桡骨远端骨折锁定钢板的拓扑优化及有限元分析

[目的]对桡骨远端骨折锁定钢板进行刚度最大化设计,运用有限元方法对重设计的钢板进行生物力学评价。[方法]运用三维建模软件和有限元分析软件完成个体化钢板的原型设计并进行初始分析,基于计算结果进一步对优化原型进行拓扑优化设计;通过有限元分析计算和对比常规钢板、优化原型钢板和优化钢板的体积、不同工况下的内固定刚度以及应力分布情况。[结果]所获得的优化钢板在体积上与常规锁定钢板相当,在轴向压缩刚度和扭转刚度方面均优于常规钢板,而在两种工况条件下优化钢板的应力峰值均低于常规钢板,应力分布更为均匀。[结论]对于桡骨远端骨折的个体化治疗,锁定钢板的拓扑优化能够为骨折的内固定提供可靠的方案。     

桡骨远端骨折掌、背侧钢板固定的生物力学研究

目的运用生物力学实验应力分析方法评价桡骨远端背侧移位型骨折,掌侧钢板和背侧钢板固定的生物力学性能比较,从而为桡骨远端骨折的治疗提供临床基础理论依据。方法选用10具桡骨远端标本,制作成背侧移位不稳定型桡骨远端骨折,并分为每对2块,随机采用掌侧钢板和背侧钢板固定,将固定好的标本进行生物力学试验。结果 a)桡骨远端背侧移位型骨折,掌侧钢板固定与背侧钢板固定的应力强度、轴向刚度和剪切刚度差异无统计学意义(P0.05);b)采用两种不同钢板固定,其扭转力学性能,扭矩和扭转刚度差异无统计学意义(P0.05);c)将固定好的两种标本进行轴向破坏力学测试,极限强度及骨吸收能量差异无统计学意义(P0.05);d)实验结果与组合杆应力理论分析相比较仅相差6%,佐证了实验应力分析的正确性。结论桡骨远端背侧移位型骨折,掌侧钢板和背侧钢板固定的生物力学性能两者相当,背侧钢板固定略占优势,但差异无统计学意义。从临床手术角度考虑一般采用掌侧钢板固定,简单、方便、实用、疗效较好,是行之有效的术式。     

四种外固定治疗不稳定性桡骨远端骨折的生物力学研究

目的　比较四种治疗桡骨远端不稳定性骨折外固定方法 ,为临床选用提供依据。方法　采用 8具尸体前臂—手部标本制成骨折损伤模型 ,随机分别先后采用桡骨远端动力型外固定器、小型AO外固定器、小型于氏多功能外固定器和石膏固定 ,进行抗轴向压缩、抗弯曲、抗扭转的强度与刚度的比较。结果　各组应变值与载荷的大小呈正线性相关 ;在满足轴向压缩、弯曲及扭转的强度、刚度和稳定性方面 ,桡骨远端动力型外固定器比小型AO外固定器和于氏多功能外固定器优越 ,石膏固定最差 ,四者具有显著性差异 (P <0 0 1)。结论　外固定器是治疗桡骨远端不稳定性骨折的一种有效方法 ,动力型外固定器具有独特优势     

四种外固定治疗不稳定性桡骨远端骨折的生物力学研究

目的：比较四种治疗桡骨远端不稳定性骨折外固定方法,为临床选用提供依据。方法：采用8具尸体前臂一手部标本制成骨折损伤模型,随机分别先后采用桡骨远端动力型外固定器、小型AO外固定器、小型于氏多功能外固定器和石膏固定,进行抗轴向压缩、抗弯曲、抗扭转的强度与刚度的比较。结果：各组应变值与载荷的大小呈正线性相关;在满足轴向压缩、弯曲及扭转的强度、刚度和稳定性方面,桡骨远端动力型外固定器比小型AO外固定器和于氏多功能外固定器优越,石膏固定最差,四者 具有显著性差异（P＜0.01)。结论：外固定器是治疗桡骨远端不稳定性骨折的一种有效方法,动力型外固定器具有独特优势。     

