股骨干骨折锁定板内固定治疗的有限元分析

目的研究股骨干骨折采用锁定板内固定,选择不同螺钉位置情况下,锁定板及螺钉最大应力情况。方法通过采集23位健康志愿者左股骨CT数据及12孔锁定板外形数据进行有限元分析前处理,并导入有限元分析软件进行装配和求解。结果不同固定方式下的锁定板及螺钉上最大应力值均出现在最内侧螺钉处,即最靠近骨折线处。对于简单骨折,随着最内侧固定螺钉的外移,锁定板及螺钉上分布的最大应力均逐渐减小;对于粉碎性骨折,则随着最内侧固定螺钉的外移,锁定板及螺钉上分布的最大应力均逐渐增大。结论对于股骨干骨折锁定板内固定,若为简单骨折,应在保证固定强度的前提下使最内侧螺钉尽量远离骨折端;若为粉碎性骨折,则应在保证固定强度的前提下使最内侧螺钉尽量靠近骨折端。     

异体骨接骨板联合不同螺钉治疗股骨干骨折有限元分析

目的对比分析异体骨接骨板分别联合可吸收螺钉(聚-DL-乳酸)和钛合金螺钉(Ti-6Al-4V)治疗股骨干骨折的应力分布情况,验证可吸收螺钉的强度,为临床提供力学依据。方法利用螺旋CT扫描股骨,将扫描数据以DICOM格式导入mimics软件中,建立股骨三维模型。在proe5.0中建立接骨板模型和螺钉模型(简化为圆柱),装配完成后,导入ansys12.0划分网格、材料赋值,并施加700 N轴向载荷、15 N·m弯曲载荷、15 N·m扭转载荷。结果在三种载荷下6根可吸收螺钉最大主应力的最大值为5.75 Mpa、6根钛合金螺钉最大主应力的最大值为24.9 Mpa;两种不同螺钉固定下,股骨和接骨板的应力分布基本相同。结论可吸收螺钉适应于同种异体骨接骨板的固定,与钛合金螺钉相比,具有减少骨头螺钉孔处的应力遮挡的优点。     

利用有限元探究内固定治疗股骨颈骨折的生物力学研究

目的:利用有限元分析研究不同内固定治疗Pauwels Ⅲ型股骨颈骨折的生物力学特点。方法:选取1名健康受试者的股骨CT数据进行三维重建,骨折造模,装配动力髋螺钉、锁定加压钢板、三枚空心钉、四枚空心钉和髓内钉,建立有限元模型,在股骨头顶端轴向加载1400 N应力。研究不同内固定的应力分布和位移分布、股骨的应力分布和位移分布,并比较内固定和股骨模型的应力峰值和位移峰值。结果:股骨和内固定应力较大区域均分布于股骨颈及股骨干部位,且在骨折线附近均出现应力增大的现象;内固定位移分布主要集中于股骨头内螺钉尖端位置,股骨位移集中于股骨头顶端,应力加载位置。四枚空心钉的应力最小,峰值为135.3 MPa;锁定加压钢板的应力最大,峰值为405.9 MPa,但锁定加压钢板的位移12.3 mm为最小峰值;三枚空心钉的位移18.8 mm为最大峰值;三枚空心钉固定时,股骨受力最小,应力峰值为36.8 MPa,但股骨位移最大,峰值为19.3 mm;锁定加压钢板固定时,股骨受力104.6 MPa为最大应力峰值而位移12.6mm为最小位移峰值。结论:锁定加压钢板在固定股骨颈骨折时稳定性最高,但股骨和内固定承受更大的压力和剪切力;动力髋螺钉固定短期内促进骨折愈合较有优势,但长期固定时髓内钉固定更佳。     

单臂外固定架治疗股骨粗隆间骨折股骨应力变化的三维有限元分析

[目的]研究单臂外固定架治疗股骨粗隆间骨折中股骨应力分布情况,为临床治疗提供理论依据。[方法]将股骨CT图像导入Mimics软件,建立股骨全长三维有限元模型。将模型输入Geomagic软件,对不规则的模型表面进行点云处理。在ANSYS软件建立单臂外固定架固定EvansⅠ型股骨粗隆间骨折模型,并在股骨头顶端施加轴向载荷411 N。[结果]固定当时股骨应力集中在股骨粗隆内侧2号螺钉与骨折交界处,应力最大为71.82 MPa,远小于螺钉的屈服强度。骨折愈合过程中最大应力出现在5号螺钉内侧,未出现明显应力集中现象。[结论]单臂外固定架治疗股骨粗隆间骨折安全、有效,其治疗骨折顺乎自然,合乎生理,符合生物力学。     

