Instrumentation techniques to prevent proximal junctional kyphosis and proximal junctional failure in adult spinal deformity correction—a systematic review of biomechanical studies

Background contextCorrection of adult spinal deformity (ASD) by long segment instrumented spinal fusion is an increasingly common surgical intervention. However, it is associated with high rates of complications and revision surgery, especially in the elderly patient population. The high construct stiffness of instrumented thoracolumbar spinal fusion has been postulated to lead to a higher incidence of proximal junctional kyphosis (PJK) and failure (PJF). Several cadaveric biomechanical studies have reported on surgical techniques to reduce the incidence of PJF/PJK. As yet, no overview has been made of these biomechanical studies.PurposeTo summarize the evidence of all biomechanical studies that have assessed techniques to reduce PJK/PJF following long segment instrumented spinal fusion in the ASD patient population.Study designA systematic review.MethodsEMBASE and MEDLINE databases were searched for human and animal cadaveric biomechanical studies investigating the effect of various surgical techniques to reduce PJK/PJF following long segment instrumented thoracolumbar spinal fusion in the adult patient population. Studied techniques, biomechanical test methods, range of motion (ROM), intervertebral disc pressure (IDP) and other relevant outcome parameters were documented.ResultsTwelve studies met the inclusion criteria. Four of these studies included non-human cadaveric material. One study investigated the prophylactic application of cement augmentation (vertebroplasty), whereas the remaining studies investigated semi-rigid junctional fixation techniques to achieve a gradual transition zone of forces at the proximal end of a fusion construct, so-called topping-off. An increased gradual transition zone in terms of ROM compared to pedicle screw constructs was demonstrated for sublaminar tethers, sublaminar tape, pretensioned suture loops, transverse hooks and laminar hooks. Furthermore, reduced IDP was found after the application of sublaminar tethers, suture loops, sublaminar tapes and laminar hooks. Finally, two-level prophylactic vertebroplasty resulted in a lower incidence of vertebral compression fractures in a flexion-compression experiment.ConclusionsA variety of techniques, involving either posterior semi-rigid junctional fixation or the reinforcement of vertebral bodies, has been biomechanically assessed. However, the low number of studies and variation in study protocols hampers direct comparison of different techniques. Furthermore, determination of what constitutes an optimal gradual transition zone and its translation to clinical practice, would aid comparison and further development of different semi-rigid junctional fixation techniques. Even though biomechanics are extremely important in the development of PJK/PJF, patient-specific factors should always be taken into account on a case-by-case basis when considering to apply a semi-rigid junctional fixation technique.     

Proximal junctional acute collapse cranial to multi-level lumbar fusion: a cost analysis of prophylactic vertebral augmentation

Background contextLimited data are available regarding incidence of proximal junctional acute collapse after multilevel lumbar spine fusion. There are no data regarding the cost of prophylactic vertebral augmentation adjacent to long lumbar fusions compared with the costs of performing revision fusion surgery for patients suffering with this complication.PurposeTo perform a cost analysis of prophylactic vertebral augmentation for prevention of proximal junctional acute collapse after multilevel lumbar fusion.Study designRetrospective chart review and cost analysis.Patient sampleAll female patients older than 60 years undergoing extended lumbar fusions were reviewed to establish the incidence of proximal junctional acute collapse.Outcome measuresCost estimates for two-level vertebroplasty, two-level kyphoplasty, and revision instrumented fusion were calculated using billing data and cost-to-charge ratios.MethodsCost comparisons of prophylactic vertebral augmentation versus extension of fusion for patients suffering from proximal junctional acute collapse were performed.ResultsTwenty-eight female patients older than 60 years underwent lumbar fusions from L5 or S1 extending to the thoracolumbar junction (T9–L2). Fifteen of the 28 patients had prophylactic vertebroplasty cranial to the fused segment. Proximal junctional acute collapse requiring revision surgery occurred in 2 of the 13 patients (15.3%) treated without prophylactic vertebroplasty. None of the 15 patients undergoing cement augmentation experienced this complication. Assuming a 15% decrease in the incidence of proximal junctional acute collapse, the estimated cost to prevent a single proximal junctional acute collapse was $46,240 using vertebroplasty and $82,172 using kyphoplasty. Inpatient costs associated with a revision instrumented fusion averaged $77,432.ConclusionsProphylactic vertebral augmentation for the prevention of proximal junctional acute collapse may be a cost effective intervention in elderly female patients undergoing extended lumbar fusions. Further efforts are needed to determine more precisely the incidence of proximal junctional acute collapse and the effects of various risk factors on increasing this incidence, as well as methods of prevention.     

