Computer simulation for the optimization of instrumentation strategies in adolescent idiopathic scoliosis

Recent studies reveal a large variability of instrumentation strategies in adolescent idiopathic scoliosis (AIS). Determination of the optimal configuration remains controversial. This study aims to develop a method to define the optimal surgical instrumentation strategy using a computer model implemented in a spine surgery simulator (S3). A total of 702 different strategies were simulated on a scoliotic patient using S3. Each configuration was assessed using objective functions that represented different correction objectives. Twelve geometric parameters were used in the three anatomic planes and mobility, and their relative weights were defined by a spine surgeon according to his objectives for correction of scoliosis. Six instrumentation parameters were manipulated in a uniform experimental design framework. An interpolation technique was used to build an approximation model from the simulation results and to locate instrumentation parameters minimizing the objective function. Small or no differences in the correction between the simulated optimal strategy and the real postoperative results of the instrumented segments were observed in the three planes. But the same overall correction was obtained by using fewer implants (only screws) and less instrumented levels. This study demonstrates the potential and feasibility of using a spine surgery simulator to optimize the planning of surgical instrumentation in AIS.     

后路椎弓根螺钉系统治疗特发性腰椎侧凸的有限元分析

目的通过有限元计算与刚体动力学相结合的方法,模拟后路椎弓根螺钉系统治疗脊柱侧凸的矫形过程,研究矫形过程中的生物力学特性,探讨不同矫形策略对临床结果的影响,为脊柱侧凸的手术规划提供依据。方法通过病体腰椎CT切片进行三维几何重构,利用ANSYS有限元软件建立了右凸40o腰椎L1-L5和椎弓根螺钉器械的三维有限元模型,联合ADAMS刚体动力学软件模拟了矫形手术中的反旋转与回弹,得到了矫形全过程中植入物所受载荷以及脊椎的应力应变场。结果不同矫形手术过程中,植入器械承受的最大反力范围约为1961099N,椎骨的极少数单元应力超过强度极限120MPa。结论后路椎弓根螺钉系统矫正腰椎侧凸具有较好的治疗效果,脊椎骨性结构的应力水平整体较低。在满足矫形效果的前提下,临床上可考虑选择不同的矫形策略,以减少需植入螺钉的腰椎节段数量并提高手术质量。     

Computer simulation for the optimization of patient positioning in spinal deformity instrumentation surgery

Studies have shown that scoliosis curves correct when patients are positioned on the operating table prior to instrumentation. However, biomechanical aspects of positioning have not been widely studied. The objective of this study was to simulate patient positioning during instrumentation surgery and test various adjustment parameters of the trunk and recommend optimal patient positioning prior to, and during spine surgery based on the results of finite element simulations. A scoliotic patient was simulated using a finite element model and six different positioning parameters were modified while ten geometric measures were recorded. Statistical analysis determined which model parameter had a significant effect on the geometric measures. Geometric measures were individually and simultaneously optimized, while corresponding model parameters were documented. Every model parameter had a significant effect on at least five of the geometric measures. When optimizing a single measure, others would often deteriorate. Simultaneous optimization resulted in improved overall correction of the patient’s geometry by 75% however ideal correction was not possible for every measure. Finite element simulations of various positioning parameters enabled the optimization of ten geometric measures. Positioning is an important surgical step that should be exploited to achieve maximum correction.     

