Postoperative MR Imaging of the Elbow.

Elbow injuries are a growing problem particularly among overhead athletes, because more children and adolescents are participating in sporting activities. The goal of surgical management of elbow injuries is to restore the capsuloligamentous and osseous contributions to stability. However, postoperative MR imaging evaluation is difficult because of the variety of surgical techniques available, and the lack of postoperative MR imaging for suspected complications because many are diagnosed clinically and a revision may be performed without imaging. This article reviews some of the commonly performed surgical techniques for select elbow injuries, with their postoperative MR imaging findings and complications.

Nerve Entrapments in the Pelvis and Hip.

Clinical symptoms of pelvic entrapment neuropathies are widely variable and frequently nonspecific, thus rendering it difficult to localize and diagnose. Magnetic resonance imaging (MRI), and in particular MR neurography, has become increasingly important in the work-up of entrapment neuropathies involving the pelvic and hip nerves of the lumbosacral plexus. The major sensory and motor peripheral nerves of the pelvis and hip include the sciatic nerve, superior and inferior gluteal nerves, femoral nerve, lateral femoral cutaneous nerve, obturator nerve, and pudendal nerve. Familiarity with the anatomy and imaging appearance of normal and pathologic nerves in combination with clinical presentation is crucial in the diagnosis of entrapment neuropathies.

Supraspinatus fatty infiltration on MRI among older adults receiving physical therapy as initial management for clinically suspected rotator cuff tear: A pilot study.

Objectives: Rotator cuff (RC) tear is common among adults ≥60 years, with supraspinatus tear most common. Intramuscular fatty infiltration (FI) on imaging is predictive of long-term outcomes following RC tear. Physical therapists routinely diagnose RC tear only by clinical examination since most do not order imaging studies. Thus, there is limited knowledge about FI in older populations receiving physical therapy (PT) for initial management of RC tear. The primary objective of our pilot study is to determine longitudinal differences in supraspinatus FI over time among older adults receiving PT (PT cohort) for initial management of RC tear relative to older adult volunteers (control cohort), and with secondary objective to evaluate longitudinal self-reported shoulder function over time. Material and Methods: This was a prospective longitudinal cohort study. Forty adults, 60-85 years, were enrolled at baseline; one follow-up visit at ≥6 months. Shoulder magnetic resonance imaging and clinical screening for Charlson comorbidity index (CCI), body mass index (BMI), and American Shoulder and Elbow Surgeon (ASES) score were completed at baseline and follow-up visits. Supraspinatus FI was evaluated by 6-point Dixon fat fraction and Goutallier grade. PT (n = 15) and control (n = 25) cohorts were stratified by supraspinatus status: Intact (no tear), partial-thickness tear (PTT), and full-thickness tear (FTT). Comparisons within cohort were performed by Kruskal-Wallis test and between cohorts by Mann-Whitney U-test. Interobserver reliability was performed for Dixon fat fraction and Goutallier grade. Results: PT cohort at baseline showed no difference for age, BMI, CCI, and ASES score; supraspinatus FI was highest for FTT by Goutallier grade (no tear, 0.5 ± 0.5; PTT, 1.1 ± 0.2; and FTT, 1.5 ± 0.5; P = 0.033) and by Dixon fat fraction (no tear, 4.6% ± 1.4%; PTT, 6.1% ± 1.9%; and FTT, 6.7% ± 2.5%; P = 0.430). Control cohort at baseline showed no difference for age, BMI, CCI, and ASES score; supraspinatus FI was highest for supraspinatus FTT by Dixon fat fraction (no tear, 5.8% ± 1.2%; PTT, 7.1% ± 6.3%; and FTT, 21.4% ± 10.4%; P = 0.034) and by Goutallier grade (no tear, 0.8 ± 0.5; PTT, 1.0 ± 0.6; and FTT, 2.4 ± 1.7; P = 0.141). No difference between similar PT and control cohort subgroups at baseline except no tear groups for ASES score (PT cohort, 58.9 ± 8.2; control cohort, 84.0 ± 21.9; P = 0.049). No differences were identified for Δ-Dixon fat fraction and Δ-Goutallier grade over time in the PT and control cohorts. PT cohort no tear subgroup showed significant improvement (P = 0.042) for Δ-ASES score over time relative to PTT and FTT subgroups; no difference for Δ-ASES score over time in the control cohort. Conclusion: Full-thickness RC tear showed higher levels of FI relative to PTT or no tear at baseline. Our pilot study's trend suggested that older adults receiving PT for initial management of RC tear have full-thickness RC tear for shorter duration based on relative lower levels of FI at baseline as compared to older adult volunteers with full-thickness RC tear. Our pilot study also found that older adults in the PT cohort with no tear had superior shoulder functional recovery by ASES score over time relative to full-thickness and PTTs.

