMARY OF BACKGROUND DATA

Child spinal cord injuries claim and debilitate thousands of children in the United States each year. Many of these injuries are diagnostically and mechanistically difficult to classify, treat, and prevent. Biomechanical studies on maturing spinal tissues have identified decreased stiffness and tolerance characteristics for children compared with adults. Unfortunately, while neurologic deficit typically dictates functional outcome, no previous studies have examined the neuroprotective role of the pediatric cervical spine.

METHODS

Twenty-two postmortem baboon cervical spines across the developmental age spectrum were tested. Two functional spinal unit segments (Oc-C2, C3-C5, and C6-T1) were instrumented with transducers to measure dynamic changes in the spinal canal. These tissues were compressed to 70% strain dynamically, and the resultant mechanics and spinal canal occlusions were recorded.

RESULTS

Classic injury patterns were observed in all of the specimens tested. The compressive mechanics exhibited a significant age relationship (P < 0.0001). Furthermore, while the peak-percent spinal canal occlusion was not age dependent, the percent occlusion just before failure did demonstrate a significant decrease with advancing age (P = 0.0001).

CONCLUSIONS

The neuroprotective ability of the cervical spine preceding failure appears to be age dependent, where the young spine can produce greater spinal canal occlusions without failure than its adult counterpart. The overall percent of the spinal canal occluded during a compression injury was not age dependent; however, these data reveal the neuroprotective ability of the child spine to be more sensitive as an injury predictor than the biomechanical fracture data.

Latent mobility of osteoporotic vertebral compression fractures

PURPOSE

To describe the property of latent mobility in osteoporotic vertebral compression fractures (VCFs) and discuss its clinical significance.

MATERIALS AND METHODS

This was a retrospective case series of 14 patients with 14 painful osteoporotic VCFs who were comfortably confined to the supine position overnight for the purpose of vertebral height restoration. There was sufficient additional vertebral height restoration the following morning to allow percutaneous vertebroplasty (PV) in some patients when this had initially been deemed unsafe or technically impossible. Anterior vertebral height of the index VCF was measured from the preoperative standing lateral, immediate cross-table supine lateral, and postconfinement cross-table supine lateral radiographs as well as the first postoperative standing lateral radiograph. Dynamic mobility was defined as the difference in anterior vertebral height between preoperative standing lateral and immediate cross-table supine lateral radiographs. Latent mobility was defined as difference in anterior vertebral height between immediate cross-table supine lateral and postconfinement cross-table supine lateral radiographs. Postoperative vertebral height restoration was defined as the difference in anterior vertebral height between preoperative and first postoperative standing lateral radiographs. Mean patient age was 81.0 years, and mean fracture age was 83.6 days.

RESULTS

Dynamic mobility averaged +4.7 mm (range, -2.1 to +12.6 mm; P = .001). Latent mobility averaged +2.7 mm (range, -1.9 to +15.5; P < .02). The average sum of preoperative dynamic and latent mobility (+7.4 mm; range -1.0 to +17.0; P < .001) was not different from final postoperative vertebral height restoration (P > .4). PV was successfully accomplished in all cases.

CONCLUSIONS

Latent mobility occurs in some VCFs and contributes to vertebral height restoration. Recognition of latent mobility may permit vertebroplasty in some patients in whom the procedure had otherwise been deemed unsafe. Reports of vertebral height restoration following vertebral augmentation should account for that proportion resulting from dynamic and latent mobility.

Long-term effects of vertebroplasty: adjacent vertebral fractures

In today's aging population, osteoporosis-related fractures are an ever-growing concern. Vertebroplasty, a promising yet cost-effective treatment for vertebral compression fractures, has an increasing role. The first vertebroplasty procedures were reported by Deramond and Galibert in France in 1987, and international interest grew with continued development of clinical techniques and augmentation materials in Europe and the United States. Initial publications and presentations at peer review meetings demonstrated 60-90% success rates in providing immediate and significant pain relief. The objective of this review is to assemble experimental and computational biomechanical research whose goal is determining and preventing the negative long-term effects ofvertebroplasty, with a specific focus on adjacent vertebral fractures. Biomechanical studies using isolated cancellous bone cylinders have shown that osteoporotic cancellous bone samples augmented by the rigid bone cement were at least 12 times stiffer and 35 times stronger than the untreated osteoporotic cancellous bone samples. The biomechanical efficacy of the procedure to repair the fractured vertebrae and prevent further collapse is determined using single-vertebra models. The strength or load-bearing capacity of a single vertebra is significantly increased following augmentation when compared to the intact strength. However, there is no dear result regarding the overall stiffness of the single vertebra, with studies reporting contradictorily that the stiffness increases, decreases, or does not significantly alter following augmentation. The effects of vertebroplasty on adjacent structures are studied via multisegment models, whose results plainly oppose the findings of the single-vertebra and intravertebral models. Here, augmentation was shown to decrease the overall segment strength by 19% when compared to the matched controls. As well, there is a significant increase in disc pressure compared to the pre-augmentation measurements. This translates to a high hydrostatic pressure adjacent to the augmented vertebra, representing the first evidence of increased loading. Computational finite element (FE) models have found that the rigid cement augmentation results in an increase in loading in the structures adjacent to the augmented vertebra. The mechanism of the increase of the loading is predicted to be the pillar effect of the rigid cement. The cement inhibits the normal endplate bulge into the augmented vertebra and thus pressurizes the adjacent disc, which subsequently increases the loading of the untreated vertebra. The mechanism for adjacent vertebral fractures is still unclear, but from experimental and computational studies, it appears that the change in mechanical loading following augmentation is responsible. The pillar effect of injected cement is hypothesized to decrease the endplate bulge in the augmented vertebra causing an increase in adjacent disc pressure that is communicated to the adjacent vertebra. To confirm the viability of the pillar effect as the responsible mechanism, endplate bulge and disc pressure should be directly measured before and after augmentation. Future studies should be concerned with quantifying the current and ideal mechanical response of the spine and subsequently developing cements that can achieve this optimum response.