Fixation in cementless total knee arthroplasty is provided by osseous integration. Radiography, radiostereometric analysis (RSA), and magnetic resonance imaging (MRI) were used simultaneously to ...investigate fixation. Relationships between RSA‐measured implant micromotions and MRI‐evaluated osseous integration at the component–bone interface were assessed in 10 patients up to 6 months postoperation. Supine MRI (using multispectral imaging sequences) and RSA exams were performed to evaluate osseous integration and measure longitudinal migration, respectively. Inducible displacement was measured from standing RSA exams. Radiolucent lines were detected on conventional radiographs. Of 10 patients, 6 had fibrous membranes detected on MRI. No fluid or osteolytic interfaces were found, and no components were scored loose. Of 10 patients, 6 had radiolucent lines detected. Average maximum total point motion (MTPM) for longitudinal migration at 6 months was 0.816 mm (range 0.344–1.462 mm). Average MTPM for inducible displacement at 6 months was 1.083 mm (range 0.553–1.780 mm). Fictive points located in fibrous‐classified baseplate quadrants had greater longitudinal migration than fictive points located in baseplate quadrants with normal interfaces at 2 weeks (p = 0.031), 6 weeks (p = 0.046), and 3 months (p = 0.047), and greater inducible displacements at 3 months (p = 0.011) and 6 months (p = 0.045). Greater early micromotion may be associated with the presence of fibrous membranes at the component–bone interface. Clinical significance: This multimodal imaging study contributes knowledge of the fixation of modern cementless TKA, supporting the notion that osseous integration is important for optimal implant fixation.
A cohort study.
The aim of this study was to evaluate the clinical utility of Zero-Echo-Time (ZTE) magnetic resonance imaging (MRI) for the assessment of cervical neural foraminal stenosis (CNFS) ...through the comparison of inter-modality computed tomography (CT) and ZTE-MRI CNFS grade severity agreements.
Conventional MRI limited in its ability to provide direct visualization of cortical bone. The highly organized tissue structure of cortical bone results in very short T2 values that preclude acquisition of sufficient signal intensity and positive image contrast. ZTE imaging permits visualization of tissues with very short transverse relaxation times, and is capable of displaying images with CT-like contrast.
Thirty-four subjects were recruited from a clinical cohort of patients undergoing standard of care MRI and CT imaging for evaluation of CNFS. Standard of care CT imaging studies were obtained on all subjects within 6 months of their ZTE-MRI acquisition (mean time interval: 25.3 ± 54.1 days; median: 0 days). ZTE-MRI and CT imaging studies were evaluated and severity of CNFS was graded on a scale from 0 to 5 (0 = none; 5 = severe). Weighted-kappa statistics were used to assess agreement between ZTE and CT grades of CNFS on both sides (right and left) of each motion segment. Ordinal logistic mixed-effects regression analyses evaluated the effects of inter-modality position differences (flexion-extension curvature) on inter-modality differences in CNFS grade.
Substantial agreement (κ = 0.72) was found between ZTE- and CT-based grades of CNFS. Significant inter-modality differences in cervical spine curvature were found for all motion segments, except C2-3 and C3-4 (P < 0.05). However, no significant relationship was found between inter-modality differences in curvature, and inter-modality differences in CNFS grade for any motion segment (P = 0.28).
Results of the current study suggest that ZTE-MRI is well-suited for the evaluation of CNFS and may have the potential to obviate the need for concurrent CT scans in some cases.
2.
Background:
Femoroacetabular impingement syndrome (FAIS) is a common disorder of the hip resulting in groin pain and ultimately osteoarthritis. Radiologic assessment of FAI morphologies, which may ...present with overlapping radiologic features of hip dysplasia, often requires the use of computed tomography (CT) for evaluation of osseous abnormality, owing to the difficulty of direct visualization of cortical and subchondral bone with conventional magnetic resonance imaging (MRI). The use of a zero echo time (ZTE) MRI pulse sequence may obviate the need for CT by rendering bone directly from MRI.
Purpose/Hypothesis:
The purpose was to explore the application of ZTE MRI to the assessment of osseous FAI and dysplasia morphologies of the hip. It was hypothesized that angular measurements from ZTE images would show significant agreement with measurements obtained from CT images.
Study Design:
Cohort study (diagnosis); Level of evidence, 2.
Methods:
Thirty-eight hips from 23 patients were imaged with ZTE MRI and CT. Clinically relevant angular measurements of hip morphology were made in both modalities and compared to assess agreement. Measurements included coronal and sagittal center-edge angles, femoral neck-shaft angle, acetabular version (at 1-, 2-, and 3-o’clock positions), Tönnis angle, alpha angle, and modified-beta angle. Interrater agreement was assessed for a subset of 10 hips by 2 raters. Intermodal agreement was assessed on the complete cohort and a single rater.
Results:
Interrater agreement was demonstrated in both CT and ZTE, with intraclass correlation coefficient values ranging from 0.636 to 0.990 for ZTE and 0.747 to 0.983 for CT, indicating “good” to “excellent” agreement. Intermodal agreement was also shown to be significant, with intraclass correlation coefficients ranging from 0.618 to 0.904.
