骶髂复合体及骶髂螺钉内固定的生物力学研究进展

随着对骨盆生物力学及解剖学认识的深化，近年来国际上更加重视骶髂关节整体结构的牛物力学，骶髂复合体的特殊生物力学特点在骨盆的功能中有着非常重要的意义，骶髂螺钉内固定成为较优越的固定方式。     

骶髂关节脱位直视复位空心螺钉固定的基础研究及临床应用

目的研究总结直视复位、经皮空心螺钉固定骶髂关节脱位的解剖学基础、生物力学稳定性以及初步的临床疗效。方法采用12具(24侧)福尔马林固定的尸体标本,测量骶骨翼上缘L_4、L_5神经根前支和闭孔神经至骶髂关节的距离。采用6具新鲜尸体骨盆标本建立骶髂关节脱位模型,比较本固定法与传统后路经皮骶髂关节螺钉和前路钢板固定的稳定性。同期采用本固定法手术治疗17例Tile C型骨折患者,随访疗效。结果①L_4、L_5神经根及闭孔神经分别距离骶髂关节(20．24±1．12)mm、(23．80±1．43)mm、(16．26±2．07)mm；②本固定方式与后路经皮骶髂关节螺钉的稳定性无显著性差异,但优于前路钢板固定；③临床治疗17例患者,平均随访2．2年,根据Matta功能评定标准,功能恢复均为优良。结论该固定系统具有良好的生物力学稳定性,同时可避免神经损伤、临床效果好、操作简便,便于基层医院开展。     

加长骶髂螺钉固定相关参数的放射解剖学研究

[目的]通过测定S1、S2加长骶髂螺钉可置钉区域的相关指标,为加长骶髂螺钉固定的临床实践提供解剖学依据。[方法]对66名成人进行骨盆CT扫描,对S1、S2加长骶髂螺钉可置钉区域的长、宽、高进行测量,对进钉点作量化定位。对上述指标行统计学描述,并对左右两侧、S1、S2两节段、S1、S2各自不同层面的同种数值进行比较。[结果]模拟左右两侧置钉的相关测量所得同种数值无显著性差异;S1、S2加长骶髂螺钉安全置钉区域的髂骨长度均>16 mm;S1、S2可置钉区域的宽、高均>7.3 mm,且整体而言S1比S2具有更大的宽度值和高度值;加长骶髂螺钉最佳进钉点的量化定位参考范围,S1:髂后上棘前方42.21～63.69mm,坐骨大切迹最高点上方32.77～53.75mm。S2:髂后上棘前方22.68～54.28 mm,坐骨大切迹最高点上方14.06～33.70 mm。[结论](1)S1、S2加长骶髂螺钉的置入具有解剖学的可行性;(2)同一节段左右两侧置入加长骶髂螺钉的各项指标无差异;(3)螺纹长度为16mm的7.3 mm部分螺纹空心钉和6.5 mm部分螺纹松质骨螺钉均可作为加长骶髂拉力螺钉使用;(4)S1、S2均有置入至...     

下颈椎经关节螺钉固定的生物力学研究

目的比较下颈椎经关节螺钉3层皮质和4层皮质固定的生物力学拔出力的区别。方法10具新鲜尸体颈椎标本（C3-T1），游离成3个颈椎运动节段（C3～C4、C5～C6、C7～T1），在椎体两侧随机进行经关节螺钉3层皮质和4层皮质固定，置入直径为3．5mm的皮质骨螺钉。置入经关节螺钉行拔出力试验，比较经关节螺钉2种固定方式的最大轴向拔出力。结果下颈椎经关节螺钉4层皮质固定的平均拔出力为430N，而3层皮质固定的平均拔出力为412N，但两者间差异无统计学意义（P〉0．05）。经关节螺钉两种固定方式在颈椎各节段间差异无统计学意义（P〉0．05）。结论下颈椎后路经关节螺钉3层皮质固定的力学性能与4层皮质固定差异并不明显。经关节螺钉3层皮质固定可能在减少和避免置钉相关的神经血管损伤并发症方面有着重要的临床意义。     

