Finite element analysis of femoral neck stress in relation to pelvic width

Hip resurfacing arthroplasty has been developed as an alternative to traditional total hip arthroplasty, in an effort to minimize the loss of native bone in young patients with symptomatic hip osteoarthritis. Femoral neck fracture following hip resurfacing is a unique complication; several risk factors are associated with this complication, including female gender. In the present study, we used finite element models of the proximal femur to simulate stresses across the femoral neck in pelvis models with varying widths. This analysis demonstrated an increase in hip reaction forces as the width of the pelvis increases, a condition that simulates a resurfacing condition in a female pelvis. This difference in peak stress on the femoral neck may explain the increased incidence of femoral neck fractures seen in female patients following hip resurfacing.     

臼杯假体高度对臼杯-骨界面应力应变影响的有限元分析

目的探究臼杯假体模拟植入Crowe Ⅱ/Ⅲ型DDH髋臼的不同高度时臼杯-骨界面间应力和应变分布特征。 方法基于3位Crowe Ⅱ/Ⅲ型DDH患者髋关节的CT扫描数据,利用计算机软件作髋臼三维建模,在距髋臼下缘连线垂直高度为15、21、30 mm处分别模拟植入臼杯模型,并转化为三维有限元网格模型,施加静力载荷,记录臼杯-骨界面的应力和应变数据,行配对t检验或Wilcoxon符号秩检验分析各组最大应力及应变的差异。 结果3组臼杯模型在距髋臼下缘连线垂直高度为21 mm处的最大应力值最小,分别为患者A 10.03 Mpa、患者B 17.67 Mpa和患者C 14.99 Mpa。在安装高度为15 mm和30 mm处,臼杯的最大应力值分别为患者A 20.64、12.03 Mpa,患者B 22.06、23.02 Mpa和患者C 34.72、17.88 Mpa。对15、21、30 mm处骨质、臼杯的最大应力及应变行两两配对检验显示各组差异无统计学意义(校正后P>0.0167)。不同安装高度下臼杯假体及假体周围骨组织应变量没有明显分布规律。 结论对于Crowe Ⅱ/Ⅲ型DDH患者行全髋关节置换术,适当上移臼杯旋转中心能减少臼杯假体最大应力。     

全髋关节置换前后股骨应力变化的有限元分析

目的:研究Chamley Elite骨水泥型和Summit近端多孔非骨水泥型股骨假体置换后股骨总体应力以及假体周围骨质区应力分布的变化。方法:根据Charnley Elite骨水泥柄和Summit非骨水泥柄假体形态建立三维有限元模型，并加载关节合力以及相关肌肉的肌力负荷，分析假体植入前后股骨总体应力模式并对股骨近端假体周围区域骨质应力分布进行分区量化研究。结果:两种假体植入后没有改变股骨总体的应力模式，应力峰值区域均位于全长股骨的中下段，但股骨应力峰值有所下降。股骨近端假体周围骨质等效应力水平出现了显著下降，下降最严重的区域为近段内侧象限即股骨距区，应力遮挡率分别达90．8％和95．3％；向假体远端应力水平逐渐增大，直至假体远段和末段水平应力值逐渐恢复并接近生理水平。就该两种不同固定方式的假体比较而言，引起的应力遮挡区域分布基本一致，应力下降程度Summit近端多孔非骨水泥型假体要高于Charnley Elite骨水泥型假体。结论:两种假体植入后均在股骨近端形成显著的应力遮挡，假体周围骨质应力大小和分布的改变是引起术后骨量丢失和假体松动的原因之一，也是术后股骨骨折发生的类型以术后肢体疼痛发生的力学基础。两种固定方式的假体均需通过进一步改进以减少应力遮挡。     

