Percutaneous vertebroplasty: history, technique and current perspectives

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.

Investigating sacroplasty: technical considerations and finite element analysis of polymethylmethacrylate infusion into cadaveric sacrum

BACKGROUND AND PURPOSE

Sacroplasty is not as routinely performed as vertebroplasty, possibly due to technical challenges and the paucity of data regarding subsequent outcomes. The first goal of the present investigation was to describe a technique for sacroplasty that facilitates safe needle placement and polymethylmethacrylate (PMMA) extrusion. The second goal was to perform finite element analysis (FEA) by using a geometric model of sacral fracture to identify mechanical outcomes of sacroplasty.

MATERIALS AND METHODS

Sacroplasty was performed on fresh pelvis specimens (n=4) under biplane fluoroscopy. Cadavers were imaged via CT before and after sacroplasty and volume rendered to examine needle placement and PMMA extrusion. The volume-rendered CT data were then used to generate geometric models of the intact, fractured, and cement-augmented fractured sacrum for comparison by using FEA.

RESULTS

CT data demonstrate that safe injection needle placement and PMMA delivery may be facilitated by orienting the needle parallel to the L5-S1 interspace and ipsilateral sacroiliac joint, then targeting the superolateral sacral ala within an area bounded by a line lateral to the posterior foraminal openings and a line superimposed on the medial edge of the sacroiliac joint. FEA revealed that simulated sacroplasty decreased maximal principal stress at the point of sacral fracture propagation by 83% and fracture gap micromotion by 48%.

CONCLUSION

Sacral landmarks can be used to place PMMA safely where sacral fractures occur. FEA suggests that sacroplasty may decrease fracture-associated mechanical stress and micromotion, which may contribute to patient reports of decreased pain and increased mobility postsacroplasty.

Vertebroplasty and kyphoplasty

Vertebral compression fractures occur more frequently than hip and ankle fractures combined. These fragility fractures frequently result in both acute and chronic pain, but more importantly are a source of increased morbidity and possibly mortality. Percutaneous vertebral augmentation offers a minimally invasive approach for the treatment of vertebral compression fractures. The history, technique, and results of vertebroplasty and kyphoplasty are reviewed. Both methods allow for the introduction of bone cement into the fracture site with clinical results indicating substantial pain relief in approximately 90% of patients.

Vertebroplasty in the treatment of osteoporotic vertebral body fracture

During the last few years, vertebroplasty has gained a wide acceptance for the treatment of painful osteoporotic vertebral body fractures and osteolytic changes. However, new guidelines with significant changes in indications and technique were published recently in Europe. Therefore, the aim of this review is to highlight recent changes in indications for vertebroplasty, patient work-up and changes in procedural technique, and to give an overview of patient outcome and possible complications. Therefore, technical details like different types of fluoroscopy, needle placement, pain management during the intervention, recommended equipment, including bone cement, and the use of venography are discussed. Postprocedural issues are noted, including the risk of minor and major complications and the expected outcome of the treated patients.

Percutaneous vertebroplasty and kyphoplasty for the stand-alone augmentation of osteoporosis-induced vertebral compression fractures: Present status and future directions

Enormous research efforts are being expended on two minimally invasive procedures: percutaneous vertebroplasty (VP) and kyphoplasty (KP). The present report, which is a detailed critical review of VP and KP that emphasizes their biomechanics aspects, is divided into six parts. In the first two parts, succinct descriptions are given of osteoporosis-induced vertebral body (VB) compression fractures as the underlying pathology to be treated with VP and KP, the theory of VP and KP, and the techniques used in performing these procedures. Concerns about VP and KP, such as the high radiation exposure burden that may be imposed on both patient and medical personnel and extravasation of the injectable bone cement, are discussed in the third part. Detailed discussions of fourteen issues/questions, such as the extent to which VP or KP affects various biomechanical measures of the augmented VB and those adjacent to it and the appropriate volume of the cement to use, are presented in the fourth part. Ideas for future research, such as development of a new generation of injectable bone cements and identification of an appropriate animal model, are covered in the fifth part. The final section contains a summary of the most salient points/observations made in the report.