基于有限元分析方法的Vancouver B1型假体周围骨折内固定方式的比较

[目的]用有限元方法研究人工髋关节置换术后Vancouver B1型股骨假体周围骨折不同内固定方式的稳定性及生物力学情况。[方法]模拟人工髋关节置换术后Vancouver B1型股骨假体周围骨折,并模拟不同方式的锁定钛板螺钉内固定术,模拟部分负重及完全负重情况对装配体施加载荷,并进行组间比较。[结果]随着钛板及螺钉数量增加,骨折端位移减小,内固定稳定性增加,钛板上分布的Von Mises应力峰值逐渐减小,单八孔钛板、单十孔钛板及双八孔钛板固定组间比较差异有统计学意义,但双十孔钛板与双八孔钛板固定组间比较差异无统计学意义;同时,假体上分布的Von Mises应力峰值逐渐增大,但各组间比较均差异无统计学意义。[结论]对于Vancouver B1型股骨假体周围骨折,若采用锁定钛板螺钉内固定方式进行治疗,双重钛板可比单一钛板提供更高的稳定性,同时使得钛板上分布的应力峰值减低,但过长的双重钛板(双十孔)并无必要。     

Pauwels Ⅲ型股骨颈骨折骨缺损不同内固定方案的生物力学分析

目的：探究不同内固定治疗PauwelsⅢ型股骨颈骨折骨缺损的生物力学特征,为骨折治疗提供参考。方法：基于CT图像建立PauwelsⅢ型股骨颈骨折模型,包括单纯骨折和骨折骨缺损两种特征,模拟4种内固定,即倒置空心螺钉（inverted cannulated screw,ICS）、ICS+内侧板、股骨颈系统（femoral neck system,FNS）和FNS+内侧板。测量并比较不同骨折模型在2 100 N轴向载荷下的应力分布、模型刚度和位移情况。结果：ICS和FNS固定时,峰值应力集中于螺钉与骨折端接触位置,FNS的峰值应力高于ICS;与内侧板联用后,峰值应力转移至内侧板,且应力增大,ICS的增加幅度大于FNS。在骨折类型相同的情况下,FNS固定的刚度高于ICS。与骨缺损模型相比,骨折模型在相同内固定时刚度更高。内侧支撑板的使用可增加模型的刚度,但ICS模型的增加幅度超过FNS模型。ICS固定模型的骨折端位移超过FNS模型。结论：对于PauwelsⅢ型股骨颈骨折骨缺损模型,FNS较ICS具有更好的生物力学性能。ICS+内侧板有助于增强治疗的稳定性,但建议采用非锁定板;FNS具有抗剪切...     

低弹性模量接骨板固定股骨干骨折的有限元分析

目的 探讨不同弹性模量接骨板内固定对股骨干骨折应力及其分布的影响. 方法采用64排螺旋CT对一名健康成年男性股骨进行层厚为0.5 mm的扫描,获得股骨CT数据,再通过软件三维反求得到股骨有限元模型.模拟股骨中段骨折模型,分别采用Ti-6Al-4V(高弹性模量组,弹性模量为110 GPa)和Ti2448(低弹性模量组,弹性模量为30 GPa)两种材料的8孔接骨板进行固定.分析两种不同弹性模量接骨板内固定在轴向压缩、四点前后弯曲和扭转载荷下股骨的应力分布情况,并以应力云图的方式直观地显示应力分布规律. 结果在3种载荷下,两组均在断端接触部位出现最大应力.在轴向压缩载荷下,低弹性模量组最大应力值为30.00 MPa,大于高弹性模量组(21.68 MPa);螺孔内最大应力值(11.47 MPa)小于高弹性模量组(13.89 MPa),应力云图显示:高弹性模量组骨组织呈多个应力梯度分布,而低弹性模量组骨组织应力分布较均匀.在四点前后弯曲载荷下,低弹性模量组最大应力值为11.23 MPa,大于高弹性模量组(7.96 MPa).在扭转载荷下,两组股骨应力分布均较均匀,低弹性模量组最大应力值(63.82 MPa)大于高弹性模量组(43.97 MPa),螺孔内最大应力值(11.47MPa)小于高弹性模量组(31.24 MPa). 结论低弹性模量接骨板内固定股骨干骨折,其骨折断端应力刺激增大,螺孔内应力集中减轻,接骨板的应力遮挡效应减小.     

