Objectives. Although vertebroplasty is very effective for relieving acute pain from an osteoporotic vertebral compression fracture, not all patients who undergo vertebroplasty receive the same degree of benefit from the procedure. In order to identify the ideal candidate for vertebroplasty, pre-operative prognostic demographic or clinico-radiological factors need to be identified. The objective of this study was to identify the pre-operative prognostic factors related to the effect of vertebroplasty on acute pain control using a cohort of surgically and non-surgically managed patients. Patients and Methods. Patients with single-level acute osteoporotic vertebral compression fracture at thoracolumbar junction (T10 to L2) were followed. If the patients were not satisfied with acute pain reduction after a three-week conservative treatment, vertebroplasty was recommended. Pain assessment was carried out at the time of diagnosis, as well as three, four, six, and 12 weeks after the diagnosis. The effect of vertebroplasty, compared with conservative treatment, on back pain (visual analogue score, VAS) was analysed with the use of analysis-of-covariance models that adjusted for pre-operative VAS scores. Results. A total of 342 patients finished the 12-week follow-up, and 120 patients underwent vertebroplasty (35.1%). The effect of vertebroplasty over conservative treatment was significant regardless of age, body mass index, medical comorbidity, previous fracture, pain duration, bone mineral density, degree of vertebral body compression, and canal encroachment. However, the effect of vertebroplasty was not significant at all time points in patients with increased sagittal vertical axis. Conclusions. For single-level acute osteoporotic vertebral compression fractures, the effect of vertebroplasty was less favourable in patients with increased sagittal vertical axis (> 5 cm) possible due to aggravation of kyphotic stress from walking imbalance. Cite this article: Y-C. Kim, D. H. Bok, H-G. Chang, S. W. Kim, M. S. Park, J. K. Oh, J. Kim, T-H. Kim. Increased sagittal vertical axis is associated with less effective control of acute pain following vertebroplasty. Bone Joint Res 2016;5:544–551. DOI: 10.1302/2046-3758.511.BJR-2016-0135.R1

Abstract. Objectives. To evaluate the safety and efficacy of vertebroplasty with short segmented cement augmented pedicle screws fixation for severe osteoporotic vertebral compression fractures (OVCF) with posterior/anterior wall fractured patients. Methods. A retrospective study of 24 patients of DGOU type-4 (vertebra plana) OVCF with posterior/anterior wall fracture, were treated by vertebroplasty and short segment PMMA cement augmented pedicle screws fixation. Radiological parameters (kyphosis angle and compression ratio) and clinical parameters Visual analogue scale (VAS) and Oswestry disability index (ODI) were analysed. Results. A significant improvement was noted in VAS (preoperative, 7.90 ± 0.60; final follow-up 2.90 ± 0.54) and ODI (77.10 ± 6.96 to 21.30 ± 6.70), (P < 0.05). Neurological improvement was noted in all patients. Kyphosis corrected significantly from preoperative 23.20 ± 5.90 to 5.30 ± 1.40 postoperative with 5% (3.30 ± 2.95) loss of correction at final follow-up. Anterior vertebral height restored significantly from 55.80 ± 11.9% to 87.6 ± 13.1% postoperative with 4.5 ± 4.0% loss at final follow-up. One case had cement leakage was found, but the patient is asymptomatic. No implant-related complication was seen. No iatrogenic dural or nerve injury. Conclusions. Treatment with vertebroplasty with cement augmented screw fixation and direct decompression is a great option in treating such a complex situation in fragile age with fragile bones because. Vertebroplasty is viable option for restoring vertebral anterior column in patients who are considered as contraindications for vertebroplasty, like DGOU-4. It provides anterior support avoiding corpectomy, minimise blood loss and also duration of surgery. Addition of short segment fixation gives adequate support with less stress risers at the junctional area

Royal Liverpool University Hospital, Liverpool, UK. To retrospectively review outcomes in patients who underwent vertebroplasty in Liverpool in response to recent level 1 publications claiming vertebroplasty to be no better than sham procedure assessed using 2 criteria. We reviewed cases between 2006 and 2009 looking at 5 criteria for procedure. Visual Analogue Score (VAS). Oswestry disability index scores (ODI). 96 patients identified. 10 patients excluded (inadequate data recorded) (n=86). Operated levels n=134 (thoracic n=61, lumbar n=71, sacral n=2). Presenting symptoms included back pain (86/86) and point tenderness was present in 90% (77/86). Average length of symptoms was 11.50 months with 28% reporting greater than 12 months. 72% recalled definite onset of symptoms with 90% being associated with a low velocity injury. Radiological findings showed an average of 54% height collapse and 91% showing high signal on STIR MRI sequences. Number of levels operated – 3 or more (n=9 VAS 5.3 ODI 10.6); 1 to 2 levels (n= 77 VAS 3.7 ODI 13.9). Average improvement in VAS score was 3.8.and ODI 13.6. 47% (40/86) of patients met all 5 current criteria recommended for operation (VAS 3.7, ODI 14). 53% (46/86) of patients met 2-5 criteria (VAS 3.8, ODI 13.4). There was improvement in pain scores in 91% of patients with an average pre-op VAS 7.8 and post-op VAS 4.0. There was no significant difference in patients meeting all 5 criteria compared to those meeting 2-5 criteria

