High-resolution ultrasound of the paratenon of the Achilles calcaneal tendon: anatomical study and description of the paratendinous injection technique.

PURPOSE: The aim of this study is to determine if ultrasound (US) allows a precise assessment of the paratenon (PT) of the Achilles calcaneal tendon (AT), and to anatomically describe the US-guided paratendinous injection technique. METHODS: This study was initially conducted on eight cadaveric specimens using high-resolution ultrasound (HRUS) to examine the PT appearance, thickness, and its relationships with the AT, plantaris tendon (PLT), Kager's fat pad (KFP), sural nerve (SN), and fascia cruris (FC). US-guided paratendinous injection of China ink was performed in all specimens, followed by anatomical dissection to assess injectate distribution. Then, HRUS study of the PT was carried out bilaterally in twenty asymptomatic volunteers (40 legs). Two musculoskeletal radiologists recorded all data in consensus except PT thickness in volunteers which was recorded independently in order to calculate intra and inter-observer reliability. RESULTS: The PT was consistently identified with HRUS along its entire course in both cadaveric specimens (8/8) and volunteers (40/40). The mean PT thickness was 0.54 mm in cadavers and 0.39 mm in vivo, without any correlation with the AT thickness. Intra- and inter observer reliability were respectively excellent and good for PT thickness. All eight (100%) ex vivo China ink injections were accurate, demonstrating a circumferential distribution of the injectate between the PT and the AT, associated with an anterior spread to the KFP. CONCLUSION: HRUS allows visualization of the PT along its entire length, and assessment of its relationships to adjacent structures. US-guided paratendinous injections can accurately and safely deliver injectates in the paratendinous sheath.

Radiological pulmonary sequelae after COVID-19 and correlation with clinical and functional pulmonary evaluation: results of a prospective cohort.

OBJECTIVES: Whether COVID-19 leads to long-term pulmonary sequelae or not remains unknown. The aim of this study was to assess the prevalence of persisting radiological pulmonary fibrotic lesions in patients hospitalized for COVID-19. MATERIALS AND METHODS: We conducted a prospective single-center study among patients hospitalized for COVID-19 between March and May 2020. Patients with residual symptoms or admitted into intensive care units were investigated 4 months after discharge by a chest CT (CCT) and pulmonary function tests (PFTs). The primary endpoint was the rate of persistent radiological fibrotic lesions after 4 months. Secondary endpoints included further CCT evaluation at 9 and 16 months, correlation of fibrotic lesions with clinical and PFT evaluation, and assessment of predictive factors. RESULTS: Among the 1151 patients hospitalized for COVID-19, 169 patients performed a CCT at 4 months. CCTs showed pulmonary fibrotic lesions in 19% of the patients (32/169). These lesions were persistent at 9 months and 16 months in 97% (29/30) and 95% of patients (18/19) respectively. There was no significant clinical difference based on dyspnea scale in patients with pulmonary fibrosis. However, PFT evaluation showed significantly decreased diffusing lung capacity for carbon monoxide (p < 0.001) and total lung capacity (p < 0.001) in patients with radiological lesions. In multivariate analysis, the predictive factors of radiological pulmonary fibrotic lesions were pulmonary embolism (OR = 9.0), high-flow oxygen (OR = 6.37), and mechanical ventilation (OR = 3.49). CONCLUSION: At 4 months, 19% of patients investigated after hospitalization for COVID-19 had radiological pulmonary fibrotic lesions; they persisted up to 16 months. CLINICAL RELEVANCE STATEMENT: Whether COVID-19 leads to long-term pulmonary sequelae or not remains unknown. The aim of this study was to assess the prevalence of persisting radiological pulmonary fibrotic lesions in patients hospitalized for COVID-19. The prevalence of persisting lesions after COVID-19 remains unclear. We assessed this prevalence and predictive factors leading to fibrotic lesions in a large cohort. The respiratory clinical impact of these lesions was also assessed. KEY POINTS: • Nineteen percent of patients hospitalized for COVID-19 had radiological fibrotic lesions at 4 months, remaining stable at 16 months. • COVID-19 fibrotic lesions did not match any infiltrative lung disease pattern. • COVID-19 fibrotic lesions were associated with pulmonary function test abnormalities but did not lead to clinical respiratory manifestation.

