摘要
1．背景
随着高能量损伤的迅速增加，骨盆骨折的发病率逐年提高；由于近年来复苏技术、介入治疗等广泛开展，骨盆骨折的死亡率已下降至5-20％，大多数骨盆骨折患者得以生存，从而进入骨盆骨折的治疗阶段。在骨盆骨折治疗概念不断更新中，骨盆诸韧带生物力学作用的研究逐渐引起国内外专家的关注；我们对临床上较为多见的骨盆外旋不稳定(骨盆翻书样损伤)中骶髂关节前方韧带的生物力学作用进行研究，以明确骶髂螺钉在不同方向置钉的情况下对骨盆外旋不稳定的生物力学影响，为骨盆骨折的临床治疗提供依据。
2．目的
观测和测量不同进针点骶髂螺钉置钉对骨盆外旋不稳定的生物力学影响，以期为临床应用提供实验依据。
3．材料与方法
3．1一般资料
10具新鲜冷冻保存的正常成人骨盆标本由浙江大学医学院解剖教研室提供，排除明显骨盆畸形、骨折和肿瘤等病变，对骨盆周围肌肉仔细剔除，完整保留骶髂前后韧带、骶髂间韧带、骶棘韧带、骶结节韧带，切断耻骨联合。线性测量采用精确度为0.01mm的位移电子引伸计，拉力测量采用德国Zwick／010电子万能材料试验机。
3．2进针方法：
分别于髂骨外板A、B、C点作为不同方向的进针点。其中B点进针法即为髂后下棘前2.5cm与坐骨大切迹上4.0cm的交点、与髂骨板呈向下向后各5°-10°的我们研究的进针法定位点，A点为B点同一水平面前方1.0cm、与髂骨板呈头倾5-10°和腹倾55-60°的定位点，C点为B点同一水平面后方1.0cm、与髂骨板呈头倾5°-10°和腹倾40°-45°的定位点。
3．3加载方式：
将标本放在特制的骨盆标本夹具上，在耻骨结节处垂直于耻骨联合方向施加2mm／min加速度的外旋力，外旋力的方向与标本的髂前上棘连线基本平行，电子万能材料试验机提供的力的大小同步反应在计算机上。
3．4耻骨联合分离测量方法：
将标本放在特制的骨盆标本夹具上，距耻骨联合切断面上方外缘各1.0cm均钉入一枚3.5mm螺钉，用以固定位移电子引伸计，螺钉与骨面垂直，两钉连线与标本的髂前上棘连线平行，于加载前后用位移电子引伸计精确测量耻骨联合分离的距离。测量力的数值由专人负责读数，每次测量前均给予适当力予加载-卸载三次，以消除标本的粘弹性影响。
3．5骶髂关节裂缝移位测量方法：
在同侧第一骶前孔连线水平、骶髂关节前缘两侧各钉入一3.5mm螺钉以固定位移电子引伸计，螺钉与骨面垂直，两钉连线与骶髂关节面垂直，相距约2.0cm，于加载前后用位移电子引伸计精确测量骶髂关节裂缝移位的距离，测量的数值由专人负责读数。
3．6统计学处理
采用SPSS13.0统计软件包计进行统计分析，数据均以均数±标准差行(X±S)表示，左右侧之间比较采用配对t检验，a值取0.05，P＜0.05认为差异具有显著性。
4．结果
形态解剖学测量及生物力学测定结果左右侧别比较(配对t检验)，统计分析显示差异无显著性(P＞0.05)。故在进一步分析中将左右侧别之间的数据按测量方法并在一起处理。
4．1耻骨联合分离测量结果
(1)本实验在一定向外分离速度下(2mm／min)的作用下，力-耻骨联合间距位移回归曲线均呈类似直线关系。
(2)在相同的向外分离速度下(2mm／min)不同的比较组间最大抗外旋力大小不一致，以韧带完整组最大(F0=260N±40N)，其次为A点进针组(F1=180N±30N)和B点进针组(F2=160±30N)，最差为C点进针组(F3=50N±10N)。
(3)为了便于数据的可比性和统计分析，各组均在最大外旋力为120N下进行位移与抗外旋力的统计分析，韧带组、C进针点组与A／B组均存在显著性差异(P＜0.05)；A、B进针点组之间没有显著性差异(P＞0.05)。
4．2骶髂关节裂缝移位测量结果
①耻骨联合的分离与骶髂关节裂缝的移位呈线性相关，在耻骨联合轻度分离时(＜0.5cm±0.1cm)骶髂关节出现关节不稳定；在耻骨联合分离达3.5cm±0.5cm时骶髂关节前方关节囊及韧带断裂。
②为了便于数据的处理，各组均在最大外旋力为120N下进行对抗骶髂关节裂缝移位和骶髂关节稳定性的统计分析，韧带组／B进针点组、A进针点组与C进针点组均存在显著性差异(P＜0.05)；韧带组、B进针点组之间没有显著性差异(P＞0.05)。
5．结论
(1)经S1椎弓根水平骶髂关节螺钉固定的不同方向进针点中，A点和B点进针点对外旋不稳定有良好的对抗作用，C点进针点对外旋不稳定几乎没有对抗作用。
(2)A点和B点进针法在对抗外旋力方面没有显著性差异，但对骶髂关节稳定性B进针点组更为优越。结合应用解剖特点，我们认为B点更为安全，为最佳进针点。
1. Background
With the increase of high-energy injuries, incidence of pelvic fracture increased year by year. The death rate of the pelvic fracture had descended to 5%-20%, due to the widespread carry-out of resuscitation technique and interventional therapy, most sufferer can exist, we had got into the stage of surgical treatment of the pelvic fracture. With the development of the treatment concept of the pelvic fracture, mote and more domestic and international expert payed attention to the biomechamcal function of anterior sacroiliac ligament; we studied the biomechamcal function of this ligament in pelvic extorsion instability (pelvic "open book" injury) which usually happened in clinic, in order to identify the biomechamcal effect of sacroiliac screw with different needling point and found experiment evidence for the clinical treatment of pelvic fracture.
