Reduced loosening rate and loss of correction following posterior stabilization with or without PMMA augmentation of pedicle screws in vertebral fractures in the elderly

Background

Therapy of vertebral fractures in the elderly is a growing challenge for surgeons. Within the last two decades, the use of polymethylmethacrylate (PMMA) in the treatment of osteoporotic vertebral fractures has been widely established. Besides vertebroplasty and kyphoplasty, the augmentation of pedicle screws with PMMA found widespread use to strengthen the implant–bone interface. Several studies showed an enhanced pullout strength of augmented screws compared to standard pedicle screws in osteoporotic bone models. To validate the clinical relevance, we analyzed postoperative radiologic follow-up data in regard to secondary loss of correction and loosening of pedicle screws in elderly patients.

Materials and methods

In this retrospective comparative study, 24 patients admitted to our level I trauma center were analyzed concerning screw loosening and secondary loss of correction following vertebral fracture and posterior instrumentation. Loss of correction was determined by the bisegmental Cobb angle and kyphosis angle of the fractured vertebra. Follow-up computed tomography (CT) scans were used to analyze the prevalence of clear zones around the pedicle screws as a sign of loosening.

Results

In 15 patients (mean age 76 ± 9.3 years) with 117 PMMA-augmented pedicle screws, 4.3 % of screws showed signs of loosening, whereas in nine patients (mean age 75 ± 8.2 years) with 86 uncemented screws, the loosening rate was 62.8 %. Thus, PMMA-augmented pedicle screws showed a significantly lower loosening rate compared to regular pedicle screws. Loss of correction was minimal, despite poor bone quality. There was significantly less loss of correction in patients with augmented pedicle screws (1.1° ± 0.8°) as compared to patients without augmentation (5° ± 3.8°).

Conclusion

The reinforcement of pedicle screws using PMMA augmentation may be a viable option in the surgical treatment of spinal fractures in the elderly.     

Distal radius fracture fixation with volar locking plates and additional bone augmentation in osteoporotic bone: a biomechanical study in a cadaveric model

Background

Fractures of the distal radius represent the most common fractures in adults. Volar locked plating has become a popular method for treating these fractures, but has been subject to several shortcomings in osteoporotic bone, such as loss of reduction and screw purchase. In order to overcome these shortcomings, cement augmentation has been proposed.

Methods

AO-type 23-A3.3 fractures were made in 8 pairs of fresh frozen osteoporotic cadaveric radial bones. All specimens were treated with volar plating, and divided into cement augmentation or non-augmentation groups (n = 8/group). Constructs were tested dynamically and load to failure, construct-stiffness, fracture gap movement and screw cutting distance were measured.

Results

Cement augmentation resulted in a significant increase in cycles and load to failure, as well as construct stiffness at loads higher than 325 N. When compared to the non-augmented group, fracture gap movement decreased significantly at this load and higher, as did screw cutting distance at the holes of the ulnar column. The cycles to failure depend on the BMD in the distal region of the radius.

Conclusion

Cement augmentation improves biomechanical properties in volar plating of the distal radius.     

Does the cement stiffness affect fatigue fracture strength of vertebrae after cement augmentation in osteoporotic patients?

Purpose

Normal progression of osteoporosis or the rigid reinforcement of the fractured vertebral body with polymethyl methacrylate (PMMA) cement is being discussed as a cause for adjacent-level fractures after vertebroplasty. The purpose of this study was to investigate whether augmentation with low stiffness cement can decrease the risk of adjacent-level fractures in low-quality bone.

Methods

Eighteen female osteoporotic lumbar specimens (L1–L5) were harvested and divided into three groups according to bone mineral density: (I) native; (II) PMMA; (III) modified PMMA (lower stiffness). For the PMMA and modified PMMA groups, a compression fracture was first mechanically induced in L3, and then the fracture received vertebroplasty treatment. The cement stiffness reduction of the modified PMMA group was achieved via an addition of 8 mL of serum to the typical PMMA base. All specimens were exposed to cyclic loading (4 Hz) and a stepwise increasing applied peak force. Cement stiffness was tested according to ISO 5833.

