| BackgroundUp to now, the treatment of acetabulur fractures is still a problem for orthopedic surgeons. Acetabulum is deep in body with complicated anatomic structures, and adjacents to the pelvic visceras and important nerve, and blood vessels.Trauma and surgery will cause threat to patients. More conservative treatments were chose for pelvic acetabulum fractures half- a-century ago, because of insufficient understanding of the acetabulur fractures and the lack of technology. But as the improvement of internal fixation techniques, Judet and Letournel,in 1964, advocated that acetabulur fractures should be treatment in accordance with the principle of the treatment of intra-articular fractures of lower limbs:Open reduction and internal fixation for all the displaced acetabulur fracture. Cases of the acetabulur fractures treated with surgery were summarized by Tile. He found that 75.2% of the cases had good efficacy,8.3% were acceptable,16.5% were poor. For 90% of the cases with anatomical reduction, the clinical effect was satisfied, but for the cases with poor reduction, the clinical effect was unsatisfied. So the clinical effect of acetabulur fractures are closely related with the fracture type and the result of the reduction.At present, the orthopedic surgeons have accepted the basic therapeutic principles of acetabulur fractures:anatomical reduction, firm fixation and early functional exercise. After years of exploration, many issues were solved well,such as the safe and effective approaches, methods for reduction, and the decrease of the incidence of complications. But clinical effect were poor in 20% of the patients with acetabulur fractures. In order to reduce the surgical trauma and decrease the incidence of surgical complications, a lot of work were did. Minimally incision or closed reduction-percutaneous screw fixation are advocated for the acetabulur fractures, if the effect of the reduction and fixation is not reduced. The fixation with percutaneous lag screw or a single incision with lag screw become popular treatment for posterior column fractures. For pure column fracture with no displacement or displacement less than 2 mm, closed reduction and percutaneous screw fixation is the the basic method. For the column fractures of associated fractures, a single incision is usually chose if the effect of the reduction and fixation is not reduced. If the anterior column or anterior wall fractures need open reduction and internal fixation, plate or screw would be used for the anterior column or anterior wall with the anterior approach, while the anterograde lag screw would be chose for the posterior column with the same approach.Due to the irregular column, "Osseous pathways" are relatively narrow, and screw is easy to stab the cortex of the posterior column, which would lead to organs injury or hip joint injury or sciatic nerve injury. Pierannunzii proposed that the nail point of the anterograde lag screw was 1centirmeter from the front of the sacroiliac joint,and 2.5 centimeters from pelvic brim; and the angle was toward the middle point of the ischial spine and the edge of obturator. Although screw navigation technique has been applied in guiding screw implanting. But due to reasons, such as its expensive, this technique is failed to used popularily. For most hospital, assessment of screw is perform with C-arm X-ray machine. In the supine position, posterior Lag screw is assessed with three radiographic views:anteroposterior, iliac oblique and obturator oblique view. When anterograde lag screw is implanted in the posterior column, attention should be pay to judge whether screw is in joints or out of column with sciatic nerve injury. Literature reported that incidence of iatrogenic sciatic nerve injury is 2%～6% in postoperative patients with acetabular fractures. Though a single incision can reduce surgical trauma, but incidence of sciatic nerve injury is not significantly reduced with single anterior approach. As Haidukewych reported, the incidence of iatrogenic sciatic nerve injury was 5.6%. But it was as high as 6.5% in patients with ilioinguinal approach. In Shazar’s reasearch, it was 4.1% with anterior approaches(ilioinguinal or Stoppa approach). Researches have proposed intraoperative monitoring can reduce incidence of iatrogenic sciatic nerve injury. But Haidukewych’s opinion was opposite:intraoperative monitoring did not reduce the incidence of iatrogenic sciatic nerve injury.In conclusion, assessment of screw position when implanting is very important. Much literature proposed that if the screw was in the shadow of posterior column in all three views (anteroposterior, iliac oblique and obturator oblique view), it could be think that the screw was in the posterior column. We suspect this opinion and hypothesise that there is a "shadow area" behind posterior column when assess lag screw with anteroposterior view, iliac oblique and obturator oblique view. Sciatic nerve may be injured if screw is in the "shadow area", but we can’t realized. If "shadow area" is existing, new method of assessment of screw will be explored.Objective1、This study discover and measure the "shadow