A novel deep learning method for large-scale analysis of bone marrow adiposity using UK Biobank Dixon MRI data.

Background: Bone marrow adipose tissue (BMAT) represents > 10% fat mass in healthy humans and can be measured by magnetic resonance imaging (MRI) as the bone marrow fat fraction (BMFF). Human MRI studies have identified several diseases associated with BMFF but have been relatively small scale. Population-scale studies therefore have huge potential to reveal BMAT's true clinical relevance. The UK Biobank (UKBB) is undertaking MRI of 100,000 participants, providing the ideal opportunity for such advances. Objective: To establish deep learning for high-throughput multi-site BMFF analysis from UKBB MRI data. Materials and methods: We studied males and females aged 60-69. Bone marrow (BM) segmentation was automated using a new lightweight attention-based 3D U-Net convolutional neural network that improved segmentation of small structures from large volumetric data. Using manual segmentations from 61-64 subjects, the models were trained to segment four BM regions of interest: the spine (thoracic and lumbar vertebrae), femoral head, total hip and femoral diaphysis. Models were tested using a further 10-12 datasets per region and validated using datasets from 729 UKBB participants. BMFF was then quantified and pathophysiological characteristics assessed, including site- and sex-dependent differences and the relationships with age, BMI, bone mineral density, peripheral adiposity, and osteoporosis. Results: Model accuracy matched or exceeded that for conventional U-Nets, yielding Dice scores of 91.2% (spine), 94.5% (femoral head), 91.2% (total hip) and 86.6% (femoral diaphysis). One case of severe scoliosis prevented segmentation of the spine, while one case of Non-Hodgkin Lymphoma prevented segmentation of the spine, femoral head and total hip because of T2 signal depletion; however, successful segmentation was not disrupted by any other pathophysiological variables. The resulting BMFF measurements confirmed expected relationships between BMFF and age, sex and bone density, and identified new site- and sex-specific characteristics. Conclusions: We have established a new deep learning method for accurate segmentation of small structures from large volumetric data, allowing high-throughput multi-site BMFF measurement in the UKBB. Our findings reveal new pathophysiological insights, highlighting the potential of BMFF as a novel clinical biomarker. Applying our method across the full UKBB cohort will help to reveal the impact of BMAT on human health and disease.

Crystal Diseases of the Spine.

Gout, calcium pyrophosphate deposition disease, and apatite calcifications, the three main crystal disorders, may involve the spine. These disorders can be completely asymptomatic or associated with various clinical symptoms, such as acute flares and more chronic manifestations. This article presents the typical and more unusual imaging features encountered in these disorders.

Relationship between bone marrow adipose tissue and kidney function in postmenopausal women.

Introduction: Bone marrow adipose tissue (BMAT) is associated with aging, osteoporosis, and chronic kidney disease (CKD). To date, the association between BMAT and kidney function in postmenopausal women has not been thoroughly investigated. The main purpose of this study was to determine whether a relationship exists between proton density fat fraction (PDFF) and kidney function in postmenopausal women. Methods: We investigated the cross-sectional association between estimated glomerular filtration rate (eGFR) - calculated using the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation - and PDFF - measured at the lumbar spine and proximal femur using Water Fat Imaging (WFI) MRI - in 199 postmenopausal women from the ADIMOS cohort study. We also performed DXA scans and laboratory measurements of sclerostin and c-terminal Fibroblast Growth Factor 23 (cFGF23). Results: Participants' mean age was 67.5 (standard deviation, SD 10.0) years. Their median eGFR was 85.0 (interquartile range, IQR 72.2-95.0) ml/min/1.73 cm2, and their mean lumbar spine PDFF was 57.9 % (SD 9.6). When classified by eGFR-based CKD stages, 41.7 % of the cohort had an eGFR ≥ 90 (n = 83), 47.2 % had an eGFR of 60-89.9 (n = 94), and 11.1 % had an eGFR of 30-59.9 (n = 22). Participants with eGFR ≥ 90 had a lower lumbar spine PDFF than those with eGFR 60-89.9 (mean 55.8 % (9.8) vs. 58.9 % (9.0), p = 0.031) and those with eGFR 30-59.9 (55.8 % (9.8) vs. 60.8 % (9.8), p = 0.043). However, the differences did not remain significant after adjusting for predetermined confounders, including age, diabetes, Charlson comorbidity index, recent history of fragility fracture, appendicular lean mass, and lumbar spine BMD. The inclusion of sclerostin and/or cFGF23 as suspected mediators did not alter the findings. When proximal hip imaging-based PDFF was considered, no significant differences were found between the eGFR categories in the unadjusted and adjusted analyses. Conclusion: No evidence of an association between kidney function and bone marrow adiposity was found either in the lumbar spine or proximal femur in a cohort of postmenopausal women.

