Stress analysis of a centrally fractured rib fixated by an intramedullary screw

The stress on an intramedullary screw rib fixation device holding together a centrally fractured human rib under in vivo force loadings was studied using finite element analysis (FEA). Validation of the FEA modelling using pullout from porcine ribs proved FEA to be suitable for assessing the structural integrity of screw/bone systems such as rib fixated by a screw. In the human rib fixation investigation, it was found that intramedullary bioresorbable Bioretec screws can fixate centrally fractured human ribs under normal breathing conditions. However, under coughing conditions, simulation showed Bioretec fixating screws to bend substantially. High stresses in the screw are mainly the result of flexion induced by the force loading, and are restricted to thin regions on the outside of the screw shaft. Stiffer screws result in less locally intense stress concentrations in bone, indicating that bone failure in the bone/screw contact regions can be averted with improvements in screw stiffness.     

骨水泥填充治疗桡骨远端骨质疏松骨折

目的:探讨骨水泥填充治疗桡骨远端骨质疏松骨折的方法。方法:对本科2000以来对8例桡骨远端骨质疏松骨行有限切开、关节面撬拨复位后注入骨水泥填充关节软骨下缺损治疗。结果:全部病例获得随访10-68月,平均22月。所有患者术后1周内肿胀消失,3～4周功能恢复接近正常。X线检查显示骨折愈合良好,无延迟愈合或不愈合。患者自我感觉5例表示满意,2例表示基本满意,1例表示不满意,满意率87.5%。结论:有限切开、关节面撬拨复位后注入骨水泥填充关节软骨下缺损是治疗桡骨远端骨质疏松骨折的有效方法。     

In vitro performance of intramedullary cement restrictors in total hip arthroplasty

Contemporary cementing techniques in total hip arthroplasty include the use of a cement restrictor to occlude the intramedullary canal. As there are many different designs currently available it was the aim of our study to compare the stability of eight different systems. We investigated the displacement and the ability to occlude the femur of these cement restrictors during standardised cementing of artificial and fresh frozen femora. The maximal intramedullary pressures and the displacement of the plugs were continuously recorded and statistically evaluated.The results revealed significant differences between the tested cement restrictors. The expandable REX Cement Stop and the Exeter Plug achieved the highest stability and the least cement leakage. The more rigid designs (Palacos Plug, BUCK, Universal) in contrast showed inferior performance. Our biomechanical study emphasises the importance of cement restrictor selection, which can have a crucial influence on the fixation of a cemented total hip replacement.     

Geometry of human ribs pertinent to orthopedic chest-wall reconstruction

Orthopedic reconstruction of blunt chest trauma can aid restoration of pulmonary function to reduce the mortality associated with serial rib fractures and flail chest injuries. Contemporary chest wall reconstruction requires contouring of generic plates to the complex surface geometry of ribs. This study established a biometric foundation to generate specialized, anatomically contoured osteosynthesis hardware for rib fracture fixation. On human cadaveric ribs three through nine, the surface geometry pertinent to anatomically conforming osteosynthesis plates was characterized by quantifying the apparent rib curvature C(A), the longitudinal twist alpha(LT) along the diaphysis, and the unrolled curvature C(U). In addition, the rib cross-sectional geometry pertinent to intramedullary fixation strategies was characterized in terms of cross-section height, width, area, and cortex thickness. The rib surface exhibited a curvature C(A) ranging from 3.8 m(-1) in the anteromedial section of rib seven to 17.3 m(-1) in the posterior section of rib three. All ribs had in common a longitudinal twist alpha(LT), ranging from 41-60 degrees. The unrolled curvature C(U) decreased gradually from ribs three to five, and increased gradually with reversed orientation from rib six to nine. The cross-sectional area remained constant along the rib diaphysis. However, the medullary canal increased in size from 29.9 mm(2) posteriorly to 41.2 mm(2) in anterior rib segments. Results of this biometric rib characterization describe a novel strategy for intraoperative plate contouring and provide a foundation for the development of specialized rib osteosynthesis strategies.     

