Prospective evaluation of ultrasound features of magnesium-based bioabsorbable screw resorption in pediatric fractures.

OBJECTIVE: Bioabsorbable magnesium-based alloy screws release gas upon resorption. The resulting findings in the adjacent soft tissues and joints may mimic infection. The aim of the study was to evaluate the ultrasound (US) findings in soft tissues and joints during screw resorption. METHODS: Prospectively acquired US studies from pediatric patients treated with magnesium screws were evaluated for screw head visibility, posterior acoustic shadowing, twinkling artifact, foreign body granuloma, gas (soft tissue, intra-articular), alterations of the skin and subcutaneous fat, perifascial fluid, localized fluid collections, hypervascularization, and joint effusion. RESULTS: Sixty-six US studies of 28 pediatric patients (nfemale = 9, nmale = 19) were included. The mean age of the patients at the time of surgery was 10.84 years; the mean time between surgery and ultrasound was 128.3 days (range = 6-468 days). The screw head and posterior acoustic shadowing were visible in 100% of the studies, twinkling artifact in 6.1%, foreign body granuloma in 92.4%, gas locules in soft tissue in 100% and intra-articular in 18.2%, hyperechogenicity of the subcutaneous fat in 90.9%, cobblestoning of the subcutaneous fat in 24.2%, loss of normal differentiation between the epidermis/dermis and the subcutaneous fat in 57.6%, localized fluid collection in 9.9%, perifascial fluid in 12.1%, hypervascularization in 27.3%, and joint effusion in 18.2%. CONCLUSION: US findings in pediatric patients treated with magnesium screws strongly resemble infection, but are normal findings in the setting of screw resorption. CLINICAL RELEVANCE STATEMENT: Bioabsorbable magnesium-based alloy screws release gas during resorption. The resulting US findings in the adjacent soft tissues and joints in pediatric patients may mimic infection, but are normal findings. KEY POINTS: • Bioabsorbable magnesium-based alloy screws release gas upon resorption. • The resulting ultrasound findings in children's soft tissues and joints closely resemble those of soft tissue infection or osteosynthesis-associated infection. • Be familiar with these ultrasound findings in order to avoid inadvertently misdiagnosing a soft tissue infection or osteosynthesis-associated infection.

Prospective measurement of the width of cerebrospinal fluid spaces by cranial ultrasound in neurologically healthy children aged 0-19 months.

BACKGROUND: Ultrasound (US) is often the first method used to look for brain or cerebrospinal fluid (CSF) space pathologies. Knowledge of normal CSF width values is essential. Most of the available US normative values were established over 20 years ago, were obtained with older equipment, and cover only part of the age spectrum that can be examined by cranial US. This prospective study aimed to determine the normative values of the widths of the subarachnoid and internal CSF spaces (craniocortical, minimal and maximal interhemispheric, interventricular, and frontal horn) for high-resolution linear US probes in neurologically healthy infants and children aged 0-19 months and assess whether subdural fluid collections can be delineated. METHODS: Two radiologists measured the width of the CSF spaces with a conventional linear probe and an ultralight hockey-stick probe in neurologically healthy children not referred for cranial or spinal US. RESULTS: This study included 359 neurologically healthy children (nboys = 178, 49.6%; ngirls = 181, 50.4%) with a median age of 46.0 days and a range of 1-599 days. We constructed prediction plots, including the 5th, 50th, and 95th percentiles, and an interactive spreadsheet to calculate normative values for individual patients. The measurements of the two probes and the left and right sides did not differ, eliminating the need for separate normative values. No subdural fluid collection was detected. CONCLUSION: Normative values for the widths of the subarachnoid space and the internal CSF spaces are useful for evaluating intracranial pathology, especially when determining whether an increase in the subarachnoid space width is abnormal.

Diffusion-Weighted Imaging Distinguishes Between Osteomyelitis, Bone Marrow Edema, and Healthy Bone on Forefoot Magnetic Resonance Imaging.