Medial meniscal repair in stable knees: Survival rate and risk factors for failure at a minimum of 5 years.

INTRODUCTION: The menisci play a major role in the protection of the knee against osteoarthritis. A medial meniscus (MM) tear occurring in a stable knee is more at risk of repair failure than a suture concomitant with reconstruction of the anterior cruciate ligament. HYPOTHESIS: The survival of MM sutures in stable knees depends on the type of lesion. MATERIALS AND METHODS: This retrospective study was carried out as part of the 2022 Francophone Arthroscopy Society's symposium, across 10 centers (Bordeaux-Mérignac, Caen, Lille, Lille Louvière, Lyon, Marseille, Toulouse, Saint-Étienne, Strasbourg and Versailles) including medial meniscus sutures in stable knees performed before the end of 2017 (minimum 5 years of follow-up) with a collection of demographic, imaging, suture and postoperative protocol data, and a functional evaluation using the Knee injury and Osteoarthritis Outcome score (KOOS). The aim of this study was to analyze the medial meniscus sutures in stable knees and to evaluate their survival and their risk factors for failure according to the type of lesion; failure being defined by the use of a meniscectomy. RESULTS: Three-hundred and sixty-seven MM sutures, including 122 bucket-handle tears, were included. The KOOS score was improved by the meniscal suture by an average of 22.2 points for each sub-score (p<0.05), with an improvement, which was more marked for the bucket-handle tears. The failure rate, defined by revision surgery by meniscectomy, was 33% on average (42% for bucket-handles tears, 26% for others). The probability of survival was reduced for bucket-handle tears (62% at 5 years versus 77% for the other types). For all lesions, the main risk factor identified for failure was immediate weight-bearing [OR=3.6 (1.62; 7.98), p=0.0016]. Smoking was a failure risk factor for bucket-handle tears [OR=5.76 (1.81; 18.35), p=0.003]. CONCLUSION: MM sutures in stable knees improve knee function but present a different risk of failure depending on the type of lesion treated with a higher risk of failure for bucket-handle tears with the need for caution to be applied with regards to weight-bearing and smoking. LEVEL OF EVIDENCE: IV; retrospective series.

The frequency of medial meniscal repairs in stable knees during one year of arthroscopic activity (2021-2022) - comparison with a retrospective study (prior to 2017).

INTRODUCTION: There has been a significant increase in the use of conservative treatment for meniscal lesions due to raised awareness around the need for meniscal preservation. However, sutures of the medial meniscus (MM) in stable knees remain less frequently used. The objective of this study was to, firstly, identify the MM suture rate over one year of activity; secondly, to identify and compare the distribution of MM sutures in stable, and stabilized, knees on this prospective series; and thirdly, to compare the evolution of practices with a retrospective series of more than 5 years follow-up. HYPOTHESIS: The number of MM sutures in stable knees represents a small percentage of annual arthroscopic activity. MATERIAL AND METHODS: This multicenter study was carried out in 10 reference centers participating in the 2022 symposium of the Francophone Society of Arthroscopy (Bordeaux, Caen, Lille, Lille Louvière, Lyon, Marseille, Toulouse, Saint-Étienne, Strasbourg, Versailles). This study included a prospective series on interventions performed under arthroscopy during one year of activity. The inclusion criteria were patients operated on via an arthroscopic technique and aged over 18 at the time of the operation. Demographic data, as well as the circumstances leading to the injury, were collected. A register of the lesions found was established in order to list the lesions of the MM, the lateral meniscus (LM), the anterior cruciate ligament (ACL), the associated chondral lesions; as well as the treatment performed: meniscal suture of the MM and/or LM, meniscectomy of the MM and/or LM and ligamentoplasty of the ACL. This study also included a retrospective series comprised of only MM sutures in stable knees at more than 5 years of follow-up. RESULTS: Of the 4154 patients included, 1919 patients (46.2%) underwent surgery for ACL reconstruction and 2235 for arthroscopy without associated ligament surgery. MM sutures (in stable knees and in knees with ACL reconstruction) represented 14% of the overall arthroscopic activity (583 MM sutures) versus 8.6% for LM (360 sutures). In cases of ACL surgery, there were 895 associated meniscal lesions (337 LM and 558 MM) and 66% of MM tears (371 MM sutures) were sutured. In stable knees, MM tears were weaker (212 MM sutures out of 1359 lesions, i.e. 15%). Of all the arthroscopic procedures performed over the course of a year, MM suturing in stable knees represented 5.1% of the activity. Compared to the retrospective series (n=367), the patients were older (37 years versus 28 years) and the management of ramp lesions or root tears was noted. In both series, these tears were related to sports trauma in more than 70% of cases. CONCLUSION: MM suturing in stable knees represents a small part of annual arthroscopic activity and it occurs less frequently than during ACL reconstruction surgery. LEVEL OF EVIDENCE: IV.

