| Pelvis and acetabulum are adjacent to many important nerves and vessels. Internal fixation by open reduction usually associated with long operation time, wide soft tissue exposed and more blood loss during operation. After operation, it is easily conducted heterotopic ossification, iatrogenic nerve and vascular injury and other complications. Therefore, in order to ensure the good reduction and rigid fixation of pelvic and acetabular fracture, how to effectively reduce the surgical trauma and operation time is a hot topic to research. With the development of biomechanics and anatomy study, medical imaging and computer assisted navigation, minimally invasive techniques are more popular for the treatment of pelvic and acetabular fractures. Minimally invasive surgery can effectively reduce the intraoperative bleeding and other complications caused by exposure. However, at the same time, due to the operation safe area is small, it can easily cause the damage of the surrounding organs and blood vessels when screws are implanted. So this kind of operation requires a high technology. The main difficulties are the correct interpretation for intraoperative fluoroscopy images accurately and the change of guide pin direction according to the images. In the minimally invasive treatment for superior ramus of pubis fractures and acetabular anterior column fracture commonly need obturator oblique view, outlet view, inlet view and outlet obturator view. The posterior column fracture needs iliac oblique view, outlet view and inlet view. The sacroiliac joint fracture and dislocation and sacral fracture need pelvic inlet view, outlet view, anteroposterior view and lateral pelvic view. All of views need to repeatedly exposure to the patients and doctors, and time-consuming. Therefore, the research on minimally invasive treatment of screw implantation of anterior column acetabular fractures, fracture of superior ramus of pubis, the posterior column fracture of acetabulum, the sacrum fracture and sacroiliac joint fracture and dislocation were studied. We put forward three new kinds of minimally invasive screw placement methods and a new method to determine the screw misplacement during operation. In the first part of this study, we proposed a new method to place screw for the acetabular anterior column fracture and the superior pubic ramus fracture. And its name is pubic ramus acetabular anterior column axial view. The validity of this method is confirmed by experiments on specimens. In the second part of this study, we put forward a new method to place screw for posterior column of acetabulum. And its name is the acetabular posterior column axial view. The validity of this method is confirmed by the experimental specimens of human body. In the third part of this study, the pelvic sacral wing “dengerous area” is studied and put forward a new method to avoid the sacroiliac screws into the sacral wing “dengerous area”, providing a reference for accurate placement of sacroiliac screws. In the fourth part of this study, we proposed a new method for accurate placement of sacroiliac screws using computer assisted thermoplastic elastomer film localization system method. Experiments by using model of pelvis preliminary confirmed the validity of this method. In the fifth part of this study, based on the experiment of computer assisted thermal plastic film system, the fixation of sacroiliac joint dislocation is used in clinical study. And the results further confirm its effectiveness and are conducive to the promotion for this method. Part 1 The application of the axial view of the anterior column for percutaneous screw placementObjective: To search for a new radiographic view/projection of the acetabular anterior column to provide a safe guide for percutaneous screw placement for acetabular fractures and pubic ramus fracure.Methods: Eight pelvic specimens taken from normal adult cadavers were positioned in a supine position on the operating table. First, the ipsilateral ilium-oblique view of the observed side was obtained on C-arm fluoroscopy by tilting the C-arm approximately 35° toward the contralateral hip joint. Then, the tilting angle of the C-arm was changed gradually until an oval track image(acetabular anterior column axial view) appeared. The oval shadow was clear only in one position as the angle of the C-arm was changed toward the caudal side of the operating table. A guide pin was put on the skin of the cadaver, and the location and tilting direction of the guide pin were adjusted under C-arm fluoroscopy until the pin’s shadow became a point in the center of the oval track. Then, the guide pin was inserted into the bone using a battery-powered drill. The degree of inclination of the guide pin in the cadaver in the frontal and sagittal planes was measured using computed tomography(CT).Results: In all eight pelves, the anterior column axial view of both sides was found successfully. All 16 guide pins were inserted through fluoroscopic guidance using the axial view and found to be well placed along the desired osseous route from the pubic superior ramus, across the iliopubic eminence, and into the iliac body. CT scans confirmed that the screws were in the safe zone, and no adjacent soft tissue or bone