Abstract. Objectives. The principle of osteoporotic vertebral compression fracture (OVCF) is fixing instability, providing anterior support, and decompression. Contraindication for vertebroplasty is anterior or posterior wall fracture. The study objectives was to evaluate the efficacy and safety of vertebroplasty with short segmented PMMA cement augmented pedicle screws for OVCF with posterior/anterior wall fracture patients. Methods. A retrospective study of 24 patients of DGOU type-4 (vertebra plana) OVCF with posterior/anterior wall fracture, were treated by vertebroplasty and short segment PMMA cement augmented pedicle screws fixation. Radiological parameters (kyphosis angle and compression ratio) and clinical parameters Visual analogue scale (VAS) and Oswestry disability index (ODI) were analysed. Results. A significant improvement was noted in VAS (preoperative, 7.90 ±0.60; final follow-up 2.90 ± 0.54) and ODI (77.10 ± 6.96 to 21.30 ± 6.70), (P < 0.05). Neurological improvement was noted in all patients. Kyphosis corrected significantly from preoperative 23.20±5.90 to 5.30±1.40 postoperative with 5% (3.30± 2.95) loss of correction at final follow-up. Anterior vertebral height restored significantly from 55.80±11.9% t0 87.6±13.1% postoperative with 4.5±4.0% loss at final follow-up. One case had cement leakage was found, but the patient is asymptomatic. No implant-related complication was seen. No iatrogenic dural or nerve injury. Conclusions. Treatment with vertebroplasty with cement augmented screw fixation and direct decompression is a great option in treating such a complex situation in fragile age with fragile bones because It provides anterior support with cementing that avoids corpectomy. Short segment fixation has less stress risers at the junctional area

Purpose of the study: To determine if cement type, bone mineral density (BMD), disc degeneration and fracture severity influence the restoration of spinal load-sharing following vertebroplasty. Methods: Fifteen pairs of thoracolumbar motion-segments (51–91 yrs) were loaded to induce fracture. Vertebroplasty was performed so that one of each pair was injected with Cortoss, the other with Spineplex. Specimens were then creep loaded at 1.0kN for 2 hours. At each stage of the experiment, stress” profiles were obtained by pulling a pressure-sensitive needle through the disc whilst under 1.5kN load. From these profiles, the intradiscal pressure (IDP), posterior stress peaks (SP. P. ), and neural arch compressive load (F. N. ) were determined. BMD was measured using dual photon X-ray absorptiometry. Severity of fracture was quantified from height loss. Results: Fracture reduced IDP (p< 0.001) but increased SP. P. and F. N. (p< 0.001). Following vertebroplasty, these effects were significantly reversed, and in most cases persisted after creep-loading. However, no differences were observed between PMMA- and Cortoss-injected specimens. After fracture, decreases in IDP, and increases in SP. P. and F. N. , were greater in specimens with lower BMD or greater height loss (p< 0.05). After vertebroplasty, specimens with lower BMD showed greater increases in IDP, and those with more degenerated discs showed greater reductions in SP. P. (p< 0.05). Conclusions: Changes in spinal load-sharing following fracture were partially restored by vertebroplasty, and this effect was independent of cement type. The effects of fracture and vertebroplasty were influenced by BMD, disc degeneration, and fracture severity. People with more severe fractures, low BMD and degenerated discs may gain most mechanical benefit from vertebroplasty