MRI of Traumatic Knee Dislocation: A Study to Evaluate Safety and Image Quality for Patients with Knee-Spanning Stabilization Devices.

This study evaluated safety and image quality of MRI exams performed for patients with traumatic knee dislocations in knee-spanning stabilization devices. It is an IRB-approved retrospective design with waived informed consent that included 63 patients with traumatic knee dislocation. 56 patients had metallic external fixators, and 7 patients had non-metallic knee immobilizers. 7 patients had bilateral dislocations yielding a total of 70 knee MRIs. 1.5 Tesla MRI exams were performed for all patients who were awake and alert at the time of imaging. All knee-spanning external fixators were considered "MR conditional" by the FDA. The electronic medical record was reviewed for notes from the technologist and nursing staff documenting any patient complaints or adverse events during the MRI exam as required by departmental protocol. Qualitative analysis of the six most frequently performed sequences were independently conducted by 2 musculoskeletal radiologists using a 5-point Likert scale. Overall image quality and select time intervals between the two groups were compared using an independent sample t test and the Mann-Whitney U test, respectively. No adverse events were reported for a 40-minute average estimated patient scan time with the stabilization devices in the MR gantry. Mean values of Likert scale scores were generated from two readers' data for comparison between the external fixation and the immobilizer groups. Most knee MRI exams with external fixators were within diagnostic quality despite artifacts (grade 3). MRI exams generally were of higher diagnostic quality in the immobilizer group than the external fixator group (p < 0.05). The external fixator models included DePuy Synthes, Smith and Nephew, Stryker Hoffman III, Zimmer FastFrame, and Zimmer XtraFix. MRI examinations in patients with external fixators for traumatic knee dislocations can be safely performed under certain conditions and provide diagnostic quality images.

Glenoid bony morphology of osteoarthritis prior to shoulder arthroplasty: what the surgeon wants to know and why.

Shoulder arthroplasty is performed with increasing frequency, and osteoarthritis is the most common indication for this procedure. However, the glenoid side of the joint is widely recognized as a limiting factor in the long-term durability of shoulder replacement, and osteoarthritis leads to characteristic bony changes at the glenoid which can exacerbate this challenge by reducing the already limited glenoid bone stock, by altering biomechanics, and by interfering with operative exposure. This article reviews the Walch classification system for glenoid morphology. Several typical findings of osteoarthritis at the glenoid are discussed including central bone loss, posterior bone loss, retroversion, biconcavity, inclination, osteophyte formation, subchondral bone quality, and bone density. The three primary types of shoulder arthroplasty are reviewed, along with several techniques for addressing glenoid deformity, including eccentric reaming, bone grafting, and the use of augmented glenoid components. Ultimately, a primary objective at shoulder arthroplasty is to correct glenoid deformity while preserving bone stock, which depends critically on characterizing the glenoid at pre-operative imaging. Understanding the surgical techniques and the implications of glenoid morphology on surgical decision-making enables the radiologist to provide the morphologic information needed by the surgeon.

Morel-Lavallee Lesions-Review of Pathophysiology, Clinical Findings, Imaging Findings and Management.

Morel-Lavallee lesion is a post-traumatic soft tissue degloving injury. This is commonly associated with sports injury caused by a shearing force resulting in separation of the hypodermis from the deeper fascia. Most common at the greater trochanter, these injuries also occur at flank, buttock, lumbar spine, scapula and the knee. Separation of the tissue planes result in a complex serosanguinous fluid collection with areas of fat within it. The imaging appearance is variable and non specific, potentially mimicking simple soft tissue haematoma, superficial bursitis or necrotic soft tissue neoplasms. If not treated in the acute or early sub acute settings, these collections are at risk for superinfection, overlying tissue necrosis and continued expansion. In this review article, we discuss the clinical presentation, pathophysiology, imaging features and differential diagnostic considerations of Morel-Lavallee lesions. Role of imaging in guiding prompt and appropriate treatment has also been discussed.

VI. PERSON-SPECIFIC INDIVIDUAL DIFFERENCE APPROACHES IN DEVELOPMENTAL RESEARCH.

In this chapter, we demonstrate the way certain common analytic approaches (e.g., polynomial curve modeling, repeated measures ANOVA, latent curve, and other factor models) create individual difference measures based on a common underlying model. After showing that these approaches require only means and covariance (or correlation) matrices to estimate regression coefficients based on a hypothesized model, we describe how to recast these models based on time-series related approaches focusing on single subject time series approaches (e.g., vector autoregressive approaches and P-technique factor models). We show how these latter methods create parameters based on models that can vary from individual-to-individual. We demonstrate differences for the factor model using real data examples.

Longitudinal Stress Fracture of the Femur: A Rare Entity.