Infectious sacroiliitis: MRI- and CT-based assessment of disease extent, complications, and anatomic correlation.

OBJECTIVE: To describe the frequency of MR and CT features of infectious sacroiliitis (ISI) and assess its extent and complications MATERIALS AND METHODS: This retrospective study included patients with ISI who were evaluated between 2008 and 2021 in a single center. Two radiologists reviewed MRI and CT images to determine the anatomical distribution (unilateral/bilateral, iliac/sacral bone, proximal/middle/distal), severity (bone marrow edema [BME]/periostitis/erosions), concurrent infection (vertebral/nonvertebral), and complications (abscess/probable adjacent osteomyelitis/cavitation/devitalized areas/sequestrum/pelvic venous thrombosis) of ISI. Interobserver reproducibility was assessed. Correlation analysis evaluated the effect of the causative microorganism on severity. Two human bodies were dissected to outline possible ways that ISI can spread. RESULTS: Forty patients with ISI (40 years ± 22; 26 women) were evaluated. Ten patients had bilateral ISI. Concurrent vertebral infection was associated in 15% of cases. Reproducibility of sacral BME, periostitis, and reactive locoregional abnormalities was perfect (κ = 1). Reproducibility was low for erosion count (κ = 0.52[0.52-0.82]) and periarticular osteopenia (κ = 0.50[0.18-0.82]). Inflammatory changes were BME (42/42 joints), muscle edema (38/42), and severe periostitis along the ilium (33/37). Destructive structural changes occurred with confluent erosions (iliac, 20/48; sacral, 13/48), sequestrum (20/48), and cavitation (12/48). Complications occurred in 75% of cases, including periarticular abscesses (n = 30/47), probable adjacent osteomyelitis (n = 16/37), and pelvic thrombophlebitis (n = 3). Tuberculous ISI (6/40) correlated with sclerosis (rs = 0.45[0.16; 0.67]; p < 10-2) and bone devitalization (rs = 0.38[0.16; 0.67]; p = .02). The anatomical study highlighted the shared venous vascularization of sacroiliac joints, pelvic organs, and mobile spine. CONCLUSION: Complications of ISI are frequent, including abscesses, adjacent osteomyelitis, and periostitis. ISI had bilateral involvement nonrarely and is commonly associated with another spinal infection.

Evaluation of the Reproducibility of MR Elastography Measurements of the Lumbar Back Muscles.

BACKGROUND: MR elastography (MRE) may provide quantitative imaging biomarkers of lumbar back muscles (LBMs), complementing MRI in spinal diseases by assessing muscle mechanical properties. However, reproducibility analyses for MRE of LBM are lacking. PURPOSE: To assess technical failure, within-day and inter-day reproducibility, robustness with the excitation source positioning, and inter-observer agreement of MRE of muscles. STUDY TYPE: Prospective. SUBJECTS: Seventeen healthy subjects (mean age 28 ± 4 years; 11 females). FIELD STRENGTH/SEQUENCE: 1.5 T, gradient-echo MRE, T1-weighted turbo spin echo. ASSESSMENT: The pneumatic driver was centered at L3 level. Four MRE were performed during two visits, 2-4 weeks apart, each consisting of two MRE with less than 10 minutes inter-scan interval. At Visit 1, after the first MRE, the coil and driver were removed, then reinstalled. The MRE was repeated. At Visit 2, following the first MRE, only the driver was moved down 5 cm. The MRE was repeated. Two radiologists segmented the multifidus and erector spinae muscles. STATISTICAL TESTS: Paired t-test, analysis of variance, intraclass correlation coefficients (ICCs). P-values <0.05 were considered statistically significant. RESULTS: Mean stiffness of LBM ranged from 1.44 to 1.60 kPa. Mean technical failure rate was 2.5%. Inter-observer agreement was excellent (ICC ranging from 0.82 [0.64-0.96] to 0.99 [0.98-0.99] in the multifidus, and from 0.85 [0.69-0.92] to 0.99 [0.97-0.99] in the erector spinae muscles). Within-day reproducibility was fair in the multifidus (ICC: 0.53 [0.47-0.77]) and good in the erector spinae muscles (ICC: 0.74 [0.48-0.88]). Reproducibility after moving the driver was excellent in both multifidus (ICC: 0.85 [0.69-0.93]) and erector spinae muscles (ICC: 0.84 [0.67-0.92]). Inter-day reproducibility was excellent in the multifidus (ICC: 0.76 [0.48-0.89]) and poor in the erector spinae muscles (ICC: 0.23 [-0.61 to 0.63]). DATA CONCLUSION: MRE of LBM provides measurements of stiffness with fair to excellent reproducibility and excellent inter-observer agreement. However, inter-day reproducibility in the multifidus muscles indicated that the herein used MRE protocol may not be optimal for this muscle. EVIDENCE LEVEL: 2 TECHNICAL EFFICACY: Stage 1.

