CT scan knee is a method of radiation diagnostics aimed at visualizing the structures forming the knee joint. It allows you to examine the patella, the distal part of the femur, the proximal parts of the tibia and fibula, to assess the overall configuration of the joint and the state of regional vessels (with contrast). CT is used in the diagnosis of bone fractures, dislocations, subluxations, degenerative and dystrophic joint lesions, benign and malignant neoplasms, osteoporosis, hemorrhages. It is usually carried out without contrasting, contrast enhancement is used less often.
Indications for CT scan knee are clinical manifestations of pathological changes in the joint itself or adjacent structures. The list of indications includes a pain syndrome of various nature that occurs at the beginning, during walking or at rest, a decrease in the amplitude of movements in the joint, morning stiffness, an increase in the volume of the joint, hyperemia, local fever, swelling of surrounding tissues, the occurrence of neoplasms. CT is necessary for severe knee injuries, especially with the appearance of pathological mobility or crunch, a change in the configuration of the joint, sharp pain during movements or axial load, indicating bone fracture, dislocations and subluxations, as well as suspected penetration of a foreign body.
Joint tomography is prescribed in the process of monitoring the patient’s condition with X-ray negative fractures, arthrosis, arthritis, hemarthrosis, suspected metastases. Intravenous contrast during this procedure allows you to visualize regional vessels, which is necessary for the differential diagnosis of malignant and benign neoplasms, the detection of thromboembolism or ruptures of the main vessels. Also, the scan is carried out at the stage of preparation for surgery, to assess the results of surgical or conservative treatment.
CT scan knee is contraindicated in patients in critical condition or with unstable hemodynamics, since during the study the possibility of constant monitoring and immediate assistance is lost. The procedure is not prescribed to pregnant women (especially in the first half of gestation) due to the negative effect of X-rays on the fetus. This study is not recommended for younger children, persons with mental disorders, phobias or severe pain syndrome, as they are unable to maintain a stationary position throughout the procedure. Severe obesity prevents CT, since most modern tomographs are designed for a patient’s body weight of no more than 120-140 kg.
Intravenous contrast is contraindicated in patients with individual intolerance to iodine or radiopaque substances due to the possible development of anaphylactic shock. The procedure is not prescribed to patients with renal and hepatic insufficiency, since contrast agents are metabolized and excreted by the liver and kidneys. It is forbidden to introduce contrast to persons suffering from myeloma, diabetes mellitus, iodine-dependent thyroid diseases.
Specific preparation for the native procedure is not required. Before contrast administration, preparation is necessary, including an allergy test for sensitivity to the injected drug, assessment of excretory kidney function (creatinine, urea, GFR) and liver condition (hepatic transaminases, bilirubin). 4-6 hours before the radiopaque CT scan, you should refuse to eat.
Immediately before the start of the study, the patient talks with the radiology doctor, receives a brief briefing. The specialist clarifies the anamnesis: previously performed surgical interventions on the knee, present diseases, the presence of metal structures (screws, spokes, plates) in adjacent areas. This is necessary to identify changes in the images obtained during CT scan knee. Next, the patient goes to the locker room, takes off all metal objects and changes into a special robe. These conditions allow you to avoid the “layering” of foreign objects in the pictures.
Methodology of conducting
Most tomographs visually represent a massive ring with a horizontal couch located in the hole. The patient lies down on the table of the device, and the doctor moves the examined area inside the scanner. Next, a CT scan is performed. If contrast enhancement is necessary, a series of images can be taken, after which a radiopaque preparation is introduced and an extended study is carried out.
Native scanning takes several minutes, during which it is necessary to lie still, since any movement can cause distortion of the tomogram. Contrast-free CT does not cause somatic sensations. Contrast enhancement may be accompanied by mild weakness, malaise or nausea. During the shooting, CT scanners emit soft clicks. Complications or adverse reactions do not occur with proper preparation. Compliance with any restrictions after this procedure is not required.
Interpretation of results
The result of a CT scan knee, depending on the institution, can be prepared from several hours to a day. As a rule, it includes a film with the obtained images, a CD with a recording of the scan, a written opinion of a radiologist. Some clinics may send the results by e-mail. According to CT data, the following pathological changes can be detected:
- violation of the structural integrity of bones (a sign of fracture)
- displacement of articular surfaces relative to each other (manifestations of complete or incomplete dislocation)
- deformity and/or narrowing of the articular gap, osteoporosis (symptoms of deforming osteoarthritis, rheumatic polyarthritis)
- neoplasms with or without neovascularization (malignant or benign tumors)
- the presence of blood in the synovial fluid corresponds to hemarthrosis, pus – abscess
- vessel “breakage” (indicates embolism or rupture)