What’s new in MSK Imaging – August 2020

1 year ago
Diagnostic Performance of Magnetic Resonance Imaging for Detecting Meniscal Ramp Lesions in Patients With Anterior Cruciate Ligament Tears: A Systematic Review and Meta-analysis.

Koo B, Lee SH, Yun SJ, Song JG. Diagnostic performance of magnetic resonance imaging for detecting meniscal ramp lesions in patients with anterior cruciate ligament tears: a systematic review and meta-analysis. The American Journal of Sports Medicine. 2019 Nov 4:0363546519880528.


Background: Ramp lesion is the tear, disruption or separation of the peripheral  menisco-capsular attachments of the posterior horn of the medial meniscus (MM). ACL reconstruction without ramp lesion repair may fail to restore normal joint kinematics. Ramp lesions cause anterior translation and external rotational laxity (knee instability), extension of the posterior horn of the medial meniscus tear, and accelerated degeneration of both the meniscus and the articular cartilage. However, the diagnostic accuracy of magnetic resonance imaging (MRI) for detecting ramp lesions has a wide range.

Questions: What is the sensitivity and specificity of MRI in diagnosing ramp lesion in patients with ACL tear?

Design: Systematic review and meta-analysis.

Participants: 883 patients with ACL tear and reconstruction (9 studies from 8 articles).

Exclusion criteria: (1) case report or case series; (2) review articles, guidelines, consensus statements, letters, editorials, and conference abstracts; (3) studies not pertaining to the field of interest; (4) studies not performed on live humans (animal or cadaveric studies), and (5) studies with insufficient data for a 2 × 2 table.

Method: A literature search of PubMed, EMBASE, and the Cochrane Library was performed based on the revised guidelines for the PRISMA DTA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses of Diagnostic Accuracy Studies) statement. Diagnostic performance studies using MRI as the index test and arthroscopy as the reference standard for ramp lesion were included. Bivariate and hierarchical summary receiver operating characteristic modeling was used to evaluate the diagnostic performance. Meta-regression analyses were performed to identify potential sources of heterogeneity.

Main Results: The summary sensitivity, summary specificity, and area under the hierarchical summary receiver operating characteristic for ramp lesion were 0.71 (95% CI, 0.59-0.81), 0.94 (95% CI, 0.88-0.97), and 0.90 (95% CI, 0.87-0.92), respectively. Among the potential covariates, magnet strength (P < .01), patient knee position (P = .04), and MRI interpreter (P = .04) were associated with heterogeneity in terms of sensitivity, whereas magnet strength (P = .03) was associated with heterogeneity in terms of specificity.

Conclusion: MRI demonstrated moderate sensitivity and excellent specificity for diagnosing ramp lesion. Routine arthroscopic assessment is recommended for the presence of ramp lesion, regardless of whether it is suspected on MRI. Further clinicoradiological studies of diagnostic algorithms are needed for identifying ramp lesion, including high-resolution MRI with appropriate knee position.

Commentary: We congratulate the authors for publishing their extensive work in the domain of MM tears in the setting of ACL injury. It must be noted that arthroscopy is not a gold standard for accuracy assessment of meniscocapsular injuries, especially in the setting of retrospective data. Secondly, it is quite common to see a corner fracture or longitudinal tear of the medial meniscus in the setting of ACL injury. Meniscocapsular sprain or separations often associated with such tears are difficult to distinguish on MRI. In addition, since the arthroscopy for ACL reconstruction is often delayed avoiding issues of stiffness from early reconstruction and for other unforeseeable reasons, such accuracy assessment may not be valid for use in the current routine clinical practice.


Epidemiology and Imaging Classification of Pediatric Cervical Spine Injuries: 12- Year Experience at a Level 1 Trauma Center

Beckmann NM, Chinapuvvula NR, Zhang X, West OC. Epidemiology and imaging classification of pediatric cervical spine injuries: 12-year experience at a Level 1 Trauma Center. American Journal of Roentgenology. 2020 Jun;214(6):1359-68.


