Neural Reward Representations Enable Utilitarian Welfare Maximization.

From deciding which meal to prepare for our guests to trading off the proenvironmental effects of climate protection measures against their economic costs, we often must consider the consequences of our actions for the well-being of others (welfare). Vexingly, the tastes and views of others can vary widely. To maximize welfare according to the utilitarian philosophical tradition, decision-makers facing conflicting preferences of others should choose the option that maximizes the sum of the subjective value (utility) of the entire group. This notion requires comparing the intensities of preferences across individuals. However, it remains unclear whether such comparisons are possible at all and (if they are possible) how they might be implemented in the brain. Here, we show that female and male participants can both learn the preferences of others by observing their choices and represent these preferences on a common scale to make utilitarian welfare decisions. On the neural level, multivariate support vector regressions revealed that a distributed activity pattern in the ventromedial prefrontal cortex (VMPFC), a brain region previously associated with reward processing, represented the preference strength of others. Strikingly, also the utilitarian welfare of others was represented in the VMPFC and relied on the same neural code as the estimated preferences of others. Together, our findings reveal that humans can behave as if they maximized utilitarian welfare using a specific utility representation and that the brain enables such choices by repurposing neural machinery processing the reward others receive.

Assessment of fatty infiltration of the hamstring muscles in chronic proximal hamstring ruptures and effect on clinical outcomes after surgical repair: a novel application of the Goutallier classification.

INTRODUCTION: Increased time to surgery has been previously associated with poorer clinical outcomes after surgical treatment of proximal hamstring ruptures, though the etiology remains unclear. The purpose of this study was to evaluate whether degree of muscle atrophy, as assessed using the Goutallier classification system, is associated with worse outcomes following surgical treatment of chronic proximal hamstring ruptures. MATERIALS AND METHODS: This was a retrospective case series of patients who underwent repair of proximal hamstring ruptures from 2012 to 2020 with minimum 2-year follow-up. Patients were included if they underwent primary repair of a proximal hamstring rupture ≥ 6 weeks after the date of injury and had accessible preoperative magnetic resonance imaging (MRI). Exclusion criteria were allograft reconstruction, endoscopic repair, or prior ipsilateral hip surgery. Patients were administered validated surveys: the modified Harris Hip Score (mHHS) and Perth Hamstring Assessment Tool (PHAT). Fatty atrophy on preoperative MRI was independently graded by two musculoskeletal radiologists using the Goutallier classification. Multivariate regression analysis was performed to evaluate associations of preoperative characteristics with muscle atrophy, as well as mHHS and PHAT scores. RESULTS: Complete data sets were obtained for 27 patients. A majority of this cohort was male (63.0%), with a mean age of 51.5 ± 11.8 years and BMI of 26.3 ± 3.8. The mean follow-up time was 62.6 ± 23.1 months, and the mean time from injury-to-surgery was 20.4 ± 15.3 weeks. The Goutallier grading inter-reader weighted kappa coefficient was 0.655. Regression analysis demonstrated that atrophy was not significantly associated with PHAT (p = 0.542) or mHHS (p = 0.574) at latest follow-up. Increased age was significantly predictive of muscle atrophy (ß = 0.62, p = 0.005) and was also found to be a significant predictor of poorer mHHS (ß = - 0.75; p = 0.037). CONCLUSIONS: The degree of atrophy was not found to be an independent predictor of clinical outcomes following repair of chronic proximal hamstring ruptures. Increasing age was significantly predictive of increased atrophy and poorer patient-reported outcomes.

Imaging assessment of spine infection.

