3D Fluoroscopy Research Articles

Intraoperative Myelography in Cervical Multilevel Stenosis Using 3D Rotational Fluoroscopy: Assessment of Feasibility and Image Quality.

Background. Intraoperative myelography has been reported for decompression control in multilevel lumbar disease. Cervical myelography is technically more challenging. Modern 3D fluoroscopy may provide a new opportunity supplying multiplanar images. This study was performed to determine the feasibility and image quality of intraoperative cervical myelography using a 3D fluoroscope. Methods. The series included 9 patients with multilevel cervical stenosis. After decompression, 10 mL of water-soluble contrast agent was administered via a lumbar drainage and the operating table was tilted. Thereafter, a 3D fluoroscopy scan (O-Arm) was performed and visually evaluated. Findings. The quality of multiplanar images was sufficient to supply information about the presence of residual stenosis. After instrumentation, metal artifacts lowered image quality. In 3 cases, decompression was continued because myelography depicted residual stenosis. In one case, anterior corpectomy was not completed because myelography showed sufficient decompression after 2-level discectomy. Interpretation. Intraoperative myelography using 3D rotational fluoroscopy is useful for the control of surgical decompression in multilevel spinal stenosis providing images comparable to postmyelographic CT. The long duration of contrast delivery into the cervical spine may be solved by preoperative contrast administration. The method is susceptible to metal artifacts and, therefore, should be applied before metal implants are placed.

Three-Dimensional Navigation Is More Accurate than Two-Dimensional Navigation or Conventional Fluoroscopy for Percutaneous Sacroiliac Screw Fixation in the Dysmorphic Sacrum

To evaluate the accuracy of computer-assisted sacral screw fixation compared with conventional techniques in the dysmorphic versus normal sacrum. Review of a previous study database. Database of a multinational study with 9 participating trauma centers. 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. 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. 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. 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). 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. Therapeutic level I.

Altered helical axis patterns of the lumbar spine indicate increased instability with disc degeneration

Although the causes of low back pain are poorly defined and indistinct, degeneration of the intervertebral disc is most often implicated as the origin of pain. The biochemical and mechanical changes associated with degeneration result in the discs׳ inability to maintain structure and function, leading to spinal instability and ultimately pain. Traditionally, a clinical exam assessing functional range-of-motion coupled with T2-weighted MRI revealing disc morphology are used to evaluate spinal health; however, these subjective measures fail to correlate well with pain or provide useful patient stratification. Therefore, improved quantification of spinal motion and objective MRI measures of disc health are necessary. An instantaneous helical axis (IHA) approach provides rich temporal three-dimensional data describing the pathway of motion, which is easily visualized. Eighteen cadaveric osteoligamentous lumbar spines (L4–5) from throughout the degenerative spectrum were tested in a pure moment fashion. IHA were calculated for flexion–extension and lateral bending. A correlational study design was used to determine the relationship between disc measurements from quantitative T2⁎ MRI and IHA metrics. Increased instability and out-of-plane rotation with diminished disc health was observed during lateral bending, but not flexion–extension. This new analysis strategy examines the entire pathway of motion, rather than simplifying spinal kinematics to its terminal ends of motion and provides a more sensitive kinematic measurement of disc health. Ultimately, through the use of 3D dynamic fluoroscopy or similar methods, a patient׳s functional IHA in lateral bending may be measured and used to assess their disc health for diagnosis, progression tracking, and treatment evaluation.

Learning curve of 3D fluoroscopy image–guided pedicle screw placement in the thoracolumbar spine

