| Objective:To discribe the anatomy of posterior column of ilium(PCI) and probe into the feasibility of lumboiliac fixation through the related measurement of ilium in the preserved adult human cadaver and biomechanics test of intensity of iliac rod fixation with Galveston technique, providing the viable method and theories support for clinical application. Data and method:Pelvic specimens:A total of 12 adult human preserved cadavera and 10 hemisectioned pelvises were harvested with intrinsic ligments and L4 below vetebra and disc intact, and the femoral heads were disarticulated, and 7 off-water ilium bone were obtained to measure.For observation of the morphologic characteristics and length of posterior iliac column(PCI), the morphologic characteristics of iliac tuberosity (IT), greater sciatic notch(GSN), arcuate line(AL) and the height of PCI which contain the iliac rod of Φ 6-7mm, we draw a line from superior edge of iliopubic tuberosity to the nearest point of auricular surface which is defined as Chiotic line section (CLS), which passes the AL and this section is the most wide of all sections, and we draw an another line parallel to the CLS called A line; for the safe of operation, this line section defined that its wideness is no less than 10mm. Through the precut, we comfirm the section located at the link line from the intersection of posterior gluteus line(PGL) andposterior iliac crest(PIS) posteriorly to the anterior inferior iliac spine(AIIS) anteriorly, the wideness of this section is 11.24mm, this section is called A line section(ALS). Whereafter we cut the bone from A line every other 4-5mm till the posterior superior iliac spine(PSIS).The related data is follow: ①The PCI length is refered to the distance from the posterior edge of acetabulum to PIC in the CLS and the wideness a is that of same section by way of ALo Height 1 is the distance from the GSN to the CLS , height 2 is the istance from the GSN to the ALS, aimed at observation how much space room which the iliac rod of 6-7mm diameter. ②distance A: from intersection of iliac crest and Chiotic line (CIS) to the tip of PSIS ; distance B: from CIS anterior branch of greater sciatic notch; distance C : from the tip of PSIS to the AIIS.③For observation the morphology of iliac tuberosity, we have to measure distance D(from the tip of PSIS to the inner edge of ilium) and distance E(from the tip of PSIS to the crossing of posterior gluteus line and posterior iliac crest ); meanwhile the follow data is harvested: wideness b is that of posterior edge of sacroiliac joint in the Chiotic line section, wideness c is that of iliac tuberosity, wideness d is that of inner edge of ilium. ④to measure the thickness of medial and lateral cortical bone in the iliac tuberosity and that of greater sciatic notch(lateral) and arcuate line (medial). ⑤three entry point were employed: first is the standard Allen' point(A),the second is at CIS(B),and the third is located at the crossing of posterior gluteus line and posterior iliac crest. To measure the angles of the three entrypoint between sagittal plane and frontal plane respectively. ⑥To measure the distance from PSIS to the Pivot joint(that is: the central point of lumbar disc of L5/S1) in the 10 half pelvises (F) .CT and C-R measurement:Computed tomography measurements and Computed radiography measurements included the followings:①make sure the location of iliac rod, and the thickness of iliac tuberosity and the ilium-sagittal angle(∠ISA) were measured, ②the length(G) and the thickness(H) ( each scan layer thickness is 5 mm, filling up all related layers)were measured, ?with the CT and C-R films, angles between three needles and line of spinous process were measured in the 10 half pelvises. ? to measure the length of entrypoint B and anterior branch of greater sciatic notch, ?to measure the vertical distance between greater sciatic notch and the second needle in the C-R radiographs, that is the utmost height which the iliac rod were engaged, ?to measure the distance between greater sciatic notch and the second needle in the CT roentgenograph (M) and the width of this portion(W), ?to measure the angle between iliac rod and the base of sacrum oBiomechanic testFour pedicle screws in the L4,5 vertabral pedicle were tweaked according to Roy-Camile' method. From the entrypiont B(CIS point), iliac rod were embedded depending upon the Author' method,with the direction to acetabulum and the diameter of rod is 6.0 turn. The iliac rod were prebended into a model'shape, and then the rod were inserted and link to the pedicle screws, ultimately the transverse link device were installed and fixed tightly. The iliac rod have two curves and one transition length oAll biomechanical testing was performed on a CSS-2201 biomechanics test machine (made in graduate school of experimental machine, Changchun), the experimental criterion GB228-87 was adopted to test the maximal compress force(Fbc) and maximal tensile force(Fc)o When the compress test was to implement,the pedicle screws were unlink to the iliac rod and two cross-link devices were used to connected the rod sections with a metal pad of 4.5mm thick as a compress shank contact point, while the tensile test was to do, the iliac rod were linked to the L5 pedicle screws and two cross-link devices were used to connected the rod sections and then link to the test machine oAll the data was to analyze with SAS statistics soft ware according to different conditions, significant differences were tested.ResultThe PCI average length is 110.57 mm, the width is 24.24 mm, the height between the greater sciatic notch and arcuate line is 14.54 nun. The narrowest portion in all of sections is located at the posterior edge of sacroiliac joint and its wideness is 14.39 mm; the wideness of iliac tuberosity at the crossing of posterior iliac crest and Chiotic line is 21.54 mm.and its width is the most thick in all of sections of iliac tuberosity; the width of inner edge of ilium is 20.35mm and it is the second most thick part, and it is in the peak of second curve of ilium; the distance between greater sciatic notch and Aline