This article comprehensively reviews current imaging concepts in spinal infection with primary focus on infectious spondylodiscitis (IS) as well as the less common entity of facet joint septic arthritis (FSA). This review encompasses the multimodality imaging appearances (radiographs, CT, MRI, and nuclear imaging) of spinal infection-both at initial presentation and during treatment-to aid the radiologist in guiding diagnosis and successful management. We discuss the pathophysiology of spinal infection in various patient populations (including the non-instrumented and postoperative spine) as well as the role of imaging-guided biopsy. We also highlight several non-infectious entities that can mimic IS (both clinically and radiologically) that should be considered during image interpretation to avoid misdiagnosis. These potential mimics include the following: Modic type 1 degenerative changes, acute Schmorl's node, neuropathic spondyloarthropathy, radiation osteitis, and inflammatory spondyloarthropathy (SAPHO syndrome).

Utility of a 2D kinematic HASTE sequence in magnetic resonance imaging assessment of adjacent segment degeneration following anterior cervical discectomy and fusion.

OBJECTIVES: To evaluate a dynamic half-Fourier acquired single turbo spin echo (HASTE) sequence following anterior cervical discectomy and fusion (ACDF) at the junctional level for adjacent segment degeneration comparing dynamic listhesis to radiographs and assessing dynamic cord contact and deformity during flexion-extension METHODS: Patients with ACDF referred for cervical spine MRI underwent a kinematic flexion-extension sagittal 2D HASTE sequence in addition to routine sequences. Images were independently reviewed by three radiologists for static/dynamic listhesis, and compared to flexion-extension radiographs. Blinded assessment of the HASTE sequence was performed for cord contact/deformity between neutral, flexion, and extension, to evaluate concordance between readers and inter-modality agreement. Inter-reader agreement for dynamic listhesis and impingement grade and inter-modality agreement for dynamic listhesis on MRI and radiographs was assessed using the kappa coefficient and percentage concordance. RESULTS: A total of 28 patients, mean age 60.2 years, were included. Mean HASTE acquisition time was 42 s. 14.3% demonstrated high grade dynamic stenosis (> grade 4) at the adjacent segment. There was substantial agreement for dynamic cord impingement with 70.2% concordance (kappa = 0.62). Concordance across readers for dynamic listhesis using HASTE was 81.0% (68/84) (kappa = 0.16) compared with 71.4% (60/84) (kappa = 0.40) for radiographs. Inter-modality agreement between flexion-extension radiographs and MRI assessment for dynamic listhesis across the readers was moderate (kappa = 0.41; 95% confidence interval: 0.16 to 0.67). CONCLUSIONS: A sagittal flexion-extension HASTE cine sequence provides substantial agreement between readers for dynamic cord deformity and moderate agreement between radiographs and MRI for dynamic listhesis. CLINICAL RELEVANCE STATEMENT: Degeneration of the adjacent segment with instability and myelopathy is one of the most common causes of pain and neurological deterioration requiring re-operation following cervical fusion surgery. KEY POINTS: • A real-time kinematic 2D sagittal HASTE flexion-extension sequence can be used to assess for dynamic listhesis, cervical cord, contact and deformity. • The additional kinematic cine sequence was well tolerated and the mean acquisition time for the 2D HASTE sequence was 42 s (range 31-44 s). • A sagittal flexion-extension HASTE cine sequence provides substantial agreement between readers for dynamic cord deformity and moderate agreement between radiographs and MRI for dynamic listhesis.

Decreased Hip Labral Width Measured on Preoperative Magnetic Resonance Imaging Is Associated With Greater Revision Rate After Primary Arthroscopic Labral Repair for Femoroacetabular Impingement Syndrome at 5-Year Follow-Up.