BACKGROUND: Diagnosis of osteomyelitis by imaging can be challenging. The feasibility of diffusion-weighted imaging (DWI) as ancillary sequence was evaluated in this study. PURPOSE: To evaluate DWI for differentiation between osteomyelitis, bone marrow edema, and healthy bone on forefoot magnetic resonance imaging (MRI). STUDY TYPE: Prospective. SUBJECTS: A total of 60 consecutive patients undergoing forefoot MRI divided into three study groups (20 subjects each): osteomyelitis, bone marrow edema, and healthy bone. FIELD STRENGTH/SEQUENCE: A 1.5T and 3T MRI scanners; readout-segmented multishot echo planar DWI. ASSESSMENT: Two independent radiologists measured apparent diffusion coefficient (ADC) values within abnormal or healthy bone. STATISTICAL TESTS: ADC values were compared between groups (pairwise t-test with Bonferroni-Holm correction for multiple testing). Intraclass correlation coefficient (ICC) was calculated to assess inter-reader agreement. Threshold ADC values were determined as the cutoffs that maximized the sum of sensitivity and specificity. Receiver operating characteristic (ROC) analysis was performed with statistical threshold of P < 0.05. RESULTS: Inter-reader agreement was 0.92 in the healthy bone group and 0.78 in both the edema and osteomyelitis groups. Average ADC values were significantly different between groups: 1432 ± 222 × 10-6  mm2 /sec (osteomyelitis), 1071 ± 196 × 10-6  mm2 /sec (bone marrow edema), and 277 ± 89 × 10-6  mm2 /sec (healthy bone). A threshold ADC value of 534 × 10-6  mm2 /sec distinguishes between healthy and abnormal bone with specificity and sensitivity of 100% each. For distinction between osteomyelitis and bone marrow edema, two cutoff values were determined: a 95%-specificity cutoff indicating osteomyelitis (>1320 × 10-6  mm2 /sec) and a 95%-sensitivity cutoff indicating bone marrow edema (<1155 × 10-6  mm2 /sec). Diagnostic accuracy of 95% was achieved for 73% (29/40) of the subjects. DATA CONCLUSION: DWI with ADC maps distinguishes between healthy and abnormal bone on forefoot MRI. Calculated cutoff values allow confirmation or exclusion of osteomyelitis in a high proportion of subjects. EVIDENCE LEVEL: 2 TECHNICAL EFFICACY: Stage 2.

Radiographic features of magnesium-based bioabsorbable screw resorption in paediatric fractures.

BACKGROUND: Resorption of magnesium-based alloy bioabsorbable screws produces hydrogen gas, which can be mistaken as a sign of infection and may affect the physis or fixed bone fragment. OBJECTIVE: We evaluated the temporal and spatial occurrence of gas and the occurrence of a breakage of the fixed bone fragment or screw following magnesium screw fixation. MATERIALS AND METHODS: Radiographs of paediatric patients treated with magnesium screws were retrospectively reviewed. Temporal occurrence and distribution of gas in the bone, the physis and soft tissues, breakage of the screw or fixed bone fragment and joint effusion were assessed. RESULTS: One hundred and three radiographs in 35 paediatric patients were reviewed (mean age: 10.6 years). Follow-up ranged from 1 to 730 days. Gas in the bone increases up to week 5, remains constant up to week 16 and then decreases. Gas in soft tissues, intra-articular gas and joint effusions gradually reduce over time. In 1/23 (4.3%) patients with an open physis, gas intrusion into the physis occurred. Breakage of the bone fragment fixated by the screw was observed in 4/35 (11.4%) patients within the first 6 weeks. Screw breakage was observed in 16/35 (45.7%) patients, with a median time to first detection of 300 days. CONCLUSION: Gas bubbles in bone and soft tissue are normal findings in the context of screw resorption and should not be confused with soft-tissue infection or osteomyelitis. Gas is rarely visible in the physis. Breakage of the fixed bone fragment and/or screw can occur.

Organ-based tube current modulation and bismuth eye shielding in pediatric head computed tomography.

BACKGROUND: Exposure of the eye lens to ionizing radiation results in cataract. Several dose optimization techniques to protect the lens are available for computed tomography (CT). OBJECTIVE: The radiation dose to the eye lens, volume CT dose index (CTDIvol) and image quality of various methods of dose optimization were evaluated for pediatric head CT: automated tube current modulation (ATCM), automated tube voltage selection (ATVS), organ-based tube current modulation (OBTCM) and bismuth shielding. MATERIALS AND METHODS: An anthropomorphic phantom of a 5-year-old child was scanned with nine protocols: no dose optimization technique and then adding different dose optimization techniques alone and in combination. Dose to the eye, thyroid and breast were estimated using metal oxide semiconductor field effect transistor (MOSFET) dosimetry. CTDIvol, influence of timing of shield placement, image noise and attenuation values in 13 regions of interest of the head and subjective image quality were compared. RESULTS: The eye shield significantly reduced the eye lens dose when used alone, to a similar degree as when using all software-based techniques together. When used in combination with software-based techniques, the shield reduced the eye lens dose by up to 45% compared to the no dose optimization technique. Noise was significantly increased by the shield, most pronounced in the anterior portion of the eye. CONCLUSION: The combination of ATCM, ATVS, OBTCM and a bismuth shield, with the shield placed after acquiring the localizer image, should be considered to reduce the radiation dose to the eye lens in pediatric head CT.