structures around hip joint were penetrated. On the CT-reconstructed image, the average angle between the guide pin and the sagittal plane was 33.6°(range: 29.6°–36.5°). The average angle between the guide pin and the transverse plane was 59.1°(range: 56.4°–63.2°).Conclusion: This axial view of the acetabular anterior column is a novel X-ray projection which provides an optimal method for guiding percutaneous insertion of anterior column screws for acetabular fractures. Insertion of the screw via this axial projection inside the oval track will prevent iatrogenic neurologic and vascular complications. Part 2 The application of the axial view of the posterior column for percutaneous screw placementObjective: To place the percutaneous screws of acetabular posterior column rapidly and safely, a readily reproducible radiographic anatomical clues of the acetabular posterior column for the percutaneous screw fixation was sought and delineated.Methods: Eight adult pelvic specimens prone positioned on the operating table and projected by X-ray machine from the ischial tuberosity to the posterior medial of ipsilateral acetabulum. The axial view of the posterior acetabular column which was oval or triangular image was found in different angles. When it was lucid, the distal posterior acetabular column were the most overlapping, which was the axial imaging signs of posterior acetabular column. It could clearly display cancellous bone channels within the posterior acetabular column.After the tube was fixed, the tip of guide wire was placed in the central of axial view of the posterior acetabular column. The guide wire was moved multi-directionally, until guide wire was entirely parallel with the X-ray projection direction and became an opaque point-like shadow. And then, along the guide wire direction, the guide wire was placed into the pelvis. After operation, the position of guide wire was observed by CT scan. In the CT reconstructed images, the diameter of narrowest part of acetabular posterior column was measured.Results: X-ray machine was placed with the pelvis specimen sagittal and transverse plane 16.6° and 62.1° respectively. The oval-shaped or triangular imaging sign was found. Through the vertical plane with the coronal observed in the bone with guide wire completely within the leading edge of posterior column, through the vertical plane with the sagittal plane did not observe the guide wire into the acetabulum. In the CT reconstructed image, the angle between the guide wire and the sagittal plane was 16.6°(9.6° to 28.5°). The angle between the guide wire and the transverse plane was 62.1°(67.4° to 55.4°).Conclusion: The acetabular posterior column axial view projection is a optimal radiographic technique for percutaneous placement of posterior column screws in clinical practice. The limpid axial view of acetabular posterior column can be got to applicate this project method, which provides a speedier method with less radiation exposure for percutaneous placement of acetabular posterior column screws. Part 3 The pelvic sacral wing “dengerous area” experimental study for accurate percutaneous sacroiliac screw insertionObjective: To evaluate the role of the inlet, outlet and lateral fluoroscopic views in optimising percutaneous sacroiliac screw insertion.Methods: In a simulated surgical procedure, 4 pelvic specimens were used. The insertion of 8 cannulated screws into the S1 vertebral bodies and perforated from the other side of sacral ala. Each pelvis was held with clamps and was placed supine on a radiolucent table. There was no attempt to create a dislocation and, therefore, this set-up resembled the condition of a sacroiliac joint dislocation after closed anatomical rduction. The perforation point was chosen as the middle point of the other side of sacral ala curve. In order to ensure the accurate placement, an aiming device was used. For the guidance and insertion of screw, a 2.5-mm guide wire was used. The perforation length was signed as 5 mm. After measure the length of the screw, a cannulated half threaded(6.5 mm) screw was inserted. The screw perforated from the middle point of opposite sacral ala curve. For standardisation and to avoid bias, all the screws were placed by the same experienced surgeon. All the procedures were performed in the operating theatre. The postoperative screws position was performed with visual examination, postoperative X-ray and computed tomography(CT). The postoperative X-rays of pelves were evaluated by two independent observers blinded to the trial. In the inlet X-ray view, the distance from the S1 anterior cortex to the screw tip(L1) and the distance from screw tip to the S1 posterior cortex(L2) were measured and recorded. And then, the ratio 1 that is the ratio of L1 and(L1 + L2) was calculated. In the outlet X-ray view, the distance from the S1 supe-rior endplate to the screw tip(L3) and the distance from screw tip to the superior border of S1 foramina(L4) were measured and recorded. And then, the ratio 2 that is the ratio of L3 and(L3 + L4) was calculated. All distance were measured for three times and ratio was determined and recorded.Results: In the X-ray inlet view, the screw tip was approximately located at the junction of the anterior 1/4 and