Understanding a mass in the paraspinal region: an anatomical approach.

The paraspinal region encompasses all tissues around the spine. The regional anatomy is complex and includes the paraspinal muscles, spinal nerves, sympathetic chains, Batson's venous plexus and a rich arterial network. A wide variety of pathologies can occur in the paraspinal region, originating either from paraspinal soft tissues or the vertebral column. The most common paraspinal benign neoplasms include lipomas, fibroblastic tumours and benign peripheral nerve sheath tumours. Tumour-like masses such as haematomas, extramedullary haematopoiesis or abscesses should be considered in patients with suggestive medical histories. Malignant neoplasms are less frequent than benign processes and include liposarcomas and undifferentiated sarcomas. Secondary and primary spinal tumours may present as midline expansile soft tissue masses invading the adjacent paraspinal region. Knowledge of the anatomy of the paraspinal region is of major importance since it allows understanding of the complex locoregional tumour spread that can occur via many adipose corridors, haematogenous pathways and direct contact. Paraspinal tumours can extend into other anatomical regions, such as the retroperitoneum, pleura, posterior mediastinum, intercostal space or extradural neural axis compartment. Imaging plays a crucial role in formulating a hypothesis regarding the aetiology of the mass and tumour staging, which informs preoperative planning. Understanding the complex relationship between the different elements and the imaging features of common paraspinal masses is fundamental to achieving a correct diagnosis and adequate patient management. This review gives an overview of the anatomy of the paraspinal region and describes imaging features of the main tumours and tumour-like lesions that occur in the region.

The interosseous tuberosities of the forearm exist from 1-year-old: a pediatric radiological study describing the ages of appearance of the different forearm reliefs.

PURPOSE: Interosseous tuberosities have been described in adults on the radial and ulnar sides. However, their presence at birth and their development during growth is still unknown. The objective of this work is to establish the age of onset of this tuberosity among a cohort of children aged 1-year-old or older. METHODS: All anterior-posterior and lateral radiographs performed in our hospital during a consecutive period of 6 months were retrospectively analyzed. Exclusion criteria were: presence of a fracture, a tumor, an age higher than 16 years, radiograph not performed strictly from the front with supination or from the side. On the anterior-posterior radiograph, the presence of the following structures was sought: radial interosseous tuberosity and determination of its length and width; the appearance of the epiphyseal nucleus of the radial head, of the bicipital tuberosity, and of the distal epiphysis. On the lateral views, the presence of the following structures was sought: ulnar interosseous tuberosity and determination of its length and width; the appearance of the olecranon epiphyseal nucleus, and the distal epiphysis. RESULTS: Over the review period, anterior-posterior and lateral radiographs were performed on 368 consecutive children. Finally, 179 patients were included in the radiographic analysis. The radial and ulnar interosseous tuberosities and bicipital tuberosity were present in all cases, from 1-year-old. Only the distal radial epiphysis began to appear at the age of one year, the others ossifying progressively during growth. CONCLUSION: Tuberositas interossea ulnarii and radii exists, are present from 1-year-old and continue to develop during growth.