Myosteatosis and bone marrow adiposity are not associated among postmenopausal women with fragility fractures.

Objectives: Although paravertebral intramuscular fatty infiltration (known as myosteatosis) following a vertebral fracture is well-known, scarce data are available regarding interactions between muscle, bone, and other fat depots. Based on a homogeneous cohort comprising postmenopausal women with or without a history of fragility fracture, we aimed to better depict the interrelationship between myosteatosis and bone marrow adiposity (BMA). Methods: 102 postmenopausal women were included, 56 of whom had a fragility fracture. Mean proton density fat fraction (PDFF) was measured in the psoas (PDFFPsoas) and paravertebral (PDFFParavertebral) muscles at the lumbar level, as well as in the lumbar spine and non-dominant hip using chemical shift encoding-based water-fat imaging. Visceral adipose tissue (VAT) and total body fat (TBF) were assessed using dual X-ray absorptiometry. Statistical models were adjusted for age, weight, height (all comparisons), and bone mineral density (when considering BMA). Results: PDFF in the psoas and paravertebral muscles was higher in the fracture group compared to controls even after adjustment for age, weight, and height (PDFFPsoas = 17.1 ± 6.1% versus 13.5 ± 4.9%, p=0.004; PDFFParavertebral = 34.4 ± 13.6% versus 24.9 ± 8.8%, p=0.002). Higher PDFFParavertebral was associated with lower PDFF at the lumbar spine (ß = -6.80 ± 2.85, p=0.022) among controls but not in the fracture group. In both groups, a significant relationship between higher PDFFPsoas and higher VAT was observed (ß = 20.27 ± 9.62, p=0.040 in the fracture group, and ß = 37.49 ± 8.65, p<0.001 in the control group). Although solely observed among controls, a similar relationship was observed between PDFFParavertebral and TBF (ß = 6.57 ± 1.80, p<0.001). No significant association was observed between BMA and other fat depots. Conclusion: Myosteatosis is not associated with BMA among postmenopausal women with fragility fractures. Whereas myosteatosis was associated with other fat depots, BMA appears uniquely regulated.

Rehabilitation protocol after suturing the medial meniscus of a stable knee, a retrospective series of the Francophone Arthroscopy Society.