2. Objective
Observe and measure the biomechamcal effect of pelvic extorsion instability with different needleing-point of sacroiliac screw fixation, in order to found evidence for clinical application.
3. Material and method 3.1 General data
10 specimens of fresh refrigerant adult pelvic were supplied by Anatomy Department of Medical College of Zhejiang University. Pelvic deformity, fracture
and tumor were excluded. We got rid of the muscles surrounding pelvic carefully, anterior and posterior sacroiliac ligaments、inter-sacroiliac ligament、 sacrospinale ligament and sacrosciatic ligament were reserved completely. Accurate rating of 0.01mm displacement electronic explication machine was used to measure the distance and German Zwick/010 electronic almighty material test machine was used to measure the tensile force.
3.2 Needling method
We drilled on different point(A, B and C) at the external circumferential lamella of iliac bone respectively. The point B was at 2.5cm anterior of posterior inferior iliac spine and 4.0cm upper of greater sciatic notch ,with 5°-10°headtilt and abdomentilt of iliac bone respectively, which we had studied before.The point A was at 1.0 cm anterior of the horizontal plane for the point B, with 5-10°headtilt and 55°-60°abdomentilt of flank bone. The point C was at 1.0 cm posterior of the horizontal plane for the point B, with 5°-10°headtilt and 40°-45°abdomentilt of flank bone.
33 Loading way
Put the specimen onto special pelvic fixation device, extorsion force of 2 mm/min acceleration was added in the direction of pubic tubercle perpendicular to pubic symphysis, the direction of the extorsion force was in parallel with the line of spina iliaca anterior superior of the specimen. The tensile force provided by electronic almighty material test machine was imported to the computer.
3.4 Measure method of pubic symphysis diastasis
Put the specimen onto special pelvic fixation device, insert a 3.5mm screw 1.0cm above the pubic symphysis section both sides, in order to fix the displacement electronic explication machine. The nails were vertical to the iliac bone , the line of two nails was in parallel with the line of spina iliaca anterior superior. The explication machine was used to measure the distance of diastasis of the symphysis pubis. Special researchers were responsible to read the number of the force. Gave appropriate force to load-unload three times before each measurement to eliminate the effect of viscoelastic properties.
3.5 Measure the shifting of sacroiliac joint crack
Inserted a 3.5mm screw each side of anterior sacroiliac joint on the line of right first anterior sacral foramina, then the specimen was fixed to the electronic explication machine. Nail was vertical to facies ossea, the line of two nails was vertical to iliosacral articulation surface and aparted from 2.0cm between two nails. Measured the distance precisely with electronic explication machine before and after the force was loaded. Special researchers was responsible to read the number of the force.
3.6 Statistical treatment
SPSS13.0 was used to preform statistical analysis, all the data was written as mean ± standardized deviate(x ± s),use t test to compare the two sides. a=0.05,the difference was statisticly significant if p<0.05.
4. Results
4.1 Results of pubic symphysis diastasis measurement
(1)Under certain loading in this experiment, the curve of force-pubic symphysis distance was similar to straight line at a abruption speed of 2mm/min.
(2) At the speed of 2mm/min,the maximum force of extorsion was diverse in different groups. The group of integrity ligament was biggest(F0=280N±40N),and then the group of needling point A(F1=180N±30N),the group of needling point B(F2=160N±30N),and the group of needling point C(F3=120N± 10N).
(3) To be easy to preform statistical analysis, all the group of bias-extorsion force statistic were at a maximum speed of 120N. The difference between integrity ligament-needling point C group and needling point A/B group was statisticly significant; the difference between needling point A and B was not statisticly significant.
4.2 Results of iliosacral articulation crack shifting measurement
(1) The shifting between iliosacral articulation crack and pubic symphysis was linear correlation. When symphysis pubis dislocated gently(<0.5cm ± 0.1cm),
sacroiliac articulation becomed unstable; if the distance ≥3.5cm ± 0.5cm, the anterior articular capsule and ligament of iliosacral articulation would collapse. (2) Each group was statistical analysised at 120N extorsion in opposition of iliosacral articulation shifting and stability of iliosacral articulation. The group of integrity ligament with the group B, the group A with the group B was significantly different (P<0. 05) , but the group of integrity ligament with the group C not (P >0.05) .
5. Conclusion
(1)With different needling point screw fixation of iliosacral articulation in the level of S1 lateral mass of vertebrar, The antagonism of extorsion instability was favourable with needling point A and B. The needling point C mostly didn't provide antagonism of extorsion instablility.
(2)The difference of confronting extorsion force between needling point A and B was not statisticly significant, but the point B was better in stability of iliosacral articulation. We presume needling point B was the best and safest point because of the anatomy feature of the pelvis.
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