External landmarks and preliminary diagnostics
Before referring a patient for instrumental examinations, the physician evaluates characteristic lines and triangles. Changes in these periarticular landmarks directly indicate bone displacement:
- Marx's line: projection of the humeral axis toward the elbow joint.
- Hüeter's landmarks: formed by the medial and lateral epicondyles of the humerus along with the tip of the olecranon. In extension, they align in a straight Hüeter's line, while in flexion they form an isosceles Hüeter's triangle.
- Roser–Nélaton line: connects the anterior superior iliac spine to the ischial tuberosity. When the hip is flexed at a 135° angle, the tip of the greater trochanter normally lies strictly on this axis.
- Schumacher's line: drawn from the tip of the greater trochanter through the anterior superior iliac spine. In a healthy individual, its extension intersects the umbilicus or passes above it. If the line falls below the umbilicus, it signals a proximal femoral fracture with displacement of the trochanter upward.
Radiography as the gold standard
In the vast majority of cases, conventional radiography remains a sufficient and mandatory method for making a definitive diagnosis. To avoid gross medical errors, the examination must follow strict rules:
- Two projections. Images are always taken in mutually perpendicular planes (lateral and anteroposterior). Sometimes special atypical projections or a 45° rotation are required.
- Correct positioning. The investigated segment and the patient must be in a standard position.
- Precise centring. The area of suspected pathology must be in the center of the frame (the physician is personally present or marks the area for the radiologist).
- Inclusion of adjacent joints. When examining long tubular bones, the joints must be captured in the frame. For the lower leg and forearm, imaging both adjacent joints is strictly mandatory.
- Structure evaluation. On a quality radiograph, bone trabeculae and their orientation are always clearly visualized.
For orthopedic surgery planning, skiagraphy is used—tracing the contours of the image to calculate geometric ratios. This helps measure axis deformation angles, joint spaces, and calculate the volume of bone tissue to be excised and the dimensions of future grafts.
X-ray computed tomography (CT)
Computed tomography takes the visualization of bone structures to a new level. The method allows obtaining X-ray images in thin slices (thickness varies from 0.1 to 11 mm). Thanks to powerful graphic workstations, specialists can perform complex overlays and build detailed spatial reconstructions of damaged areas.
Ultrasound and blood flow assessment
Methods that do not use ionizing radiation play an important role in assessing soft tissues and the vascular bed.
Ultrasonography (US) is characterized by mobility, low cost, and the ability to immediately compare the affected joint with the healthy (contralateral) one. In traumatology, ultrasound is indispensable for:
- Studying muscles and tendons (especially the Achilles tendon).
- Detecting joint effusion, popliteal cysts, meniscus and ligament tears.
- Evaluating hip joints in pediatrics (relationship between the femoral head and the acetabulum).
To visualize red blood cell motion ("color flow"), dopplerography is used. In orthopedics, it has an auxiliary role and is primarily needed to rule out arterial stenosis or venous thrombosis.
When a detailed study of blood supply is required, angiography is employed—introducing a contrast agent into vessels via a catheter. The method is complex and carries risks, but it allows visualization of arterial, capillary, and venous phases of blood flow. This is necessary when planning limb-salvage or oncological surgeries, as well as when assessing limb viability and diagnosing avascular necrosis.
Scintigraphy (radioisotope scanning)
Unlike X-ray and CT, scintigraphy shows not anatomy, but tissue metabolic activity. A radiopharmaceutical is administered intravenously to the patient, and its accumulation is recorded by a special camera.
The method has extremely high sensitivity, but low specificity—it easily detects a problem, but cannot always precisely state what caused it.
- Decreased uptake indicates early stages of osteonecrosis.
- Increased uptake is characteristic of fractures, foci of osteomyelitis, and tumors (primary or metastatic).
Scintigraphy is of particular value in occult injuries: it can detect compression fractures and microfractures in osteoporosis even before they become visible on conventional radiographs or tomograms.
Briefly: answers to topical questions
Which anatomical structures of the joint (unlike CT) are the main targets for MRI examination?
The main targets for MRI examination are soft tissues, cartilage, tendons, and menisci, whereas CT is used to evaluate bone tissue.
- Soft tissues—visualization of ligaments and tendons (e.g., the distal biceps brachii tendon).
- Cartilage (Cartilage)—assessment of cartilage damage stages and osteochondral defects.
- Menisci (Menisci)—diagnosis of degenerative and acute meniscal tears (Meniscal tear).
- Bone marrow (Bone marrow)—detection of bone marrow edema (bone marrow edema).
What are the absolute contraindications to MRI in patients with orthopedic implants?
The sources do not provide a specific list of absolute contraindications specifically for orthopedic implants. The following contraindications or limitations to MRI are indicated:
- implanted pacemaker;
- insulin pump;
- middle ear implant system;
- metallic or ferromagnetic foreign bodies, including fragments in organs or near the eyeball;
- cerebral vessel clips;
- ferromagnetic stents.
Modern models of some devices may be MRI-compatible, so their presence does not necessarily preclude the examination.
What modern modifications of tomography (MSCT, CBCT) are used in traumatology and how do they differ from step-and-shoot CT?
Multispiral computed tomography (MSCT) and cone-beam computed tomography (CBCT) are used in traumatology.
- MSCT: is the method of choice for multiple facial skeleton fractures, especially in critically ill children; it allows obtaining a three-dimensional image of anatomical structures. In acute urogenital trauma, MSCT with intravenous contrast and multiplanar reconstruction is the "gold standard".
- CBCT: is used by indication for the diagnosis and treatment planning of facial bone fractures, especially of the middle third of the face.
- Spiral CT: the tube moves along one or several spirals; the examination takes about 1 minute.
- Conventional CT: the examination takes about 10 minutes. Multispiral CT has almost completely replaced single-spiral CT.
The term "step-and-shoot CT" is not used in the sources.
Class and exam questions
Why is an X-ray of the entire leg, including the knee and ankle, performed for a shin fracture?
This is a strict radiological rule: in injuries of the long tubular bones of the forearm or lower leg, examining both adjacent joints is mandatory, as the force of the impact can cause associated injuries at opposite ends of the bone.
Why is skiagraphy needed if a high-quality X-ray image is already available?
Skiagraphy is necessary for precise geometric calculation: it allows the surgeon to measure deformation angles, joint space width, and pre-determine the size of the bone graft before surgery.
How does scintigraphy fundamentally differ from CT?
CT shows structural and anatomical bone changes (with a slice thickness from 0.1 mm), while scintigraphy visualizes the level of metabolic activity, allowing the detection of microfractures or early osteonecrosis before bone tissue destruction occurs.
What else to study on this topic
- Stress radiographs: weight-bearing imaging techniques
- Specific contrast modalities: fistulography and pneumoarthrography
- Diagnostic imaging tactics in avascular osteonecrosis
- Peculiarities of pediatric hip joint imaging
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