Questions: What is the rate of cervical spine injuries in pediatric population with blunt trauma? What are the types of cervical spine injuries in this population?

Design: Retrospective study

Participants: Two hundred thirty-five patients who were 16 years old or younger with a diagnosis of cervical spine injury in the trauma registry between July 2006 and June 2018.

Exclusion criteria: Patients presenting without cross-sectional imaging (CT or MRI) for review and patients with penetrating trauma of the cervical spine were excluded.

Method: The presenting CT scans, MR images or both reviewed by a musculoskeletal fellowship trained radiologist with 13 years of experience, and the injury level and type was recorded. If presenting radiographs were obtained, the report from the radiographs was reviewed and compared with injury findings on CT or MR images.

Main Results:  The frequency of isolated upper cervical spine injuries was 73% in patients younger than 3 years old, 48% in patients 3-8 years old, and 29% in patients older than 8 years old. Seventy-one percent of occipital condyle fractures were avulsions, and 26% of dens fractures were avulsions. Type II dens fractures were found only in patients older than 8 years old. Type I and III dens fractures were almost exclusively in patients 8 years old or younger. Injuries classified as AO Spine types A, B, and C comprised 65.6%, 17.2%, and 17.2% of subaxial injuries, respectively.

Conclusion: Pediatric patients have high rates of upper cervical spine injuries, which tend to be distraction injuries that are frequently associated with avulsion fractures. Injury patterns in pediatric patients vary significantly by age, with patients younger than 3 years old being particularly prone to distraction type injuries.

Commentary: Thank you for the work. Relatively larger size of pediatric head and stronger cervical ligaments likely explain the higher frequency of upper cervical injuries and typical avulsion fractures.


Clinical Value of Ultrasonographic Assessment in Lateral Epicondylitis Versus Asymptomatic Healthy Controls

Krogh TP, Fredberg U, Ammitzbøll C, Ellingsen T. Clinical Value of Ultrasonographic Assessment in Lateral Epicondylitis Versus Asymptomatic Healthy Controls. The American Journal of Sports Medicine. 2020 Jun 2:0363546520921949.


Background: Lateral epicondylitis (LE) also known as tennis elbow is an overuse syndrome of common extensor tendon. Increased common extensor tendon thickness is part of the tendinopathic changes observed in LE. Ultrasonography (US) is often used in the assessment of LE. The strength of evidence supporting its role is, however, not well-documented.

Questions: Can ultrasonography be used as a stand-alone technique to diagnose LE? Is Color Doppler activity of common extensor tendon pathognomonic for LE? Is there an association between the presence of bony spur and development of lateral epicondylitis?

Design: Cross-sectional observational and comparative study.

Participants: 264 participants with healthy elbows and 60 patients with chronic LE.

Exclusion criteria for patients with LE: Age <18 years, glucocorticoid injection within the past 3 months, previous LE surgery, inflammatory diseases (eg, rheumatoid arthritis, psoriatic arthritis, or inflammatory bowel disease), neck pain, shoulder pain on the ipsilateral side, and other chronic widespread pain syndromes.

Exclusion criteria for elbow-healthy group: Exclusion criteria were age <20 years and any history of lateral elbow pain.

Method: Tendon thickness, color Doppler activity, and bone spur were assessed by US. In addition to patient characteristics, Patient-Rated Tennis Elbow Evaluation (PRTEE) score, pain, and disability were recorded.

Main Results: Depending on the measurement technique used, mean LE tendon thickness increased by 0.53 mm (10.2%) or 0.70 mm (14.5%) as compared with the contralateral arm and 0.40 mm (7.9%) or 0.41 mm (8.5%) as compared with the general population. Mean color Doppler activity (scale, 0-4) was 3.47 in the LE arm versus 0.13 in the contralateral asymptomatic arm and 0.26 in the general population. Bone spur was observed in 78% of the LE arms as opposed to 45% in the contralateral arms and 50% in the general population.

