Dual-energy CT and ceramic or titanium prostheses material reduce CT artifacts and provide superior image quality of total knee arthroplasty

Imaging in osteoarticular infection in adults

BACKGROUND

Osteoarticular infections are uncommon and required a multimodal approach for diagnosis. Imaging forms an important component of this multimodal approach.

OBJECTIVES

In this narrative review, we describe the different imaging modalities, features of osteoarticular infections present on these imaging approaches and recommendations for which imaging modality should be considered in different types of osteoarticular infections.

SOURCES

This narrative review was based on literature review from PubMed and was limited to bacterial infections in adult patients.

CONTENT

Imaging modalities include modalities that provide information on the anatomy or radionuclide imaging that provides information about the metabolic activity of the area of interest. Anatomical imaging includes plain radiographs (X-ray), computed tomography, and magnetic resonance imaging. Radionuclide approaches include three-phase bone scintigraphy, gallium scans, white blood cell scintigraphy, and 18F-fluorodeoxy-glucose positron emission tomography. The optimal radiological modality for diagnosis is influenced by multiple factors, including infection location, presence of metalware, timing of infection from any preceding surgery or fracture, antibiotic use, and patient comorbidities. Local availability of scanning modality, tracer supply, technical expertise, and patient access also influences choice.

IMPLICATIONS

A collaborative approach with imaging, pathology and clinical input in a multidisciplinary setting is paramount for the diagnosis of osteoarticular infections. Increasing research and improvements in technology will further improve the utility and accuracy of imaging approaches for imaging in osteoarticular infections.

Combining iterative metal artifact reduction and virtual monoenergetic images severely reduces hip prosthesis-associated artifacts in photon-counting detector CT

Aim of this study was to assess the impact of virtual monoenergetic images (VMI) in combination and comparison with iterative metal artifact reduction (IMAR) on hip prosthesis-associated artifacts in photon-counting detector CT (PCD-CT). Retrospectively, 33 scans with hip prosthesis-associated artifacts acquired during clinical routine on a PCD-CT between 08/2022 and 09/2022 were analyzed. VMI were reconstructed for 100-190 keV with and without IMAR, and compared to polychromatic images. Qualitatively, artifact extent and assessment of adjacent soft tissue were rated by two radiologists using 5-point Likert items. Quantitative assessment was performed measuring attenuation and standard deviation in most pronounced hypodense and hyperdense artifacts, artifact-impaired bone, muscle, vessels, bladder and artifact-free corresponding tissue. To quantify artifacts, an adjusted attenuation was calculated as the difference between artifact-impaired tissue and corresponding tissue without artifacts. Qualitative assessment improved for all investigated image reconstructions compared to polychromatic images (PI). VMI_100keV in combination with IMAR achieved best results (e.g. diagnostic quality of the bladder: median PI: 1.5 (range 1-4); VMI_100keV+IMAR: 5 (3-5); p < 0.0001). In quantitative assessment VMI_100keV with IMAR provided best artifact reduction with an adjusted attenuation closest to 0 (e.g. bone: PI: 302.78; VMI_100keV+IMAR: 51.18; p < 0.0001). The combination of VMI and IMAR significantly reduces hip prosthesis-associated artifacts in PCD-CT and improves the diagnostic quality of surrounding tissue.

Dual-Energy CT for Detecting Painful Knee Prosthesis Loosening

Background Dual-energy CT (DECT) is an alternative to radiography and single-energy CT (SECT) for detecting prosthesis-related complications. Purpose To compare the diagnostic performance of DECT, SECT, and radiography for knee prosthesis loosening, with use of surgery or imaging follow-up reference standards. Materials and Methods In this prospective single-center study from December 2018 to June 2021, participants with unilateral painful knee prostheses underwent radiographic, SECT, and DECT imaging. Five blinded readers, four radiologists, and one orthopedic surgeon evaluated the images. Prosthesis loosening was diagnosed by a periprosthetic lucent zone greater than 2 mm. The sensitivity, specificity, and area under the receiver operating characteristic curve (AUC) of each method were determined and compared with use of a multireader multicase analysis. Results There were 92 study participants (mean age ± SD, 70 years ± 9.4; 67 women) evaluated. Tibial and femoral loosening were diagnosed in 47 and 24 participants, respectively. For the tibia, mean sensitivity and specificity for arthroplasty loosening were 88% and 91%, respectively, for DECT, 73% and 78% for SECT, and 68% and 81% for radiography. For the tibia, DECT demonstrated similar diagnostic performance (AUC, 0.90) to SECT (AUC: 0.90 vs AUC: 0.87, respectively; P = .13) but was superior to radiography (AUC: 0.90 vs AUC: 0.82; P = .002). Overall diagnostic performance of DECT (AUC, 0.87) for the femur was superior to both SECT and radiography (P < .001). Conclusion Dual-energy CT had generally better diagnostic performance in detecting loosening of tibial and femoral components after total knee arthroplasty compared with single-energy CT or radiography. Clinical trial registration no. 2942 © RSNA, 2022.