桡骨头骨折两种内固定方式的生物力学研究

[目的]探讨桡骨头骨折两种内固定的生物力学特性。寻找最佳内固定方法,为临床运用提供基础理论依据。[方法]20具人工桡骨制作桡骨头颈骨折模型,10具采用普通微型钢板固定(普通板组),另外10具采用解剖型钢板固定(解剖板组),分别进行轴向压缩应力强度和刚度、弯曲强度和挠度及扭转力学性能的生物力测试。比较两种内固定方式的优劣性。[结果]普通板组的轴向压缩强度显著低于解剖板组,差异有统计学意义(P0.05)。普通板组的刚度显著低于解剖板组,两者刚度相差17%,差异有统计学意义(P0.05)。普通板组与解剖板组的三点弯曲强度相差17%,差异有统计意义(P0.05)。在相同载荷下,普通板组的挠度明显高于解剖板组,两者相差15%,差异有统计学意义(P0.05)。普通板和解剖板两种不同型式钢板固定后,桡骨头的扭转强度和刚度恢复达90%以上。两组相比较,解剖板组的扭转强度高于普通板组,达18%,扭转刚度达13%,差异有统计学意义(P0.05)。[结论]桡骨头骨折采用解剖型钢板固定较采用普通钢板具有生物力学优势,是一种比较理想的内固定方式。     

三种方法治疗尺桡骨中段双骨折的生物力学比较与分析

[目的]从生物力学角度探讨尺桡骨中段双骨折不同内固定方法的力学稳定性差异,为临床应用提供理论依据。[方法]采用15具新鲜尺桡骨标本,制成中段横形骨折模型(AO分型A3.2),分成3组,然后采用三种不同的方法进行固定(尺桡骨双钢板固定,尺桡骨双髓内钉固定,尺骨髓内钉加桡骨动力加压钢板固定)。之后,进行生物力学试验,比较轴向刚度、弯曲刚度、扭转刚度和等效刚度。[结果]双钢板组与尺骨髓内钉+桡骨钢板组之间无明显差异,两者的稳定性均高于双髓内钉组。[结论]尺骨髓内钉加桡骨钢板组具有良好的生物力学性能,固定可靠,并且具有创伤小、并发症少的优点,是一种良好的固定方法。     

胫骨远端解剖钢板治疗不稳定性Pilon骨折的生物力学研究

目的：从生物力学角度探讨新型胫骨远端解剖铜板的力学性能。方法：将12具新鲜湿润成人踝关节标本,随机区组分为4组（每组3具）,3具正常胫骨作为对照（正常N组）,9具造成胫骨远端不稳定性Pilon骨折,分别采用新型胫骨远端解剖钢板固定（A组）、重建铜板固定（B组）、三叶草钢板固定（C组）,B、C两组为对照组,测试各组的远端轴向抗压强度、远端轴向刚度、扭转生物力学性能、胫距关节面接触特征。结果：A组在胫骨远端不稳定性Pilon骨折的远端轴向抗压强度、远端轴向刚度、扭转生物力学性能以及胫距关节面接触特征上接近正常N组（P〉0．05）,优于B、C组（P〈0．05）。结论：新型胫骨远端解剖钢板固定后比较牢固,能达到胫骨远端不稳定性Pilon骨折稳定、可靠的固定目的。     

胫骨远端前外侧解剖型锁定钢板治疗不稳定性Pilon骨折的生物力学研究

目的探讨胫骨远端前外侧解剖型锁定钢板治疗不稳定性Pilon骨折的生物力学性能。方法将7具新鲜湿润的成人踝关节标本随机分为四组,1具标本作为正常对照组(N组);其余6具均造成胫骨远端不稳定性Pilon骨折,分成3组,每组2具标本,分别采用胫骨远端前外侧解剖型锁定钢板(A组)、三叶草钢板(B组)、重建钢板固定(C组),后两组为对照组,测试各组的远端轴向强度、刚度,扭转生物力学性能,胫距关节面接触特征。结果 A组在胫骨远端不稳定性Pilon骨折的远端轴向强度、刚度,扭转生物力学性能以及胫距关节面接触特征上接近N组(P0.05),优于B、C组(P0.05)。结论胫骨远端前外侧解剖型锁定钢板治疗不稳定性Pilon骨折不但具有优越的生物力学性能,而且操作简便、安全可靠,Pilon骨折固定的关节稳定性明显比其他内固定材料占有较大的优势,是较为理想的选择。     

不同固定方法治疗不稳定性桡骨远端关节内骨折的离体生物力学评估

目的比较5种不同固定方法对不稳定性桡骨远端关节内骨折的作用。方法采用标准的截骨法制备不稳定性桡骨远端关节内骨折的尸体模型,然后测量外固定伴或不伴克氏针固定、背侧钢板内固定、掌侧钢板内固定及双侧支撑钢板固定5种方法对恢复桡骨稳定性及轴向力传导的作用,并与正常对照组进行比较。结果外固定伴克氏针固定和掌侧钢板内固定是其中最稳定的方法,其次是背侧钢板内固定及单纯外固定,双侧支撑钢板固定则最不稳定。结论本研究的结果对临床治疗方案的选择提供有意义的参考。     

