| BackgroundFemale pelvic floor dysfunction mainly includes pelvic organ prolapse,stress urinary incontinence,sexual dysfunction and fecal incontinence. Pelvic organ prolapse are major health and quality of life problem of women in the reproductive and menopausal years. Our country is a populous country. The prevalence of pelvic organ prolapse is increasing with aging from the second half of the 20th century onwards, which becomes to be a great life and psychological distress to the patients and the heavy burden to the patients family and to the society. Laparoscopic sacrocolpopexy is another alternative surgery treatment of pelvic organ prolapse with a high success rate,low recurrence rate and surgical trauma,less erosion and blood loss,faster postoperative recovery,less influence to the quality of sexual life.Great blood loss of the presacral space that difficult to control and even lead to life-threatening bleeding is the most severity intraoperative complication of laparoscopic sacrocolpopexy,due to the rich and great various blood vessels of presacral space. But how to prevent great blood loss of the presacral space intraoperative and erosion of the mesh postoperative?Where is the reasonable fixed position on the sacrum of the mesh? It's argued at present and prevented this operation carrying out widespread. So the safety of laparoscopic sacrocolpopexy is most important. However,there are few reports at home and abroad about the safety of this operation. ObjectiveBy studying on the anatomic structure of presacral space of the adult female cadavers,which fixed with formaldehyde after injection of different color resin into the inferior vena cava and iliac artery,the aim of our research was to determine a safe zone in the anterior aspect of the sacrum in order to lower the occurrence of such injuries during laparoscopic sacrocolpopexy and to supply applied anatomical data for the safety of it. At the same time,in vitro biomechanical test was performing on difference segments of the adult female cadavers anterior longitudinal ligament of sacral vertebrae,to understand its biological and mechanical properties,obtain biomechanical parameters. The aim of our research was to supply biomechanical data for laparoscopic sacrocolpopexy. Further more,provided mechanics basis for the reasonable fixed position on the sacrum of the mesh.Methods1. Dissection was performed on 18 adult female cadavers fixed with 10% formaldehyde,which were injected different color resin into the inferior vena cava and iliac artery that succeeded on 16 specimens. All of the specimens'perineum and pelvic organ were no absence,no abnormalities,no manifest of pelvic organ prolapse. Observe the composition of presacral space,and measure the presacral space and the distance around the main structure. 2. 16 pieces of anterior longitudinal ligament of sacral vertebrae which were took from the cadavers of part one,were trimmed for the S1 segment (16 cases), S2 segment (16 cases) and S3~5 segment (16 cases) ,with the standard sample of growth 20 mm and width 10 mm. After measuring the thickness of the specimens with the digital calipers,the specimens were placed into the testing machine after the pre-set to deal with the tensile test. Obtain biomechanical data of female cadavers anterior longitudinal ligament of sacral vertebrae.Result1. From S1 to S5, the height of sacral vertebral, distance of anterior sacral foramina as well as the distance of presacral transverse veins was declining(P<0.05). And the size of avascularity decrease progressively too.2. The location of the median sacral vessels were great various.43.75% went through the midpoint of sacral promontory;37.5% in the left while 18.75% in the right. When the median sacral vessels walked on the surfaces of sacrum under sacral promontory, 12.5% went through the midline,31.25% on the left of the midline while 56.25% on the right. Meanwhile,the outside diameter of the median sacral vessels were small in usual:the median sacral artery(1.89±0.45)mm and the median sacral veins were(1.76±0.59)mm.3. The location of the first transverse veins were great various.The type of variation occupies 26.67%. The vertical distance between the first transverse veins of variant and the midpoint of sacral promontory was 7.26 mm on average;And the normal ones constituted 73.33%. However,the vertical distance between the first transverse veins of normal and the midpoint of sacral promontory was 31.09 mm on average.4. There were differences in the distance between the median sacral vessels