Introduction: Cement augmentation of osteoporotic vertebral fractures by vertebroplasty can alleviate pain, although the mechanism remains unknown. We hypothesise that vertebral fracture reduces loading by the vertebral body, and that vertebroplasty reverses this effect. Methods: Nineteen thoracolumbar motion segments (64 – 90 yrs) were used. Specimens were compressed at 1.5kN in moderate flexion and extension while intradis-cal stress profiles were obtained by pulling a miniature pressure transducer along the mid-sagittal diameter of the disc (. 1. ). Vertebral fracture was induced by compressive overload in moderate flexion. Vertebroplasty was then performed by injecting polymethylmethacry-late cement into the anterior vertebral body. Stress profiles were repeated after fracture, and after vertebroplasty. Stress concentration in the annulus was calculated by subtracting the nuclear pressure from the maximum stress in the annulus. Neural arch compressive load was obtained by subtracting the disc compressive force, calculated by integrating intradiscal stress over area, from the applied 1.5kN (. 1. ). Results: Fracture increased the stress concentration in the annulus from 0.21 to 0.58MPa in flexion (p< 0.01) and from 0.02 to 0.20MPa in extension (p< 0.05). It also increased neural arch load bearing from 9% to 27% of the applied load in flexion (p< 0.01), and from 53% to 70% in extension (p< 0.01). Following vertebroplasty, these changes were largely reversed: in flexion, stress concentrations in the annulus decreased to 0.36MPa and neural arch load-bearing fell to 5% (p< 0.01). Similar, non-significant trends were observed in extension. Discussion: Vertebral fracture reduces load-bearing by the vertebral body, and increased compressive loading of the neural arch. Vertebroplasty goes some way to reversing these effects, and significantly decreased stress concentration in the annulus and loading of the neural arch in flexion. This could contribute to pain relief in patients undergoing this procedure

Introduction. Vertebral osteoporotic fracture increases both elastic and time-dependent ('creep') deformations of the fractured vertebral body during subsequent loading. The accelerated rate of creep deformation is especially marked in central and anterior regions of the vertebral body where bone mineral density is lowest. In life, subsequent loading of damaged vertebrae may cause anterior wedging of the vertebral body which could contribute to the development of kyphotic deformity. The aim of this study was to determine whether gradual creep deformations of damaged vertebrae can be reduced by vertebroplasty. Methods. Fourteen pairs of spine specimens, each comprising three vertebrae and the intervening soft tissue, were obtained from cadavers aged 67-92 yr. Specimens were loaded in combined bending and compression until one of the vertebral bodies was damaged. Damaged vertebrae were then augmented so that one of each pair underwent vertebroplasty with polymethylmethacrylate cement, the other with a resin (Cortoss). A 1kN compressive force was applied for 1 hr before fracture, after fracture, and after vertebroplasty, while creep deformation was measured in anterior, middle and posterior regions of each vertebral body, using a MacReflex optical tracking system. Results. Cement type had little influence on creep deformation, so data from all 28 specimens were pooled. After fracture, creep in the anterior vertebral body increased from 4,513 (STD 4766) to 54,107 (STD 54,845) microstrains (P<0.001), and creep in the central region of the vertebral body increased from 885 (STD 5,169) to 34,378 (STD 40,762) microstrain (P<0.001). (10,000 microstrains = 1% deformation.) Following vertebroplasty, creep deformations were reduced by 61% (P=0.002) and 66% (P=0.006) in anterior and central regions respectively. Conclusion. Creep deformations of the anterior and central regions of vertebral bodies increase markedly as a result of fracture but are then reduced by vertebroplasty. In life, vertebroplasty could help to slow or prevent the gradual development of kyphotic deformity following vertebral osteoporotic fracture, as well as increase vertebral stiffness and strength

Introduction: Vertebroplasty increases stiffness and partly restores normal load-sharing in the human spine following vertebral fracture. The present study investigated whether the mechanical effects of vertebroplasty are influenced by the distribution of injected cement. Methods: Ten pairs of cadaver motion segments (58–88 yr) were loaded to induce fracture, after which one from each pair underwent vertebroplasty with polymethyl-methacrylate cement, the other with a resin (Cortoss). Various mechanical parameters were measured before fracture, after fracture and following subsequent vertebroplasty. Micro-computed tomography scans and plane radiographs (sagittal, frontal, and axial) obtained from each augmented vertebral body were analysed to determine percentage cement fill in the whole vertebral body and in selected regions. The relationship between volumetric fill obtained by micro-CT and areal fill obtained by radiography was investigated using linear regression analysis. Regression analysis also indicated whether changes in mechanical parameters following vertebroplasty were dependent upon cement distribution. Results: Cement type had no significant influence upon regional fill patterns, so data from both cements were pooled for all subsequent analyses. Volumetric fill of the whole vertebral body was predicted best by areal fill in the sagittal plane (R2=0.366, P=0.0047). Restoration of intradiscal pressure and compressive stiffness following vertebroplasty were dependent upon volumetric cement fill both in the whole vertebral body (R2=0.304, P=0.0118 and R2=0.197, P=0.0499 respectively), and in the anterior half (R2=0.293, P=0.0137 and R2=0.358, P=0.0053). Conclusion: Cement fill patterns can best be assessed radiographically from sagittal plane views. Placement of cement in the anterior vertebral body may help to improve mechanical outcome following vertebroplasty