Calcium phosphate cement augmentation of cancellous bone screws can compensate for the absence of cortical fixation

An obvious means to improve the fixation of a cancellous bone screw is to augment the surrounding bone with cement. Previous studies have shown that bone augmentation with Calcium Phosphate (CaP) cement significantly improves screw fixation. Nevertheless, quantitative data about the optimal distribution of CaP cement is not available. The present study aims to show the effect of cement distribution on the screw fixation strength for various cortical thicknesses and to determine the conditions at which cement augmentation can compensate for the absence of cortical fixation in osteoporotic bone. In this study, artificial bone materials were used to mimic osteoporotic cancellous bone and cortical bone of varying thickness. These bone constructs were used to test the fixation strength of cancellous bone screws in different cortical thicknesses and different cement augmentation depths. The cement distribution was measured with microCT. The maximum pullout force was measured experimentally. The microCT analysis revealed a pseudo-conic shape distribution of the cement around the screws. While the maximum pullout strength of the screws in the artificial bone only was 30±7 N, it could increase up to approximately 1000 N under optimal conditions. Cement augmentation significantly increased pullout force in all cases. The effect of cortical thickness on pullout force was reduced with increased cement augmentation depth. Indeed, cement augmentation without cortical fixation increased pullout forces over that of screws without cement augmentation but with cortical fixation. Since cement augmentation significantly increased pullout force in all cases, we conclude that the loss of cortical fixation can be compensated by cement augmentation.     

顺行髓内钉、逆行髓内钉及锁定加压钢板内固定治疗股骨远端骨折的对比研究

摘要目的：探讨顺行髓内钉、逆行髓内钉及锁定加压钢板内固定3种方法治疗股骨远端骨折患者的疗效。方法：对2011年1月至2012年12月间我院收治的101例股骨远端骨折进行临床随机分组手术,分别在手术中使用顺行髓内钉、逆行髓内钉以及锁定加压钢板内固定。对三组患者手术时间、术中出血量以及切口长度等一般情况进行比较分析,同时采用Harris评分系统对三组患者术后恢复情况进行分析比较。结果：经过手术治疗后,逆行髓内钉组Harris评分显著高于其他两组（P〈0．05）。另外,逆行髓内钉组手术过程短、出血量少、手术切口小,上述指标与其他两组比较均有统计学意义（P〈0．05）。结论：股骨远端骨折行逆行髓内钉治疗的疗效优于顺行髓内钉以及锁定加压钢板内固定,具有手术时间短、术中出血少、切口小等优点,能够有效提高术后膝关节功能的恢复,值得临床推广使用。     

同期双侧胸腔镜联合肋骨接骨板内固定治疗双侧多发肋骨骨折的体会

目的:探讨同期双侧胸腔镜联合肋骨接骨板内固定治疗双侧多发肋骨骨折的方法及临床疗效评价。方法:对13例双侧多发肋骨骨折患者施行同期双侧胸腔镜联合肋骨接骨板内固定治疗,对于合并胸内损伤有胸腔探查指征者,先手术治疗损伤重的一侧;对于肋骨固定为主者,先手术治疗损伤较轻的一侧。固定材料选用形状记忆环抱接骨板。结果:全组13例患者均临床治愈,术后双侧胸痛明显缓解,胸廓畸形纠正,缩短ICU治疗时间,无明显并发症发生。结论:双侧多发肋骨骨折行同期双侧胸腔镜联合肋骨接骨板内固定治疗,能有效恢复胸廓的完整性,减少并发症,改善预后,而且具有创伤小的优点。     

可吸收螺钉内固定治疗多发性肋骨骨折的临床疗效

目的:分析可吸收螺钉内固定治疗多发性肋骨骨折的临床疗效。方法:选择2013年10月-2015年10月在我院接受治疗的多发性肋骨骨折患者89例作为研究对象,根据内固定材料不同将患者分为研究组和对照组。研究组45例患者采用可吸收肋骨钉内固定治疗,对照组44例患者采用记忆合金接骨板内固定治疗。观察并比较两组患者的临床疗效及术后并发症的发生情况。结果:与对照组比较,研究组患者术中出血量少,术后胸痛缓解时间以及下床活动时间较早,差异均具有统计学意义(P0.05);两组患者的手术时间、术后引流时间、住院时间比较,差异均无统计学意义(P0.05);研究组患者并发症的发生率(6.67%)明显低于对照组(20.45%),差异具有统计学意义(P0.05)。结论:可吸收肋骨钉内固定治疗多发性肋骨骨折具有术中出血量少、术后胸痛缓解时间和下床活动时间快的特点,可作为临床治疗首选材料。     