area" in three fluoroscopic views on the standard supine position.2、To observe positional relation between the sciatic nerve and the "shadow area", and explore the cause of the sciatic nerve injury.3、To explore whether the landmarks of the three views can be used to assess the position of the landmark.4、To explore whether the position of screw can be assessed by the landmarks if the angle of the obturator oblique view is adjusted.Part ⅠMethodsThis study was carried out with the axial view of the magnetic resonance imaging of twenty right and left pelvis of ten adult males(24-67 years, mean 36 years). The parameters were measured on the plane of the apex of the ischial spine(P1) and the plane five millimeters above P1(P2). Five lines were used to simulate the fluoroscopy with three views (anteroposterior, iliac oblique and obturator oblique view). Line 2 and line 3 intersected with the posterior aspect of the posterior column at point A and B, respectively. Line 1 intersected with line 2 and line 3 at point D and C, respectively. Point E was the midpoint of CD. EF was perpendicular to CD, and intersected with the posterior aspect of the posterior column at point F. On Plane PI and P2, the lengths of AD(al, a2) and EF(bl, b2) and the shortest distance between the front edge of the sciatic nerve and the posterior column were measured (L1, L2). Last, the position of the sciatic nerve relative to the quadrilateral "ABCD"was surveyed.ReasultsThe shape of the "shadow area" is akin to a right-angled trapezoid. The parameters of the "shadow area" is as follows:a1= (11.62±2.29) mm, b1= (9.24±1.64) mm;a2=(13.63±1.85) mm, b2=(9.01±1.94) mm.. The distance between the nerve and the posterior column is as follows:L1= (7.42±1.90) mm, L2= (5.83±1.93) mm. On plane P1,85% of the sciatic nerve is in the "shadow area"(40% for R1,45% for junctional zone of R1 and R2); just 15% is out of the "shadow area". On plane P2,85% of the sciatic nerve is in the R1 region; just 15% is out of the "shadow area".Part ⅠMethods1.MaterialSpecimen:three fresh frozen or preservative adult male pelvis,supplied by the department of anatomy of southern medical university, were used in this study(complete osseous pelvic with pelvic ligament and lumbar 4/5). All the pelvis was confirmed well, by gross appearance and X-ray, without disease such as fracture, tumor, rheumatism disease or tuberculosis anatomical variations. Experimental apparatus:Orthopedic operating table, C-arm X-ray machine(Germany, Ziehm), Low-speed electric drill, several kirschner wires (Ω1.0 mm), cannulated screws(Ω6.5 mm, L 110 mm and 90 mm, Watson, China).2.Model formationModel with screw located at posterior column:Screws were guided by kirschner wire. The nail point was near the sacroiliac joint and the pelvic brim, and the angle was toward the ischial tuberosity. If the position of wire was well, then placed the screw into posterior column.Model with screw stabbed out of posterior column and into the "shadow area": Screws were also guided by kirschner wire. The nail point was near the sacroiliac joint and the pelvic brim, and the angle was toward the ischial tuberosity. The wire weared out of the back of the posterior column at the position about 20 mm above the ischial spine. Long screws (L110 mm) weared out of column and then into the ischial ramus again, while short screws (L90mm)weared out of column with 15 mm, but did not wear into the ischial ramus again. All models were checked and the position of the screws were assessed with fluoroscopy with three views: anteroposterior view, iliac and obturator oblique view. All screws were proved that they were in the outline of the posterior column.3.Methods of fluoroscopy:Posture of the pelvis:All pelvis were placed on orthopaedic operating table with standard anatomical position. The posture was confirmed by fluoroscopy with anteroposterior view and lateral view.Definition of the views of fluoroscopy is provided as following. Anteroposterior view:The posture of the pelvis were standard anatomical position, and the tube exposured the acetabulum anteroposteriorly. Iliac oblique view:The posture of the pelvis were standard anatomical position, and the tube was rotated toward the another side by 45°. Obturator oblique view:The posture of the pelvis were standard anatomical position, and the tube was rotated toward the same side by 45°.4.fluoroscopic test:Six acetabulum of the three pelvis were testet respectively with four tests as following:with no screws,wiht long screws well in posterior column,with long screws out of posterior and into "shadow area", with Short screws out of posterior and into "shadow area". The following projection was carried out in all tests: anteroposterior view, iliac oblique view, obturator oblique view, obturator oblique+ 5 °view, obturator oblique+ 10°view, obturator oblique+ 15°view, obturator oblique+ 20°view.5.Radiographic assessmentAll images were assessed by two intermediate or senior orthopedic surgeons, Respectively, who work on research of pelvic and acetabulum. Content for Assessment:The fluoroscopic views are standard or not, the landmark of the acetabulum in fluoroscopic views, the