Stereotactic CT-guided Percutaneous Stabilization of Posterior Pelvic Ring Fractures: A Preclinical Cadaver Study

Innovations in Image-Guided Procedures: Unraveling Robot-Assisted Non-Hepatic Percutaneous Ablation

Interventional oncology is routinely tasked with the feat of tumor characterization or destruction, via image-guided biopsy and tumor ablation, which may pose difficulties due to challenging-to-reach structures, target complexity, and proximity to critical structures. Such procedures carry a risk-to-benefit ratio along with measurable radiation exposure. To streamline the complexity and inherent variability of these interventions, various systems, including table-, floor-, gantry-, and patient-mounted (semi-) automatic robotic aiming devices, have been developed to decrease human error and interoperator and intraoperator outcome variability. Their implementation in clinical practice holds promise for enhancing lesion targeting, increasing accuracy and technical success rates, reducing procedure duration and radiation exposure, enhancing standardization of the field, and ultimately improving patient outcomes. This narrative review collates evidence regarding robotic tools and their implementation in interventional oncology, focusing on clinical efficacy and safety for nonhepatic malignancies.

Navigation and Robotics in Interventional Oncology: Current Status and Future Roadmap

Interventional oncology (IO) is the field of Interventional Radiology that provides minimally invasive procedures under imaging guidance for the diagnosis and treatment of malignant tumors. Sophisticated devices can be utilized to increase standardization, accuracy, outcomes, and "repeatability" in performing percutaneous Interventional Oncology techniques. These technologies can reduce variability, reduce human error, and outperform human hand-to-eye coordination and spatial relations, thus potentially normalizing an otherwise broad diversity of IO techniques, impacting simulation, training, navigation, outcomes, and performance, as well as verification of desired minimum ablation margin or other measures of successful procedures. Stereotactic navigation and robotic systems may yield specific advantages, such as the potential to reduce procedure duration and ionizing radiation exposure during the procedure and, at the same time, increase accuracy. Enhanced accuracy, in turn, is linked to improved outcomes in many clinical scenarios. The present review focuses on the current role of percutaneous navigation systems and robotics in diagnostic and therapeutic Interventional Oncology procedures. The currently available alternatives are presented, including their potential impact on clinical practice as reflected in the peer-reviewed medical literature. A review of such data may inform wiser investment of time and resources toward the most impactful IR/IO applications of robotics and navigation to both standardize and address unmet clinical needs.

Artificial intelligence and CT-based 3D statistical modeling to assess transsacral corridors and plan implant positioning

Transsacral corridors at levels S1 and S2 represent complex osseous spaces allowing percutaneous fixation of non- or minimally-displaced fragility fractures of the sacrum. To safely place transsacral implants, they must be completely intraosseous. However, standard radiographs and CT do not properly demonstrate the corridor's intricate configuration. Our goal was to facilitate the three-dimensional assessment of transsacral corridors using artificial intelligence and the planning of transsacral implant positioning. In total, 100 pelvic CTs (49 women, mean age: 58.6 ± SD 14.8 years; 51 men, mean age: 60.7 ± SD 13 years) were used to compute a 3D statistical model of the pelvic ring. On the basis of morphologic features (=predictors) and principal components scores (=response), regression learners were interactively trained, validated, and tuned to predict/sample personalized 3D pelvic models. They were matched via thin-plate spline transformation to a series of 20 pelvic CTs with fragility fractures of the sacrum (18 women and 2 men, age: 69-9.5 years, mean age: 78.65 ± SD 8.4 years). These models demonstrated the availability, dimension, cross-section, and symmetry of transsacral corridors S1 and S2, as well as the planned implant position, dimension, axes, and entry and exit points. The complete intraosseous pathway was controlled in CT reconstructions. We succeeded to establish a workflow determining transsacral corridors S1 and S2 using artificial intelligence and 3D statistical modeling.

Percutaneous screw fixation of the iliosacral joint: A case-based preoperative planning approach reduces operating time and radiation exposure

INTRODUCTION

A preoperative planning approach for percutaneous screw fixation of the iliosacral joint provides specific entry points (EPs) and aiming points (APs) of intraosseous screw pathways (as defined by CT scans) for lateral fluoroscopic projections used intraoperatively. The potential to achieve the recommended EPs and APs, to obtain an ideal screw position (perpendicular to the iliosacral joint), to avoid occurrence of extraosseous screw misplacement, to reduce the operating time and the radiation exposure by utilizing this planning approach have not been described yet.