PURPOSE: To examine the associations between hip labral width and patient-reported outcomes, clinical threshold achievement rates, and rate of reoperation among patients with femoroacetabular impingement syndrome (FAIS) who underwent hip arthroscopy and labral repair at minimum 5-year follow-up. METHODS: Patients were identified from a prospective database who underwent primary hip arthroscopy for treatment of labral tears and FAIS. Modified Harris Hip Score (mHHS) and Nonarthritic Hip Score (NAHS) were recorded preoperatively and at 5-year follow-up. Achievement of the minimal clinically important difference (MCID), substantial clinical benefit (SCB), and patient-acceptable symptom state (PASS) was determined using previously established values. Labral width magnetic resonance imaging measurements were performed by 2 independent readers at standardized "clockface" locations. Patients were stratified into 3 groups at each position: lower-width (<½ SD below mean), middle-width (within ½ SD of mean), and upper-width (>½ SD above mean). Multivariable regression was used to evaluate associations of labral width with patient-reported outcomes and reoperation rate. RESULTS: Seventy-three patients (age: 41.0 ± 12.0 years; 68.5% female) were included. Inter-rater reliability for labral width measurements was high at all positions (intraclass correlation coefficient 0.94-0.96). There were no significant intergroup differences in mHHS/NAHS improvement (P > .05) or in achievement rates of MCID/SCB/PASS at each clockface position (P > .05). Eleven patients (15.1%) underwent arthroscopic revision and 4 patients (5.5%) converted to total hip arthroplasty. Multivariable analysis found lower-width groups at 11:30 (odds ratio 1.75, P = .02) and 3:00 (odds ratio 1.59, P = .04) positions to have increased odds of revision within 5 years; however, labral width was not associated with 5-year improvement in mHHS/NAHS, achievement of MCID/PASS/SCB, or conversion to total hip arthroplasty (P > .05). CONCLUSIONS: Hip labral width <½ SD below the mean measured on preoperative magnetic resonance imaging at 11:30- and 3:00-clockface positions was associated with increased odds of reoperation after arthroscopic labral repair and treatment of FAIS. Labral width was not associated with 5-year improvement of mHHS, NAHS, achievement of clinical thresholds, or conversion to arthroplasty. LEVEL OF EVIDENCE: Level IV, case series.

Tips and tricks in ultrasound-guided musculoskeletal interventional procedures.

Ultrasound visualization affords proceduralists versatile and accurate guidance for a variety of percutaneous, minimally invasive procedures in the musculoskeletal system including joint (intra-articular) injections or aspirations, intra-bursal injections, peritendinous, and perineural injections. A variety of percutaneous procedures are traditionally performed blindly, but may be more easily or more accurately performed with the real-time assistance of ultrasound guidance. Other procedures are only possible utilizing image-guidance, due to the required precision of the injection because of delicate local anatomy or depth of the injection; ultrasound is a safe, portable, and widespread modality that can be used to assist the proceduralist in localizing the needle tip in such cases, to ensure safe and accurate delivery of the medication, most frequently a solution of steroid and anesthetic. This review aims to provide a foundational approach to ultrasound-guided procedures in the musculoskeletal system, offering tips and tricks that can be employed in many different procedures including intra-articular, juxta-articular, and perineural injections for a multitude of clinical scenarios. Technical considerations regarding ultrasound transducer selection, sonographic technique, as well as common indications, contraindications, and complications of these procedures, are presented. Additionally, a variety of pharmacologic considerations for proceduralists contemplating ultrasound-guided injections are discussed.

Extended and weightbearing wrist 3-T MRI using a novel harness and flexible 24-channel glove coil to evaluate carpal kinematics: a pilot study in 10 volunteers.