posterior 3/4 of the sacral ala. In the outlet view, the screw tip was approximately located at the junction of the upper 1/5 and lower 4/5 of the sacral ala. In the lateral view, the screw was located at the posterior of the alar slope image.Conclusion: If the screw tip located in the anterior 1/4 of sacral ala on the inlet view and in the superior 1/5 of sacral ala on the outlet view, the screw tip possibly has already perforated the anterior cortex. It is important to properly adjust the direction of the screw or decrease the length of the screw for safe placement of the sacroiliac screw. Part 4 The application of a computer-assisted thermoplastic membrane navigation system in screw fixation of the sacroiliac joint experimental studyObjective: Unstable pelvic ring fractures with complete posterior ring disruption are serious injury and nonoperative treatment is not adequate to stabilize this kind of fracture. This study was designed to evaluate the effectiveness and accuracy of self-designed computer-assisted thermoplastic membrane navigation system versus conventional fluoroscopy technique in applying for screw fixation of sacroiliac joint dislocations. The hypothesis was that the computer-assisted thermoplastic membrane navigation system improved the accuracy of the screw positioning when correcting sacroiliac joint dislocations and the operating time would be reduced significantly.Methods: To ensure uniform testing materials, 16 polyurethane pelvic models of uniform size and composition were used to test the effectiveness of the conventional fluoroscopy techniques(control group) versus our selfdesigned navigation system(experimental group) in stabilizing sacroiliac joint dislocations. Identical C3 type sacroiliac joint dislocations were created and the models were randomly assigned with one of two guidance techniques. In each experimental group and control group, 32 cannulated screws were placed into the S1 vertebral bodies of 8 pelvic models. The pelvis in experimental group was placed in a prone position on the base plate of the location system. A size-specific thermoplastic membrane based on the size of the patient was selected and submerged into a sterile hot water tank. After the thermoplastic membrane softened, it was extracted from the water tank and immediately placed around on the pelvis. After the membrane was moulded with the pelvic contours, the two edges of the thermoplastic mould were locked on the base plate bilaterally. The pelvis was placed in between the mould and the base plate. The thermoplastic mould became hardened soon after the temperature dropped. The 3D laser location instrumentwas applied to select the standard plane for CT scanning, which was marked by three points on the mould. Three-millimetre fine-cut CT scanning was performed in the S1 and S2 vertebra regions. The CT data were collected and transferred to the treatment planning system, which automatically establishes a 3D model of the pelvis. The optimal screw trajectory of IS screw was designated as a line through the centre of the sacral 1 or sacral 2 pedicles and perpendicular to the IS joint. The screw trajectory was determined by two points, entry point and exit point, the screw trajectory across the thermoplastic membrane of the both sides. Depending on the marked plane, the spatial orientation data of entry point and exit point were calculated. The data were transferred to the 3D laser location instrument, through which entry point and exit point were located and marked on the thermoplastic mould. The length of the screw was also measured based on the CT images. The C-shaped aiming device was applied and adjusted until the tips of both the sleeves touched the entry and exit point marker of the mould, respectively. A 2.5-mm guide wire was placed into the IS joint under the guide of the C-shaped aiming device followed by insertion of a screw(6.5 mm) with the appropriate length. The pelvis in control group was prone on the operation table. The same surgeon performed the conventional method for screw placement using C-arm image intensifier to obtain inlet, outlet and lateral view of the pelvis. After operation, the inlet and outlet X-ray views and CT scan were performed to further measure and compare the screw positions. The radiation exposure time and operation time in between the onset of operation and the insertion of guide wire were recorded.Results: In control group, which applied with the conventional fluoroscopy technique, the average radiation exposure time was 41.1±15.2 seconds, and the average operation time was 382.9±93.7 seconds. 