Biomechanical measurements on scaphoid bone screws in an experimental model

A number of screws commonly used for internal fixation in scaphoid bone fractures and nonunions are compared regarding biomechanical properties and clinical applicability. The experiments were carried out on models made of ash-wood, representing a reconstruction and fixation as is performed in a cortico-cancellous inlay bone graft for scaphoid non-union. For fixation use was made of 2.7 and 3.5 AO/ASIF cortical screws respectively, 4.0 AO/ASIF cancellous screws, Herbert screws, and a newly designed screw called the three components screw (D.K.S.). The models with implanted screws were tested for bending strength, tensile strength and torsion stability. No large differences between the various screws were found regarding the measured parameters, so that a small intra-osteal implant such as the Herbert screw and the D.K.S., which can be inserted easily and which gives a certain amount of interfragmentary compression, will be sufficient for osteosynthesis of the scaphoid bone. In case an intra-osteal implant is not available a single 3.5 AO/ASIF cortical screw, inserted following lag-screw principles, is recommended.     

动力加压髋螺钉对股骨上段生物力学特征性的影响

目的：探讨股骨上端骨折,以动力加压髋螺钉进行骨固定治疗,骨折愈合后,取出动力加压髋螺钉以后的股骨上段与完整的股骨上段的生物力学特性相比较,为临床内固定取出术后功能锻炼的强度提供量化依据。方法：收集8具新鲜尸体股骨标本进行实验应力分析,分别测定完整股骨上段和动力加压髋螺钉取出后股骨上段的力学特性改变。结果：动力加压髋螺钉取出术后股骨上段的力学特性与完整股骨上段的力学特性相比有显著的差异（P＜0．01）。结论：股骨上端骨折如果以动力加压髋螺钉为治疗手段,在骨折愈合取出内固定后,功能锻炼只能控制在慢速步行水平,不能进行奔跑、跳跃等活动,以防止再骨折等并发症的发生。     

A new adhesive technique for internal fixation in midfacial surgery

Background  

The current surgical therapy of midfacial fractures involves internal fixation in which bone fragments are fixed in their anatomical positions with osteosynthesis plates and corresponding screws until bone healing is complete. This often causes new fractures to fragile bones while drilling pilot holes or trying to insert screws. The adhesive fixation of osteosynthesis plates using PMMA bone cement could offer a viable alternative for fixing the plates without screws. In order to achieve the adhesive bonding of bone cement to cortical bone in the viscerocranium, an amphiphilic bone bonding agent was created, analogous to the dentin bonding agents currently on the market.     

Biomechanical comparison of locking plate and crossing metallic and absorbable screws fixations for intra-articular calcaneal fractures

The locking plate and percutaneous crossing metallic screws and crossing absorbable screws have been used clinically to treat intra-articular calcaneal fractures, but little is known about the biomechanical differences between them. This study compared the biomechanical stability of calcaneal fractures fixed using a locking plate and crossing screws. Three-dimensional finite-element models of intact and fractured calcanei were developed based on the CT images of a cadaveric sample. Surgeries were simulated on models of Sanders type III calcaneal fractures to produce accurate postoperative models fixed by the three implants. A vertical force was applied to the superior surface of the subtalar joint to simulate the stance phase of a walking gait. This model was validated by an in vitro experiment using the same calcaneal sample. The intact calcaneus showed greater stiffness than the fixation models. Of the three fixations, the locking plate produced the greatest stiffness and the highest von Mises stress peak. The micromotion of the fracture fixated with the locking plate was similar to that of the fracture fixated with the metallic screws but smaller than that fixated with the absorbable screws. Fixation with both plate and crossing screws can be used to treat intra-articular calcaneal fractures. In general, fixation with crossing metallic screws is preferable because it provides sufficient stability with less stress shielding.     