BACKGROUND: Wrist pain in the extended or extended weightbearing positions may be incompletely evaluated using standard magnetic resonance imaging (MRI) with standard rigid clamshell coils in the neutral position. PURPOSE: To evaluate a flexible 24-channel glove coil and harness when imaging the wrist in neutral, dorsally extended, and weightbearing positions. MATERIAL AND METHODS: Ten wrists in 10 asymptomatic volunteers (mean age = 29 years) were scanned. Participants underwent 3-T MRI using the harness and flexible glove coil, acquiring sagittal turbo spin echo (TSE) and half-Fourier acquisition single-shot turbo spin echo (HASTE) pulse sequences. Static TSE images were obtained in neutral, extended, and weightbearing positions using proton density parameters and independently evaluated by two radiologists for: dorsal radiocarpal ligament thickness; radiocapitate, radiolunate, and capitatolunate angles; palmar translation of the lunate on the radius; angulation of the extensor tendons; and distance from the distal extensor retinaculum to Lister's tubercle. Cine HASTE images were dynamically acquired between neutral-maximum extension to measure the radiocapitate angle. RESULTS: Good reader agreement was observed (r > 0.73) for all measurements except palmar translation in the neutral position (r = 0.27). Significant increases in dorsal radiocarpal ligament thickness; radiocapitate, radiolunate and capitolunate angulation; and extensor tendon angulation were observed between the neutral and extended positions (P < 0.001). A further significant increase in these metrics between extended and weightbearing positions was also seen (P < 0.01). CONCLUSION: Significant increases in dorsal radiocarpal ligament thickness, articular and tendon angulations occur during wrist extension, that further increase with dorsal weightbearing.

Musculoskeletal Soft-tissue Masses: MR imaging-Ultrasonography Correlation, with an Emphasis on the 2020 World Health Organization Classification.

Evaluation of soft-tissue masses has become a common clinical practice indication for imaging with both ultrasound and MR imaging. We illustrate the ultrasonography and MR imaging appearances of soft-tissue masses based on the various categories, updates, and reclassifications of the 2020 World Health Organization classification.

Image-Guided Radar Reflector Localization for Small Soft-Tissue Lesions in the Musculoskeletal System.

Preoperative localization of nonpalpable breast lesions using a radar reflector surgical guidance system has become commonplace, but the clinical utility of this emerging technology in the musculoskeletal system has not yet been well established. The system components include a console, a handpiece, an implanted radiofrequency reflector that works as a lesion marker, and an infrared light-emitting probe to guide the surgeon. The reflector can be deployed to localize small nonpalpable nodules within the subcutaneous fat as well as lesions within the deeper soft tissues. It can also be used for lymph nodes and foreign bodies. Localization can be performed both before and after treatment. The objective of this article is to describe the potential applications and our technique and initial experience for radar reflector localization within the musculoskeletal system.

Postoperative MR Imaging of Joints: Technical Considerations.

Postoperative MR imaging of joints is now commonly requested, yet artifacts caused by metallic orthopedic implants remain a significant challenge during image interpretation. Effective artifact reduction is essential to identify postsurgical complications, such as prosthesis loosening, infection, adverse local tissue reaction, and periarticular soft tissue injuries. This article reviews basic and advanced metal artifact reduction MR imaging techniques applied to various clinical protocols for successful postoperative MR imaging of small and large joints.

Analysis of Factors Potentially Influencing Diagnostic Yield Among Computed Tomography-Guided Biopsies for Bone Lesions.

OBJECTIVE: This study aimed to investigate patient-specific, lesion-related, and technical factors that potentially influence diagnostic yield of computed tomography (CT)-guided biopsies of bone lesions. METHODS: Computed tomography-guided bone lesion biopsies performed over a 2-year period were retrospectively reviewed, including image review and electronic medical records for pathology reports and clinical follow-up. Lesions were tabulated by prebiopsy CT and magnetic resonance imaging features. Patients with nondiagnostic biopsies were assessed for presumptive clinical diagnosis and management. RESULTS: Nondiagnostic pathology results were obtained in 31 of 156 cases (19.87%), among which diagnoses were confirmed by other tissue sampling in 9; clinical follow-up of up to 2 years yielded no diagnosis in 10 and presumptive diagnoses in 12. The nondiagnostic biopsy rate of long bone lesions was higher than that of other bone lesions (odds ratio, 3.46; 95% confidence interval, 1.32-9.09). There were no significant differences in patient American Society of Anesthesiologists class, mean body mass index, sedation method, number of cores, or needle gauge between diagnostic and nondiagnostic biopsy cohorts. Diagnostic yield was not significantly different between occult, lytic, or sclerotic lesions. There was no difference in diagnostic yield regarding presence of cortical break, gadolinium enhancement, or lesion depth. Magnetic resonance imaging was obtained before biopsy in significantly more nondiagnostic cases compared with diagnostic cases ( P = 0.027). CONCLUSIONS: Computed tomography-guided biopsies had a nondiagnostic rate of 19.87%, and lesions in the long bones of the extremities were disproportionately common among this group. There was no significant association between biopsy results and several patient-specific, lesion-related, and technical factors.