骨水泥修复颈椎前路椎体螺钉钉道的生物力学研究

目的 评价聚甲基丙烯酸甲酯(Polymethylmethacrylate,PMMA)修复颈椎前路椎体螺钉钉道的生物力学效果。方法 防腐成人颈椎标本(C_3~7)共30个,分3组:正常骨密度组(A组)、骨质疏松组(B组),骨质疏松修复组(C组),各组10个标本,测试疲劳前后的最大轴向拔出力。A、B对照组椎体二侧钉孔均放置4 mm的椎体螺钉,随机选择一侧行即时最大拔出力实验,另一侧在疲劳实验(2 Hz,20 000次)后行最大拔出力实验。C组(实验前需进行螺钉拔松实验)注入PMMA 0.6~1.0 mL,并拧入螺钉,随机选择一侧进行即时和疲劳后最大拔出力实验。结果 A、B、C组即时拔出力明显高于疲劳后拔出力,差异具有统计学意义(P< 0.05),C组疲劳后与A组即时拔出力比较,差异无统计学意义(P >0.05),但高于B组即时拔出力,差异具有统计学意义(P< 0.05)。即时拔出力C组 >A组 >B组,差异均有统计学意义(P< 0.05)。疲劳后拔出力C组 >A组 >B组,差异均有统计学意义(P< 0.05)。PMMA注射后未发现钉道渗漏。结论 PMMA钉道修复能够明显增强椎体螺钉的即时稳定性和抗疲劳能力, 并且安全有效,适用于螺钉松动和拔出的修复固定。     

A biomechanical study of intrapeduncular screw fixation in the lumbosacral spine

This laboratory experiment was undertaken to identify factors contributing to intrapeduncular screw fixation in the vertebra. Testing was performed in axial pull-out and cyclic loading modes using multiple screw designs inserted to various depths into fresh human lumbosacral vertebra. The degree of osteoporosis played a major role in pull-out strength. Larger diameter, full-threaded screws inserted deep enough to engage the anterior vertebral cortex resulted in the most secure fixation. In the sacrum, the second sacral pedicle was the weakest location of insertion. Screws aimed laterally into the ala at 45 degrees or medially into the first sacral pedicle resisted larger axial pull-out loads than those inserted straight anteriorly into the ala. Methyl methacrylate was found to restore secure fixation in previously-loosened screws and pressurization of cement doubled the pull-out force. In cyclic load tests, deeper-inserted screws were found to withstand a greater number of cycles before loosening. Measurements of pedicle outer cortical diameters were found in many specimens to be smaller than both the 4.5-mm and 6.5-mm diameter screws.     

Computed tomography-guided screw fixation of a sacroiliac joint dislocation fracture: a case report

A 19-year-old woman sustained a vertical shear type pelvic fracture. Sacroiliac fixation using computed tomography (CT)-guided cannulated screws was performed for a left sacroiliac dislocation fracture, and a satisfactory result was obtained over time. Patients who have posterior instability of the lateral compression or vertical shear type do not obtain adequate stability by fixation of the anterior part alone; and they often have persistent residual pain, necessitating internal fixation of the posterior part later. Advantages of CT-guided sacroiliac screw fixation include precise evaluation of the degree of reduction and absence of nerve and vascular damage during the time the screw is inserted into the sacral body. This procedure is a useful, safe method owing to its minimal invasiveness in patients with unstable pelvic fractures that are reducible by manual manipulation or traction.     

Intramedullary screw fixation of Jones fractures: a biomechanical study.

The management of proximal fifth metatarsal ("Jones") fractures in athletes has become increasingly more aggressive, despite a lack of biomechanical data in the literature. A cadaver biomechanical study was conducted to evaluate the strength of intramedullary fixation of simulated Jones fractures loaded to failure via three-point bending on a Materials Testing System machine. In a series of eight intact fifth metatarsal control specimens, the force to failure (fracture) was measured for comparison with repaired specimens. Acute fractures were simulated in 10 pairs of feet via osteotomy at the typical fracture location and were fixed with either a 4.5-mm malleolar screw or a 4.5-mm partially threaded, cancellous, cannulated screw, both placed using conventional intramedullary techniques. Force at initial displacement averaged 73.9 N (SD, 64.7 N) for the malleolar screws and 72.5 N (SD, 42.3 N) for the cannulated screws. Force at complete displacement averaged 519.3 N (SD, 226.2 N) for the malleolar screws and 608.4 N (SD, 179.7 N) for the cannulated screws. The force to failure of the intact specimens was significantly greater than the initial and complete forces to failure for the fixed specimens (P < 0.05, independent measures analysis of variance). There was no statistical difference between the average forces at initial displacement or at complete displacement in the fixed metatarsal specimens for the two different types of screws, but the forces at complete displacement for each screw type were significantly greater than the forces at initial displacement (P < 0.05). On the basis of literature review and data generated from this study, it is apparent that the forces necessary to cause displacement of the stabilized Jones fracture are above what would be transmitted within the lateral midfoot during normal weightbearing. The choice of screw and intramedullary technique of fixation is a matter of surgeon preference, because the choice of screw makes no biomechanical difference.     