Conclusion: Ultrasonography cannot be used as a stand-alone diagnostic tool but rather as a supplement to the overall assessment, given the marked variation in natural tendon thickness and small increases in tendon thickness in patients with LE. The contralateral elbow (if asymptomatic) is a better tendon thickness comparator than a general population mean-value. Color Doppler activity is an indicator of ongoing tendinopathy and supports the LE diagnosis, but it is not pathognomonic for the condition. Absence of Doppler activity in a patient with suspected LE should raise suspicion of other diagnoses. Identification of a bone spur is of very limited clinical value given the high prevalence in the general population. The important outcomes of pain, disability, PRTEE, and disease duration did not correlate with any of the investigated US techniques.

Commentary: Thank you for an interesting study. In our practice, tenderness on sonopalpation has a big role in deciding about active tendon inflammation. Agree that asymptomatic bony proliferation or tendon thickening are commonly encountered incidental findings.


Not All Green Is Tophi: The Importance of Optimizing Minimum Attenuation and Using a Tin Filter to Minimize Clumpy Artifacts on Foot and Ankle Dual-Energy CT

Park EH, Yoo WH, Song YS, Byon JH, Pak J, Choi Y. Not All Green Is Tophi: The Importance of Optimizing Minimum Attenuation and Using a Tin Filter to Minimize Clumpy Artifacts on Foot and Ankle Dual-Energy CT. American Journal of Roentgenology. 2020 Jun;214(6):1335-42.


Background: Dual-energy CT has shown promising results in distinguishing uric acid crystals from calcium by their chemical composition, which has made early diagnosis of gout possible. The total volume of tophi in chronic gout can be measured using DECT, which can allow quantitative evaluation of tophi burden and treatment response in follow up. DECT may color code nonurate material as green in certain circumstances. This artifact, which is a cluster of submillimeter green pixilation, has been described with different terms, including a “cluster of submillimeter artifacts” and a “clumpy artifact”. Because this clumpy artifact usually appears as a concentrated cluster along the tendon or ligament, it resembles tophi in its shape and location, which can complicate diagnosis and lead to false positive.

Questions: What is the frequency and location of clumpy artifacts? What is the rate of misdiagnosis of clumpy artifacts as gout? Will raising the minimum attenuation value and using a selective photon shield in DECT help in reducing the occurrence of clumpy artifact?

Design: Retrospective study

Participants: 40 patients who had foot and ankle DECT performed at Chonbuk National University Hospital.

Exclusion Criteria: Single energy CT, a history of gout, CT performed to rule out gout, age younger than 16 years old, pain that a rheumatologist suspected to be caused by gout, pre-existing metal prosthesis at scanned area, and any high attenuation noted on standard gray-scale CT images matched as green pixilation on DECT reconstruction.

Method: Images in set 1 were obtained with DECT without a tin filter; images in set 2 were obtained with DECT with a tin filter. Images in both sets were randomly assigned a minimum attenuation of 130 HU or 150 HU. Three radiologists independently checked all images for the presence, volume, and location of green color-coded pixilation and graded their findings according to a 4-point confidence scale, frequency, and volume. Misdiagnosis rate and misdiagnosis score were compared using the Wilcoxon signed rank and McNemar tests.

Main Results: In set 1, the frequency of clumpy artifacts in DECT with the minimum attenuation set to 130 HU and 150 HU were 81% and 68%, respectively. In set 2, with the minimum attenuation set to 130 HU, the frequency of the clumpy artifact was 44%; with the minimum attenuation set to 150 HU, no clumpy artifacts were seen.

Conclusion: Clumpy artifacts occurred frequently in DECT without a tin filter. Setting the minimum attenuation to the higher value of 150 HU reduced the frequency of clumpy artifacts, and adding a tin filter to DECT greatly reduced their occurrence.

Commentary: Very interesting and clinically relevant work. Reduction of such artifacts will help the clinical practice. Hopefully, more vendors can incorporate such advancements in near future.