Editorial Commentary: Real-Time Dynamic Magnetic Resonance Imaging of the Patellofemoral Joint: Ready for Prime Time?

Real-time dynamic magnetic resonance imaging (MRI) in the musculoskeletal system touts the ability to perceive in vivo joint kinematics, which is particularly attractive for diagnosing dynamic pathologies such as joint instability or impingement syndromes.The clinical utility of dynamic MRI in the musculoskeletal system is wide ranging, from patellofemoral kinematics to imaging of the hip in femoroacetabular impingement and also dynamic spine imaging. Patellofemoral instability is an ideal diagnostic target, as knee flexion and extension are easily performed in an MRI scanner, and dynamic measurements have been correlated to clinical and static radiologic parameters of instability. Proving the clinical utility of this MRI technique requires rigorous technical standardization and definition of normal patellofemoral motion parameters. Validated imaging methods and rigorously defined normal range data are required to light the path forward, and the video format of dynamic MRI is also ideal for advancing patient-centered care, improving patient literacy on their condition, and offering a potential catalyst for shared decision-making between surgeons and their patients.

Incidence of infectious complications following ultrasound-guided percutaneous musculoskeletal interventions with the use of an uncovered transducer footprint.

OBJECTIVES: To determine the incidence of infectious complications following ultrasound-guided musculoskeletal interventions performed with a disinfected uncovered ultrasound transducer footprint. METHODS: Electronic medical records of all patients who underwent an ultrasound-guided musculoskeletal procedure (including injection, calcific lavage, or ganglion cyst aspiration) performed by any of the 14 interventional musculoskeletal radiologists at our institution between January 2013 and December 2018 were retrospectively reviewed to identify procedure site infections. Biopsies and joint aspirations were excluded. The procedures were performed using a disinfected uncovered transducer footprint. First, an automated chart review identified cases with (1) positive answers to the nurse's post-procedure call, (2) an International Classification of Diseases (ICD) diagnostic code related to a musculoskeletal infection, or (3) an antibiotic prescription within 30 days post-procedure. Then, these cases were manually reviewed for evidence of procedure site infection. RESULTS: In total, 6511 procedures were included. The automated chart review identified 3 procedures (2 patients) in which post-procedural fever was reported during the nurse's post-procedure call, 33 procedures (28 patients) with an ICD code for a musculoskeletal infection, and 220 procedures (216 patients) with an antibiotic prescription within 30 post-procedural days. The manual chart review of these patients revealed no cases of confirmed infection and 1 case (0.015%) of possible site infection. CONCLUSIONS: The incidence of infectious complications after an ultrasound-guided musculoskeletal procedure performed with an uncovered transducer footprint is extremely low. This information allows radiologists to counsel their patients more precisely when obtaining informed consent. KEY POINTS: • Infectious complications after ultrasound-guided musculoskeletal procedures performed with a disinfected uncovered transducer footprint are extremely rare.

Interventional Imaging Techniques as Alternative to Surgery of the Foot and Ankle.

A variety of foot and ankle pathologies can impair patient's daily activities, ultimately requiring surgical management. However, with improvements in image-guided intervention, the joints, soft tissues, and osseous structures may be accessible using various percutaneous techniques as a potential alternative therapeutic tool, avoiding the need for surgery with its associated risks and morbidity. This article discusses the potential range of image-guided interventional treatments. Injections, aspiration, biopsies, cryoablation, and radiofrequency ablation are described. Newer novel treatments are also covered. Finally, the common pathologies of Morton's neuroma, Achilles tendinopathy, and plantar fasciitis are addressed.

