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Objectives: To evaluate CT imaging findings in symptomatic patients with and without revision surgery (RS) after reverse shoulder arthroplasty (RSA)., Materials and Methods: In this retrospective study, two radiologists assessed CT imaging findings in symptomatic patients with RSA over 5 years, including material fracture and loosening of the peg, baseplate, screws, and humeral stem, screw positioning, prosthesis dislocation, glenoid notching, fractures, and deltoid muscle quality. The primary outcome parameter was RS. Patients were assigned Group 1 (RS) or Group 2 (No RS)., Results: Ninety-nine patients (mean age 70.4 ± 10.3 years, 61 females) met the inclusion criteria. Fifty-two patients (29 females) received RS after 34.0 ± 38.3 months. The only CT imaging finding significantly associated with RS was prosthesis dislocation (P = .007, odds ratio (OR) 10.95, 95% CI 1.34-89.24). All other evaluated CT imaging findings were not associated with RS. Yet, loosening of the peg (30% vs. 16%), baseplate (15% vs. 6%), and superior screw (18% vs. 7%) and periprosthetic humeral fractures (29% vs. 13%)-as common reasons for RS-were more frequent in patients with RS than in those without, however not reaching significance (P ≥ .11). The large majority of patients had glenoid notching (79% vs. 94%), irrespective of RS., Conclusion: In this cohort of symptomatic patients after RSA, prosthesis dislocation was the only CT imaging finding associated with RS. Besides, there was a trend with higher numbers of loosening of the peg, baseplate, and superior screw, as well as periprosthetic humeral fractures in patients with RS, though not reaching significance., Competing Interests: Declarations. Ethical approval: This study was approved by the local ethics committee (Cantonal Ethics Committee Zurich) and conducted according to the 1964 Helsinki Declaration and its later amendments and national ethical standards. Informed consent: Informed consent was obtained from all participants included in this study. Conflict of interest: Prof. Reto Sutter (RS) receives royalties for his work as a book editor at Breitenseher Publisher. The remaining authors do not have any conflicts of interest to declare., (© 2025. The Author(s).)

Objectives: To assess calf muscle constitution in chronic Achilles tendon disease (ATD) using two-point Dixon-based MRI (2pt-MRI DIXON )., Materials and Methods: This retrospective study analyzed 91 patients (36 females; 57.0 ± 14.4 years) with midportion or insertional chronic ATD who underwent clinical MRI of the Achilles tendon (AT), including 2pt-MRI DIXON for quantitative assessment of calf muscle fat content (MFC). Additionally, two radiologists qualitatively assessed MFC, AT quality, and co-pathologies. 2pt-MRI DIXON -derived fat fractions (FF) were related to patients' demographics and qualitative imaging findings., Results: The overall mean FF derived from 2pt-MRI DIXON of the triceps surae muscle was 11.2 ± 9.3%. Comparing midportion and insertional ATD, there was no significant difference regarding fatty muscle infiltration assessed with 2pt-MRI DIXON (P ≥ .47) or qualitative grading (P ≥ .059). More severe AT thickening (11 vs.9 mm, P < .001) and complete tears (29 vs. 9%, P = .025) were significantly more common in midportion ATD, while partial tears were significantly more frequent in insertional ATD (55 vs. 31%, P = .027). Soleus muscle edema was more prevalent in midportion than insertional ATD (40 vs. 9%, P = .002). In contrast, insertional ATD more commonly featured bone marrow edema (61 vs. 2%), Haglund's deformity (67 vs. 0%), and retrocalcaneal bursitis (82 vs. 43%) (P ≤ .002). Significant correlations (P ≤ .001) were demonstrated between FF, AT diameter, age (both in midportion and insertional ATD), and body mass index (in midportion ATD only) (ρ range = 0.53-0.61)., Conclusion: In chronic ATD, calf MFC was statistically equivalent (approximately 11%), irrespective of the localization of tendon damage. More severe tendon thickening and complete tears were more common in midportion ATD, and, vice versa, partial AT tears were significantly more frequent in insertional ATD., Competing Interests: Declarations. Ethical approval: This study was approved by the local ethics committee (Cantonal Ethics Committee Zurich) and conducted according to institutional and national ethical standards in accordance with the 1964 Helsinki Declaration and its later amendments or comparable ethical standards. Informed consent: Informed consent was obtained from all participants included in this study. Competing interests: Prof. Reto Sutter (RS) receives royalties for his work as a book editor at Breitenseher Publisher. The remaining authors do not have any conflicts of interest to declare., (© 2024. The Author(s).)

Objective: To examine how different photon-counting detector (PCD) CT scanning and reconstruction methods affect the volume of metal artifacts and image quality for a hip prosthesis phantom., Methods: A titanium and cobalt-chromium-molybdenum-alloy total hip prosthesis phantom was scanned using a clinical PCD-CT with a constant tube potential (140 kV) and Computed-Tomography-Dose- Index (7 mGy). Different scan settings were used: with/without tin-filter (Sn), with/without ultra-high resolution (UHR), both individually and combined, resulting in four modes: Quantumplus (Standard), UHR Quantumplus (HighRes), QuantumSn (Standard-Tin) and UHR QuantumSn (HighRes-Tin). Reconstructions included virtual monoenergetic images (VMI) spanning 40-190 keV and polychromatic images, with/without iterative metal artifact reduction (MAR). Artifact volumes rendered in a 3D-printing software were quantified in milliliters (ml), and image quality was evaluated using a Likert score., Results: Polychromatic reconstruction: Tin-filter reduced artifact volumes (298 (Standard-Tin) vs. 347 ml (Standard) and 310 (HighRes-Tin) vs. 360 ml (HighRes)). The smallest artifact volume was measured in HighRes MAR (150 ml). VMI reconstruction: The smallest artifact volume was measured in Standard 130 keV (150 ml) and HighRes 130 keV (164 ml) and in Standard-Tin 120 keV (169 ml) and HighRes-Tin 120 keV (172 ml). MAR further reduced the artifact volumes to 130 ml (Standard 150 keV MAR) and 140 ml (HighRes 160 keV MAR). Image quality was rated best for Standard 65 keV MAR, polychromatic HighRes MAR, Standard 100 keV MAR, polychromatic Standard-tin MAR, HighRes-tin 100 keV and polychromatic HighRes-tin., Conclusion: Combining tin-filter, UHR and MAR in VMI or polychromatic images achieve the strongest artifact reduction., (© 2024. The Author(s).)