COVID-19 and vaccination impact on radiology departments provided by Dose Archiving and Communication System.

OBJECTIVES: To study the impact of COVID-19 on chest CT practice during the different waves using Dose Archiving and Communication System (DACS). METHODS: Retrospective study including data from 86,136 chest CT acquisitions from 27 radiology centers (15 private; 12 public) between January 1, 2020, and October 13, 2021, using a centralized DACS. Daily chest CT activity and dosimetry information such as dose length product (DLP), computed tomography dose index (CTDI), and acquisition parameters were collected. Pandemic indicators (daily tests performed, incidence, and hospital admissions) and vaccination rates were collected from a governmental open-data platform. Descriptive statistics and correlation analysis were performed. RESULTS: For the first two waves, strong positive and significant correlations were found between all pandemic indicators and total chest CT activity, as high as R = 0.7984 between daily chest CT activity and hospital admissions during the second wave (p < 0.0001). We found differences between public hospitals and private imaging centers during the first wave, with private centers demonstrating a negative correlation between daily chest CT activity and hospital admissions (-0.2819, p = 0.0019). Throughout the third wave, simultaneously with the rise of vaccination rates, total chest CT activity decreased with significant negative correlations with pandemic indicators, such as R = -0.7939 between daily chest CTs and daily incidence (p < 0.0001). Finally, less than 5% of all analyzed chest CTs could be considered as low dose. CONCLUSIONS: During the first waves, COVID-19 had a strong impact on chest CT practice which was lost with the arrival of vaccination. Low-dose protocols remained marginal. KEY POINTS: • There was a significant correlation between the number of daily chest CTs and pandemic indicators throughout the first two waves. It was lost during the third wave due to vaccination arrival. • Differences were observed between public and private centers, especially during the first wave, less during the second, and were lost during the third. • During the first three waves of COVID-19 pandemic, few CT helical acquisitions could be considered as low dose with only 3.8% of the acquisitions according to CTDIvol and 4.3% according to DLP.

Vertebral trabecular bone texture analysis in opportunistic MRI and CT scan can distinguish patients with and without osteoporotic vertebral fracture: A preliminary study.

PURPOSE: To investigate the potential of texture parameters from opportunistic MRI and CT for the detection of patients with vertebral fragility fracture, to design a decision tree and to compute a Random Forest analysis for the prediction of fracture risk. METHODS: One hundred and eighty vertebrae of sixty patients with at least one (30) or without (30) a fragility fracture were retrospectively assessed. Patients had a DXA, an MRI and a CT scan from the three first lumbar vertebrae. Vertebrae texture analysis was performed in routine abdominal or lumbar CT and lumbar MRI using 1st and 2nd order texture parameters. Hounsfield Unit Bone density (HU BD) was also measured on CT-scan images. RESULTS: Twelve texture parameters, Z-score and HU BD were significantly different between the two groups whereas T score and BMD were not. The inter observer reproducibility was good to excellent. Decision tree showed that age and HU BD were the most relevant factors to predict the fracture risk with a 93 % sensitivity and 56 % specificity. AUC was 0.91 in MRI and 0.92 in CT-scan using the Random Forest analysis. The corresponding sensitivity and specificity were 72 % and 93 % in MRI and 83 and 89 % in CT. CONCLUSIONS: This study is the first to compare texture indices computed from opportunistic CT and MR images. Age and HU-BD together with selected texture parameters could be used to assess risk fracture. Machine learning algorithm can detect fracture risk in opportunistic CT and MR imaging and might be of high interest for the diagnosis of osteoporosis.

Texture Parameters Measured by UHF-MRI and CT Scan Provide Information on Bone Quality in Addition to BMD: A Biomechanical Ex Vivo Study.