Results

A 51 % decrease in cement stiffness was achieved in the modified PMMA group (954 ± 141 vs. 1,937 ± 478 MPa, p < 0.001). Fatigue fracture force (the force level during cyclic loading at which the deformation experienced a sudden increase; FFF) was significantly affected by bone quality (r ² = 0.39, p = 0.006) and by the initial fracture force (the force necessary to create the initial fracture in L3 prior to augmentation; r ² = 0.82, p < 0.001). Using initial fracture force as a covariate, the FFF of the modified PMMA group (1,764 ± 49 N) was significantly higher than in the PMMA group (1,544 ± 55 N; p = 0.03).

Conclusions

A possible method to reduce adjacent-level fractures after vertebroplasty in patients with reduced bone quality could be the use of a lower modulus cement. Therefore, mixing cement with biocompatible fluids could prove useful to tailor cement properties in the operating theater.     

Can MRI predict subsequent pseudarthrosis resulting from osteoporotic thoracolumbar vertebral fractures?

Purpose

The purpose of this study was to assess the ability of short inversion time inversion-recovery (STIR) in magnetic resonance imaging for predicting the prognosis of osteoporotic vertebral fractures.

Methods

We analyzed 63 vertebrae of 56 patients who had osteoporotic vertebral fracture (Th10–L2) prospectively. Image finding of a homogeneous high signal change on a fractured vertebra was evaluated and all vertebrae were divided into “homogenous high signal change group” or “non-homogenous high signal change group”. On the other hand, image finding of linear black signal area was evaluated and all vertebrae were divided into “linear black signal area group” or “non-linear black signal area group”.

Results

Sixteen and 24 vertebrae were included in the homogenous high signal change group or the linear black signal area group, respectively. The 16 homogenous high signal change cases did not result in non-union, and 47 non-homogenous high signal change cases resulted in 14 non-unions, a significant difference. Twenty-four linear black signal area and 39 non-linear black signal area cases resulted in 10, and 4 non-unions, respectively, also a significant difference. The kyphosis progression rate of the linear black signal area group (mean 35 %) was significantly higher than that of non-linear black signal area group (mean 23 %). The visual analog scale of back pain of the linear black signal area group (mean 35 mm) was significantly higher than that of the non-linear black signal area group (mean 23 mm).

Conclusions

STIR was useful for predicting bone union, kyphosis, and back pain in patients with osteoporotic vertebral fracture.     

椎体后凸成形术与椎体成形术生物力学比较

目的比较椎体后凸成形术（KP）与椎体成形术（VP）对骨质疏松性椎体压缩骨折（OVCF）椎体力学性能的影响。方法5具尸体取20个胸腰段骨质疏松单椎体标本,按配对设计,分配为球囊扩张椎体后凸成形术组（KP组）和椎体成形术组（VP组）。经轴向加载压缩25%,制成椎体压缩骨折,记录制成骨折时的最大载荷及刚度数据。KP组将椎体压缩骨折标本行球囊扩张椎体后凸成形术;VP组将椎体压缩骨折标本行椎体成形术。然后将骨水泥强化治疗的椎体再次经万能力学试验机轴向加载,记录治疗后最大载荷及刚度数据。结果KP组和VP组骨折治疗后椎体最大载荷均分别明显高于骨折前（P〈0.01）,而椎体刚度差异无统计学意义（P〉0.05）。KP组与VP组间比较治疗后椎体最大载荷差异无统计学意义（P〉0.05）,椎体刚度差异无统计学意义（P〉0.05）。结论KP和VP均可明显增加OVCF椎体的抗压强度和恢复刚度。     

Augmentation of mechanical properties in osteoporotic vertebral bones – a biomechanical investigation of vertebroplasty efficacy with different bone cements