可吸收螺钉结合克氏针治疗跟骨骨折

目的评价可吸收螺钉结合克氏针治疗跟骨骨折的疗效。方法采用可吸收螺钉结合克氏针对17例跟骨骨折行切开复位内固定。按Sanders分型[1]:其中Ⅱ型6例,Ⅲ型10例,IV型1例。结果 17例均获得随访,随访时间6～42个月,平均11.6个月,骨折全部愈合。疗效优6例,良8例,可2例,差1例,优良率82.4%。结论可吸收螺钉结合克氏针用于治疗跟骨骨折,值得推广。     

Biomechanical Comparison of Different Stabilization Constructs for Unstable Posterior Wall Fractures of Acetabulum. A Cadaveric Study

Purpose

Operative treatment of unstable posterior wall fractures of acetabulum has been widely recommended. This laboratory study was undertaken to evaluate static fixation strength of three common fixation constructs: interfragmentary screws alone, in combination with conventional reconstruction plate, or locking reconstruction plate.

Methods

Six formalin-preserved cadaveric pelvises were used for this investigation. A posterior wall fracture was created along an arc of 40–90 degree about the acetabular rim. Three groups of different fixation constructs (two interfragmentary screws alone; two interfragmentary screws and a conventional reconstruction plate; two interfragmentary screws and a locking reconstruction) were compared. Pelvises were axial loaded with six cycles of 1500 N. Dislocation of superior and inferior fracture site was analysed with a multidirectional ultrasonic measuring system. Results: No statistically significant difference was found at each of the superior and inferior fracture sites between the three types of fixation. In each group, the vector dislocation at superior fracture site was significantly larger than inferior one.

Conclusions

All those three described fixation constructs can provide sufficient stability for posterior acetabular fractures and allow early mobilization under experimental conditions. Higher posterior acetabular fracture line, transecting the weight-bearing surface, may indicate a substantial increase in instability, and need more stable pattern of fixation.     

经骨折椎体椎弓根螺钉短节段固定治疗胸腰段骨折疗效

目的:评估和分析经骨折椎体椎弓根螺钉短节段固定治疗胸腰段单椎体粉碎性骨折的临床疗效。方法:选取胸腰段单椎体粉碎性骨折30例患者,分为两组,甲组20例,采用经骨折椎体椎弓根螺钉短节段固定治疗,均行骨折椎体及骨折椎体上下相邻椎体的椎弓根螺钉+双侧连接杆固定;乙组10例,只行骨折椎体的上下相邻椎体的椎弓根螺钉+连接杆固定术。术后随访。测定两组患者手术前后的椎体后凸畸形角和骨折椎体前方高度,评估其临床疗效。结果:术前平均后凸畸形角纠正:甲组15°,乙组11°,P0.05。术后骨折椎体前方的平均高度(和正常椎体前方高度比):甲组89%,乙组81%,P0.05;术后3个月随访:平均后凸畸形角纠正丢失,甲组2°,乙组6°,P0.05;骨折椎体前方的平均高度(和正常椎体前方高度比):甲组87%,乙组73%,P0.05。结论:经骨折椎体椎弓根螺钉短节段固定治疗胸腰段单椎体粉碎性骨折能提供更好的生物力学稳定性,更有利于骨折的复位和后凸畸形的纠正。     

Comparison of compression and torque measurements of self-tapping and pretapped screws

The choice of an internal fixation system for maxillofacial surgery is made difficult because of lack of information with respect to functional load. This study attempted to clarify some of the controversy with respect to maxillofacial use of these implants. Maximal compressive force to torque values were measured in standardized bone thicknesses of 1, 2, 3, and 4 mm. The screws tested were pretapped AO 1.5-, 2.0-, 2.7-, and 3.5-mm rescue screws and self-tapping Luhr, Champy, and AO 1.5- and 2.0-mm screws. Ten measurements were made for each screw type/bone thickness combination using a piezoelectric washer and torque screwdriver. It was apparent that for 1- and 2-mm bone thicknesses the use of self-tapping screws resulted in the highest compression values. In 3- and 4-mm bone thicknesses, pretapped screws offered the highest compression values. As expected, self-tapping screws had the highest torque values on insertion owing to torque loss in cutting the screw threads. The 2.7-mm screw offered no advantage over the 2.0-mm screws in 1- and 2-mm bone thicknesses but resulted in higher compression values in 3- and 4-mm bone thicknesses.     