To investigate whether restoration of mechanical function and spinal load-sharing following vertebroplasty depends upon cement distribution. Fifteen pairs of cadaver motion segments (51-91 yr) were loaded to induce fracture. One from each pair underwent vertebroplasty with PMMA, the other with a resin (Cortoss). Various mechanical parameters were measured before and after vertebroplasty. Micro-CT was used to determine volumetric cement fill, and plane radiographs (sagittal, frontal, and axial) to determine areal fill, for the whole vertebral body and for several specific regions. Correlations between volumetric fill and areal fill for the whole vertebral body, and between regional volumetric fill and changes in mechanical parameters following vertebroplasty, were assessed using linear regression. For Cortoss, areal and volumetric fills were significantly correlated (R=0.58-0.84) but cement distribution had no significant effect on any mechanical parameters following vertebroplasty. For PMMA, areal fills showed no correlation with volumetric fill, suggesting a non-uniform distribution of cement that influenced mechanical outcome. Increased filling of the vertebral body adjacent to the disc was associated with increased intradiscal pressure (R=0.56, p<0.05) in flexed posture, and reduced neural arch load bearing (F. N. ) in extended posture (R=0.76, p<0.01). Increased filling of the anterior vertebral body was associated with increased bending stiffness (R=0.55, p<0.05). Cortoss tends to spread evenly within the vertebral body, and its distribution has little influence on the mechanical outcome of vertebroplasty. PMMA spreads less evenly, and its mechanical benefits are increased when cement is concentrated in the anterior vertebral body and adjacent to the intervertebral disc

Introduction. Vertebral osteoporotic fracture increases both elastic and time-dependent (‘creep’) deformations of the fractured vertebral body during subsequent loading. This is especially marked in central and anterior regions of the vertebral body, and could explain the development of kyphotic deformity in life. We hypothesise that vertebroplasty can reduce these creep deformations. Methods. Twelve pairs of spine specimens, each comprising three vertebrae and the intervening soft tissue, were obtained from cadavers aged 67-92 yr. They were compressed to failure, after which one of each pair underwent vertebroplasty with polymethylmethacrylate cement, the other with a resin (Cortoss). A 1kN compressive force was applied for 1 hour before fracture, after fracture, and after vertebroplasty, while creep deformation was measured in the anterior, middle, and posterior region of each vertebral body using a MacReflex optical tracking system. Results. Cement type had little influence on creep deformation, so data from all 24 specimens were pooled. After fracture, creep in the anterior vertebral body increased from 4,863 (STD 5060) to 57,674 (STD 57,663) microstrains (P<0.001), and creep in the central vertebral body increased from 738 (STD 5,643) to 37,025 (STD 43,519) microstrain (P<0.001). Vertebroplasty reduced creep deformations by 67% (P=0.002) and 66% (P=0.011) in the anterior and central regions respectively. Conclusion. Vertebroplasty reduces progressive creep deformations of a fractured vertebral body. These findings suggest that vertebroplasty may slow or prevent the development of kyphotic deformity following vertebral osteoporotic fracture

Introduction: To evaluate whether a biologically-active cement “Cortoss” confers any short-term mechanical advantages when compared with a polymethylmethacrylate bone cement “Spineplex” which is currently in widespread use. Methods: Two thoracolumbar motion segments were harvested from each of six spines (51 – 82 yrs). Specimens were compressed to failure in moderate flexion to induce vertebral fracture. Pairs of specimens were randomly assigned to undergo vertebroplasty with either Cortoss or Spineplex. Compressive stiffness and compressive stress on the disc were measured before and after fracture, and after vertebroplasty. Compressive stress was measured by pulling a pressure- sensitive needle through the mid-sagittal diameter of the disc whilst under 1.5kN load. Intradiscal pressure (IDP), peak stress in the annulus and neural arch compressive load were obtained from the resulting stress profiles. Results: No differences in IDP, annulus stress, neural arch load bearing and compressive stiffness were observed between the groups before fracture, after fracture or after vertebroplasty (p> 0.05). After fracture, IDP decreased from 1.02 to 0.68 MPa in flexion and from 0.75 to 0.34 MPa in extension (p< 0.05), neural arch load bearing increased from 13% to 37% of the applied load in flexion (p< 0.05), and compressive stiffness decreased from 2441 to 1478 N/mm (p< 0.05). After vertebroplasty, these changes were largely reversed: IDP increased to 0.45 MPa in extension (p< 0.05), neural arch load bearing fell to 20% in flexion (p=0.1), and compressive stiffness increased to 1799 N/mm (p< 0.05). Conclusion: Vertebroplasty using either Cortoss or Spineplex was equally effective in reversing fracture-induced changes in motion segment mechanics

