| Objective: The treatment of pelvic trauma has made great progress in recent years, open reduction and internal fixation (ORIF) has become an important therapeutic tool of pelvic fractures and acetabular fractures, sometimes serious complication occurs during internal fixation of the fractured fragment, such as screw penetrating the joint surface, injuring important blood vessel and nerve. So it is basis and key of preventing blood vessel and nerve from accidental injury to comprehend the depth of whole pelvis, the distance of important blood vessel and nerve to bone wall, and their projection on pelvis surface.There is no report of the depth of whole pelvis at present, so we establish a coordinate system on the outer and inner surface of the pelvis respectively, measure the depth of all points of the coordinate system, draw contour lines, and fill in different color between different contour lines respectively, thus it form several regions of different depth. Apart from the projection of external iliac a. v., obturator a. v. n., sacroiliac joint, lateral sacral mass and S2 pedicle, there is no report of the projection of other important structures of pelvic on the outer surface of the posterior ilium, so we draw the projection of the important structures of pelvis on the outer surface of the posterior ilium, thus it form the projection graph. We quote the concept of topography map in geography, draw coordinate system, contour lines and projection graph on pelvis simultaneously, and it form the topographic map of the inner and outer surface of pelvis respectively, express directly the depth of the whole pelvis, the projection position of the blood vessel and nerve, so the topography map iseasy to use and memory. It is of important instructive significance to avoid important blood vessel and nerve injury during ORIF operation of pelvic fractures and acetabular fractures.The internal fixation techniques of pelvic fractures and actebular fractures include iliosacral screw technique, sacroiliac joint anterior plate fixation technique, acetabular posterior column plate technique, acetabular posterior column lag screw technique, acetabular anterior column plate technique and acetabular anterior column lag screw technique et al. The prior four methods has been well documented, we do not repeat it any more, we concentrate mainly on acetabular anterior column plate technique and acetabular anterior column lag screw technique in the article.Serious complication of screw penetrating the joint surface may occur if using acetabular anterior column plate technique in single anterior approach, because we can not see the opposite joint surface. The Benedetti's study on the angle of inclination of screw is with respect to the vertical lines of anterior surface of anterior column, its reliability is poor, and moreover, the data is too much to memory. So we modify Benedetti's experiment, change reference standard of the angle of inclination of screw as quadrilateral plate, it would have a more reliable and practical conclusion, and we simplify the data, make it easy to memory and use clinically.Some doctors overseas have reported the lag screw placement in the anterior column one after another, but the entry point, the angle of inclination and mean length of the lag screw is different, so the technique is lack of unity and screw penetration of the acetabulum, important blood vessel and nerve injury may take place during operation. So the key of minimizing the complication above-mentioned is to choose the optimal entry point, angle of inclination and length of the lag screw through quantitative anatomic study. The quantitative anatomic documents about anterior column lag screw are few at present, and definition of entry point is too tedious and inconvenience. So we determine the entry point, the angle of inclination and the length of lag screw through new method, which make anterior column lag screw technique standardization, and minimize the complication relevant to internal fixationgreatly.Methods: The study can be divided into two parts, in part 1, we mainly draw the topographic map of the inner and outer surface of pelvis. In part 2, we mainly study the entry point, the angle of inclination and the mean length of lag screw in acetabular anterior column lag screw technique and acetabular anterior column plate technique.In the study of part 1, 5 cadaveric adult antiseptic specimens were prepared. Dissect pelvis and expose important blood vessel and nerve, observe its course, establish a coordinate system on the outer and inner surface of the pelvis, dill and