Diagnostic utility of perilesional muscle edema in myositis ossificans.

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.

Fluoroscopy-guided versus CT-guided Lumbar Steroid Injections: Comparison of Radiation Exposure and Outcomes.

Purpose To compare the radiation exposure for participants and interventionalists as well as participant outcomes between fluoroscopy-guided versus CT-guided lumbar spinal injections. Materials and Methods This prospective, nonrandomized observational study included 1446 participants (mean age, 60.6 years; range, 18-91 years) who received transforaminal epidural injections or facet joint injections under fluoroscopic or CT guidance between October 2009 and April 2016. Effective doses were estimated by conversion from dose-area product for fluoroscopy-guided injections and dose-length product for CT-guided injections. Radiation exposure for interventionalists was measured with dosimeters at the body and wrist. The Patient Global Impression of Change (PGIC) scale was used to assess clinical participant outcomes at 1 day, 1 week, and 1 month after lumbar spine injections. Student t and χ2 tests were used for statistical analysis. Results The mean effective participant dose for fluoroscopy-guided lumbar transforaminal epidural injections was 0.24 mSv ± 0.22, compared with 0.33 mSv ± 0.10 for CT-guided injections (P < .003). The mean effective participant dose for fluoroscopy-guided lumbar facet joint injections was 0.10 mSv ± 0.11, compared with 0.33 mSv ± 0.13 for CT-guided injections (P < .001). Radiation exposure for the interventionalist was higher during fluoroscopy-guided compared with CT-guided lumbar transforaminal epidural injections (body: 0.42 × 10-3 mSv ± 0.99 vs 0.11 × 10-3 mSv ± 0.44, P < .03; wrist: 1.44 × 10-3 mSv ± 2.69 vs 0.14 × 10-3 mSv ± 0.55, P < .001). Radiation exposure of the wrist for the interventionalist was higher during fluoroscopy-guided compared with CT-guided lumbar facet injections (0.46 × 10-3 mSv ± 0.93 vs 0.06 × 10-3 mSv ± 0.24, respectively; P < .006). Clinical participant outcomes as determined with the PGIC scale did not differ between fluoroscopy-guided and CT-guided injections (P = .15-.96). Conclusion Radiation exposure in fluoroscopy-guided lumbar spinal injections was lower for participants and higher for physicians when compared with CT-guided injections; however, no associations were observed between clinical participant outcomes and type of imaging-guided injection technique at all evaluated time points. © RSNA, 2019.

Pincer-type MRI morphology seen in over a third of asymptomatic healthy volunteers without femoroacetabular impingement.

BACKGROUND: In daily routine, pincer femoroacetabular impingement (FAI) findings are often seen without a clinical diagnosis of pincer FAI. PURPOSE: To assess the presence of pincer FAI MRI findings in asymptomatic volunteers with negative impingement test versus patients with clinically confirmed FAI. STUDY TYPE: Case-control study. POPULATION: Sixty-three asymptomatic volunteers and 63 matched patients with FAI were included. FIELD STRENGTH/ SEQUENCE: A coronal T1 -weighted turbo spin-echo sequence as well as a 3D oblique transverse water-excitation true fast imaging sequence at 1.5T. ASSESSMENT: The volunteers underwent standard MRI of the hip, and patients underwent MR arthrography of the symptomatic hip using the same MR sequences. Measurements of cranial acetabular version, acetabular depth, and lateral center-edge angle were performed independently by three fellowship-trained musculoskeletal radiologists. STATISTICAL TESTS: Descriptive statistics, Mann-Whitney U-test, Unpaired t-test, receiver operating characteristics (ROC), Intraclass correlation coefficient (ICC). RESULTS: Forty-one percent (26/63, reader 1), 32% and 37% (20 and 23/63, reader 2/3) of asymptomatic volunteers had at least one positive MR finding for pincer-FAI. Patients with pincer or mixed-type FAI had cranial retroversion of the acetabulum of -0.2° ± 7.1 (mean ± standard deviation) for reader 1 and -0.3° ± 5.5/-0.2° ± 4.8 for reader 2 / reader 3, while asymptomatic volunteers had an anteversion of 6.2° ± 6.4 (reader 1) and 3.2° ± 4.9/3.1° ± 6.5 (readers 2/3): This difference was statistically significant (P ≤ 0.002), but there was a large overlap between the groups. Acetabular depth measurements were very similar for patients with either pincer or mixed-type FAI (5.1-5.3 mm ± 3.1) and volunteers (5.2-6.1 mm ± 2.6), without a statistically significant difference (P ≤ 0.50). Lateral center-edge angle was also similar in patients with either pincer or mixed-type FAI (32.1-35.1° ± 9.1) and volunteers (30.7-33.2° ± 6.5), without a statistically significant difference (P ≤ 0.28). DATA CONCLUSION: There is a large overlap in pincer-type MRI findings between patients with symptomatic FAI and asymptomatic volunteers. More than a third of volunteers exhibited at least one positive pincer-type MRI finding. LEVEL OF EVIDENCE: 1 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2019;49:1296-1303.