Patient-specific mechanical properties of a flexible multi-body model of the scoliotic spine

The flexibility of the scoliotic spine is an important biomechanical parameter to take into account in the planning of surgical instrumentation. The objective of the paper was to develop a method to characterisein vivo the mechanical properties of the scoliotic spine using a flexible multi-body model. Vertebrae were represented as rigid bodies, and intervertebral elements were defined at every level using a spherical joint and three torsion springs. The initial mechanical properties of motion segments were defined fromin vitro experimental data reported in the literature. They were adjusted using an optimisation algorithm to reduce the discrepancy between the simulated and the measured Ferguson angles in lateral bending of three spine segments (major or compensatory left thoracic, right thoracic and left lumbar scoliosis curves). The flexural rigidity of the spine segments was defined in three categories (flexible, nominal, rigid) according to the estimated mechanical factors (α). This approach was applied with ten scoliotic patients under-going spinal correction. Personalisation of the model resulted in an increase of the initial flexural rigidity for seven of the ten lumbar segments (1.38≤α≤10.0) and four of the ten right thoracic segments (1.74≤α≤5.18). The adjustment of the mechanical parameters based on the lateral bending tests improved the model's ability to predict the spine shape change described by the Ferguson angles by up to 50%. The largest differences after personalisation were for the left lumbar segments in left bending (4⁰±3⁰). Thein vivo identification of the mechanical properties of the scoliotic spine will improve the ability of biomechanical models adequately to predict the surgical correction, which should help clinicians in the planning of surgical instrumentation manoeuvres.     

Biomechanical modelling of segmental instrumentation for surgical correction of 3D spinal deformities using Euler-Bernoulli thin-beam elastic deformation equations

A simplified computer-modelling technique intended to analyse 3D spinal deformity correction with segmental instrumentation is presented. The spine was modelled as a thin beam-composed structure linked by implants to two deformable rods. The Landau vector representation of Euler-Bernoulli beam elastic deformation equations was used to formulate the simulation approach. All types of essential deformation (bending, torsion, tension, compression) were considered. An iterative numerical method was proposed to obtain an appropriate load, able to deform the spine axial curve to the desired post-operative shape. A simulation based on the spine of a real scoliotic patient (thoracic and lumbar Cobb angles: 39° and 8°), corrected using surgical instrumentation intervention, is presented. Force loads within the range of 20–350N were able to deform the pre-operational spine axial curve to the post-operational one with a root mean square approximation error of 3.7 mm. Similarly good corrections were obtained using different force patterns. This highlights the uncertainty of which corresponding surgical instrumentation to use. Such uncertainty is related to the ‘ill-posed problems’ property of mechanical systems.     

腰椎手术后的邻近节段翻修

目的:评估腰椎手术邻近节段翻修手术方法和疗效,探讨邻近节段病(ASD)的预防和治疗策略.方法:回顾性分析我院2003年12月～2009年3月间收治的腰椎手术后邻近节段翻修患者23例(ASD组),其中19例行减压、椎弓根螺钉内固定及植骨融合治疗,4例行减压结合棘突间非融合装置治疗;随机抽取同期我院收治的行单节段椎管减压内固定和植骨融合治疗患者共26例作为对照组.应用VAS、JOA下腰痛评分评价并比较两组患者术前、术后腰腿痛程度与功能状况.结果:ASD组与对照组随访时间分别为4.6 a和5.1 a.ASD组VAS评分术前7.6±1.2、术后2.5±1.6,JOA评分术前11.2±4.2、术后24.2±3.1;对照组VAS评分术前6.8±2.1、术后2.3±0.9,JOA评分术前11.2±4.2、术后26.5±2.5.改善率(RI)ASD组73%,对照组85.7%.两组间末次随访的JOA评分和改善率差异均无统计学意义(P＞0.05),但在行走、感觉异常和下肢症状等JOA单项评估上,两组间差异有统计学意义(P＜0.05).结论:在腰椎初次手术时,应注意筛检并减少ASD的危险因素,降低ASD的发生.采用椎板扩大开窗减压、内固定和植骨融合术,对腰椎手术的邻近节段进行翻修,可取得较好的疗效.     

