Fluoroscopically guided anterior atlantoaxial transarticular screws: a feasibility and trajectory study using CT-based simulation software

Background contextAnterior transarticular screw (ATAS) fixation has been suggested as a viable alternative to posterior stabilization. However, we are not aware of previous reports attempting to establish the usefulness of specific fluoroscopic landmark-guided trajectories in the use of ATAS, and we could find no reference to it in a computerized search using MEDLINE.PurposeTo determine the anatomic feasibility of ATAS placement using defined fluoroscopic landmarks to guide screw trajectory.Study designEvaluation using three-dimensional screw insertion simulation software and 1.0-mm–interval computed tomographic scans.Patient sampleComputed tomographic scans of 100 patients including 50 men and 50 women.Outcome measuresIncidence of violation of the vertebral artery groove of C1 and C2, the spinal canal, and the atlanto-occipital joint and screw lengths and lengths of C1 and C2 purchase.MethodsFour screw trajectories were determined: promontory screw (PS), single central facet (CF) screw, and medial (MF) and lateral (LF) double facet screws. Placement of a 4.0-mm screw was simulated using defined fluoroscopic landmarks for each trajectory. The previously mentioned outcome measures were evaluated and compared for the four trajectories. This study was not supported by any financial sources, and there is no topic-specific potential conflict of interest with this study.ResultsNo violation of the C1 or C2 vertebral artery groove or of the spinal canal was observed for any of the screw types. Screw lengths and the length of C2 purchase were by far the longest for PS (40.4±2.8 and 25.7±2.1 mm, respectively; p<.001 in all post hoc comparisons). The length of C1 purchase was longer for CF (16.4±2.3 mm) and LF (15.8±1.6 mm) than PS (14.7±2.0 mm) and MF (14.6±2.4 mm) (p≤.001, respectively). There was no atlanto-occipital joint violation if the length of C1 purchase was set at 12 mm for CF and LF and at 10 mm for PS and MF.ConclusionsOur results suggest that it may be possible to place ATASs without violating the vertebral artery groove, spinal canal, or the atlanto-occipital joint by using the described entry points, trajectories, and fluoroscopic landmarks.     

Use of vertebroplasty to prevent proximal junctional fractures in adult deformity surgery: a biomechanical cadaveric study

Background contextVertebral compression fractures at the proximal junction are common complications of long spinal fusion surgeries that can contribute to the development of proximal junctional kyphosis or proximal junctional failure. To our knowledge, no biomechanical studies have addressed the effect of vertebral augmentation at the proximal junction.PurposeTo evaluate the effectiveness of prophylactic vertebroplasty in reducing the incidence of vertebral compression fractures at the proximal junction after a long spinal fusion in a cadaveric spine model.Study designBiomechanical cadaveric study.MethodsWe divided 18 cadaveric spine specimens into three groups of six spines each: a control group, a group treated with one-level prophylactic vertebroplasty at the upper instrumented vertebra, and a group treated with two-level prophylactic vertebroplasty at the upper instrumented vertebra and the supra-adjacent vertebra. In all spines, the pedicles were instrumented from L5 to T10. Using eccentric axial loading, the specimens were then compressed until failure. Failure was defined as a precipitous decrease in load with increasing compression. The effect of augmentation on load-to-failure was checked using linear regression. The effect of augmentation on incidence of adjacent fractures was checked using logistic regression. Differences at the level of p<.05 were considered significant. KyphX cement introducer was donated by Kyphon, and the pedicle screws were donated by DePuy.ResultsFractures occurred in 12 of 18 specimens: five in the control group, six in the one-level group, and only one in the two-level group; these differences were statistically significant.ConclusionsProphylactic vertebroplasty at the upper instrumented level and its supra-adjacent vertebra reduced the incidence of junctional fractures after long posterior spinal instrumentation in this axially loaded cadaveric model. Additional studies are necessary to determine if these results are translatable to clinical practice.     

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.     