股骨骨折术后1年随访骨愈合模型的有限元分析

目的：对股骨骨折髓内钉术后1年骨愈合模型快速建模,通过有限元分析研究对比术前术后模型,通过术前判定内固定取出后骨折断端是否断裂。方法：运用Mimics、Geomagic Studio、Abaqus等软件采用快速个体化建模方法对股骨骨折髓内钉术后1年内固定取出术前后的多层螺旋CT数据进行快速建立模型,术前模型模拟剥除钢板后进行有限元分析,施加人体单腿站立时的静力载荷和约束,并将分析结果与术后模型进行对比,观察米塞斯应力分布情况、最大值及其所处部位。结果：按照材料属性进行区别显示米赛斯应力的最大值及最小值,在不同应力载荷下,手术前后各类型材料的米赛斯应力最大值及最小值部位相同,各类型材料中,最大值均没有位于骨折断端,不同方法的最大应力值部位相近,均在股骨中远端1/4交界处,手术前后应力分布基本相同。结论：采用个体化建模方法可以对骨折内固定取出前的骨愈合模型进行运算分析,快速预判术后是否导致骨折断端断裂。     

两种方法治疗桡骨远端骨折的疗效比较研究

目的:比较采用T形钢板内固定和闭合复位石膏外固定这两种方法治疗桡骨远端骨折的疗效研究。方法:选取我院2008年3月至2011年12月间的76例桡骨远端骨折患者,并按照治疗方法不同分为2组,41例患者进行T形钢板内固定,其余35例患者进行复位后石膏外固定。并借助X线对比分析桡骨远端骨折复位前后及临床愈合时桡骨腕关节的掌倾角、尺偏角及桡骨轴向缩短长度变化等数据,并根据改良的Shea评定法对临床疗效进行比较。结果:针对桡骨远端不稳定型骨折的患者,T形钢板内固定组的优良率要优于石膏外固定组的疗效(P<0.05);而对于稳定性桡骨远端骨折的患者,两组之间的优良率没有明显差异(P>0.05)。结论:对于桡骨远端不稳定骨折的患者,应优先选择T形钢板内固定手术方法,而对于稳定性骨折患者这两种治疗方法均可采用。     

A Biomechanical Comparison of Expansive Pedicle Screws for Severe Osteoporosis: The Effects of Screw Design and Cement Augmentation

Expansive pedicle screws significantly improve fixation strength in osteoporotic spines. However, the previous literature does not adequately address the effects of the number of lengthwise slits and the extent of screw expansion on the strength of the bone/screw interface when expansive screws are used with or without cement augmentation. Herein, four designs for expansive pedicle screws with different numbers of lengthwise slits and different screw expansion levels were evaluated. Synthetic bones simulating severe osteoporosis were used to provide a comparative platform for each screw design. The prepared specimens were then tested for axial pullout failure. Regardless of screw design, screws with cement augmentation demonstrated significantly higher pullout strength than pedicle screws without cement augmentation (p < 0.001). For screws without cement augmentation, solid screws exhibited the lowest pullout strength compared to the four expansive groups (p < 0.01). No significant differences in pullout strength were observed between the expansive screws with different designs (p > 0.05). Taken together, our results show that pedicle screws combined with cement augmentation may greatly increase screw fixation regardless of screws with or without expansion. An increase in both the number of slits and the extent of screw expansion had little impact on the screw-anchoring strength. Cement augmentation is the most influential factor for improving screw pullout strength.     