单侧与双侧钢板内固定治疗AO-A3型股骨远端骨折的试验研究

目的对单侧、双侧钢板内固定治疗干骺端粉碎性股骨远端骨折生物力学稳定性进行比较。方法笔者于2016-04—2016-06选取8个配对的经防腐处理的成人股骨标本,建立AO-A3型骨折模型,随机分为2组,单侧钢板组用外侧解剖锁定接骨板固定,双侧钢板组外侧用解剖锁定接骨板、内侧用直型接骨板固定。应用电子万能试验机对单侧与双侧钢板组进行生物力学检测,比较2组垂直加压、循环垂直加压及极限载荷下的稳定性。结果单侧钢板组在垂直加压、循环垂直加压及极限载荷测试中均劣于双侧钢板组,差异有统计学意义(P0.05)。2组未出现钢板或螺钉断裂,载荷-位移曲线斜率未发生较大变化。载荷去除后,2组均恢复原来的状态,具有较好的即刻稳定性。结论单侧或双侧钢板固定干骺端粉碎性股骨远端骨折均能达到有效的力学稳定性,一般无需双侧钢板固定来增加固定强度,单侧钢板固定弹性更佳,可能有利于骨折端的微动及骨折愈合。     

加长型PFNA内固定治疗股骨反粗隆间骨折的三维有限元研究

目的采用三维有限元方法分析加长型股骨近端防旋髓内钉(PFNA)内固定股骨反粗隆间骨折的生物力学特点,为股骨反粗隆间骨折的临床治疗提供理论依据。方法选取1名健康男性志愿者,进行股骨全长螺旋CT扫描,获取DICOM格式数据,用Mimics软件建立正常股骨模型,Creo Parametric软件建立加长型PFNA模型,再使用Geomagic Studio及3-matic软件生成加长型PFNA内固定股骨反粗隆间骨折有限元模型,最后利用ANSYS软件模拟计算各模型的应力及位移分布,进而分析加长型PFNA内固定股骨反粗隆间骨折的生物力学特点。结果加长型PFNA内固定股骨反粗隆间骨折模型应力分布与正常股骨模型接近,股骨两端应力相对较大,中段应力较小,骨折线两端应力分布均匀,以内侧骨皮质处应力最高。加长型PFNA模型应力主要集中于螺旋刀片、主钉近端及二者交界处,且主钉以远应力主要集中于内侧区域。加长型PFNA模型主钉位移在中段处最大,并向两侧递减,螺旋刀片以头部位移最大。结论加长型PFNA内固定股骨反粗隆间骨折的力学特点与正常股骨应力分布一致,内固定物可有效传导应力,符合股骨生物力学特点。     

MIPPO技术下胫骨近端骨折LCP固定的三维有限元研究

目的 比较胫骨近端内侧LCP接骨板通过锁定孔和加压孔固定在不同载荷下的应力分布特点,探讨锁定固定和加压固定的优缺点.方法 建立胫骨近端骨折LCP接骨板锁定固定和加压固定的三维有限元模型,采用有限元分析法,分析模型在轴向加压、三点侧弯、扭转状态下的应力分布.结果 ①LCP接骨板在锁定固定和加压固定下,都在骨折处和骨折近端第一个锁定(加压)孔处有应力集中现象;②LCP接骨板锁定固定应力均值大于加压固定.结论 锁定固定和加压固定都使钢板在骨折处和接骨板第一个锁定(加压)孔处容易发生断裂,加压固定比锁定固定更稳固,但锁定固定更符合BO理论要求.     

Early experience with the gamma interlocking nail for peritrochanteric fractures of the proximal femur.

Surgical fixation, early weight-bearing, and bony union remain a challenge in the treatment of peritrochanteric femur fractures, especially if the fractures are comminuted or unstable. Preliminary experience with the Gamma locking nail, a short intramedullary nail connected to a sliding compression screw augmented with distal locking screws, is presented. In a consecutive series of 29 patients, all fractures were adequately reduced and immediate weight-bearing was begun regardless of fracture configuration (13/27 fractures classified as unstable). Twenty-seven patients were reviewed at 6 months. At follow-up, all patients continued to be ambulatory and all fractures healed. Major complications included screw migration in the femoral head (two patients), difficulty in securely placing the distal screws (eight patients), and a femoral shaft fracture through the distal locking screws following a fall. The technical problems inherent in the device and its instrumentation are discussed. In this early experience, the Gamma nail appears to allow for early patient ambulation regardless of the fracture configuration with excellent clinical results.     