Effectiveness of pedicle screw inclusion at the fracture level in short-segment fixation constructs for the treatment of thoracolumbar burst fractures: a computational biomechanics analysis

When treating thoracolumbar burst fractures (BF), short-segment posterior fixation (SSPF) represents a less invasive alternative to the traditional long-segment posterior fixation (LSPF) approach. However, hardware failure and loss of sagittal alignment have been reported in patients treated with SSPF. Including pedicle screws at the fracture level in SSPF constructs has been proposed to improve stiffness and reliability of the construct. Accordingly, the biomechanical performance of the proposed construct was compared to LSPF via a computational analysis. Pedicle screws at fracture level improved the performance of the short-segment construct. However, LSPF still represent a biomechanically superior option for treating thoracolumbar BF.     

对侧皮质锁定螺钉与锁定螺钉治疗股骨远端骨折疗效比较

目的:比较对侧皮质锁定螺钉与锁定螺钉治疗股骨远端骨折的临床疗效。方法:回顾性分析自2013年5月至2016年8月诊治的52例股骨远端骨折患者,采用对侧皮质锁定螺钉+NCB接骨板内固定治疗26例(A组:对侧皮质锁定组),采用锁定螺钉+NCB接骨板内固定治疗26例(B组:锁定螺钉组)。记录两组手术出血量和手术时间、切口长度、内固定治疗后骨折愈合时间、内固定治疗后完全负重时间、内固定治疗后并发症发生率等,在每个随访节点对每位患者进行患肢的正侧位X线平片检查,末次随访时对患肢进行膝关节功能评分,采用美国特种外科医院膝关节评分标准评定患肢功能。骨折愈合的定义为活动时骨折处无痛且在骨折正侧位X线平片上可见到断端骨皮质骨痂连接。术后并发症包括:关节僵硬、内固定断裂、骨不连以及感染等。结果:本研究52例骨折均获得至少12个月的随访。两组在手术相关指标及切口愈合等方面均无明显差异(P均0.05)。在骨折愈合以及完全负重时间方面,A组均显著短于B组(P均0.05)。末次随访时52例患者患肢膝关节功能:A组:优18例,良5例,差4例,优良率88.5%;B组:优15例,良6例,中4例,差1例,优良率80.8%。两组对比A组优良率显著高于B组(P0.05)。两组并发症对比无明显差异:A组发生骨不连2例,骨折内固定断裂2例。B组发生骨不连3例,畸形愈合2例。结论:与传统锁定螺钉相比,对侧皮质锁定螺钉在骨折愈合时间、完全负重时间、术后患肢功能优良率方面具有优势,但在并发症发生率方面没有明显差异。对侧皮质锁定螺钉的治疗指征及自身强度还有待大样本、多中心的临床研究进一步明确。     

空心钉配合缝线张力带技术治疗移位的肱骨大结节骨折

目的:探讨使用空心钉配合缝线张力带技术治疗移位的肱骨大结节骨折的效果。方法:2008年3月-2010年3月,收治12例肱骨大结节骨折病人,男10例,女2例,年龄21-71岁,平均年龄46.3岁。其中8例摔伤,2例车祸外伤,2例运动中损伤并伴有盂肱关节脱位。受伤至手术时间5小时-1周。X线显示大结节骨折移位大于5mm。大结节骨折块采用空心钉配合5-Ethibond缝线构成的张力带技术进行固定。结果:患者伤口均一期愈合无感染等并发症发生,所有患者均获随访,随访时间9-33个月,平均14个月。X线显示术后2-4个月骨折愈合,平均2.5个月。美国加州大学洛杉矶分校评分标准评分为(33.65±3.83)分;优9例,良2例,可1例,优良率91.7%。结论:采用切开复位空心钉配合缝线张力带技术治疗肱骨大结节骨折疗效满意,功能恢复良好,疼痛缓解明显。     

8. Self-compressing implants in the management of fractures.

Internal fixation of fractures has become increasingly important since the introduction of self-compressing implants. Rigidity of fixation thus ensured permits primary bone healing. Two types of self-compressing implants are available--screws and plates. The former produces compression between fracture fragments, the latter, along the long axis of the bone. Two common types of plates are the dynamic compression plate and the Osteo self-compressing plate. Use of self-compressing implants requires familiarity with the technique, a definite plan of operation, and strict asepsis and lack of infection in the patient. Indications for the technique include failure or unsuitability of closed reduction of fractures, care of associated serious soft-tissue injuries, and displaced intra-articular fractures. Use of self-compressing plates hastens rehabilitation, lessens joint stiffness and reduces the duration of hospitalization. The incidence of nonunion with self-compression techniques is lower than with traditional methods of fracture management.     