The current definition of osteoporosis includes alteration of bone quality. The assessment of bone quality is improved by the development of new texture analysis softwares. Our objectives were to assess if proximal femoral trabecular bone texture measured in Ultra high field (UHF) 7 Tesla MRI and CT scan were related to biomechanical parameters, and if the combination of texture parameters and areal bone mineral density (aBMD) measured by dual-energy X-ray absorptiometry provided a better prediction of femoral failure than aBMD alone. The aBMD of 16 proximal femur ends from eight cadavers were investigated. Nineteen textural parameters were computed in three regions or volumes of interest for each specimen on UHF MRI and CT scan. Then, the corresponding failure load and failure stress were calculated thanks to mechanical compression test. aBMD was not correlated to failure load (R2 = 0.206) and stress (R2 = 0.153). The failure load was significantly correlated with ten parameters in the greater trochanter using UHF MRI, and with one parameter in the neck and the greater trochanter using CT scan. Eight parameters in the greater trochanter using UHF MRI combined with aBMD improved the failure load prediction, and seven parameters improved the failure stress prediction. Our results suggest that textural parameters provide additional information on the fracture risk of the proximal femur when aBMD is not contributive.

Intradiscal oxygen-ozone therapy for the treatment of symptomatic lumbar disc herniation: A preliminary study.

PURPOSE: To assess safety and effectiveness of computed tomography (CT)-guided intradiscal oxygen-ozone therapy (O2-O3 therapy) for the treatment of symptomatic lumbar disc herniation and radiological changes. MATERIALS AND METHODS: This study was conducted in twenty patients presenting lumbar disc herniation with resistant lumbar or lumbar radicular pain They underwent intradiscal oxygen-ozone therapy under CT guidance. They were treated at one- or two-disc levels, representing a total of 24 discs treated. MR imaging examinations were obtained before treatment and 2 months post-procedure to analyse treatment-related disc modifications including modification of the surfaces of the disc and of the herniated disc, and the variations in disc height according to the disc height index. Clinical outcomes were assessed using the visual analogue scale (VAS) to evaluate the severity of pain before the procedure, at primary (2 months) and at secondary (12 months) follow-ups. RESULTS: All the procedures were technically successful. The median VAS scores were 7.95 before the procedure, 3.9 at 2 months and 2.95 at 12 months. MRI analysis showed a significant decrease in herniation size at 2 months (-20%, p = 0.008). No immediate or late complications were observed. Only three patients (13.6%) underwent lumbar spine microdiscectomy in the year following ozone therapy. The treatment appeared to be more effective in cases of nerve root symptomatology. CONCLUSION: This study suggests that intradiscal O2-O3 therapy is safe and effective for the treatment of lumbar disc herniation associated with resistant lumbar or lumbar radicular pain.

The ulnar interosseous tuberosity exists: a radiological and descriptive cadaveric study.

PURPOSE: The anatomy of the ulna seems to have already been described exhaustively, particularly at its extremities, but very little in its middle third. We report the existence of an interosseous tuberosity on the interosseous border of the ulnar shaft that we have named the "tuberositas interossea ulnarii" (TIU). METHODS: First, we analyzed all side view X-rays of the forearm in neutral rotation, as well as forearm CT scans carried out during a 1-year period in our hospital. On these radiographic examinations, we evaluated the presence or absence of the TIU, its length, the thickness of the interosseous cortex at its level, above and below compared with anterior, posterior, and lateral bone cortices. In the second part of the study, we dissected cadaveric forearms to determine which ligaments and muscles were attached to it. RESULTS: A total of 91 standard forearm radiographs and 13 CT scans were analyzed. In all cases, the ulnar interosseous tuberosity was present. The mean tuberosity length was 107.5 mm (± 18.2), without any significant gender influence. It corresponded to a thickening (6.9 mm then 4.6 mm above and 3.9 mm below; p < 0.0001) of the ulnar interosseous cortex. Then, ten anatomic subjects (six females, four males) were dissected. We observed that this tuberosity served as an attachment for the central band of the interosseous membrane, for the deep flexor and extensor muscles for the long fingers, and for the abductor pollicis longus muscle's inner attachment. CONCLUSION: Tuberositas interossea ulnarii exists besides the tuberositas interossea radii, corresponds to thickening of the cortex and may play a role in the stability of the forearm and the function of the long fingers.