Reliable semiquantitative whole-joint MRI score for the shoulder joint: The shoulder osteoarthritis severity (SOAS) score.

BACKGROUND: Shoulder osteoarthritis causes severe pain and functional disability. Preventive surgical procedures aiming to halt the progression of degenerative changes are increasingly applied. However, no MRI-based score exists that may be applied for scoring of osteoarthritic changes and their progression. PURPOSE: To establish a semiquantitative MRI-based shoulder osteoarthritis severity (SOAS) evaluation system and to test its reliability. STUDY TYPE: Retrospective. SUBJECTS: A total of N = 60 patients (73.2 ± 7.3 years; 30/60 female) was included; n = 15 subjects for each of the four radiographic grades of osteoarthritis (Samilson score 0 to 3). ASSESSMENT: Based on the MRIs of the shoulder, the SOAS scoring system was created. All MRIs were assessed by six readers. The severity of degeneration was evaluated for: rotator cuff, labral-bicipital-complex, cartilage, osseous findings, joint capsule, and acromion. The total SOAS score ranged between 0 (absence of osteoarthritis) and 100 (most severe osteoarthritis). SOAS scores were correlated with radiographic Samilson, Hamada and Kellgren-Lawrence (KL) gradings. STATISTICS: Pearson correlations, t-tests, receiver operating characteristics (ROC) and interclass correlation coefficients (ICC). RESULTS: Intra- (ICC = 0.99) and interreader agreement (ICC 0.96-0.98) for the total SOAS score was excellent. The range of SOAS scores was from 1 to 88. SOAS correlated significantly with radiographic Samilson and KL scores (R = 0.82, P < 0.001), but not with Hamada scores (R = -0.07, P = 0.60). The highest correlations with Samilson scores were found for cartilage (R = 0.82, P < 0.001) and osseous findings (R = 0.86, P < 0.001). SOAS scores were significantly different between different Samilson grades (Samilson 0, 13.4 ± 7.6; Samilson 1, 26.0 ± 9.1; Samilson 2, 38.2 ± 19.2; Samilson 3, 65.5 ± 13.0; P < 0.05). The ability of the SOAS score to predict incident radiographic shoulder OA (KL grade ≥2) was excellent (AUC = 0.91; P < 0.001). DATA CONCLUSION: The newly developed semiquantitative MRI-based SOAS score represents the severity of global shoulder OA and structure-specific shoulder degeneration with excellent reliability in a standardized manner and may therefore be helpful in MRI research studies of the shoulder. LEVEL OF EVIDENCE: 3 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2018.

Arthroscopic Hip Surgery: Frequency of Postoperative MR Arthrographic Findings in Asymptomatic and Symptomatic Patients.

Purpose To determine and compare the frequency of imaging abnormalities in asymptomatic and symptomatic patients after arthroscopic hip surgery. Materials and Methods This study was approved by the institutional review board. Informed consent was obtained from all patients. Thirty-four patients (17 asymptomatic and 17 symptomatic patients) underwent 1.5-T magnetic resonance (MR) arthrography of the hip 1 year after arthroscopic treatment of femoroacetabular impingement. Two readers independently analyzed all MR arthrographic images for the presence of abnormal imaging findings, including capsular adhesions at the femoral neck, obliteration of the paralabral sulcus, labral defects, and defects of the hip capsule in several anatomic positions (anterior to posterior). Postoperative findings were compared with linear and generalized linear mixed-effects regression models. Results Capsular adhesions at the anterior femoral neck were present in 12 of the 34 patients (35%), and there were no differences between the groups or readers (P = .99). The paralabral sulcus was obliterated in at least one anatomic location in 94% (reader 1, 32 of 34 patients) and 100% (reader 2, 34 of 34 patients) of patients (P = .99). Residual labral tears were detected in 35% of asymptomatic patients (six of 17 patients) and 41% of symptomatic patients (seven of 17 patients) by reader 1 and in 53% of asymptomatic and symptomatic patients (nine of 17 patients in each group) by reader 2, without significant differences between the groups (P = .81). Defects of the hip capsule were more common in asymptomatic patients (77% [13 of 17 patients] for reader 1 and 53% [nine of 17 patients] for reader 2) than in symptomatic patients (59% [10 of 17 patients] for reader 1 and 47% [eight of 17 patients] for reader 2), but without significant differences (P = .33). Conclusion Obliteration of the paralabral sulcus was the most frequent finding after arthroscopic hip surgery in both asymptomatic and symptomatic patients, and capsular adhesions at the anterior femoral neck were present in 35% of patients in both groups. © RSNA, 2016.