Objectives: Knowledge about the long-term outcome of patients with lumbar spondylolysis (LS) is limited. This study assessed the frequency of bone fusion in conservatively treated lumbar spondylolysis with photon counting detector computed tomography., Methods: Patients with lumbar spondylolysis diagnosed with CT or MRI were prospectively enrolled and underwent CT 5-10 years after initial imaging. Image assessment included evaluation of Meyerding grade, listhesis size, measurement of the lysis gap, and disc integrity on the lysis level. Comparisons were made between bone fusion as the primary endpoint and sex, body mass index, age at diagnosis, follow-up interval, size of listhesis, Meyerding grade, size of the lysis gap, sports activity, and presence of pain., Results: A total of 39 patients (26.0 ± 3.1 years, 15 female) with lumbar spondylolysis on 41 levels were included after a mean follow-up period of 9.1 ± 2.2 years. Nine patients (22.0%, four female) showed complete fusion of the lysis gap. Patients with bone fusion of the lysis gap had a significantly lower Meyerding grade (p = 0.01), smaller size of the listhesis (p = 0.019), and smaller anterior and posterior lysis gap size (p = 0.046 and p = 0.011, respectively). Unilateral lyses showed significantly higher fusion rates than bilateral lyses (40.0% vs. 16.1%, p = 0.01). No statistically significant difference was found for pain at follow-up between patients with and without bone fusion (p = 0.253)., Conclusion: Bone fusion occurred in about a fifth of conservatively treated lumbar spondylolysis after a follow-up period of 9 years. Factors associated with a successful fusion were a lower Meyerding grade, minimal listhesis, and a small lysis gap., (© 2024. The Author(s).)

Magnetic resonance imaging (MRI) around metal implants has been challenging due to magnetic susceptibility differences between metal implants and adjacent tissues, resulting in image signal loss, geometric distortion, and loss of fat suppression. These artifacts can compromise the diagnostic accuracy and the evaluation of surrounding anatomical structures. As the prevalence of total joint replacements continues to increase in our aging society, there is a need for proper radiological assessment of tissues around metal implants to aid clinical decision-making in the management of post-operative complaints and complications. Various techniques for reducing metal artifacts in musculoskeletal imaging have been explored in recent years. One approach focuses on improving hardware components. High-density multi-channel radiofrequency (RF) coils, parallel imaging techniques, and gradient warping correction enable signal enhancement, image acquisition acceleration, and geometric distortion minimization. In addition, the use of susceptibility-matched implants and low-field MRI helps to reduce magnetic susceptibility differences. The second approach focuses on metal artifact reduction sequences such as view-angle tilting (VAT) and slice-encoding for metal artifact correction (SEMAC). Iterative reconstruction algorithms, deep learning approaches, and post-processing techniques are used to estimate and correct artifact-related errors in reconstructed images. This article reviews recent developments in clinically applicable metal artifact reduction techniques as well as advances in MR hardware. The review provides a better understanding of the basic principles and techniques, as well as an awareness of their limitations, allowing for a more reasoned application of these methods in clinical settings., (© 2024. The Author(s).)

Objective: To compare the image quality of low-dose CT (LD-CT) with tin filtration of the lumbar spine after metal implants to standard clinical CT, and to evaluate the potential for metal artifact and dose reduction., Materials and Methods: CT protocols were optimized in a cadaver torso. Seventy-four prospectively included patients with metallic lumbar implants were scanned with both standard CT (120 kV) and tin-filtered LD-CT (Sn140kV). CT dose parameters and qualitative measures (1 = worst,4 = best) were compared. Quantitative measures included noise, signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), and the width and attenuation of the most prominent hypodense metal artifact. Standard CT and LD-CT were assessed for imaging findings., Results: Tin-filtered LD-CT was performed with 60% dose saving compared to standard CT (median effective dose 3.22 mSv (quartile 1-3: 2.73-3.49 mSv) versus 8.02 mSv (6.42-9.27 mSv; p < .001). Image quality of CT and tin-filtered low-dose CT was good with excellent depiction of anatomy, while image noise was lower for CT and artifacts were weaker for tin-filtered LD-CT. Quantitative measures also revealed increased noise for tin-filtered low-dose CT (41.5HU), lower SNR (2) and CNR (0.6) compared to CT (32HU,3.55,1.03, respectively) (all p < .001). However, tin-filtered LD-CT performed superior regarding the width and attenuation of hypodense metal artifacts (2.9 mm and -767.5HU for LD-CT vs. 4.1 mm and -937HU for CT; all p < .001). No difference between methods was observed in detection of imaging findings., Conclusion: Tin-filtered LD-CT with 60% dose saving performs comparable to standard CT in detection of pathology and surgery related complications after lumbar spinal instrumentation, and shows superior metal artifact reduction., (© 2023. The Author(s).)

Back pain is one of the most common medical problems and is associated with high socioeconomic costs. Imaging-guided spinal injections are a minimally invasive method to evaluate where the back pain is originating from, and to treat patients with radicular pain or spinal stenosis with infiltration of corticosteroids. CT-guided spine injections are a safe procedure, characterized by precise needle placement, excellent visualization of the relevant anatomical structures, and low radiation exposure for the patient and the interventional radiologist. In this review article, the variety of applications of CT-guided injections (focused on nerve roots and epidural injections) and the optimal injection procedure as well as risks and side effects are discussed., (© 2022. The Author(s).)