Background. Fracture of an osteoporotic vertebral body reduces vertebral stiffness and decompresses the nucleus in the adjacent intervertebral disc. This leads to high compressive stresses acting on the annulus and neural arch. Altered load-sharing at the fractured level may influence loading of neighbouring vertebrae, increasing the risk of a fracture ‘cascade’. Vertebroplasty has been shown to normalise load-bearing by fractured vertebrae but it may increase the risk of adjacent level fracture. The aim of this study was to determine the effects of fracture and subsequent vertebroplasty on the loading of neighbouring (non-augmented) vertebrae. Methods. Fourteen pairs of three-vertebra cadaver spine specimens (67-92 yr) were loaded to induce fracture. One of each pair underwent vertebroplasty with PMMA, the other with a resin (Cortoss). Specimens were then creep loaded at 1.0kN for 1hr. In 17 specimens where the upper or lower vertebra fractured, compressive stress distributions were measured in the disc between adjacent non-fractured vertebrae by pulling a pressure transducer through the disc whilst under 1.0kN load. These ‘stress profiles’ were obtained at each stage of the experiment (in flexion and extension) in order to quantify intradiscal pressure (IDP), the size of stress concentrations in the posterior annulus (SP) and compressive load-bearing by anterior (FA) and posterior (FP) halves of the vertebral body and by the neural arch (FN). Results. No differences were found between Cortoss and PMMA so all data were pooled. Following fracture, IDP fell by 26% in extension (P=0.004) and SP increased by more than 200% in flexion (P=0.01). FA decreased from 55% to 36% of the applied load in flexion (P=0.002) and from 36% to 27% in extension (P=0.002). FN increased from 17% to 31% in flexion (P=0.006) and from 22% to 37% in extension (P=0.008). Vertebroplasty reduced stress concentrations in the disc and restored load-bearing towards pre-fracture values. Conclusion. Vertebral fracture transfers compressive load from the anterior vertebral body to the posterior vertebral body and neural arch of adjacent (non-fractured) vertebrae. Vertebroplasty largely restores normal load-sharing at both the augmented and adjacent levels and in doing so may help reduce the risk of a spinal fracture cascade

Introduction Vertebroplasty and kyphoplasty have been gaining popularity for treating vertebral fractures. Current reviews provide an overview of the procedures but are not comprehensive and tend to rely heavily on personal experience. This paper aimed to compile all available data and evaluate the clinical outcome of the two procedures. The objective was to evaluate the safety and efficacy of vertebroplasty and kyphoplasty using the data presented in published clinical studies, with respect to patient pain relief, restoration of mobility and vertebral body height, complication rate, and incidence of new adjacent vertebral fractures. Methods This is a systematic review of all the available data presented in peer reviewed published clinical trials (69 papers). Where possible a quantitative aggregation of the data was performed. Data was collected for each study under the headings: general information, participants, intervention, outcomes, complications, and follow-up. Outcome data was collected detailing: pain relief, general health, functional improvements, satisfaction with treatment, and reduction in kyphosis. Complications included: cement leakage (asymptomatic and symptomatic), neurological deficits, cardiovascular, pulmonary and any other clinically relevant complication. Long term follow-up information included all the items recorded under the heading “outcome” with the addition of new fracture details. Results A large proportion of subjects experienced some pain relief (87% vertebroplasty, 92% kyphoplasty). Vertebral height restoration was possible using kyphoplasty (average 6.6°) and for a subset of patients using vertebroplasty. Cement leaks occurred for 41% and 9% of treated vertebrae for vertebroplasty and kyphoplasty respectively. New fractures of adjacent vertebrae occurred for both procedures at rates that are greater than the general osteoporotic population but approximately equivalent to the general osteoporotic population that had a previous vertebral fracture. Discussion The pain relief experienced by patients is promising for both kyphoplasty and vertebroplasty in the short term (< 1 year). Leakage of the PMMA is the most common complication and may pose significant danger. Higher leakage rates have been reported for vertebroplasty studies compared to kyphoplasty studies. Particularly kyphoplasty has the ability to reduce the kyphotic angle and restore vertebral height. The critical factor for the restoration of vertebral height would appear to be fracture age