Testing models at the neural level reveals how the brain computes subjective value.

Decisions are based on the subjective values of choice options. However, subjective value is a theoretical construct and not directly observable. Strikingly, distinct theoretical models competing to explain how subjective values are assigned to choice options often make very similar behavioral predictions, which poses a major difficulty for establishing a mechanistic, biologically plausible explanation of decision-making based on behavior alone. Here, we demonstrate that model comparison at the neural level provides insights into model implementation during subjective value computation even though the distinct models parametrically identify common brain regions as computing subjective value. We show that frontal cortical regions implement a model based on the statistical distributions of available rewards, whereas intraparietal cortex and striatum compute subjective value signals according to a model based on distortions in the representations of probabilities. Thus, better mechanistic understanding of how cognitive processes are implemented arises from model comparisons at the neural level, over and above the traditional approach of comparing models at the behavioral level alone.

Ultrasound of the symptomatic shoulder arthroplasty: Spectrum and prevalence of periarticular soft tissue pathology.

PURPOSE: To describe our experience using ultrasound (US) to evaluate postoperative complications in the presence of in situ shoulder arthroplasty. METHODS: Review of patients who underwent US evaluation following total shoulder arthroplasty (TSA), reverse total shoulder arthroplasty (RTSA) or hemiarthroplasty from 2007 to 2020. All studies were reviewed independently by two musculoskeletal radiologists to assess for joint effusion, periarticular collection, and characterization of associated rotator cuff tears. Tendon tears were assessed with respect to (1) thickness: low grade (<50% thickness), high grade (>50% thickness), full thickness; (2) morphology (focal vs. diffuse) and location (insertion vs. critical zone). Inter-reader agreements were determined using Cohen's kappa test. RESULTS: Ninety-seven studies were performed in 72 patients following TSA, RTSA, or hemiarthroplasty. Thirty-seven exams were solely for diagnostic purposes, and 59 were for guiding joint or periarticular collection aspiration. Twenty-eight studies assessed the cuff tendons post TSA. The mean time between surgery and US examination was 29.2 months. Complete or high-grade tears were identified in 8/28 (28.6%) diagnostic exams. The most commonly torn tendon among TSA patients was the subscapularis, with 13/28 (46.4%) demonstrating at least partial tearing. Inter-reader agreement was excellent for presence of effusion (k = 0.79, p < .001) and periarticular collection (k = 0.87, p < .001), and excellent agreement for presence of subscapularis tear (k = 0.78, p < .001), with fair agreement for assessment of supraspinatus (k = 0.66, p < .001) and infraspinatus (k = 0.60, p < .001) tears. CONCLUSION: The most commonly torn tendon following anatomic TSA identified by US was the subscapularis, which was torn or deficient in 46.4% of cases. The majority of studies were performed for the guidance of percutaneous aspiration.

Imaging Spectrum of Calvarial Abnormalities.

Calvarial abnormalities are usually discovered incidentally on radiologic studies or less commonly manifest with symptoms. This narrative review describes the imaging spectrum of the abnormal calvaria. The extent, multiplicity, and other imaging features of calvarial abnormalities can be combined with the clinical information to establish a final diagnosis or at least narrow the differential considerations. Prior trauma (congenital depression, leptomeningeal cysts, posttraumatic osteolysis), surgical intervention (flap osteonecrosis and burr holes), infection, and inflammatory processes (sarcoidosis) can result in focal bone loss, which may also be seen with idiopathic disorders without (bilateral parietal thinning and Gorham disease) or with (Parry-Romberg syndrome) atrophy of the overlying soft tissues. Anatomic variants (arachnoid granulations, venous lakes, parietal foramina) and certain congenital lesions (epidermoid and dermoid cysts, atretic encephalocele, sinus pericranii, and aplasia cutis congenita) manifest as solitary lytic lesions. Other congenital entities (lacunar skull and dysplasia) display a diffuse pattern of skull involvement. Several benign and malignant primary bone tumors involve the calvaria and manifest as lytic, sclerotic, mixed lytic and sclerotic, or thinning lesions, whereas multifocal disease is mainly due to hematologic or secondary malignancies. Metabolic disorders such as rickets, hyperparathyroidism, renal osteodystrophy, acromegaly, and Paget disease involve the calvaria in a more diffuse pattern. Online supplemental material is available for this article. ©RSNA, 2021.