section is 31.46 mm, it shows that there was 3 cm space room containing the iliac rod of 6-7mm diameter.The distance between the CIS and tip of PSIS is 23.94 mm anteriorly, and that of CIS to the greater sciatic notch is 85.43 mm, and that of CIS to AIIS is the longest distance 142.60mm, the length of posteior iliac crest or length of iliac tuberosity is 61.39mmo The distance between the tip of PSIS and the crossing of posterior gluteus line and posterior iliac crest is 46.63 mm, the portion of CIS to above the crossing is ideal entrypoint part(4.6-2.4=2.2cm), of which the CIS is the optimal ? The distance of PSIS to Pivot point is 53.80mm, from this point of view, if the length of iliac rod is long enough than this distance over the sagittal plane, the strength is enough to embrace the rod tightly and fixation is stabilization, just as the pedicle screws penetrate three columns of spine, it act as powerful sustainence force oThe cortical bone thickness of greater sciatic notch(GSN) is 3.43 mm(maximal thickness is 4.5mm), and that of arcuate line(AL) is 3.34 mm(maximal thickness is 4.22mm); the thickness of inner cortical bone at the iliac tuberosity(IT) is 1.22mm(maximal thickness is 1.48mm) ,and that of extra cortical bone is 1.85mm(maximal thickness is 2.28mm ) ,it indicates that the cortial bone of the portion of greater sciatic notch and arcuate line are special thick, it is an area that the trabeculae concentrated which was demonstrated in the photographs of CT and C-R, as an arch bridge in conjunction with front ilum and back ilunio Its frontal sections shows ( CT scans and cutting sections )that this portion is delineated an triangle with opening upwards. Thedistance of greater sciatic notch to second pin is 3.03cm, the numericial value on CT scan have two: the height of filling-up of layers is 3.25cm, while that of coronal scans is 3.06 cm, this three data make no significant difference, which reveals that the three methods were adopted and beneficial to preoperative plan especially for the C-R radiographs. The length of second needle to front branch of greater sciatic notch is average 8.2 cm, which is useful at confirming the length of iliac rod while operation.,Of all three different entrypoint, the sagittal angle of A point is 19.5 ° and the coronal angle of it is 63.66° , namely its horizontial angle is 26° or so; the sagittal angle of B point is 25.66° and the coronal angle of it is 48.33° ,namely its horizontial angle is 42° ; the sagittal angle ofC point is 33.83° and its coronal angle is31 ° ,namely its horizontial angle is 59° <> TheZISA on the CT scan is 22.16 ° , there is no significant difference between sagittal angle of B point and Z IS A o Parallelling the horizontial angle of B point with 30° > 45° and 50° ,we found that three was no significant difference between the horizontial angle of B point and 45 ° ; the angle between B point and tilting of sacrum is 2.16 ° ,it shows that the incline angle of sacrum is in parallel with the sagittal angle of B point oThe whole length of ilium on CT scan is 14.40 cm, the section width above the greater sciatic notch is2.26cm; the thickness of iliac tuberosity is 2.0cm-, the wideness of posterior edge of sacroiliac joint is 1.53cmo In comparison to that of specimen respectively, there are no significant difference among them0 It displays that three different methods are identical in measurmentoThe bending angle of iliac rod is an important reference data, it determine if the iliac rod can be inserted and connected to the pedicle screws successfully or noU Its bending curve at the sacrum is 99.66° and its bending curve at the ilium is 50° ,the valgus angle is 33.16° ,the migration distance between two bending is 2.0cmoThe result of biomechanic test shows that PCI can sustain 2683N maximumly and 619N leastly, the average compress force is 1927.33N; and meanwhile it can withstand the highest strain of 198IN and lowest strain of 789N, and on average ,it can bear 1334.67N strain forceo In the process of test ,there were no instrumentationfailure.ConclusionAccording to our observation, the PCI seem resemble a trapezoid with a center of Chiotic lineo The posterior iliac crest is its posterosuperior border and its length is 6cm, its anteroinferior border is located at posterior edge of acetabulum and its length can be deemed to the height of PCI(3cm), its inferior border is 8.2cm, its superior border is equal to PCI and its length is 11 cm- PCI is a bearing bone of back part of ilium and thus it gets special thickness.Iliac tuberosity(IT) is a unregular quadrangle located behind ilium, posterior iliac crest is its back edge, iliac rod penetrates iliac tuberosity(IT^ auricular surface(AS) in turn and then entry into the triangle region enclosed by greater sciatic notch (GSN) and arcuate line(AL)until the posterior superior edge of acetabulum o There was a sunken behind AS, from anterior superior part to posterior inferior part, this sunken is gradually deepen and it get more and more thin under Chiotic line,. In level with the fro-GSN, the thickness is not enough thick to contain a iliac rod, and therefore PSIS is unsuitable /improper for implanting iliac rodoGSN and AL possess the thickest cortical bone in PCI located in lateral (3.43mm) and medial region (3.34mm), just as the pedicle screws link the vertebral body and accessories, GSN and AL act as an arch bridge linking the front and back ilium o Compressive stress osteo-trabeculae focus on the posterosuperior edge of acetabulum getting along with tensile stress osteo-trabeculae of tubercle of iliac crest(TIC), they constitutes the loading portion of acetabulum together, the latter portion related to TIC is a part of anterior column of acetabulum delineated by Letornnel, hence it is called anterior column of ilium(ACI)<> On the top of the GSN, there is 3 cm space room containing iliac rod of 6-7mm diameter <>The entrypoint B is optimial of all three options, one the one hand its entry direction is in line with that of osteo-trabeculae and parallel to that of sacral tilting, on... |
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