股骨远端锁定接骨板结合中空螺钉治疗股骨远端粉碎性骨折

目的总结股骨远端锁定接骨板结合中空螺钉内固定治疗股骨远端粉碎性骨折的临床疗效。方法采用小切口复位和MIPPO技术、股骨远端锁定接骨板结合中空螺钉治疗36例股骨远端粉碎性骨折患者。结果 36例均获随访,时间6~23(13.5±2.7)个月,骨折均骨性愈合。按照Kolmert et al股骨远端骨折功能评估系统评价:优25例,良8例,中3例,优良率为91.67%。结论正确应用小切口复位和MIPPO技术,股骨远端锁定接骨板结合中空螺钉治疗股骨远端粉碎性骨折能够获得满意的临床疗效。     

Biomechanical testing of the LCP--how can stability in locked internal fixators be controlled?

New plating techniques, such as non-contact plates, have been introduced in acknowledgment of the importance of biological factors in internal fixation. Knowledge of the fixation stability provided by these new plates is very limited and clarification is still necessary to determine how the mechanical stability, e.g. fracture motion, and the risk of implant failure can best be controlled. The results of a study based on in vitro experiments with composite bone cylinders and finite element analysis using the Locking Compression Plate (LCP) for diaphyseal fractures are presented and recommendations for clinical practice are given. Several factors were shown to influence stability both in compression and torsion. Axial stiffness and torsional rigidity was mainly influenced by the working length, e.g. the distance of the first screw to the fracture site. By omitting one screw hole on either side of the fracture, the construct became almost twice as flexible in both compression and torsion. The number of screws also significantly affected the stability, however, more than three screws per fragment did little to increase axial stiffness; nor did four screws increase torsional rigidity. The position of the third screw in the fragment significantly affected axial stiffness, but not torsional rigidity. The closer an additional screw is positioned towards the fracture gap, the stiffer the construct becomes under compression. The rigidity under torsional load was determined by the number of screws only. Another factor affecting construct stability was the distance of the plate to the bone. Increasing this distance resulted in decreased construct stability. Finally, a shorter plate with an equal number of screws caused a reduction in axial stiffness but not in torsional rigidity. Static compression tests showed that increasing the working length, e.g. omitting the screws immediately adjacent to the fracture on both sides, significantly diminished the load causing plastic deformation of the plate. If bone contact was not present at the fracture site due to comminution, a greater working length also led to earlier failure in dynamic loading tests. For simple fractures with a small fracture gap and bone contact under dynamic load, the number of cycles until failure was greater than one million for all tested constructs. Plate failures invariably occurred through the DCP hole where the highest von Mises stresses were found in the finite element analysis (FEA). This stress was reduced in constructions with bone contact by increasing the bridging length. On the other hand, additional screws increased the implant stress since higher loads were needed to achieve bone contact. Based on the present results, the following clinical recommendations can be made for the locked internal fixator in bridging technique as part of a minimally invasive percutaneous osteosynthesis (MIPO): for fractures of the lower extremity, two or three screws on either side of the fracture should be sufficient. For fractures of the humerus or forearm, three to four screws on either side should be used as rotational forces predominate in these bones. In simple fractures with a small interfragmentary gap, one or two holes should be omitted on each side of the fracture to initiate spontaneous fracture healing, including the generation of callus formations. In fractures with a large fracture gap such as comminuted fractures, we advise placement of the innermost screws as close as practicable to the fracture. Furthermore, the distance between the plate and the bone ought to be kept small and long plates should be used to provide sufficient axial stiffness.     

