Faculty Bibliography

Ischiofemoral impingement is a syndrome defined by hip pain associated with narrowing of the space between ischial tuberosity and lesser trochanter. This phenomenon leads to abnormalities of the quadratus femoris muscle, ranging from deformity and edema to tears and atrophy. This review article presents an up-to-date discussion and imaging findings of ischiofemoral impingement, along with its related anatomy, clinical presentation, differential diagnosis and treatment.

Femoroacetabular impingement (FAI) is a common cause of early-onset osteoarthritis of the hip. It can be caused by morphologic abnormalities involving the proximal femur or acetabulum, leading to abnormal abutment of the femoral head-neck against the acetabular rim. This repetitive trauma causes mechanical wear of the labrum and articular cartilage, leading to osteoarthritis of the hip. Magnetic resonance imaging is an accurate noninvasive imaging modality that can detect acetabular labral lesions and adjacent cartilage damage, and is able to detect underlying subtle anatomic variations of the femoral head-neck junction and acetabulum associated with FAI.

BACKGROUND:Vitamin D insufficiency and higher testosterone are common in obese girls and may adversely affect glucose homeostasis and cardiovascular risk. Data are conflicting regarding the impact of parathyroid hormone (PTH) on these factors. Our objective was to determine associations of 25-hydroxyvitamin D (25-OHD), PTH, and testosterone with measures of glucose homeostasis and cardiovascular risk in adolescent girls after controlling for regional adiposity, with the hypothesis that lower 25-OHD, a higher PTH or PTH/25-OHD ratio, and higher testosterone would be associated with lower insulin sensitivity and greater cardiovascular risk. METHODS:A total of 15 obese girls and 15 matched normal weight controls (12-18 years) underwent fasting measurements of 25-OHD, PTH, testosterone, sex hormone-binding globulin (SHBG), high-sensitivity C-reactive protein (hsCRP), oral glucose tolerance testing, and quantification of visceral (VAT) and subcutaneous (SAT) fat by magnetic resonance imaging (MRI). RESULTS:There were no associations of 25-OHD with measures of glucose homeostasis or hsCRP. In contrast, PTH and PTH/25-OHD were associated negatively with homeostasis model assessment of insulin resistance (HOMA-IR) and positively with quantitative insulin sensitivity check index (QUICKI) in obese girls but not controls. These associations remained significant after controlling for body mass index standard deviation score (BMI-SDS), but not for VAT. On regression modeling, PTH/25-OHD was positively associated with hsCRP after controlling for BMI-SDS or VAT. Free testosterone positively predicted the corrected insulin response. CONCLUSIONS:In obese girls, PTH/25-OHD is positively associated with measures of insulin sensitivity and hsCRP. Further studies are needed to investigate the relationship between PTH and glucose homeostasis in obesity.

CONTEXT/BACKGROUND:The elbow is a complex joint and commonly injured in athletes. Evaluation of the elbow by magnetic resonance imaging (MRI) is an important adjunct to the physical examination. To facilitate accurate diagnosis, a concise structured approach to evaluation of the elbow by MRI is presented. EVIDENCE ACQUISITION/METHODS:A PubMed search was performed using the terms elbow and MR imaging. No limits were set on the range of years searched. Articles were reviewed for relevance with an emphasis of the MRI appearance of normal anatomy and common pathology of the elbow. RESULTS:The spectrum of common elbow disorders varies from obvious acute fractures to chronic overuse injuries whose imaging manifestations can be subtle. MRI evaluation should include bones; lateral, medial, anterior, and posterior muscle groups; the ulnar and radial collateral ligaments; as well as nerves, synovium, and bursae. Special attention should be paid to the valgus extension overload syndrome and the MRI appearance of associated injuries when evaluating throwing athletes. CONCLUSION/CONCLUSIONS:MRI evaluation of the elbow should follow a structured approach to facilitate thoroughness, accuracy, and speed. Such an approach should cover bone, cartilage, muscle, tendons, ligaments, synovium, bursae, and nerves.