Hip MRI: Prevalence of articular cartilage defects and labral tears in asymptomatic volunteers. A comparison with a matched population of patients with femoroacetabular impingement.

PURPOSE: To prospectively compare defects of the articular cartilage and labrum in asymptomatic volunteers and in patients with femoroacetabular impingement (FAI) matched for age and gender. MATERIALS AND METHODS: This cross-sectional study was institutional review board approved. A total of 63 asymptomatic volunteers and 63 patients with symptomatic FAI between 20 and 50 years underwent 1.5 Tesla MRI (coronal T1-weighted, coronal intermediate-weighted fat saturated, transverse oblique true fast imaging with steady-state precession [FISP], sagittal dual echo steady state [DESS] sequence). Two radiologists independently assessed defects of the cartilage and labrum at six positions. Statistics included Mann-Whitney U-test and Spearman's rho. RESULTS: A defect of the articular cartilage and/or labrum was present on average in 57% of asymptomatic volunteers, compared with 80% of symptomatic patients (P ≤ 0.028). A total of 14% of volunteers had acetabular cartilage defects, and 6% had femoral cartilage defects, compared with 47% and 30% in symptomatic patients (P ≤ 0.001 and P ≤ 0.003), respectively. Labrum defects were seen in 44% of volunteers versus 61% of patients (P ≤ 0.12). Both cartilage and labral defects were more commonly encountered in male volunteers than in female volunteers, with the largest difference seen for the acetabular cartilage (P ≤ 0.02). In all groups, the majority of cartilage and labrum defects were encountered in the anterosuperior, superior, and posterosuperior position. CONCLUSION: A substantial number of asymptomatic volunteers had labral tears, defects of the acetabular cartilage, and to a lesser degree, defects of the femoral cartilage; our data demonstrate that not all cartilage and labral defects of the hip joint are symptomatic and that a similar predilection for location of defects is found in volunteers and FAI patients. LEVEL OF EVIDENCE: 2 Technical Efficacy: Stage 3 J. MAGN. RESON. IMAGING 2017;46:440-451.

Is there an Added Value of T1-Weighted Contrast-Enhanced Fat-suppressed Spin-Echo MR Sequences Compared to STIR Sequences in MRI of the Foot and Ankle?

OBJECTIVES: To prospectively compare T1-weighted fat-suppressed spin-echo magnetic resonance (MR) sequences after gadolinium application (T1wGdFS) to STIR sequences in patients with acute and chronic foot pain. METHODS: In 51 patients referred for MRI of the foot and ankle, additional transverse and sagittal T1wGdFS sequences were obtained. Two sets of MR images (standard protocol with STIR or T1wGdFS) were analysed. Diagnosis, diagnostic confidence, and localization of the abnormality were noted. Standard of reference was established by an expert panel of two experienced MSK radiologists and one experienced foot surgeon based on MR images, clinical charts and surgical reports. Patients reported prospectively localization of pain. Descriptive statistics, McNemar test and Kappa test were used. RESULTS: Diagnostic accuracy with STIR protocol was 80% for reader 1, 67% for reader 2, with contrast-protocol 84%, both readers. Significance was found for reader 2. Diagnostic confidence for reader 1 was 1.7 with STIR, 1.3 with contrast-protocol; reader 2: 2.1/1.7. Significance was found for reader 1. Pain location correlated with STIR sequences in 64% and 52%, with gadolinium sequences in 70% and 71%. CONCLUSIONS: T1-weighted contrast material-enhanced fat-suppressed spin-echo magnetic resonance sequences improve diagnostic accuracy, diagnostic confidence and correlation of MR abnormalities with pain location in MRI of the foot and ankle. However, the additional value is small. KEY POINTS: • Additional value of contrast-enhanced MR over standard MR with STIR sequences exists. • There is slightly more added value for soft tissue than for bony lesions. • This added value is limited. • Therefore, application of contrast material cannot be generally recommended.