Purpose: To evaluate the distribution and severity of muscle atrophy in diabetic patients with active Charcot foot (CF) compared to diabetic patients without CF. Furthermore, to correlate the muscle atrophy with severity of CF disease., Material/methods: In this retrospective study, MR images of 35 diabetic patients (21 male, median:62.1 years ± 9.9SD) with active CF were compared with an age- and gender-matched control group of diabetic patients without CF. Two readers evaluated fatty muscle infiltration (Goutallier-classification) in the mid- and hindfoot. Furthermore, muscle trophic (cross-sectional muscle area (CSA)), intramuscular edema (none/mild versus moderate/severe), and the severity of CF disease (Balgrist Score) were assessed., Results: Interreader correlation for fatty infiltration was substantial to almost perfect (kappa-values:0.73-1.0). Frequency of fatty muscle infiltration was high in both groups (CF:97.1-100%; control:77.1-91.4%), but severe infiltration was significantly more frequent in CF patients (p-values: < 0.001-0.043). Muscle edema was also frequently seen in both groups, but significantly more often in the CF group (p-values: < 0.001-0.003). CSAs of hindfoot muscles were significantly smaller in the CF group. For the flexor digitorum brevis muscle, a cutoff value of 139 mm 2 (sensitivity:62.9%; specificity:82.9%) in the hindfoot was found to differentiate between CF disease and the control group. No correlation was seen between fatty muscle infiltration and the Balgrist Score., Conclusion: Muscle atrophy and muscle edema are significantly more severe in diabetic patients with CF disease. Muscle atrophy does not correlate with the severity of active CF disease. A CSA < 139 mm 2 of the flexor digitorum brevis muscle in the hindfoot may indicate CF disease., (© 2023. The Author(s).)

Objective: De-centering of the shoulder joint on radiographs is used as indicator for severity of rotator cuff tears and as predictor for clinical outcome after surgery. The objective of the study was to assess the effect of malrotation on glenohumeral centering on radiographs and to identify the most reliable parameter for its quantification., Subjects and Methods: In this retrospective study (2014-2018), 249 shoulders were included: 92 with imaging-confirmed supra- and infraspinatus tears (rupture; 65.2 ± 9.9 years) and 157 without tears (control; 41.1 ± 13.0 years). On radiographs in neutral position and external rotation, we assessed three radiographic parameters to quantify glenohumeral centering: acromiohumeral distance (ACHD), craniocaudal distance of the humeral head and glenoid center (Deutsch), and scapulohumeral arch congruity (Moloney). Non-parametric statistics was performed., Results: In both positions, only the distance parameters ACHD (< 0.5 mm) and Deutsch (< 1 mm) were comparable in the two study groups rupture and control. Comparing the parameters between the study groups revealed only ACHD to be significantly different with a reduction of more than 2 mm in the rupture group. Among the parameters, ACHD ≤ 6 mm was the only cut-off discriminating rupture (12-21% of the shoulders with ACHD ≤ 6 mm) and control (none of the shoulders with ACHD ≤ 6 mm). Ninety percent of shoulders with ACHD ≤ 6 mm presented with a massive rotator cuff tear (defined as ≥ 67% of the greater tuberosity exposed)., Conclusion: Glenohumeral centering assessed by ACHD and Deutsch is not affected by rotation in shoulders with and without rotator cuff tear. An ACHD ≤ 6 mm has a positive predictive value of 90% for a massive rotator cuff tear., (© 2022. The Author(s).)

Objective: To assess the predictive value of immediate pain-relief after CT-guided transforaminal epidural steroid injection (TFESI) including local anesthetics for longer-term pain relief and patients' global impression of change (PGIC) after 4 weeks., Materials and Methods: One hundred ninety-three patients (age 55.4 ± 14.9) with single-level discogenic lumbar radiculopathy and subsequent TFESI were included. Pain scores were recorded before (NRS 0 ), 15 min (NRS 15min ), and 4 weeks (NRS 4w ) after treatment using a numerical-rating-scale (NRS; 0, no pain; 10, intolerable pain). Additionally, the PGIC was assessed after 4 weeks. Two fellowship-trained musculoskeletal radiologists evaluated nerve compression of the injected level and contrast dispersion. Spearman's rank and point-biserial correlation were applied to assess associations between outcome variables and demographics/imaging findings. A p-value < 0.05 was considered to be statistically significant., Results: There was a significant positive correlation between immediate pain-relief and longer-term pain-reduction (r = 0.24, p = 0.001) with an odds ratio of 2.0 (CI: 1.1-3.6). A good short-term response (NRS 15min  ≥ 50% reduction) was associated with a persistent longer-term good response (NRS 4w  ≥ 50% reduction) in 59.7% (CI: 50.9-68.0%) of patients. There was no association between short-term pain-relief and PGIC after 4 weeks (p = 0.18). Extent and location of nerve compression and contrast dispersion during TFESI did not correlate with longer-term pain-relief (all p ≥ 0.07)., Conclusion: Our results indicate a significant positive correlation between immediate post-procedural and longer-term pain relief after TFESI in patients with lumbar radiculopathy; however, no effect of short-term pain relief is seen on PGIC after 4 weeks. Patients with good longer-term outcome (≥ 50% pain reduction) are twice as likely to have already shown good immediate pain reduction after TFESI., (© 2022. The Author(s).)

Purpose: To investigate the predictive value of talar head edema (THE) in acute ankle sprain for the presence of concomitant ligament injuries., Methods: This retrospective study was approved by the ethics committee and informed consent was obtained. One hundred patients (mean age: 37 years ± 14 [standard deviation], range 13-77 years) with MRI of the ankle after acute trauma were included. The cohort in this matched-pair study consisted of 50 patients with THE (group 1) and 50 patients without THE (group 2). Two readers independently evaluated presence and size of bone marrow edema of the talus head and injuries of the lateral, medial, talonavicular, and spring ligament complex. Statistics included intraclass correlation coefficient (ICC) and Kappa statistics as well as parametric and non-parametric tests., Results: On average, patients with THE demonstrated significantly more ligament injuries in comparison to patients without THE (3.7 vs. 1.3, p ≤ 0.01). Also, in patients with THE, the number of injured ligaments was significantly higher at the lateral (p = 0.03), medial (p ≤ 0.01), and talonavicular (p ≤ 0.01) compartment in comparison to patients without THE. The most frequently injured ligaments in patients with THE were the anterior talofibular ligament (60%) and the anterior tibiotalar ligament (42%). There was no significant correlation between edema size and the number of injured ligaments or compartments (p = 0.5)., Conclusion: THE is associated with more extensive ligamentous ankle injury, in particular to the medial and lateral collateral ligament complex, and therefore indicative of severe ankle trauma., (© 2022. The Author(s).)