INTRODUCTION: Surgical meniscal lesions are common and 80% of cases involve the medial meniscus of a stable knee. There is a lack of consensus regarding postoperative rehabilitation protocols and a wide variation between restrictive and accelerated rehabilitation protocols exists. The main objective of this study was to report the functional results and the failure rate of the various rehabilitation protocols of the retrospective series of the French Society of Arthroscopy (SFA) after suturing the medial meniscus of a stable knee, considering whether the tear is stable or unstable. HYPOTHESIS: Our hypothesis was that accelerated rehabilitation was not associated with an increased risk of failure. MATERIALS AND METHODS: This retrospective, multicenter study was conducted across 10 centers (6 private hospitals and 4 public hospitals) including all patients tested for a medial meniscus suture in a stable knee between January 1, 2005 and November 31, 2017 for a minimum follow-up of 5years. Demographic, imaging, suturing, rehabilitation protocol, and functional TEGNER and KOOS scores were collected. Failure was defined as performing a secondary meniscectomy. RESULTS: Three hundred and sixty-seven patients were analyzed with an average follow-up of 82months. Immediate weight bearing was allowed in 85% of cases, the wearing of a brace was present in almost 74% of cases and flexion was limited in 97% of cases. Inter-group comparisons found a higher suture failure rate in the group with immediate weight bearing (35.6% vs. 20%, p=0.011) and in the group with a brace (36.9% vs. 22.4%, p<0.001). There was no difference in the 90° flexion group. The TEGNER score was higher in the non-weight bearing group (6.5 vs. 5.4, p=0.028) and the KOOS QOL score was higher in the group without a brace (82.2 vs. 66.8, p=0.025). According to a multivariate analysis, immediate weight bearing (OR=3.6, [1.62; 7.98], p=0.0016) and wearing a brace (OR=2.83, [1.54; 5.02], p<0.001) were associated with a higher failure rate. In the group of stable lesions, the use of a brace (OR=3.73, [1.62; 8.56], p=0.0019) was associated with a higher failure rate. CONCLUSION: No consensus regarding rehabilitation protocols has been established to date and the results of this retrospective series of the SFA affirm the great variability of practices at a national level. Although accelerated rehabilitation protocols are presently favored, the resumption of immediate full weight bearing should be considered with caution, being associated with a higher risk of failure in this series. Deferring weight bearing for 1 month can be considered in the event of a large tear or in the event of damage to the circumferential fibers. Wearing a brace does not seem to have any influence, while limited flexion achieved a consensus. LEVEL OF EVIDENCE: IV, retrospective study.

Bone Marrow Adiposity and Fragility Fractures in Postmenopausal Women: The ADIMOS Case-Control Study.

CONTEXT: Noninvasive assessment of proton density fat fraction (PDFF) by magnetic resonance imaging (MRI) may improve the prediction of fractures. OBJECTIVE: This work aimed to determine if an association exists between PDFF and fractures. METHODS: A case-control study was conducted at Lille University Hospital, Lille, France, with 2 groups of postmenopausal women: one with recent osteoporotic fractures, and the other with no fractures. Lumbar spine and proximal femur (femoral head, neck, and diaphysis) PDFF were determined using chemical shift-based water-fat separation MRI (WFI) and dual-energy x-ray absorptiometry scans of the lumbar spine and hip. Our primary objective was to determine the relationship between lumbar spine PDFF and osteoporotic fractures in postmenopausal women. Analysis of covariance was used to compare PDFF measurements between patient cases (overall and according to the type of fracture) and controls, after adjusting for age, Charlson comorbidity index (CCI) and BMD. RESULTS: In 199 participants, controls (n = 99) were significantly younger (P < .001) and had significantly higher BMD (P < 0.001 for all sites) than patient cases (n = 100). A total of 52 women with clinical vertebral fractures and 48 with nonvertebral fractures were included. When PDFFs in patient cases and controls were compared, after adjustment on age, CCI, and BMD, no statistically significant differences between the groups were found at the lumbar spine or proximal femur. When PDFFs in participants with clinical vertebral fractures (n = 52) and controls were compared, femoral neck PDFF and femoral diaphysis PDFF were detected to be lower in participants with clinical vertebral fractures than in controls (adjusted mean [SE] 79.3% [1.2] vs 83.0% [0.8]; P = 0.020, and 77.7% [1.4] vs 81.6% [0.9]; P = 0.029, respectively). CONCLUSION: No difference in lumbar spine PDFF was found between those with osteoporotic fractures and controls. However, imaging-based proximal femur PDFF may discriminate between postmenopausal women with and without clinical vertebral fractures, independently of age, CCI, and BMD.

Anatomical Variants of the Sacroiliac Joint.

Anatomical variants are frequently encountered when assessing the sacroiliac joints (SIJ) using magnetic resonance imaging. When not located in the weight-bearing part of the SIJ, variants associated with structural and edematous changes can be misinterpreted as sacroiliitis. Their correct identification is necessary to avoid radiologic pitfalls. This article reviews five SIJ variants involved in the dorsal ligamentous space (accessory SIJ, iliosacral complex, semicircular defect, bipartite iliac bony plate, and crescent iliac bony plate) and three SIJ variants involved in the cartilaginous part of the SIJ (posterior dysmorphic SIJ, isolated synostosis, and unfused ossification centers).