C-arm flat-panel CT arthrography of the shoulder: Radiation dose considerations and preliminary data on diagnostic performance.

OBJECTIVES: To investigate radiation dose and diagnostic performance of C-arm flat-panel CT (FPCT) versus standard multi-detector CT (MDCT) shoulder arthrography using MRI-arthrography as reference standard. METHODS: Radiation dose of two different FPCT acquisitions (5 and 20 s) and standard MDCT of the shoulder were assessed using phantoms and thermoluminescence dosimetry. FPCT arthrographies were performed in 34 patients (mean age 44 ± 15 years). Different joint structures were quantitatively and qualitatively assessed by two independent radiologists. Inter-reader agreement and diagnostic performance were calculated. RESULTS: Effective radiation dose was markedly lower in FPCT 5 s (0.6 mSv) compared to MDCT (1.7 mSv) and FPCT 20 s (3.4 mSv). Contrast-to-noise ratios (CNRs) were significantly (p < 0.05) higher in FPCT 20-s versus 5-s protocols. Inter-reader agreements of qualitative ratings ranged between к = 0.47-1.0. Sensitivities for cartilage and rotator cuff pathologies were low for FPCT 5-s (40 % and 20 %) and moderate for FPCT 20-s protocols (75 % and 73 %). FPCT showed high sensitivity (81-86 % and 89-99 %) for bone and acromioclavicular-joint pathologies. CONCLUSION: Using a 5-s protocol FPCT shoulder arthrography provides lower radiation dose compared to MDCT but poor sensitivity for cartilage and rotator cuff pathologies. FPCT 20-s protocol is moderately sensitive for cartilage and rotator cuff tendon pathology with markedly higher radiation dose compared to MDCT. KEY POINTS: • FPCT shoulder arthrography is feasible with fluoroscopy and CT in one workflow. • A 5-s FPCT protocol applies a lower radiation dose than MDCT. • A 20-s FPCT protocol is moderately sensitive for cartilage and tendon pathology.

The Legend of the Luschka Tubercle and Its Association With Snapping Scapulae: Osseous Morphology of Snapping Scapulae on CT Images.

OBJECTIVE: The purpose of this article is to determine the osseous morphology of snapping scapulae on CT images. MATERIALS AND METHODS: Retrospectively, 2D and 3D CT images of the scapulae of 35 patients with snapping scapula were compared with 35 age-matched control group subjects. Two observers analyzed the following parameters: presence of the Luschka tubercle; abnormalities of the bones and periscapular soft tissues; shape, thickness, and length of the superior angle of the scapula; craniocaudal length of the scapula; minimum distance between the scapula and rib cage; depth of the subscapular fossa; and the superomedial angle. RESULTS: In patients with snapping scapulae, observer 1 did not find any Luschka tubercles, whereas observer 2 detected one; in the control group both observers found two Luschka tubercles (p > 0.49). One scapular osteochondroma was found in the group with snapping scapulae. No further abnormalities of the rib cage or periscapular soft tissues were found in that group. The superior angle of the scapula was significantly thicker in the snapping scapula group compared with the control group (4.8 ± 1.3 mm vs 4.0 ± 1.0 mm, p < 0.012). The subscapular fossa was significantly deeper in patients with snapping scapula than in control group subjects (25.7 ± 5.2 mm vs 21.8 ± 5.0 mm, p < 0.005). The remaining parameters did not differ significantly between the groups. CONCLUSION: The Luschka tubercle was rarely observed and not associated with a snapping scapula. However, the superior angle of the scapula was significantly thicker and the subscapular fossa was significantly deeper in patients with snapping scapula than in control group subjects.

Frequency of Arthritis-Like MRI Findings in the Forefeet of Healthy Volunteers Versus Patients With Symptomatic Rheumatoid Arthritis or Psoriatic Arthritis.