Objective: This study aims to evaluate the image quality of virtual non-contrast (VNC) images calculated from dual-energy CT shoulder arthrography (DECT-A) and their ability to detect periosteal calcifications and intraarticular loose bodies., Materials and Methods: In 129 shoulders of 123 patients, DECT arthrography (80 kV/140 kV) was performed with diluted iodinated contrast material (80 mg/ml). VNC images were calculated with image postprocessing. VNC image quality (1 = worst, 5 = best), dose parameters, and CT numbers (intraarticular iodine, muscle, VNC joint fluid density) were assessed. Image contrast (iodine/muscle) and percentage of iodine removal were calculated. Two independent readers evaluated VNC and DECT-A images for periosteal calcifications and intraarticular loose bodies, and diagnostic confidence (1 = low, 4 = very high) was assessed., Results: VNC images (129/129) were of good quality (median 4 (3-4)), and the mean effective dose of DECT-A scans was 2.21 mSv (± 1.0 mSv). CT numbers of iodine, muscle, and VNC joint fluid density were mean 1017.6 HU (± 251.6 HU), 64.6 HU (± 8.2 HU), and 85.3 HU (± 39.5 HU), respectively. Image contrast was mean 953.1 HU (± 251 HU) on DECT-A and 31.3 HU (± 32.3 HU) on VNC images. Iodine removal on VNC images was 91% on average. No difference was observed in the detection of periosteal calcifications between VNC (n = 25) and DECT-A images (n = 21) (p = 0.29), while the detection of intraarticular loose bodies was superior on VNC images (14 vs. 7; p = 0.02). Diagnostic confidence was higher on VNC images for both periosteal calcifications (median 3 (3-3) vs. 3 (3-3); p = 0.009) and intraarticular loose bodies (median 3 (3-4) vs. 3 (3-3); p < 0.001)., Conclusion: VNC images from DECT shoulder arthrography are superior to DECT-A images for the detection of intraarticular loose bodies and increase the confidence in detecting periosteal calcifications., (© 2022. The Author(s).)

Objective: To evaluate the image quality of dual energy CT (DECT) of the shoulder after arthrography and of virtual non-contrast (VNC) 3D reformats of the glenoid and to compare glenoid measurements on VNC 3D reformats and on 2D CTs., Materials and Methods: DECT arthrography (80 kV/140 kV) was performed in 42 shoulders of 41 patients with instability using diluted iodinated contrast media (80 mg/ml). VNC images and VNC 3D reformats of the glenoid were calculated using image postprocessing. Dose parameters, CT values of intraarticular iodine and muscle, image contrast (iodine/muscle), and image quality (5-point scale: 1 = worst, 5 = best) were evaluated. Two independent readers assessed glenoid morphology and performed glenoid measurements on 2D and 3D images., Results: Calculation of VNC images and VNC 3D reformats was successful in 42/42 shoulders (100%). The effective dose was mean 1.95 mSv (± 0.9 mSv). CT values of iodine and muscle were mean 1014.6 HU (± 235.8 HU) and 64.5 HU(± 8.6 HU), respectively, and image contrast was mean 950.2 HU (± 235.5 HU). Quality of cross-sectional images, VNC images, and VNC 3D reformats was rated good (median 4 (4-5), 4 (3-4), 4 (3-5), respectively). Detection of an osseous defect was equal on 2D and 3D images (13/42, P > 0.99) with no difference for measurement of the glenoid diameter with mean 28.3 mm (± 2.8 mm) vs. 28.4 mm (± 2.9 mm) (P = 0.5), width of the glenoid defect with 3.2 mm (± 2.1 mm) vs. 3.1 mm (± 2.3 mm) (P = 0.84), surface area with 638.5 mm 2 (± 127 mm 2 ) vs. 640.8 mm 2 (± 129.5 mm 2 ) (P = 0.47), and surface area of the defect with 46.6 mm 2 (± 44.3 mm 2 ) vs. 47.2 mm 2 (± 48.0 mm 2 ) (P = 0.73), respectively., Conclusion: DECT shoulder arthrography is feasible and allows successful iodine removal with generation of VNC images and accurate VNC 3D reformats of the glenoid for assessment of bone loss., (© 2021. The Author(s).)

Objective: To investigate the impact of contrast dispersion pattern/location during lumbar CT-guided transforaminal epidural steroid injection (TFESI) and experience of the performing radiologist on therapeutic outcome., Materials and Methods: In this single-center retrospective cohort study, two observers analyzed contrast dispersion during CT-guided TFESI of 204 patients (age 61.1 ± 14 years) with discogenic unilateral single-level L4 or L5 radiculopathy. The contrast dispersion pattern was classified as "focal," "linear," or "tram-track"; the location was divided into "extraforaminal," "foraminal," or "recessal." Pain was assessed before and 4 weeks after treatment using a numerical rating scale (0, no pain; 10, intolerable pain). Additionally, the patient global impression of change (PGIC) was assessed. The TFESI was performed by musculoskeletal radiologists (experience range: first year of musculoskeletal fellowship training to 19 years). Contrast pattern/location and radiologist's experience were compared between "good responder" (≥ 50% pain reduction) and "poor responder" (< 50%). A p-value < 0.05 was considered to be statistically significant., Results: Overall, CT-guided TFESI resulted in a substantial pain reduction in 46.6% of patients with discogenic radiculopathy. The contrast dispersion pattern and location had no effect on pain relief (p = 0.75 and p = 0.09) and PGIC (p = 0.70 and p = 0.21) 4 weeks after TFESI. Additionally, the experience of the radiologist had no influence on pain reduction (p = 0.92) or PGIC (p = 0.75). Regarding pre-interventional imaging findings, both the location and grading of nerve compression had no effect on pain relief (p = 0.91 and p = 0.85) and PGIC (p = 0.18 and p = 0.31)., Conclusion: Our results indicate that neither contrast agent dispersion/location nor the experience of the radiologist allows predicting the therapeutic outcome 4 weeks after the procedure., (© 2021. The Author(s).)

