Adventures in Medical School
Pelvic fracture may lead to hemorrhage from arterial, venous, or osseous sources. On CT this may present as hematoma (left arrow) or hemoperitoneum. Initial stabilization of the pelvic fracture, usually with external fixation, is needed. Treatment of these vascular injuries can be attempted with surgical exploration but more commonly angiographic embolization (right arrow) is used.
Pelvic fracture occurs during high-impact injury and can be rapidly fatal if not adequately treated. The complications of pelvic fracture include vascular injury with hemorrhage and bladder injury with extravasation of urine. The pelvis is a ring structure and, therefore, if 1 fracture is identified, then at least 1 additional fracture must be present. Given the complex anatomy of the pelvis, CT with multiplanar reformatting is usually indicated. This three-dimensional CT reformat demonstrates left acetabular (yellow arrow), sacral (red arrow), and pubic (blue arrow) fractures with displacement of the bladder to the right due to pelvic swelling and hematoma.
This series of CT scans demonstrates epidural gas in the cervical region (arrows). The gas entered the epidural space via a severe thoracic spinal fracture. Violation of the epidural space places the patient at increased risk for neurologic complications from infection.
The human heart on chest X-ray
Primary and metastatic cancer to the bones may be evident on chest radiographs. Boney lesions may be sclerotic or lytic and can give clues as to the etiology. Common malignancies giving rise to sclerotic metastasis are prostate cancer, breast cancer, and lymphoma, while common malignancies giving rise to lytic metastasis are renal cell cancer, multiple myeloma, and thyroid cancer. The image shown is from a chest radiograph and reveals a permeative mixed lytic and sclerotic process in the left clavicle (arrow) secondary to malignant lymphoma.
Osteomyelitis is an infection of the bone and bone marrow. It may be easily missed on chest radiographs if one does not pay careful attention to the bones in addition to the lung fields. Typical findings of acute osteomyelitis on plain radiographs are soft tissue swelling, periosteal reaction, cortical irregularity, and demineralization. In chronic osteomyelitis, there is thick, irregular, sclerotic bone with radiolucencies and an elevated periosteum. The image shown is from a patient with chronic osteomyelitis of the left clavicle with bony expansion, sclerosis, and periosteal reaction (arrow). Note the size difference compared to the right clavicle.
Facet joints are formed by the overlapping of the projections from the lamina. The upper projection of one lamina (superior articular process) is overlapped by the lower projection (inferior articular process) of the adjacent vertebra, and together form the facet join. There is a facet joint on each side of the spine at every level.
Compression fractures of the thoracic spine occur whenever the spinal column is subjected to forces that exceed its strength and stability. They may be first detected on chest radiographs by carefully evaluating the vertebral bodies. Typical findings on a plain radiograph for anterior compression fractures include cortical impaction, loss of vertical height, buckling of the anterior cortex, trabecular compaction, and endplate fracture. Lateral radiographs may provide better views of the spinal architecture. The image shown demonstrates kyphosis of the thoracic spine with an osteoporotic fracture of the T8 vertebral body (arrow).
X-ray of a patient’s spine with scoliosis
Metacarpal fractures
The oblique radiograph shown demonstrates fourth and fifth metacarpal fractures. Most dislocations can be evaluated with physical examination only. Images must be obtained in multiple planes and hand positions to ensure no subtle fractures are missed. Commonly obtained views include posterior-anterior, lateral, oblique, Roberts (best for first metacarpal base), Brewerton (best for metacarpal heads), and clenched fist. CT is reserved for detailed evaluation of intra-articular injuries.
Woven bone is the primitive bone first laid down during fracture repair or new bone formation. It consists of a higher percentage of osteocytes than normal. The gross structure is highly disorganized and thus much weaker. It is eventually replaced by concentrically organized lamellar bone with much lower proportions of osteocytes. The histology slide shown demonstrates woven bone arising directly from surrounding mesenchymal tissue.
Boney remodeling is a chronic process of replacement with minimal change in the gross shape of the bone structure. Osteoblasts and osteoclasts together are referred to as bone remodeling units. They work in concert together, coordinated via paracrine signaling by the osteoblasts. The constant remodeling allows for calcium homeostasis and the repair of microscopic daily stressors. The histology slide show demonstrates bone remodeling with osteoclasts resorbing one side of a bony trabecula and osteoblasts depositing new bone on the other side.
Bone scans are not used to measure bone mineral density, but may be useful in the detection of insufficiency fractures in patients with osteoporosis. The patient shown has insufficiency fractures of the sacrum and the pubic rami in a characteristic H, or Honda, sign (arrows), which appears as intense radiopharmaceutical uptake at the fracture sites.
