Computed tomography image-guided surgery in complex acetabular fractures

Inroads Toward Robot-Assisted Internal Fixation of Bone Fractures Using a Bendable Medical Screw and the Curved Drilling Technique

Internal fixation is a common orthopedic procedure in which a rigid screw is used to fix fragments of a fractured bone together and expedite the healing process. However, the rigidity of the screw, geometry of the fractured anatomy (e.g. femur and pelvis), and patient's age can cause an array of complications during screw placement, such as improper fracture healing due to misalignment of the bone fragments, lengthy procedure time and subsequently high radiation exposure. To address these issues, we propose a minimally invasive robot-assisted procedure comprising of a continuum robot, called ortho-snake, together with a novel bendable medical screw (BMS) for fixating the fractures. We describe the implementation of a curved drilling technique and focus on the design, manufacturing, and evaluation of a novel BMS, which can passively morph into the drilled curved tunnels with various curvatures. We evaluate the performance and efficacy of the proposed BMS using both finite element simulations as well as experiments conducted on synthetic bone samples.

The obturator oblique and iliac oblique/outlet views predict most accurately the adequate position of an anterior column acetabular screw

OBJECTIVE

Percutaneous fixation of the acetabulum is a treatment option for select acetabular fractures. Intra-operative fluoroscopy is required, and despite various described imaging strategies, it is debatable as to which combination of fluoroscopic views provides the most accurate and reliable assessment of screw position.

MATERIALS AND METHODS

Using five synthetic pelvic models, an experimental setup was created in which the anterior acetabular columns were instrumented with screws in five distinct trajectories. Five fluoroscopic images were obtained of each model (Pelvic Inlet, Obturator Oblique, Iliac Oblique, Obturator Oblique/Outlet, and Iliac Oblique/Outlet). The images were presented to 32 pelvic and acetabular orthopaedic surgeons, who were asked to draw two conclusions regarding screw position: (1) whether the screw was intra-articular and (2) whether the screw was intraosseous in its distal course through the bony corridor.

RESULTS

In the assessment of screw position relative to the hip joint, accuracy of surgeon's response ranged from 52% (iliac oblique/outlet) to 88% (obturator oblique), with surgeon confidence in the interpretation ranging from 60% (pelvic inlet) to 93% (obturator oblique) (P < 0.0001). In the assessment of intraosseous position of the screw, accuracy of surgeon's response ranged from 40% (obturator oblique/outlet) to 79% (iliac oblique/outlet), with surgeon confidence in the interpretation ranging from 66% (iliac oblique) to 88% (pelvic inlet) (P < 0.0001).

CONCLUSIONS

The obturator oblique and obturator oblique/outlet views afforded the most accurate and reliable assessment of penetration into the hip joint, and intraosseous position of the screw was most accurately assessed with pelvic inlet and iliac oblique/outlet views.

EVIDENCE

Clinical Question.

Three-dimensional printing and patient-specific pre-contoured plate: future of acetabulum fracture fixation?

PURPOSE

Due to the complexity of acetabulum, achieving anatomical contouring intra-operatively is difficult for surgeon. A 3D (dimensional) real model can facilitate us both in contouring the plate pre-operatively and in better pre-operative planning. Patient-specific pre-contoured plate in acetabular fracture has been studied by few researchers but randomized case-control study was lacking. Hence, we conducted a case-control study to evaluate the accuracy of patient-specific pre-contoured plate.

MATERIALS AND METHODS

Prospective randomized case control study was conducted. 21 patients were included. 10 patients were distributed in "case" group and remaining 11 in "control" group.

INCLUSION CRITERIA

Displaced acetabulum fractures with displacement of ≥3 mm in adults who reported within 3 weeks of injury. Exclusion criteria were: Open fractures, associated Morel-Lavallée lesion and patients with >3 weeks old fracture. In case group, patient-specific real 3D model of fractured acetabulum was generated using rapid prototyping technology and plates were contoured pre-operatively. Control group was treated using intra-operative contoured plates. Both the groups were compared using parameters: Blood loss, Surgery time, post-operative reduction on X-ray, post-surgical residual displacement and reduction achieved as evaluated by CT scan.