Objectives: To assess the value of the divergence of toes on conventional radiographs of the foot for diagnosing Morton's neuroma., Methods: This retrospective case-control study was approved by the local ethics committee. In 100 patients with MRI-proven Morton's neuroma 2/3 or 3/4 (study group) and 100 patients without (control group), conventional weight-bearing dorso-plantar view radiographs were evaluated for the subjective presence of interphalangeal divergence, called the Vulcan salute sign or V-sign, by two blinded, independent musculoskeletal radiologists. Interphalangeal angles (2/3 and 3/4) and intermetatarsal angle I/V were measured. The t test and chi-squared test were used to compare the groups. Diagnostic performance was calculated. Interobserver reliability was assessed using κ statistics and intraclass correlation coefficient (ICC)., Results: The difference between the groups was significant (P < 0.05) regarding the presence of the V-sign, which was found in 30 of 100 patients with Morton neuroma and in 3 of 100 control patients, with a sensitivity of 30% and a specificity of 97%. The differences between interphalangeal angles were significant (P < 0.05) between the groups. The interphalangeal angle 2/3 mean values were 7.9° (± 4.8) for the study group vs 5.4° (± 2.6) for the controls; the 3/4 angle values were 6.5° (± 3.8) and 3.4° (± 2.5), respectively. There was no significant difference between the groups in the intermetatarsal angle I/V. Interobserver agreement was substantial for the V-sign, with a κ value of 0.78. The ICC was excellent concerning angle measurements, with all values ≥ 0.94., Conclusion: The Vulcan salute sign on conventional radiographs is specific for Morton's neuroma., (© 2021. The Author(s).)

Objective: To evaluate the prevalence, morphology, and clinical significance of a repeatedly observed yet not examined circumscript osseous defect at the anteroinferior aspect of the femoral head, termed femoral head defect., Materials and Methods: Retrospective study with approval of the institutional review board. There was informed consent by all individuals. Magnetic resonance imaging (MRI) hip examinations of 970 individuals (age 15 to 55) were analyzed for femoral head defect. Patients with femoral head defect were matched for age and gender with patients without defect. Two readers independently assessed MRI images regarding presence, location, and morphology of the defect. MR images and radiographs were analyzed for findings of femoroacetabular impingement (FAI). Femoral torsion was measured. Independent t test and chi-square test were used for statistics., Results: Sixty-eight (7%) of 970 MRI examinations exhibited a femoral head defect in an anteroinferior location of the femoral head (29/400 men, 7.3%; 39/570 women, 6.8%; p = 0.8). The most frequent morphology of femoral head defect was type I, dent-like (34; 50%), followed by type II, crater-like (27; 40%), and III, cystic (7; 10%). Femoral head defect was slightly more common on the right hip (39 individuals; 57%) compared to left (29 individuals; 43%), non-significantly (p = 0.115). There was no association between FAI or its subtypes and the presence of femoral head defect (p = 0.890). Femoral antetorsion was reduced in patients with femoral head defect (12.9° ± 8.6) compared to patients without defect (15.2° ± 8.5), without statistical significance (p = 0.121)., Conclusion: The femoral head defect is a common finding in MRI examinations of the hip and is situated in the anteroinferior location. There was no association with FAI yet a non-significant trend towards lower femoral antetorsion in patients with femoral head defects., (© 2021. The Author(s).)

Objective: To investigate long-term effects of pregnancy/childbirth on bone marrow edema (BME) and subchondral sclerosis of sacroiliac joints (SIJ) in comparison to MRI changes caused by spondyloarthritis (SpA) and assess the influence of birth method and number of children on SIJ-MRI changes., Materials and Methods: This is a retrospective cohort study with 349 women (mean age 47 ± 14 years) suffering low back pain. Four subgroups were formed based on SpA diagnosis and childbirth (CB) history. Two musculoskeletal radiologists scored the presence of BME and sclerosis on SIJ-MRI using the Berlin method. Further, an 11-point "global assessment score" representing the overall confidence of SpA diagnosis based on MRI was evaluated in addition to the ASAS (Assessment of Spondyloarthritis International Society) criterion of "positive MRI" for sacroiliitis., Results: CB did not correlate with BME score (p = 0.38), whereas SpA diagnosis was associated with a higher BME score (r = 0.31, p < 0.001). Both CB (r = 0.21, p < 0.001) and SpA diagnosis (r = 0.33, p < 0.001) were correlated with a higher sclerosis score. CB was not associated with a higher confidence level in diagnosing SpA based on MRI (p = 0.07), whereas SpA diagnosis was associated with a higher score (r = 0.61, p < 0.001). Both CB (phi = 0.13, p = 0.02) and SpA diagnosis (phi = 0.23, p < 0.001) were significantly associated with a positive ASAS criterion for sacroiliitis. In non-SpA patients with CB, number of children (p = 0.001) was an independent predictor of sclerosis score, while birth method yielded no significant effect (p = 0.75)., Conclusion: Pregnancy/CB has no impact on long-term BME on SIJ, however, may cause long-term subchondral sclerosis-similar to SpA-associated sclerosis. Number of children is positively correlated with SIJ sclerosis. Birth method yields no effect on SIJ sclerosis.

Objective: To prospectively assess the evolution of postoperative MRI findings in asymptomatic patients after total hip arthroplasty (THA) over 24 months (mo)., Methods: This prospective cohort study included 9 asymptomatic patients (56.7 ± 15.0 years) after THA. Metal artifact-reduced 1.5-T MRI was performed at 3, 6, 12, and 24 mo after surgery. The femoral stem and acetabular cup were assessed by two readers for bone marrow edema (BME), periprosthetic bone resorption, and periosteal edema in addition to periarticular soft tissue edema and joint effusion., Results: BME was common around the femoral stem in all Gruen zones after 3 mo (range: 50-100%) and 6 mo (range: 33-100%) and in the acetabulum in DeLee and Charnley zone II after 3 mo (100%) and 6 mo (33%). BME decreased substantially after 12 mo (range: 0-78%) and 24 mo (range: 0-50%), may however persist in particular in Gruen zones 1 + 7. Periosteal edema along the stem was common 3 mo postoperatively (range: 63-75%) and rare after 24 mo: 13% only in Gruen zones 2 and 5. Twelve months and 24 mo postoperatively, periprosthetic bone resorption was occasionally present around the femoral stem (range: 11-33% and 13-38%, respectively). Soft tissue edema occurred exclusively along the surgical access route after 3 mo (100%) and 6 mo (89%) and never at 12 mo or 24 mo (0%)., Conclusion: Around the femoral stem, BME (33-100%) and periosteal edema (0-75%) are common until 6 mo after THA, decreasing substantially in the following period, may however persist up to 24 mo (BME: 0-50%; periosteal edema: 0-13%) in few non-adjoining Gruen zones. Soft tissue edema along the surgical access route should have disappeared 12 mo after surgery.