腰1椎体应力的有限元分析及分区

目的:利用有限元分析法研究在不同等级载荷及不同运动状态下腰1(L1)椎体皮质骨及松质骨的应力分布情况,并建立应力分区。方法:选取1例志愿者行胸腰段CT平扫,获取CT原始数据以DICOM导入Mimics、Geomagic、SoliderWorks、HyperMesh、Abaqus等有限元软件,构建正常胸腰段椎体(T11～L2)模型,在T11椎体上缘均匀施加力学载荷,将在载荷500N、弯矩7.5N·m下产生的所有运动状态称为α组,载荷600N、弯矩7.5N·m下产生的所有运动状态称为β组,载荷700N、弯矩7.5N·m下产生的所有运动状态称为γ组。选取L1椎体,从矢状面观正中分割分为上下两部分,上半部分标记为A区,下半部分标记为B区;从椎体正中央至椎体边缘呈同心圆均匀划分6段,上下各构成三维圆弧柱形6部分,从外缘到中央依次标记为1、2、3、4、5、6区,构成A1、A2、A3、A4、A5、A6、B1、B2、B3、B4、B5、B6区域共12部分;分别在α、β、γ三组中均匀采集上述12区域内皮质骨及松质骨应力数据,对皮质骨及松质骨相邻区域内应力值进行两两配对t检验,将差异具有统计学意义的两相邻区...     

V-Y advancement flaps for tumor excision defects of the eyelids

Resection of cutaneous malignancies of the medial canthus and lower lid create challenging wound closure problems. The V-Y flap closure technique achieves wound closure using adjacent tissue while minimizing closure tension. Twenty-three patients underwent resection of basal cell carcinomas in these two anatomical regions. In 22 patients a single V-Y flap was used to close the defect. In 1 patient two flaps were used. There were 2 patients with transient ectropion. No tissue loss or other complications occurred.     

Finite element stress analysis of the wrist joint without and with an endoprosthesis

The finite element analysis method was used to obtain the lateral deformation profile and values of the von Mises stress in the cortical and cancellous regions of the various bones in models of a selected space in the coronal plane of a human wrist joint, without and with a prosthesis. The prosthesis was the metacarpal component of the Trispherical design of the total wrist joint arthroplasty. The models included all the bones, the associated network of ligaments, and the intervening soft muscle tissue. Each type of model was completely constrained along its entire proximal surface and subjected to either a static point force (in the axial compressive or anteroposterior tensile direction) acting at the center of the distal tip of the third metacarpal cortical bone. For the models containing the prosthesis, a parametric study was conducted involving the method of anchorage of the prosthesis to the contiguous bones and the material of fabrication of the prosthesis. It was found that: (1) the axial force produces lower stresses in the bones compared with the anteroposterior one; (2) no clear-cut case can be advanced, from the stress viewpoint, for press-fitting the prosthesis to the contiguous bones rather than using bone cement for such anchorage; and (3) any alloy with modulus of elasticity in the 79 to 196 GPa range and Poisson's ratio of about 0.3 may be used to fabricate the prosthesis. The approximations used and the associated limitations of the work are fully discussed, as are the design implications and clinical significance of the results.     

Transposition movement of V-Y flaps for facial reconstruction.

BACKGROUND: The V-Y advancement flap has been widely used for the reconstruction of cutaneous defects for decades; however, the movement of a V-Y flap is sometimes limited, allowing only for rotation or advancement movement. To overcome this limitation, the present study introduces a transposition movement of the V-Y flap and assesses its clinical outcome for facial reconstruction. MATERIALS AND METHODS: A modified V-Y flap was designed with a single laterally based pedicle and transferred to the defect through a transposition movement. The transposition movement was demonstrated with photographs and the clinical outcome was described in six patients. RESULTS: This modified V-Y flap was reliable and robust, and could be moved easily with less tension. Meanwhile, the flap allowed for a primary closure of the defects along the nasolabial fold or preauricular crease. More importantly, all six patients achieved satisfactory functional and cosmetic outcomes in facial reconstruction. Temporary sensory alteration was common in the flap skin during the initial postoperative period, but improved as time passed and disappeared about 6 months later. CONCLUSION: This modified transposition V-Y flap may serve as an alternative option for aesthetic reconstruction of facial defects.     