Experimental and probabilistic analysis of distal femoral periprosthetic fracture: a comparison of locking plate and intramedullary nail fixation. Part B: probabilistic investigation

The following is Part B of a two-part study. Part A evaluated, biomechanically, intramedullary (IM) nails versus locking plates for fixation of an extra-articular, metaphyseal wedge fracture in synthetic osteoporotic bone. Part B of this study introduces deterministic finite element (FE) models of each construct type in synthetic osteoporotic bone and investigates the probability of periprosthetic fracture of the locking plate compared with the retrograde IM nail using Monte Carlo simulation. Deterministic FE models of the fractured femur implanted with IM nail and locking plate, respectively, were developed and validated using experimental data presented in Part A of this study. The models were validated by comparing the load-displacement curve of the experimental data with the load-displacement curve of the FE simulation with a root-mean square error of less than 3?mm. The validated FE models were then modified by defining the cortical and cancellous bone modulus of elasticity as uncertain variables that could be assumed to vary randomly. Monte Carlo simulation was used to evaluate the probability of fracture (POF) of each fixation. The POF represents the cumulative probability that the predicted shear stresses in the cortical bone will exceed the expected shear strength of the cortical bone. This investigation provides information regarding the significance of post-operative damage accumulation on the POF of the implanted bones when the two fixations are used. The probabilistic analysis found the locking plate fixation to have a higher POF than the IM nail fixation under the applied loading conditions (locking plate 21.8% versus IM nail 0.019%).     

The influence of proximal stem geometry and surface finish on the fixation of a double-tapered cemented femoral stem

In this study, the in vitro fixation of four otherwise identical double-tapered stem-types, varying only in surface finish (polished or matte) and proximal stem geometry (with or without flanges) were compared under two conditions. First, four specimens of each stem type were tested with initially bonded stem–cement interfaces, representing early post-operative conditions. Then, simulating conditions a few weeks to months later, stems were implanted in unused synthetic femurs, with a thin layer coating the stem to prevent stem–cement adhesion. Per-cycle motions were measured at both cement interfaces throughout loading. Overall, surface finish had the smallest relative effect on fixation compared to flanges. Flanges increased axial fixation by 22 μm per-cycle, regardless of surface finish (P=0.01). Further, all stems moved under dynamic load at the stem–cement interface during the first few cycles of loading, even without a thin film. The results indicate that flanges have a greater effect on fixation than surface finish, and therefore adverse findings about matte surfaces should not necessarily apply to all double-tapered stems. Specifically, dorsal flanges enhance the stability of a tapered cemented femoral stem, regardless of surface finish.     

弹性髓内钉和钢板固定对儿童股骨干中段骨折的疗效比较

目的:观察并比较弹性髓内钉(ESIN)与钢板固定(PF)治疗儿童股骨干中段骨折的临床疗效。方法:选择2013年2月至2016年12月我院收治的股骨干中段骨折患儿90例,依据治疗方法不同分为ESIN组和PF组。ESIN组(n=45)采用弹性髓内钉固定,PF组(n=45)采用钢板固定,比较两组患者手术时间、手术切口、术中失血量、术后切口引流量等手术指标,随访评估患者住院时间、完全负重时间、骨折愈合时间;按Flynn评定标准比较两组患者的最终治疗结果。结果:两组患者术中失血量、术后引流量比较差异无统计学意义(P0.05),ESIN组患者手术切口显著小于PF组(P0.05),手术时间、透视时间、完全负重时间均显著短于PF组(P0.05),临床疗效明显优于PF组(P0.05)。结论:与钢板固定比较,弹性髓内钉在手术时间、透视时间显著短于钢板固定,临床疗效明显优于钢板固定,可作为儿童股骨干骨折内固定的首选材料。     

肋骨接骨板的临床应用研究

目的:探讨肋骨接骨板治疗外伤性连枷胸的方法和疗效。方法:将我院2008年2月至2011年3月收治的47例外伤性连枷胸患者的临床资料进行回顾性分析。分为内固定组(肋骨接骨板内固定术)21例和保守组(呼吸机气体内固定、加压包扎固定)26例。对二组病例的恢复情况及并发症进行对照比较。结果:骨折全部骨性愈合,内固定组并发症发生率低于保守组(P<0.05),恢复优于保守组,差异有统计学意义(P<0.05)。结论:肋骨接骨板内固定术治疗外伤性连枷胸安全可行,且术后并发症少,值得推广。     