Percutaneous sacroiliac screw fixation in fragility fractures of the pelvis: Comparison of two different augmentation techniques

ObjectiveFragility fractures of the pelvis (FFP) are becoming increasingly common. Percutaneous sacroiliac screw fixation is an accepted and safe treatment method for FFP. Augmentation is an option to optimize fixation strength of the screws. This study aims to compare patient mobility and the occurrence of complications after operative treatment of FFP utilizing two different augmentation techniques.MethodsAll patients who received augmented sacroiliac screws for the treatment of FFPs between 01.01.2017 and 31.12.2018 at one of the two participating hospitals were included. The operative techniques only differed with regards to the augmentation method used. At the one hospital cannulated screws were used. Definitive screw placement followed augmentation. At the other hospital cannulated and fenestrated screws were used, permitting definitive screw placement prior to augmentation.ResultsIn total, 59 patients were included. The NRS score for pain was significantly lower after surgery. Preoperative mobility levels could be maintained or improved in 2/3 of the patients. There were no fatal complications. Two revision surgeries were performed because of screw misplacement. There were no significant differences between the two augmentation techniques in terms of complications.ConclusionBoth augmentation techniques have a low complication rate and are safe methods to maintain patients’ mobility level. The authors advocate early consideration of surgical treatment for patients with FFP. Augmentation can be considered a safe addition when performing percutaneous sacroiliac screw fixation.     

骶髂关节螺钉固定应用及CT与解剖学研究

目的 :采用CT扫描测量髂骨翼后外侧面至第 1骶椎 (S1)的距离和S1椎弓根宽 ,为临床上经骶髂关节螺钉固定治疗后骨盆环不稳定提供参考。方法 :对 2 2例中国成人的骨盆标本共 4 4侧骶髂关节进行CT和解剖学研究 ,测量S1椎弓根宽 ,髂骨翼后外侧面的进针点至S1椎弓根中心距离 ,进针点至S1椎体对侧前皮质距离 ,并对解剖测量值和CT测量值进行比较。在实验研究的基础上 ,对 11例垂直不稳定后骨盆环骨折进行骶髂螺钉固定。结果 :髂骨翼后外侧面的进针点至椎弓根中心距离解剖和CT测量值分别为 4 9 5± 4 0mm和 4 9 2± 3 9mm ,两者差异无显著性 (P >0 0 5 ) ;进针点至S1椎体对侧前皮质距离解剖和CT测量值分别为 86 9± 4 6mm和 86 4± 4 4mm ,两者差异无显著性 (P >0 0 5 ) ;S1椎弓根宽解剖和CT测量值分别为 2 7 7± 2 0mm和 2 0 7± 2 5mm ,两者差异有显著性 (P <0 0 1)。临床 11例共 13枚骶髂螺钉均准确置入 ,无骨皮质穿破或神经血管损伤等并发症。结论 :术前CT扫描可准确地推算骶髂螺钉长度 ,具有临床实用意义。     

Percutaneous screw fixation for scaphoid nonunion in skeletally immature patients: a report of two cases

Nonunion of the scaphoid waist in skeletally immature patients is rarely diagnosed. We report 2 cases of scaphoid nonunion in skeletally immature patients who underwent percutaneous screw fixation without bone graft. In stable nonunions with minimal sclerosis, percutaneous screw fixation without bone graft can be an alternative to the conventional open procedure in skeletally immature patients, with successful union and clinical outcome.     

Intramedullary screw fixation of proximal fifth metatarsal fractures: a biomechanical study

Intramedullary screw fixation is a popular technique for treatment of proximal fifth metatarsal fractures. The purpose of this study was to compare the fixation rigidity of a 5.5 mm partially threaded cannulated titanium screw, with presumed superior endosteal purchase, to a similar 4.5 mm screw. Acute fifth metatarsal fractures were simulated in cadavers, stabilized with intramedullary screws, and loaded to failure in three-point bending. The initial failure loads for the metatarsals fixed with 4.5 mm and 5.5 mm screws were not significantly different (332.4 N vs. 335.2 N, respectively), nor were the ultimate failure loads (849.8 N vs. 702.2 N, respectively). Based upon our results, maximizing screw diameter does not appear to be critical for fixation rigidity and may increase the risk of intraoperative or postoperative fracture.     