American Paraplegia Society 48th Annual Conference • September 2002 Poster Presentations #P1-P30 Sci Research • Pharmacology • Technology • Education

Abstract

Background/Objective: Salmonella spondylodiskitis is an uncommon type of vertebral infection. The aim of this study was to present a case of progressive paraplegia caused by Salmonella spondylodiskitis and epidural abscess after endoscopic cholecystectomy.

Methods: The patient underwent posterior instrumentation and posterior fusion between T6 and T12, hemilaminotomies at levels T8-T9-T10, and drainage of the abscess. Through a left thoracotomy, anterior T8-T10 corpectomy, debridement, anterior stabilization, and fusion were conducted.

Results: Fifteen months later, final follow-up showed no complications secondary to the vertebral and hip surgeries, and neurological status improved to Frankel grade E. Laboratory investigations showed no evidence of Salmonella infection.

Conclusion: Immunocompromised patients who undergo endoscopic intervention are vulnerable to Salmonella infections. One must consider Salmonella infection in those who develop acute progressive spondylodiskitis.     

Clinical anatomy of vertebrae in scoliosis: global analysis in four different diseases by multiplanar reconstructive computed tomography

Background contextFew accurate analyses of clinically useful vertebral anatomy have been conducted, and most have focused on thoracic idiopathic scoliosis.PurposeTo evaluate the different anatomic characteristics in scoliosis by disease type and level.Study designObservational cohort study.Patient sampleForty-eight patients with scoliosis were included in this study.Outcome measuresSubjects underwent computed tomography (CT) of the whole spine.MethodsForty-eight patients with scoliosis were included in this study: 15 adolescent idiopathic, 11 cerebral palsy (CP), 10 muscular dystrophy (MD), and 12 congenital (CG) scoliosis patients with similar demographics. Subjects underwent CT of the whole spine, preoperatively. Eight anatomic parameters were measured in multiplanar reconstructive CT images, and statistical analysis was performed to investigate differences.ResultsIn general, values in the anatomic parameters were similar for the four diseases. Each parameter showed the unique change pattern according to the spinal level regardless of curvature shape, direction, or magnitude. In particular, chord length (CL) in MD and CG scoliosis was lower than in adolescent idiopathic scoliosis (AIS) and CP, and pedicle rib unit length was lower in CG scoliosis than in the other diseases (p<.05). Comparisons of convex and concave anatomies in AIS showed that inner pedicle width (PWI) and outer pedicle width (PWO) were wider for convex side, CL, pedicle width, and transverse pedicle angle were greater for concave side (p<.05), and differences were more significant at apices. However, in CP, PWI and PWO were similar between convex and concaves sides (p>.05). Although PWI and PWO were wider for convex sides and CL and pedicle length were greater for concave sides in MD (p<.05), differences were less significant at apices. Particularly, CG scoliosis showed severely deformed anatomy, with differences of seven parameters at apical vertebrae (p<.05).ConclusionClinical anatomies of vertebrae in scoliosis were found to differ significantly at different levels and in terms of convexity and disease type.     

Usefulness of Prone Cross-Table Lateral Radiographs in Vertebral Compression Fractures

Background

Dynamic radiographs are recommended to investigate non-healing evidence such as the dynamic mobility or intravertebral clefts in osteoporotic vertebral compression fractures (VCFs). However, it is difficult to examine standing flexion and extension lateral radiographs due to severe pain. The use of prone cross-table lateral radiographs (PrLRs) as a diagnostic tool has never been proposed to our knowledge. The purpose of this study is to clarify the usefulness of PrLRs in diagnosis and treatment of VCFs.

Methods

We reviewed 62 VCF patients examined with PrLRs between January 1, 2008 and June 30, 2011. To compare the degree of pain provoked between standing extension lateral radiographs (StLRs) and PrLRs, numeric rating scale (NRS) scores were assessed and compared by a paired t-test. Vertebroplasty was done for 40 patients and kyphoplasty was done for 9 patients with routine manners. To assess the degree of postural reduction, vertebral wedge angles (VWA) and vertebral height ratios (VHR) were calculated by using preoperative StLRs, PrLRs, and postoperative lateral radiographs. Two variables derived from changes in VWA and VHR between preoperative and postoperative radiographs were compared by a paired t-test.