Numerous studies have examined the biomechanical properties of the vertebral body following PMMA cement augmentation for the treatment of osteoporotic vertebral body fractures. To date there is no published literature reporting the effects of Vertebroplasty on internal intervertebral disc biomechanics which in turn have been shown to reflect loading patterns of the vertebral column. To study effects of PMMA cement augmentation of vertebral body fractures on intervertebral disc biomechanics using stress prolifometry to assess differential anterior and posterior vertebral column loading. Eight cadaveric motion segments were individually loaded on a hydraulically powered materials testing machine under 1.5kN of axial compression. Following fracture induction the lower vertebral body underwent Vertebroplasty. Profiles of the vertically acting compressive stress were obtained by pulling a pressure sensitive transducer along the mid-sagittal diameter of the intervertebral disc. “Stress profile” measurements were obtained before fracture, following fracture, and after vertebro-plasty both in extension and flexion. Stress profiles were integrated over area to calculate the compressive force across the disc. The compressive load acting on the neural arch was calculated by subtracting the disc force from the applied 1.5kN load. In flexed postures posterior column loading increased from 17.1% to 42.2% following fracture (p< 0.01) and then decreased significantly from 42.2% to 23.68% following vertebroplasty (p< 0.03). There was no significant difference between pre-fracture and post-vertebroplasty status (p=0.11). In extended posture, fracture produced increased posterior column loading 72.9% vs 51.8% (p< 0.005) and following vertebroplasty there was no significant change (p=0.2). In moderate degrees of flexion, vertebroplasty produces normalisation of load bearing through the anterior vertebral column and hence offloads the posterior elements to a significant degree. This could be postulated, to partly account for the analgesic effect seen following vertebroplasty in the clinical setting

Introduction. Osteoporotic fracture reduces vertebral stiffness, and alters spinal load-sharing. Vertebroplasty partially reverses these changes at the fractured level, but is suspected to increase deformations and stress at adjacent levels. We examined this possibility. Methods. Twelve pairs of three-vertebra cadaver spine specimens (67-92 yr) were loaded to induce fracture. One of each pair underwent vertebroplasty with PMMA, the other with a resin (Cortoss). Specimens were then creep-loaded at 1.0kN for 1hr. In 15 specimens, either the uppermost or lowest vertebra was fractured, so that compressive stress distributions could be determined in the disc between adjacent non-fractured vertebrae. Stress was measured in flexion and extension, at each stage of the experiment, by pulling a pressure-transducer through the disc whilst under 1.0kN load. Stress profiles quantified intradiscal pressure (IDP), stress concentrations in the posterior annulus (SP. P. ), and compressive load-bearing by the neural arch (F. N. ). Elastic deformations in adjacent vertebrae were measured using a MacReflex tracking system during 1.0kN compressive ramp loading. Results. No differences were found between Cortoss and PMMA so data was pooled. Following fracture, IDP fell by 27% in extension (P=0.009), and SP. P. increased by 277% in flexion (P=0.016). F. N. increased from 17% to 30% of the applied load in flexion, and from 23% to 37% in extension (P<0.05). Vertebroplasty partially reversed these changes without inducing any increase in elastic deformation of the adjacent vertebrae. Conclusion. Vertebral fracture increases stress concentrations acting on the vertebral bodies and neural arches of adjacent (non-fractured) vertebrae, and these increases can be partially reversed by vertebroplasty

Introduction: Kyphoplasty is a modification of the basic vertebroplasty technique used to treat osteoporotic vertebral fracture. This study evaluated whether kyphoplasty conferred any short-term mechanical advantage when compared with vertebroplasty. Methods: Pairs of thoracolumbar “motion segments” were harvested from nine spines (42–84 yrs). Specimens were compressed to failure in moderate flexion to induce vertebral fracture. One of each pair underwent vertebroplasty, the other kyphoplasty. Specimens were then creep loaded at 1.0kN for 2 hours to allow consolidation. At each stage of the experiment, motion segment stiffness in bending and compression was determined, and the distribution of compressive “stress” was measured in flexed and extended postures by pulling a pressure- sensitive needle through the mid-sagittal diameter of the disc whilst under 1.5kN load. Stress profiles indicated the intradiscal pressure (IDP), stress peaks in the posterior annulus (SPP), and neural arch compressive load-bearing (FN). Results: Vertebral fracture reduced bending and compressive stiffness by 37% and 55% respectively (p< 0.0001), and IDP by 55%–83%, depending upon posture (p< 0.001). SPP increased from 0.188 to 1.864 MPa in flexion, and from 1.139 to 3.079 MPa in extension (p< 0.05). FN increased from 13% to 37% of the applied load in flexion, and from 29% to 54% in extension (p< 0.001). Vertebroplasty and kyphoplasty partially reversed these changes, and their immediate mechanical effects were mostly sustained after creep-loading. No differences were found between vertebroplasty and kyphoplasty. Conclusion: Kyphoplasty and vertebroplasty are equally effective in reversing fracture-induced changes in motion segment mechanics. In the short-term, there is no mechanical advantage associated with kyphoplasty