锁定加压钢板治疗桡骨远端骨折

目的评估锁定加压钢板治疗桡骨远端不稳定性骨折的临床疗效。方法手术治疗26例不同类型桡骨远端不稳定性骨折患者,采用锁定加压钢板进行内固定。结果26例均获随访,时间6～15个月,骨折均在6～12周愈合。桡骨轴向无短缩,钢板螺钉位置良好,无固定钉板松动、断钉及骨折再移位现象发生。按照改良McBride评分和纽约骨科医院腕关节评估标准：优14例,良9例,可3例。结论锁定加压钢板治疗桡骨远端骨折临床疗效满意,尤其对不稳定以及骨质疏松性桡骨远端骨折者,能够牢固维持复位,有利于患肢早期功能锻炼。     

Internal fixation of dorsally displaced fractures of the distal part of the radius. A biomechanical analysis of volar plate fracture stability

BACKGROUND: Volar plate fixation with use of either a locking plate or a neutralization plate has become increasingly popular among surgeons for the treatment of dorsally comminuted extra-articular distal radial fractures. The purpose of the present study was to compare the relative stability of five distal radial plates (four volar and one dorsal), all of which are commonly used for the treatment of dorsally comminuted extra-articular distal radial fractures, under loading conditions simulating the physiologic forces that are experienced during early active rehabilitation. METHODS: With use of a previously validated Sawbones fracture model, a dorsally comminuted extra-articular distal radial fracture was created. The fracture fixation stability of four volar plates (an AO T-plate, an AO 3.5-mm small-fragment plate, an AO 3.5-mm small-fragment locking plate, and the Hand Innovations DVR locking plate) were compared under axial compression loading and dorsal and volar bending simulating the in vivo stresses that are generated at the fracture site during early unopposed active motion of the wrist and digits. A single dorsal plate (an AO pi plate) was used for comparison, with and without simulated volar cortical comminution. The construct stiffness was measured to assess the resistance to fracture gap motion, and comparisons were made among the implants. RESULTS: The volar AO locking and DVR plates had greater resistance to fracture gap motion (greater stiffness) compared with the volar AO nonlocking and AO T-plates under axial and dorsal loading conditions (p < 0.01), with no significant difference between the AO volar locking and DVR plates. The volar AO locking plate had greater resistance to fracture gap motion than did the volar AO nonlocking plate under axial loading and dorsal bending forces (p < 0.01). The dorsal pi plate had the greatest resistance to fracture gap motion under axial loading and volar and dorsal bending forces (p < 0.01). However, the pi plate was significantly less stable to axial load and dorsal bending forces when the volar cortex was comminuted (p < 0.01). CONCLUSIONS: In this model of dorsally comminuted extra-articular distal radial fractures, dorsal pi-plate fixation demonstrated better resistance to fracture gap motion than did the four types of volar plate fixation. The AO volar locking and DVR plates conferred the greatest resistance to fracture gap motion among the four volar plates tested. Volar locking technology conferred a significant increase in resistance to fracture gap motion as compared with nonlocking plate technology.     

Calcar screw position in proximal humerus fracture fixation: Don’t miss high!

IntroductionIn locked plate fixation of proximal humerus fractures, the calcar is an important anchor point for screws providing much-needed medial column support. Most locking plate implants utilize a fixed-trajectory locking screw to achieve this goal. Consequently, adjustments of plate location to account for patient-specific anatomy may result in a screw position outside of the calcar. To date, little is known about the consequences of “missing” the calcar during plate positioning. This study sought to characterize the biomechanics associated with proximal and distal placement of locking plates in a two-part fracture model.Materials and methodsThis experiment was performed twice, first with elderly cadaveric specimens and again with osteoporotic sawbones. Two-part fractures were simulated and specimens were divided to represent proximal, neutral, and distal plate placements. Non-destructive torsional and axial compression tests were performed prior to an axial fatigue test and a ramp to failure. Torsional stiffness, axial stiffness, humeral head displacement and stiffness during fatigue testing, and ultimate load were compared between groups.ResultsCadavers: Proximal implant placement led to trends of decreased mechanical properties, but there were no significant differences found between groups. Sawbones: Distal placement increased torsional stiffness in both directions (p = 0.003, p = 0.034) and axial stiffness (p = 0.018) when compared to proximal placement. Distal placement also increased torsional stiffness in external rotation (p = 0.020), increased axial stiffness (p = 0.024), decreased humeral head displacement during fatigue testing, and increased stiffness during fatigue testing when compared to neutral placement.DiscussionThe distal and neutral groups had similar mechanical properties in many cadaveric comparisons while the proximal group trended towards decreased construct stiffness.Resultsfrom the Sawbones model were more definitive and provided further evidence that proximal calcar screw placements are undesirable and distal implant placement may provide improved construct stability.ConclusionSuccessful proximal humerus fracture reconstruction is inherent upon anatomic fracture reduction coupled with medial column support. Results from this experiment suggest that missing the calcar proximally is deleterious to fixation strength, while it is safe, and perhaps even desirable, to aim slightly distal to the intended target.     