Recent clinical trials have reported favorable early results for transpedicular vertebral cement reinforcement of osteoporotic vertebral insufficiencies. There is, however, a lack of basic data on the application, safety and biomechanical efficacy of materials such as polymethyl-methacrylate (PMMA) and calciumphospate (CaP) cements. The present study analyzed 33 vertebral pairs from five human cadaver spines. Thirty-nine vertebrae were osteoporotic (bone mineral density < 0.75 g/cm2), 27 showed nearly normal values. The cranial vertebra of each pair was augmented with either PMMA (Palacos E-Flow) or experimental brushite cement (EBC), with the caudal vertebra as a control. PMMA and EBC were easy to inject, and vertebral fillings of 20-50% were achieved. The maximal possible filling was inversely correlated to the bone mineral density (BMD) values. Cement extrusion into the spinal canal was observed in 12% of cases. All specimens were subjected to axial compression tests in a displacement-controlled mode. From load-displacement curves, the stiffness, S, and the maximal force before failure, Fmax, were determined. Compared with the native control vertebrae, a statistically significant increase in vertebral stiffness and Fmax was observed by the augmentation. With PMMA the stiffness increased by 174% (P = 0.018) and Fmax by 195% (P = 0.001); the corresponding augmentation with EBC was 120% (P = 0.03) and 113% (P = 0.002). The lower the initial BMD, the more pronounced was the augmentation effect. Both PMMA and EBC augmentation reliably and significantly raised the stiffness and maximal tolerable force until failure in osteoporotic vertebral bodies. In non-porotic specimens, no significant increase was achieved.     

Influence of the screw augmentation technique and a diameter increase on pedicle screw fixation in the osteoporotic spine: pullout versus fatigue testing

Purpose

For posterior spinal stabilization, loosening of pedicle screws at the bone-screw interface is a clinical complication, especially in the osteoporotic population. Axial pullout testing is the standard pre-clinical testing method for new screw designs although it has questioned clinical relevance. The aim of this study was to determine the fixation strength of three current osteoporotic fixation techniques and to investigate whether or not pullout testing results can directly relate to those of the more physiologic fatigue testing.

Methods

Thirty-nine osteoporotic, human lumbar vertebrae were instrumented with pedicle screws according to four treatment groups: (1) screw only (control), (2) prefilled augmentation, (3) screw injected augmentation, and (4) unaugmented screws with an increased diameter. Toggle testing was first performed on one pedicle, using a cranial-caudal sinusoidal, cyclic (1.0 Hz) fatigue loading applied at the screw head. The initial compressive forces ranged from 25 to 75 N. Peak force increased stepwise by 25 N every 250 cycles until a 5.4-mm screw head displacement. The contralateral screw then underwent pure axial pullout (5 mm/min).

Results

When compared to the control group, screw injected augmentation increased fatigue force (27 %, p = 0.045) while prefilled augmentation reduced fatigue force (?7 %, p = 0.73). Both augmentation techniques increased pullout force compared to the control (ps < 0.04). Increasing the screw diameter by 1 mm increased pullout force (24 %, p = 0.19), fatigue force (5 %, p = 0.73), and induced the least stiffness loss (?29 %) from control.

Conclusions

For the osteoporotic spine, screw injected augmentation showed the best biomechanical stability. Although pullout testing was more sensitive, the differences observed were not reflected in the more physiological fatigue testing, thus casting further doubt on the clinical relevance of pullout testing.     

Minimal-invasive Zementaugmentation von osteoporotischen Wirbelkörperfrakturen mit der neuen Radiofrequenz-Kyphoplastie

Objective

Minimally invasive cement augmentation of painful osteoporotic vertebral compression fractures in elderly patients.

Indications

Painful osteoporotic vertebral compression fractures in elderly patients (>?65 years of age) after conservative therapy failure. Painful aggressive primary tumors of the spine or osteolytic metastases to the spine with high risk of vertebral fracture in the palliative care setting.

Contraindications

General contraindications for surgical interventions. Local soft-tissue infection. Osteomyelitis, discitis or systemic infection. Coagulopathy refractory to treatment or bleeding diathesis. Asymptomatic vertebral compression fractures. Burst of the posterior vertebral column with high degree of spinal canal stenosis. Primary or metastatic spinal tumors with epidural growth.