不同颌间牵引结合可吸收内固定材料在下颌骨骨折的重建研究

目的:下颌骨骨折患者采用可吸收内固定材料进行固定,同时结合牙弓夹板或自攻钛钉进行术后颌间牵引固定,探讨两种牵引方式对患者口腔情况和术后咬合关系恢复的促进作用。方法:对65例下颌骨骨折病例在完成骨折坚固内固定的基础上分别应用牙弓夹板和自攻钛钉进行颌间牵引,14 d后拆除颌间牵引,术后3-6月进行复查,对患者术后及复查期间口腔情况和咬合关系进行评估,采用两组间t检验进行统计学分析。结果:所有35例患者伤口均一期愈合。两种技术相结合,即使全面部骨折和陈旧性骨折都获得了良好的疗效,不同颌间牵引结果显示采用自攻钛钉治疗更加简便,口腔卫生情况明显好于采用牙弓夹板的患者;复查显示两组患者咬合关系恢复理想,两者骨折愈合、张口度及咬合关系无明显差异。结论:采用可吸收材料进行颌骨固位是一种较先进的坚固内固定方法,颌间自攻钛钉是恢复及维持咬合关系较为理想的治疗方法,两者结合可以获得满意的效果,值得临床推广。     

Reconstruction of mandibular defects with revascularized free rib grafts.

Two cases of hemimandibular reconstructions with revascularized free rib grafts are presented. The viability of the transplants was confirmed by bone scans and biopsy, even though the main nutrient vessels providing the intramedullary blood flow were not included in these grafts (and only the periosteal circulation was utilized). The removal of a rib graft without the nutrient vessel eliminates the need for a complicated posterior dissection, close to the costovertebral joint. Revascularized free bone grafts have a greater chance of survival, provide more rapid healing, offer less risk of absorption, and are more resistant to infection than conventional bone grafts.     

A new technique for internal fixation of femoral fractures in mice: impact of stability on fracture healing

Mouse models are of increasing interest to study the molecular aspects of fracture healing. Because biomechanical factors greatly influence the healing process, stable fixation of the fracture is of interest also in mouse models. Unlike in large animals, however, there is a lack of mouse models which provide stable osteosynthesis. The purpose of this study was therefore to develop a technique for a more stable fixation of femoral fractures in mice and to analyze the impact of stability on the process of fracture healing. The new technique introduced herein includes an intramedullary pin and an extramedullary metallic clip. Ex vivo biomechanical analysis revealed a significantly higher implant stiffness of our pin-clip technique when compared with previously described intramedullary fixation techniques. In vivo, we studied the course of healing after the more stable fixation with our pin-clip technique and compared the results with that observed after unstable fixation with the pin-clip technique after cutting the clip. After 2 and 5 weeks of fracture healing radiological analysis demonstrated that the more stable fixation with the pin-clip technique results in a significantly higher union rate compared to the unstable fixation. Torsional stiffness at 5 weeks was almost 3-fold of that measured after unstable fixation. Histomorphological analysis further showed that fractures stabilized with the pin-clip technique healed with a smaller periosteal callus area, an increased fraction of bone and a reduced amount of fibrous tissue. Of interest, the pin-clip fixation showed reliable union after 5 weeks, whereas the unstable pin fixation did not regularly achieve adequate fracture healing. In conclusion, we introduce a novel, easily applicable internal osteosynthesis technique in mice, which provides rotational stability after femoral fracture fixation. We further show that a more stable osteosynthesis significantly improves the process of fracture healing also in mice.     

弹性髓内钉与接骨板内固定治疗儿童股骨干骨折的临床疗效对比研究

摘要 目的：对比弹性髓内钉与接骨板内固定治疗儿童股骨干骨折的临床疗效。方法：本研究为回顾性研究,选取我院于2018年3月~2019年8月期间收治的儿童股骨干骨折患者98例,根据固定方式的不同将患儿分为A组（n=50,接骨板内固定治疗）和B组（n=48,弹性髓内钉治疗）,观察两组优良率、术前/术后相关指标及并发症发生情况。结果：B组的优良率高于A组（P<0.05）。B组手术时间、切口长度短于A组,术中出血量少于A组（P<0.05）。B组骨折愈合时间、住院时间、手术至内固定拆除时间、取出内固定手术时间短于A组（P<0.05）。两组患儿并发症发生率对比,差异无统计学意义（P>0.05）。结论：相对于接骨板内固定治疗,弹性髓内钉治疗儿童股骨干骨折,疗效更好,可有效改善术中、术后指标,且不增加并发症的发生率。