Pacinian corpuscles represent special nerve endings that serve as mechanoreceptors sensitive to vibration and pressure and are crucial for proprioception. This work demonstrates that the complex network of Pacinian corpuscles in hands and feet can be examined with three-dimensional Dual Echo Steady State (DESS) MR imaging at 7 T, while previous dedicated MRI reports were either limited to two-dimensional images or focused on the hands. The high-resolution MR images show the detailed architecture of the complex receptor network and reveal a "chain-like" arrangement of Pacinian corpuscles, a predilection for clustering around metacarpophalangeal/metatarsophalangeal joints, proximal phalanges and fingertips, and specific sensor locations both in the superficial subcutaneous tissue and adjacent to deep soft tissue structures such as tendons and joint capsules.

Objective: To develop a new magnetic resonance imaging(MRI) scoring system for evaluation of active Charcot foot and to correlate the score with a duration of off-loading treatment ≥ 90 days., Methods: An outpatient clinic database was searched retrospectively for MRIs of patients with active Charcot foot who completed off-loading treatment. Images were assessed by two radiologists (readers 1 and 2) and an orthopedic surgeon (reader 3). Sanders/Frykberg regions I-V were evaluated for soft tissue edema, bone marrow edema, erosions, subchondral cysts, joint destruction, fractures, and overall regional manifestation using a score according to degree of severity (0-3 points). Intraclass correlations (ICC) for interreader agreement and receiver operating characteristic analysis between MR findings and duration of off-loading-treatment were calculated., Results: Sixty-five feet in 56 patients (34 men) with a mean age of 62.4 years (range: 44.5-85.5) were included. Region III (reader 1/reader 2: 93.6/90.8%) and region II (92.3/90.8%) were most affected. The most common findings in all regions were soft tissue edema and bone marrow edema. Mean time between MRI and cessation of off-loading-treatment was 150 days (range: 21-405). The Balgrist Score was defined in regions II and III using soft tissue edema, bone marrow edema, joint destruction, and fracture. Interreader agreement for Balgrist Score was excellent: readers 1/2: ICC 0.968 (95% CI: 0.948, 0.980); readers 1/2/3: ICC 0.856 (0.742, 0.917). A cutoff of ≥ 9.0 points in Balgrist Score (specificity 72%, sensitivity 66%) indicated a duration of off-loading treatment ≥ 90 days., Conclusion: The Balgrist Score is a new MR scoring system for assessment of active Charcot foot with excellent interreader agreement. The Balgrist Score can help to identify patients with off-loading treatment ≥ 90 days.

Objective: In total hip arthroplasty (THA), surgeons attempt to achieve a physiological antetorsion. However, postoperative antetorsion of the femoral stem is known to show large variabilities. The purpose of this study was to assess whether postoperative antetorsion is influenced by stem design or cementation., Materials and Methods: This retrospective study included 227 patients with a hip prosthesis with five different stem designs (S1: short curved, S2 and S3: standard straight, S4: standard straight collared, S5: cemented straight), who had metal suppressed 1.5T-MRI of the hip between February 2015 and October 2019. Measurement of femoral antetorsion was done independently by two fellowship-trained radiologists on axial images by measuring the angle between the long axis of the femoral neck and the posterior condylar tangent of the knee. Measured angles in the different groups were compared using the t test for independent samples., Results: The cementless collared stem S4 showed the highest antetorsion with 18.1° (± 10.5°; range -10°-45°), which was significantly higher than the antetorsion of the collarless S3 with 13.3° (± 8.4°; - 4°-29°) and the cemented S5 with 12.7° (± 7.7°; - 3°-27°) with p = 0.012 and p = 0.007, respectively. S1 and S2 showed an antetorsion of 14.8° (± 10.0°; 1°-37°) and 14.1° (± 12.2°; - 20°-41°). The torsional variability of the cementless stems (S1-4) was significantly higher compared with that of the cemented S5 with a combined standard deviation of 10.5° and 7.7° (p = 0.019)., Conclusion: Prosthesis design impacts the postoperative femoral antetorsion, with the cementless collared stem showing the highest antetorsion. Cemented stems demonstrated significantly lower variability, suggesting the lowest rate of inadvertent malrotation.

Objectives: To investigate the value of extensive perilesional muscle edema for the differentiation between myositis ossificans (MO) and malignant intramuscular soft tissue tumors on MRI., Materials and Methods: Two blinded readers analyzed MR examinations of 90 consecutive patients with intramuscular soft tissue masses (group 1: MO, n = 20; group 2: malignant tumors, n = 70). Extent of edema around lesions was graded (0, none; 1, minimal edema; 2, moderate edema; 3, extensive edema). Edema-lesion ratio (ELR = ratio of the maximal diameter of the edema and the maximal diameter of the central lesion) was calculated. ROC analysis, Mann-Whitney U test, and Kappa test were used., Results: A total of 70% and 60% of patients with MO had edema grade 3 (reader 1/reader 2), 30%/40% edema grade 2. For the patients with malignant tumors, it was 2.9%/1.4% (edema grade 3) and 16%/23% (edema grade 2). Interrater reliability was substantial (kappa = 0.66). Extent of edema was significantly higher for patients of group 1 (p < 0.0001, both readers). Mean ELR was 3.60 (group 1) and 1.35 (group 2), with statistically significant differences (p < 0.0001). Grade 3 edema showed a sensitivity/specificity of 70%/97.1% (reader 1) and 60%/99% (reader 2) for diagnosing MO. For ELR > 2.0, sensitivity was 90% and specificity 91% for diagnosing MO., Conclusions: Extensive perilesional muscle edema on MRI of more than double the size of the central lesion is highly specific, but not pathognomonic for myositis ossificans in the early/intermediate stage in the differentiation to malignant intramuscular soft tissue lesions.

