Proceedings of the NASS 20th Annual Meeting / The Spine Journal 5 (2005) 1S–189S 17S

in 8/10 cases when comparing preoperative to preprocedure (positional)and 10/15 cases comparing preprocedure to postprocedure (procedural).Cobb angle showed improvement in 7/10 and 10/15 and Post Ang 6/10and 9/15 respectively. When we arbitrarily assigned an improvement of 5degrees as being clinically significant, positional improvement occurred in7/10 using the Cobb method and 6/10 with Post Ang. As results of indexvertebral measurements, average absolute height restoration at anteriorvertebra was 6.4 mm by positioning, 10 mm by bone tamp, 13 mm by cementdeposition. Vertebral height was restored more by bone tamp inflation(p�.0040) and cement deposition (p�.0007) compared with positioningonly. The restored vertebral height over just positioning was maintainedon the postoperative X-ray (p�.0001); however, vertebral height at postop-erative standing X-ray was decreased from the time of bone tamp inflation(p�.0007) and cement deposition (p�.0022). Restored vertebral heightwas greater at anterior vertebra compared with middle (p�.0156) andposterior (p�.0001).CONCLUSIONS: Height restoration improvement appears to occur bothwith positioning and procedure during the kyphoplasty procedure. It appearsthat bone tamp inflation and cement deposition restore height beyond whatcan be achieved by positioning alone.DISCLOSURES: FDA device/drug: Kyphoplasty. Status: Approved forthis indication.CONFLICT OF INTEREST: Author (DT) Consultant: Good ClinicalPractice 8-1-2-3; Consultant for Kyphoplasty project in Japan; Authors(DT, IHL) Grant Research Support: Kyphon Inc., Sunnyvale, CA.; Author(JAG) Other: Received an educational grant from Synthes Spine, Paoli,PA; Author (RS) Speaker’s Bureau Member: Kyphon Inc., Sunnyvale, CA.;Author (IHL) Consultant: Kyphon Inc., Sunnyvale, CA.

doi: 10.1016/j.spinee.2005.05.033

4:0532. Structural bioactive hydrogels for injectable vertebralfracture repairsEmily Ho, Anthony Lowman, Michele Marcolongo; Drexel University,Philadelphia, PA, USA

BACKGROUND CONTEXT: During vertebroplasty or kyphoplasty, po-lymethylmethacrylate (PMMA) bone cement is injected into the fracturedvertebral body to relieve pain and to restore its mechanical integrity. More-over, 26% of kyphoplasty cases reported subsequent vertebra fractureswhich resulted from modulus mismatch between pmMA (1-3 GPa) andtrabecular bone (0.05 GPa). Recently, bioactive bone cements are ap-plied. These materials offer osteoconductivity allowing in vivo bone in-growth, but their moduli are even higher than pmMA.PURPOSE: We proposed an injectable material with osteoconductivitywhich has an optimized modulus for vertebra fracture fixations. Thisstudy assesses the feasibility of using a thermoreversible injectable polymeras the fixation material.STUDY DESIGN/SETTING: A bioactive component was engineeredinto the macromolecular structure to facilitate the formation of calciumphosphate nucleation sites on a thermo-sensitive polymer, poly(N-isopro-pylacrylamide)-co-poly(ethyleneglycol) dimethacrylate (PNIPAAm-PEGDM), through incorporation of tri-methacryloxypropyltri-methoxysilane(MPS). PNIPAAm-PEGDM is capable of liquid to solid phase transforma-tion at 32�XC, thus enabling the material to be injected as a liquid at roomtermperatureandsolidify into firm,solid hydrogel atbody temperature. In thisstudy, we evaluated the liquid to solid phase transformation temperature(LCSTs) and the in vitro mechanical properties, swelling characteristics,and bioactivity in different immersion media of the polymers.PATIENT SAMPLE: N/A.OUTCOME MEASURES: N/A.METHODS: PNIPAAm-PEGDM solutions were prepared with differingMPS concentrations to determine the effect of crosslinking agent on theinjectability, mechanical behavior after immersion in different physiologicalsolutions, swelling characteristics, and bioactivity of the hydrogel polymer.

RESULTS: Ease of injection through a 20 gauge needle was accomplishedwith MPS concentrations of 0.01 molar ratio or less with a consistenttransition temperature of 32�C. The addition of MPS encouraged calciumphosphate formation thoughout the gel thickness. MPS also contributed toincreased modulus of the material, likely the result of the condensation ofsilanol which forms siloxane serving to cross-link the polymer backbone(Fig. 1). Swelling properties of the gels also varied with immersion media,although the differences were less pronounced for the MPS-containingsystems. As compared with PBS, immersion in SBF served to enhance thebioactivity reactions as well as increase the mechanical properties, evenafter 5 days of immersion in vitro. The challenge of this material systemis to balance the network-forming and bioactivity-inducing MPS with thegain in elastic recovery induced by PEGDM addition to the PNIPPAmbase, all while maintaining an injectable material system.