Distance of the Posterior Interosseous Nerve From the Bicipital (Radial) Tuberosity at Varying Positions of Forearm Rotation: A Magnetic Resonance Imaging Study With Clinical Implications.

BACKGROUND: The proximity of the posterior interosseous nerve (PIN) to the bicipital tuberosity is clinically important in the increasingly popular anterior single-incision technique for distal biceps tendon repair. Maximal forearm supination is recommended during tendon reinsertion from the anterior approach to ensure the maximum protective distance of the PIN from the bicipital tuberosity. PURPOSE: To compare the location of the PIN on magnetic resonance imaging (MRI) relative to bicortical drill pin instrumentation for suspensory button fixation via the anterior single-incision approach in varying positions of forearm rotation. STUDY DESIGN: Descriptive laboratory study. METHODS: Axial, non-fat suppressed, T1-weighted MRI scans of the elbow were obtained in positions of maximal supination, neutral, and maximal pronation in 13 skeletally mature individuals. Distances were measured from the PIN to (1) the simulated path of an entering guidewire (GWE-PIN) and (2) the cortical starting point of the guidewire on the bicipital tuberosity (CSP-PIN) achievable from the single-incision approach. To radiographically define the location of the nerve relative to constant landmarks, measurements were also made from the PIN to (3) the prominent-most point on the bicipital tuberosity (BTP-PIN) and (4) a perpendicular plane trajectory from the bicipital tuberosity exiting the opposing radial cortex (PPT-PIN). All measurements were subsequently compared between positions of pronation, neutral, and supination. In supination only, BTP-PIN and PPT-PIN measurements were made and compared at 3 sequential axial levels to evaluate the longitudinal course of the nerve relative to the bicipital tuberosity. RESULTS: Of the 13 study participants, mean age was 38.77 years, and mean body mass index was 25.58. Five participants were female, and 5 left and 8 right elbow MRI scans were reviewed. The GWE-PIN was significantly greater in supination (mean ± SD, 16.01 ± 2.9 mm) compared with pronation (13.66 ± 2.5 mm) (P < .005). The mean CSP-PIN was significantly greater in supination (16.20 ± 2.8 mm) compared with pronation (14.18 ± 2.4 mm) (P < .013).The mean PPT-PIN was significantly greater in supination (9.00 ± 3.0 mm) compared with both pronation (1.96 ± 1.2 mm; P < .001) and neutral (4.73 ± 2.6 mm; P < .001). The mean BTP-PIN was 20.54 ± 3.0, 20.81 ± 2.7, and 20.35 ± 2.9 mm in pronation, neutral, and supination, respectively, which did not significantly differ between positions. In supination, the proximal, midportion, and distal measurements of BTP-PIN did not significantly differ. The proximal PPT-PIN distance (9.08 ± 2.9 mm) was significantly greater than midportion PPT-PIN (5.85 ± 2.4 mm; P < .001) and distal BTP-PIN (2.27 ± 1.8 mm; P < .001). CONCLUSION: This MRI study supports existing evidence that supination protects the PIN from the entering guidewire instrumentation during anterior, single-incision biceps tendon repair using cortical button fixation. The distances between the entering guidewire trajectory and PIN show that guidewire-inflicted injury to the nerve is unlikely during the anterior single-incision approach. CLINICAL RELEVANCE: When a safe technique is used, PIN injuries during anterior repair are likely the result of aberrant retractor placement, and we recommend against the use of retractors deep to the radial neck. Guidewire placement as close as possible to the anatomic footprint of the biceps tendon is safe from the anterior approach. MRI evaluation confirms that ulnar and proximal guidewire trajectory is the safest technique when using single-incision bicortical suspensory button fixation.