Relationships between Circulating Sclerostin, Bone Marrow Adiposity, Other Adipose Deposits and Lean Mass in Post-Menopausal Women.

Sclerostin is a Wnt signaling pathway inhibitor that negatively regulates bone formation. Bone-marrow-derived stromal cell (BMSC) differentiation is influenced by the Wnt pathway, leading to the hypothesis that higher levels of sclerostin might be associated with an increase in bone marrow adiposity (BMA). The main purpose of this study was to determine whether a relationship exists between circulating sclerostin and BMA in post-menopausal women with and without fragility fractures. The relationships between circulating sclerostin and body composition parameters were then examined. The outcomes measures included vertebral and hip proton density fat fraction (PDFF) using the water fat imaging (WFI) MRI method; DXA scans; and laboratory measurements, including serum sclerostin. In 199 participants, no significant correlations were found between serum sclerostin and PDFF. In both groups, serum sclerostin was correlated positively with bone mineral density (R = 0.27 to 0.56) and negatively with renal function (R = -0.22 to -0.29). Serum sclerostin correlated negatively with visceral adiposity in both groups (R = -0.24 to -0.32). Serum sclerostin correlated negatively with total body fat (R = -0.47) and appendicular lean mass (R = -0.26) in the fracture group, but not in the controls. No evidence of a relationship between serum sclerostin and BMA was found. However, serum sclerostin was negatively correlated with body composition components, such as visceral adiposity, total body fat and appendicular lean mass.

Quantitative dynamic contrast-enhanced MRI of bone marrow perfusion at the proximal femur: influence of femoral head osteonecrosis risk factor and overt osteonecrosis.

OBJECTIVE: To evaluate the MRI perfusion changes in patients with risk factors for osteonecrosis and normally appearing femoral heads prior to overt femoral head osteonecrosis. METHODS: Fifty-eight patients (105 hips) were prospectively included in this ethics committee-approved study. There were 46 hips with no image anomalies and no risk factors for osteonecrosis of the femoral head (ONFH) risk factors, 38 with ONFH risk factors and no image abnormalities, and 21 with overt ONFH. All patients underwent DCE-MRI. Semi-quantitative (peak enhancement [PE], area under the curve [AUC], time to maximum enhancement [TME]) and quantitative perfusion parameters (volume plasma, KTRANS, and KEP) were calculated. Excessive alcohol consumption, corticosteroid use, and trauma were considered major risk factors for osteonecrosis of the femoral head. RESULTS: Measured at the femoral neck and compared to the healthy hips without OFNH risk factors, PE was significantly lower in the hips of patients with OFNH risk factors. Moreover, the difference was greater in females with risk factors, who presented significantly lower PE values (p = 0.0096). A PE threshold of 1.4% yielded a 92% sensitivity and 54% specificity for the presence of associated ONFH risk factors. The hips with overt OFNH compared to those with normally appearing showed an increase of PE of 45% in the neck (p < 0.014). Various epiphyseal femoral head perfusion parameters (PE, TME, AUC, and Ktrans) presented statistically significant differences in hips with ONFH and those without (p < 0.0001). CONCLUSION: DCE-MRI can identify perfusion marrow changes related to the presence of ONFH risk factors and adjacent to osteonecrosis areas. KEY POINTS: • Bone marrow perfusion changes may occur prior to overt ONFH and extend beyond the osteonecrosis area to the entire femoral head and neck. • Peak enhancement values were significantly reduced in patients with ONFH risk factors, compared to those without. • The presence of ONFH led to a significant increase in marrow perfusion adjacent to the osteonecrosis area.

Stimulatory Effect of Tofacitinib on Bone Marrow Adipocytes Differentiation.