Preliminary biomechanical evaluation of prophylactic vertebral reinforcement adjacent to vertebroplasty under cyclic loading

Background ContextPercutaneous vertebroplasty has become a favored treatment option for reducing pain in osteoporotic patients with vertebral compression fractures (VCFs). Short-term results are promising, although longer-term complications may arise from accelerated failure of the adjacent vertebral body.PurposeTo provide a preliminary biomechanical assessment of prophylactic vertebral reinforcement adjacent to vertebroplasty using a three-vertebra cadaveric segment under dynamic loads that represent increasing activity demands. In addition, the effects of reducing the elastic modulus of the cement used in the intact vertebrae were also assessed.Study Design/SettingThree-vertebra cadaveric segments were used to evaluate vertebroplasty with adjacent vertebral reinforcement as an intervention for VCFs.MethodsNine human three-vertebra segments (T12–L2) were prepared and a compression fracture was generated in the superior vertebrae. Vertebroplasty was performed on the fractured T12 vertebra. Subsequently, the adjacent intact L1 vertebra was prophylactically augmented with cement of differing elastic moduli (100–12.5% modulus of the base cement value). After subfailure quasi-static compression tests before and after augmentation, these specimens were subjected to an incrementally increasing dynamic load profile in proportion to patient body weight (BW) to assess the fatigue properties of the construct. Quantitative computed tomography assessments were conducted at several stages in the experimental process to evaluate the vertebral condition and quantify the gross dimensions of the segment.ResultsNo significant difference in construct stiffness was found pre– or postaugmentation (t=1.4, p=.19). Displacement plots recorded during dynamic loading showed little evidence of fracture under normal physiological loads or moderate activity (1–2.5× BW). A third of the specimens continued to endure increasing load demands and were confirmed to have no fracture after testing. In six specimens, however, greater loads induced 11 fractures: 7 in the augmented vertebra (2×T12, 5×L5) and 4 in the adjacent L2 vertebra. A strong correlation was observed between the subsidence in the segmental unit and the incidence of fracture after testing (r_Spearman's=?0.88, p=.002). Altering the modulus of cement in the intact vertebra had no effect on level of segmental compromise.ConclusionsThese preliminary findings suggest that under normal physiological loads associated with moderate physical activity, prophylactic augmentation adjacent to vertebroplasty showed little evidence of inducing fractures, although loads representing more strenuous activities may generate adjacent and peri-augmentation compromise. Reducing the elastic modulus of the cement in the adjacent intact vertebrae appeared to have no significant effect on the incidence or location of the induced fracture or the overall height loss of the vertebral segment.     

Vertebroplasty increases compression of adjacent IVDs and vertebrae in osteoporotic spines

Background contextApproximately 25% of vertebroplasty patients experience subsequent fractures within 1 year of treatment, and vertebrae adjacent to the cemented level are up to three times more likely to fracture than those further away. The increased risk of adjacent fractures postaugmentation raises concerns that treatment of osteoporotic compression fractures with vertebroplasty may negatively impact spine biomechanics.PurposeTo quantify the biomechanical effects of vertebroplasty on adjacent intervertebral discs (IVDs) and vertebral bodies (VBs).Study designA biomechanics study was conducted using cadaveric thoracolumbar spinal columns from elderly women (age range, 51–98 years).MethodsFive level motion segments (T11–L3) were assigned to a vertebroplasty treated or untreated control group (n=10/group) such that bone mineral density (BMD), trabecular architecture, and age were similar between groups. Compression fractures were created in the L1 vertebra of all specimens, and polymethylmethacrylate bone cement was injected into the fractured vertebra of vertebroplasty specimens. All spine segments underwent cyclic axial compression for 115,000 cycles. Microcomputed tomography imaging was performed before and after cyclic loading to quantify compression in adjacent VBs and IVDs.ResultsCyclic loading increased strains 3% on average in the vertebroplasty group when compared with controls after 115,000 cycles. This global strain manifested locally as approximately fourfold more compression in the superior VB (T12) and two- to fourfold higher axial and circumferential deformations in the superior IVD (T12–L1) of vertebroplasty-treated specimens when compared with untreated controls. Low BMD and high cement fill were significant factors that explained the increased strain in the vertebroplasty-treated group.ConclusionsThese data indicate that vertebroplasty alters spine biomechanics resulting in increased compression of adjacent VB and IVD in severely osteoporotic women and may be the basis for clinical reports of adjacent fractures after vertebroplasty.     