METHODS

On preoperative CT scans of eight human cadaveric specimen individual EPs and APs were identified and transferred to the lateral fluoroscopic projection using a coordinate system with the zero-point in the center of the posterior cortex of the S1 vertebral body (x-axis parallel to upper S1 endplate). Distances were expressed in relation to the anteroposterior distance of the S1 upper endplate (in%). In each specimen on one side a screw was placed with provided EP and AP (New Technique) whereas at the contralateral side a screw was placed without given EP and AP (Conventional Technique). Both techniques were compared using postoperative CT scans to assess distances between predefined EPs and APs and the actually obtained EPs and APs, screw angulations in relation to the iliosacral joint in coronal and axial planes and the occurrence of any extraosseous screw misplacement. The "operating time (OT)" and the "time under fluoroscopy (TUF)" were recorded. Statistical analysis was performed by the Wilcoxon signed-rank test.

RESULTS

EPs were realized significantly more accurate using the new technique in vertical direction. The screw positions in relation to the iliosacral joint showed no significant difference between both techniques. Both techniques had one aberrantly placed screw outside the safe corridor. The (mean±SD) "OT" and the (mean±SD) "TUF" were significantly decreased using the new technique compared to the conventional technique (OT: 7.6±2min versus 13.1±5.8min, p=0.012; TUF: 1.5±0.8min versus 2.2±1.1min).

CONCLUSION

The presented preoperative planning approach increases the accuracy in percutaneous screw fixation of the iliosacral joint, reduces operating time and minimizes radiation exposure to patient and staff.

Electromagnetic Real Time Navigation in the Region of the Posterior Pelvic Ring: An Experimental In-Vitro Feasibility Study and Comparison of Image Guided Techniques

Background

Electromagnetic tracking is a relatively new technique that allows real time navigation in the absence of radiation. The aim of this study was to prove the feasibility of this technique for the treatment of posterior pelvic ring fractures and to compare the results with established image guided procedures.

Methods

Tests were performed in pelvic specimens (Sawbones^®) with standardized sacral fractures (Type Denis I or II). A gel matrix simulated the operative approach and a cover was used to disable visual control. The electromagnetic setup was performed by using a custom made carbon reference plate and a prototype stainless steel K-wire with an integrated sensor coil. Four different test series were performed: Group OCT: Optical navigation using preoperative CT-scans; group O3D: Optical navigation using intraoperative 3-D-fluoroscopy; group Fluoro: Conventional 2-D-fluoroscopy; group EMT: Electromagnetic navigation combined with a preoperative Dyna-CT. Accuracy of screw placement was analyzed by standardized postoperative CT-scan for each specimen. Operation time and intraoperative radiation exposure for the surgeon was documented. All data was analyzed using SPSS (Version 20, 76 Chicago, IL, USA). Statistical significance was defined as p< 0.05.

Results

160 iliosacral screws were placed (40 per group). EMT resulted in a significantly higher incidence of optimal screw placement (EMT: 36/40) compared to the groups Fluoro (30/40; p< 0.05) and OCT (31/40; p< 0.05). Results between EMT and O3D were comparable (O3D: 37/40; n.s.). Also, the operation time was comparable between groups EMT and O3D (EMT 7.62 min vs. O3D 7.98 min; n.s.), while the surgical time was significantly shorter compared to the Fluoro group (10.69 min; p< 0.001) and the OCT group (13.3 min; p< 0.001).

Conclusion

Electromagnetic guided iliosacral screw placement is a feasible procedure. In our experimental setup, this method was associated with improved accuracy of screw placement and shorter operation time when compared with the conventional fluoroscopy guided technique and compared to the optical navigation using preoperative CT-scans. Further studies are necessary to rule out drawbacks of this technique regarding ferromagnetic objects.

Anatomical considerations for percutaneous trans ilio-sacroiliac S1 and S2 screw placement

OBJECTIVE

To determine the presence of a consistent osseous corridor through S1 and S2 and fluoroscopic landmarks thereof, which could be used for safe trans ilio-sacroiliac screw fixation of posterior pelvic ring disorders.

STUDY DESIGN

Computed tomography (CT) based anatomical investigation utilising multiplanar image and trajectory reconstruction (Agfa-IMPAX Version 5.2 software). Determination of the presence and dimension of a continuous osseous corridor in the coronal plane of the sacrum at the S1 and S2 vertebral levels.

OUTCOME MEASURES

Determination of: (a) the presence of an osseous corridor in the coronal plane through S1 and S2 in males and females; (b) the dimension of the corridor with regard to diameter and length; (c) the fluoroscopic landmarks of the corridor.

