| Prior to the 1960s,conservative treatment was an absolute advantage in the treatment of pelvic acetabular fractures.This was mainly because pelvic acetabular fractures were often caused by high energy damage.Most cases were complicated by other intraabdominal organ injuries,even threatening life,which made diagnosis difficult and management complex.In addition,pelvis and acetabulum are deep in body with complicated anatomic structures,and adjacents to the pelvic visceras and important nerve,and blood vessels.The surgery itself may lead to a large number of bleeding risk,making the conservative treatment of pelvic injuries to be first choice.In the 1960 s,As the pelvic acetabulum fracture classification and surgical approaches and reduction and fixation technique had been put forward by the two professors of Judet and Letournel,the modern conception of pelvic acetabulum fracture treatment gradually established.The surgical treatment was gradually accepted by most of traumatic orthopedic surgeons and widely used in clinical.Since the early 1990s,Chinese doctors had been gradually exposed to pelvic acetabular surgery.Over the past 20 years,with the development of the internal fixation technology and imaging,starting pelvic acetabulum classes,in-depth communication of technology at home and abroad,it led to the rapid development of diagnosis and treatment of the domestic pelvic and hip fracture.However,up to now,it is undeniable that pelvic fractures still have many problems to be solved in clinical treatment,which is still a very difficult problem faced by orthopaedic surgeonsAs a complex and serious injury pelvic fracture,it is often complicated by the simultaneous injury of the bone and ligament.Postoperative persistent pain,restricted movement,and unstable gait are still common.Of all them,especially the lower back pain coming from the sacroiliac joint often brings inconvenience to patients.It is closely related to the clinical doctors’ lack of understanding of the pelvic injury mechanism and the anatomy and function of the surrounding ligament of the sacroiliac joint.The sacroiliac joint is an important structure to support the body load and to complete the mechanical conduction.The integrity of its anatomy and function is crucial to the stability of the pelvic ring.Clinicians only tend to focus on the repair of bone structural damage and neglect the repair of soft tissues such as the ligaments around the sacroiliac joint,which insufficient attention is paid to for the soft tissues around the sacroiliac joint.Therefore,although the recent curative of sacroiliac joint injury is still effective,the long-term prognosis is often unsatisfactory.Since the 1990 s,according to pelvic injury mechanisms,prefessor Young and Burgess had established Young-Burgess pelvic fractures classification system,Orthopaedic surgeons had a preliminary knowledge and understanding to the mechanismof various types of pelvic fractures,especially anteroposterior compression pelvic injury,is considered to be the most typical pelvic ligaments injury.According to different types of fracture,the clinical doctors derived the mechanism of injury and violence and made the treatment plan,which is still widely used in clinical practice,which brings good news to the patients.However,without understanding inadequately the bone and ligament injury mechanisms of various pelvis fracture,many clinicians were only familiar with the clinical classification of pelvic fractures in general and then often misdiagnosed,bringing great pains to the patients.There are still many arguments about pelvic injury mechanism.Always study of sacroiliac complex mainly included such as anatomical morphology of sacroiliac joint,the biomechanics of ligament surrounding sacroiliac joints,movement mode and range,etc.However,due to its unique anatomy,biomechanical properties and its ambiguous showing imaging examination,all of these are added to our difficulty of cognitive pelvic,especially sacroiliac joint,diseases.Thus,the relevant study on pelvis is still less,there are many problems remain to be further research and exploration.Biomechanics mainly includes experimental biomechanical research and theoretical biomechanical research.The two methods complement and coordinate with each other.In general,experimental biomechanics is the basis of computational biomechanics and provides the check and auxiliary conditions for it.And computational biomechanics provides the development space for experimental biomechanics.With the continuous development of three-dimension finite element technology,its application makes the study of