Fig. 1. In vitro elastic modulus of the hydrogels after 5 days of immersionin PBS and SBF.

CONCLUSIONS: PNIPAAm-PEGDM crosslinked with MPS are bonebonding systems that have a wide range of mechanical properties whichmay be tuned for use in vertebral fracture repair.DISCLOSURES: No disclosures.CONFLICT OF INTEREST: No conflicts.

doi: 10.1016/j.spinee.2005.05.034

4:1133. Cement leakage in percutaneous vertebroplasty: effect ofpreinjection gelfoam embolizationChandra Bhatia, MD, Manoj Krishna, FRCS, Tai Friesem, MD,Raymond Pollock, PhD; University Hospital of North Tees, Stockton onTees, Cleveland, United Kingdom

BACKGROUND CONTEXT: Percutaneous vertebroplasty has been usedpreviously in pain relief for vertebral fractures due to malignancy andosteoporosis. However, extravertebral cement extrusion is a commonproblem and can lead to complications.PURPOSE: To determine the safety, feasibility and effectiveness of routinepreinjection of gelatin clotting agent in reducing cement leakage duringpercutaneous vertebroplasty. The aim was to determine if routine gelfoamembolization will reduce extravertebral cement leakage. Reducing cementleakage will reduce the morbidity and mortality associated with theprocedure.STUDY DESIGN/SETTING: Prospective case series.PATIENT SAMPLE: Thirty-one patients who met the inclusion-exclusioncriteria were entered into the study, which covered the period August 2001to August 2004. Inclusion criteria were: -Severe back pain of at least 8weeks not responding to oral anti-imflammatory/opioid treatment. -Localtenderness at the levels identified from imaging studies. -Desire to pursue asurgical treatment option. -A magnetic resonance image showing a vertebral

Proceedings of the NASS 20th Annual Meeting / The Spine Journal 5 (2005) 1S–189S18S

VCFs using vertebroplasty technique at three centers (20 patients) andkyphoplasty technique at five centers (20 patients). Treatment was limited toone or two levels from T6 to L5. The objective was to compare thepatients’ condition prior to and after treatment, with each patient beingtheir own control.PATIENT SAMPLE: Twenty patients were treated using the Verte-broplasty technique. There were 8 males and 12 females with a mean age of72. 15 lumbar and 11 thoracic vertebrae were treated, with an averageof 1.9 cc injected per vertebra. Twenty patients were treated using theKyphoplasty technique. There were 6 males and 14 females with a meanage of 79. Twenty-five vertebrae were treated with an average of 4.1 ccper vertebra.OUTCOME MEASURES: Primary endpoints included pain (Visual Ana-logue Scale, VAS) and function (Oswestry Disability Index, ODI), radio-graphic evaluation, and safety.METHODS: Patients meeting the inclusion/exclusion criteria were admit-ted into the study. Each study was run independently of the other; that is,there was no randomization between groups.RESULTS: Vertebroplasty: Average pain improved by a reduction in theVAS, from 74.1 preoperatively to 24.1 at 3 months, 28 at 6 months, and32 at 12 months. Similarly, disability improved from a mean ODI scoreof 52% preoperatively to a mean score of 30% at 3 months and a meanscore of 23% at 12 months. Kyphoplasty: Average pain improved by areduction in the VAS, from 54 preoperatively to 22 at 3 months and 36at 6 months. Similarly, disability improved from a mean ODI score of 60%to a mean score of 33% at 3 months and a mean score of 35% at 6 months.Leakages, which were carefully analyzed on postoperative CT scans (1-mmcuts), were similar in both groups and easily detected due to the radiopacityof Cortoss. In both the Vertebroplasty and kyphoplasty groups, extravasa-tions were all anatomically close to the vertebra and asymptomatic. Nocardiac irregularities or pulmonary emboli were observed.CONCLUSIONS: The results obtained in these two pilot IDE studiesindicate that Cortoss is safe and effective in the treatment of osteoporoticVCF. The reductions in VAS pain scores are consistent with those reportedin the litterature using PMMA. The results are also consistent with thoseobtained in the prospective vertebroplasty study using Cortoss conductedin Europe. These studies suggest that a smaller volume of Cortoss appearsto successfully reinforce the vertebrae and achieve symptomatic relief,as compared with the volumes reported in the literature for PMMA. Thismay be due to the interdigitated fill pattern observed with Cortoss whichresults in trabecular reinforcement. A larger, prospective randomized con-