The interosseous tuberosity of radius: a descriptive radiological and cadaveric anatomical study.

PURPOSE: The radius is described with a single tuberosity: the radial tuberosity. However, we hypothesize that there is a second tuberosity on the interosseous border of the radius: which we propose to call the interosseous tuberosity - Tuberositas interossea radii - (IT). METHODS: First, we analyzed all anteroposterior radiographs of the forearm (48 females, 54 males; 62 lefts and 40 rights) as well as CT scans (6 females, 7 males; 5 lefts and 8 rights) carried out during one year in our hospital. We evaluated the presence of IT, its length, thickness of the interosseous cortex at IT level, above and below compared with anterior, posterior and lateral bone cortices. In the second part of the study, we dissected cadaveric forearms to determine which ligaments and muscles were attaches on the IT. RESULTS: A total of 102 standard forearm radiographs and 13 CT-scans were analyzed. In all cases, an IT was present. The mean tuberosity length was 93.9 mm (+ / - 15.8), which corresponds to 37% (+ / - 5) of total radial length. IT corresponds to a significant thickening (7.6 mm than 4.2 mm and 4.3 mm below; p < 0.0001) of radial interosseous cortex. A total of 10 forearms were dissected. In all cases, we observed that IT served as an attachment for central band of interosseous membrane and for all extrinsic muscles of the thumb with the exception of the extensor pollicis longus. CONCLUSION: Tuberositas interossea radii exists, corresponds to a cortex thickening and may play a role in the stability of the forearm and the function of the thumb.

The male external urethral sphincter is autonomically innervated.

INTRODUCTION: The aim of the present study was to describe autonomic urethral sphincter (US) innervation using specific muscular and neuronal antibody markers and 3D reconstruction. MATERIAL AND METHODS: We performed en-bloc removal of the entire pelvis of three male human fetuses between 18 and 40 weeks. Serial whole mount sections (5 µm intervals) were stained and investigated. The sections were stained with Masson's trichrome and Eosin Hematoxylin, and immunostained with: anti-SMA antibody for smooth muscle; anti-S100 antibody for all nerves; and anti-PMP22 antibody, anti-TH antibody, anti-CGRP antibody, anti-NOS antibody for somatic, adrenergic, sensory and nitrergic nerve fibers, respectively. The slides were digitized for 3D reconstruction to improve topographical understanding. An animated reconstruction of the autonomic innervation of the US was generated. RESULTS: The external and internal US are innervated by autonomic nerves of the inferior hypogastric plexus (IHP). These nerves are sympathetic (positive anti-TH antibody), sensory (positive anti-CGRP antibody), and nitrergic (positive anti-NOS antibody). Some autonomic fibers run within the neurovascular bundles, posterolaterally. Others run from the IHP to the posteromedial aspect of the prostate apex, above an through the rectourethral muscle. The external US is also innervated by somatic nerves (positive anti-PMP22 antibody) arising from the pudendal nerve, joining the midline but remaining below the rectourethral. CONCLUSIONS: This study provides anatomical evidence of an autonomic component in the innervation of the external US that travels in the neurovascular bundle. During radical prostatectomy, the rectourethral muscle and the neurovascular bundles are to be preserved, particularly during apical dissection.

Stabilization of the radial head with the palmaris longus or the gracilis tendon: an anatomical feasibility study.