同指尺侧岛状皮瓣远侧V-Y推进修复拇指指端缺损

目的 探讨一种修复拇指指端缺损的手术方法. 方法 对拇指指端缺损的患者采用同指尺侧岛状皮瓣远侧V-Y推进进行修复,术中切取皮瓣范围1.4 cm×2.0 cm～1.4 cm×2.5 cm,供区取前臂全厚皮片移植修复. 结果 2007年3月至2009年10月于临床应用10例,术后所有皮瓣和移植皮片均成活,伤口一期愈合.术后随访6～18个月,皮瓣质地柔软,无明显挛缩,末节指腹指纹重新建立,指间关节活动正常,无钩甲畸形发生,末节指腹两点辨别觉为5～6 mm. 结论 应用同指尺侧岛状皮瓣远侧V-Y推进的方法可以较好地修复拇指指端缺损.     

V-Y island flaps for repair of large perianal defects.

BACKGROUND: Some perianal diseases such as Paget disease and Bowen disease are extensive and require a wide circumferential excision including the entire anoderm of the anal canal. METHODS: We describe a technique of V-Y island flaps to cover the large perianal defects and the denuded anal canal. It is important to excise the base of the flaps in order to fit them into the anal canal. RESULTS: There were 10 women and 5 men with an average age of 54 years (range 32 to 77). The mean follow-up was 45 months (range 6 to 92). The underlying pathology included various kinds of neoplastic and nonneoplastic diseases. There were no major complications such as flap loss or infection. Most complications were minor, including superficial wound separation, flap hematoma, and anal stricture. Although initially all patients had some degree of incontinence for gas and liquid stool or discharge, none of them had significant fecal incontinence at the time of last follow-up. A diverting ileostomy or colostomy was created in 5 patients. Its role was not clear but it did help in the management of the wounds and minimized the pain.     

Closure of meningomyelocele defects with bilateral modified V-Y advancement flaps

BACKGROUND: Although several different methods were described in the literature, closure of large meningomyelocele defects presents a challenging problem. Wound dehiscence may lead to devastating complications. In this paper, the efficacy of the bilateral modified V-Y advancement flap procedure was investigated in terms of simplicity, donor-site morbidity, and reliability. PATIENTS AND METHODS: The authors presented 10 neonates treated with a modified subcutaneous advancement procedure. Unlike the typical V-Y advancement techniques, the apical extensions of the "V" flaps were elevated based on the paraspinous perforators. A standard closure algorithm was not followed, as the well-vascularized apical extensions facilitated intraoperative decision making for the most appropriate adaptation pattern, depending on the size, shape, and localization of the defect. As well as that, transposition of these apical flaps to the defect site was further supported by the advancement of the V-Y flaps to decrease the tension along the closure. RESULTS: Mean follow-up period was 13.6 months (range 3-37 months), and no complications that might be attributable to the operative procedure were observed. CONCLUSIONS: Utilization of bilateral modified V-Y flaps for the closure of large meningomyelocele defects is a simple and effective procedure. Main advantages of the method described in this paper may be listed as follows: simplicity, reliability due to coverage of the defect with well-vascularized flaps, minimal bleeding, decreased operative time, and no donor-site morbidity.     

A new simple technique to correct nipple inversion using 2 V-Y advancement flaps

Nipple inversion is a particular condition characterized by shorter galactophorous ducts, periductal fibrosis, and lack of soft tissue under the nipple base. It can be congenital or acquired, and it affects about 10% of the female population. Many operative techniques have been described seeking to correct this deformity, but a unique landmark strategy does not exist yet. Although acceptable results have been reported, every surgical technique has its drawbacks. We describe our 5 years' experience in correcting inverted nipples by using a simple personal approach. Between January 2004 and January 2009, we treated 52 patients presenting with nipple inversion using 2 V-Y dermoglandular flaps performed in the dermoglandular portion of the nipple. This method is effective in the correction of moderate and severe inverted nipple deformities. Follow-up period ranged from 1 to 6 years. Results showed recurrence in 1 case and postoperative complications in 3 patients. The authors have found this to be an ideal procedure for correcting inverted nipple; the use of an easy to perform V-Y flap ensures nipple protrusion and support, lactation, and minimal scars.     