OBJECTIVE:The objective of this study was to determine the prevalence of extrinsic wrist ligament injury by magnetic resonance imaging and its association with intrinsic ligament tears. METHODS:We reviewed conventional magnetic resonance images performed over a 5-year period from adult patients in the setting of wrist trauma. Two musculoskeletal radiologists examined the integrity of wrist ligaments and presence of bone abnormalities. RESULTS:In a cohort of 75 subjects, extrinsic ligament injury was present in 75%, with radiolunotriquetral being most frequently affected (45%). Intrinsic ligament injury was present in 60%. Almost half of subjects had combined intrinsic and extrinsic ligament injury. Bone abnormalities were seen in 69%. The rate of extrinsic injury was higher in subjects with bone injury (P = 0.008). CONCLUSIONS:There is high prevalence of extrinsic ligament injury in the setting of wrist trauma, especially in the presence of bone abnormalities, with combined injury of intrinsic and extrinsic ligaments in about half of cases.

BACKGROUND:HIV lipodystrophy - characterized by peripheral lipoatrophy, with or without central fat accumulation - confers increased metabolic risk. However, the functional activity of HIV lipodystrophic tissue in relation to metabolic risk has yet to be fully explored in vivo through the use of non-invasive imaging techniques. This study assesses the relationship between FDG uptake in various fat depots and metabolic/immune parameters among subjects with HIV lipodystrophy. METHODS:Lipodystrophic men on antiretroviral therapy underwent whole-body (18)F-fluorodeoxyglucose positron emission tomography (FDG-PET)/computed tomography scans and detailed metabolic/immune phenotyping. RESULTS:FDG uptake in the subcutaneous adipose tissue (SAT) of the extremities (mean standardized uptake value [SUV] of the arm and leg SAT) was found to correlate with the degree of peripheral lipoatrophy (r=0.7; P=0.01). Extremity SAT FDG uptake was positively associated with homeostasis model assessment of insulin resistance (HOMA-IR; r=0.6; P=0.02) and fasting hyperinsulinaemia (r=0.7; P=0.01), while fat percentage of extremities was not. Furthermore, extremity SAT FDG uptake was significantly associated with CD4(+) T-cell count (r=0.6; P=0.05). In multivariate modelling for HOMA-IR, extremity SAT FDG uptake remained significant after controlling for body mass index and tumour necrosis factor-α (R(2) for model =0.71, P=0.02; SUV in the extremity SAT β-estimate 12.3, P=0.009). CONCLUSIONS:In HIV lipodystrophic patients, extremity SAT FDG uptake is increased in association with reduced extremity fat and may contribute to insulin resistance. Non-invasive assessments of in situ inflammation using FDG-PET may usefully complement histological and gene expression analyses of metabolic dysregulation in peripheral fat among HIV-positive patients.

INTRODUCTION/BACKGROUND:The purpose of this study was to report the MRI findings that can be encountered in successfully treated bacterial septic arthritis. MATERIALS AND METHODS/METHODS:The study included 12 patients (8 male and 4 female; mean age 38 years, range 9-85) with 13 proven cases of bacterial septic arthritis. The joints involved were hip (n = 3), knee (n = 3), shoulder (n = 2), sacroiliac (n = 2), ankle (n = 1), wrist (n = 1), and elbow (n = 1). MRI examinations following surgical debridement and at initiation of antibiotic therapy and after successful treatment were compared for changes in effusion, synovium, bone, and periarticular soft tissues. Imaging findings were correlated with microbiological and clinical findings. RESULTS:Joint effusions were present in all joints at baseline and regressed significantly at follow-up MRI (p = 0.001). Abscesses were present in 5 cases (38 %), and their sizes decreased significantly at follow-up (p = 0.001). Synovial enhancement and thickening were observed in all joints at both baseline and follow-up MRI. Myositis/cellulitis was present in 10 cases (77 %) at baseline and in 8 cases (62 %) at follow-up MRI. Bone marrow edema was present in 10 joints (77 %) at baseline and persisted in 8 joints (62 %). Bone erosions were found in 8 joints (62 %) and persisted at follow-up MRI in all cases. CONCLUSION/CONCLUSIONS:The sizes of joint effusions and abscesses appear to be the factors with the most potential for monitoring therapy for septic arthritis, since both decreased significantly following successful treatment. Synovial thickening and enhancement, periarticular myositis/cellulitis, and bone marrow edema can persist even after resolution of the infection.