Evaluation of an injectable bone substitute (betaTCP/hydroxyapatite/hydroxy-propyl-methyl-cellulose) in severely osteopenic and aged rats

The use of injectable biomaterials is of interest in osteoporotic patients to locally restore bone mass in sites at risk of fracture. An injectable bone substitute (IBS1 made of betaTCP/hydroxyapatite as a calcium phosphate substitute and hydroxy-propyl-methyl-cellulose as a polymer carrier) was used in a severely osteopenic rat model obtained by combining orchidectomy (ORX) and disuse (paralysis induced by botulinum toxin - BTX). Fifty-six aged male rats were randomized into three groups: 18 were SHAM operated; 38 were ORX and BTX injected in the right hindlimb; they constituted the OP (osteoporotic) group. One month after ORX-BTX surgery, 20 of these OP rats received a IBS1 injection in the right femur (OP-IBS1 rats). Animals were studied at the time of IBS1 injection 1 month post ORX-BTX (M1), 1 month (M2) and 2 months (M3) after IBS1 injection. Bone mass (BV/TV) and microarchitectural parameters were measured by microCT. BV/TV was decreased after ORX-BTX; ORX and BTX had cumulative effects on bone loss (differences maximized on the right femur). BV/TV (combining the volume of both bone and material in OP-IBS1 rats) was elevated at M1 but decreased at M2. Marked bone formation was found onto the biomaterial granules but bone had a woven texture. A marked increase in the number of nonosteoclastic TRAcP+ cells was found in the implanted area. IBS1 induced new bone formation shortly after implantation but both IBS1 and woven bone were resorbed without inducing lamellar bone. Biomaterial trials must be conducted with long-term implantation periods, in aged osteoporotic animals.

Cold defect on bone scan in a vertebral body after percutaneous vertebroplasty

Percutaneous vertebroplasty using bone cements is increasingly being used to stabilize osteoporotic spinal compression fractures. Although the scintigraphic appearance of compression fractures has been well-described, the post-vertebroplasty bone scan appearance has not. This case report describes a characteristic cold defect of a vertebral body after percutaneous vertebroplasty.

Femoroplasty--augmentation of the proximal femur with a composite bone cement--feasibility, biomechanical properties and osteosynthesis potential

BACKGROUND

Analogous to vertebroplasty, cement-augmentation of the proximal femur ("femoroplasty") could reinforce osteoporotic bones. This study was to evaluate (i) the feasibility of femoroplasty with a composite cement (Cortoss), (ii) its influence on femoral strength by mechanical testing and (iii) the feasibility of stable osteosynthesis of the augmented fractured bones.

METHODS

Nine human cadaveric femora were augmented with a composite bone cement, the surface heat generation monitored, and then tested biomechanically against their native contralateral control to determine fracture strength. Subsequently, thirteen reinforced and fractured femora were osteosynthetized by different implants and tested against their osteosynthetisized, non-augmented contralateral control.

FINDINGS

Cement could be injected easily, with a moderate temperature rise. A positive correlation between BMD and fracture load and a significant increase in fracture load (+43%) of the augmented femora compared to their native controls (6324 N and 4430 N, respectively) as well as a significant increase in energy-to-failure (+187%, 86 N m and 30 N m, respectively) was found. Osteosynthesis was possible in cement-augmented femora. Osteosynthetisized femora showed equivalent strength to the intact controls.

INTERPRETATION

Augmentation of the proximal femur with composite bone cement could be of use in prophylaxis of fractures in osteoporotic femurs. Osteosynthesis of the fractured augmented bones is a challenging procedure but has a good chance to restore strength.

