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.     

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。     

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.     

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.     

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.     

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.     

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.     

股骨生物力学特性的有限元分析

目的对股骨的生物力学特性进行研究以指导临床工作。方法根据股骨的螺旋CT片,采用计算机辅助技术建立股骨的三维有限元模型,通过分别对模型施加350、700、1400和2100N的垂直载荷及行走载荷,观察股骨的应力分布,并对结果做出分析。结果在各种载荷下,股骨颈和股骨干各有一个应力集中部位。股骨颈的应力集中部位在小转子上方、稍偏股骨颈后方处,应力值分别为6.3、12.6、25.1、37.7和20.8MPa;而股骨干以其内侧中下1/3交界处的应力最大,应力值分别为7.3、14.5、29.0、43.5和31.3MPa。结论股骨颈处的压力骨小梁和股骨距是主要的承重结构,内固定的放置应与压力骨小梁的方向一致,并紧贴股骨距;股骨干应力骨折好发于其中下1/3交界处,与此处应力集中有关。     

有限元分析应用于全髋关节置换中的研究进展

全髋关节置换术是治疗多种髋关节疾病的一种有效方式,多项研究发现术后假体的稳定性及多种并发症的发生均与关节周围生物力学因素有关,但髋关节复杂的解剖结构使得在体内和实验室对其进行生物力学研究非常困难。有限元分析对复杂物体的生物力学性能分析具有独特的优势,现已被成功应用于人体骨骼、关节和肌肉的相关研究,在骨科生物力学领域占有重要的地位。本文对近几年来有限元分析应用于全髋关节置换中的相关研究进行了较详细的总结,归纳了目前最新的研究进展及存在的问题,为以后的研究指明了方向。     

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     

Finite element analysis of impact loads on the femur

Objective: To investigate the stress distribution and fracture mechanism of proximal femur under impact loads. Methods: The image data of one male' s femur were collected by the Lightspeed multi-lay spiral computed tomography. A 3D finite element model of the femur was established by employing the finite element software ANSYS, which mainly concentrated on the effects of the directions of the impact loads arising from intense movements and the parenchyma on the hip joint as well as those of the femur material properties on the distribution of the Mises equivalent stress in the femur after impact. Results: The numerical results about the effects of the angleδof the impact loads to the anterior direction and the angleγof the impact loads to the femur shaft on the bone fracture were given. The angleδhad larger effect on the stress distribution than the angleγ, which mainly represented the fracture of the upper femur including the femoral neck fracture when the posterolateral femur was impacted. This result was consistent with the clinical one. The parenchyma on the hip joint has relatively large relaxation effect on the impact loads. Conclusions: A 3D finite element analysis model of the femoral hip joint under dynamic loads is successfully established by using the impact dynamic theory.