OBJECTIVE: The objective of the present study is to evaluate arthritis-like findings on MRI studies of the forefeet of healthy volunteers versus patients with symptomatic rheumatoid arthritis (RA) or psoriatic arthritis (PsA). MATERIALS AND METHODS: Two observers analyzed MR images of the forefeet of 31 healthy volunteers, 30 patients with symptomatic RA, and 30 patients with symptomatic PsA, to identify MRI patterns of RA or PsA (e.g., bone marrow edema [BME], erosions, tenosynovitis, joint effusion, periarticular soft-tissue edema, or bony proliferations) on the basis of the Outcome Measures in Rheumatoid Arthritis Clinical Trial RA MRI scoring system and the PsA MRI scoring system. The Mann-Whitney test with Bonferroni correction was used for statistical analysis. RESULTS: Reader 1 found BME in 14 healthy volunteers (45%), whereas reader 2 found BME in 10 volunteers (32%). Tenosynovitis was observed by reader 1 in three healthy volunteers (10%). Joint effusion was found by reader 1 in seven healthy volunteers (23%) and by reader 2 in three volunteers (10%); the mean intensity grades for these findings were low (range, 1-1.33). Erosions, soft-tissue edema, and bony proliferations were not found in the forefeet of healthy volunteers. Reader 1 and reader 2 observed all arthritis-like features on the MR images of patients with RA. The percentages of patients with RA who had such MRI features, as identified by reader 1 and reader 2, respectively, were as follows: BME, 83% and 80%; erosions, 40% and 40%; tenosynovitis, 33% and 17%; effusion, 87% and 53%; soft-tissue edema, 20% and 27%; and bony proliferations, 3% and 3%. The percentages of patients with PsA who were found to have arthritis-like findings on MR images, as determined by reader 1 and reader 2, respectively, were as follows: BME, 70% and 67%; erosions, 20% and 20%; tenosynovitis, 57% and 50%; effusion, 70% and 37%; and soft-tissue edema, 60% and 53%. Bony proliferations were observed by reader 2 only in 7% of patients with PsA. The mean minimum intensity grade was 1 (for tenosynovitis in patients with RA, as observed by reader 2), whereas the maximum intensity grade was 2.53 (for erosions in patients with RA, as observed by reader 1). Tenosynovitis and soft-tissue edema were observed more frequently in patients with PsA than in patients with RA (p = 0.001-0.059). CONCLUSION: On the forefoot of healthy volunteers, mild BME is a common finding, and tenosynovitis and joint effusion are occasional findings. The frequency and intensity of arthritis-like findings on MRI are similar in patients with RA and PsA, with the exception of tenosynovitis and soft-tissue edema, which are more frequently observed in patients with PsA than in patients with RA.

Imaging of Individual Anatomical Risk Factors for Patellar Instability.

This review article presents several pitfalls and limitations of image interpretation of anatomical risk factors for patellar instability. The most important imaging examinations for the work-up of patients with patellar instability are the true lateral radiograph and transverse computed tomography (CT) or MR images of the knee. Primary anatomical risk factors are an insufficient medial patellofemoral ligament (MPFL), patella alta, trochlear dysplasia, increased distance from the tibial tuberosity to the trochlear groove (TTTG), and torsional limb parameters. Limitations of the Caton-Deschamps index are related to the clear identification of the patellar and tibial articular margin. Classification of trochlear dysplasia according to the Dejour system on radiographs and MR images revealed a weak reliability. The comparability of TTTG values obtained on CT and MR images at various flexion angles and different varus alignments of the knee is limited. Thus MRI performed with a dedicated knee coil may underestimate the TTTG distance compared with CT images. Increased lateral patellar tilt is a consequence of primary anatomical risk factors rather than an independent anatomical risk factor for patellar instability. The pretest likelihood of a torn MPFL on MR images is very high after an acute episode of lateral patellar dislocation. Surgical restoration of the patellofemoral joint stability addresses the complex multifactorial biomechanics by a custom-made management such as MPFL reconstruction, sulcus-deepening trochleoplasty, as well as medialization and distalization of the tibial tubercle. Quantification of anatomical risk factors for patellar instability in each person is important for highly individual treatment.

Ultrasound of the coracoacromial ligament in asymptomatic volunteers and patients with shoulder impingement.

BACKGROUND: The coracoacromial ligament is part of the coracoacromial arch, which is considered to be involved in shoulder impingement. PURPOSE: To compare the coracoacromial ligament on ultrasound in asymptomatic volunteers and in patients with subacromial shoulder impingement. MATERIAL AND METHODS: Twenty-nine asymptomatic volunteers (mean age, 35.5 years) and 29 patients (mean age, 49.9 years) with shoulder impingement, diagnosed by experienced shoulder surgeons, were prospectively included. Two radiologists obtained and analyzed ultrasound images of the coracoacromial ligament in the longitudinal axis. RESULTS: The ligament thickness was 1.4 ± 0.2 mm at its midportion, 1.8 ± 0.4 mm at the coracoid, and 2.1 ± 0.6 mm at the acromion in asymptomatic volunteers compared with 1.3 ± 0.2 mm, 1.9 ± 0.5 mm, and 1.9 ± 0.5 mm in impingement patients for observer 1. The ligament length was 30.6 ± 2.4 mm in asymptomatic volunteers compared with 30.4 ± 3.6 mm in impingement patients for observer 1. An anteriorly convex shape of the superficial contour of the coracoacromial ligament was significantly more frequent in impingement patients compared with asymptomatic volunteers for both observers (observer 1: 10% (3/29) versus 45% (13/29), P value <0.01; observer 2: 10% (3/29) versus 38% (11/29), P value <0.03). The comparison of the remaining parameters of the coracoacromial ligament, such as the thickness, length, echogenicity, and fibrillation did not reveal significant differences between volunteers and patients. CONCLUSION: While thickness or length of the coracoacromial ligament were similar in volunteers and patients with shoulder impingement, an anteriorly convex shape of the superficial contour of the coracoacromial ligament was significantly more frequent in impingement patients compared with asymptomatic volunteers.