[Computed tomography of the musculoskeletal system]

Computed tomography (CT) is an important diagnostic modality in the work-up of musculoskeletal diseases. Just as projection radiography and magnetic resonance imaging, it has specific possible uses. As a tool to guide interventional and surgical procedures, it is a significant imaging technique. The technical development of multislice spiral CT in recent years has contributed considerably to increasing the diagnostic quality of CT. In particular, the possibilities for depicting the findings with methods for secondary image reconstruction have been decidedly improved.

Leakage of Polymethylmethacrylate in Percutaneous Vertebroplasty

OBJECTIVE

We compared polymethylmethacrylate (PMMA) leakage from vertebral bodies in osteoporotic compression fractures with and without intravertebral vacuum clefts (IVCs) on computed tomography (CT) after vertebroplasty.

METHODS

Percutaneous vertebroplasty was performed in 59 patients, comprising 36 compression fractures with IVCs in 33 patients and 49 fractures without IVCs in 26 patients. All patients underwent postprocedural CT of treated and adjacent vertebral bodies. CT findings and clinical complications were assessed retrospectively with regard to the presence of PMMA leakage. When present, leakage types were classified as intradiscal, epidural, foraminal, and perivertebral venous. The frequencies and types of leakages were compared in both groups using chi and Fisher exact tests, respectively.

RESULTS

The PMMA leakage occurred in 20 (55.5%) of 36 fractures with IVCs and in 25 (51.0%) of 49 fractures without IVCs, without significant difference (P=0.679). No patients experienced clinical complications. The leakage types that frequently occurred were intradiscal (13/20, 65.0%), perivertebral venous (5/20, 25%), epidural (1/20, 5%), and foraminal (1/20, 5%) in compression fractures with IVCs; and epidural (11/25, 44.0%), intradiscal (6/25, 24%), and perivertebral venous (8/25, 32%) in those without. A significant difference was found between the most frequent types in both groups (P=0.006, P=0.003, respectively).

CONCLUSIONS

On CT after vertebroplasty, the incidences of PMMA leakage in osteoporotic compression fractures with and without IVCs were similar; however, leakage type frequencies differed.

Preparation of acrylic bone cements for vertebroplasty with bismuth salicylate as radiopaque agent

One of the problems of percutaneous vertebroplasty attributed to the use of acrylic cements is related to the radiopacity of the formulation. The use of bismuth salicylate as the radiopaque agent is proposed in this work, taking into account the high radiopacity of organobismuth compounds used in dental applications and the possible analgesic effect of salicylic acid. Various cements formulated with this compound (some of them modified with polyethylene oxide) were examined. Setting parameters, mechanical properties, rheological behaviour, injectability, radiopacity and biocompatibility were studied for a variety of formulations, showing that the cement formulations containing bismuth salicylate have a higher radiopacity and better injection properties than commercial bone cement preparations and present good mechanical properties.

Influence of powder particle size distribution on complex viscosity and other properties of acrylic bone cement for vertebroplasty and kyphoplasty

For use in vertebroplasty and kyphoplasty, an acrylic bone cement should possess many characteristics, such as high radiopacity, low and constant viscosity during its application, low value of the maximum temperature reached during the polymerization process (T(max)), a setting time (t(set)) that is neither too low nor too high, and high compressive strength. The objective of this study was to investigate the influence of the powder particle distribution on various properties of one acrylic bone cement; namely, residual monomer content, T(max), t(set), complex viscosity, storage and loss moduli, injectability, and quasi-static compressive strength and modulus. It was found that the formulations that possessed the most suitable complex viscosity-versus-mixing time characteristics are those in which the ratio of the large poly(methyl methacrylate) beads (of mean diameter 118.4 microm) to the small ones (of mean diameter 69.7 microm) was at least 90% w/w. For these formulations, the values of the other properties determined were acceptable.

Percutaneous Vertebroplasty in Octogenarians: Results and Follow-Up

OBJECTIVES

To determine pain relief, performance status, morbidity, and mortality associated with percutaneous vertebroplasty for spinal pain in patients aged 80 years and older.