Supplemental S1 fixation for type C pelvic ring injuries: biomechanical study of a long iliosacral versus a transsacral screw

Background

A single iliosacral screw placed into the S1 vertebral body has been shown to be clinically unreliable for certain type C pelvic ring injuries. Insertion of a second supplemental iliosacral screw into the S1 or S2 vertebral body has been widely used. However, clinical fixation failures have been reported using this technique, and a supplemental long iliosacral or transsacral screw has been used. The purpose of this study was to compare the biomechanical effect of a supplemental S1 long iliosacral screw versus a transsacral screw in an unstable type C vertically oriented sacral fracture model.

Materials and methods

A type C pelvic ring injury was created in ten osteopenic/osteoporotic cadaver pelves by performing vertical osteotomies through zone 2 of the sacrum and the ipsilateral pubic rami. The sacrum was reduced maintaining a 2-mm fracture gap to simulate a closed-reduction model. All specimens were fixed using one 7.0-mm iliosacral screw into the S1 body. A supplemental long iliosacral screw was placed into the S1 body in five specimens. A supplemental transsacral S1 screw was placed in the other five. Each pelvis underwent 100,000 cycles at 250 N, followed by loading to failure. Vertical displacements at 25,000, 50,000, 75,000, and 100,000 cycles and failure force were recorded.

Results

Vertical displacement increased significantly (p < 0.05) within each group with each increase in the number of cycles. However, there was no statistically significant difference between groups in displacement or load to failure.

Conclusions

Although intuitively a transsacral screw may seem to be better than a long iliosacral screw in conveying additional stability to an unstable sacral fracture fixation construct, we were not able to identify any biomechanical advantage of one method over the other.

Level of evidence

Does not apply—biomechanical study.     

A biomechanical study of unilateral posterior atlantoaxial transarticular screw fixation

The purpose of this study was to investigate the fixation of C1-C2 instability with the use of a unilateral screw. Transarticular screw placement across C1-C2 may be contra-indicated in up to 20% of specimens on at least one side because of anatomic variations or other pathological processes. Hence the current study looks into unilateral screw fixation of C1- C2 instability. Eight cervical spine specimens, C1 through C5, were harvested from fresh human cadavers (4 male and 4 female) of average age 67 years (54-80). C1 and C2-C5 vertebrae were potted to allow motion only at the C1-C2 articulation. Cutting the transverse ligament on both sides of the odontoid and the tectorial membrane destabilized the specimens. Transarticular screw fixation of C1-C2 was performed in a manner similar to the technique described by Magerl. The stability was tested after fixation with one transarticular screw together with a posterior graft and wire. Placement of the screw was randomized, resulting in half the specimens receiving screws on the right side and the remaining half on the left side. The stiffness of the C1-C2 articulation was tested in rotation, lateral bending, flexion, and anterior translation in random order. The rotational stiffness was 1.44 +/- 0.44 N-m/deg, while lateral bending stiffness values were 2.33 +/- 1.14 N-m/mm (right bending) and 2.81 +/- 1.36 N-m/mm (left bending). The stiffness value in flexion was 0.813 +/- 0.189 N-m/mm and in translation 67.1 +/- 25.1 N/m. It was found that stability after unilateral transarticular screw fixation was less than that previously reported after bilateral transarticular screw fixation, but similar to that found with modified Brooks posterior wiring, which has been shown to provide better stability than other posterior wiring methods, and fusion rates of 96% have been reported. We concluded that C1-C2 unilateral posterior transarticular screw fixation with supplemental posterior graft and wiring would confer adequate stability in cases where bilateral screw placement is contraindicated.     