Background: Systemic inflammation is the main factor underlying secondary osteoporosis in patients with rheumatoid arthritis (RA). Janus kinase inhibitors (JAKi), such as tofacitinib (Tofa), can control systemic inflammation and may have beneficial effects on bone in various models. This might be due to direct effects on the bone microenvironment and not exclusively based on their anti-inflammatory function. Bone marrow adipocytes (BMAds) are abundant in the bone microenvironment. The effect of JAKi on BMAds is unknown, but evidence suggests that there is competition between human bone marrow-derived stromal cell (hBMSC) differentiation routes towards BMAds and osteoblasts (Ob) in osteoporosis. Objectives: The aims of the study are to determine whether Tofa influences BMAds and Ob derived from hBMSCs and to investigate the potential effects of Tofa on bone marrow adiposity in RA patients. Methods: To determine the effect of Tofa on cellular commitment, hBMSCs were differentiated to BMAds or OBs for 3 days together with Tofa at 200, 400, or 800 nM and TNFα. This study was also conducted using differentiated BMAds. The impact of Tofa was determined by gene and protein expression analysis and cell density monitoring. In parallel, in a pilot study of 9 RA patients treated with Tofa 5 mg twice a day (NCT04175886), the proton density fat fraction (PDFF) was measured using MRI at the lumbar spine at baseline and at 6 months. Results: In non-inflammatory conditions, the gene expression of Runx2 and Dlx5 decreased in Ob treated with Tofa (p <0.05). The gene expression of PPARγ2, C/EBPα, and Perilipin 1 were increased compared to controls (p <0.05) in BMAds treated with Tofa. Under inflammatory conditions, Tofa did not change the expression profiles of Ob compared to TNFα controls. In contrast, Tofa limited the negative effect of TNFα on BMAd differentiation (p <0.05). An increase in the density of differentiated BMAds treated with Tofa under TNFα was noted (p <0.001). These findings were consolidated by an increase in PDFF at 6 months of treatment with Tofa in RA patients (46.3 ± 7.0% versus 53.2 ± 9.2% p <0.01). Conclusion: Together, these results suggest a stimulatory effect of Tofa on BMAd commitment and differentiation, which does not support a positive effect of Tofa on bone.

Presurgical Perspective and Postsurgical Evaluation of Non-Achilles Tendons of the Ankle and Retinaculum.

The vast majority of non-Achilles ankle tendinopathies are related to overuse. This article discusses the clinical aspect, imaging appearance, and management of tendinopathies of the lateral, medial, and the anterior compartments with a focus on presurgical perspective and postsurgical evaluation.

Main Diagnostic Pitfalls in Reading the Sacroiliac Joints on MRI.

Magnetic resonance imaging of the sacroiliac joints is now frequently performed to help identify patients with early axial spondyloarthritis. However, differential diagnoses exist and should be recognized. The aim of this article is to review the most frequent differential diagnoses that may mimic inflammatory sacroiliitis in clinical practice.

Impact of introducing extremity cone-beam CT in an emergency radiology department: A population-based study.

BACKGROUND: Musculoskeletal cone-beam CT (CBCT) recently appeared on the market, with image quality comparable to that of high-resolution CT. It was previously implemented mainly in craniofacial surgery and in orthopedic limb surgery for weight-bearing imaging, but without large-scale assessment in emergency settings. We therefore conducted a retrospective comparative study in an emergency radiology department: 1) to assess whether introduction of CBCT dedicated to extremity traumatology reduced radiation dose delivered to the patient undergoing cross-sectional imaging, 2) to assess whether it increased turnover, and 3) to study the feasibility and practical consequences. Study hypothesis Introducing CBCT dedicated to traumatology in an emergency radiology department reduces radiation dose related to cross-sectional imaging in extremity trauma. PATIENTS AND METHODS: Two periods were distinguished: in May-November 2016, the only cross-sectional imaging available in our emergency radiology department was multi-detector CT (MDCT); in May-November 2017, both MDCT and CBCT were available. Thus, the population in period 1 (n=165) had undergone only MDCT extremity imaging, while patients in period 2 underwent either CBCT (n=139) or MDCT (n=85). Study parameters notably included dose-length product (DLP) and length of patient stay in the radiology department (turnover). RESULTS: Mean DLP was significantly reduced with the introduction of CBCT: 210.3±133.6 mGy.cm (range, 20-595) in period 1, versus 138.4±92.7 mGy.cm (range, 32-623) in period 2 (p<0.0001). Taking both periods together, mean DLP was 50.7% lower with CBCT (n=139) than MDCT (n=249): respectively, 101.6±14.9 mGy.cm (range, 50.6-126.9) versus 206.5±131.8 mGy.cm (range, 20-623) (p<0.0001). Turnover accelerated with the introduction of CBCT, with mean stay of 84.9minutes in period 1 versus 72.1minutes in period 2 (p=0.011). In period 2, turnover was 23.6% faster with CBCT than MDCT: respectively, 64.9minutes versus 85.0minutes (p=0.0004). DISCUSSION: Introducing CBCT dedicated to the extremities in an emergency radiology department was feasible. It reduced overall radiation dose and accelerated turnover. LEVEL OF EVIDENCE: III; comparative case-control study.