Objective: To test a 3D-hindfoot alignment (HA) measurement technique based on low-dose biplanar radiographs (BPRs) in a clinical setting and compare the results with 2D-HA measurements on long axial view radiographs (LARs)., Materials and Methods: This prospective study was approved by the local institutional review board. HA measurements on 3D-BPR and 2D-LAR of 50 patients (29 female; mean age 47 ± 16.6 years) were compared (positive values = valgus; negative values = varus). Two independent musculoskeletal radiologists (readers 1 and 2) performed 3D-HA measurements on BPR using a custom-made MATLAB code and measured HA on LAR during two separate readout sessions. Descriptive statistics and intraclass correlation coefficients (ICC) were calculated, and Bland-Altman plots were used for intermethod comparison., Results: Using BPRs, HA was 0.8° ± 9.°1 (range, -20.2 to 20.0) for reader 1, and 0.7° ± 9.5° (range, -21.2 to 18.3) for reader 2. HA on LARs was -2.0 ° ± 7.0° (range, -27.0° to 11.1°) for reader 1 and - 1.7° ± 7.0° (range, -24.1° to 14.3°) for reader 2. Interreader agreement for measurements was excellent, both for BPRs (ICC = 0.992; 95% CI:0.986-0.995) and LAR measurements (ICC = 0.962; 95% CI:0.932-0.978). Mean difference between the two methods was -2.43° (range, -29.4° to 25.6°) for reader 1 and -2.6° (range,-28.7° to 30.2°) for reader 2. On Bland-Altman plots, three measurements of reader 1 and six measurements of reader 2 were outside of the ±1.96 SD interval., Conclusion: Hindfoot alignment measurements on 3D-BPR have an excellent interreader agreement in a clinical setting. Large measurement errors can occur in individual patients using 2D-LAR alone. Therefore, we suggest using 3D-BPR measurements in daily routine for the assessment of HA, which are independent of rotational foot malpositioning.

Objective: To investigate the different morphologic types of the fovea capitis femoris and the spectrum of osseous spurs/osteophytes of the fovea in asymptomatic volunteers and patients with hip osteoarthritis., Material and Methods: Sixty-five patients (mean age 63.6 years) with radiographically confirmed osteoarthritis of the hip and 59 asymptomatic healthy volunteers (mean age 33.9 years) underwent non-contrast MRI of the hip joint. Two radiologists independently evaluated all images. Fovea morphology (standard type, diamond type, flat type, triangular type) as well as the frequency, size and location of spurs/osteophytes of the fovea were assessed. Descriptive and inferential statistics were applied., Results: The most frequent morphologic type of the fovea capitis femoris was the standard type for both asymptomatic volunteers (average 45%) and patients (average 49%). Osseous spurs were detected in 70% of the asymptomatic volunteers, and 97% of the patients had osteophytes. Spur size at all locations was significantly smaller in asymptomatic volunteers (range 1-2 mm) than osteophyte size in patients (range 1-4 mm) (p ≤ 0.035). In volunteers and patients, the spurs/osteophytes were most frequently located at the anterior border of the fovea capitis femoris., Conclusion: Smaller osseous spurs (<2 mm) at the border of the fovea capitis femoris are very common in asymptomatic volunteers and do not seem to be pathologic.

Objectives: To determine whether specific MRI findings are related to outcomes after lumbar transforaminal epidural steroid injections (TFESI) and to assess the inter-rater reliability of imaging diagnosis., Materials and Methods: A prospective outcomes study on 156 consecutive patients with 1-month follow-up outcomes data and MRI within 3 months of TFESI was conducted. Pain levels (numerical rating scale) (NRS) were recorded prior to injection. Overall 'improvement' was determined using the Patients Global Impression of Change (PGIC) scale and NRS data were collected at three time points post injection. Two radiologists independently evaluated all images blinded to treatment outcome for reliability of diagnosis. The Chi-square test compared MRI findings for the senior radiologist to 'improvement'. NRS change scores were compared to MRI findings with the unpaired t-test or ANOVA. Kappa and percent agreement assessed inter-rater agreement of diagnosis., Results: The only abnormality linked to 'improvement' (p = 0.03) and higher NRS change scores (p = 0.0001) at 1 month was the disc herniation morphology 'protrusion + sequestration'. Patients with degeneration by osteophytes (p = 0.034), grade 3 foraminal nerve root compression (p = 0.01) and foraminal/extraforaminal location of herniation (p = 0.014) also had higher 1 month NRS change scores. Reliability of diagnosis was 'fair' to 'substantial' depending on MRI findings., Conclusions: Patients with disc protrusion plus sequestration were significantly more likely to report overall improvement and more pain reduction at 1 month. Higher pain reduction was noted in patients with degeneration by osteophytes, grade 3 foraminal nerve root compression, or foraminal/extraforaminal disc herniation location.

Purpose: To prospectively characterize the MR appearance of the carpometacarpal (CMC) joint of the thumb in asymptomatic volunteers., Materials and Methods: Thirty-four asymptomatic volunteers (17 women, 17 men, mean age, 33.9 ± 9.2 years) underwent MR imaging of the thumb after approval by the local ethical committee. Two musculoskeletal radiologists independently classified visibility and signal intensity (SI) characteristics of the anterior oblique (AOL/beak ligament), the posterior oblique (POL), the intermetacarpal (IML), and the dorsoradial ligaments (DRL) on a three-point Likert scale. The thickness of all ligaments, cartilage integrity, and presence of joint fluid were assessed. The alignment of the first metacarpal base with the trapezium was quantified on sagittal and coronal planes., Results: The ligaments of the CMC joint were constantly visible in all volunteers for the POL and IML, and in all but one for the AOL and DRL. On intermediate-weighted fat-saturated images the POL (65 %/74 % reader 1/reader 2) and DRL (58 %/64 %) were commonly of increased SI, while the IML had a striated appearance in 91 %/76 % of subjects. The AOL showed a variable SI (36 %/42 % low, 27 %/27 % increased, 36 %/30 % striated). The IML was the thickest ligament with a mean of 2.9 mm/3.1 mm and the DRL the thinnest (1.2 mm/1.4 mm). There was a mean dorsal subluxation of 1.8 mm/2.0 mm and radial subluxation of 2.8 mm/3.4 mm of the metacarpal base. The AOL was significantly thicker in men (1.7 mm) than in women (1.2 mm; p = 0.02). Radial subluxation was significantly larger in men (3.4 mm) than in women (2.2 mm; p = 0.02). No subluxation in palmar or ulnar direction was seen., Conclusions: Radial and dorsal subluxation of the CMC joint can be a normal finding in a resting position at MR imaging. The CMC ligaments showed a considerable variability of signal intensity with a typically striated IML; thickness of the AOL is typically less than 2.2 mm, of the POL typically less than 2.9 mm.