Background contextDuring the past decade, a disproportionate increase of spinal fusion procedures has been observed. Along with this trend, image-guided spine surgery has been experiencing a renaissance in the recent years. A wide range of different navigation systems are available on the market today. However, only few published studies assess the learning curves concerning these new spinal navigation techniques. So far, a study on the learning curve for intraoperative three-dimensional fluoroscopy (3DFL)–navigated pedicle screw (PS) placement is still lacking. PurposeThe purpose of the study was to analyze the learning curve for 3DFL-navigated thoracolumbar PS placement. Study design/settingThe study design included a prospective case series. Patient sampleA cohort of 145 patients were recruited from January 2011 to June 2012. Outcome measuresThe outcome measures were duration of intraoperative 3D scans, PS placement, PS accuracy on postoperative computed tomography (CT) scans, and PS-related revisions and complications. MethodsFrom the introduction of spinal navigation to our department in January 2011 until June 2012, the learning curve for the duration of intraoperative 3D scan acquisition (navigation or control scan) and placement time per screw, intraoperative screw revisions, screw-related complications, revision surgeries, and PS accuracy on postoperative CT scans were assessed in 145 patients undergoing dorsal navigated instrumentation for 928 PS (736 lumbosacral and 192 thoracic). The observed time span was divided into four intervals. Results of the second, third, and last periods were compared with the first (reference) period, respectively. ResultsThe mean navigation 3D scan time decreased (first and fourth periods) from 15.4±7.8 (range, 4–40) to 8.4±3.3 (3–15) minutes (p<.001). The mean control 3D scan time (after PS placement) decreased from 11.2±4.8 (5–25) to 6.6±3.0 (3–15) minutes (p<.001). The mean PS insertion time decreased from 5.3±2.5 (1–15) to 3.2±2.3 (1–17) minutes (p<.001). The mean proportion of correctly positioned PS (all 928) according to the Gertzbein and Robbins classification grades A and B increased initially from 83.1% (first period) to 95.1% (second period, p=.001), 96.4% (third period, p=.002), and 92.4% (fourth period, p=.049). No learning effect was found with respect to intraoperative screw revisions. There was one revision surgery. ConclusionsWe could demonstrate significant learning effects for 3DFL-navigated PS placement with regard to intraoperative 3D scan acquisition, PS placement time, and PS accuracy.

Remnant-preserving anterior cruciate ligament reconstruction using a three-dimensional fluoroscopic navigation system.

IntroductionRecently, remnant-preserving anterior cruciate ligament (ACL) reconstruction has been increasingly performed to achieve revascularization, cell proliferation, and recovery of high-quality proprioception. However, poor arthroscopic visualization makes accurate socket placement during remnant-preserving ACL reconstruction difficult. This study describes a surgical technique used to create an anatomical femoral socket with a three-dimensional (3D) fluoroscopy based navigation system during technically demanding remnant-preserving ACL reconstruction.Surgical TechniqueAfter a reference frame was attached to the femur, an intraoperative image of the distal femur was obtained, transferred to the navigation system and reconstructed into a 3D image. A navigation computer helped the surgeon visualize the entire lateral wall of the femoral notch and lateral intercondylar ridge, even when the remnant of the ruptured ACL impeded arthroscopic visualization of the bone surface. When a guide was placed, the virtual femoral tunnel overlapped the reconstructed 3D image in real time; therefore, only minimal soft tissue debridement was required.Materials and MethodsWe treated 47 patients with remnant-preserving ACL reconstruction using this system. The center of the femoral socket aperture was calculated according to the quadrant technique using 3D computed tomography imaging.ResultsThe femoral socket locations were considered to be an anatomical footprint in accordance with previous cadaveric studies.ConclusionsThe 3D fluoroscopy-based navigation can assist surgeons in creating anatomical femoral sockets during remnant-preserving ACL reconstruction.

P-005 Evaluation of an Automatic Detection and Segmentation Tool for Flow Diverters (Pipeline™ Embolization Device) from C-arm CT Images

PurposeIn addition to stent-assisted coiling, endovascular treatment of intracranial aneurysms using flow diverters, like the Pipeline™ Embolization Device (PED), has become a viable treatment option. Visualization of the device after...

Target visibility enhancement for C-arm cone beam CT-fluoroscopy-guided hepatic needle placement: implementation and accuracy evaluation

Fluoroscopy-guided hepatic intervention is limited by target visibility and respiratory movement. A feasible procedure for visibility enhancement of the key regions and targets in 2D fluoroscopic images is needed. A system was developed to improve targeting by integrating the forward projection of objects extracted from 3D cone beam CT (CBCT) volumes. The target matching accuracy during regular respiration was measured to evaluate the system. 3D CBCT abdominal volumes were acquired and segmented to extract different regions, including the diaphragm, hepatic vessels, bony structures, and hepatic tumor. The segmented result was rendered and projected to generate augmented fluoroscopy fusion images. The target matching accuracy by applying these procedures was evaluated for the hepatic intervention guidance. Quantitative assessment of the target matching accuracy in the upper section of liver was performed for eight targets from four subjects. The 2D and 3D target matching accuracy were 0.98±0.37 and 1.47±0.26 mm, respectively. The 2D target matching accuracy was 1.46±0.67 mm for the target in the lower liver. This accuracy should be acceptable for the 5 mm safety margin required in clinical use. Visibility of targets in 2D fluoroscopy was enhanced to improve interactive navigation guidance for hepatic needle placement. The target matching accuracy for the C-arm cone beam CT-fluoroscopy-guided hepatic needle targeting was sufficient for clinical use.