DESIGN

Prospective, descriptive, third-party independent interview, clinical audit.

SETTING

University Hospital, Geneva, Switzerland.

PARTICIPANTS

Patients aged 80 years and older who underwent vertebroplasty between August 1997 and August 2004 because of vertebral fractures from osteoporotic or malignant etiologies.

METHODS

Primary outcome measures were verbal rating scale (VRS) (0--no pain, 5--intolerable) and Eastern Cooperative Oncology Group (ECOG) performance status scale (0--normal activity, 4--unable to get out of bed) before and after procedure. Patients were interviewed 8 to 35 months post treatment (mean 25), independently assessed for pain relief, analgesic consumption, and overall satisfaction by using the American Society of Anesthesiologists (ASA) Outcome Measures questionnaire.

RESULTS

Mean VRS scores significantly decreased from 4.86 +/- 0.64 to 2.39 +/- 1.14 (P < 0.05), and mean ECOG performance scores improved from 1.87 +/- 0.97 to 1.29 +/- 1.06 (P < 0.05) after treatment. When patients were analyzed by etiology (group 1--cancer; group 2--osteoporosis), both groups significantly reduced their VRS (P < 0.05); however, only group I significantly improved their performance (P < 0.05; P = 0.334, respectively). Nine patients answered the ASA questionnaire (18 deceased, 1 demented, 1 lost to follow-up) and reported an improvement in their ability to perform daily tasks. No early or late complications were observed; none of the deaths were procedure-related.

CONCLUSIONS

Percutaneous vertebroplasty is a safe, minimally invasive, well-tolerated analgesic procedure among octogenarians suffering from spinal pain, permitting increased activities of daily living. Pain reduction is significant regardless of the etiology; performance scores are significantly improved in cancer pain.

Kyphosis reduction and the rate of cement leaks after vertebroplasty of intravertebral clefts

To assess the results of vertebroplasty in patients with intravertebral clefts compared to patients with normal osteoporotic fractures, we evaluated the pre- and postoperative images and pain scores (VAS) of 114 patients with 192 vertebroplasty procedures treated between March 2002 and February 2005. Intravertebral clefts were identified on conventional radiographs, MR or CT images as gas- or fluid-filled spaces adjacent to an endplate of a fractured vertebra. Forty-four vertebrae showed intravertebral clefts. All clefts were filled with PMMA showing a typical filling pattern. Due to the prone positioning of the patient during vertebroplasty, a significant reduction of the kyphosis angle was achieved in the cleft group. Cement leakage occurred in 18.2% of clefts and 46% of regular osteoporotic fractures. In all patients, good filling of the cleft was achieved no matter where the needle tip was placed in the vertebra. The VAS score was 9.1 preoperatively, 3.6 before discharge and 3.9 6 months postoperatively, showing no significant difference between both groups. Patients with intravertebral clefts show a significant reduction of the kyphosis angle compared to non-cleft patients and have a significantly lower risk of experiencing cement leakage during vertebroplasty. Pain reduction is the same in both groups.

Histopathologic findings of retrieved specimens of vertebroplasty with polymethylmethacrylate cement: case control study

STUDY DESIGN

Case control study.

OBJECTIVE

To investigate the histopathologic findings of 2 retrieved specimens from failed vertebroplasty with polymethylmethacrylate (PMMA) cement.

SUMMARY OF BACKGROUND DATA

Vertebroplasty using PMMA cement has been commonly used to treat debilitating back pain from compression fracture, angiomas, and metastatic cancer. However, there was concern about the unpredictable future results with PMMA cement. The histopathologic changes were rarely reported.

METHODS

There were 2 PMMA augmented and 3 nonaugmented fractured vertebral bodies retrieved for histopathologic study. Between the 2 groups, we compared the findings of bone necrosis, foreign body reaction, fibrotic wall formation, and neovascularization.