Immediate weight-bearing after treatment of a comminuted fracture of the femoral shaft with a statically locked intramedullary nail

BACKGROUND: The purpose of this two-part investigation was to test the feasibility, safety, and efficacy of immediate weight-bearing after treatment of fractures of the shaft of the femur with a statically locked intramedullary nail. METHODS: In the first part of the investigation, a biomechanical study was performed to determine the fatigue strength of eleven different statically locked intramedullary nail constructs. Segmentally comminuted midisthmal fractures were simulated with use of sections of polyvinyl chloride pipe; each construct was cyclically loaded in compression with use of physiologically relevant loads in a materials testing machine at eight hertz. The fatigue tests were conducted according to the so-called staircase method, and the construct was considered to have run out (exceeded its anticipated service life) if it had not failed after 500,000 cycles. In the second part of the study, a clinical investigation of immediate weight-bearing after treatment of comminuted fractures of the femoral shaft with a Russell-Taylor (RT-2) construct was performed. Complete follow-up data were available for twenty-eight of the thirty-five patients (thirty-six fractures) entered into the study. RESULTS: In Part I of the study, two constructs, a statically locked twelve-millimeter-diameter Russell-Taylor femoral nail with two distal locking screws (RT-2) and a statically locked twelve-millimeter-diameter Zimmer femoral nail with two distal locking screws (Z-2), had significantly higher mean fatigue strengths (2171 and 2113 newtons, respectively) than all other constructs tested (p<0.001), but the strengths of these two constructs were not significantly different from each other. Constructs with only one distal locking screw demonstrated significantly lower (p<0.05) fatigue strengths than the two-screw constructs. These results suggest that full weight-bearing during the weeks immediately after insertion of the nail may be possible, even for patients who have a comminuted fracture of the femoral shaft. In Part II of the study, twenty-six of the twenty-eight patients were bearing full weight on the fractured limb or limbs at the six-week follow-up visit. All fractures united; only one of these needed an additional procedure (the removal of the screws five months after the insertion of the nail) to stimulate union. No loss of fixation, such as back-out or breakage of a locking screw or breakage or bending of the intramedullary nail, occurred. CONCLUSIONS: We concluded from this two-part investigation that immediate weight-bearing after stabilization of a comminuted fracture of the femoral shaft with a statically locked intramedullary nail is safe when the construct has a relatively high fatigue strength. Immediate weight-bearing after stabilization of a fracture of the femoral shaft permits patients who have multiple fractures of the extremity to walk and to participate in physical therapy earlier, possibly decreasing the duration of the hospital stay or reducing the need for prolonged rehabilitation on an inpatient basis.     

Stress fractures in the gapped area of a two implant construct: a case report

The concomitant occurrence of femoral shaft and hip fractures are not rare. The ideal management of ipsilateral intertrochanteric and femoral shaft fractures is still controversial and needs to be addressed. Cephalomedullary nail fixations of both the fractures have been described with excellent results. Similar results have been published with two implant constructs treating both of these injuries separately. We report the case of a stress fracture, in the gapped area above the proximal interlocking screw of a retrograde femoral nail placed for a segmental femur fracture and a trochanteric fracture treated with a sliding hip plate screw construct, 9?months after initial injury. The gapped area of a two implant construct is of concern and biomechanical studies have shown that the proximal end of the nail and the interlocking screws may act as a stress riser in the femur. A stress fracture in the gapped area of a two implant construct has not been described earlier, although a cadaveric study had shown that the area of the proximal screw hole of the retrograde nail is a common site for a fracture, on loading. Kissing or overlapping instrumentation increases the load to failure and creates a biomechanically stable construct.     

PFLCP与PFNA治疗股骨粗隆间骨折的临床疗效比较

目的回顾总结应用股骨近端锁定加压接骨板(proximal femur locking compression plate,PFLCP)与股骨近端螺旋刀片抗旋髓内钉(proximal femoral nail antirotation blade,PFNA)两种手术内固定治疗股骨粗隆间骨折的临床疗效并进行对比分析。方法从2008年7月至2011年10月,收治股骨粗隆间骨折56例,随机分为两组,一组采用PFLCP内固定,另一组采用PFNA内固定。术后分析手术时间、伤口大小、失血量、完全负重时间、骨折愈合时间及内固定位置情况,并通过Harris功能评分评价下肢功能。结果两组顺利完成手术,术后均定期完成随访,平均随访12个月(8～18个月)。PFNA组在切口长度、术后负重时间均优于PFLCP组(P<0.05),两组在手术时间、术中失血量、骨折愈合时间方面比较差异无统计学意义(P>0.05)。PFLCP组出现2例髋内翻、螺钉松动退出、股骨大粗隆滑囊炎,PFNA组2例分别出现颈干角丢失、螺钉切出股骨头和下肢轻度短缩、螺钉稍退出。结论 PFNA和PFLCP两种内固定在股骨粗隆间骨折治疗中均具有较好疗效,PFNA固定允许患者早期负重,两种内固定均具有自己的优势。