Anatomical study of the proximal tibiofibular ligaments using ultrasound.

OBJECTIVES: No description of the proximal tibiofibular (PTF) ligaments by means of high ultrasound has yet been reported in the literature. The purpose of this study was to assess whether ultrasound may allow the assessment of these ligaments. METHODS: This study was initially undertaken in three cadaveric knees, followed by an ultrasound study performed by two musculoskeletal radiologists working in consensus of 52 patients without history of trauma or surgery of the knee, and without lateral knee pain. The visibility, echogenicity, length and thickness of the PTF ligaments were assessed. RESULTS: Regarding the anterior PTF ligament, the superior bundle and the upper and lower middle bundles were clearly seen in 42.3%, 100% and 75% of the knees, respectively. Regarding the posterior PTF ligament, the superior and middle bundles were clearly seen in 88.4% and 51.9% of the knees, respectively. The echo-anatomy of these ligaments and the probe positioning allowing their best depiction were described in this study. CONCLUSION: Most of the PTF ligaments can be visualized by means of ultrasound. This possible assessment may have clinical applications, particularly in patients with lateral knee pain.

Enlarged External Occipital Protuberance in young French individuals' head CT: stability in prevalence, size and type between 2011 and 2019.

External Occipital Protuberance (EOP) enlargement has been recently reported to increase in young adults, with a putative link with postural factors such as the use of smartphones. This study aims to analyze finely the changes in prevalence and size of EOP enlargement in millennials, throughout the smartphone era (2011 - 2019). Anonymized head Computerized Tomography (CT) examinations from patients aged 18-30 in 2011 (n = 205) or 2019 (n = 240), were reviewed to assess the type of EOP and to measure its volume in case of enlargement. Additional CT analyses were performed on two ancient skulls, from a XVIth century young male and a young female Egyptian mummy. There was no significant evolution in the prevalence of EOP enlargement between 2011 (92/205, 44.9%) and 2019 (106/240; 44.2%) (P = 0.92). There was no significant evolution either in the distribution of enlarged EOP volumes (P = 0.14) or of EOP types (P = 0.92) between 2011 and 2019. In the meantime, rates of smartphone ownership in millennials rose from 35% to 98%. Compared to 2019 volumes, the Egyptian mummy displayed an EOP enlargement corresponding to the 85th percentile for young women, and the XVIth century skull to the 73rd percentile for young men. In conclusion, on a population scale, prevalence and volume of enlarged EOP in millennials remain stable between 2011 and 2019, which makes the impact of rapidly growing modern environmental factors on EOP changes unlikely. EOP enlargement was also already present in ancient skulls from young individuals, with measurements within today's upper ranges.

Reporting Guidelines, Review of Methodological Standards, and Challenges Toward Harmonization in Bone Marrow Adiposity Research. Report of the Methodologies Working Group of the International Bone Marrow Adiposity Society.

The interest in bone marrow adiposity (BMA) has increased over the last decade due to its association with, and potential role, in a range of diseases (osteoporosis, diabetes, anorexia, cancer) as well as treatments (corticosteroid, radiation, chemotherapy, thiazolidinediones). However, to advance the field of BMA research, standardization of methods is desirable to increase comparability of study outcomes and foster collaboration. Therefore, at the 2017 annual BMA meeting, the International Bone Marrow Adiposity Society (BMAS) founded a working group to evaluate methodologies in BMA research. All BMAS members could volunteer to participate. The working group members, who are all active preclinical or clinical BMA researchers, searched the literature for articles investigating BMA and discussed the results during personal and telephone conferences. According to the consensus opinion, both based on the review of the literature and on expert opinion, we describe existing methodologies and discuss the challenges and future directions for (1) histomorphometry of bone marrow adipocytes, (2) ex vivo BMA imaging, (3) in vivo BMA imaging, (4) cell isolation, culture, differentiation and in vitro modulation of primary bone marrow adipocytes and bone marrow stromal cell precursors, (5) lineage tracing and in vivo BMA modulation, and (6) BMA biobanking. We identify as accepted standards in BMA research: manual histomorphometry and osmium tetroxide 3D contrast-enhanced µCT for ex vivo quantification, specific MRI sequences (WFI and H-MRS) for in vivo studies, and RT-qPCR with a minimal four gene panel or lipid-based assays for in vitro quantification of bone marrow adipogenesis. Emerging techniques are described which may soon come to complement or substitute these gold standards. Known confounding factors and minimal reporting standards are presented, and their use is encouraged to facilitate comparison across studies. In conclusion, specific BMA methodologies have been developed. However, important challenges remain. In particular, we advocate for the harmonization of methodologies, the precise reporting of known confounding factors, and the identification of methods to modulate BMA independently from other tissues. Wider use of existing animal models with impaired BMA production (e.g., Pfrt-/-, KitW/W-v) and development of specific BMA deletion models would be highly desirable for this purpose.