Objective: To evaluate the association between hypertrophy of the tensor fasciae latae muscle and abductor tendon tears., Materials and Methods: Thirty-five patients who underwent MRI of the abductor tendons of the hip were included in this retrospective study. A subgroup of 18 patients was examined bilaterally. The area of the tensor fasciae latae muscle and the area of the sartorius muscle (size reference) were quantified at the level of the femoral head, and a ratio was calculated. Two radiologists assessed the integrity of the gluteus medius and minimus tendon in consensus. Data were analyzed with a Mann-Whitney U test., Results: Sixteen out of 35 patients (46 %) had a tear of the gluteus medius or minimus tendon. The ratio of the area of the tensor fasciae latae to the sartorius muscle was significantly higher (p = .028) in the group with an abductor tendon tear (median 2.25; Interquartile Range [IQR] = 1.97-3.21) compared to the group without any tears (median 1.91; IQR = 1.52-2.26). The bilateral subanalysis showed that in patients without a tear, the ratio of the two areas did not differ between each side (p = .966), with a median of 1.54 (primary side) and 1.76 (contralateral side). In patients with an abductor tendon tear the ratio was significantly higher (p = .031) on the side with a tear (median 2.81) compared to the contralateral healthy side (1.67)., Conclusion: Patients with abductor tendon tears showed hypertrophy of the tensor fasciae latae muscle when compared to the contralateral healthy side and to patients without a tear.

Objective: To establish a hindfoot alignment measurement technique based on low-dose biplanar radiographs and compare with hindfoot alignment measurements on long axial view radiographs, which is the current reference standard., Materials and Methods: Long axial view radiographs and low-dose biplanar radiographs of a phantom consisting of a human foot skeleton embedded in acrylic glass (phantom A) and a plastic model of a human foot in three different hindfoot positions (phantoms B1-B3) were imaged in different foot positions (20° internal to 20° external rotation). Two independent readers measured hindfoot alignment on long axial view radiographs and performed 3D hindfoot alignment measurements based on biplanar radiographs on two different occasions. Time for three-dimensional (3D) measurements was determined. Intraclass correlation coefficients (ICC) were calculated., Results: Hindfoot alignment measurements on long axial view radiographs were characterized by a large positional variation, with a range of 14°/13° valgus to 22°/27° varus (reader 1/2 for phantom A), whereas the range of 3D hindfoot alignment measurements was 7.3°/6.0° to 9.0°/10.5° varus (reader 1/2 for phantom A), with a mean and standard deviation of 8.1° ± 0.6/8.7° ± 1.4 respectively. Interobserver agreement was high (ICC = 0.926 for phantom A, and ICC = 0.886 for phantoms B1-B3), and agreement between different readouts was high (ICC = 0.895-0.995 for reader 1, and ICC = 0.987-0.994 for reader 2) for 3D measurements. Mean duration of 3D measurements was 84 ± 15/113 ± 15 s for reader 1/2., Conclusion: Three-dimensional hindfoot alignment measurements based on biplanar radiographs were independent of foot positioning during image acquisition and reader independent. In this phantom study, the 3D measurements were substantially more precise than the standard radiographic measurements.

Purpose: To compare the detection rate and visibility of the ligaments in the Lisfranc joint with a single 3D (-SPACE) MR sequence and three orthogonal PD fat-saturated sequences., Materials and Methods: Thirty-one asymptomatic feet and 15 patients with posttraumatic pain in the Lisfranc joint were evaluated with a 3D-SPACE-sequence (0.5 mm section thickness, acquisition time 10:22 min, secondary reformations) and three orthogonal PD fs sequences (2 mm section thickness, 9:20 min). The Lisfranc-ligament, the dorsal and plantar tarsometatarsal ligaments (TMT), the dorsal, interosseous, and plantar intermetatarsal ligaments (IMT) (24 ligaments for each foot) were assessed., Results: In asymptomatic feet, 692 ligaments were detected with the SPACE sequence, thereof 90.6 % exhibited normal signal, and most (96.9 %) were completely visible on one single image. A total of 659 ligaments were detected with the PD fs sequence, thereof 86.6 % yielded normal signal, and 28.5 % were completely visible on one single image. In patients, 327 ligaments were detected with SPACE, thereof 50.6 % appeared completely visible with high signal. On PD fs, 308 ligaments were detected, 42.2 % of the ligaments had high signals., Conclusions: The ligaments of the Lisfranc joint are better detected with a single 3D-SPACE sequence and secondary reformations than with three orthogonal PD fs sequences.

Objective: To describe an "indirect" cervical nerve root injection technique with a dorsal approach that should carry less inherent risk than the "direct" cervical transforaminal injection approach, and to compare the immediate post-injection results of the two procedures., Materials and Methods: The indirect and direct cervical nerve root injection procedures are described in detail. Fifty-three consecutive patients receiving the indirect nerve root injections during 2009-2010 were age- and gender-matched to 53 patients who underwent direct transforaminal nerve root injections performed in 2006. Pain level data were collected immediately before and 20-30 min after each procedure. The percentages of pain change in the two groups were compared using the unpaired Student's t test., Results: Fifty-two men (mean age 49) and 54 women (mean age 55) were included. The mean percentage of pain reduction for patients receiving indirect nerve root injections was 38.4% and for those undergoing the direct nerve root injections approach it was 43.2%. This was not significantly different (P = 0.455). No immediate or late adverse effects were reported after either injection procedure., Conclusions: The indirect cervical nerve root injection procedure is a potentially safer alternative to direct cervical transforaminal nerve root injections. The short-term pain reduction is similar using the two injection methods.