Why We Learn Less from Observing Outgroups.

Humans are less likely to learn from individuals belonging to a different group (outgroup) than from individuals of their own group (ingroup), yet the source of this societally relevant deficit has remained unclear. Here we used neuroimaging and computational modeling to investigate how people learn from observing the actions and outcomes of ingroup and outgroup demonstrators. Politically left-wing male and female participants performed worse when observing computer-simulated actions they believed were from a right-wing outgroup member compared with those from a left-wing ingroup member. A control experiment in which participants observed choices from a nonhuman agent confirmed that this performance difference reflected an outgroup deficit, rather than an ingroup gain. Accounting for the outgroup deficit, a computational model showed that participants relied less on information from outgroup actions compared with ingroup actions, while learning from outgroup outcomes was not impaired. At the neural level, the differences in observational ingroup versus outgroup learning were reflected in lateral prefrontal activity. The stronger the activity in this region, the more strongly participants weighed ingroup compared with outgroup learning signals (action prediction errors), which formally captured deficits in outgroup learning. Together, our work provides a computational and neural account of why people learn less from observing outgroups.SIGNIFICANCE STATEMENT Learning from observing others is an efficient way to acquire knowledge. In our globalized world, "the others" often are people from a different social group (outgroup). There is evidence that people learn less from observing outgroup individuals compared with individuals from their own group (ingroup). However, the source of this outgroup deficit in observational learning remained unknown, which limits our chances to improve intergroup learning. Our results showed that participants rely less on observed outgroup actions compared with ingroup actions, while learning from outgroup outcomes is not impaired. On the neural level, this outgroup deficit was reflected in the activation of the inferior frontal gyrus. These findings imply that intergroup learning should rely on observing outcomes, rather than actions.

Does Magnetic Resonance Imaging After Diagnostic Ultrasound for Soft Tissue Masses Change Clinical Management?

OBJECTIVES: To evaluate whether a follow-up magnetic resonance imaging (MRI) scan performed after initial ultrasound (US) to evaluate soft tissue mass (STM) lesions of the musculoskeletal system provides additional radiologic diagnostic information and alters clinical management. METHODS: A retrospective chart review was performed of patients undergoing initial US evaluations of STMs of the axial or appendicular skeleton between November 2012 and March 2019. Patients who underwent US examinations followed by MRI for the evaluation of STM lesions were identified. For inclusion, the subsequent pathologic correlation was required from either a surgical or image-guided biopsy. Imaging studies with pathologic correlations were then reviewed by 3 musculoskeletal radiologists, who were blinded to the pathologic diagnoses. The diagnostic utility of MRI was then assessed on the basis of a 5-point grading scale, and inter-reader agreements were determined by the Fleiss κ statistic. RESULTS: Ninety-two patients underwent MRI after US for STM evaluations. Final pathologic results were available in 42 cases. Samples were obtained by surgical excision or open biopsy (n = 34) or US-guided core biopsy (n = 8). The most common pathologic diagnoses were nerve sheath tumors (n = 9), lipomas (n = 5), and leiomyomas (n = 5). Imaging review showed that the subsequent MRI did not change the working diagnosis in 73% of cases, and the subsequent MRI was not considered to narrow the differential diagnosis in 68% of cases. There was slight inter-reader agreement for the diagnostic utility of MRI among individual cases (κ = 0.10) between the 3 readers. CONCLUSIONS: The recommendation of MRI to further evaluate STM lesions seen with US frequently fails to change the working diagnosis or provide significant diagnostic utility.