Three-dimensional finite element analysis of intramedullary nail with different materials in the treatment of intertrochanteric fractures

Intramedullary nails are the common treatment options for femoral intertrochanteric fractures. However, aseptic loosening is considered to be one of the primary forms of failure that can be caused by the stress shielding between the bone and implants. The matching in mechanical properties of implant and bone is a key issue to prevent this failure. Polyetheretherketone (PEEK) and Function-graded (FG) materials are widely used in clinical because of their excellent mechanical properties. In this study, to investigate the biomechanical behaviors of intramedullary nails made of Ti-6Al-4V alloy, Stainless Steel (SS), PEEK and two FG materials, three-dimensional finite element models of intertrochanteric fracture femur with intramedullary nail were constructed with ABAQUS. The maximum von Mises stress on the femoral fracture surface fixed by PEEK intramedullary nail was the largest, followed by FG intramedullary nail, which help stimulate bone growth and subsequently reduce fracture healing time. Compared with traditional metal intramedullary nails, PEEK and FG implants might increase von Mises stress along the same path in the proximal femur. The results showed that PEEK and FG intramedullary nails obviously changed the stress distributions in the bone and reduced stress shielding. This finding indicated that PEEK and FG intramedullary nails have the potential to become alternatives to the conventional metal intramedullary nails.     

Effect of Dexmedetomidine infusion during hip fracture surgery on hemodynamic parameters and blood loss: A triple-blinded Randomized Clinical Trial

Introduction In this study, we aim to assess the intra-operative effect of dexmedetomidine administration on the hemodynamic parameters and bleeding volume during hip fracture surgery.Patients and methods we designed and implemented a triple-blinded randomized clinical trial to objectively compare the effects of 0.5 µg/kg/h infusion of dexmedetomidine with placebo (equal amount of normal saline) during hip fracture surgery. All included cases were between 30 and 70 years old and underwent surgery for fixation of a proximal femur fracture from September 26, 2020 until February 15, 2021. They were all ASA class I or II with preoperative hemoglobin levels of 10 mg/dL or higher. Surgical blood loss and hemodynamic parameters were documented.Results 76 patients were enrolled. There were no significant differences in baseline patient characteristics. The bleeding rate was 620 ± 190.0 mL for the normal saline group and 476 ± 177.98 mL in the dexmedetomidine group (P = 0.04). No significant effect on hemodynamic parameters was observed.Conclusion Based on the current study, intravenous infusion of dexmedetomidine during hip fracture surgery under general anesthesia reduced the amount of intraoperative bleeding without causing any significant hemodynamic disturbances.Registration number IRCT20191222045857N1 (Iranian Registry of Clinical Trials)     

治疗时机对创伤性漂浮膝预后的影响

目的:探讨不同的手术时机对于创伤性漂浮膝术后功能恢复的影响。方法:回顾性分析42例接受手术治疗并获得随访的漂浮膝患者术后膝关节功能恢复情况,将患者按接受手术的时间分为72h内（23例）和72h后（19例）手术组,根据Karlstrom标准对两组患者术后膝关节功能恢复情况进行评定,将评定结果使用SPSS10·0软件进行统计学分析。结果:随访11个月⁶年,平均26个月,72h内接受手术者膝关节功能恢复情况优10例,良7例,中5例,差1例;72h后接受手术者优2例,良5例,中4例,差8例,两组结果差异有显著性统计学意义（P<0·01）。结论:早期手术坚强内固定、早期进行功能锻炼对于漂浮膝损伤远期功能的恢复具有重要的意义。     

股骨头骨坏死样本空间结构的Micro-CT评估

目的以股骨头骨坏死样本的Micro-CT断层图像为基础，对其进行空间结构评估。方法2003年11月～2005年6月，收集股骨头骨坏死患者行全髋关节置换术时取出的股骨头样本6个，对样本进行Micro-CT断层扫描，获取股骨头骨坏死样本的计算机三维图像，图像空间分辨率为36μm×36μm×36μm。手工选取兴趣区，随后采用骨体积分数（BV／TV）、骨小梁间隙（Tb．Sp）、骨小梁厚度（Tb，Th）、骨小梁数目（Tb．N）、骨表面积体积比（BS／BV）、结构模型指数（SMI）、骨小梁模型因子（Tb．Pf）等三维空间参数分别对股骨头骨坏死标本的正常区域、硬化带和塌陷区进行评价。结果晚期股骨头骨坏死硬化区和塌陷区的骨小梁空间结构明显改变：硬化区Bv／Tv明显增加，Tb．Th明显增厚，Tb，Sp变窄，SMI与正常区域的骨小梁无差别；而塌陷区Bv／Tv明显减少，BS／BV增大，Tb．N和Tb．Pf增加，Tb，Th改变不明显。结论Micro-CT作为一种新的检测手段，能够在不损伤样本的条件下快速获取股骨头骨坏死样本断层图像，具有精度高、检测快、可进行三维重建分析的优点。晚期股骨头骨坏死不同区域的骨三维结构呈现出不同的空间结构特征。     