Surgical technique

Prone position on a radiolucent operating table. Fluoroscopic localization of the fractured vertebra using two conventional C-arm devices (anteroposterior and lateral views). Fluoroscopic localization of the fractured vertebra using two conventional C-arm devices (anteroposterior and lateral views). An introducer is inserted through a small skin incision into the pedicle under fluoroscopic guidance. To create a site- and size-specific three-dimensional cavity in the center of the fractured vertebra, the navigational VertecoR? MidLine Osteotome was inserted through the correctly sited introducer and guided fluoroscopically. As the MidLine Osteotome allows angulation of the tip up to 90° by rotating the handle, a cavity over the midline of the vertebral body can mainly be created through one pedicle. The radiofrequency activated cohesive ultrahigh viscosity PMMA cement (ER² bone cement) is injected stepwise on demand by remote control under continuous pressure from the hydraulic assembly into the vertebral body.

Postoperative management

Bed rest for 6 h postoperatively in supine position. Early mobilization without a corset on the day of surgery. Specific back and abdominal exercises that strengthen the back and abdominal muscles. Pain dependent increase of weight bearing. Continue osteoporosis therapy and start specific drug therapy according to the local guidlines if necessary.

Results

In all, 44 patients (29 women, 15 men) with a mean age of 73.5 years with a total of 62 painful osteoporotic vertebral fractures were treated with RF kyphoplasty from May 2009 until July 2010, and followed over a period of 12 months. The mean operating time per patient was 36.2 min, the operating time per vertebra was 25.7 min. All the patients studied experienced an early and persistent significant pain relief even 12 months after therapy (8?±?1.4 vs. 2.7?±?1.9) according to the visual analogue pain scale. According to the Oswestry Disability Index (ODI) as a disease-specific disability measure all the patients improved significantly (p?相似文献   

Biomechanical evaluation of kyphoplasty and vertebroplasty with calcium phosphate cement in a simulated osteoporotic compression fracture

 Kyphoplasty and vertebroplasty with polymethylmethacrylate (PMMA) have been used for the treatment of osteoporotic vertebral compression fractures. We performed kyphoplasty and vertebroplasty with α-tricalcium phosphate cement (CPC) and PMMA to compare the biomechanical properties. Thirty osteoporotic vertebrae were harvested from nine embalmed cadavers. We randomized the vertebrae into four treatment groups: (1) kyphoplasty with CPC; (2) kyphoplasty with PMMA; (3) vertebroplasty with CPC; and (4) vertebroplasty with PMMA. Prior to injecting the cement, all vertebrae were compressed to determine their initial strength and stiffness. They were then recompressed to determine their augmented strength and stiffness. Although the augmented strength was greater than the initial strength in all groups, there was no significant difference between the two bone cements for either kyphoplasty or vertebroplasty. The augmented stiffness was significantly less than the initial stiffness in the kyphoplasty groups, but the difference between the two cements did not reach significance. In the vertebroplasty groups, the augmented stiffness was not significantly different from the initial stiffness. There was no significant difference between the two bone cements for either procedure when cement volume and restoration of anterior height were assessed. We concluded that kyphoplasty and vertebroplasty with CPC were viable treatment alternatives to PMMA for osteoporotic vertebral compression fractures. Received: July 18, 2002 / Accepted: November 6, 2002 Offprint requests to: S. Tomita     

Intraoperative PEEP-ventilation during PMMA-injection for augmented pedicle screws: improvement of leakage rate in spinal surgery

Background

Within the last two decades the use of polymethylmethacrylate (PMMA) in the treatment of osteoporotic vertebral fractures has been established widely. Several techniques of cement application in spinal surgery have been described. Besides classical vertebroplasty, kyphoplasty and related techniques that reinforce stability of the fractured vertebral body itself, augmentation of pedicle screws became an issue in the past 10 years. Aim of this technique is strengthening of the implant-bone-interface and the prevention of loosening and failure of posterior instrumentation in limited bone quality due to osteoporosis. PMMA use in spinal surgery always bears the risk of cement leakage and cement embolism. There are only few publications dealing with cement leakage in pedicle screw augmentation. We examined our cohort concerning incidence and type of leakage in comparison to the literature. In particular, we evaluated a possible role of intrathoracic pressure during cementation procedure.