Use of reverse triangular V-Y flaps to create a web space in syndactyly.

The authors describe a new technique for division in syndactyly. The web space is reconstructed using two reverse V-Y island triangular flaps. The flaps are raised both on the dorsal and the palmar aspect of the hand. This technique does not require the use of a skin graft. Fourteen syndactylies in 9 children-three incomplete (two congenital and one secondary to burn) and six complete-were treated using this technique. The results after a maximum 4-month follow-up and the advantages of the technique are discussed.     

Bilateral V-Y advancement flaps for the management of extensive defects of the perianal skin

Premalignant and malignant conditions of the skin may sometimes require excision of extensive areas of the skin and subcutaneous tissues. Coverage of the ensuing raw area may be afforded by allowing healing by secondary intention, skin grafts, or flaps. Wide excision of the perianal skin poses special problems. We describe the use of bilateral V-Y advancement flaps for the management of an extensive defect resulting from the wide excision of squamous cell carcinoma arising in scarred perianal skin.     

齿突下软骨基质融合部对枢椎骨折类型影响的有限元分析

目的 建立并验证精细枢椎三维有限元模型,应用该模型探讨在前、后不同载荷条件下枢椎齿突下软骨基质融合部骨质不同发育程度对枢椎骨折类型的影响.方法 基于正常成人颈椎CT图像建立枢椎精细三维有限元模型.模拟体外生物力学实验验证模型.模型经验证后对齿突施加不同角度载荷,通过降低枢椎软骨基质融合部位松质骨的弹性模量以模拟该部位松质骨发育不同程度,分析枢椎在2种不同约束条件下的应力、应变分布情况,并探讨可能发生的相应骨折类型.结果 模型验证结果与体外生物力学实验结果基本一致.边界约束模式1下齿突前部垂直和水平方向不同角度加载模型预测结果与屈曲位水平角度载荷下预测应力分布图显示,应力集中区域随加载角度变化而发生转变,骨折类型可由Ⅲ型转变为Ⅱ型齿突骨折.边界约束模式2下受不同水平载荷角度加载后,模型预测骨折类型可由对称性Hangman骨折向不对称性Hangman骨折的转变.垂直方向上不同角度载荷下,预测骨折类型可由对称性Hangman骨折向Ⅱ型齿突骨折转变.齿突下软骨基质融合部位松质骨的发育程度不改变枢椎在垂直、水平、屈曲位不同角度受力下的应力集中带分布情况,皮质骨承受主要应力.结论 枢椎骨折的发生类型除了与所遭受暴力的方向、大小有关外,同时还与受伤瞬间寰枢椎相对应的位置情况和枢椎齿突的解剖差异有关.体外对枢椎骨折的生物力学研究实验中,除了加载暴力的方向外,尸体标本的固定与加载方式直接影响枢椎骨折类型的复制.齿突下软骨基质融合部对枢椎骨折类型无明显影响.     