组织工程关节软骨梯度仿生支架的研究进展

由于良好的机械性能和生物相容性,组织工程支架已经成为修复和再生关节软骨缺损的重要方法。随着组织工程技术的不断发展,过去十年已经开发和测试了许多支架的制备和形成方法,但是理想再生支架的制备一直存在争议。关节软骨作为人体关节内的承重组织,其基质结构和细胞组成呈带状,并且从软骨表层至软骨下骨存在着几个平滑的自然梯度,包括细胞表型和数量、特异性的生长因子、基质的组成、纤维的排列、力学性能、营养和氧气的消耗量等均有较为明显的不同。因此,在再生支架的设计中有必要通过重现这些梯度来原位再生关节软骨。最近的文献报道已经有许多新型的梯度仿生支架用于模拟天然关节软骨的自然梯度,这些支架在结构上呈现出不同的机械、物理、化学或者生物梯度,并且取得了不错的修复效果。通过检索关于梯度支架治疗关节软骨缺损的相关文献,首先对天然关节软骨组织的结构、生物化学、生物力学、营养代谢等梯度特性进行研究和总结,然后对目前关节软骨梯度支架的最新设计和构建进行了归类,其次从材料构成(如水凝胶、纳米材料等)以及制备工艺(如静电纺丝、3D打印等)进一步加深对梯度支架的认识,最后讨论了梯度仿生支架在软骨原位组织工程技术中的前景和挑战,为梯度支架成功用于临床转化提供理论基础。     

Femoral neck shaft angle is not correlated with femoral version: A retrospective study of computed tomography scans

BackgroundAn understanding of femoral anteversion and neck-shaft angle (NSA) is essential to deliver optimal orthopaedic surgical care. Despite the importance, there is little research examining the relationship between femoral anteversion and the NSA in an adult population. This study sought to determine if there is a correlation between femoral neck shaft angle and version in skeletally mature adults using computed tomography (CT) scanograms.MethodsBetween January 2010 and June 2017, all skeletally mature patients who had received a CT scanogram of the lower extremity were reviewed. Exclusion criteria included: (1) radiographic evidence of osteoarthritis, (2) history of hip, femur, or knee surgery or trauma, (3) and anatomic abnormalities of the proximal femur including prior slipped capital femoral epiphysis or Legg-Calvé-Perthes disease. Both femoral version and NSA were measured by a musculoskeletal fellowship trained radiologist using CT scanograms. Correlation between femoral version and NSA was determined using coefficient of determination (R²) and Pearson correlation coefficient (r) for the group as a whole and for each sex.ResultsThere was no statistical correlation between femoral version and NSA for either the entire cohort or for each sex. For the entire cohort, R² = 0.0016 and r was 0.04 (p=0.45), for females, R² = 0.0005 and r was 0.0224 (p=0.72), and for males, R² = 0.0342 and r was 0.185 (p=0.07).ConclusionThere was no correlation between femoral version and NSA. This finding is beneficial for surgeons to understand the proximal femoral anatomy. Patients with an increased femoral NSA should not be assumed to have increased femoral anteversion.Level of EvidenceLevel III, Retrospective Cohort Study     

Plate selection for fixation of extra-articular distal humerus fractures: A biomechanical comparison of three different implants

Operative fixation of extra-articular distal humerus using a single posterolateral column plate has been described but the biomechanical properties or limits of this technique is undefined. The purpose of this study was to evaluate the mechanical properties of distal humerus fracture fixation using three standard fixation constructs.Two equal groups were created from forty sawbones humeri. Osteotomies were created at 80 mm or 50 mm from the tip of the trochlea. In the proximal osteotomy group, sawbones were fixed with an 8-hole 3.5 mm LCP or with a 6-hole posterolateral plate. In the distal group, sawbones were fixed with 9-hole medial and lateral 3.5 mm distal humerus plates and ten sawbones were fixed with a 6-hole posterolateral plate. Biomechanical testing was performed using a servohydraulic testing machine. Testing in extension as well as internal and external rotation was performed. Destructive testing was also performed with failure being defined as hardware pullout, sawbone failure or cortical contact at the osteotomy.In the proximal osteotomy group, the average bending stiffness and torsional stiffness was significantly greater with the posterolateral plate than with the 3.5 mm LCP. In the distal osteotomy group, the average bending stiffness and torsional stiffness was significantly greater with the posterolateral plate than the 3.5 mm LCP. In extension testing, the yield strength was significantly greater with the posterolateral plate in the proximal osteotomy specimens, and the dual plating construct in the distal osteotomy specimens. The yield strength of specimens in axial torsion was significantly greater with the posterolateral plate in the proximal osteotomy specimens, and the dual plating construct in the distal osteotomy specimens.Limited biomechanical data to support the use of a pre-contoured posterolateral distal humerus LCP for fixation of extra-articular distal humerus exists. We have found that this implant provided significantly greater bending stiffness, torsional stiffness, and yield strength than a single 3.5 mm LCP plate for osteotomies created 80 mm from the trochlea. At the more distal osteotomy, dual plating was biomechanically superior. Our results suggest that single posterolateral column fixation of extra-articular humerus fractures is appropriate for more proximal fractures but that dual plate fixation is superior for more distal fractures.     