Patients and methods

In this retrospective study 42 patients were included. Mean age was 74 (57–89) years. 311 fenestrated, augmented screws were analyzed postoperatively concerning leakage and subsequent pulmonary embolism of cement particles. Overall, there was a leakage rate of 38.3 %, and 28.6 % of patients showed pulmonary embolism of PMMA. During surgery, patients were in part ventilated with a positive end-expiratory pressure (PEEP) of 15 cmH₂O during cement injection. These individuals showed significantly less leakage locally as well as less PMMA-emboli in the pulmonary circulation in contrast to patients ventilated without increased PEEP.

Conclusion

PEEP elevation during administration of PMMA via fenestrated pedicle screws is reducing the leakage rate in spinal surgery. These beneficial effects warrant further evaluation in prospective studies.     

Reconsideration of the relevance of mild wedge or short vertebral height deformities across a broad age distribution

Summary

Based on an evaluation of vertebral fracture prevalence on lateral radiographs across all age groups in a large cohort, mild or wedge-shaped vertebral body changes identified among adults should be managed as osteoporosis or at least considered as a risk factor for osteoporotic fracture, since they are rare among young subjects.

Introduction

Radiographic assessment of vertebral fractures is limited by the inability to distinguish mild fractures from congenital mild wedge deformities or vertebrae of short vertebral height. We attempted to quantify the expected background prevalence of these deformities by measuring vertebral fracture prevalence across all age groups in a large hospital-based retrospective Chinese cohort.

Methods

We reviewed eligible lateral chest radiographs from patients admitted to Peking Union Medical College Hospital during 2011 using the Genant semiquantitative method for vertebral fracture assessment (T4–L2). We evaluated fracture prevalence among subjects by sex, 10-year age group, and fracture severity grades subjectively. We further analyzed characteristics of subjects with mild (grade I) fractures to estimate the relative contribution of congenital mild wedge deformities.

Results

A total of 10,720 subjects (5,396 men and 5,324 women) with lateral chest radiographs were evaluated. Subjects ranged in age from 0.5 to 97 years with a mean of 51.8?±?17.4 years (men 52.8?±?17.6 years; women 50.8?±?17.2 years). When stratified by 10-year age groups, the prevalence of vertebral fractures was relatively low until about 40 years of age, after which prevalence increased for both genders. Fractures (13 fractures for 9 males and 6 fractures for 5 females) seen in subjects younger than 40 years of age were almost exclusively mild grade fractures. No fractures were identified in subjects younger than 20 years of age.

Conclusions

Mild or wedge-shaped vertebral body changes on lateral radiographs are rare among young subjects, indicating that when mild vertebral deformities are found among adults, they are likely to be the product of aging and not congenital variation. Clinically, therefore, mild vertebral body changes should be managed as osteoporosis or at least considered as a risk factor for osteoporotic fracture.     

Adjacent vertebral failure after vertebroplasty. A biomechanical investigation

Vertebroplasty, which is the percutaneous injection of bone cement into vertebral bodies has recently been used to treat painful osteoporotic compression fractures. Early clinical results have been encouraging, but very little is known about the consequences of augmentation with cement for the adjacent, non-augmented level. We therefore measured the overall failure, strength and structural stiffness of paired osteoporotic two-vertebra functional spine units (FSUs). One FSU of each pair was augmented with polymethylmethacrylate bone cement in the caudal vertebra, while the other served as an untreated control. Compared with the controls, the ultimate failure load for FSUs treated by injection of cement was lower. The geometric mean treated/untreated ratio of failure load was 0.81, with 95% confidence limits from 0.70 to 0.92, (p < 0.01). There was no significant difference in overall FSU stiffness. For treated FSUs, there was a trend towards lower failure loads with increased filling with cement (r2 = 0.262, p = 0.13). The current practice of maximum filling with cement to restore the stiffness and strength of a vertebral body may provoke fractures in adjacent, non-augmented vertebrae. Further investigation is required to determine an optimal protocol for augmentation.     