不同载荷下腰1椎体内应力分布规律的有限元分析

目的:观察腰1(L1)椎体在不同载荷作用下椎体内应力分布情况,探讨其应力分布规律及临床意义.方法:选取1例27岁健康男性志愿者,以层厚1 mm进行T12～L2脊柱节段CT扫描,将原始数据存盘.运用3D软件、Auto CAD系统及ANSYS 6.0有限元软件建立正常人体胸腰段(T12～L2)运动节段的三维有限元模型.在T12椎体上表面施加不同等级的压力(400N、600N、800N、1000N、1200N),模拟脊柱的轴向压缩载荷;在T12椎体上表面施加不同等级压力(400N、600N、800N、1000N、1200N)的同时再施30N·m的弯矩,模拟脊柱的屈曲压缩载荷.将连接L1椎体上下终板凹面最低点的连线7等份,在此基础上将T1椎体中的松质骨划分为7个具有统计节点的层面,每个统计层面划分成9个统计区(椎体前部A1、A2和A3区,椎体中部M1、M2和M3区,椎体后部P1、P2和P3区).测量L1椎体松质骨中间3个层面9个统计区的平均应力值,将9个统计区划分成6个组,分别为Ⅰ组A1、A2、A3,Ⅱ组M1、M2、M3,Ⅲ组P1、P2、P3,Ⅳ组A1、M1、P1Ⅴ组A2、M2、P2,Ⅵ组A3、M3、P3.比较同一等级载荷下9个统计区的应力分布情况,并对6个组内的松质骨应力值进行两两配对t检验,分析L1椎体内不同载荷作用下应力分布情况.结果:轴向加载时同一等级载荷下,Ⅲ组内P2松质骨平均应力值与P1、P3比较,Ⅳ组内P1与A1、M1比较,Ⅴ组内P2与A2、M2比较,Ⅵ组内P3与A3、M3比较,差异均有统计学意义(P＜0.05);而Ⅰ组、Ⅱ组内的数据经两两比较均无统计学差异(P＞0.05);椎体后部P区(P1,P2,P3)的应力值与M区、A区比较最大,其中P2区应力最大.屈曲加载时同一等级载荷下,Ⅰ组内A2与A1、A3比较,Ⅱ组内M2与M1、M3比较,Ⅲ组内P2与P1、P3比较,Ⅳ组内A1与M1、P1比较,Ⅴ组内A2与M2、P2比较,Ⅵ组内A3与M3、P3比较,差异均有统计学意义(P＜0.05);Ⅰ组内A1与A3比较,Ⅱ组内M1与M3比较,Ⅲ组内P1与P3比较,Ⅳ组内M1与P1比较,均无统计学差异(P＞0.05);椎体前部A区(A1,A2,A3)的应力值与M区、P区比较最大,A2区应力最大.结论:L1椎体在不同载荷作用下,松质骨内存在着应力分布的集中趋势;轴向加载时应力集中的部位靠近椎体后缘中央,屈曲加载时应力集中的部位靠近椎体前缘中央.     

Interdigitating fasciocutaneous gluteal V-Y advancement flaps for reconstruction of sacral defects

The authors describe a modification of the classic gluteal bilateral V-Y advancement flap for sacral defect closure. After initial debridement, the V-Y design is marked on both sides of the defect. The incision is carried down to the fascia of the underlying gluteus maximus muscle. The upper and lower arms of the flaps are elevated and advanced on the gluteal muscle toward the midline, interdigitating each opposing arm. The overall result is a zigzag, broken midline suture. This procedure was carried out in 14 patients with sacral pressure sores and in 1 patient with a chronic pilonidal sinus. All flaps survived without major problems. There were no recurrences during the 6 to 16 months of follow-up. The interdigitating fasciocutaneous V-Y gluteal flap design is effective in breaking the midline vertical scar and preserving the gluteus maximus muscle.     

Stepladder V-Y advancement flaps for resurfacing various shaped defects of the sacrogluteal region

Gluteal stepladder V-Y advancement musculocutaneous and fasciocutaneous flaps were used for resurfacing of various shaped sacrogluteal defects. A total of 27 patients with sacrogluteal defects were treated using this technique. Twenty-four patients had sacral pressure sores, 2 patients had a pilonidal sinus, and 1 had a low thermal burn of the gluteal region. The shape of defects varied including 12 elliptic, 5 inverted heart-shaped, 4 pentagon, 4 diamond, and 2 other shapes. There were no problems regarding flap survival even at the tip of step segments. In all patients, easy resurfacing of the defects and satisfactory recontour of the gluteal region was obtained without linear scars crossing the gluteal fissure. Since the segments of the flap are similar to the defect, defects of various shapes are easily covered, and trimming of normal skin tissue becomes unnecessary or minimal. On inserting a triangular flap in the gluteal fissure, excellent recontour of the sacrogluteal region can be achieved. Received: 19 October 1998 / Accepted: 20 January 1999