2 of 32 screws(6.3%) were misplaced. In comparison with the control group, the radiation exposure was totally avoided during operating, and the average operation time was 189.3±78.1 seconds in experimental group in which self-designed navigation system applied. All 32 screws were in the safe area. The difference regarding screw positioning between the preoperative plan and final screw position was 0.32±0.17 mm and 0.95±0.35 mm. The radiation exposure time during operating and operation time were reduced significantly when the experimental system was applied(P<0.05).Conclusion: Application of computer-assisted thermoplastic membrane navigation system for stabilizing sacroiliac joint dislocations has improved accuracy of screw positioning and the operating time was reduced significantly in contrast to the conventional fluoroscopic technique. The results of this prospectively controlled experimental study will need to be confirmed and studied by further clinical study. Part 5 The application of a computer-assisted thermoplastic membrane navigation system in screw fixation of the sacroiliac joint clinical studyObjective: The use of an iliosacral(IS) screw is the most popular method of stabilizing the posterior pelvic ring. However, percutaneous insertion remains challenging for orthopedic surgeons. We applied a computer assisted thermoplastic membrane navigation(CATMN) system for aide on the insertion of IS screws, a technique that is widely used for the accurate and repeatable location tumor in radiation therapy. We hypothesized that application of the CATMN system on IS screws’ insertion will provide a superior result to conventional fluoroscopic imaging with less operative time, radiation exposure and lower complication rates.Methods: We prospectively evaluated 26 consecutive patients who suffered from sacroiliac joint fractures and dislocations, treated at our hospital. Patients were randomized into two groups: 13 patients in the control and 13 patients in the CATMN groups. All patients were treated in a standardised fashion with initial resuscitation, followed by stabilisation with skeletal traction for rotationally and vertically unstable injuries. Patients with vertically unstable fracture dislocations were placed in femoral traction with a high weight. Anterior–posterior, inlet and outlet X-rays were performed to confirm the type of pelvic injury and reduction. The patient in CATMN group was placed in a prone position on the base plate of the location system. The operative area and thermoplastic mould are prepared in a sterile fashion. A size-specific thermoplastic membrane based on the size of the patient was selected and submerged into a sterile hot water tank. After the thermoplastic membrane softened, it was extracted from the water tank and immediately placed around on the patient’s pelvis. After the membrane was moulded with the pelvic contours, the two edges of the thermoplastic mould were locked on the base plate bilaterally. The patient was placed in between the mould and the base plate. The thermoplastic mould became hardened soon after the temperature dropped. The 3D laser location instrumentwas applied to select the standard plane for CT scanning, which was marked by three points on the mould. Three-millimetre fine-cut CT scanning was performed in the S1 and S2 vertebra regions. The CT data were collected and transferred to the treatment planning system, which automatically establishes a 3D model of the pelvis. The optimal screw trajectory of IS screw was designated as a line through the centre of the sacral 1 or sacral 2 pedicles and perpendicular to the IS joint. The screw trajectory was determined by two points, entry point and exit point, the screw trajectory across the skin of the both sides. Depending on the marked plane, the spatial orientation data of entry point and exit point were calculated. The data were transferred to the 3D laser location instrument, through which entry point and exit point were located and marked on the thermoplastic mould. The length of the screw was also measured based on the CT images. The C-shaped aiming device was applied and adjusted until the tips of both the sleeves touched the entry and exit point marker of the mould, respectively. A 2.5-mm guide wire was placed into the IS joint under the guide of the C-shaped aiming device followed by insertion of a screw(6.5 mm) with the appropriate length. The patient in control group was prone on the operation table. The same surgeon performed the conventional method for screw placement using C-arm image intensifier to obtain inlet, outlet and lateral view of the pelvis. After operation the inlet and outlet X-ray views and CT scanning were performed in the two groups to confirm and compare the screw positions. The operative time, blood loss, fluoroscopic times and radiation exposure and accuracy(measured with postoperative CT) were analyzed between groups.Results: In the control group: 18 screws were placed in 13 patients with conventional fluoroscopic technique, two of 18(11.1%) screws were misplaced. The average radiation exposure time was 37.5±6.4 seconds, intraoperative blood loss was 145.4±112.0 ml, and operation time was 619.2±199.5 seconds. In the CATMN group, 21 screws were placed in 13 patients with the application of the CATMN system. All 21 screws were in safe zones. The radiation exposure was zero, the average intraoperative blood loss was 46.2±24.3 ml and operation time was 353.8±111.2 seconds. Operative time was reduced significantly with the CATMN system(P<0.05).Conclusion: Application of computer-assisted thermoplastic membrane navigation system in treating sacroiliac joint dislocations decreased operative time with zero intraoperative radiation exposure. The CATMN system is shown to be effective and accurate and provide an alterative option for guidance of the IS screw placement. |
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