Adjacent vertebral failure after vertebroplasty: a biomechanical study of low-modulus PMMA cement

PMMA is the most common bone substitute used for vertebroplasty. An increased fracture rate of the adjacent vertebrae has been observed after vertebroplasty. Decreased failure strength has been noted in a laboratory study of augmented functional spine units (FSUs), where the adjacent, non-augmented vertebral body always failed. This may provide evidence that rigid cement augmentation may facilitate the subsequent collapse of the adjacent vertebrae. The purpose of this study was to evaluate whether the decrease in failure strength of augmented FSUs can be avoided using low-modulus PMMA bone cement. In cadaveric FSUs, overall stiffness, failure strength and stiffness of the two vertebral bodies were determined under compression for both the treated and untreated specimens. Augmentation was performed on the caudal vertebrae with either regular or low-modulus PMMA. Endplate and wedge-shaped fractures occurred in the cranial and caudal vertebrae in the ratios endplate:wedge (cranial:caudal): 3:8 (5:6), 4:7 (7:4) and 10:1 (10:1) for control, low-modulus and regular cement group, respectively. The mean failure strength was 3.3 ± 1 MPa with low-modulus cement, 2.9 ± 1.2 MPa with regular cement and 3.6 ± 1.3 MPa for the control group. Differences between the groups were not significant (p = 0.754 and p = 0.375, respectively, for low-modulus cement vs. control and regular cement vs. control). Overall FSU stiffness was not significantly affected by augmentation. Significant differences were observed for the stiffness differences of the cranial to the caudal vertebral body for the regular PMMA group to the other groups (p < 0.003). The individual vertebral stiffness values clearly showed the stiffening effect of the regular cement and the lesser alteration of the stiffness of the augmented vertebrae using the low-modulus PMMA compared to the control group (p = 0.999). In vitro biomechanical study and biomechanical evaluation of the hypothesis state that the failure strength of augmented functional spine units could be better preserved using low-modulus PMMA in comparison to regular PMMA cement.     

Is there a stable vertebral height restoration with the new radiofrequency kyphoplasty? A clinical and radiological study

Purpose

The aim of this study is to evaluate whether radiofrequency kyphoplasty can restore vertebral body height in osteoporotic vertebral fractures and whether restoration of vertebral height correlates with decreased pain.

Methods

In a prospective study from December 2010 to October 2011, 25 patients underwent RF kyphoplasty for 30 fresh osteoporotic vertebral fractures. The parameter demographics, pain relief, restoration of vertebral body height (mean vertebral body height, kyphosis angle, anterior/posterior edge height) and all complications were recorded.

Results

Mean age of patients was 73.8 ± 9.6 (range, 55–83); time from initial painful fracture to treatment was 3.0 weeks ± 1.2; average operative time was 23.5 min (range, 15–41). Average pain index score decreased significantly from 69 ± 8.5 preoperatively to 34.4 ± 5.9 postoperatively (p < 0.001), and to 30 ± 6.3 (p < 0.001) after 3 months. Mean vertebral body height, anterior edge height and kyphosis angle showed significant increases postoperatively and at 3-month follow-up (p < 0.05). In two vertebrae (6.6 %), minimal, asymptomatic cement leakage occurred in the upper disc. After 2 months, one new fracture (3.3 %) was identified in the directly adjacent segment that was also successfully treated with radiofrequency kyphoplasty. There was a preliminary correlation between mean vertebral body height elevation and cement volume (r = 0.533).

Conclusion

Radiofrequency kyphoplasty achieves rapid and lasting improvement in clinical symptoms. There was stable restoration of vertebral body height with a mean cement volume of 3.0 ml ± 0.6. There was no correlation between restoration of vertebral body height and pain relief.     

Surgical procedure and initial radiographic results of a new augmentation technique for vertebral compression fractures

Purpose

Recently, a new minimally invasive technique called ‘vertebral body stenting’ (VBS) was introduced for the treatment of osteoporotic vertebral fractures. The technique was developed to prevent the loss of reduction after deflation of the balloon and to reduce the complication rate associated with cement leakage.