The effect of prophylactic vertebroplasty on the incidence of proximal junctional kyphosis and proximal junctional failure following posterior spinal fusion in adult spinal deformity: a 5-year follow-up study

Background Context

The incidence of proximal junctional kyphosis (PJK) ranges from 5% to 46% following adult spinal deformity surgery. Approximately 66% to 76% of PJK occurs within 3 months of surgery. A subset of these patients, reportedly 26% to 47%, develop proximal junctional failure (PJF) within 6 months postoperatively. To date, there are no studies evaluating the impact of prophylactic vertebroplasty on PJK and PJF incidence at long-term follow-up.

Biomechanical comparison of semirigid junctional fixation techniques to prevent proximal junctional failure after thoracolumbar adult spinal deformity correction

BACKGROUND CONTEXTAdult spinal deformity patients treated operatively by long-segment instrumented spinal fusion are prone to develop proximal junctional kyphosis (PJK) and failure (PJF). A gradual transition in range of motion (ROM) at the proximal end of spinal instrumentation may reduce the incidence of PJK and PJF, however, previously evaluated techniques have not directly been compared.PURPOSETo determine the biomechanical characteristics of five different posterior spinal instrumentation techniques to achieve semirigid junctional fixation, or “topping-off,” between the rigid pedicle screw fixation (PSF) and the proximal uninstrumented spine.STUDY DESIGNBiomechanical cadaveric study.METHODSSeven fresh-frozen human cadaveric spine segments (T8–L3) were subjected to ex vivo pure moment loading in flexion-extension, lateral bending and axial rotation up to 5 Nm. The native condition, three-level PSF (T11–L2), PSF with supplemental transverse process hooks at T10 (TPH), and two sublaminar taping techniques (knotted and clamped) as one- (T10) or two-level (T9, T10) semirigid junctional fixation techniques were compared. The ROM and neutral zone (NZ) of the segments were normalized to the native condition. The linearity of the transition zones over three or four segments was determined through linear regression analysis.RESULTSAll techniques achieved a significantly reduced ROM at T10-T11 in flexion-extension and axial rotation relative to the PSF condition. Additionally, both two-level sublaminar taping techniques (CT2, KT2) had a significantly reduced ROM at T9-T10. One-level clamped sublaminar tape (CT1) had a significantly lower ROM and NZ compared with one-level knotted sublaminar tape (KT1) at T10-T11. Linear regression analysis showed the highest linear correlation between ROM and vertebral level for TPH and the lowest linear correlation for CT2.CONCLUSIONSAll studied semirigid junctional fixation techniques significantly reduced the ROM at the junctional levels and thus provide a more gradual transition than pedicle screws. TPH achieves the most linear transition over three vertebrae, whereas KT2 achieves that over four vertebrae. In contrast, CT2 effectively is a one-level semirigid junctional fixation technique with a shift in the upper rigid fixation level. Clamped sublaminar tape reduces the NZ greatly, whereas knotted sublaminar tape and TPH maintain a more physiologic NZ. Clinical validation is ultimately required to translate the biomechanics of various semirigid junctional fixation techniques into the clinical goal of reducing the incidence of proximal junctional kyphosis and failure.CLINICAL SIGNIFICANCEThe direct biomechanical comparison of multiple instrumentation techniques that aim to reduce the incidence of PJK after thoracolumbar spinal fusion surgery provides a basis upon which clinical studies could be designed. Furthermore, the data provided in this study can be used to further analyze the biomechanical effects of the studied techniques using finite element models to better predict their post-operative effectiveness.     