Conclusion:
Significant agreement of angular measurements for hip morphology exists between ZTE MRI and CT imaging. ZTE MRI may be an effective method to quantitatively evaluate osseous hip morphology.
Magnetic resonance imaging (MRI) has historically been avoided for the routine clinical evaluation of metal implants at many clinical centers due to the presence of artifact that creates in‐plane and ...through‐plane distortions and signal intensity voids in generated images. However, when the image acquisition parameters are appropriately modified and advanced multi‐spectral pulse sequences are used, high‐quality diagnostic images can be generated and may be used for diagnosing patients with suspected periprosthetic pathology. MRI provides superior soft‐tissue contrast and excellent sensitivity for mobile water and is, therefore, a valuable tool in the evaluation of these patients, given the increasing prevalence of arthroplasty within the general population. Knowledge of expected normal postoperative appearance in patients with total hip arthroplasty, total knee arthroplasty, and total shoulder arthroplasty facilitates the detection of abnormal findings in this population, as does familiarity with common pathologic conditions encountered in the periprosthetic region. This review article will provide background information regarding the presence of image artifacts, methods to reduce the artifacts, and application of MRI at 1.5 T for evaluating common complications in subjects with total knee arthroplasty, total hip arthroplasty, and total shoulder arthroplasty.
Background
Diffusion‐weighted imaging (DWI) provides quantitative measurement of random water displacement in tissue as calculated by the apparent diffusion coefficient (ADC). While heavily utilized ...in stroke and oncology applications, DWI is a promising tool to map microstructural changes in musculoskeletal applications including evaluation of synovial reactions resulting from total hip arthroplasty (THA). One major challenge facing the application of DWI in THA is the significant artifacts related to the conventional echo‐planar imaging (EPI) readout used. Multispectral imaging (MSI) techniques, including the multiacquisition with variable resonance image combination (MAVRIC), have been shown to effectively reduce metallic susceptibility artifacts around total joint replacements to render clinically useful images. Recently, a 2D periodically rotated overlapping parallel line with enhanced reconstruction (PROPELLER) FSE acquisition that incorporates a diffusion preparation pulse with 2D‐MAVRIC has been developed to mitigate both distortion and dropout artifacts. While there have been some preliminary assessments of DWI‐MAVRIC, the repeatability of DWI‐MAVRIC and the effects of key parameters, such as the number of spectral bins, are unknown.
Purpose
To evaluate the quantitative accuracy of DWI‐MAVRIC as compared to conventional diffusion sequences.
Methods
A diffusion phantom with different reference diffusivities (ADC = 113–1123 μm2/s) was used. Scans were performed on two 1.5T MRI scanners. DWI‐EPI and DWI‐MAVRIC were acquired in both the axial and coronal planes. Three spatial offsets (0 cm, 10 cm left, and 10 cm right off iso‐center) were used to evaluate effects of off‐isocenter positioning. To assess intraday and interday repeatability, DWI‐EPI and DWI‐MAVRIC acquisitions were repeated on one scanner at same‐day and 9‐month intervals. To assess inter‐scanner repeatability, DWI‐EPI and DWI‐MAVRIC acquisitions were compared between two scanners. ADC maps were generated with and without gradient nonlinearity correction (GNC). Linear regression, correlation, and error statistics were determined between calculated and reference ADC values. Bland‐Altman plots were generated to evaluate intraday, interday, and interscanner repeatability.
Results
DWI‐MAVRIC had excellent correlation to reference values but at reduced linearity (r = 1.00, slope = 0.91–0.94) as compared to DWI‐EPI (r = 1.00, slope = 0.99–1.01). A greater than 5% ADC bias was observed at the lowest ADC values, predominantly in the DWI‐MAVRIC scans. ADC values did not vary with DWI‐MAVRIC parameters. DWI‐EPI acquisitions had intraday, interday, and interscanner repeatability of 3.18 μm2/s, 19.2 μm2/s, and 20.2 μm2/s, respectively. DWI‐MAVRIC acquisitions had inferior intraday, interday, and interscanner repeatability of 13.3 μm2/s, 44.7 μm2/s, 110 μm2/s, respectively. Lower ADC errors were found at isocenter, as compared to the left and right positions. GNC reduced the absolute error by 0.31% ± 0.89%, 3.6% ± 1.4%, 0.65% ± 2.4% for the center, left, and right positions, respectively.
Conclusions
DWI‐MAVRIC provides good linearity with respect to reference values and good intra‐ and interday repeatability.
MRI is predictive of adverse local tissue reactions (ALTRs) after THA but how MRI directly relates to implant surface wear, fretting, and trunnion corrosion at different articulations between implant ...components remains unclear. MRI generates high-contrast images to display soft tissues around arthroplasty and may provide a surgeon the means to distinguish and differentiate host-related synovial patterns as a response to either polyethylene wear or metal wear and corrosion products.
The purposes of this study were (1) to correlate findings from MRI in patients who have undergone THA with direct assessment of implant wear, corrosion, and fretting from retrieved components; and (2) to distinguish the unique synovial responses on MRI in patients who have undergone THA based on bearing materials.