PURPOSE: The proximal radioulnar joint (PRUJ) and the radiocapitellar joint may be destabilized after trauma. Different techniques for stabilization of PRUJ have been proposed, but none of them can stabilize the radiocapitellar joint at the same time. We propose a ligamentoplasty to stabilize the radial head at these two joints by reconstructing the radial head annular ligament and the lateral collateral ulnar ligament (LCUL) with a single graft (palmaris longus or gracilis tendon of the knee). METHODS: Fifteen cadaveric upper limbs were used to compare the stabilization obtained by performing our ligamentoplasty with the palmaris longus or the gracilis tendon. For each technique, the stabilization obtained was evaluated by measuring the displacement of the radial head in the anterior, lateral and posterior directions when a force of 1 N was applied in maximum supination, neutral rotation and maximum pronation. We also evaluated whether this technique could damage the ulnar nerve or the posterior interosseous nerve by dissecting them and whether it could limit the range of rotation of the forearm. RESULTS: Our ligamentoplasty enables to restore PRUJ stability equivalent to the intact ligament condition. The palmaris longus was inconstant (13/15) and too short to allow concomitant reconstruction of the LCUL (except in one case). No nerve damage was found during the dissection, and the range of rotation of the forearm was not limited by the ligamentoplasty. We also report a clinical case with an excellent result and without complications. CONCLUSION: This ligamentoplasty we have described makes it possible to stabilize the radial head with respect to the radial notch of the ulna and with respect to the capitellum of the humerus. The gracilis tendon is more suitable than the palmaris longus because of its constant presence and length. A clinical series is now necessary to better evaluate this technique.

IgG4-related disease: rare presentation as a soft-tissue mass in the thigh of an adolescent.

We report a case of a 16-year-old boy who presented a soft-tissue mass in the anterior compartment of the right thigh discovered by positron emission tomography/computed tomography within the work-up of unexplained prolonged inflammatory syndrome. The mass has no calcification. Subsequently, magnetic resonance imaging of the femoral triangle was carried out. Axial short tau inversion recovery images showed a 3.5-cm ill-defined mass in the femoral triangle with focal areas of hypointensity, which suggests that there might be fibrosis or hemosiderin within the tumor. Axial T1-weighted images showed a slight hyperintense mass involving the iliopsoas muscle. Contrast-enhanced fat-suppressed T1-weighted imaging showed a heterogeneous solid enhancement. Adjacent thick fascia enhancement of the vastus intermedius and the vastus lateralis muscles extending from the mass as a tail-like margin suggested the infiltrative spread of the tumor along the fascial plane. The mass and the lymphadenopathy were excised. Immunohistochemically, tumor cells were staining for muscle actin and desmin. Many plasma cells were IgG4+ (175per high-power field) with a ratio IgG4+/IgG+ of 50%. The diagnosis of IgG4-related disease (IgG4-RD) was made. Although a diffuse array of musculoskeletal symptoms has been observed in IgG4-related disease, reports of biopsy-proven musculoskeletal involvement of the limb are rare. We showed the radiological features of IgG4-RD presenting as a soft-tissue mass of the thigh. Musculoskeletal involvement, clinical significance, and treatment of IgG4-RD are also discussed.

The paraspinal muscle-tendon system: Its paradoxical anatomy.

Anatomy of the muscle-tendon system is an important component to musculoskeletal models. In particular, the cross-sectional area of belly (mCSA) and tendon (tCSA) provides information about the maximum force that a muscle may exert. The ratio of mCSA to tCSA (rCSA) demonstrates how muscle force is related to the ability to resist/transmit the force to bone. Previous anatomical studies of the lumbar paraspinal muscles (LPM) showed that their bellies have large mCSA suggesting that they are powerful muscles. Surprisingly, surgical experience shows that the tendons of the LPM are among the thinnest tendons of the body. We therefore hypothesized that traditional biomechanics of the LPM and the rCSA do not correspond for LPM. In 10 fresh-frozen old cadavers, we measured the mCSA, tCSA and rCSA of the LPM (multifidus and the erector spinae, i.e. the longissimus and the iliocostalis); then, we compared these data with those of one of the weakest muscles in the body, i.e. the extensor digitorum communis (EDC) chosen because it shares some common anatomical features with the LPM, in particular with the erector spinae. For instance, the EDC has a polyarticular course and presents long and thin effector tendons. Among the LPM, the longissimus has the greatest mean ACSA with 10.42 cm2 compared with 9.16 cm2 for the iliocostalis and 0.24 cm2 for the multifidus. Mean ACSA of the EDC was almost ten times smaller than those of erector spinae. Regarding the mean tCSA, the EDC was the largest one with 11.48 mm2 compared with 2.69 mm2 and 1.43 mm2 for the longissimus, 5.74 mm2 and 2.38 mm2for the iliocostalis and 5.28 mm2 and 4.96 mm2 for the multifidus. Mean rCSAs of the erector spinae were extremely small, ranged from 1/156 for the spinal attachment of the iliocostalis to 1/739 for the rib attachment of the longissimus that suggests that tendons are an unsuitable size to transmit the force to bone. Mean rCSA of the multifidus and the EDC were in the same range with rCSA = 1/5 and rCSA = 1/9 respectively. The rCSA of the multifidus was substantial, but its ACSA (1cm2) corresponds to low-power muscles. This paradoxical anatomy compels us to consider the biomechanics of the LPM in a different way from that of the classical "chord-like model", i.e. the muscle belly creates a force that is applied to a bone piece through a tendon. The LPM have large contractile mass in a semi-rigid compartment inside which the pressure may increase. This result strengthens the hypothesis that high pressure and intrinsic stiffness of the LPM create two stiff bodies, closely attached to the spine thus ensuring its stabilization.