短节段内固定并椎体成形术治疗重度椎体骨质疏松性骨折伴脊柱后凸畸形

目的 评估行后路内固定并椎体成形术治疗椎体骨质疏松性压缩性骨折的疗效.方法 2007年1月～2011年12月,对32例椎体压缩＞2/3并伴脊柱后凸畸形的老年患者行后路脊柱后凸矫正及椎体成形术.对手术前后患椎高度、脊柱后凸Cobb角、腰背部疼痛视觉模拟量表（visual analog scale,VAS）评分和Oswestry功能障碍指数（Oswestry disability index,ODI）进行评价分析.结果 全部病例平均随访13.5个月.手术前,患椎平均剩余高度为27.8 %,脊柱后凸Cobb角25.3°,腰背痛VAS评分8.06,ODI为90%;术后1周,各项指标分别为63.1%,8.5°,3.14,59.7%;手术后3个月,分别为62.7%,8.69°,1.4,31.32%.与术前相比,差异均有统计学意义（P＜0.05）.结论对于重度椎体骨质疏松性骨折合并脊柱后凸畸形的患者,行脊柱后凸矫正及开放椎体成形术,治疗效果良好.     

Effect of vertebroplasty on the compressive strength of vertebral bodies

Background contextPercutaneous vertebroplasty has been used successfully for many years in the treatment of painful compressive vertebral fractures due to osteoporosis.PurposeTo compare the effect of vertebroplasty on the compressive strength of unfractured vertebral bodies.Study designBiomechanical study on cadaveric thoracic vertebrae.MethodsForty vertebral bodies from four cadaveric thoracic spines were used for this experiment. Before testing, each thoracic spine was submitted to bone density testing and radiographic evaluation to rule out any obvious fractures. Under image intensification, 6 mL of a mixture of polymethylmethacrylate (PMMA) with barium (8 g of barium/40 g of PMMA) was injected into every other vertebral body of each spine specimen. After vertebroplasty, all soft tissues were dissected from the spine, and the vertebral bodies were separated and potted for mechanical testing. Testing to failure was performed using a combination of axial compression and anterior flexion moments. Two pneumatic cylinders applied anterior and posterior loads at a distance ratio of 4:3 relative to the anterior vertebral body wall, whereas two additional cylinders applied lateral loads, each at a constant rate of 200 N/s.ResultsThe average failure loads for nonvertebroplasty specimens was 6724.02±3291.70 N, whereas the specimens injected with PMMA failed at an average compressive force of 5770.50±2133.72 N. No statistically significant difference in failure loads could be detected between intact specimens and those that had undergone vertebroplasty.ConclusionsUnder these specific loading conditions, no significant increase in compressive strength of the vertebral bodies could be documented. This suggests that some caution should be applied to the concept of “prophylactic” vertebroplasty in patients at risk for fracture.     

Changes of the adjacent discs and vertebrae in patients with osteoporotic vertebral compression fractures treated with or without bone cement augmentation

