Introduction
This topic covers the imaging modalities used to evaluate bones and joints (plain radiography, CT/MDCT, MRI, nuclear bone scanning, ultrasound), how to approach a fracture on imaging, bone healing and its complications, and congenital hip dysplasia.
Imaging methods
- Plain radiography is the first choice; images in at least two projections. A fracture line is a radiolucent shadow with sharp contours. Plain films and CT study the cortical and trabecular bone.
- CT and MDCT are the leading techniques for polytrauma and for assessment of the bones of the entire skeleton.
- MRI images soft tissue (cartilage, ligaments, tendons, muscles and bone marrow) and assesses traumatic changes in joints: lesions of ligaments and tendons.
- Nuclear bone scanning gives more information about physiology and less about anatomy.
- How: a material readily taken up by actively growing bone is injected; it carries a radioactive pharmaceutical that decays, forming gamma rays that are detected by gamma cameras.
- Actively growing bone (healing fracture, tumours, after infection) takes up more radiopharmaceutical and shows as a hot area.
- Ultrasound evaluates soft tissues and joints; it is non-ionizing and is used in hip dysplasia in infants.
Three-step assessment of bone and soft-tissue injury
- Assess soft-tissue swelling and joint effusion, as they displace the intra-articular fat pads.
- Examine the cortex along the whole length of the bone.
- Look for contour abnormalities (buckling, impaction or irregularity).
Describing a fracture
- Evaluate whether the fracture extends completely.
- Course of the fracture line: transverse, oblique, longitudinal or spiral.
- Assess any displacement or angulation of the distal fracture fragments. Comminuted: more than 2 pieces of bone or more than 1 fracture line.
- See whether the fracture extends to the joint, and report it so that alignment of the articular surface can be restored.
- See whether it is an open fracture (exposed to air).
The notes list 5 categories of bone injury: separation (separation of the bone), metaphyseal (pieces from below the epiphysis), epiphyseal (pieces from the epiphysis), metaphyseal and epiphyseal, and compression (compression of the bones).