Predicting Osteomyelitis In Patients Whose Initial MRI Demonstrated Bone Marrow Edema Without Corresponding T1 Signal Marrow Replacement

Sax AJ, Halpern EJ, Zoga AC, Roedl JB, Belair JA, Morrison WB. Predicting osteomyelitis in patients whose initial MRI demonstrated bone marrow edema without corresponding T1 signal marrow replacement. Skeletal Radiology. 2020 Mar 4:1-9.


Background: Osteomyelitis can definitely be diagnosed in the appropriate setting (adjacent to an ulcer) with marrow edema on fluid sensitive sequences and replacement of fat signal on T1-weighted images. However, in a proportion of cases, marrow signal adjacent to an ulcer is discordant, with marrow edema in fluid sensitive sequences, but normal signal on T1-weighted images. This has been postulated to represent “early osteomyelitis” or “reactive hyperemia”.

Questions: What are the MRI characteristics that suggest greatest risk for osteomyelitis in patients with diabetic foot ulcers with normal T1- weighted images?

Design: Retrospective study

Participants: MR imaging from 60 patients with suspected osteomyelitis in the setting of diabetic pedal ulcer.

Exclusion criteria: Metal or other artifacts, and recent surgery precluding the evaluation of bone marrow signal.

Method: Ulcer dimension and depth were measured. Ratios of marrow ROI/joint fluid ROI on T2/STIR sequences were obtained. Progression to osteomyelitis on subsequent MRI was characterized by loss of normal marrow signal on T1-weighted images. Statistical analysis was performed with a two-sample t test and Cox proportional hazard model.

Main Results: Of the 60 MR exams examined, 34 progressed to osteomyelitis. Marrow ROI/joint fluid ratios averaged 65% in the osteomyelitis group, and 45% in the non-osteomyelitis group, p<0.001. ROI ratios >53% had a 6.5- fold increased risk of osteomyelitis, p<0.001. Proximity to bone averaged 6mm in the osteomyelitis group and 9 mm in the non-osteomyelitis group, p=0.02. Ulcers greater than 3 cm2 have a 2-fold increase in the risk of osteomyelitis, p=0.04.

Conclusion: Increasing bone marrow ROI signal/joint fluid ratios on T2/STIR images were the strongest risk factors for developing osteomyelitis, while ulcer size and depth are weaker predictors.

Commentary: Intriguing work. In our practice, we focus more on cortical destruction with loss of T1 and T2 cortical hypointensity on MRI at the site of ulcer. The latter is a very reliable sign including cortical enhancement if gadolinium has been administered. I think hypointensity of marrow on T1 is a late development on MRI, which is suggested by the findings of this study as well.


Anomalous Signal Intensity Increase On Out-Of-Phase Chemical Shift Imaging: A Manifestation Of Marrow Mineralization?

van Vucht N, Santiago R, Pressney I, Saifuddin A. Anomalous signal intensity increase on out-of-phase chemical shift imaging: a manifestation of marrow mineralisation?. Skeletal Radiology. 2020 Mar 20:1-7.


Background: In-phase (IP) and out-of-phase (OOP) chemical shift imaging (CSI) is an established technique for clarifying the nature of indeterminate bone marrow lesions, a signal intensity (SI) drop of >20% at 1.5 tesla(T) or >25% on 3 T on the OOP sequence being consistent with non-neoplastic process such as fat containing marrow lesions. Occasionally, SI increase is seen in OOP sequences.

Question: What are the causes of increase in SI in OOP sequences?

Design:  Prospective study

Participants: 184 patients who were referred for the assessment of suspected bone tumors.

Exclusion criteria: None

Methods: In 184 cases, the SI change on OOP was calculated. For patients in whom the SI on OOP increased compared with the IP sequence, available CT studies and radiographs were reviewed to look for marrow sclerosis and/or matrix mineralization.

Main Results: Of the 184 patients, 40 patients (34.35%) showed an anomalous increase in SI on the OOP sequence. CT studies (available in 27 cases) showed medullary sclerosis in 20 of these cases and matrix mineralization in 2 cases. Radiographs demonstrated matrix mineralization in 6 cases. Punctate signal void consistent with chondral calcification was seen on MRI in 2 cases. Based on either typical imaging features or histology, 17.5% cases were classed as non-neoplastic, 45% as benign neoplasms and 37.5% as malignant neoplasms.