下颈椎爆裂骨折合并脊髓损伤的手术治疗

目的评估手术治疗下颈椎爆裂骨折合并脊髓损伤的临床效果。方法回顾性分析自2002年以来收治的12例下颈椎爆裂骨折合并脊髓损伤的临床资料。伤后2~8 d,4例采用前路减压植骨融合内固定术,8例采用1期前-后联合减压植骨融合内固定术。采用ASIA分级评估神经功能,用放射学方法评估植骨融合情况,记录围手术期并发症。结果平均随访11.2个月。1例伤后2 d接受手术,术后死亡,6例术后发生并发症,经对症处理治愈。3例术后需要机械通气支持。7例患者有不同程度神经功能恢复（ASIA分级提高1~2级）。随访期间未见内固定失败者。结论手术治疗下颈椎爆裂骨折可以达到神经组织减压和重建颈椎稳定性的目的 ,根据具体病情可以选择单纯前路手术或者1期前后路联合手术。     

Sagittal plane analysis of adolescent idiopathic scoliosis after VATS (video-assisted thoracoscopic surgery) anterior instrumentations

Radiographic sagittal plane analysis of VATS (video-assisted thoracoscopic surgery) anterior instrumentation for adolescent idiopathic scoliosis. This is retrospective study. To report, in details about effects of VATS anterior instrumentation on the sagittal plane. Evaluations of the surgical outcome of scoliosis have primarily studied in coronal plane correction, functional, and cosmetic aspects. Sagittal balance, as well as coronal balance, is important in functional spine. Recently, scoliosis surgery applying VATS has been increasingly performed. Its outcome has been reported several times; however, according to our search of the literature, the only one study partially mentioned. The study population was a total of 42 cases of idiopathic scoliosis patients (8 male, 34 female). Their mean age was 15.6 years (13 to 18 years). The 18 cases were Lenke IA type, 16 cases were Lenke IB type, and 8 cases were Lenke IC type. The preoperative Cobb's angle was 54.5 +/- 13.9 degrees. All patients were followed up for a minimum of 2 years and implanted, on average, at the 5.9 level (5 to 8 levels). The most proximal implant was the 4th thoracic spine, and the most distal implant was the 1st lumbar spine. Whole spine standing PA and lateral radiographs were taken before surgery, 2 months after surgery, and at the last follow up (range 24-48 months, mean 35 months). The C7 plumbline proximal junctional measurement (PJM), distal junctional measurement (DJM), thoracic kyphosis, and lumbar lordosis angles were measured and compared. In all cases, follow-ups were possible and survived till the last follow up. The Cobb's angle in coronal plane at the last follow up was 19.7 +/- 9.3 degrees and was corrected to 63.8% on average. The preoperative C7 sagittal plumbline before surgery was -13.9 +/- 29.1 mm, the final follow up was -9.9 +/- 23.8 mm, and the average positive displacement was 4 mm. Thoracic kyphosis was increased from preoperative 18.2 +/- 7.7 degrees to 22.4 +/- 7.2 degrees on average at the last follow up, and the increase was, on average, 4.2 degrees. The PJM angel was increased from 6.2+/- 4.3 degrees preoperative to 8.8 +/- 3.7 degrees at the last follow up, and the increment was, on the average, 2.6 degrees. The DJM angle before surgery was 6.8 +/- 5.1 degrees and 6.7 +/- 4 degrees at the last follow up, and did not change noticeably. Preoperative lumbar lordosis was 42 +/- 10.7 degrees and 43.5 +/- 11.1 degrees after surgery. Similarly, it did not change greatly. The scoliosis surgery applying VATS displaced the C7 sagittal plumb line by 4 mm to the anteriorly, increased thoracic kyphosis by 4.2 degrees, and increased PJM by 2.6 degrees. DJM and lumbar lordosis, before and after operation, were not significantly different. Although the surgical technique of VATS thoracic instrumentation is difficult to make the normal thoracic kyphosis, an acceptable sagittal balance can be obtained in Lenke type I adolescent idiopathic scoliosis using VATS.     