RESULTS

Reduced blood loss (100 ml less in case group) and surgical time (12 min less in case group) and better post-operative reduction were observed in case than control. In control group, 4 patients even had step of 2-3 mm, which was not seen in case group. All the pre-contoured plates fitted well to the pelvis intra-operatively. Reduction achieved as evaluated by CT was more in "case" group with statistically significant outcomes (p < 0.05).

CONCLUSION

Patient-specific pre-contoured plate made using 3D model is a better implant than intra-operatively contoured plate. Real-time 3D pelvis model is an accurate technique for pre-operative planning in acetabular fractures.

Three-dimensional printing and patient-specific pre-contoured plate: future of acetabulum fracture fixation?

PURPOSE

Due to the complexity of acetabulum, achieving anatomical contouring intra-operatively is difficult for surgeon. A 3D (dimensional) real model can facilitate us both in contouring the plate pre-operatively and in better pre-operative planning. Patient-specific pre-contoured plate in acetabular fracture has been studied by few researchers but randomized case-control study was lacking. Hence, we conducted a case-control study to evaluate the accuracy of patient-specific pre-contoured plate.

MATERIALS AND METHODS

Prospective randomized case control study was conducted. 21 patients were included. 10 patients were distributed in "case" group and remaining 11 in "control" group.

INCLUSION CRITERIA

Displaced acetabulum fractures with displacement of ≥3 mm in adults who reported within 3 weeks of injury. Exclusion criteria were: Open fractures, associated Morel-Lavallée lesion and patients with >3 weeks old fracture. In case group, patient-specific real 3D model of fractured acetabulum was generated using rapid prototyping technology and plates were contoured pre-operatively. Control group was treated using intra-operative contoured plates. Both the groups were compared using parameters: Blood loss, Surgery time, post-operative reduction on X-ray, post-surgical residual displacement and reduction achieved as evaluated by CT scan.

RESULTS

Reduced blood loss (100 ml less in case group) and surgical time (12 min less in case group) and better post-operative reduction were observed in case than control. In control group, 4 patients even had step of 2-3 mm, which was not seen in case group. All the pre-contoured plates fitted well to the pelvis intra-operatively. Reduction achieved as evaluated by CT was more in "case" group with statistically significant outcomes (p < 0.05).

CONCLUSION

Patient-specific pre-contoured plate made using 3D model is a better implant than intra-operatively contoured plate. Real-time 3D pelvis model is an accurate technique for pre-operative planning in acetabular fractures.

Fluoroscopic views for safe insertion of lag screws into the posterior column of the acetabulum

BACKGROUND

Percutaneous lag screw fixation is an alternative treatment for non-displaced or minimally displaced posterior column fractures. This study aims to explore new fluoroscopic views of the acetabulum for safe percutaneous insertion of posterior column lag screws.

METHODS

Axial computed tomography (CT) scans were taken of sixteen embalmed adult cadavers. The axial CT images at the level of the middle height of the acetabulum were selected. The angle (angle α) between the posterior cortex of the posterior column (PCPC) and the line intersecting the axial plane and the coronal plane, and the angle (angle β) between the medial wall and the line intersecting the axial plane and the sagittal plane were identified and measured. Tangential views of the PCPC and medial wall were obtained by referencing the measured angles. A lag screw was inserted into the posterior columns of the sixteen pelvic specimens under fluoroscopic guidance using an iliac oblique view and the two tangential views. CT scans were performed to evaluate the lag screw position. Axial CT images of 52 volunteers were obtained and the angles α and β were measured following the same methods used for the cadaveric specimens.

RESULTS

The angles α and β for the specimens were 29.3 ± 2.8.1 and 8.1 ± 1.4 degrees, respectively. On the tangential view of the PCPC, the posterior cortex appears as a nearly straight line between the lesser and greater sciatic notches. On the tangential view of the medial wall, the medial wall appears as a distinct straight line. Using these radiographic images, the lag screws were inserted into the posterior columns of bony pelvic specimens. Screw placement was confirmed by CT, and found to be fully intraosseous in all cases without any cortical breaches. The angles α and β were 30.4 ± 4.1 and 9.2 ± 1.9 degrees for male volunteers and 28.5 ± 3.7 and 7.7 ± 1.8 degrees for female volunteers, significant difference in these angles between cadaveric specimens and human volunteers.