Hydroxyapatite modified titanium promotes superior adhesion and proliferation of corneal fibroblast in comparison with pure titanium

To determine whether hydroxyapatite modified titanium promotes superior adhesion and proliferation of rabbit corneal fibroblast in comparison with pure titanium. · METHODS: We used bioactive hydroxyapatite to modify titanium surfaces. Fourth passage fibroblasts of rabbit cornea were seeded on hydroxyapatite modified titanium surfaces, pure titanium and glass surfaces. Cell adhesion, proliferation and morphology were detected at 24, 48, and 72 hours using a acridine orange stain. Further studies of cell morphology were performed using scanning electron microscopy. · RESULTS: Cell counts were significantly greater on hydroxyapatite modified titanium surfaces at each time point (P＜0.05). At 24 hours, cell spreading was greater on hydroxyapatite-coated titanium and glass than on the pure titanium. At 72 hours, compared with pure titanium and glass surfaces, the cells on hydroxyapatite modified titanium surfaces had greater spreading area and longer stress fibers. · CONCLUSION: Hydroxyapatite modified titanium promotes superior adhesion and proliferation of rabbit corneal fibroblast in comparison with pure titanium.     

Beagle sciatic nerve regeneration across a 30 mm defect bridged by chitosan/PGA artificial nerve grafts

Longitudinally oriented microstructures are essential for a nerve scaffold to promote the significant regeneration of injured peripheral axons across nerve gaps. In the current study, we present a novel nerve-guiding collagen-chitosan (CCH) scaffold that facilitated the repair of 30 mm-long sciatic nerve defects in beagles. The CCH scaffolds were observed with a scanning electron microscope. Eighteen beagles were equally divided into CCH group, autograft group and non-graft group. The posture and gait of each dog was recorded at 12 and 24 weeks after surgery. Electrophysiological tests, Fluoro-Gold retrograde tracing test, Histological assessment of gastrocnemius and immunofluorescent staining of nerve regeneration were performed. Our investigation of regenerated sciatic nerves indicated that a CCH scaffold strongly supported directed axon regeneration in a manner similar to that achieved by autologous nerve transplantation. In vivo animal experiments showed that the CCH scaffold achieved nerve regeneration and functional recovery equivalent to that achieved by an autograft but without requiring the exogenous delivery of regenerative agents or cell transplantation. We conclude that CCH nerve guides show great promise as a method for repairing peripheral nerve defects.     

人关节软骨源性微载体的制备

目的制备一种既能大量扩增人软骨细胞,又能作为细胞支架的人关节软骨源性微载体.方法切取人关节软骨,冷冻干燥后粉碎,筛取150～200μm的软骨颗粒,以质量分数为0.25%的胰蛋白酶37℃消化24 h,加入体积分数为1%的Triton X-100振荡72 h,在倒置相差显微镜下进行观察,并行HE、番红花O染色及软骨蛋白聚糖、Ⅱ型胶原免疫组化染色.将微载体经60Co照射灭菌后与人关节软骨细胞共同培养.结果倒置相差显微镜下可见关节软骨颗粒冻干后呈黄色,形状不一,可呈方形、多角形或不规则形,表面凹凸不平,可见多个陷窝.经胰蛋白酶和Triton X-100处理后,微载体呈淡黄色,关节软骨的基本形态消失,微载体绒毛化,呈绒球状或毛刷状,表面接触面积大幅度增加.微载体与软骨细胞在37℃培养箱中共同培养2 h时即见大量软骨细胞黏附于关节软骨源性微载体上.HE染色显示已无软骨细胞成分;番红花O染色弱阳性,提示仍残留少许糖胺多糖;软骨蛋白聚糖免疫组化染色阴性,提示微载体内软骨蛋白聚糖已被敲除;Ⅱ型胶原免疫组化染色阳性,提示微载体内Ⅱ型胶原仍然存留.结论经胰蛋白酶和Triton X-100处理的关节软骨颗粒,不但脱去了软骨的细胞成分、敲除了软骨蛋白聚糖、使之呈绒球状或毛刷状、增大了表面接触面积,而且保留了对软骨细胞黏附、增殖和再分化起重要作用的Ⅱ型胶原和GAG,经与人关节软骨细胞共培养,证实关节软骨源性微载体与软骨细胞的体外相容性良好.