Analysis of the mechanical properties of locking plates with and without screw hole inserts

The purpose of this study was to determine if the use of screw hole inserts in empty locking screw holes improves the strength and failure characteristics of locking plates. Twenty 5-hole 1/3 tubular locking plates (Synthes, Paoli, Pennsylvania) were mounted on an oak dowel with a 1-cm gap simulating a fracture with comminution and bone loss. Ten of the 1/3 tubular plates had a screw hole insert placed in the center hole (centered over the simulated fracture), while 10 of the 1/3 tubular plates remained empty in the center hole. The plate-dowel constructs were placed in an Instron 8800 Material Testing Machine and subjected to a series of loading conditions, replicating physiologic loading. The torsional and axial stiffness of each plate-dowel construct was calculated. All plates were then loaded to failure. No significant differences were found in the mechanical properties of the 2 plate constructs. Both the filled screw-hole plate constructs and unfilled screw hole plate constructs demonstrated the same torsional and axial stiffness, before and after being subjected to a combined cyclic and axial torsional load. Additionally, there was no significant difference in ultimate compressive strength or load to failure. Locking plate technology is a relatively new innovation in orthopedic fracture fixation. The evolution of new and varied applications and implants continues. Persistent, fundamental questions exist concerning the basic locking plate design. This study demonstrates that the addition of screw hole inserts does not significantly change the stiffness, torsional strength, or axial loading strength of 1/3 tubular locking plates.     

Nailing versus plating for comminuted fractures of the distal femur: a comparative biomechanical in vitro study of three implants

Purpose

The purpose of our study was to determine the biomechanical properties of three different implants utilized for internal fixation of a supracondylar femur fracture. The retrograde supracondylar nail (SCN), the less invasive stabilization system plate (LISS) and the distal femoral nail (DFN) were tested and their biomechanical properties compared.

Methods

Twenty pairs of fresh-frozen human femura were used. Each femur was osteotomised to simulate a comminuted supracondylar fracture (AO/OTA 33.A3) and then randomized to fracture fixation with either SCN (n=9) or LISS (n=9). Each contralateral femur was stabilized with DFN as a control (n=18). Two femur pairs were spent on pretesting. All femura were subjected to axial (10–500 N) and torsional (0.1–14 Nm) loading.

Results

Eighteen matched femur pairs were analyzed. The post-loading median residual values were 49.78, 41.25 and 33.51% of the axial stiffness of the intact femur and 59.04, 62.37 and 46.72% of the torsional stiffness of the intact femur in the SCN, LISS and DFN groups. There were no significant differences between the three implants concerning axial and torsional stiffness.

Conclusions

All implants had sufficient biomechanical stability under physiological torsional and axial loading. All three implants have different mechanisms for distal locking. The SCN nail with the four-screw distal interlocking had the best combined axial and torsional stiffness whereas the LISS plate had the highest torsional stiffness.     

Biomechanical analysis of distal femoral fracture fixation: dynamic condylar screw versus locked compression plate

Background This human cadaveric study introduces a laboratory model to establish and compare the fixation stability of the distal femoral locking plate (DFLP) and dynamic condylar screw (DCS) in distal femoral fracture fixation.Materials and methods The study was conducted on 16 fresh cadaveric femoral specimens, 8 implanted with the DCS and the other 8 with the DFLP. The construct was made unstable by removing a standard-sized medial wedge with a 1-cm base (gap osteotomy) beginning 6 cm proximal to the lateral joint line in the distal metaphyseal region with loss of the medial buttress. Each specimen underwent axial and torsional stiffness testing along with cyclic axial loading to failure. The mean DEXA value for the DFLP group was 0.82 g/cm² and in the DCS group was 0.79 g/cm².Results Axial stiffness in the DFLP group was significantly higher than in the DCS group, but no significant difference was found in torsional stiffness between the groups. A significant difference was found in the load-to-failure results between the groups. Plastic and total deformation was significantly higher in constructs in the DCS group than in those in the DFLP group. Total energy absorbed before construct failure was also significantly higher in the DFLP group than in the DCS group.Conclusions The DFLP construct proved stronger than the DCS in both axial stiffness and cyclic loading, but similar in torsional stiffness in biomechanical testing in a simulated A3 distal femoral fracture.     