compression fracture. Exclusion criteria were: -Nerve root compression.-Neurological deficit. -Infection.OUTCOME MEASURES: The primary outcome measure of cement leak-age was assessed postoperatively using radiographs and computed tomogra-phy. The secondary outcome measure of pain relief was assessed verbally byasking patients to subjectively describe their pain at 8 weeks post-procedure.METHODS: Thirty-six patients underwent percutaneous vertebroplasty.Venography was first performed to determine the flow pattern in the verte-brae and confirm needle placement. Next, routine gelfoam embolization ofvenous channels was performed. The gelatin sponge was cut into fine pieces(1–2 mm square) and transferred to a 20-ml syringe and attached to oneend of a 3-way valve. Another 20-ml syringe containing saline and contrastmedia was attached at right angles to the other valve and the gelatin spongesuspended by repeatedly mixing the contents of the two syringes. The finalsuspension was aspirated into one of the syringes ready for injection.This was followed by low pressure mimimal volume cement injection.Aproximately 2–3 ml of vertebroplasty was injected under fluoroscopicguidance.RESULTS: There were no complications in the 31 patients (24 females,7 males, mean age at treatment 71.5 years; age range 52–87 years). Sixty-one levels of vertebroplasty were performed. Cement leakage occurred at16 levels in 12 patients (26.3%). Five of the leaks (31.3%) were in patientswith fractures due to neoplasms. At 8 levels leakage was into the adjoiningdisc, leakage anteriorly was seen at 3 levels, and there were 2 cases ofleakage into the paravertebral tissues. There were 3 occurrences of epiduralleakage (4.9%), 1 via the venous system and 2 through a cortical defect.None of the leakages were symptomatic. Thirty patients (97%) were ableto be followed up at 8 weeks. All but one patient reported total or nearcomplete pain relief and this was maintained in those patients (14 patients,45%) who were able to be followed up in the long term (mean follow-up8.4 months).CONCLUSIONS: Gelfoam embolization together with careful techniquecan reduce venous cement leakage in vertebroplasty. Complications due tocement leakage are the most feared side effect of the procedure. This hasresulted in only limited application of vertebroplasty. We hope by routinelyusing preinjection gelfoam embolization the technique will be morewidely used.DISCLOSURES: No disclosures.CONFLICT OF INTEREST: No conflicts.

doi: 10.1016/j.spinee.2005.05.035

4:1734. Characteristics and clinical experience using a novel bioceramicfor treating vertebral compression fractures in vertebroplasty andkyphoplasty: report on the first 40 patientsHyun Bae, MD1, Philip Maurer, MD2, Walter Peppelman, MD3,William Beutler, MD3, Raymond Linovitz, MD4, Erik Westerlund4,Timothy Peppers4, Isador Lieberman, MD, MBA, FRSC (C)5,Choll Kim, MD, PhD6, Federico Girardi, MD7; 1St. John’s HealthCenter, Santa Monica, CA, USA; 2Pennsylvania Hospital, Philadelphia,PA, USA; 3Pennsylvania Spine Institute, Harrisburg, PA, USA;4Encinitas, CA, USA; 5Cleveland Clinic Foundation, Cleveland,OH, USA; 6University of California–San Diego, San Diego, CA, USA;7Hospital for Special Surgery, New York, NY, USA

BACKGROUND CONTEXT: Cortoss is a high-strength, bioactive, self-setting composite engineered to mimic the characteristics of human struc-tural bone. Because it is inherently radiopaque, Cortoss is easily visualizedduring its placement under fluoroscopy, or in postoperative imaging. Animalstudies demonstrated that the Cortoss-bone interface continues to bestrengthened over time, with new bone being formed and integrated ontoand into the material.PURPOSE: To assess the feasibility and clinical outcome of the use ofCortoss in treating osteoporotic vertebral compression fractures (VCF).STUDY DESIGN/SETTING: Forty patients were enrolled in two FDAapproved pilot IDE studies conducted using Cortoss for the treatment of

trolled IDE study to confirm these findings is under way.DISCLOSURES: FDA device/drug: Cortoss. Status: Investigational/notapproved.CONFLICT OF INTEREST: Author (HB) Grant Research Support:Orthovita.

doi: 10.1016/j.spinee.2005.05.036

4:2335. Vertebral compression fracture reconstruction: amulti-center studyStefano Boriani1, Reuven Gepstein2, Ilya Pekarsky3, Yoram Fulman4,Wolfgang M. Franck5; 1Maggiore Hospital, Bologna, Italy; 2Meir MC,Kfar Sava, Israel; 3Meir MC, Israel; 4Hillel Yaffe MC, Israel;5Cuxhaven Hospital GmbH, Germany

BACKGROUND CONTEXT: A novel expandable device was used toreconstruct fractured vertebral bodies by means of a minimally invasivetechnique. The SKy Bone Expander System is a 4-mm-diameter polymertube that following axial pressure, radially expands up to 16 mm indiameter. The concept enables percutaneous positioning of the device in itsreduced form under local or general anesthesia, and its contraction andremoval once vertebral reconstruction is achieved. The device creates adefined cavity, which enables paste-like bone cement injection instead ofliquiform injection with standard vertebroplasty techniques. Several implantsizes are available.