Influence of Scan Parameters of Single and Dual-Energy CT Protocols in Combination with Metal Artifact Suppression Algorithms for THA: An ex Vivo Study

BACKGROUND

Metal artifacts caused by hip arthroplasty stems limit the diagnostic value of computed tomography (CT) in the evaluation of periprosthetic fractures or implant loosening. The aim of this ex vivo study was to evaluate the influence of different scan parameters and metal artifact algorithms on image quality in the presence of hip stems.

METHODS

Nine femoral stems, 6 uncemented and 3 cemented, that had been implanted in subjects during their lifetimes were exarticulated and investigated after death and anatomical body donation. Twelve CT protocols consisting of single-energy (SE) and single-source consecutive dual-energy (DE) scans with and without an iterative metal artifact reduction algorithm (iMAR; Siemens Healthineers) and/or monoenergetic reconstructions were compared. Streak and blooming artifacts as well as subjective image quality were evaluated for each protocol.

RESULTS

Metal artifact reduction with iMAR significantly reduced the streak artifacts in all investigated protocols (p = 0.001 to 0.01). The best subjective image quality was observed for the SE protocol with a tin filter and iMAR. The least streak artifacts were observed for monoenergetic reconstructions of 110, 160, and 190 keV with iMAR (standard deviation of the Hounsfield units: 151.1, 143.7, 144.4) as well as the SE protocol with a tin filter and iMAR (163.5). The smallest virtual growth was seen for the SE with a tin filter and without iMAR (4.40 mm) and the monoenergetic reconstruction of 190 keV without iMAR (4.67 mm).

CONCLUSIONS

This study strongly suggests that metal artifact reduction algorithms (e.g., iMAR) should be used in clinical practice for imaging of the bone-implant interface of prostheses with either an uncemented or cemented femoral stem. Among the iMAR protocols, the SE protocol with 140 kV and a tin filter produced the best subjective image quality. Furthermore, this protocol and DE monoenergetic reconstructions of 160 and 190 keV with iMAR achieved the lowest levels of streak and blooming artifacts.

LEVEL OF EVIDENCE

Diagnostic Level III. See Instructions for Authors for a complete description of levels of evidence.

Metallic Artifact Reduction in Midfacial CT Scans Using Patient-Specific Polymer Implants Enhances Image Quality

Midfacial reconstruction after tumor resection surgery is commonly conducted by using autologous bone grafts or alloplastic implants. Titanium is the most frequently used osteosynthesis material in these cases but causes disturbing metallic artifacts in CT imaging. The purpose of this experimental study was to evaluate whether the use of midfacial polymer implants reduces metallic artifacts in CT imaging to improve image quality. Zygomatic titanium (n = 1) and polymer (n = 12) implants were successively implanted in a human skull specimen. Implants were analyzed for their effect on Hounsfield Unit values (streak artifacts) and virtual growth in CT images (blooming artifacts) as well as image quality. Multi-factorial ANOVA and Bonferroni's post hoc test were used. Titanium (173.7 HU; SD ± 5.1) and hydroxyapatite containing polymers (155.3 HU; SD ± 5.9) were associated with significantly more streak artifacts compared to all other polymer materials. There was no significant difference in blooming artifacts between materials. The metallic artifact reduction algorithm showed no significant difference. Image quality was slightly better for polymer implants compared to titanium. Personalized polymer implants for midfacial reconstruction significantly reduce metallic artifacts in CT imaging which improves image quality. Hence, postoperative radiation therapy planning and radiological tumor aftercare around the implants are facilitated.

Comparison of Image Quality and Radiation Dose Between Single-Energy and Dual-Energy Images for the Brain With Stereotactic Frames on Dual-Energy Cerebral CT

Background

Preoperative stereotactic planning of deep brain stimulation (DBS) using computed tomography (CT) imaging in patients with Parkinson's disease (PD) is of clinical interest. However, frame-induced metal artifacts are common in clinical practice, which can be challenging for neurosurgeons to visualize brain structures.

Objectives

To evaluate the image quality and radiation exposure of patients with stereotactic frame brain CT acquired using a dual-source CT (DSCT) system in single- and dual-energy modes.

Materials and Methods

We included 60 consecutive patients with Parkinson's disease (PD) and randomized them into two groups. CT images of the brain were performed using DSCT (Group A, an 80/Sn150 kVp dual-energy mode; Group B, a 120 kVp single-energy mode). One set of single-energy images (120 kVp) and 10 sets of virtual monochromatic images (50-140 keV) were obtained. Subjective image analysis of overall image quality was performed using a five-point Likert scale. For objective image quality evaluation, CT values, image noise, signal-to-noise ratio (SNR), and contrast-to-noise (CNR) were calculated. The radiation dose was recorded for each patient.