RESULTS

The mean cross-sectional area for S1 corridors in males and females was 2.13 and 1.47 cm(2) , respectively. The mean cross-sectional area for the S2 corridor in males and females was 1.46 and 1.13 cm(2), respectively. The limiting anatomical factor is the sagittal diameter of the sacral ala at the junction to the vertebral body. The centre of the S1 and S2 corridor is located in close proximity to the centre of the S1 and S2 vertebrae on the lateral fluoroscopic view as determined by the adjacent endplates and anterior and posterior vertebral cortices.

CONCLUSION

Two-thirds of males and females have a complete osseous corridor to pass a trans-sacroiliac S1 screw of 8 mm diameter. The S2 corridor was present in all males but only in 87 % of females. Preoperative review of the axial CT slices at the midpoint of the S1 or S2 vertebral body allows the presence of a trans-sacroiliac osseous corridor to be determined by assessing the passage at the narrowest point of the corridor at the junction of the sacral ala to the vertebral body.

Three-dimensional navigation is more accurate than two-dimensional navigation or conventional fluoroscopy for percutaneous sacroiliac screw fixation in the dysmorphic sacrum: a randomized multicenter study

OBJECTIVES

To evaluate the accuracy of computer-assisted sacral screw fixation compared with conventional techniques in the dysmorphic versus normal sacrum.

DESIGN

Review of a previous study database.

SETTING

Database of a multinational study with 9 participating trauma centers.

PATIENTS

The reviewed group included 130 patients, 72 from the navigated group and 58 from the conventional group. Of these, 109 were in the nondysmorphic group and 21 in the dysmorphic group.

INTERVENTION

Placement of sacroiliac (SI) screws was performed using standard fluoroscopy for the conventional group and BrainLAB navigation software with either 2-dimensional or 3-dimensional (3D) navigation for the navigated group.

MAIN OUTCOME MEASUREMENTS

Accuracy of SI screw placement by 2-dimensional and 3D navigation versus conventional fluoroscopy in dysmorphic and nondysmorphic patients, as evaluated by 6 observers using postoperative computerized tomography imaging at least 1 year after initial surgery. Intraobserver agreement was also evaluated.

RESULTS

There were 11.9% (13/109) of patients with misplaced screws in the nondysmorphic group and 28.6% (6/21) of patients with misplaced screws in the dysmorphic group, none of which were in the 3D navigation group. Raw agreement between the 6 observers regarding misplaced screws was 32%. However, the percent overall agreement was 69.0% (kappa = 0.38, P < 0.05).

CONCLUSIONS

The use of 3D navigation to improve intraoperative imaging for accurate insertion of SI screws is magnified in the dysmorphic proximal sacral segment. We recommend the use of 3D navigation, where available, for insertion of SI screws in patients with normal and dysmorphic proximal sacral segments.

LEVEL OF EVIDENCE

Therapeutic level I.

Sacroiliac screw fixation: A mini review of surgical technique

The sacral percutaneous fixation has many advantages but can be associated with a significant exposure to X-ray radiation. Currently, sacroiliac screw fixation represents the only minimally invasive technique to stabilize the posterior pelvic ring. It is a technique that should be used by experienced surgeons. We present a practical review of important aspects of this technique.

Integration of fluoroscopy-based guidance in orthopaedic trauma surgery - a prospective cohort study

INTRODUCTION

Computer-assisted guidance systems are not used frequently for musculoskeletal injuries unless there are potential advantages. We investigated a novel fluoroscopy-based image guidance system in orthopaedic trauma surgery.

MATERIALS AND METHODS

The study was a prospective, not randomised, single-centre case series at a level I trauma centre. A total of 45 patients with 46 injuries (foot 12, shoulder 10, long bones seven, hand and wrist seven, ankle seven and spine and pelvis four) were included. Different surgical procedures were examined following the basic principles of the Arbeitsgemeinschaft für Osteosynthesefragen/Association for the Study of Internal Fixation (AO/ASIF). Main outcome measurements were the number of trials for implant placement, total surgery time, usability via user questionnaire and system failure rate.

RESULTS

In all cases, the trajectory function was used, inserting a total of 56 guided implants. The system failed when used in pelvic and spinal injuries, resulting in a total failure rate of 6.5% (n=3) of all included cases. The overall usability was rated as good, scoring 84.3%.

CONCLUSION

The novel image-guidance system could be integrated into the surgical workflow and was used successfully in orthopaedic trauma surgery. Expected advantages should be explored in randomised studies.