BACKGROUND CONTEXTAlthough vertebral augmentation with bone cement has been commonly used to treat symptomatic osteoporotic vertebral compression fractures, relatively little is known about the impact of augmentation on the adjacent spinal components.PURPOSETo determine the imaging effects of vertebral augmentation on the adjacent discs, the augmented vertebra, and the involved spinal segment.STUDY DESIGNRetrospective radiographic study.PATIENT SAMPLEPatients with acute osteoporotic vertebral compression fractures who underwent vertebral augmentation or nonoperative treatments.OUTCOME MEASURESOn baseline and follow-up mid-sagittal T2W magnetic resonance images, quantitative measurements of disc degeneration, including disc height, bulging, and signal, vertebral height, wedge angle, and segmental kyphotic angle were acquired.METHODSLumbar spine magnetic resonance images of patients with acute osteoporotic vertebral compression fractures at a local hospital in Eastern China between 2010 and 2017 were reviewed. Student's t-tests and χ² tests were used to examine the differences of baseline and changes over time between vertebrae underwent vertebral augmentation and those did not. Paired t-tests were used to examine the differences between baseline and follow-up to study the changes of adjacent disc degeneration, creep deformity of the vertebra and progression of segmental kyphosis.RESULTSThere were 112 acute vertebral compression fractures (72 treated with kyphoplasty and 40 with nonoperative treatments) in 101 subjects. At final follow-up (mean 21.5 months), the cranial disc of the augmented vertebra decreased in height (p<.001), and both cranial and caudal discs decreased in signal intensity (p≤.02). The discs in the nonoperative group did not undergo such degenerative changes. For the fractured vertebra, vertebral height significantly decreased (p<.01 for both) and vertebral wedge angle significantly increased (p≤.01 for both), regardless of augmentation treatment or not. Segmental kyphotic angle significantly increased in vertebral fractures that underwent vertebral augmentation (p<.001), but not in those underwent nonoperative treatments.CONCLUSIONSPatients that underwent vertebral augmentation had more advanced disc degeneration at adjacent disc levels as compared to those without augmentation. The fractured vertebral body height decreased and the wedge angle increased, regardless of vertebral augmentation treatment or not. Vertebral augmentation may be associated with increased creep deformity of the adjacent vertebra and the progression of segmental kyphosis.     

Comparison of the adjacent-level fracture rate between instrumented fusion plus vertebroplasty and vertebroplasty alone in osteoporotic spine

Background/PurposePrevious study revealed a high incidence of adjacent-level fracture after vertebroplasty. On the other hand, instrumented fusion plus bone cement augmentation of anterior column have been reported to achieve significant sagittal alignment reduction and strong spinal fixation. Our hypothesis is that instrumented fusion plus vertebroplasty can prevent adjacent-level fractures in high-risk patients.MethodsPatients with predisposing risk factor for adjacent-level fracture were included. All enrolled patients were treated with instrumented fusion plus vertebroplasty (IF) or vertebroplasty alone (VP), and a standardized postoperative care and follow-up protocol was followed. Data from charts and radiographs were collected and analyzed.ResultsA total of 59 patients (40 women and 19 men) with a mean age of 75.4 years were included in this study: 21 patients (15 females) in the IF group and 38 patients (25 females) in the VP group; the mean follow-up period was 34 months. Both groups were similar with respect to age, gender, bone density, involved level, preoperative visual analog scale, and image parameters. It was noted that a greater volume of bone cement was injected in the IF group. Both groups achieved significant improvement in pain scale and image parameters. The overall adjacent-level fracture was 57.89% in VP group. But no adjacent-level fracture was noted in the IF group.ConclusionInstrumented fusion plus vertebroplasty and vertebroplasty alone can provide significant image parameters recovery, and visual analog scale score improvement. However, instrumented fusion plus vertebroplasty is effective in prophylaxis against adjacent-level fracture.     

椎体成形在胸腰椎压缩性骨折后的三维稳定性测试

目的评估在胸腰椎骨折后椎体成形术对恢复脊柱单元即刻三维稳定性的作用。方法7具新鲜胸腰段脊柱标本。测试前屈、后伸、左侧弯、右侧弯、左旋转、右旋转的中性区（neutral zone,NZ）和运动范围（range of motion,ROM）。程序：①完整状态;②骨折后状态;③椎体成形后;④3000次循环疲劳后。结果骨折后中性区和运动范围均明显增大。椎体成形后屈伸、侧弯、旋转在NZ及ROM均明显减少。疲劳后虽然有增加,但较骨折后明显减少。运动范围在椎体成形后和损伤前完整时比较无差别。结论骨水泥椎体成形在离体常规负荷下可恢复脊柱运动单元的三维稳定性。     