骶骨螺钉经上终板与经前皮质固定的生物力学比较

目的测试骶骨螺钉经上终板固定技术的生物力学性能,并与经前皮质固定技术比较。方法取17具新鲜成年男性骶骨标本,两侧分别采用螺钉经上终板固定和经前皮质固定技术。经前皮质固定的螺钉指向前内侧,平行于终板;经上终板固定的螺钉指向前内侧,矢状面上向头侧成30°～35°角,钉尖对向S1上终板的前部。植入螺钉时测定最大扭矩;通过模拟生理应力进行疲劳试验,测定固定刚度变化和拔出力。结果经上终板固定组螺钉最大扭矩为(3.18±0.49)Nm,经前皮质固定组为(1.98±0.76)Nm, 差异有非常显著性(P< 0.01),经上终板固定组比经前皮质固定组高60.6%; 经上终板固定组拔出力为(1457±276)N,经前皮质固定组为(1122±364)N, 差异有显著性(P< 0.05),经上终板固定组比经前皮质固定组高29.9%;在循环负载过程中,两组刚度在负载早期(前5000个循环)均明显下降,然后趋于平稳,经上终板固定组的最后刚度高于经前皮质固定组(P< 0.05)。两组中螺钉的最大扭矩与拔出力均有显著相关性,相关系数分别为0.94和0.95(P< 0.01)。结论骶骨螺钉经上终板固定技术与经前皮质固定技术相比有一定的力学优越性。     

Accuracy of computer-guided screw fixation of the sacroiliac joint.

Computer-assisted image guidance allows precise preoperative planning and intraoperative localization of surgical instruments. The technique recently was validated for the insertion of pedicle screws. In the laboratory, the precision of a surface-matching algorithm was evaluated for registration and accuracy and safety of screw placement into the vertebral bodies of S1 and S2 for fixation of the sacroiliac joint. Using six plastic pelves, 24 screw holes were made through the sacroiliac joint into the vertebral body of S1, and 12 holes were made through the sacroiliac joint into S2. The accuracy of the hole position was evaluated using a postoperative computed tomography examination. The safety factor was assessed by analysis of the remaining bone stock around the holes calculating a theoretical cylindrical volume being outside bone with increasing bore hole diameters. The registration was accurate with a mean error less than 1.4 mm in the posterior parts of the pelvis. The drilling followed precisely the preoperatively planned trajectories; perforation of the cortex of the sacrum was not observed. The safety factor of the S1 vertebral body is higher than that of S2 allowing larger diameter screw insertion into S1. This technique provides a safe and precise guide for transcutaneous or open insertion of iliosacral screws in cases of iliosacral dislocation or sacral fracture.     

L5/S1和骶髂关节对腰-髂固定稳定性影响的生物力学分析

目的:探讨L5/S1和骶髂关节对腰-髂固定稳定性的影响,为腰-髂稳定性理想重建提供生物力学依据.方法:7具成年新鲜尸体L2-骨盆标本,先行L3～L5椎弓根螺钉固定,并将此结构定义为腰-髂部稳定初始状态.初始状态测试后,在同一标本上实施连续性操作如下:使用髂骨钉的L3-髂骨固定(A组)、L5/S1双侧关节突关节切除(B组)、L5/S1椎间盘切除(C组)、左侧骶髂关节切除(D组).在MTS材料实验机上,给标本头侧分别施加600N轴向压缩和7Nm轴向扭转载荷,计算并比较各组结构压缩和扭转刚度.结果:初始状态组的压缩刚度值为(332±103)N/mm,A～D组腰-髂固定结构的压缩刚度分别为初始状态组的(122±15.5)％、(118.3±10.5)％、(81.1±7.7)％和(59.2±8.6)％.A和B组间无显著性差异(P＞0.05),两组的压缩刚度均显著高于初始状态组(P＜0.05);C组和D组的压缩刚度均显著低于A、B组及初始状态组(P＜0.05),C组和D组间的差异也具有显著性(P＜0.05).初始状态组的扭转刚度值为(2.47±0.88)Nm/deg,A～D组固定结构的扭转刚度分别为初始状态组的(128±14.3)％、(120±12.6)％、(78.4±13.2)％和(62.9±11.3)％,A组和B组获得同等的扭转刚度(P＞0.05),而且此两组的扭转刚度均显著高于初始状态、C组和D组(P＜0.05),C、D组和初始状态三组彼此间的差异均具有显著性(P＜0.05).结论:L5/S1椎间盘切除和单侧骶髂关节切除均显著降低腰-髂固定结构的稳定性,在腰-髂稳定性重建中,获得脊柱前方支撑和恢复骨盆环完整性是提高腰-髂固定结构稳定性的关键.