Results

The mean effective radiation dose was reduced in the dual-energy mode (1.73 mSv ± 0.45 mSv) compared to the single-energy mode (3.16 mSv ± 0.64 mSv) (p < 0.001). Image noise was reduced by 46-52% for 120-140 keV VMI compared to 120 kVp images (both p < 0.01). CT values were higher at 100-140 keV than at 120 kVp images. At 120-140 keV, CT values of brain tissue showed significant differences at the level of the most severe metal artifacts (all p < 0.05). SNR was also higher in the dual-energy mode 90-140 keV compared to 120 kVp images, showing a significant difference between the two groups at 120-140 keV (all p < 0.01). The CNR was significantly better in Group A for 60-140 keV VMI compared to Group B (both p < 0.001). The highest subjective image scores were found in the 120 keV images, while 110-140 keV images had significantly higher scores than 120 kVp images (all p < 0.05).

Conclusion

DSCT images using dual-energy modes provide better objective and subjective image quality for patients with PD at lower radiation doses compared to single-energy modes and facilitate brain tissue visualization with stereotactic frame DBS procedures.

No difference in the anteroposterior stability between the GRADIUS and multi-radius designs in total knee arthroplasty

BACKGROUND

This retrospective study aimed to compare stability and clinical and radiological outcomes of total knee arthroplasty (TKA) for the GRADIUS and multi-radius femoral designs after minimum of two-year follow-up.

METHODS

A total of 142 patients who underwent TKA using ATTUNE posterior stabilized (PS) implants (68 patients, GRADIUS group) or Persona PS implants (74 patients, multi-radius group) for degenerative osteoarthritis were included. After an average of 2-year follow-up, the anteroposterior (AP) stability at 30°, 60°, and 90° was measured using KT 2000 device and compared between the two groups. The clinical outcome measurements included range of motion (ROM) of the knee, patient-reported outcomes and anterior knee pain (AKP). For the clinical evaluation of mid-flexion instability, pain was evaluated using the visual analog scale (VAS) score recorded during climbing up or going down stairs. The radiolucent lines on knee radiographs obtained at final follow-up were evaluated and compared between two groups.

RESULTS

The average AP stability at 30° knee flexion was 5.7 mm in the GRADIUS group and 5.9 mm in the multi-radius group; however, the difference was not significant. The AP stability at 60° and 90° knee flexion was also similar in both groups. There were no significant differences in the ROM, patient-reported outcomes at follow-up, incidence of AKP and VAS scores between the two groups. There were no differences in the incidence of radiolucency around the components between the two groups.

CONCLUSION

The GRADIUS design did not show any advantage with respect to the stability or clinical outcomes compared with the multi-radius design in TKA.

From the Performance to the Essence: The Biological Mechanisms of How Tantalum Contributes to Osteogenesis

Despite the brilliant bioactive performance of tantalum as an orthopedic biomaterial verified through laboratory researches and clinical practice in the past decades, scarce evidences about the essential mechanisms of how tantalum contributes to osteogenesis were systematically discussed. Up to now, a few studies have uncovered preliminarily the biological mechanism of tantalum in osteogenic differentiation and osteogenesis; it is of great necessity to map out the panorama through which tantalum contributes to new bone formation. This minireview summarized current advances to demonstrate the probable signaling pathways and underlying molecular cascades through which tantalum orchestrates osteogenesis, which mainly contain Wnt/β-catenin signaling pathway, BMP signaling pathway, TGF-β signaling pathway, and integrin signaling pathway. Limits of subsistent studies and further work are also discussed, providing a novel vision for the study and application of tantalum.

A New Diagnostic Approach for Periprosthetic Acetabular Fractures Based on 3D Modeling: A Study Protocol

Periprosthetic acetabular fractures after total hip arthroplasty (THA) are mostly related to low energy trauma reduced bone quality. CT-scan is widely used to evaluate acetabular fractures, however, metal artifacts produced prosthetic implants limit the visualization of the articular surface and bone loss assessment. 3D modeling software allows us to creating tridimensional images of the bony surface, removing the metallic implants trough image segmentation. We highlight the use of 3D modeling and rapid prototyping (3D printing) for the diagnostic process of periprosthetic acetabular fracture around THA. 3D modeling software was used to improve the assessment of fracture morphology and bone quality. Moreover, the 3D images were printed in a real-life size model and used for preoperative implant templating, sizing and surgical simulation.

Intra- and interobserver reliability and agreement in three-dimensional computed tomography measurements of component positions after total knee arthroplasty

BACKGROUND

Accurate evaluation of the postoperative position of total knee arthroplasty (TKA) components is crucial in the analysis of the association of alignments with clinical outcomes. The aim of this study was to investigate the reliability of measurements of component positions after TKA using three-dimensional computed tomography (3D-CT) reconstruction.