经皮椎体成形术190例疗效评价

目的：通过大宗病例的统计分析，探讨X线透视下经皮椎体成形术治疗椎体骨质疏松性压缩骨折、椎体血管瘤、椎体转移癌的临床疗效。方法：2002年8月至2005年8月，采用C形臂X线机透视下俯卧位经皮椎弓根椎体穿刺190例（275个椎体，男80例，女110例；年龄53-91岁，平均66岁），注射PMMA。术前、术后3个月通过视觉模拟疼痛评分（VAS）、活动能力评分和止痛药使用评分的评定，比较改善情况。结果：190例275个椎体均手术成功，VAS术前平均（7．8±1．4）分，术后3个月平均（2．1±0．1）分，分数下降。活动能力评分：术后3个月平均（1．21±0.36）分。较术前平均（2．71±0．71）分明显改善。使用止痛药评分：术后3个月平均（0．89±0．43）分，较术前平均（2．12±0．56）分明显改善（P〈0．05）。结论：经皮椎体成形术为微创性手术，早期止痛效果好，术后下地时间早，避免了患者长期卧床引起的各种并发症，且手术操作简单、治疗费用低，是治疗椎体骨质疏松性压缩骨折、椎体血管瘤、椎体转移癌的有效方法。     

Improving outcomes in adult spinal deformity surgery

Proximal junctional kyphosis and failure are important complications in reconstructive spine surgery. The impact of proximal junctional pathology on health status is variable, and junctional failure may involve compromise of neural and physical function, and may require revision surgery. The risk factors for proximal junctional kyphosis include multilevel fusion to the sacrum, malalignment of the spine, choice of upper instrumented vertebra, magnitude of realignment, bone and muscle quality, tension band integrity and characteristics of the unfused spine. The pathophysiology of proximal junctional pathology involve fracture and bony failure, ligamentous and soft tissue failure, and combined bone and soft tissue failure. Prevention of proximal junctional pathology is an important goal, and has a significant impact on improving the outcomes and durability of spinal reconstructive surgery. Prevention strategies are derived from an understanding of the underlying causes of junctional pathology. Preoperative planning to determine optimal post-operative alignment, and intraoperative strategies to achieve that alignment are important for prevention of junctional pathology. Preoperative preparation of the patient with optimization of bone quality, extensor muscle strength and body mass index may prevent junctional complications. Surgical strategies including anterior column load sharing and posterior augmentation of fixation are useful for prevention of junctional pathology. Cement augmentation at the upper instrumented vertebra, with possible inclusion of the next cephalad vertebra may be protective of bone failure. Ligamentoplasty and preservation of the tension band may be protective of soft tissue failure. Proximal junctional pathology remains an important complication in spinal reconstructive surgery. Understanding the factors associated with proximal junctional pathology including the mechanisms underlying junctional kyphosis, and awareness of the strategies for avoidance of junctional pathology will empower the surgeon to reduce the risk of post-operative junctional kyphosis and lead to improved outcomes in adult spinal deformity surgery.     

Pre-existing vertebral fracture is a risk factor for postoperative proximal junctional fracture after adult spinal deformity surgery: A propensity score-matched analysis

BackgroundCorrective surgery for adult spinal deformity has recently been increasingly performed because of aging populations and advances in minimally invasive surgery. Low bone mineral density is a major contributor to proximal junctional kyphosis after spinal long fusion. Assessment for low bone mineral density ideally involves both dual energy X-ray absorptiometry and identification of pre-existing vertebral fractures, the latter, requiring only standard equipment, being performed more frequently. We therefore aimed to examine the impact of pre-existing vertebral fractures on the incidence of type 2 proximal junctional kyphosis, including proximal junctional fracture and failure, after corrective surgery for adult spinal deformity.MethodsWe performed a retrospective, single institution study of 106 women aged over 50 years who had undergone corrective long spinal fusion for severely symptomatic spinal deformity from 2014 to 2017. We allocated them to three groups (with and without pre-existing vertebral fractures and with severe [Grades 2–3 according to Genant et al.‘s classification] preexisting vertebral fractures) and used propensity score matching to minimize bias. The primary outcome was postoperative proximal junctional fracture and the secondary outcome proximal junctional kyphosis/failure.ResultsThe primary and secondary endpoints were achieved significantly more often in the 28 patients with than in the 78 without preexisting vertebral fractures (total 41). The former group was also significantly older and had greater pelvic tilt and fewer fused segments than those without vertebral fractures. After propensity score matching, the incidences of the endpoints did not differ with pre-existing vertebral fracture status; however, patients with severe vertebral fractures more frequently had proximal junctional fractures postoperatively. Postoperative improvements in health-related quality of life scores did not differ with pre-existing vertebral fracture status.ConclusionsSevere pre-existing vertebral fractures are a risk factor for proximal junctional fracture after correction of adult spinal deformity.     