Vertebroplasty is a minimal invasive technique in the management of osteoporotic vertebral fractures. Clinical and biomechanical investigations could show the strengthening effect of the unipedicular injection of osteoporotic vertebral bodies using different materials. Little is known about the distribution of the inhected material and the resulting biomechanical outcome. The present study was designed with the focus on investigating both, the biomechanical behaviour and the cement distribution in augmentation of osteoporotic vertebrae using the vertebroplasty technique. 40 osteoporotic vertebral bodies were injected unipedicular with an amount of 6ml of two different PMMA bone cements (Vertebroplastik/DePuy; Simplex/Stryker-Howmedica-Osteonics). Strength and stiffness were measured during axial compression. For the investigation of the cement distribution, two sections of each injected vertebral body were cut, digitally imaged and analysed by an image processing software using a specially developed procedure. The augmentation with Vertebroplastik bone cement resulted in a significant increased failure load compared to control. The use of both cements showed a significant increased resistance to further compression fractures. For the Vertebroplastik bone cement a significant better flow to the centre of the vertebral body was observed. Vertebroplasty of osteoporotic vertebral bodies by using Vertebroplastik and Simplex PMMA bone cement results in significant increased failure load and resistance to further compression under laboratory conditions. The investigation of the cement distribution showed a significant better spreading of the Vertebroplastik bone cement to the centre of the vertebral body. From the experimental point of view we recommend the augmentation of osteoporotic vertebral bodies to prevent further collapse

Summary. Time-lapsed CT offers new opportunities to predict the risk of cement leakage and to evaluate the mechanical effects on a vertebral body by monitoring each incremental injection step in an in-vitro vertebroplasty procedure. Introduction. Vertebroplasty has been shown to reinforce weak vertebral bodies and to prophylactically reduce fracture risks. However, bone cement leakage is a major vertebroplasty related problem which can cause severe complications. Leakage risk can be minimised by injecting less cement into the vertebral body, inevitably compromising the mechanical properties of the augmented bone, as a proper endplate-to-endplate connection of the injected cement is needed to obtain a mechanical benefit. Thus the cement flow in a vertebroplasty procedure requires a better understanding. This study aimed at developing a method to monitor the cement flow in a vertebral body and its mechanical effect. Materials and Methods. Eight fresh frozen human cadaveric vertebrae were prepared for augmentation by performing a bitrans- or bipedicular approach. Following they were XTremeCT-scanned (Scanco, Switzerland) at a nominal resolution of 82µm. A custom made setup enabled to fix the vertebrae in the CT bore (Siemens Emotion6) centrically. Bone cement (Vertecem V+, Synthes GmbH, Switzerland) was injected monopedicularly via a syringe driver (Harvard Apparatus, USA). Injection forces were recorded through a load cell (Type 9211, Kistler Instrumente AG, Switzerland) placed on the driver. Either a custom PEEK cannula or a trocar was inserted into each pedicle of a vertebra to allow artifact-free CT scanning. After each milliliter of injection a CT scan of the vertebra was performed at a nominal resolution of 0.63mm. Subsequently, the CT images were resampled to the original XTremeCT image and the cement cloud was segmented. The image data were then further processed for micro finite element (microFE) modeling (FAIM, Numerics88, Canada). The models were then solved for axial stiffness and Von Mises Stress (VMS) distribution. Finally, the vertebrae underwent a biomechanical quasistatic axial compression test (Mini Bionix II 858, MTS Systems Corp., USA). Results. Endplate-to-endplate connection of the cement was reached in 4 vertebrae. The average volume needed to reach the connection was 5.0±1.2 ml. Cement leakage occurred in all vertebrae, whereby in 4 cases the cement leaked into the spine channel. Each successive cement injection step was characterised with an increase of peak injection forces (16.5±12.7N at 1ml to 70.82±21.14N at 6ml). With respect to axial stiffness the mechanical tests and the microFE models correlated well (R. 2. = 0.778). Analyzing the top 100 VMS an elevated stress concentration between the endplate and the cement was observed unless the endplate was in direct contact with the cement. Conclusion. Cement flow can be monitored precisely at each injection step using the time-lapsed CT approach. Combined with microFE modeling the mechanical properties of the augmented bone can be evaluated for different incremental cement volumes injected. Our results suggest augmenting the bone until an endplate-to-endplate connection is established as otherwise partial filling would increase the risk of failure in the trabecular bone structure. This is in close agreement to other studies