CONCLUSION

The tangential views of both the PCPC and medial wall can be obtained following the aforementioned methods The oblique iliac view and the two tangential views enable safe insertion of posterior column lag screws.

The study of broken quadrilateral surface in fractures of the acetabulum

PURPOSE

Three-dimensional computerised tomography (3DCT) can provide comprehensive patho-anatomy of complex bone on a single image. Though important, the key articular quadrilateral [Q] surface has not been a part of the systems developed for classifying acetabulum fractures. The purpose of the study was to simplify the complexity of classification by the direct sign of the broken Q surface which lies opposite the entire floor of the acetabulum.

METHODS

The study reviewed 84 acetabular fractures using 3DCT images of the interior lateral view (IL) taken between June 2002 to December 2009. Fractures were traditionally classified using the anatomical disruption, plane of the fracture line breaking through or not through the bone column described by Judet and Letournel.

RESULTS

The 3D images clearly show the primary site of impaction acting on the acetabulum and the whole course of fracture. The image could not illustrate disruption of the lips of acetabulum and congruity of hip joints in 20 cases of wall (W) fracture. There were 30 transverse (T) fractures classified when the acetabulum was divided horizontally from front to back into upper and lower parts and 34 cases of column (C) fracture when the main vertical lines run and collide along the anterior and posterior column.

CONCLUSIONS

This study showed that the well-known complex fractures can be satisfactorily classified with the broad flat inner plane of the Q surface.

Percutaneous screw fixation for the acetabular fracture with quadrilateral plate involved by three-dimensional fluoroscopy navigation: surgical technique

BACKGROUND

The percutaneous three-dimensional (3D)-fluoroscopic-navigated screw directing to the quadrilateral plate was attempted.

MATERIALS AND METHODS

Five patients with acetabular fractures were treated by 3D navigated percutaneous screw. The quadrilateral plate was involved in all the patients. The Arcadis 3D (ARCADIS Orbic 3D(®); Siemens AG Healthcare Sector, Erlangen, Germany) and computer navigation system (stryker navigation system) were employed, screwing trajectory was attempted to anchor the quadrilateral plate perpendicularly to the fracture line and close to the joint cartilage as much as possible. Parameters including fracture gap closure (P1), distance to the joint cartilage (P2), angulations between the screw and the fracture line (P3), were measured with the software installed on the machine of Arcadis 3D.

RESULT

Seven screws were inserted with the use of 3D fluoroscopic navigation. The quadrilateral plate was hold by percutaneous screws. The closure of fracture gap was achieved in 3 patients by 2-3mm. The nearest distance from the screw to the joint cartilage was ranged from <1mm to 6mm. The angulations between the screw and the fracture line was 80-90° in three patients, it was 60° and 65° respectively on the rest two patients. All patients felt pain free 1week after the operation. No complication was noted postoperatively.

CONCLUSION

The surgical technique of percutaneous screwing for the acetabular fracture with three-dimensional fluoroscopy-based navigation was demonstrated.

PROSPECTIVE STUDY ON SEVENTY-SIX CASES OF FRACTURED ACETABULUM WITH SURGICAL TREATMENT

OBJECTIVE

To conduct a prospective study on unstable and incongruent fractures of the acetabulum, in comparison with the literature, covering the type of access, fixation materials, degree of reduction, type of fracture and results after surgery.

METHODS

The authors evaluated 76 patients with unstable and incongruent fracture of the acetabulum between January 1999 and December 2009. The Marvin Tile classification was used, and all cases were treated surgically using the technique recommended by the AO-ASIF group.

RESULTS

The radiological evaluation was done in accordance with the Ruesch criteria, and good, excellent or perfect results were obtained for 64 patients (84.2%). The clinical evaluation was done in accordance with the Harris criteria, and good or excellent results were obtained for 62 patients (81.6%). The complications were assessed and, in comparison with the literature, were shown to be compatible with previous reports even after the statistical analysis.