CONTEXT/BACKGROUND:Recent studies have suggested that obesity in men is associated with increased fracture risk. Obesity in men is also associated with dysregulation of the GH/IGF-I and gonadal steroid axes, important regulators of bone homeostasis. OBJECTIVE:The aim of the study was to investigate body composition and endocrine determinants of bone microarchitecture and mechanical properties in obese men. DESIGN AND SETTING/METHODS:We conducted a cross-sectional study at a clinical research center. PARTICIPANTS/METHODS:Thirty-five obese men (mean age, 33.8 ± 6.4 yr; mean body mass index, 36.5 ± 5.8 kg/m(2)) participated in the study. OUTCOME MEASURES/METHODS:Distal radius microarchitecture and mechanical properties were measured by three-dimensional high-resolution peripheral quantitative computed tomography and microfinite element analysis; body composition by computed tomography; bone marrow fat by proton magnetic resonance spectroscopy; total and free estradiol and testosterone; IGF-I; peak glucagon-stimulated GH; 25-hydroxyvitamin D. RESULTS:Men with high visceral adipose tissue (VAT) had impaired mechanical properties compared to men with low VAT (P < 0.05), despite comparable body mass index. VAT was inversely associated and thigh muscle was positively associated with mechanical properties (P < 0.05). Bone marrow fat was inversely associated with cortical parameters (P ≤ 0.02). Free estradiol was positively associated with total density (P = 0.05). Free testosterone was positively associated with trabecular thickness and inversely with trabecular number (P ≤ 0.05). Peak stimulated GH was positively associated with trabecular thickness, as was IGF-I with cortical area (P ≤ 0.04). CONCLUSION/CONCLUSIONS:VAT and bone marrow fat are negative predictors and muscle mass is a positive predictor of microarchitecture and mechanical properties in obese men. Testosterone, estradiol, and GH are positive determinants of trabecular microarchitecture, and IGF-I is a positive determinant of cortical microarchitecture. This supports the notion that VAT is detrimental to bone and that decreased GH and testosterone, characteristic of male obesity, may exert deleterious effects on microarchitecture, whereas higher estradiol may be protective.

OBJECTIVE:Enchondromas are benign lesions that may present with nonspecific features on imaging in children. Correlation of histology with imaging findings is often required to make the final diagnosis of a benign lesion. The aim of this study was to review imaging and pathological findings of enchondromas in children. MATERIALS AND METHODS/METHODS:Imaging examinations of 12 enchondromas in 11 patients (median age 14 years) were retrospectively reviewed. Imaging evaluation included an assessment of lesion size, relationship to the growth plate, mineralization, matrix and periosteal reaction, intrinsic MR signal characteristics, and intraosseous and soft-tissue edema. Pathological findings were reviewed. RESULTS:Lesions were located in the phalanx in 33% (4 out of 12), metacarpal in 25% (3 out of 12), femur in 33% (4 out of 12) and tibia in 8% cases (1 out of 12). The mean size was 28 mm (range, 11-70 mm). Matrix mineralization in a typical "rings-and-arcs" pattern was observed in 20% of the lesions with available radiographs/CT (2 out of 10). Lesions were expansive with endosteal scalloping in 75% of cases (9 out 12) and contacted the growth plate in 50% of cases (6 out of 12). All enchondromas in which MR imaging was available (5 out of 5) demonstrated typical cartilaginous matrix of lobules of high T2 signal, low T1 signal, and peripheral enhancement. CONCLUSION/CONCLUSIONS:Enchondromas in children are relatively large lesions, with frequent endosteal scalloping and rare matrix mineralization.