Exercise-induced stress reactions and stress fractures are common causes of pain in athletes. Although most stress fractures are trans- verse in orientation, rarely longitudinal stress fractures may occur in the tibia and femur. Early detection is important to start prompt and appropriate treatment to prevent complications. Thus, familiarity with the clinical presentation, imaging findings, and treatment of this rare entity are important for proper and timely treatment.

Medical Students' Understanding of Directed Questioning by Their Clinical Preceptors.

Phenomenon: Throughout clerkship, preceptors ask medical students questions for both assessment and teaching purposes. However, the cognitive and strategic aspects of students' approaches to managing this situation have not been explored. Without an understanding of how students approach the question and answer activity, medical educators are unable to appreciate how effectively this activity fulfills their purposes of assessment or determine the activity's associated educational effects. APPROACH: A convenience sample of nine 4th-year medical students participated in semistructured one-on-one interviews exploring their approaches to managing situations in which they have been challenged with questions from preceptors to which they do not know the answer. Through an iterative and recursive analytic reading of the interview transcripts, data were coded and organized to identify themes relevant to the students' considerations in answering such questions. FINDINGS: Students articulated deliberate strategies for managing the directed questioning activity, which at times focused on the optimization of their learning but always included considerations of image management. Managing image involved projecting not only being knowledgeable but also being teachable. The students indicated that their considerations in selecting an appropriate strategy in a given situation involved their perceptions of their preceptors' intentions and preferences as well as several contextual factors. Insights: The medical students we interviewed were quite sophisticated in their understanding of the social nuances of the directed questioning process and described a variety of contextually invoked strategies to manage the situation and maintain a positive image.

Morel-Lavallée Lesion: A Case of an American Football Injury.

Morel-Lavallée Lesion (MLL) is a posttraumatic, closed degloving injury where the skin and superficial fascia get separated from deep fascia (fascialata) in the trochanteric region and upper thigh, hence creating a potential space. Similar lesions at other locations (e.g., abdominal wall and lumbar regions) have been described as Morel-Lavallée effusion, hematoma, or extravasation. Injury to an area with rich vascular and lymphatic supply leads to filling of this space with blood, lymph, fat, and necrotic debris. MLL usually presents as painful fluctuant swelling in the anterolateral portion o fthe upper thigh. Many of these maybe missed at initial evaluation and present weeks to months after the initial trauma.

Dynamic models of biological pattern formation have some surprising implications for understanding the epigenetics of development.

Nonlinear epigenetic processes are conceived of in terms of self-organizing dynamic models of biological pattern formation. Epigenetic processes thus conceived generate substantial subject-specific structural variation, for instance, in growing brain networks. It is shown that standard quantitative genetic modeling based on analyses of interindividual phenotypic variation misclassifies the variation generated by nonlinear epigenetic processes as being due to specific environmental influences. A new quantitative genetic model, iFACE, is introduced to correctly identify the structural variation generated by self-organizing epigenetic processes. iFACE is based on time series analysis of intraindividual variation of a single pair of genetically related subjects. The results of an application of iFACE to multilead EEG obtained with a single dizygotic twin pair is presented.

Selective versus non-selective suppression of nitric oxide synthase on regional hemodynamics in rats with or without LPS-induced endotoxemia.

The late phase of severe septic shock is associated with reduced cardiac output (CO) and activation of the inducible isoform of nitric oxide synthase (NOS). This study examined the effects of 1400 W (N-3-aminomethyl-benzyl-acetamidine), a new selective inhibitor of inducible NOS (iNOS), relative to those of N(G)-nitro-L-arginine (L-NNA, non-selective inhibitor of NOS) and the vehicle, on mean arterial pressure (MAP), CO, total peripheral resistance (TPR) and tissue blood flow (BF) in thiobutabarbital-anesthetized rats with lipopolysaccharide (LPS, 10 mg/kg, i.v.) induced endotoxemia. At 2.5 as well as 4 h after injection of LPS, MAP, CO, and BF of the stomach, skeletal muscle and skin were decreased, but TPR was increased, BF to the heart and kidneys were also decreased at 4 h after injection of LPS. Treatment of endotoxemic rats with 1400 W (3 mg/kg followed by 3 mg/kg/h, i.v.) at 2.5 h after endotoxin challenge prevented the late phase fall in MAP without exacerbating the decreases in CO and tissue BF. In contrast, treatment with L-NNA (8 mg/kg followed by 3 mg/kg/h, i.v.) at 2.5 h did not prevent the decline in MAP in the LPS-treated rats. Furthermore, CO drastically decreased, TPR markedly increased, and BF to the heart, brain, intestine and skeletal muscle were decreased at 4 h relative to the readings in saline- or 1400 W-treated endotoxemic rats. Therefore, selective inhibition of iNOS by 1400 W restores MAP without compromising CO, but non-selective inhibition of NOS is detrimental at the late stage of septic shock.