pelvic bones-ligament damage more economic,convenient.It had an advantage of a sufficient sample size,the precision data results and good adaptability.Currently,combining with the finite element model and traditional method of biological mechanics on basic and clinical research in orthopaedic field is playing an increasingly important role.With the improvement of the computer hardware and software performance,it will produce an universal model and can be used to evaluate and develop a plan of preoperative and postoperative.On the basis of pelvic CT,our experimental design will combine with finite element technology and experimental mechanics,and established related pelvic injury model.We will attain the results by analysis and calculation of finite element model and specimen simulation of pelvic injury mechanism from the following five parts for research.Part 1:Construction and validation normal finite element model of pelvisbone-ligamentObjective:To establish an effective finite element model of pelvis bone-ligament,and provide the basis for the following study regarding constructing finite element model of anteroposterior compression pelvic injury.Methods:A specimen of the pelvis was obtained from adult male cadavers,with 44years old,height 172cm and weight 70Kg.Based on scanning CT of the volunteer’s pelvis,three dimensional DICOM format image of pelvis could be obtained.Mimics,Geomagic and Solidworks software were used to building a pelvic bone-ligament finite element model and drawing relevant ligaments around the pelvis.Then we coped with and imported the model into Ansys software to assign material attribute,mesh,optimize smooth.A three-dimensional finite element model of pelvic bone-ligament was established and tested for its effectiveness.Results:Between before and after the optimization of the pelvic bone-ligament model,the distance between the bony salient points of the pelvis acetabulum had no significant difference(P>0.05).The finite element analysis showed that the overall deformation of the pelvis was centered on the sacrum,and the two sides of the pelvis were weakened,and the left and right sides were basically symmetrical.The results were in accordance with theoretical knowledge and relevant research.The established model proved to be effective.Conclusions:Using three-dimension finite element technology to build the pelvic bones-ligament three-dimensional finite element model objectively could reflect the real pelvis anatomy morphology and biomechanical behavior.The established finite element model of pelvic bones-ligament morphology and mechanics can be used for future experimental research.Part 2:Establishment of a three-dimensional finite element model of anteroposterior compression pelvic injury and analysis of the related ligament damage mechanismObjective:To establish a three-dimensional finite element model and explore damage mechanism of anteroposterior compression(APC)pelvic injury.Methods:A normal human pelvic bone-ligament finite element model was established and verified.Test models of APC type of pelvic ring injuries were created.The right hemipelvis was constrained and fixed without movement.Pubic symphysis(PS)was sectioned and a manual external mobile force was gradually then applied to the left hemipelvis to move towards external purely.the PS diastasis was divided to 10mm,15mm,20mm,25mm,30mm,35mm,40mm,60mm,80mm,100mm.We simulated APC type of pelvic fracture mechanics tests in the same pelvic specimen and anterior sacroiliac ligament(ASIL)was found to rupture when the PS diastasis reached 28 mm.The strain value of ASIL was calculated through the finite element model,and applied to the other pelvic ligaments assignment model.The displacement in front of sacroiliac joint(SIJ),the stress,strain and the extent of injury and disruption of sacrotubemus/sacrospinous ligament(STL/SSL)with a corresponding PS diastasis were observed and recorded.Results:ASIL was failed at the point of the PS diastasis being 28mm when the displacement in front of SIJ was 7.41mm.The calculating strain and maximum principal stress value of ASIL through the finite element model was 259.5%and 543.24MPa respectively.The maximum principal stress value of SSL was 35.00MPa at the point of failure When the PS diastasis and the displacement in front of sacroiliac joint was 51 mm and 15.23 mm respectively.The maximum principal stress value of STL was 13.17MPa with the strain of ligament not the rupture and failure even if the PS diastasis and the displacement in front of sacroiliac joint was 100 mm and 7.5 mm respectively.The ASIL failure was followed by rupture