and anterior sacral foramina as a result of its variation of location. The horizontal distance of Type 1 median sacral vessels (through the midline or left of the midline) among the first to fourth anterior sacral foramina inner edge on the left were(12.21±3.88)mm, (9.73±5.58)mm,(9.16±3.97)mm and(9.39±3.66)mm respectively. The differences between levels are not significan(tP>0.05).However,the horizontal distance between them on the right were(19.48±4.00)mm,(17.13±5.17)mm,(15.84±5.61)mm and(12.28±2.00)mm respectively,which was declining(P<0.05). The horizontal distance of Type 2 median sacral vessels (on the right of the midline) among the first to fourth anterior sacral foramina inner edge on the left were(19.91±2.50)mm,(18.37±1.22)mm,(16.28±2.65)and(16.15±3.16)mm respectively, which was declining(P<0.05). On the other hand,the horizontal distance between them on the right were(10.31±2.46)mm,( 4.90±3.36)mm,(6.10±4.40) and (9.60±4.23)mm respectively,the differences between levels were not significant (P>0.05).5. The vessels closest to the midian sacral vessels were different in the different reference levels:(1) At the level of the sacral promontory,the vessels which closest to the midian sacral vessels(type 1 )on the left-hand was the left common iliac vein (18.25±11.36 mm),the right-hand was the right internal iliac vein (26.66±7.18 mm);whilh the vessels closest to the type 2 midian sacral vessels in the left-hand was the left common iliac vein (24.92±9.59 mm),the right-hand is the right internal iliac artery (19.53±4.94 mm). The difference was significant(P <0.05).(2) At the level of the first anterior sacral foramina,the vessels which closest to the midian sacral vessels(type 1 )on the left-hand was the left common iliac vein (24.57±11.91 mm),the right-hand is the right internal iliac vein (28.52±4.54 mm);whilh the vessels closest to the type 2 midian sacral vessels in the left-hand was the left internal iliac vein (37.52±8.71),the right-hand was the right internal iliac vein (26.71±19.56 mm). The difference is significant(P <0.05).(3) From the second to fourth anterior sacral foramina level,the paravertebral venous and the lateral sacral artery are the nearest vessels to the type 1 or type 2 midian sacral vessels. The difference is significant(P <0.05).6. The thickness of anterior longitudinal ligament was different in different segments. The thickness of S1 segment,S2 segment,S3～5 segment respectively were:(0.59±0.12) mm,(0.37±0.08) mm and (0.22±0.04) mm. It was declining which was a significant difference( P <0.05).7. The maximum load of the S1,S2 ,S3～5 anterior longitudinal ligament, respectively were (38.59±4.65) N,(22.74±5.21) N and (11.30±2.99) N; the stress respectively were (30.27±2.71) MPa,(20.02±1.25) MPa and (16.69±2.34) MPa;and the modulus of elasticity respectively were (60.32±7.56),(30.08±5.89) and (20.11±6.72).3 groups had no significant difference in the strain difference(P > 0.05);The maximum load,the stress and the modulus of elasticity were decreasing(P <0.05), there was a significant difference.It was suggested that the strength and stiffness of the sacral anterior longitudinal ligament gradually became weaker and weaker from S1 to S5.ConclusionIn this study, we find out that:(一) The anatomy structure of presacral space is complex.The rich and great various blood vessels of presacral space are the main reasons of great blood loss during laparoscopic sacrocolpopexy. (二) The presacral space of S1 has the largest avascular zone,which is the relatively safe area of fixation position for laparoscopic sacrocolpopexy. The relative safety area is a rectangle which upper bound is 10mm under promontorium sacri and lower bound is 40mm under promontorium sacri with 15mm in width. The rectangle is 30×15mm.Consider the middle sacral vessels as the reference point,when the middle sacral vessels locate in middle or variates to left,the rectangle locates in the right side of the middle sacral vessels. However,when the middle sacral vessels variates to right,the rectangle locates in the left side of the middle sacral vessels.(三) The large blood vessels closest to the presacral space of S1 is the right internal iliac vein that should be avoided injury intraoperative.(四) The anterior longitudinal ligament of sacral vertebrae of S1 segment is the thickest, with the greatest strength and stiffness.It is the best reasonable fixation position for laparoscopic sacrocolpopexy that can provide stronger fixation strength and stiffness.
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