Treatment of mandible fractures using low-profile titanium miniplates: preliminary study.

This study evaluated the short-term results of patients treated with low-profile titanium miniplates for fractures of the mandible. Thirty-one fractures of the mandible in 23 patients were treated by open reduction and internal fixation using thin, low-profile miniplates and 1.3-mm self-threading screws. Duration of intermaxillary fixation ranged from 0 to 25 days. Patients were evaluated for complications during a follow-up period ranging from 6 to 24 months. Seven patients (30.4 percent) experienced complications. These included infection (n = 1), premature occlusal contact (n = 1), wound dehiscence (n = 1), temporomandibular joint disorder (n = 1), and paresthesia (n = 3). All complications were minor and adequately managed with incision and drainage, medication, and elastic traction. Low-profile titanium miniplates can be adequately used for internal fixation in selective mandibular fractures. Advantages of these types of plates include comfort due to the thinness of miniplates and ease of application.     

Biomechanical studies and finite element analysis of a bone-implant interface]

In the present study, the fixation system of a femoral medullary nail connection was investigated. In surgical treatment of fractured femurs, the fracture is bridged by a medullary nail that is fixed by interlocking screws in the bone. Bone failure around these screws is the most common complication associated with the treatment of fractures of osteoporotic bone. The present study analyses the stresses present in the region of the implant/bone system. Three-dimensional finite element models were generated, a nonlinear structure analysis performed, and the stresses at material interfaces investigated. The highest concentration of stresses is to be found in the middle of the interlocking screws and the holes drilled in the bone. This is in agreement with the results of experimental investigations.     

Rigid stabilization of sagittal fractures of the maxilla and palate

Rigid stabilization of sagittal fractures of the palate is described that utilizes plate and screw fixation in the palatal vault. Accurate reduction of facial width is obtained, and stability is significantly enhanced. An existing laceration or a longitudinal incision in the palatal mucoperiosteum provides exposure for maxillary adaption plate application. The transpalatal reduction should be supplemented by fixation at the piriform aperture, the zygomaticomaxillary and nasomaxillary buttresses, and by the use of an arch bar. Since slower bone healing may be observed following palatoalveolar fractures, the occlusion must be observed for deviation throughout a full 16-week period even though early motion and soft diet are permitted. Removal of the plate and screws in the roof of the mouth is sometimes required and utilizes local anesthesia.     

Comparative endurance testing of the Biomet Matthews Nail and the Dynamic Compression Screw,in simulated condylar and supracondylar femoral fractures

Background  

The dynamic compression screw is a plate and screws implant used to treat fractures of the distal femur. The Biomet Matthews Nail is a new retrograde intramedullary nail designed as an alternative surgical option to treat these fractures. The objective of this study was to assess the comparative endurance of both devices.     

Treatment of mandible fractures using bioabsorbable plates

This study evaluated the short-term outcome of treating fractures of the mandible with bioabsorbable plates. Sixty-nine fractures of the mandible in 49 patients were treated by open reduction and internal fixation using bioabsorbable plates and 2.4-mm, 2.0-mm, and 1.5-mm pretapped screws. The duration of intermaxillary fixation ranged from 0 to 23 days, with a mean of 4.6 days. Patients were evaluated for complications during the follow-up period, which ranged from 1 to 18 months. Six patients (12.2 percent) experienced complications. These included infection (four patients), premature occlusal contact (one patient), and temporomandibular disorder (one patient). Except for one case, all complications were minor and adequately managed with incision and drainage, elastic traction, physical therapy, and medication. Delayed infection (osteomyelitis) developed in a symphysis fracture and was treated by saucerization and antibiotics. The fracture line subsequently showed complete consolidation. Bioabsorbable plates can be selectively used for internal fixation in mandibular fractures, with the advantage that they do not need to be removed.     