Methods

The amount of kyphosis correction, improvement of vertebral body height and quantitative cement leakage rate by applying CT-based quantitative volumetry after VBS were measured in 27 patients (55 vertebra) and compared with a control group (29 patients, 61 vertebrae), which was treated with conventional vertebroplasty.

Results

After VBS, a significant improvement was seen in vertebral height, compared to conventional vertebroplasty. The mean improvement in segmental kyphosis and vertebral kyphosis were 5.8° (p < 0.05) and 3.5° (p < 0.05), respectively. In the VBS group, the mean injected volume of cement per vertebral body was 7.33 cm³ (3.34–10.19 cm³). The average amount of cement outside the vertebrae was 0.28 cm³ (0.01–1.64 cm³), which was 1.36 % of the applied total cement volume. In the vertebroplasty group, the applied mean volume of the cement per level was 2.7 cm³ (1–5.8 cm³) and the average amount of cement outside the vertebrae was 0.15 cm³ (0.01–1.8 cm³), which was 11.5 % (0.2–60 %) of the applied total volume of cement.

Conclusion

The frequency of cement leakage after VBS was 25.5 % compared to 42.1 % in the vertebroplasty group. VBS led to a significant decrease in the leakage rate compared with conventional vertebroplasty.     

Treatment of multiple osteoporotic vertebral compression fractures by percutaneous cement augmentation

Purpose

Vertebral compression fractures cause significant pain and some patients are debilitated by the pain due to the fracture. Conventional surgery carries a high risk and has a poor outcome. Vertebroplasty is a minimally invasive surgical procedure, which in vertebral fractures restores stability and diminishes pain. The aim of the study was to analyse the effectiveness and safety of vertebroplasty in multiple vertebral compression fractures with a 24-month follow-up.

Methods

Vertebroplasty was performed in 160 patients with multiple osteoporotic compression fractures under local anaesthesia, using a unilateral transpedicular approach. The level of pain was assessed according to a 10-cm visual analogue scale. The patients were observed for 24 months after surgery.

Results

Vertebroplasty significantly diminished the level of pain in 90 % of patients, and half of them were free of pain within 12 hours after surgery. Only 4 % of the patients did not benefit from this type of treatment. During the 24-month follow-up these results changed only slightly, and after two years almost 80 % still benefited, while the number of unsatisfactory results changed from 6 to 9 %. No serious clinical complications were noted; in three patients new fractures appeared during the two year observation period.

Conclusions

Vertebroplasty should be seriously taken into account as a primary method of treatment in patients with multiple osteoporotic vertebral compression fractures.     

Locally measured microstructural parameters are better associated with vertebral strength than whole bone density

Summary

Whole vertebrae areal and volumetric bone mineral density (BMD) measurements are not ideal predictors of vertebral fractures. We introduce a technique which enables quantification of bone microstructural parameters at precisely defined anatomical locations. Results show that local assessment of bone volume fraction at the optimal location can substantially improve the prediction of vertebral strength.

Introduction

Whole vertebrae areal and volumetric BMD measurements are not ideal predictors of vertebral osteoporotic fractures. Recent studies have shown that sampling bone microstructural parameters in smaller regions may permit better predictions. In such studies, however, the sampling location is described only in general anatomical terms. Here, we introduce a technique that enables the quantification of bone volume fraction and microstructural parameters at precisely defined anatomical locations. Specific goals of this study were to investigate at what anatomical location within the vertebrae local bone volume fraction best predicts vertebral-body strength, whether this prediction can be improved by adding microstructural parameters and to explore if this approach could better predict vertebral-body strength than whole bone volume fraction and finite element (FE) analyses.

Methods

Eighteen T12 vertebrae were scanned in a micro-computed tomography (CT) system and FE meshes were made using a mesh-morphing tool. For each element, bone microstructural parameters were measured and correlated with vertebral compressive strength as measured experimentally. Whole bone volume fraction and FE-predicted vertebral strength were also compared to the experimental measurements.