position of screws, reationship of screw and landmarks.Results1. Landmarks of the acetabulum on three fluoroscopic viewsLandmarks can be found on three fluoroscopic views. In anteroposterior view, five distinct landmarks can be seen around the socket:iliopectineal line, anterior lip of the socket, posterior lip of the socket, ilioischial line,superior segment of articular surface. In iliac oblique view, four distinct landmarks can be seen:ilioischial line, superior segment of articular surface, posterior lip of the socket, anterior lip of the socket. Five landmarks can be seen in obturator oblique view:iliopectineal line, anterior lip of the socket, posterior lip of the socket, posterior line of the back wall, ilioischial line. The ilioischial line is visible near the ischial spine, and it crosses the upside and bottom of the posterior lip. The landmarks, as above, can be seen on all six hemipelves. Visualization of all the landmarks are fuzzy or clear.2、assessment of the screwBy observing the three views of the model with screw located at posterior column, some other features can be found, not only the screw is located at the outline of posterior. In anteroposterior view, screw goes across the socket and is lateral to ilioischial line. Screw is between the superior segment of articular surface and the ilioischial line in iliac oblique view. In obturator oblique view, screw is anteromedial to the acetabular segment of the ilioischial line.By observing the three views of the model with screw stabbed out of posterior column and into the "shadow area", some other features can be found, although the screw is located at the outline of posterior. The position of the screw is relative to the landmarks. In anteroposterior view, screw is more medial than that placed well into the posterior column and closer to ilioischial line. In iliac oblique view, screw is more medial and postrerior, and also closer to ilioischial line. In obturator oblique view, screw is outside the the acetabular segment of the ilioischial line.3、The features of the the adjustive obturator oblique viewsIn obturator oblique view, the order of the three landmarks, posterior line of the back wall, posterior lip of the socket and ilioischial line, is back-to-front. They cross each other at the bottom of the posterior lip, the ilioischial line crosses upside of posterior lip of the socket. In the obturator oblique+5°view, the order of the three landmarks, posterior line of the back wall, posterior lip of the socket and ilioischial line, is back-to-front, too. But the distance between the posterior lip of the socket and ilioischial line shorten, while the distance between the posterior line of the back wall and posterior lip of the socket prolong. In the obturator oblique+10°view, ilioischial line overlaps posterior lip of the socket. In the obturator oblique+ 15°view, the order of the three landmarks, posterior line of the back wall, ilioischial line, and posterior lip of the socket, is back-to-front. In the obturator oblique+ 20°, the posterior line of the back wall overlaps ilioischial line,and the posterior lip of the socket is anteromedial to the two landmarks.In the obturator oblique+ 10°view of the model with screw located at posterior column, screw is anterior to the overlap between ilioischial line and posterior lip.Screw, of which model with screw stabbed out of posterior column and into the "shadow area", is in the outline of the posterior column in three views. But In the obturator oblique view, screw is is posterior to the ilioischial line. In the obturator oblique+ 10°view, all the part of the screw that is out of the posterior column is posterior to the overlap almost. For the model with short screw stabbed out of posterior column and into the "shadow area", some part of the screw out of the posterior column is also posterior to the overlap in the obturator oblique+ 15°view, but less than 15 mm.Conclusion1. "Shadow area" will be formed behind the adult male acetabular posterior column while the radiographic images of the anteroposterior, iliac oblique and obturator oblique views are used, although the screw is in the outline of the posterior in three views.2. Short distance is found between the sciatic nerve and the posterior column, and the sciatic nerve is often located in the "shadow area".3. This reminds us that the sciatic nerve would be injured when the antegrade lag screw pierce out of the posterior column and in to the "shadow area".4. The position of the screw can be assessed according to the landmarks in three views. If the position of the screw is well in the anteroposterior and iliac oblique views, the positon of the screw can be assessed in the obturator oblique view:If the screw is anteromedial to the ilioischial line, it can be ensured that the screw is placed well in the posterior column.5. If the position of the screw is well in the anteroposterior and iliac oblique views, the positon of the screw can be assessed in the obturator oblique+10°view:If the screw is anteromedial to the overlap of the ilioischial line and posterior lip, it can be ensured that the screw is placed well. |
PDF Full Text Request