of the SSL,and then the STL was not necessary to failure.The STL may limit the movement of SSL towards to back as the hemipelvis gradually rotated externally.Conclusions:The established pelvic bone-ligament model could effectively simulate APC type of pelvic injury mechanism and evaluate the extent of pelvic ligamental injury,providing a basis for the study of biomechanics of the pelvic bones and ligaments.Part 3:Finite element analysis of the impact of pelvic vertical stability ofrelevant ligament in anteroposterior compression II type pelvic injury.Objective:to study the effect of maintaining pelvic vertical stability of anterior sacroiliac ligament(ASIL),sacrospinous ligament(SSL),sacrotubemus ligament(STL)in anteroposterior compression Ⅱ type pelvic injury.Methods:A normal human pelvic bone-ligament finite element model was established and verified.Test models of APC type of pelvic ring injuries were created.The pubic symphysis(PS)of the model were then divided into A,B,C,D,E five groups according to the ligament rupture order APC II type injury.Of all three ASIL,SSL and STL ligaments,Group A1:only cut off ASIL;Group A2:cut off SSL and STL,but without ASIL;Group B1:only cut off the SSL,Group B2:cut off ASIL and STL,but without SSL;Group C1:cut off STL,C2 group:cut off ASIL and SSL,but without STL;Group D:ASIL,SSL and STL were cut off.Group D ASIL,SSL and STL were retained.After the physiological being loaded,the finite element calculation was performed to record the displacement of the sacroiliac joint and the stress and strain distribution of ASIL,SSL and STL.Results:Of all the five models,the displacement of sacroiliac joint was not obvious whether the PS and ASIL,SSL or STL were sectioned or not.The displacement of the sacroiliac joint was Group A1>Group B1>Group C1;group C2>group B2>group A2.In all the groups,the displacement of group D and E of was the largest and smallest respectively.And the stress and strain of each group were ASIL>SSL>STL.Conclusion:In unilateral APC II type pelvic injury,the ASIL,SSL,STL ligaments have little effect on the vertical stability of pelvis,In three ligament,ASIL maintain pelvic stability is strongest,followed by SSL,and STL the weakest role.Part 4:The differentiation of anteroposterior compression type I from type II pelvic ring injuries and its evaluation of the extent of ligament injuriesObjective:To investigate the reliability of using the diastasis of 2.5 cm in pubic symphysis(PS)and sacroiliac joint(SIJ)to differentiate anteroposterior compression(APC)injuries type I from II damage and assess the extent of ligament injuriesMethods:Test models of APC type pelvic ring injuries were created in 11 fresh cadaver pelves(7 males and 4 females,22 hemipelvis in total).The hemipelvis,that were devided into 2 equal groups(n=11),were fixed to a table in one group(constrained group)and were not in the other group(unconstrained group).External rotation of the hemipelvis was applied to cadaveric human pelves with the hemipelvis either unconstrained or constrained to move only in the plane of rotation.We recorded displacement of the PS,SIJ and injury and disruption of sacrotubemus/sacrospinous ligament complex(STL/SSL)in each group that corresponded with failure of the anterior sacroiliac ligaments(ASIL).Results:The PS and SIJ average diastasis of the original pelvis were respectively 4.73±0.84mm,3.16±0.38mm.Average PS and SIJ diastasis at the point of ASIL failure were respectively 23.36±7.27mm(n = 22;range,12-41 mm),9.82±3.25mm(n＝22;range,5-18 mm).There were both significant differences of sexs(P<0.05)between PS and SIJ diastasis at the point of ASIL failure,but without significant differences between the constrained and unconstrained groups(P>0.05).The sample size of the separation distance of PS and SIJ were both 10(45.5%)beyoud 23.36mm or 9.82 mm.In addition,the sample size that at least one of the PS and SIJ diastasis was beyond of 23.36 mm or 9.82mm was 15(68.2%).Conclusions:Regarding the existing of significant morphologic variation,2.5 cm of symphysis pubis diastasis may be taken as an approximately averages,but not a valid differentiation point between anteroposterior compression Ⅰ and Ⅱ injuries.Clinically,the degree of pelvic injuries is always underestimated,and the comprehensive evaluation is recommended based on different situation.The pubic symphysis combined with the anterior separation of the sacroiliac joint is more helpful to judge the degree of pelvic injuries.Part 5:Research progress on biomechanical characteristics of sacroiliac complex(A review)... |
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