Ablation of typical atrial flutter using a novel non-fluoroscopic electromagnetic catheter tracking system

Typical atrial flutter is characterized by a stable macro-reentrant circuit around the tricuspid annulus with the cavotricuspid isthmus serving as the critical zone of slow conduction. Catheter ablation targeting this isthmus provides a curative and safe treatment option for the vast majority of patients with atrial flutter. The conventional ablation approach using fluoroscopy for catheter visualization and navigation, however, is associated with substantial radiation exposure to both patients and healthcare personnel. Recently, a novel non-fluoroscopic electromagnetic catheter tracking system has been introduced that enables integration of 3D catheter navigation into the environment of prerecorded conventional 2D fluoroscopy. The feasibility, safety and efficacy of this system have been demonstrated in a variety of invasive electrophysiological procedures. In nonrandomized clinical trials, utilizing the nonfluoroscopic catheter tracking system to support catheter ablation for atrial flutter was associate...

Use of three-dimensional fluoroscopy to determine intra-articular screw penetration in proximal humeral fracture model

Proximal humeral locking plates have significantly improved the treatment of proximal humeral fractures in recent years; however, they are not devoid of complications. Inadvertent screw penetration into the joint is a well-documented complication. Intraoperative 3-dimensional (3D) imaging may assist in detecting intra-articular implant penetration. This study compared the performance of a standard C-arm fluoroscope with a novel 3D imaging fluoroscope in detecting penetrating implants in a proximal humeral fracture model. Zinc-sprayed proximal humerus sawbones were affixed with a proximal humeral locking plate. Six different constructs were assembled. In each specimen, 1 screw, 2 screws, or no screws were inserted 2-mm proud of the articular surface. Each specimen was imaged with a conventional fluoroscope and a 3D imaging fluoroscope. Overall, 36 image sets were prepared for each modality. These were evaluated by 2 fellowship-trained surgeons for intraobserver and interobserver reliability as well for the accuracy of detecting prominent implants in the 2 imaging methods. Overall accuracy for observer A was 89.9% compared with 100% for C-arm fluoroscopy and 3D imaging fluoroscopy (P < .01) and for observer B was 91.1% and 100% (P = .01), respectively. The κ values were 0.74 with C-arm fluoroscopy and 1.0 for the 3D imaging fluoroscopy for observer A, and 0.93 and 1.0, respectively, for observer B. In a proximal humeral fracture model, C-arm fluoroscopy is a highly accurate imaging modality that can minimize the incidence of penetrating screws into the joint. Further clinical studies are required to establish this modality.

Comparison of two-dimensional and three-dimensional fluoroscopy-based navigation in percutaneous sacroiliac screw internal fixation

Objective To compare the advantages and disadvantages of using intraoperative 2 dimensional (2D)-fluoroscopy-based navigation technique and 3 D technique used in percutaneous sacroiliac screw internal fixation,and to find a simple and safe operative method by combined the advantages of the two navigation techniques.Methods From June 2008 to October 2012,we retrospective analyzed 41 cases subject to percutaneous sacroiliac screw fixation.The cases were divided into three groups of A,B,and C according to the operation method:group A,2D-navigation technique; group B,3D-navigation technique; group C:insertion of a guiding pin first with 2D navigation,verification with 3D fluoroscopy and then fixation with cannulated screw.The time of screw insertion,the time of fluoroscopy,and the times of penetrating the vertebrae cortex were compared.Methods We totally used 44 nails,and the mean time of screw insertion in groups A,B and C was (51.2 ± 5.6),(67.7 ± 10.7) and (55.3 ± 4.0) min respectively.The mean fluoroscopy times in groups A,B and C were (74.7 ± 5.6),(144.1 ± 2.1) and (104.3 ±1.0).One screw in the group A penetrated the S1 vertebrae cortex,and the rest two groups had no penetration of nails across the S1 vertebrae cortex.Conclusion Combining the advantages and disadvantages of 2D and 3D navigation,the method of inserting a guiding pin with 2D navigation,and using 3D fluoroscopy to verify it,would not only take less time of operation and fluoroscopy,but also has the same screw accuracy rate as using the 3D navigation technique. Key words: Computer navigation system; Sacroiliac screw; Internal fixation

Accuracy of 3D fluoroscopy in cranial stereotactic surgery: A comparative study in phantoms and patients