CONCLUSION

It was concluded that anatomical reduction and stable fixation are important for good results.

The surgical treatment of anterior column and anterior wall acetabular fractures

Isolated fractures of the anterior column and anterior wall are a relatively rare subgroup of acetabular fractures. We report our experience of 30 consecutive cases treated over ten years. Open reduction and internal fixation through an ilioinguinal approach was performed for most of these cases (76.7%) and percutaneous techniques were used for the remainder. At a mean follow-up of four years (2 to 6), 26 were available for review. The radiological and functional outcomes were good or excellent in 23 of 30 patients (76.7%) and 22 of 26 patients (84.6%) according to Matta’s radiological criteria and the modified Merlé d’Aubigné score, respectively.

Complications of minor to moderate severity were seen in six of the 30 cases (20%) and none of the patients underwent secondary surgery or replacement of the hip.

Use of rapid prototyping and three-dimensional reconstruction modeling in the management of complex fractures

BACKGROUND

The production of a copy of the fracture or a deformity in a bone with a complex geometry can be one of the important applications of the integration between two modern computer-based technologies, reverse engineering (RE) and rapid prototyping (RP).

METHODS

This article reviews recent development in this field and present a case series about the use of medical CT/MRI scanning, three-dimensional reconstruction, anatomical modeling, computer-aided design, RP and computer-aided implantation in treating a complex fracture of acetabulums, calcaneum, and medial condyle of femur (Hoffa's fracture).

CONCLUSION

The use of RP technology helped us to understand the fracture configuration and to achieve near anatomical reduction. With this we believe, this technology will reduce the surgical time as was observed in our cases. This consequently, will lower the requirement of an anesthetic dosage and decrease the intraoperative blood loss.In summary, the merging of computational analysis, modeling, designing, and fabrication will serve as important means to treat conditions and fractures around joints, spine, acetabulum, and craniofacial region.

LEVEL OF EVIDENCE

Level 4, case series.

Quantitative anatomic basis of antegrade lag screw placement in posterior column of acetabulum

BACKGROUND

Lag screw fixation has been recommended for treatment of acetabular and pelvic fracture for several years. The aim of the present study was to determine the projection of the axis of the posterior column on the inner table of the iliac wing in the supra-acetabular region.

METHODS

Thirty adult dried bony hemipelves specimens and other five intact adult dried pelvic specimens were included in this study. The projection point of the axis of the posterior column of the acetabulum was determined on the inner table of the iliac wing of the hemipelves specimens. The perpendicular distance from the optimal entry point to the linea terminalis of pelvis was measured and recorded as the lateral distance. The same measurement along the linea terminalis from the optimal entry point to the junction between the anterior border of iliosacral articulation and the linea terminalis of pelvis was made and recorded as the posterior distance. The depth of the anchor path and the corresponding average retroversion angulation and extraversion angulation were also measured. According to the results acquired from this study, a series of 6.5 mm lag screws were inserted into the posterior column of each side of the other five intact specimens, respectively, to evaluate the position of the screws. The data were expressed as mean +/- SD and analyzed by using the descriptive methods with SPSS 10.0.

RESULTS

The average length of lag screw was 104.8 +/- 4.2 mm. The average lateral distance was 16.8 +/- 2.1 mm. The average posterior distance was 23.5 +/- 3.4 mm. The corresponding average retroversion angulation and extraversion angulation were 57 degrees 36' +/- 4 degrees 28' and 119 degrees 18' +/- 2 degrees 32', respectively. The insertion of the single 6.5 mm lag screw of adequate length was possible in the posterior column along its anchor path and no accidental extraosseous or intraarticular screw placement had occurred.

CONCLUSIONS

The present study describes a safe anchor path of antegrade lag screw fixation in the posterior column. Insertion of the lag screws of adequate length is possible in the posterior column along its functional axis.