Carpal tunnel ultrasound: is the "safe zone" on the ulnar side of the median nerve really avascular?

INTRODUCTION: Numerous publications have studied the regional anatomy of the carpal tunnel to define a "safe zone" to reduce the risk of perioperative neurovascular complications. This zone, located between the ulnar neurovascular bundle and the median nerve, is considered to be safe mainly because of the absence of vascular structures. This study aims to assess the presence of arterioles within this area using superb microvascular imaging (SMI). MATERIALS AND METHODS: The images from patients who underwent a bilateral routine wrist ultrasound with SMI, between January 28 and February 28, 2019, were retrospectively reviewed by two radiologists to evaluate the presence and location of arterioles in the safe zone. In addition, cadaveric wrists injected with intra-arterial red latex underwent dissection of the carpal tunnel. RESULTS: The images from 27 patients (54 wrists) were reviewed. In the safe zone, arterioles were seen superficial to the retinaculum in 36 wrists (36/54; 66.7%) and deep to the retinaculum in 21 wrists (21/54; 38.9%). The arterioles located deep to the retinaculum were more frequently found close to the median nerve (21/54; 38.9%) than to the ulnar artery (9/54; 16.7%). In five cadaveric wrists, arterioles were detected superficial to the retinaculum in 3 wrists (3/5; 60%) and deep to the retinaculum in 2 wrists (2/5; 40%). CONCLUSION: Arterioles can be seen in the safe zone both superficial and deep to the flexor retinaculum. Deep to the retinaculum, they are mainly observed in the proximal aspect of the carpal tunnel and more frequently close to the median nerve. KEY POINTS: • Superb microvascular imaging (SMI) enables the visualization of arterioles within the "safe zone" of the carpal tunnel (visible both superficial and deep to the flexor retinaculum). • Arterioles were more frequently observed in the proximal aspect of the carpal tunnel. • Deep to the retinaculum, arterioles were more frequently seen in proximity to the median nerve.

Proximal femur fat fraction variation in healthy subjects using chemical shift-encoding based MRI.

The objective of this study was to describe the normal variation of bone marrow fat content in the proximal femur considering the influence of side, age, sex and body mass index using fat fraction MRI. From September 2012 to July 2016, the MRI of 131 patients (258 hips) considered to have a normal MRI appearance were retrospectively evaluated. Patient records were searched to allow calculation of the body mass index (BMI). Water-fat based chemical shift MRI was available for all patients included. Proton density fat fraction maps were calculated, and measurements were performed in the femoral epiphysis, intertrochanteric region, and greater trochanter. The influence of patient age, sex, hip side and BMI on fat fraction values was assessed. Fat fraction was significantly different in the different locations evaluated (P = 0.0001). Patient sex and age significantly influenced fat fraction values in all regions evaluated (P < 0.02) with the exception of the epiphysis for sex (p = 0.07). In all locations, PDFF values were higher in men compared to women (3.3%, 4.4% and 13.1% higher in the epiphysis, greater trochanter and intertrochanteric region respectively). The intertrochanteric region presented the lowest fat fraction values with the highest variation compared to the greater trochanter and the epiphysis. BMI only influenced fat fraction values in the intertrochanteric region of females over 42 years old (P = 0.014). The interobserver variability of the measurements performed was considered to be excellent (ICC = 0.968). In conclusion, patient sex, age, and measurement location significantly influenced fat fraction values indicating that specific standards of reference are needed depending on these factors.