Posture-related stiffness mapping of paraspinal muscles.

The paraspinal compartment acts as a bone-muscle composite beam of the spine. The elastic properties of the paraspinal muscles play a critical role in spine stabilization. These properties depend on the subjects' posture, and they may be drastically altered by low back pain. Supersonic shear wave elastography can be used to provide quantitative stiffness maps (elastograms), which characterize the elastic properties of the probed tissue. The aim of this study was to challenge shear wave elastography sensitivity to postural stiffness changes in healthy paraspinal muscles. The stiffness of the main paraspinal muscles (longissimus, iliocostalis, multifidus) was measured by shear wave elastography at the lumbosacral level (L3 and S1) for six static postures performed by volunteers. Passive postures (rest, passive flexion, passive extension) were performed in a first shear wave elastography session, and active postures (upright, bending forward, bending backward) with rest posture for reference were performed in a second session. Measurements were repeated three times for each posture. Sixteen healthy young adults were enrolled in the study. Non-parametric paired tests, multiple analyses of covariance, and intra-class correlations were implemented for analysis. Shear wave elastography showed good to excellent reliability, except in the multifidus at S1, during bending forward, and in the multifidus at L3, during bending backward. Yet, during bending forward, only poor quality was recorded for nine volunteers in the longissimus. Significant intra- and inter-muscular changes were observed with posture. Stiffness significantly increased for the upright position and bending forward with respect to the reference values recorded in passive postures. In conclusion, shear wave elastography allows reliable assessment of the stiffness of the paraspinal muscles except in the multifidus at S1 and longissimus, during bending forward, and in the multifidus at L3, during bending backward. It reveals a different biomechanical behaviour for the multifidus, the longissimus, and the iliocostalis.

Characterization of Testicular Masses in Adults: Performance of Combined Quantitative Shear Wave Elastography and Conventional Ultrasound.

We prospectively evaluated the performance of combined shear wave elastography (SWE) and conventional ultrasound (US) for the characterization of 89 testicular focal masses. Testes were evaluated with B-mode, color Doppler and SWE measurements, locating a region of interest on the normal and pathologic parenchyma. Thirty-seven malignant tumors (MTs), 12 burned out tumors (BOTs), 28 Leydig cell tumors (LCTs), 2 dermoid cysts and other benign lesions were included. MTs + BOTs exhibited more microliths and macrocalcifications compared with benign lesions (p < 10-4). LCTs manifested mostly a dominant peripheral vascularization pattern compared with other lesions. MTs + BOTs were stiffer compared with benign lesions (p < 2 × 10-4) but with a moderate area under the receiver operating characteristic curve (AUROC) of 80%. By focusing on LCTs versus MTs + BOTs, diagnostic performance led to an AUROC of 89% for the best stiffness parameter. For combined conventional US and SWE, the diagnostic performance to differentiate all benign lesions versus MTs + BOTs and LCTs versus MTs + BOTs increased to AUROCs of 93% and 98%, respectively.