Pediatric Foot: Development, Variants, and Related Pathology.

Pediatric foot development throughout childhood and adolescence can present a diagnostic dilemma for radiologists because imaging appearances may be confused with pathology. Understanding pediatric foot development and anatomical variants, such as accessory ossification centers, is essential to interpret musculoskeletal imaging in children correctly, particularly because many of these variants are incidental but others can be symptomatic. We first briefly review foot embryology. After describing common accessory ossification centers of the foot, we explain the different patterns of foot maturation with attention to irregular ossification and bone marrow development. Common pediatric foot variants and pathology are described, such as tarsal coalitions and fifth metatarsal base fractures. We also discuss pediatric foot alignment and various childhood foot alignment deformities.

Dynamic musculoskeletal ultrasound: slipping rib, muscle hernia, snapping hip, and peroneal tendon pathology.

Dynamic musculoskeletal ultrasound is an important diagnostic tool that allows the practitioner to observe soft tissue structures over a range of motion and identify pathology not diagnosed on other modalities. Familiarity with this modality allows health care practitioners to appropriately refer patients for this type of examination. This article will review several indications for dynamic ultrasound imaging, including slipping rib, muscle hernia, snapping hip, and peroneal tendon pathology. The examination technique and expected findings for common pathology in each location are discussed.

Pearls and Pitfalls of Imaging of the Developing Pediatric Skeleton: Differentiating Normal and Pathology With MRI.

Developmental changes occurring in the pediatric skeleton throughout childhood cause imaging appearances that may be confused with pathology. Knowledge of the typical pattern of red to yellow bone marrow conversion and areas of normal developmental irregular ossification is essential for radiologists interpreting musculoskeletal imaging in children to avoid mistaking normal findings for disease. Here we review the normal conversion of hematopoietic to yellow marrow on pediatric MRI and illustrate how MRI can distinguish the normal areas of irregular ossification from various pathology that can occur at and around growth centers in the developing skeleton.

Positron emission tomography/computed tomography imaging appearance of benign and classic "do not touch" osseous lesions.

BACKGROUND: Classic "do not touch" and benign osseous lesions are sometimes detected on 18-F-fluorodeoxyglucose (18F-FDG) positron emission tomography/computed tomography (PET/CT) studies. These lesions are often referred for biopsy because the physician interpreting the PET/CT may not be familiar with the spectrum of 18F-FDG uptake patterns that these lesions display. AIM: To show that "do not touch" and benign osseous lesions can have increased 18F-FDG uptake above blood-pool on PET/CT; therefore, the CT appearance of these lesions should dictate management rather than the standardized uptake values (SUV). METHODS: This retrospective study evaluated 287 independent patients with 287 classic "do not touch" (benign cystic lesions, insufficiency fractures, bone islands, bone infarcts) or benign osseous lesions (hemangiomas, enchondromas, osteochondromas, fibrous dysplasia, Paget's disease, osteomyelitis) who underwent 18F-FDG positron emission tomography/computed tomography (PET/CT) at a tertiary academic healthcare institution between 01/01/2006 and 12/1/2018. The maximum and mean SUV, and the ratio of the maximum SUV to mean blood pool were calculated. Pearson's correlations between lesion size and maximum SUV were calculated. RESULTS: The ranges of the maximum SUV were as follows: For hemangiomas (0.95-2.99), bone infarcts (0.37-3.44), bone islands (0.26-3.29), enchondromas (0.46-2.69), fibrous dysplasia (0.78-18.63), osteochondromas (1.11-2.56), Paget's disease of bone (0.93-5.65), insufficiency fractures (1.06-12.97) and for osteomyelitis (2.57-12.64). The range of the maximum SUV was lowest for osteochondromas (maximum SUV 2.56) and was highest for fibrous dysplasia (maximum SUV of 18.63). There was at least one lesion that demonstrated greater 18F-FDG avidity than the blood pool amongst each lesion type, with the highest maximum SUV ranging from 9.34 times blood pool mean (osteomyelitis) to 1.42 times blood pool mean (hemangiomas). There was no correlation between the maximum SUV and the lesion size except for enchondromas. Larger enchondromas had higher maximum SUV (r = 0.36, P = 0.02). CONCLUSION: The classic "do not touch" lesions and classic benign lesions can be 18F-FDG avid. The CT appearance of these lesions should dictate clinical management rather than the maximum SUV.

Accuracy of CT Attenuation Measurement for Differentiating Treated Osteoblastic Metastases From Enostoses.

OBJECTIVE: The objective of our study was to assess whether the maximum and mean CT attenuations are accurate for differentiating between enostoses and treated sclerotic metastases. MATERIALS AND METHODS: We retrospectively reviewed CT studies of 165 patients (167 lesions) that included 49 patients with 49 benign lesions, 69 patients with 71 sclerotic treated lesions, and 47 patients with 47 untreated lesions, and calculated the mean and maximum CT attenuations of each lesion. ROC curves were used to identify thresholds for differentiating enostoses from treated sclerotic metastases and from untreated sclerotic metastases. RESULTS: The maximum CT attenuation of enostoses (1212.0 HU) was higher from that of untreated (754.7 HU) (p = 9.7 × 10-16) and that of treated (891.7 HU) (p = 9.9 × 10-10) sclerotic metastases. The maximum CT attenuation of treated sclerotic metastases (891.7 HU) was higher than that of untreated sclerotic metastases (754.7 HU) (p = 0.003). Enostoses had higher mean CT attenuation (1123.0 HU) than untreated (602.0 HU) (p < 2.2 × 10-16) and treated (731.7 HU) (p = 9.6 × 10-15) sclerotic metastases. A threshold mean CT attenuation of 885 HU had an accuracy of 91.7% and 81.7% to differentiate enostoses from untreated and treated metastases, respectively, whereas a threshold maximum CT attenuation of 1060.0 HU had an accuracy of 81.3% and 72.5% to differentiate enostoses from untreated and treated metastases. CONCLUSION: The mean and maximum CT attenuations can differentiate between enostoses and sclerotic metastases; however, the accuracy of both metrics decreases after treatment.