Introduction The aim of this study was to assess the effectiveness of percutaneous vertebroplasty as an invervention therapy in symptomatic vertebral compression fractures on pain relief and improvement of the quality of life of the patients. The increasing elderly population is assumed to be associated with an increased incidence of osteoporotic vertebral compression fractures. These fractures lead to a severe morbidity, decreasing quality of life, worsening co-morbidity and sometimes resulting in death. It is justifiable to treat stable vertebral compression fractures by non-operative therapy. Previous studies have shown that vertebroplasty as a non-operative treatment increases the vertebral body strength, restores vertebral body stiffness, reinforces fractured bone, prevents further deformity and alleviates the local pain. Complication rates are reputed to be low. Methods This is a prospective clinical study of percutaneous vertebroplasty in treating stable vertebral compression fractures. Since January 2001, 30 patients were treated by percutaneous vertebroplasty for 58 osteoporotic compression vertebral fractures, four non-osteoporotic stable compression fractures, two compression vertebral fractures due to metastatic carcinoma of the prostate and one due to metastatic carcimona of the cervix. Bone cement PMMA (Howmedica) mixed with Vancomycin antibiotic, and Tantalum Dust Powder (Cook Medical Co) was inserted to the facture site using Oseo-Site Bone Biopsy needle (Cook Medical Co). Pre and post treatment pain, morbidity, quality of life, hospital stay, complication and long term results were evaluated. Results The average hospital stay after vertebroplasty was 2.2 days. Signficant pain relief from 9.9 (pain scale) to 1.8. Improvement of the quality of life: siting, standing, walking without a lumbar brace was achieved one day after the treatment. In some cases the delay of improvement was influenced by the co-morbidity of the patients. No complications were found during the procedure of this treatment. Conclusions Vertebroplasy provided a promisingly good result in alleviating the local pain and improving the quality of life in osteoporotic thoraco-lumbar compression fractures. Prospective and long term results should be evaluated in greater sample size for non osteoporotic stable compression fractures. Although vertebroplasty does not change the nature of carcinoma, it improves the rest of the quality of life of someone suffering from metastatic fractures. In relation to the conduct of this study, one or more of the authors has received, or is likely to receive direct material benefits

Introduction. Vertebroplasty helps to restore mechanical function to a fractured vertebra. We investigated how the distribution of injected cement benefits both fractured and neighbouring vertebrae. Methods. Nine pairs of three-vertebra cadaver spine specimens (aged 67–90 yr) were compressed to induce fracture. One of each pair underwent vertebroplasty with PMMA, the other with a resin (Cortoss). Specimens were then creep-loaded at 1.0kN for 1hr. Before and after vertebroplasty, compressive stiffness was determined, and stress profilometry was performed by pulling a pressure-transducer through each disc whilst under 1.0kN load. Profiles indicated intradiscal pressure (IDP) and compressive load-bearing by the neural arch (F. N. ) at both disc levels. Micro-CT was used to quantify cement fill in the anterior and posterior halves of each augmented vertebral body, and also in the region immediately adjacent to the fractured endplate. Results. Fracture reduced stiffness and IDP, and increased F. N. Following vertebroplasty, anterior fill was greater for Cortoss (30%) than PMMA (17%) (P<0.01). With Cortoss, increased posterior fill was associated with a greater restoration of IDP in the adjacent disc (P<0.05). Furthermore, specimen stiffness increased in proportion to cement fill adjacent to the fractured end-plate. With PMMA, increased anterior fill caused a greater reduction in F. N. in the non-adjacent disc (P<0.05), whereas increased posterior fill and increased fill adjacent to the fracture caused a greater restoration of IDP in the adjacent disc (P<0.05). Conclusion. Cement distribution varied between the two cements. However, increased filling immediately adjacent to the fractured endplate was linked most consistently to improved mechanical function. Conflicts of Interest. None. Source of Funding. This work was funded by Action Medical Research. Vertebroplasty materials were provided by Stryker and by Orthovita. We can confirm that this abstract has not been published previously in whole or substantial part, and the findings have not been presented previously at a national meeting