Conclusion: When assessing focal marrow lesions with CSI, anomalous SI increase may be seen on the OOP sequence in approximately one-third of cases. In over 75% of such cases, CT or radiographs demonstrate either diffuse marrow sclerosis or matrix mineralization.

Commentary: Great insights. Going back to physics, OOP imaging will show increase signal where there is hemorrhage or hemosiderin. It is thus expected in cases of marrow hemosiderosis e.g. sickle cell disease, PVNS (TSGCT), and hemarthrosis, etc.


Diffusion Tensor Imaging And Tractography For Preoperative Assessment Of Benign Peripheral Nerve Sheath Tumors

Gersing AS, Cervantes B, Knebel C, Schwaiger BJ, Kirschke JS, Weidlich D, Claudi C, Peeters JM, Pfeiffer D, Rummeny EJ, Karampinos DC. Diffusion tensor imaging and tractography for preoperative assessment of benign peripheral nerve sheath tumors. European Journal of Radiology. 2020 Jun 6:109110.


Background:  If a neurofibroma is detected, the complete resection of the tumor can only be achieved by completely removing the affected nerve. Yet, this causes a loss of the nerve function, therefore the resection and complications caused by this needs to be carefully weighed against the clinical symptoms as well as the potential of a neurofibroma to develop into a malignant peripheral nerve sheath tumor (MPNST), a spindle cell sarcoma. Schwannomas on the other hand are not likely to malignify and if the schwannoma is eccentrically-located on the side of the operational access route, the fascicles can easily be preserved during the operative procedure. Therefore, detailed knowledge of the exact location of the fascicles is crucial in these patients in order to achieve a complete resection without iatrogenic damage.

Questions: What is the diagnostic value of fiber tractography and diffusivity analysis generated from 3D diffusion-weighted (DW) sequences for preoperative assessment of benign peripheral nerve sheath tumors? Will preoperative diffusion tensor imaging help in the differentiation of neurofibroma and schwannoma?

Design: Prospective study, from October 2016 until January 2018.

Participants: In total, 18 schwannomas and 11 neurofibromas were assessed in 22 patients (mean age 50.9 ± 18.6 years, 13 women), with the final diagnosis proven in all cases by histopathology after excision biopsy or biopsy followed by a resection of the tumor.

Exclusion criteria: Lesions clearly not related to any peripheral nerve were excluded from this study previous to the analyses (1 sarcoma and 2 myxomas).

Method: MR imaging at 3 T was performed in 22 patients (mean age 41.9 ± 17.1y, 13 women) with histologically confirmed schwannomas ( N = 18) and histologically confirmed neurofibromas ( N = 11), including a 3D DW turbo spin echo sequence with fat suppression. Diffusion tensor parameters were computed and fiber tracks were determined. Evaluation was performed by two radiologists and one orthopedic surgeon blinded for final diagnosis. Mean diffusivity was computed to allow further assessment of tumor microstructure. Preoperative fascicle visualization was graded, fascicles were categorized regarding anatomical location and amount of fascicles surrounding the tumor. The agreement of imaging findings with intraoperative findings was assessed.

Main Results: On 78.3% of the DTI images, the fascicle visualization was rated as good or very good. Tractography differences were observed in schwannomas and neurofibromas, showing schwannomas to be significantly more often located eccentrically to the nerve (94.8 %) than neurofibromas (0 %, P < 0.01). Fascicles were significantly more often continuous (87.5 %) in schwannomas, while in neurofibromas, none of the tracks was graded to be continuous (0 %, P = 0.014). A substantial agreement between fiber tracking and surgical anatomy was found regarding the fascicle courses surrounding the tumor (κ = 0.78). Mean diffusivity of schwannomas (1.5 ± 0.2 × 10 −3 mm 2/s) was significantly lower than in neurofibromas (1.8 ± 0.2 × 10 −3 mm 2/s; P < 0.001). The Youden index showed an optimal cutoff at 1.7 × 10 −3 mm 2/s (sensitivity, 0.91; specificity, 0.78; J = 0.69).