measure the depth in every point of coordinate system. Draw the contour line of 5 mm, 10 mm, 15 mm and 20 mm on the inner and outer surface of the pelvis respectively, and fill in different color between the different contour line, thus it form several regions of different depth. Draw the projection of important blood vessel and nerve on the inner and outer surface of the pelvis respectively.In the study of part 2, 10 cadaveric adult antiseptic specimens were prepared. Determine anterior acetabular margin, posterior acetabular margin and the serial cross-sections of the acetabular anterior column, measure the distance from anterior acetabular margin and posterior acetabular margin to AIIS, iliopubic eminence and pubic tubercle respectively. Section anterior column with a fine-toothed hand saw, form cross-sections A, B, C, D, E and F.Acetabular anterior column lag screw techniques: In single screw technique, we define the penetrating point of the Kirschner wire on the posterolateral surface of the ilium as point O, summit of greater sciatic notch as point Q, draw parallel line of medial border of the posterior column at point O, draw vertical line of the parallel line at point Q, the vertical line and the parallel line intersect at point P, then measure the length of OP and PQ, and measure the length from point O to cross-section F. In double screw technique, we define the penetrating point of the Kirschner wire on the posterolateral surface of the ilium as point 01 and point 02 respectively, draw parallel line of medial border of the posterior column at point Ol and point 02 respectively, draw 2 vertical lines of the 2 parallel lines at point Q, the 2 vertical linesand the corresponding parallel lines intersect at point PI and point P2 respectively, then measure the length of O1P1, O2P2, P1Q and P2Q, and measure the length from point 01 and point 02 to cross-section E (anterior margin plane of acetabulum) respectively.Acetabular anterior column plate technique: Draw the contour line of each cross-section, then a distance measuring 0.5 cm from and parallel to the bony acetabular medial boundary was determined and also marked on each cross-section, positions were then marked at distances of 0.5, 1.0, and 1.5 cm lateral to the pelvic brim on anterior surface of the anterior column on each cross-section. These points represented proposed entry points for cortical screw placement. The line connecting each of the 0.5 cm, 1.0 cm, and 1.5 cm entry points with the most medial projection tangent of the parallel lines relative to each entry point was established, the angulation created by this line with respect to the quadrilateral plate is the safe angle of screw entry. The distance from entry point to the penetrating point on quadrilateral plate is the length of screw; put all data into software SPSS 10.0 for statistics process.Results: Place mean of the depth of all points on coordinate system of inner and outer of pelvis in the nearest whole number, and mark the integer number on the coordinate system of the inner and outer surface of the pelvis. Draw the coordinate system, the contour line and the projection graph of important blood vessel and nerve on pelvis simultaneously, form three topography maps, one is topography map of inner surface of pelvis, one is topography map of outer surface of pelvis without blood vessel and nerve, the other is topography map of outer surface of pelvis with blood vessel and nerve.Acetabular anterior column lag screw technique: Single screw technique: thelength of OP is (23.5±2.2) mm, the length of PQ is (16.8±1.6) mm, the length of lagscrew is (84.9±4.7) mm. Double screw technique: the length of O1P1 is (26.3±2.3)mm, the length of P1Q is (13.6±1.4) mm, the length of medial lag screw is(69.8±4.1) mm, the length of O2P2 is (20.7±2.1) mm, the length of P2Q is(20.1±1.8) mm, the length of lateral lag screw is (61.2±3.7) mm.Acetabular anterior column plate technique: The anterior margin of the acetabulum region lies in 16 mm anterior to the projection of the center of iliopubic eminence onto the linea terminalis of pelvis, or 29 mm anterior to the projection of inferior margin of AIIS onto the linea terminalis of pelvis, or 37 mm posterior to the projection of pubic tubercle onto the linea terminalis of pelvis. The posterior margin of the acetabulum region lies in 25 mm posterior to the projection of the center of iliopubic eminence onto the linea terminalis of pelvis, or 12 mm posterior to the projection of inferior margin of AIIS onto the linea terminalis of pelvis. The shortest distance from 0.5 cm, 1.0 cm and 1.5 