脊柱椎弓根螺钉生物力学研究进展

椎弓根螺钉内固定术是目前临床上治疗脊柱骨折的常用手术方式。生物力学特别是脊柱生物力学方面的研究是其内固定器设计和研制的基础,也是评价其固定的稳定性及实用价值性的具体标准。因此,运用生物力学的理论知识来全面分析脊柱的力学改变及内固定器的作用机制,对于合理使用内固定器械以取得最满意矫形和固定效果具有重要意义。但现有实验条件及实验方法依然存在缺陷。例如,所有现有的实验均为体外实验,仅能反映即可实验结果,而且不能反映椎弓根螺钉在体内的长期力学特性。因此,本文通过椎弓根螺钉的自身设计、螺钉的植入技术、椎弓根螺钉的强化以及其他辅助椎弓根螺钉稳定性的辅助系统来全面分析脊柱椎弓根螺钉的生物力学。     

人工关节置换与加压螺钉内固定治疗高龄骨质疏松性股骨颈骨折的疗效观察

目的:探讨人工关节置换与加压螺钉内固定治疗高龄骨质疏松性股骨颈骨折的疗效。方法:选取2010年8月至2013年3月我院收治的120例高龄骨质疏松性股骨颈骨折患者,将所有患者随机分为人工置换组和内固定组两组,每组各60例,内固定组采用加压螺钉内固定术治疗,人工置换组采取人工关节置换术治疗,评定两组患者的手术时间、术中出血量、下地时间、术后并发症发生率及末次随访时Harris评分优良率。结果:人工置换组手术时间及术中出血量分别为(124.8±16.7)min、(369.2±99.7)ml,明显高于内固定组的(73.5±15.1)min、(78.4±25.6)ml;但人工置换组术后下地时间为(15.3±4.8)d,明显低于内固定组的(40.2±7.5)d;人工置换组与内固定组患者术后并发症的发生率分别为20%、66.7%,人工置换组明显低于内固定组,其中,泌尿系褥疮的组间差异最为显著;末次随访时Harris评分优良率,相比于内固定组的61.67%,人工置换组为78.33%,明显偏高。差异有统计学意义(P0.05)。结论:加压螺钉内固定术和人工关节置换术在治疗高龄骨质疏松性股骨颈骨折方面各有优劣,对于能够耐受人工关节置手术且经济条件好的的老年患者而言,采用人工关节置换术治疗,疗效更佳。     

锁定钢板固定术后内侧柱支撑能力与肱骨近端骨折患者预后的相关分析

目的:研究锁定钢板固定术后内侧柱的支撑能力与肱骨近端骨折患者预后的相关关系。方法:选取107例肱骨近端骨折患者作为研究对象,根据不同内侧柱支撑重建方式将所有患者分为四组,其中A组患者48例,均接受肱骨近端内侧骨皮质解剖复位以重建内侧柱支持;B组患者20例,均使用1枚支撑螺钉置入肱骨头内下方的软骨下骨,C组患者14例,均使用2枚或2枚以上支撑螺钉置入肱骨头内下方的软骨下骨;D组患者25例,均未进行肱骨近端内侧骨皮质解剖复位亦未使用锁定螺钉固定。比较各组患者术后Constant评分、VAS(visual analogue scale)评分、骨折愈合时间、肱骨头高度丟失值、肱骨头内翻角、并发症发生情况及二次手术率。结果:与无支撑重建组相比,骨皮质解剖复位组、单枚螺钉支撑重建组以及多枚螺钉支撑重建组的VAS评分、骨折愈合时间、肱骨头高度丟失值以及肱骨头内翻角均明显降低,而Constant评分明显升高,其中骨皮质解剖复位组的变化幅度最大多枚螺钉支撑重建组次之,单枚螺钉支撑重建组变化幅度最小,差异具有统计学意义(t=23.100,22.130,7.267,68.440,47.900,均P0.001);与无支撑重建组相比,骨皮质解剖复位组、单枚螺钉支撑重建组以及多枚螺钉支撑重建组的术后总并发症发生率和二次手术率均明显降低,其中骨皮质解剖复位组的降低幅度最大,单枚螺钉支撑重建组次之,多枚螺钉支撑重建组降低幅度最小差异具有统计学意义(X~2=12.938,11.904,P=0.005,0.008)。结论:锁骨钢板固定术后内侧柱的支撑能力与肱骨近端异型解剖钢板患者预后相关,内侧柱支撑能力的越高患者术后骨折愈合、肩关节恢复越佳,而并发症发生率以及二次手术率越低。