Conclusions: Preoperative diffusion tensor imaging allowed to accurately differentiate between schwannomas and neurofibromas and to describe their location in relation to the nerve fascicles for preoperative planning.

Commentary: Thank you for a nice study. The sample size is small but nicely highlights the differences between different nerve sheath tumors. Another point to remember is that segmental schwannomatosis also renders resectability difficult or impossible. In addition, the fascicles involved with schwannoma or neurofibroma are non-functional and resection of those fascicles does not usually lead to significant functional weakness. Look forward to larger studies on this subject.


Flat-Panel CT Arthrography For Cartilage Defect Detection In The Ankle Joint: First Results In Vivo

Sarah P, David C, Roman G, Vanessa P, Daphné G, Pierre C, Le Corroller T. Flat-panel CT arthrography for cartilage defect detection in the ankle joint: first results in vivo. Skeletal radiology. 2020 Mar 7:1-7.


Background:  Direct MR arthrography leads to better results in the detection of chondral defects compared with standard MR imaging and should therefore be considered in patients with specific suspicion of articular cartilage lesion. MDCT arthrography is considered the method of choice in the assessment of articular cartilage, especially in the ankle joint where hyaline cartilage is particularly thin. FPCT arthrography has recently been shown to be as feasible as MDCT arthrography with similar image quality in vitro and ex vivo.

Questions: What is the diagnostic performance of FPCT arthrography for cartilage defect detection in the ankle joint when compared to MR arthrography and MDCT arthrography?

Design: Prospective comparative study

Participants: Twenty seven patients with suspected articular cartilage lesion of the ankle joint were enrolled between July 2015 and April 2017. These patients had FPCT, MDCT and MR arthrography performed on the same day as a part of preoperative workup.

Exclusion criteria: History of previous ankle arthroscopy or open surgery and the time delay between contrast agent injection and cross-sectional imaging longer than 30 minutes.

Method: Twenty seven patients with specific suspicion of articular cartilage lesion underwent ankle arthrography with injection of a mixture of diluted gadolinium and iobitridol and were examined consecutively with the use of FPCT, MDCT, and 1.5 T MR imaging. FPCT, MDCT, and MR arthrography examinations were blinded and randomly evaluated by two musculoskeletal radiologists in consensus. In each ankle, eight articular cartilage areas were assessed separately: medial talar surface, medial talar trochlea, lateral talar trochlea, lateral talar surface, tibial malleolus, medial tibial plafond, lateral tibial plafond, and fibular malleolus. Findings at FPCT and MR were compared with MDCT assessments in 216 cartilage areas.

Main Results: For the detection of cartilage defects, FPCT demonstrated a sensitivity of 97%, specificity of 95%, and accuracy of 96%; and MR arthrography showed a sensitivity of 69%, specificity of 94%, and accuracy of 87%. FPCT and MR arthrography presented almost perfect agreement and moderate agreement, respectively, with MDCT arthrography. Mean diagnostic confidence was higher for FPCT (2.9/3) than for MR (2.3/3) and MDCT (2.7/3) arthrography.

Conclusion: FPCT demonstrated better accuracy than did 1.5 T MR arthrography for cartilage defect detection in the ankle joint. Therefore, FPCT should be considered in patients scheduled for dedicated imaging of ankle articular cartilage.

Commentary: Thanks for the work. MR arthrogram of ankle is becoming obsolete in our practice and high-resolution 1.5T scans or 3D imaging on 1.5T and 3T scanners have virtually replaced all imaging for cartilage assessment of the joints. One can avoid radiation if image resolution of MR imaging is kept optimal with 3mm slices on 2D imaging and a matrix of 256 and above or 0.65-0.7mm voxel on 3D T2W imaging.

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