cm entry points to articular surface of acetabulum is (15.6±1.5) mm, (13.1±1.2) mm and (11.2± 1.4) mm respectively.The average entry angle of inclination in 0.5 cm entry point of cross-section B, C and D is 8.2°, 4.5° and —15.2° respectively, the average length of lag screw is 19.8 mm, 24.4 mm and 45.1 mm respectively. The average entry angle of inclination in 1.0 cm entry point of cross-section B, C and D is 14.9°, 13.2° and —7.4° respectively, the average length of lag screw is 23.3 mm, 27.5 mm and 46.5 mm respectively. The average entry angle of inclination in 1.5 cm entry point of cross-section B, C and D is 26.1°, 23.6° and 4.9° respectively, the average length of lag screw is 25.6 mm, 34.2 mm and 48.3 mm respectively.Conclusion: On iliac crest, plate can be used for internal fixation; plate can be placed on the inner surface, superior surface or outer surface of the iliac crest. On the inner table of ilium, you can drill and fix with screw on all regions except the region of depth less than 5 mm and the projection of the acetabulum, avoiding damaging upper and lower branch of superior gluteal nerve. On the outer table of ilium, you can drill and fix with screw on all regions except the region of depth less than 5 mm. Important blood vessel and nerve injury is possible when drill and fix with screw on the region from greater sciatic notch to 4 cm above greater sciatic notch. In the region, you must strictly control the depth of drill and lag screw, not penetrating the opposite cortex of the bone, the safety depth of the screw is 15 mm, no more than 20 mm is recommended. The depth of the anterior border of the ala of ilium from ASIS totubercle of iliac crest is more than 5 mm, and the region is straight relatively, you may entry the screw backward on the anterior border of the ala of ilium from ASIS to the inferior margin of AIIS.Topography map of the pelvis express the depth of all parts of the pelvis, the projection of important blood vessel and nerve onto the pelvis accurately and directly. To understand deeply the topography map of the pelvis may prevent vital blood vessel and nerve from accidental injury during the operation of internal fixation of pelvic fracture and acetabular fracture.Acetabular anterior column lag screw technique: The entry point of single screw technique lies in the summit of greater sciatic notch move outward 17 mm perpendicular to the medial margin of the posterior column, then move upward 24 mm parallel to the medial margin of the posterior column, the length of the screw is 85 mm. The entry point of medial screw in two screw technique lies in 14 mm perpendicular to the medial margin of the posterior column, and then move upward 26 mm parallel to the medial margin of the posterior column, the length of the screw is 70 mm. The entry point of lateral screw in two screw technique lies in 20 mm perpendicular to the medial margin of the posterior column, and then move upward 21 mm parallel to the medial margin of the posterior column, the length of the screw is 61 mm. The angle of lag screw with respect to the parallel line of the medial margin of the posterior column is 123°or so, the angle lag screw with respect to the vertical line of the medial margin of the posterior column is 62°or so. The position of the lag screw must be confined by intraoperative fluoroscopy in multiple projections.Acetabular anterior column plate technique: On anterior 1/4 region of the acetabulum, the entry point must be restricted in the scope of 0-1.5 cm outer of the linea terminalis of pelvis, the length of lag screw is 12-14 mm, the direction of lag screw is parallel to the quadrilateral plate. On anterior-middle 1/4 region, posterior-middle 1/4 region and posterior 1/4 region, the direction of the lag screw is perpendicular to the linea terminalis of the pelvis on sagittal plane; On coronal plane, with respect to quadrilateral plate, the angle of inclination of the lag screw are asfollows: on the region from the linea terminalis of pelvis to 0.5 cm lateral to the linea terminalis of pelvis, the entry angle of the screw is 0°-10°; On the region from 0.5 cm lateral to the linea terminalis of pelvis to 1.0 cm lateral to the linea terminalis of pelvis, the entry angle of screw is 10°-20°; On the region from 1.0 cm lateral to the linea terminalis of pelvis to 1.5 cm lateral to the linea terminalis of pelvis, the entry angle of screw is 20°-30°. The length of the lag screw can be determined according to depth-measuring result after drilling; it should be restricted in less than 50 mm.
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