Vertebroplasty and Kyphoplasty in Spinal Trauma

Abstract Kyphoplasty and vertebroplasty have become recognized procedures for the treatment of vertebral fractures, especially in patients with osteoporosis. In most cases of osteoporotic spinal vertebral fracture in elderly patients, polymethylmethacrylate (PMMA) cement is used to fill the defect and stabilize the vertebral body. The techniques of vertebroplasty and kyphoplasty differ in the possibility of realignment and reconstruction of the vertebral body and spinal column. Long-term results in terms of integration of the cement and bioreactivity of the vertebral body are still lacking; so, these procedures are still no options in the treatment of younger patients. Vertebroplasty and kyphoplasty show different success in the management of fresh traumatic spine fractures. The acute traumatic vertebral fracture has to be classified sensitively, to find the right indication for cement augmentation. Mild acute compression fractures can be treated by vertebroplasty or kyphoplasty, severe compression and burst fractures by combination of internal fixation and kyphoplasty. The indications for use of biological or osteoinductive cement in spinal fracture management must still be regarded as restricted owing to the lack of basic biomechanical research data. Such cement should not be used except in clinical studies.     

骨填充网袋椎体成形术与经皮球囊后凸成形术治疗骨质疏松性椎体压缩性骨折

目的:探讨骨填充网袋椎体成形术治疗骨质疏松性椎体骨折的临床疗效。方法:对2015年12月至2017年6月符合纳入与排除标准的127例(145椎)骨质疏松性胸腰椎体骨折患者的临床资料进行回顾性分析,通过临床表现、X线、CT、MRI明确责任椎体,其中95例(110椎)采用经皮椎体后凸成形术治疗(PKP组),男34例(42椎),女61例(68椎),年龄(73.92±7.14)岁,胸椎47节(T_8-T_(12)),腰椎63节(L_1-L_5);另外的32例(35椎)采用骨填充网袋椎体成形术治疗(网袋组),男11例(12椎),女21例(23椎),年龄(71.56±7.89)岁,胸椎16节(T_9-T_(12)),腰椎19节(L_1-L_5)。观察患者术后3 d疼痛改善、椎体高度恢复、功能改善情况,并通过X线片观察骨水泥弥散及渗漏情况。结果:所有患者顺利完成手术,术中未出现并发症。骨填充网袋椎体成形术治疗的32例患者手术时间为(31.75±4.99)min,术后3 d的VAS评分,椎体前缘、中部高度,腰部ODI评分分别为(2.38±0.94)分、(19.54±2.36)mm、(18.16±2.65)mm和(25.19±5.49)分,各项目与术前比较明显改善(P0.01),与PKP组比较差异无统计学意义(P0.05)。术后3 d的X线片显示两组患者的骨水泥均呈斑片状、团块状或少量弥散状分布,网袋组的渗漏率为2.86%(1/35),PKP组的渗漏率为16.36%(18/110),多为"拖尾征",两组比较差异有统计学意义(P0.05)。结论:骨填充网袋椎体成形术治疗骨质疏松性椎体骨折具有类似经皮椎体后凸成形术的疗效,能够缓解疼痛,恢复部分椎体高度,并且明显减少渗漏率,是一种简单、快速、有效的治疗方法。     