Results

The average NRS scores were 6.23 ± 1.67 in StLRs and 5.18 ± 1.47 in PrLRs. The degree of pain provocation was lower in using PrLRs than StLRs (p < 0.001). The average changes of VWA between preoperative and postoperative status were 5.24° ± 6.16° with PrLRs and 3.46° ± 3.47° with StLRs. The average changes of VHR were 0.248 ± 0.178 with PrLRs and 0.148 ± 0.161 with StLRs. The comparisons by two variables showed significant differences for both parameters (p = 0.021 and p < 0.001, respectively). The postoperative radiological status was reflected more precisely when using PrLRs than StLRs.

Conclusions

In comparison with StLR, the PrLR was more accurate in predicting the degree of restoration of postoperative vertebral heights and wedge angles, and provoked less pain during examination. The PrLR could be a useful diagnostic tool to detect intravertebral cleft or intravertebral dynamic instability.     

经皮椎体成形术在椎体压缩骨折及椎体肿瘤治疗中的临床应用

目的 总结分析经皮椎体成形术(PVP)在骨质疏松性椎体压缩骨折及椎体肿瘤治疗中临床应用的疗效.方法 宣武医院神经外科2007年1月至2012年6月应用PVP治疗45例患者共62个病变椎体,随访时间点为术后24h、3、6、12、24及36个月,采用VAS、ODI评价其临床疗效,椎体前缘高度及Cobb角评估影像学结果.结果 平均随访时间(13.9±7.8)个月,术后24 h,患者VAS疼痛评分、ODI指数及Cobb角分别由术前(7.3±1.9)分、32.0±3.4和15.0°±2.3°降至术后(4.8±1.6)分、22.1±2.1和14.0°±1.9°(P＜0.05),椎体前缘高度由术前(16.0±1.8) mm升至(19.0±2.1)mm(P＜0.05).3～36个月随访期内,VAS评分、椎体前缘高度及Cobb角差异无统计学意义(P＞0.05).随访中约54％患者VAS评分维持在5分以内.结论 PVP是治疗骨折及肿瘤所致的椎体源性疼痛简单有效的微创疗法,临床疗效稳定.     

Vertebral Artery Anomaly Causing C2 Suboccipital Neuralgia,Relieved by Neurovascular Decompression

We report imaging and surgical findings of a symptomatic 40‐year‐old male with an anomalous left vertebral artery. MR, CT myelography, angiography, and intraoperative photos demonstrate the vertebral artery entering the thecal sac at the C1‐C2 intervertebral foramen and compressing the dorsal C2 nerve rootlets against the cord. Open microvascular decompression alleviated the patient's long‐standing suboccipital and posterior cervical neck pain. An embryologic review of the vertebral and lateral spinal artery systems reveals possible developmental explanations for this variant. Intradural course of the vertebral artery at C2 is one of the few symptomatic developmental vertebral artery anomalies. Recognition of this condition is important because surgical intervention can alleviate associated neck pain.     

寰枢段椎动脉在远外侧入路中的应用显微解剖研究

目的 为颅颈交界区手术入路提供解剖学参数,帮助神经外科医生安全、准确地暴露手术靶区.方法 应用10％甲醛固定的汉族成人尸头标本10例20侧;漂白干颅骨及寰枢椎10例20侧.模拟手术入路逐层解剖,并对解剖结构进行精确测量和拍照.结果 寰枢段椎动脉在颅颈交界区形成比较恒定的五个生理弯曲,平均直径(4.3±0.5) mm,角度多变.寰椎后弓外侧半距(19.3±4.7)mm.结论 熟悉寰枢段椎动脉五个生理弯曲的定位方法,有助于提高颅颈交界区手术入路的安全性.