Fluoroscopic templating technique for precision arthroscopic rim trimming

Arthroscopic rim trimming for femoroacetabular impingement can be technically challenging to perform with precision. Intraoperative assessment of the extent of acetabular rim resection is very important. Over-resection can lead to hip instability and even iatrogenic dislocation. Under-resection may leave residual impingement. A novel imaging technique is presented that is simple, practical, and readily available. The technique involves matching the fluoroscopic C-arm image intensifier to the operative pelvis while under the desired amount of hip distraction so that a horizontal anteroposterior hip image appears on the viewing monitor. An erasable marking pen is used to draw the desired area of planned acetabular rim resection directly on the viewing monitor screen. Intermittent fluoroscopic images with the raised stationary C-arm device allow assessment of superior (lateral) and anterior rim resection. The surgeon "wipes away" the drawn template with the radiopaque metallic bur until the all-important medial template border is reached, indicating that the actual rim resection matches that intended in a controlled and precise manner.

Utility of intraoperative three-dimensional imaging at the hip and knee joints with and without navigation

Intraoperative three-dimensional imaging in orthopaedic trauma care has achieved greater importance over the last few years in some specialized hospital centers. For various types of peripheral-extremity trauma, clinical studies have confirmed, on the basis of three-dimensional information, an intraoperative revision rate ranging from 7% to 19%. Three-dimensional C-arm imaging may be used to achieve adequate intraoperative information about the quality of fracture reduction, residual steps, and correct implant placement, and this technique has been described for use in both the hip joint (for acetabular fractures, isolated femoral head [Pipkin-type] fractures, three-dimensional navigated sacroiliac screw or acetabular column screw placements, and, less frequently, for navigated drilling of tumors or osteochondral lesions) and the knee joint (for tibial plateau fractures, complex distal femoral condylar fractures, and navigated targeting of osteochondral lesions in combination with the use of preoperative magnetic resonance imaging scans). Major limitations of this technology include increased intraoperative time requirements, limited image quality compared with that of computed tomographic scans, cost, specific positioning techniques, and the need for radiolucent operating-room tables. Although prospective studies have yet to be conducted, the ways in which the surgeon will benefit from the use of intraoperative three-dimensional imaging are apparent, but indications for combined three-dimensional C-arm navigated procedures at the hip and knee joint are still limited. Future directions may include the use of digital flat-panel detectors and even robotic-controlled C-arm motion.

The long lost art of preoperative planning--resurrected?

Tibial plateau fractures are complex injuries that can affect both knee function and stability. In the past, surgeons have relied on radiographs, viewboxes, tracing paper, and scaled acetate templates to formulate a preoperative plan. With the advent of digital radiography, viewboxes, and standard radiographs are no longer routinely available. The availability of a digital format for preoperative planning has helped to address this, but fragment manipulation and implant templating are not features of most digital radiography systems. Digital surgical planning software allows for these functions thereby enabling the surgeon to formulate a preoperative plan for fracture reduction and fixation. Concomitant use of 3-dimensional (3D) imaging software permits unlimited inspection of the fracture by allowing for oblique or special views through manipulation of the software image as opposed to potentially painful positioning of the injured limb by the patient or radiograph personnel. This case report illustrates the advantages of these new software tools.

Navigation in laparoscopy--prototype research platform for improved image-guided surgery

The manipulation of the surgical field in laparoscopic surgery, through small incisions with rigid instruments, reduces free sight, dexterity, and tactile feedback. To help overcome some of these drawbacks, we present a prototype research and development platform, CustusX, for navigation in minimally invasive therapy. The system can also be used for planning and follow-up studies. With this platform we can import and display a range of medical images, also real-time data such as ultrasound and X-ray, during surgery. Tracked surgical tools, such as pointers, video laparoscopes, graspers, and various probes, allow surgeons to interactively control the display of medical images during the procedure. This paper introduces navigation technologies and methods for laparoscopic therapy, and presents our software and hardware research platform. Furthermore, we illustrate the use of the system with examples from two pilots performed during laparoscopic therapy. We also present new developments that are currently being integrated into the system for future use in the operating room. Our initial results from pilot studies using this technology with preoperative images and guidance in the retroperitoneum during laparoscopy are promising. Finally, we shortly describe an ongoing multicenter study using this surgical navigation system platform.