Fixation of osteoporotic distal fibula fractures: A biomechanical comparison of locking versus conventional plates.

The increased use of locking plates to treat difficult fracture scenarios has been advocated in patients that have reduced bone mineral density. One of these difficult fracture patterns, fixation of the distal fragment of a distal fibula fracture, may depend on unicortical and cancellous bony purchase. This study investigated the construct stiffness afforded by using locking and conventional plating schema in a cadaveric model. Overall, the data indicate that a locking plate construct with two distal unicortical screws was mechanically equivalent to standard plating with 3 distal screws. In addition, fixation with the standard plates was dependent on bone mineral density (BMD) whereas the locking plate fixation was independent of BMD. The clinical implication of this study is that locking plates may be advantageous in patients with the most severe osteoporosis.     

桡掌侧入路锁定钢板治疗桡骨远端粉碎性骨折

目的观察锁定钢板对桡骨远端粉碎性骨折的\治疗效果。方法采用桡掌侧入路锁定钢板治疗33例桡骨远端粉碎性骨折患者。结果 33例均获随访,时间24~72周。骨折均愈合,愈合时间12~24周。无腕关节僵硬以及骨折再移位。根据Dienst功能评定标准评定疗效:优24例,良7例,可2例,优良率93.94%。结论桡掌侧入路锁定钢板治疗桡骨远端粉碎性骨折疗效可靠,腕关节功能恢复满意。     

The effect of plate rotation on the stiffness of femoral LISS: a mechanical study

OBJECTIVE: Malposition of the femoral Less Invasive Stabilization System (LISS) plate may alter its biomechanical behavior. This study compares the mechanical stability of "correctly" affixed LISS plates matching the slope of the lateral femoral condyle to "incorrectly" placed LISS plates fixed in external rotation relative to the distal femur. METHODS: A fracture gap model was created to simulate a comminuted supracondylar femur fracture (AO/OTA33-A3). Fixation was achieved using two different plate positions: the LISS plate was either placed "correctly" by internally rotating the plate to match the slope of the lateral femoral condyle, or "incorrectly" by externally rotating the plate relative to the distal femur. Following fixation, the constructs were loaded in axial, torsional, and cyclical axial modes in a material testing machine. MAIN OUTCOME MEASUREMENT: Stiffness in axial and torsional loading; total deformation and irreversible (plastic) deformation in cyclical axial loading. RESULTS: The mean axial stiffness for the correctly placed LISS constructs was 21.5% greater than the externally rotated LISS constructs (62.7 N/mm vs. 49.3 N/mm; P = 0.0007). No significant difference was found in torsional stiffness between the two groups. Cyclical axial loading caused significantly less (P < 0.0001) plastic deformation in the correct group (0.6 mm) compared with externally rotated group (1.3 mm). All the constructs in the incorrect group failed, where failure was defined as a complete closure of the medial fracture gap, prior to completion of the test cycles. CONCLUSION: Correct positioning of the LISS plate for fixation of distal femur fractures results in improved mechanical stability as reflected by an increased stiffness in axial loading and decreased plastic deformation at the bone-screw interface.     

Biomechanics and biology of plate fixation of distal radius fractures

The fracture management principles of anatomic or near anatomic reduction, fracture stabilization, minimal operative trauma, and early joint motion are paramount in man-aging unstable distal radial fractures. The operative approach and plate selection should correlate with the fracture configuration. Plates have the advantages of providing secure fixation throughout the entire healing process without protruding wires or pins and allowing early and intensive forearm, wrist, and digital exercises. Disadvantages include additional operative trauma, including fragment devascularization; some additional risk of wrist stiffness; occasional tendon rupture; and at times, the need for plate removal. New developments in plate and screw design and operative strategies, fragment specific fixation, and plate strength have improved results with plate fixation. Fixed angle blades and locking screws and pegs enhance overall plate stability, support the articular surface of the distal radius, and are effective in fractures occurring in osteopenic bone.     

Palmar plate fixation of AO type C2 fracture of distal radius using a locking compression plate--a biomechanical study in a cadaveric model

The stability of palmar plate fixation using a locking compression T-plate was compared with that of a conventional palmar T-plate and a dorsal T-plate in a cadaveric model of an AO type C2 fracture of distal radius. The wrist axial load transmission through the radius was tested for each fixation. The results show that, under 100N axial load, the palmar locking compression T-plate restores stability comparable to that of the intact radius, and is superior to conventional palmar or dorsal T-plates.