METHODS

Two independent orthopedic surgeons (an attending surgeon and a fellow) examined 30 knees after primary TKA. The coronal, sagittal, and rotational positions of the femoral and tibial components were measured twice at an interval of six weeks on 3D-CT images reconstructed using ZedKnee software. Mean intra- and interobserver differences of measured angles were calculated, and the intra- and interobserver reliability was determined using intraclass correlation coefficients (ICCs), with agreement assessed by Bland-Altman analysis.

RESULTS

The mean intraobserver difference between alignment measurements for femoral and tibial components was <2° (range 0.23-1.17°) and the mean interobserver difference was <1° (range 0.22-0.97°). The intra- and interobserver ICCs were >0.8 for all component positions. The only systematic bias found in the intra- and interobserver agreements occurred for the sagittal position of the femoral component.

CONCLUSION

Three-dimensional-CT measurements of component positions after TKA showed good intra- and interobserver reliability for the femoral and tibial components in coronal, sagittal and rotational positions. The intra- and interobserver agreements were favorable for all but the sagittal position of the femur. These results suggest that 3D-CT can be used to evaluate the alignment of all TKA components except for the sagittal position of the femur.

Non-Destructive Testing of Ceramic Knee Implants Using Micro-Computed Tomography

BACKGROUND

Because of the accumulated numbers and the increasing rate of knee replacement surgeries larger numbers of revision cases are likely. Although the success rate of knee arthroplasties is high, complications like the loosening of the implant necessitate subsequent treatments. Therefore, new concepts such as metal-free ceramic implants are necessary, for example, using zirconium dioxide (ZrO₂). Several studies showed that the strength of ceramic ZrO₂ implants is equivalent to cobalt-chromium components.

METHODS

Non-destructive testing remains challenging due to the high density (6 g/cm³) of ZrO₂. In this feasibility study, we investigated 8 tibial and 8 femoral implants respectively using an industrial X-ray micro-computed tomography (XCT) system at a voxel size of 100 μm. We established a non-destructive testing protocol for ceramic knee implants optimizing scanning parameters and sample orientation using CT simulations. Finally, we used an iterative artifact reduction procedure for beam hardening correction.

RESULTS

The results show that corrected image data enable the non-destructive inspection of high-density components. In this sample, none of the investigated components show any internal defects like pores or cracks. In general, XCT is a major imaging method that is able to provide a 3-dimensional representation of higher dense objects that allows the inspection of metal or ceramic knee implants. Even though we established an optimized scanning routine for tibial and femoral ceramic components, it is not possible to completely eliminate scanning artifacts of XCT.

CONCLUSION

Altogether, after visual inspection, none of the beam-hardening corrected XCT data sets for femoral and tibial implants showed any defects, that is, no inclusions, cracks, or pores were detected. XCT test is therefore an essential addition to the fatigue testing since it is the only non-destroying testing method.

Radiological Imaging Evaluation of the Failing Total Hip Replacement

Total hip replacements (THR) have been performed in the UK from the 1960s and since then we have seen surgical techniques, the design of implants, and imaging modalities rapidly develop. This paper will aim to review the different complications and imaging appearance which help to evaluate each problem. As for all investigations for bone and joints, a radiograph is the first imaging to be performed for any patient with a THR and can detect a majority of complications. CT is relatively low-cost, simple to perform and easily available making it an excellent tool to supplement radiographs when trying to evaluate a hip prosthesis. Single photon emission computed tomography with CT (SPECT-CT) is an emerging modality which has shown to combine the sensitivity that bone scintigraphy offers with the high specificity of CT. SPECT imaging also has the advantage of showing the bone's metabolic activity and is less prone to metal artifact than Magnetic resonance imaging (MRI). MRI has evolved to become an important diagnostic tool for the evaluation of THR in the post-operative period. Optimized pulse sequences and metal artifact reduction techniques have made MRI a useful tool in diagnosis of soft tissue abnormalities and is particularly useful in identifying adverse local tissue reactions in metal on metal implants. CT and MRI are accurate in identifying the diagnosis of most causes of THR complications except infection. Research confirms that leukocyte-marrow scintigraphy is the modality of choice for accurately diagnosing prosthetic joint infection and reassures us of its superiority over other nuclear medicine imaging. However, due to the limited availability and increased costs when performing leukocyte-marrow scintigraphy, CT and SPECT-CT would be a more preferred option when suspecting prosthesis infection. Ultrasound (US) has a limited role in the assessment of most THR complications but can be useful to identify peri-prosthetic fluid collections and the presence of soft tissue sinus tracts. Being aware of the imaging modalities that are available to orthopedic surgeons, and discussing these challenging cases with specialist radiologists will enable optimal management of THR complications.