Results

A significant association between local bone volume fraction measured at a specific central region and vertebral-body strength was found that could explain up to 90 % of the variation. When including all microstructural parameters in the regression, the predictive value of local measurements could be increased to 98 %. Whole bone volume fraction could explain only 64 % and FE analyses 76 % of the variation in bone strength.

Conclusions

A local assessment of volume fraction at the optimal location can substantially improve the prediction of bone strength. Local assessment of other microstructural parameters may further improve this prediction but is not clinically feasible using current technology.     

应用新型Vessel-X骨材料填充器注射聚甲基丙烯酸甲酯的实验研究

目的 探讨新型Vessel-X骨材料填充器对注射聚甲基丙烯酸甲酯(PMMA)在椎体内分布影响及对椎体力学性能的修复效果.方法 将新鲜冰冻人椎体标本14个随机分单侧穿刺和双侧穿刺组.每组7椎.测量各标本的骨密度、前后缘和中线高度以及原始刚度和强度后,建立压缩骨折模型.测量骨折后标本的高度和剐度.应用Vessel-X骨材料填充器注射PMMA后再次测量椎体的高度、强度和刚度.观察填充器在椎体内的膨胀情况及PMMA在椎体内的分布情况.结果 两组椎体术后的强度均较原始大,但术后强度比较差异无统计学意义.两组椎体术后刚度较骨折后水平均有恢复,双侧组较单侧组刚度恢复效果好.术后椎体各部位的高度均增加,但未恢复到原始高度水平.术后两组椎体中线两侧的高度差比较差异无统计学意义.轴位透视下见骨水泥在椎体内呈椭圆形或长椭圆形分布,与填充器在体外膨胀后的形状相似.横断标本后,见填充器能在椎体内良好膨胀,包裹绝大部分PMMA,仅少量PMMA渗漏到网层外,但均局限在网层周围.结论 Vessel-X骨材料填充器在椎体标本内能包裹绝大部分PMMA,可防止骨水泥渗漏,且能恢复骨折椎体的力学性能和高度.     

Vertebral deformities and fractures are associated with MRI and pQCT measures obtained at the distal tibia and radius of postmenopausal women

Summary

We investigated the association of postmenopausal vertebral deformities and fractures with bone parameters derived from distal extremities using MRI and pQCT. Distal extremity measures showed variable degrees of association with vertebral deformities and fractures, highlighting the systemic nature of postmenopausal bone loss.

Introduction

Prevalent vertebral deformities and fractures are known to predict incident further fractures. However, the association of distal extremity measures and vertebral deformities in postmenopausal women has not been fully established.

Methods

This study involved 98 postmenopausal women (age range 60–88 years, mean 70 years) with DXA BMD T-scores at either the hip or spine in the range of ?1.5 to ?3.5. Wedge, biconcavity, and crush deformities were computed on the basis of spine MRI. Vertebral fractures were assessed using Eastell's criterion. Distal tibia and radius stiffness was computed using MRI-based finite element analysis. BMD at the distal extremities were obtained using pQCT.

Results

Several distal extremity MRI and pQCT measures showed negative association with vertebral deformity on the basis of single parameter correlation (r up to 0.67) and two-parameter regression (r up to 0.76) models involving MRI stiffness and pQCT BMD. Subjects who had at least one prevalent vertebral fracture showed decreased MRI stiffness (up to 17.9 %) and pQCT density (up to 34.2 %) at the distal extremities compared to the non-fracture group. DXA lumbar spine BMD T-score was not associated with vertebral deformities.

Conclusions

The association between vertebral deformities and distal extremity measures supports the notion of postmenopausal osteoporosis as a systemic phenomenon.     

Biomechanical comparative study of the stability of injectable pedicle screws with different lateral holes augmented with different volumes of polymethylmethacrylate in osteoporotic lumbar vertebrae

Background Context

Polymethylmethacrylate (PMMA) is widely used for pedicle screw augmentation in osteoporosis. Until now, there had been no studies of the relationship between screw stability and the distribution and volume of PMMA.