Kirschner wire placement in scaphoid bones using intraoperative CT-guided stereotaxy

BACKGROUND

Minimally invasive ostesynthesis of scaphoid fractures may reduce the risk of fracture non-union and shorten the duration of illness. The aim of this study was to analyze the technical feasibility and targeting accuracy of computed tomography (CT) - guided stereotactic Kirschner (K)-wire positioning in the scaphoid.

METHODS

Nineteen Formalin preserved cadaveric upper extremities (10 right, 9 left) were fixed in 90 degree dorsal extension for percutaneous access from palmar. An ideal central position of the K-wire was planned on the computer adapted from intraoperative CT data. A 3D navigation system and stereotactic targeting device were used for K-wire placement. Target positioning errors were evaluated by fusion of the control CT with the K-wire in place with the planning CT.

RESULTS

The procedure allowed for an easy and rigid wrist fixation. K-wire placement showed mean ± SD lateral targeting errors of 0.9 ± 0.5 mm at the scaphoid bone entry and 1.2 ± 0.7 mm at the K-wire tip. The mean angular error was 1.3° ± 1.1° . Total duration of the intervention ranged between 19 and 23 min.

CONCLUSION

CT-guided stereotactic K-wire placement in scaphoid bones is highly accurate. The technique may guide minimally invasive screw-osteosynthesis of scaphoid fractures.

CT-guided stereotactic targeting accuracy of osteoid osteoma

BACKGROUND

The aim of this study was to evaluate the CT-guided stereotactic targeting accuracy for radiofrequency ablation of osteoid osteoma (OO), a small, benign but painful osseous lesion.

METHODS

Patient and extremity were fixed in a vacuum cushion. The OO was targeted using an optical navigation system with a stereotactic targeting device. For evaluation of targeting errors, the control CT with the needle in place was fused with the planning CT.

RESULTS

In 16 consecutive patients, nine OOs in the femur, four in the tibia, one in the spine, one in the ulna and one in the pubic bone were successfully targeted without complications. The mean ± SD lateral targeting error was 2.6 ± 1.7 mm at the needle entry and 1.9 ± 1.2 mm at the needle tip, and the mean angular error was 2.0 ± 1.3°.

CONCLUSION

Stereotaxy allows for accurate and safe targeting of OOs in various bone regions.

The application of a computer-assisted thermoplastic membrane navigation system in screw fixation of the sacroiliac joint--a clinical study

BACKGROUND

We inserted iliosacral screws with the aid of a computer-assisted thermoplastic membrane navigation (CATMN) system which is widely used for the accurate and repeatable location tumour in radiation therapy. We hypothesised that application of the CATMN system on IS screws' insertion will provide a superior result to conventional fluoroscopic imaging with less operative time, more accuracy and lower complication rates.

METHODS

We prospectively evaluated 26 consecutive patients who suffered from sacroiliac joint fractures and dislocations (type C, Tile classification) from April 2007 to June 2010 in our hospital. Patients were randomised into two groups: 13 patients in control group and 13 patients in CATMN groups. After operation, inlet and outlet X-ray views and computed tomography (CT) scanning were performed to confirm and compare the screw positions. The operative time, blood loss and accuracy (measured with postoperative CT) were analysed 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 intra-operative blood loss was 145.4±112.0ml, and operation time was 619.2±199.5s. 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 average intra-operative blood loss was 46.2±24.3ml and the operation time was 353.8±111.2s. Operative time and blood loss were reduced significantly with the CATMN system (p<0.05).

CONCLUSION

Application of CATMN system has high accuracy in treating sacroiliac joint dislocations and provides a new alternative method for guidance of the IS screw placement.

Two-dimensional fluoroscopic navigation in posterior cruciate ligament reconstruction: a preclinical cadaver study

OBJECTIVES

To assess the feasibility and accuracy of frameless stereotactic two-dimensional fluoroscopy-assisted guide pin (GP) placement in posterior cruciate ligament (PCL) reconstruction in human cadavers.

MATERIALS AND METHODS

A total of 13 pins were placed in 7 cadaver specimens, using a fluoroscopic-based navigation technique. The knees were fixed noninvasively on a carbon baseplate. Interventions were planned on intraoperatively acquired perpendicular fluoroscopic images. A stereotactic aiming device was mounted to the carbon baseplate and adjusted according to the planned trajectories. GPs were advanced through the aiming device to the precalculated depth. GP positions were verified by image fusion of the fluoroscopic planning and control data, respectively. Measurements were scored on three occasions by one independent observer. In order to assess interobserver reliability, measurements were scored by two further independent observers on one occasion.