Ultra high molecular weight polyethylene (UHMWPE) model can provide results comparable to cadaveric models

The in vitro biomechanical models using a cadaveric spine specimen have long been used in understanding normal and abnormal functions of spines as well as for strength and stability testing of the spine specimen or spinal construct. Little effort has been made to describe the similarities or differences between UHMWPE and cadaveric models. Eight cadaveric lumbar spines were harvested generating six FSU and three corpectomy models. Six UHMWPE blocks were fabricated to form FSU and corpectomy models. All were tested intact, with posterior instrumentation, and with anterior instrumentation consisting of Moss-Miami 4.0 mm stainless steel rods, uni-axial stainless steel screws and DePuy Harm's cages. All models were tested in axial compression. The cadaveric model and UHMPWE model yielded axial stiffness values of comparable magnitude with respect to instrumentation applied using the posterior approach (P>0.05). Under an FSU configuration, only in the case of anterior instrumentation without the addition of a Harm's cage did both the cadaveric and UHMPWE models provide comparable axial stiffness results (P>0.05). While in vitro cadaveric models are considered the gold standard for biomechanical testing of the spine, the data suggests that under specific approaches and surgical models UHMWPE can be used to infer mechanical performance of instrumentation in cadaveric material.     

半自动脊柱手术机器人系统在脊柱外科治疗中的应用

文题释义：医学机器人：是多学科研究和发展的成果,是指被应用在诊断、治疗、康复、护理和功能辅助等诸多医学领域的机器人,目前主要被分为手术机器人、康复机器人、辅助机器人、服务机器人。   自动化程度：可分为医师完全直接控制、医师机器人协同控制、医师监督下半自动及机器人全自动4个等级。医师监督下半自动即在医师监督下,手术机器人有一定的自主性执行手术任务,医师主要起到巡视监督的作用,在执行的过程中参与较少,例如肿瘤放射治疗的赛博刀系统。术中或术前医师负责手术规划,执行工作交付于手术机器人,医师在术中可调整手术计划,确保手术过程的安全执行。 背景：临床常用的手术机器人主要依赖进口,自动化程度不高,核心技术无法突破,国产机器人方兴未艾,手术机器人造价昂贵,手术费用居高不下。课题组及深圳鑫君特智能医疗器械有限公司协同开发了Orthobot脊柱外科专用手术机器人系统,对国产手术机器人的发展意义重大。 目的：通过动物腰椎模型探讨Orthobot半自动脊柱手术机器人系统在腰椎手术的应用可行性,验证其安全性及有效性,优化手术流程。 方法：将12具实验猪腰椎标本(L₁-L₆)随机分成2组,实验组(6具)采用术前CT扫描数据结合术中C臂机X射线透视进行配准,在三维CT数据下规划钉道,应用Orthobot机器人系统进行腰椎标本椎弓根定位,克氏针钻孔,沿克氏针攻丝,制备钉道;对照组(6具)直接采用术中C臂机X射线透视数据,在二维X射线数据下规划钉道。记录术中钉道规划时间、克氏针植入时间、射线暴露时间及机器人单个钉道制备总耗时。复查CT扫描,参照Abul-Kasimhierarchy分级系统评估植入椎弓根螺钉钉道的准确性与优良率。 结果与结论：①实验组钉道规划时间、单个钉道制备总耗时长于对照组(P < 0.001),两组射线暴露时间、克氏针植入时间比较无显著性意义(P > 0.05);②复查CT评估显示,实验组制备60个腰椎椎弓根螺钉钉道的优良率为96.7%(58/60),明显优于对照组的优良率85.0%(51/60)(P < 0.05);③结果表明对比单纯采用术中C臂,应用半自动Orthobot脊柱手术机器人系统结合术前CT与术中C臂置钉的准确率高、安全有效,但术中系统注册匹配时间增加、手术总耗时更长。 ORCID: 0000-0002-6549-7973(林云志) 中国组织工程研究杂志出版内容重点：人工关节;骨植入物;脊柱;骨折;内固定;数字化骨科;组织工程