Percutaneous fixation of the pelvic ring: an update

With the development of systems of trauma care the management of pelvic disruption has evolved and has become increasingly refined. The goal is to achieve an anatomical reduction and stable fixation of the fracture. This requires adequate visualisation for reduction of the fracture and the placement of fixation. Despite the advances in surgical approach and technique, the functional outcomes do not always produce the desired result. New methods of percutaneous treatment in conjunction with innovative computer-based imaging have evolved in an attempt to overcome the existing difficulties. This paper presents an overview of the technical aspects of percutaneous surgery of the pelvis and acetabulum.

The use of a virtual three-dimensional model to evaluate the intraosseous space available for percutaneous screw fixation of acetabular fractures

We created virtual three-dimensional reconstruction models from computed tomography scans obtained from patients with acetabular fractures. Virtual cylindrical implants were placed intraosseously in the anterior column, the posterior column and across the dome of the acetabulum. The maximum diameter which was entirely contained within the bone was determined for each position of the screw. In the same model, the cross-sectional diameters of the columns were measured and compared to the maximum diameter of the corresponding virtual implant. We found that the mean maximum diameter of virtual implant accommodated by the anterior columns was 6.4 mm and that the smallest diameter of the columns was larger than the maximum diameter of the equivalent virtual implant. This study suggests that the size of the screw used for percutaneous fixation of acetabular fractures should not be based solely on the measurement of cross-sectional diameter and that virtual three-dimensional reconstructions might be useful in pre-operative planning.

Smart intramedullary rod for correction of pediatric bone deformity: a preliminary study

We were interested in determining if a smart intramedullary rod made of nitinol shape-memory alloy is capable of correcting deformed immature long bones. Because of limitations in our study design the process was reversed in that we examined the smart rod's ability to create a deformity rather than to correct one. Smart rods of different lengths and diameters were heat-treated to resume a radius of curvature of 30 to 110 mm. The low and high temperature phases of the smart rods were set, respectively, at 0 degrees C to 4 degrees C and 36 degrees C to 38 degrees C. The preshaped smart intramedullary rods were implanted in the cooled martensite phase in the medullary canal of the tibia in eight rabbits, where they restored their austenite form, causing a continuous bending force. On a weekly basis anteroposterior and lateral radiographs of the surgically treated tibia and the contralateral tibia were obtained for comparison. Rabbits were euthanized 6 weeks after surgery and computed tomography scans of both tibias were used for image analysis. Smart rods with a larger radius of curvature showed only minimal signs of remodeling; however, rods with a radius of curvature of 50 and 70 mm generated enough force history to create bone remodeling and deformation. The amount of bone deformation was highly magnified when unicortical corticotomy on the tension side was done. Based on this preliminary study the technology of the smart intramedullary rod may provide a valuable alternative method to correct pediatric skeletal deformities.

Application of computer-generated stereolithography and interpositioning template in acetabular fractures: a report of eight cases

To determine the effectiveness of stereolithography modeling technologies in the surgical treatment of complex acetabular fractures, five patients with a complex fracture of the acetabulum and three patients with posterior wall fractures were considered in this study. The patients were surgically treated using an interposition template for accurate positioning of the fixation plate and screw trajectories. Intraoperative fluoroscopy confirmed precise plate placement and that all screw trajectories missed the hip joint. Fluoroscopy was only needed for confirmation of fracture reduction and for confirmation of screw location. Application of a life-size stereolithographic model of the pelvis and an interpositioning template along with the computer model of the reversed nonfractured contralateral hemipelvis provides an effective means for preoperative planning and accurate fixation of acetabular fractures. Further studies with this type of preplanning equipment may show a decrease in operative time and morbidity, decrease in radiation exposure, and improvement in accuracy of plate and screw placement.

The process and development of image-guided procedures

Medical imaging has been used primarily for diagnosis. In the past 15 years there has been an emergence of the use of images for the guidance of therapy. This process requires three-dimensional localization devices, the ability to register medical images to physical space, and the ability to display position and trajectory on those images. This paper examines the development and state of the art in those processes.