Does pain relief by CT-guided indirect cervical nerve root injection with local anesthetics and steroids predict pain relief after decompression surgery for cervical nerve root compression?

BACKGROUND: The relationship of pain relief from a recently presented CT-guided indirect cervical nerve root injection with local anesthetics and steroids to surgical decompression as a treatment for single-level cervical radiculopathy is not clear. This retrospective study aimed to compare the immediate and 6-week post-injection effects to the short- and long-term outcomes after surgical decompression, specifically in regard to pain relief. METHODS: Patients (n = 39, age 47 ± 10 years) who had undergone CT-guided indirect injection with local anesthetics and steroids as an initial treatment for single cervical nerve root radiculopathy and who subsequently needed surgical decompression were included retrospectively. Pain levels (VAS scores) were monitored before, immediately after, and 6 weeks after injection (n = 34), as well as 6 weeks (n = 38) and a mean of 25 months (SD ± 12) after surgical decompression (n = 36). Correlation analysis was performed to find potential associations of pain relief after injection and after surgery to investigate the predictive value of post-injection pain relief. RESULTS: There was no correlation between immediate pain relief after injection (-32 ± 27 %) and 6 weeks later (-7 ± 19 %), (r = -0.023, p = 0.900). There was an association by tendency between immediate pain relief after injection and post-surgical pain relief at 6 weeks (-82 ± 27 %), (r = 0.28, p = 0.08). Pain relief at follow-up remained high at -70 ± 21 % and was correlated with the immediate pain amelioration effect of the injection (r = 0.37, p = 0.032). Five out of seven patients who reported no pain relief from injection had a pain relief from surgery in excess of 50 %. CONCLUSIONS: The amount of immediate radiculopathic pain relief after indirect cervical nerve root injection is associated with the amount of pain relief achieved at long-term follow-up after surgical decompression of single-level cervical radiculopathy. Patients can still expect sufficient pain relief from surgery even if they did not respond to the cervical infiltration.

The tibial-tubercle trochlear groove distance in patients with trochlear dysplasia: the influence of the proximally flat trochlea.

PURPOSE: Increased tibial tubercle trochlear groove distance (TT-TG) is frequently associated with trochlear dysplasia (TD). Since the trochlear groove appears more distally in patients with TD compared to controls, it is unknown whether TT-TG might be comparable and meaningful. METHODS: Fifty patients with TD were retrospectively analysed and compared to 52 age- and gender-matched patients (CG). TT-TG was measured on transverse MR images, as the distance between the trochlear groove of minimal 2 mm depth proximally and the centre of the patellar tendon at its distal insertion. The height of the femoral reference point above joint line was recorded for both groups. TT-TG measurement was repeated in CG using the first (P25), second (P50) and third quartile (P75) above joint line of TD. RESULTS: Patients with TD had a significantly smaller vertical distance between the most proximal trochlear deepening and the femorotibial joint line (20.6 mm, range 10.3-30.9) compared to CG (33.8 mm, range 25.4-41.1; p < 0.001). TT-TG values measured at 20 mm (P50) and 15 mm (P25) proximal to the femorotibial joint line were significantly smaller compared when measured with the most proximal reference point [1.8 mm (95 % CI 1.3-2.3, p < 0.001) and 2.4 mm (95 % CI 1.9-3.0, p < 0.001)] in CG. The inter-rater reliability was excellent (ICC 0.99). CONCLUSION: TT-TG distance depends significantly on the femoral reference point. Since the trochlear groove is seen more distally in patients with TD compared to controls, TT-TG of the patients with highest risk of recurrent patellar instability might be underestimated. LEVEL OF EVIDENCE: Diagnostic study, Level I.