经皮椎体成形术治疗骨质疏松型胸腰椎压缩性骨折的临床评价

目的：评价经皮椎体成形术(percutaneous vertebroplasty,PVP)治疗骨质疏松型胸腰椎压缩性骨折的效果及安全性,探讨避免手术并发症的措施。方法回顾性分析2010年3月至2014年1月我院采用经椎弓根入路双侧PVP治疗骨质疏松型胸腰椎压缩性骨折的患者45例,按病变部位分为胸椎组,腰椎组和合并胸腰椎骨折组,分别于术后3 d、术后1年随访患者,以视觉模拟评分法( visual analogue score,VAS)和Oswestry功能障碍指数( Oswestry disability index,ODI)为评价指标,应用SAS软件进行t检验分析,比较治疗前后VAS和ODI评分的差异。结果45例骨质疏松型压缩性骨折患者行PVP治疗后3 d、1年VAS评分分别降低了(5.87±1.00)分、(4.25±1.28)分,ODI评分分别下降了(54.97±4.92)分、(41.47±5.88)分,术后3 d、1年胸椎组、腰椎组VAS评分和ODI评分,差异均无统计学意义(均P>0.05)。 PVP治疗过程中5例患者发生骨水泥渗漏,但无神经损坏、肺栓塞等并发症。结论PVP是治疗骨质疏松型胸腰椎压缩性骨折的一种安全、有效的治疗方式。 PVP对骨质疏松引起的胸椎、腰椎骨折疗效相当。 PVP新型材料的安全性还需进一步研究探讨。严格掌握适应证、规范的操作、把握好推注骨水泥量和速度是目前预防并发症的有效方法。     

Occlusion of the lumbar spine canal during high-rate axial compression

BACKGROUND CONTEXTWhile burst fracture is a well-known cause of spinal canal occlusion with dynamic, axial spinal compression, it is unclear how such loading mechanisms might cause occlusion without fracture.PURPOSETo determine how spinal canal occlusion during dynamic compression of the lumbar spine is differentially caused by fracture or mechanisms without fracture and to examine the influence of spinal level on occlusion.STUDY DESIGNA cadaveric biomechanical study.METHODSTwenty sets of three-vertebrae specimens from all spinal levels between T12 and S1 were subjected to dynamic compression using a hydraulic loading apparatus up to a peak velocity between 0.1 and 0.9 m/s. The presence of canal occlusion was measured optically with a high-speed camera. This was repeated with incremental increases of 4% compressive strain until a vertebral fracture was detected using acoustic emission measurements and computed tomographic imaging.RESULTSFor axial compression without fracture, the peak occlusion (O_max) was 29.9±10.0%, which was deduced to be the result of posterior bulging of the intervertebral disc into the spinal canal. O_max correlated significantly with lumbar spinal level (p<.001), the compressive displacement (p<.001) and the cross-sectional area of the vertebra (p=.031).CONCLUSIONSSpinal canal occlusion observed without vertebral fracture involves intervertebral disc bulging. The lower lumbar spine tended to be more severely occluded than more proximal levels.CLINICAL SIGNIFICANCEClinically, intermittent canal occlusion from disc bulging during dynamic compression may not show any radiographic features. The lower lumbar spine should be a focus of injury prevention intervention in cases of high-rate axial compression.     

The biomechanical effectiveness of prophylactic vertebroplasty: a dynamic cadaveric study

OBJECT: The purpose of the study was to investigate the segmental effects of prophylactic vertebroplasty under increasingly demanding loading conditions and to assess the effect of altered cement properties on the construct biomechanics. METHODS: Twelve human cadaveric 3-vertebral functional spinal units (T12-L2) were prepared such that the intact L-1 vertebra was prophylactically augmented with cements of differing elastic moduli (100, 50, 25, and 12.5% modulus of the base cement). These specimens were subjected to quasistatic subfailure compression pre- and postaugmentation to 50% of the predicted failure strength and then cyclic loading in a fatigue rig (115,000 cycles) to characterize the high-stress, short-cycle fatigue properties of the construct. Loading was increased incrementally in proportion to body weight to a maximum of 3.5 x body weight. Quantitative computed tomography assessment was conducted pre- and postaugmentation and following cyclic testing to assess vertebral condition, cement placement, and fracture classification. RESULTS: Adjacent and periaugmentation fractures were induced in the prophylactically augmented segments. However, it appeared that these fractures mainly occurred when the specimens were subjected to loads beyond those that may commonly occur during most normal physiological activities. CONCLUSIONS: Lowering the elastic modulus of the cement appeared to have no significant effect on the frequency or severity of the induced fracture within the vertebral segment.