RESULTS

The femoral cohort included seven GP placements in seven cadavers. Mean GP placement accuracy according to plan was 1.3 mm (SD 0.9 mm, range 0.3-3.8 mm) at the target point. The recorded femoral angular misalignment of GPs was 1.1 degrees (SD 0.9 degrees , range 0.2 degrees -3.3 degrees ). The tibial cohort included six GP placements in six cadavers. Mean GP placement accuracy according to the plan was 1.8 mm (SD 2.1 mm, range 0.3-9.5 mm). The recorded tibial angular misalignment of GPs was 1.4 degrees (SD 1.1 degrees , range 0.1 degrees -5 degrees ). Navigated GP implantation, as planned, was optimal in six out of seven cases in the femoral cohort and in four out of six cases in the tibial cohort.

CONCLUSION

Our preliminary cadaver study suggests that the use of fluoroscopic-based navigation combined with a stereotactic targeting device may be a helpful tool to improve PCL reconstruction. In addition, this method may also be used for other minimal invasive skeletal interventions.

Accuracy of minimally invasive navigated acetabular and iliosacral fracture stabilization using a targeting and noninvasive registration device

BACKGROUND

To assess the feasibility and accuracy of guide pin (GP) placement using a combined noninvasive patient immobilization and stereotactic targeting system in computer-assisted percutaneous pelvic fracture stabilization.

METHODS

A total of 12 patients with negligible dislocated unstable pelvic fractures were enrolled in this study, performed between February 2002 and October 2005. Our original plans included 13 GP placements in the iliosacral area (SF) and 8 in the acetabular (AF) area. Patients were bedded on a noninvasive dual-vacuum immobilization device. Interventions were planned on a navigation system using intraoperatively acquired CT data. Radiodense markers glued to the skin and the immobilization device provided synchronization between virtual data set and real anatomical situation. A stereotactic targeting device was used for stabilization of GP tracking. GP positions were verified intraoperatively by CT, followed by fracture stabilization with cannulated screws.

RESULTS

Mean GP placement accuracy according to plan: (1) SF-cohort: 2.8 mm (SD 2.0 mm, range 0.5-9.0 mm) at the bony entry point and 3.8 mm (SD 2.3 mm, range 0.6-9.5 mm) at the target point. (2) AF-cohort: 3.0 mm (SD 0.9 mm, range 1.6-4.9 mm) at the bony entry point and 3.9 mm (SD 1.9 mm, range 1.6-7.5 mm) at the target point. GP placement succeeded optimally in 11 out of 13 cases in the SF-cohort, and 6 out of 8 cases in the AF-cohort. The individual average dose-length product (DLP) per successful finished procedure was 1,576 mGy x cm (SD 812 mGy x cm, range 561-2,739 mGy x cm).

CONCLUSION

Our findings substantiate application of the noninvasive patient immobilization and stereotactic targeting system as effective in computer-assited percutaneous stabilization of sacral bone fractures/SI joint disruptions and coronally oriented acetabular dome fractures. We recommend according to the ALARA (as low as reasonable achievable) principle: first, the kV and mAs values have to be reduced. Second, the scanned volume has to be strictly limited to the area of interest. Third, the number of control CTs have to be minimized. Also, the IsoC might be a better choice for implant tracking below 12 cm to reduce the radiation dose to the minimum. We believe that for all high-precise GP placements in the acetabular column area, further improvements in GP guidance (inhibiting pin tip slipping and detecting intraosseous GP deflection) are necessary.

Treatment of posterior pelvic ring injuries with minimally invasive percutaneous plate osteosynthesis

From January 2004 to July 2007, 21 patients with injuries at the posterior pelvic ring were treated with locking compression plate osteosynthesis through a minimally invasive approach and followed up for a mean of 12.2 months. Preoperative and postoperative radiography was conducted to assess the reduction and union. The mean operation time was 60 minutes (range: 40-80). Intraoperative blood loss was 50-150 ml. All patients achieved union at the final follow-up. The overall radiological results were excellent or good in 17 patients (85%). The functional outcome was excellent or good in 18 patients (90%). There was no iatrogenic nerve injury, deep infection or failure of fixation. We believe that fixation with a locking compression plate is an effective method for the treatment of injuries of the posterior pelvic ring in view of its convenience, minimal traumatic invasion and lower morbidity.