To assess the precision and accuracy of 3D fluoroscopy (XT) in phantoms and patients compared to computed tomography (CT) in localizing stereotactic probes. Approval was obtained from the institutional research ethics board. The prospective phantom study was compared to a retrospective patient cohort. Accuracy was assessed by the mean error and precision by the mean dispersion between XT and CT with a cubic or a skull phantom containing metallic spheres installed on plates or along trajectories. Significance was assessed by Friedman's and Levene's test. Secondary endpoints were Euclidean error, other influences e.g. installed frame and radiation exposure. A total of 3,342 distances were assessed in 17 XT and 13 CT phantom scans. The cubic phantom showed mean distance errors of 0.33 mm (SD + -0.46 mm) for XT compared to 0.19 mm (SD + -0.83 mm) for CT scans (p = 0.0004) and a dispersion of 0.22 mm (XT) and 0.70 mm (CT). The dispersion was 0.36 mm with and 0.63 mm without a stereotactic frame (p < 0.0001). The mean Euclidean error was 0.72 mm (SD + -0.59 mm) in the skull phantom and 1.34 mm (SD + -0.82 mm) in the patient cohort. The effective dose was 0.65 mSv for the XT and 1.12 mSv for the CT. The accuracy of XT imaging in phantoms revealed a slightly lower accuracy but higher precision than the CT. The overall accuracy of XT was higher than that of the stereotactic frame allowing stereotactic localization with about half of the effective dose of a CT-scan.

Pedicle violation and Navigational errors in pedicle screw insertion using the intraoperative O-arm: A preliminary report

BackgroundUse of computer-assisted insertion of pedicle screws has some advantages owing to the reportedly decreased incidence of pedicle breach and clinical events. Registration-based methods based on preoperative computed tomography imaging, 2D fluoroscopy, and 3D fluoroscopy are the most popular, however each has its limitations. O-arm–based navigation, which uses intraoperative acquisition and registration of navigated images, may overcome many of these disadvantages. We set out to study the clinical accuracy and navigational accuracy for pedicle screw insertion using our recently acquired O-arm and present our preliminary findings. MethodsThe first 26 patients operated consecutively for L4-5 fusion were included in the study. O-arm–based navigation was used to insert the pedicle screws. Postoperative computed tomography images were acquired and assessed for pedicle breach and anterior cortical perforation. Planned trajectories of each screw were compared with the actual trajectories in the postoperative images to assess navigational accuracy in both axial and sagittal planes. ResultsA total of 104 screws were inserted. One screw (1%) breached the pedicle laterally. Nonsignificant anterolateral cortical perforations were noted in 7 screws (6.7%), all of which occurred at L5 level. The mean axial and sagittal navigational error was 2.3° (± 1.7) and 3.1° (± 2.3), respectively. There were no significant differences in the errors between L4 or L5 level. The occurrence of anterior perforation correlated with the degree of axial (P = .02) but not sagittal (P = .12) navigational error. There were no clinical events related to the screw insertion. ConclusionUse of O-arm–guided pedicle screw insertion was associated with low incidence of pedicle breach (1%) and a low range of navigational error in both sagittal and axial planes. Anterolateral vertebral body perforation was higher at L5 without any negative clinical events. Despite the high need for technical support, we found that O-arm was a very efficient tool for accurate pedicle screw insertion.

Computed Tomographic Imaging of Transcatheter Aortic Valve Replacement for Prediction and Prevention of Procedural Complications

Senile calcific aortic stenosis (AS) is the most common acquired valvular heart disease with an increasing prevalence attributable to an aging population. Survival is poor in patients with severe or critical AS, chiefly after the onset of symptomology that primarily includes angina, dyspnea, or syncope. On the onset of symptoms, mortality occurs at very high rates during the ensuing 2 to 3 years.1 Until recently, surgical aortic valve replacement represented the sole therapy that definitive reduced mortality and morbidity in patients with severe symptomatic AS, with medical therapy generally ineffective of these patients. Given the advanced age commonly associated with severe AS, a high proportion of these patients are denied surgical intervention because of multiple comorbidities and excessively high surgical risk.2 Recently, transcatheter aortic valve replacement (TAVR) has emerged as a novel disruptive technology that serves an alternative therapy to surgical AVR and has been shown to be an effective therapy in nonoperable and high-risk patients with severe symptomatic AS.3,4 TAVR was first described in humans by Cribier et al in 20025 by a transvenous approach delivered in an antegrade fashion. This technique requires a transseptal puncture and passage of the aortic stent valve across the mitral valve to the aortic position. Subsequently, array of alternative transvascular approaches have arisen, including transfemoral, transaortic, trans-subclavian, and aortic methods. Of these, the retrograde transarterial approach through the femoral artery, developed by Webb et al,6 has been the commonly used approach, with >60 000 such procedures performed worldwide to date. To date, the global experience with TAVR as documented in both single and multicenter registries as well as through multicenter trials have shown good clinical outcomes with improvement in hemodynamic and clinical status, establishing TAVR to be a feasible alternative therapy to traditional surgical aortic valve …