In this prospective study, patients undergoing THA (181 patients, 187 hips) with metal-on-metal (MoM), hip resurfacing (HRA), metal-on-polyethylene (MoP), ceramic-on-polyethylene, ceramic-on-ceramic, or modular neck designs having revision surgery (between October 2013 and June 2017) underwent preoperative MRI. A single reader blinded to the bearing surface made an assessment of the synovial response (Gwet's AC1, 0.65-0.97); these data were compared with semiquantitative histology of tissue samples by a single reader (Gwet's AC1, 0.92) and semiquantitative wear, corrosion, and fretting analysis of retrieved components using Goldberg scoring (Gwet's AC1, 0.60-0.79). Direct noncontact measurements of implant wear were also made. Correlations and analyses of variance were used to assess associations between metrics and differences by implant type, respectively.
Correlations were found between MRI synovial thickness with severity of fretting and corrosion damage of the female head-neck trunnion of femoral stems in modular designs (ρ = 0.26 95% confidence interval {CI}, 0.12-0.39; p = 0.015, n = 185) and ALTR grade and volumetric wear in MoM bearings (ρ = 0.93 95% CI, 0.72-0.98; p < 0.001, n = 10). MRI synovial thickness was highest in patients identified with aseptic lymphocyte-dominated vasculitis-associated lesions and diffuse tissue necrosis. On MRI, MoP hips demonstrated a distinct polymeric synovial response, whereas HRA, MoM, and modular hips more commonly demonstrated ALTR. Hips classified as having a polymeric synovial response on MRI had a greater number of particles present in tissue samples.
In this study, we demonstrated that MRI of THA can distinguish synovial responses that reflect the bearing type of the implanted THA and correlate to direct measurements of implant wear, corrosion, and fretting and histologic assessment of wear particles in periprosthetic tissues. MRI provides a means of direct, noninvasive visualization of the host-generated synovial response. Patients presenting with painful arthroplasties may be evaluated for the cause of their discomfort, specifically highlighting any concerning synovial reactions that would warrant more prompt surgical intervention. Future studies would benefit from a prospective evaluation of different implants to assess the natural longitudinal history of arthroplasty complications, including the development and prevalence of ALTR across bearing constructs.
Level III, diagnostic study.
Abstract
Context
Many individuals at high risk for osteoporosis and fragility fracture are never screened by traditional methods. Opportunistic use of imaging obtained for other clinical purposes is ...required to foster identification of these patients.
Objective
The aim of this pilot study was to evaluate texture features as a measure of bone fragility, by comparing clinically acquired magnetic resonance imaging (MRI) scans from individuals with and without a history of fragility fracture.
Methods
This study retrospectively investigated 100 subjects who had lumbar spine MRI performed at our institution. Cases (n = 50) were postmenopausal women with osteoporosis and a confirmed history of fragility fracture. Controls (n = 50) were age- and race-matched postmenopausal women with no known fracture history. Trabecular bone from the lumbar vertebrae was segmented to create regions of interest within which a gray level co-occurrence matrix was used to quantify the distribution and spatial organization of voxel intensity. Heterogeneity in the trabecular bone texture was assessed by several features, including contrast (variability), entropy (disorder), and angular second moment (homogeneity).
Results
Texture analysis revealed that trabecular bone was more heterogeneous in fracture patients. Specifically, fracture patients had greater texture variability (+76% contrast; P = 0.005), greater disorder (+10% entropy; P = 0.005), and less homogeneity (−50% angular second moment; P = 0.005) compared with controls.
Conclusions
MRI-based textural analysis of trabecular bone discriminated between patients with known osteoporotic fractures and controls. Further investigation is required to validate this promising methodology, which could greatly expand the number of patients screened for skeletal fragility.
Magnetic resonance imaging (MRI) can provide accurate and non‐invasive diagnoses of lower extremity injuries in athletes. Sport‐related injuries commonly occur in and around the knee and can affect ...the articular cartilage, patellar tendon, hamstring muscles, and bone. Sports medicine physicians utilize MRI to evaluate and diagnose injury, track recovery, estimate return to sport timelines, and assess the risk of recurrent injury. This article reviews the current literature and describes novel developments of quantitative MRI tools that can further advance our understanding of sports injury diagnosis, prevention, and treatment while minimizing injury risk and rehabilitation time. Innovative approaches for enhancing the early diagnosis and treatment of musculoskeletal injuries in basketball players span a spectrum of techniques. These encompass the utilization of T2, T1ρ, and T2* quantitative MRI, along with dGEMRIC and Na‐MRI to assess articular cartilage injuries, 3D‐Ultrashort echo time MRI for patellar tendon injuries, diffusion tensor imaging for acute myotendinous injuries, and sagittal short tau inversion recovery and axial long‐axis T1‐weighted, and 3D Cube sequences for bone stress imaging. Future studies should further refine and validate these MR‐based quantitative techniques while exploring the lifelong cumulative impact of basketball on players' knees.
Level of Evidence
5
Technical Efficacy
Stage 2
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