RESULTS

Bone necrosis was noted in the periphery of PMMA cement, which was surrounded by fibrotic tissues. In contrast, no fibrotic wall formation could be found in the nonaugmented control group. Foreign body reaction was only noted in PMMA augmented cases, and neovascularization was only noted in the control cases.

CONCLUSION

PMMA cement might not be as bioinert as we considered. Therefore, the long-term safety of vertebroplasty should be further evaluated.

Percutaneous vertebroplasty: An update

Percutaneous vertebroplasty is an imaging-guided interventional technique in which surgical polymethylmethacrylate is injected via a large bore needle into a painful compressed vertebral body. This technique is safe and effective, and provides increased strength and pain relief in vertebrae weakened by bone diseases. Among the current indications for vertebroplasty are intractable nonradicular pain caused by compression fractures due to osteoporosis, myeloma, metastasis, and aggressive vertebral hemangioma. Contraindications include bleeding disorder, unstable fracture, and lack of definable vertebral collapse. The preprocedural evaluation, technique, complications, and expected results of performing this procedure are also reviewed.

Intraoperative three-dimensional fluoroscopy-based computerized tomography guidance for percutaneous kyphoplasty

Object

Percutaneous kyphoplasty is an established method for the treatment of pathological vertebral compression fractures (VCFs). This procedure is usually performed with the aid of biplanar fluoroscopic image guidance. There are currently no published clinical studies in which the use of three-dimensional (3D) image guidance to facilitate this technique has been evaluated. The purpose of this study was to evaluate the efficacy of isocentric fluoroscopy-based navigation for the kyphoplasty procedure, with special reference to operating time and the amount of radiation exposure.

Methods

A prospective clinical study was performed in which 11 consecutive patients with painful pathological VCFs that did not respond to conservative treatment underwent the kyphoplasty procedure. During this procedure, cannulation of the pedicle and vertebral body was performed with the aid of isocentric 3D fluoroscopy visualization. Total operating time and intraoperative fluoroscopy time for this group was compared with a cohort of nine patients who underwent the procedure prior to the availability of isocentric fluoroscopy (only biplanar fluoroscopy was used). Possible complications such as cement extravasations were evaluated during the procedure and on postoperative computerized tomography scans.

The mean duration of surgery for the 3D isocentric fluoroscopic guidance group was 60 minutes (range 36–89 minutes) for one-level and 68.5 minutes (range 65–75 minutes) for two-level cases. Because of a learning curve with the equipment, the operating time for the initial cases was significantly longer than with the later ones. Even with the initial cases included, the mean operating time was shorter compared with the biplanar fluoroscopy-assisted procedures, which averaged 69.2 minutes (range 44–113 minutes) for one-level procedures. This difference was not statistically significant. The mean fluoroscopy exposure time was 41.3 seconds (range 25–62 seconds) in the isocentric fluoroscopy-assisted procedures, with an additional 40 seconds of fluoroscopy time used for the 3D fluoroscopy “spin,” compared with 293.2 seconds (range 180–400 seconds) in the biplanar fluoroscopy-assisted procedures. The difference was statistically significant (p = 0.02). All pedicles were accessed without difficulty and no complications were encountered in either group of patients.

Conclusions

The main advantage of isocentric fluoroscopy is the significant reduction in radiation exposure for the patient and surgical staff without an increase in the mean operating time. This technique is a significant advancement over biplanar fluoroscopy in this setting.

Vertebroplasty and kyphoplasty: rapid pain relief for vertebral compression fractures

Vertebroplasty and kyphoplasty are minimally invasive procedures aimed at relieving symptoms associated with vertebral compression fractures. They have become accepted, highly effective, safe procedures, and are known for their high patient satisfaction rates. Although they are image-guided percutaneous spine therapies, differences do exist. They have each arisen from different backgrounds and are championed by different subspecialties and each involves slightly different techniques. In addition, a prospective, randomized trial comparing the two techniques has yet to be performed. This lack of objective data allows market forces and opinions to have a large influence on utilization and patient referral.