Evaluation of Automated 2D-3D Image Overlay System Utilizing Subtraction of Bone Marrow Image for EVAR: Feasibility Study

To evaluate the automated 2D-3D image overlay system ("3D Roadmap") for use during endovascular aneurysm repair (EVAR) in the hybrid operating theater. Datasets of preoperative CT images were modified to subtract dense bone marrow to improve the visualization of vasculature on the overlaid image, and allow for accurate navigation of the endovascular devices. The 3D-CT overlay image was registered on the 2D fluoroscopy image to mark the iliac crest and lumbar vertebrae on both images as landmarks. Arteriography was performed only twice to confirm the precision of the position of renal artery and the final evaluation. Twenty patients underwent EVAR with Medtronic Endurant, Gore Excluder, or COOK Zenith using "3D Roadmap". The origin of the renal artery and iliac bifurcation were registered with complete accuracy in 10 patients (50%). The lower renal artery deviated toward the cranial side less than 3 mm in six patients. In all cases, EVAR was successful, and completed with the volume of contrast material limited to 43.8 ± 3.1 mL. "3D Roadmap" was confirmed to be valuable for visualization of vessel origin in a fused image and for reduction of contrast material during EVAR.

Investigating the performance of a wrist stabilization device for image-guided percutaneous scaphoid fixation

Conventional navigated surgery relies on placement of a reference marker on the anatomy of interest. However, placement of such a marker is not readily feasible in small anatomic regions such as the scaphoid bone of the wrist. This study aimed to develop an alternative mechanism for patient tracking that could be used to perform navigated percutaneous scaphoid fixation. A prototype wrist stabilization device was developed to immobilize the scaphoid relative to a reference marker attached to the device. A position measurement system and 3D fluoroscopy were used to study the accuracy and limitations of wrist stabilization during simulated clinical usage with a cadaver specimen. Reference markers mounted on the device were used to measure intra-device motion. Radiometallic beads implanted in the scaphoid were used to measure patient-device motion. Navigated planning and guidance of scaphoid fixation were performed in five cadaver and eight "ideally immobilized" plastic specimens. Postoperative 3D fluoroscopy was used to assess the accuracy of navigated drilling. The average intra-device motion was 1.9 mm during load application, which was elastically recovered upon release of the load. Scaphoid motion relative to the reference marker was predominately rotational with an average displacement of 1.25 mm and 2.0°. There was no significant difference in the accuracy of navigated drilling between the cadaver specimens and the ideally immobilized group. The prototype wrist stabilization device meets the criteria for effective wrist stabilization. This study provides insight concerning proper use of the device to minimize scaphoid displacement and design recommendations to improve immobilization.

Abstract No. 242 - Comparing 2d angiography, 3D rotational angiography, and pre-procedural CT image fusion with 2d fluoroscopy for endovascular repair of thoraco-abdominal aortic aneurysm

Purpose To evaluate the feasibility of pre-procedural arterial phase computed tomography image fusion with intra-procedural fluoroscopy (or Image fusion: IF) road-mapping in endovascular repair of thoraco-abdominal aortic aneurysm (EVRTAAA) compared to current road-mapping methods (2D and 3D angiographies) in terms of x-ray exposure, injected contrast volume, and procedure time. Materials and Methods Single-institution prospective study (Internal institute approved), on 37 patients, informed written consent provided, and treated for EVRTAAA. All interventions were performed on the same angiographic system. Patients were consecutively placed in three groups in a seven-month period: “2D angiography” (2DA) (9 patients), “3D rotational angiography” (3DA) (14 patients), and “image fusion” (IF) (14 patients). Injected contrast volume, x-ray exposure (dose-area-product: DAP), and procedure time were recorded. To compare the groups in terms of the above measures and general patient characteristics, statistical tests using Fisher’s Exact, Kruskal-Wallis, and Mann-Whitney were performed. Results Patient characteristics and stenting types were similar between all three groups with no statistically significant differences (p-value>0.05). The IF group showed significant reduction (p-value Conclusion Image fusion road-mapping for EVRTAAA is feasible, and is associated to a statistically significant reduction in contrast volume and a trend towards DAP reduction while maintaining similar procedure time.

Image fusion for hybrid repair of dislocated superior mesenteric branch of a branched endovascular aortic graft

Recent advances in imaging technology allow the projection of volumetric imaging data from the preacquired computed tomography angiography over live fluoroscopy during interventions. This "fusion" technology is currently underused, although its application carries distinct advantages. We introduce a case in which fusion technology was used for the placement of two thoracic and one branched abdominal aortic endograft and to treat late dislocation of its side branch using a hybrid technique.

Feasibility of differential quantification of 3D temporomandibular kinematics during various oral activities using a cone-beam computed tomography-based 3D fluoroscopic method

Background/purposeThe measurement of mandibular kinematics is critical for studying the function of the temporomandibular joint (TMJ) and for relevant clinical applications. However, none of the existing methods allows the measurement of three-dimensional (3D) in vivo motion of the joint during dynamic functional movements without artifactual interference. The purpose of this study was to demonstrate the feasibility of a newly developed cone-beam computed tomography (CBCT)-based 3D fluoroscopic method in differentiating rigid-body kinematics of the TMJ during various functional activities. Materials and methodsOne healthy individual was asked to undergo a CBCT scan and fluoroscopic imaging of her mandible and maxilla during various functional activities. CBCT-based 3D fluoroscopy was used to measure the 3D kinematics of the TMJ. ResultsThe 3D rigid-body kinematics of the mandible, movement trajectories of the centers of the TMJ and the midpoint of the interincisal edge were measured during functional activities. ConclusionA new CBCT-based 3D fluoroscopic method was proposed and shown to be capable of quantitatively differentiating TMJ movement patterns among complicated functional activities. It also enabled a complete description of the rigid-body mandibular motion and descriptions of as many reference points as needed for future clinical applications. It will be helpful for dental practice and for a better understanding of the functions of the TMJ.

In vitro quantification of the performance of model-based mono-planar and bi-planar fluoroscopy for 3D joint kinematics estimation

Model-based mono-planar and bi-planar 3D fluoroscopy methods can quantify intact joints kinematics with performance/cost trade-off. The aim of this study was to compare the performances of mono- and bi-planar setups to a marker-based gold-standard, during dynamic phantom knee acquisitions. Absolute pose errors for in-plane parameters were lower than 0.6mm or 0.6° for both mono- and bi-planar setups. Mono-planar setups resulted critical in quantifying the out-of-plane translation (error<6.5mm), and bi-planar in quantifying the rotation along bone longitudinal axis (error<1.3°). These errors propagated to joint angles and translations differently depending on the alignment of the anatomical axes and the fluoroscopic reference frames. Internal-external rotation was the least accurate angle both with mono- (error<4.4°) and bi-planar (error<1.7°) setups, due to bone longitudinal symmetries. Results highlighted that accuracy for mono-planar in-plane pose parameters is comparable to bi-planar, but with halved computational costs, halved segmentation time and halved ionizing radiation dose. Bi-planar analysis better compensated for the out-of-plane uncertainty that is differently propagated to relative kinematics depending on the setup. To take its full benefits, the motion task to be investigated should be designed to maintain the joint inside the visible volume introducing constraints with respect to mono-planar analysis.

Patient-tailored plate for bone fixation and accurate 3D positioning in corrective osteotomy

A bone fracture may lead to malunion of bone segments, which gives discomfort to the patient and may lead to chronic pain, reduced function and finally to early osteoarthritis. Corrective osteotomy is a treatment option to realign the bone segments. In this procedure, the surgeon tries to improve alignment by cutting the bone at, or near, the fracture location and fixates the bone segments in an improved position, using a plate and screws. Three-dimensional positioning is very complex and difficult to plan, perform and evaluate using standard 2D fluoroscopy imaging. This study introduces a new technique that uses preoperative 3D imaging to plan positioning and design a patient-tailored fixation plate that only fits in one way and realigns the bone segments as planned. The method is evaluated using artificial bones and renders realignment highly accurate and very reproducible (d(err) < 1.2 ± 0.8 mm and φ(err) < 1.8° ± 2.1°). Application of a patient-tailored plate is expected to be of great value for future corrective osteotomy surgeries.