X-ray symptoms and syndromes of skeletal lesions

Pathological processes developing in the musculoskeletal system lead to various and very polymorphic radiographic manifestations. On the one hand, the same diseases, depending on the individual characteristics of the patient and the stage of the disease, can cause various symptoms, and on the other hand, pathological conditions that are opposite in nature and prognosis are sometimes accompanied by very similar changes. In this regard, radiographic data should be assessed only taking into account the clinical picture and laboratory test results. It should also be borne in mind that an X-ray image that displays only the mineralized bone base may be normal in cases of soft tissue lesions of the musculoskeletal system. As a result, a latent ("radio-negative") period is distinguished in the course of many diseases. Such patients need to undergo other radiation studies - CT, MRI, sonography, osteoscintigraphy.

The main deviations from the norm observed during radiological examination can be grouped as follows:

1. changes in the position, shape and size of bones;
2. changes in the surface of bones (their contours on radiographs);
3. changes in bone structure:
   • violation of the integrity of the bone beams;
   • restructuring of bone structure;
   • osteolysis and osteonecrosis;
   • destruction and sequestration of bone tissue;
4. changes in the X-ray joint space.

The first group of signs requires almost no explanation. Changes in the position of the bones can be both a developmental anomaly and a consequence of fractures and dislocations. A change in the normal shape of the bone occurs with developmental anomalies or occurs as a result of a decrease in bone strength (with vitamin deficiency, bone demineralization, etc.). A change in the size of the bone is caused by its destruction or neoplasm. Thickening of the bone is usually called hyperostosis. It is formed as a result of increased functional load or excessive growth and ossification of the periosteum with circulatory disorders, intoxications, inflammatory lesions. Uniform bone reduction occurs with its underdevelopment or atrophy. The most common cause of atrophy is limitations in the locomotor function of the skeleton and neurodystrophic disorders.

Changes in the outer surface of the bone are observed during destruction of the cortical layer of inflammatory or tumor origin. In addition, there may be protrusions on the bone associated with developmental disorders (exostoses) or an inflammatory process (osteophytes), but most often changes in the contours of the bone are explained by structural shifts in the periosteum.

Normally, the periosteum is not visible on radiographs, but under pathological conditions it often calcifies and ossifies. Depending on the nature of the process (inflammatory or non-inflammatory), it is called periostitis or periostosis. In inflammatory lesions, the periosteum is pushed away from the bone surface by exudate and calcifies. This is the so-called exfoliated periostitis. It looks like a delicate narrow intermittent strip located at some distance from the bone contour. Then the mass of calcified periosteum increases and it sometimes takes on the appearance of a fringe from a curtain ("fringed" or "lace" periostitis). In bone tumors - sarcomas - ossification of the periosteum is observed, pushed away from the edges of the neoplasm - periostitis in the form of a visor, as well as ossification along the vessels going from the periosteum to the bone (they are not quite accurately called needle periostitis). Let us add that sonography allows us to detect changes in the volume of the periosteum and accumulations of blood or pus located underneath it during the “radio-negative” period.

Changes in bone structure occur primarily in fractures and are expressed in a break in bone beams and trabeculae: a fracture line or gap appears in the bone, having a different direction and length. In neurodystrophic lesions, bone tissue resorption may be observed, in which an irregularly shaped defect of bone substance with blurred boundaries is detected on images. Osteonecrosis develops in bone nutrition disorders. The necrotic area appears denser against the background of the surrounding bone. Bone beams in the area of necrosis cannot withstand the usual load and are compressed, which leads to bone deformation and an even greater increase in the intensity of its shadow.

In a number of diseases, destruction occurs - the destruction of bone beams and entire sections of bone and their replacement with pus, granulation or tumor tissue. On an X-ray, the site of destruction looks like a bone defect. The contours of fresh destructive foci are uneven, while the edges of long-existing foci become smooth and compacted. Destruction often leads to the rejection of bone fragments and their necrosis. Such freely lying and necrotic pieces of bone are called sequesters.

Of great importance in X-ray diagnostics is the symptom of bone structure reorganization. Bone reorganization is any change in bone structure accompanied by the appearance of a new structure in place of the previous one. A distinction is made between physiological and pathological reorganization. Physiological reorganization includes all types of bone structure changes that occur during normal human activity under the influence of certain working and living conditions, sports. Such reorganization occurs in the bone system of a healthy person throughout life. It is characterized by a balance between the processes of bone formation and resorption. Pathological reorganization can occur as a result of dystrophic, inflammatory and other processes and is usually accompanied by a predominance of resorption processes or new formation of bone elements.

The most frequently observed type of remodeling is osteoporosis (bone rarefaction). It is expressed in a uniform decrease in the number of bone beams per unit volume of bone. On radiographs, osteoporosis is manifested by increased transparency of the bone, thinning of the cortical layer and widening of the medullary canal, accentuation of the contours of the cortical layer around the entire bone. In the spongy substance of the epiphyses, metaphyses and in flat bones, a large-mesh bone structure is observed. Osteoporosis can be spotty and manifest itself in the form of separate small or larger areas of enlightenment or be diffuse and uniform. By extent, there are 4 forms of osteoporosis: local, regional, widespread and systemic. Local osteoporosis is a limited area of rarefaction of the bone structure: usually this is the initial manifestation of bone destruction. Regional osteoporosis is osteoporosis that affects an entire anatomical area. As a rule, rarefaction of the bone structure is determined in the articular ends of bones in arthritis. Osteoporosis is considered widespread when it affects all the bones of one limb, which is usually associated with a circulatory or innervation disorder of that limb. Systemic osteoporosis affects the entire skeleton.

Osteosclerosis is a change in bone structure in which an increase in the amount of bone substance per unit of bone volume is observed. In the spongy substance, a finely looped structure is determined, up to one in which the bone pattern is indistinguishable. In long bones, thickening of the cortical layer and narrowing of the medullary canal are observed.

Osteosclerosis can be limited or systemic. The latter form is observed relatively rarely: in some congenital diseases (marble disease), poisoning with fluorine compounds (fluorosis). Multiple areas of osteosclerosis in bones are detected in heavy metal intoxication, some types of leukemia, deforming osteodystrophy, renal osteodystrophy, osteoblastic metastases of cancer.

A peculiar type of remodeling are the so-called Looser remodeling zones. They develop in cases where normal bone is subjected to excessive load or physiological load is applied to pathologically changed bone (for example, in case of vitamin deficiency). In this case, acute aseptic necrosis occurs in the area of overload. Most often, it manifests itself as a transverse or oblique band of enlightenment in the bone, in which the bone beams are no longer visible. If the load is stopped and immobilization is carried out, then due to the activity of the periosteum and endosteum, a semblance of bone callus is formed and a new structure is formed that can withstand increased load. Otherwise, a real fracture ("stress fracture") may occur.

A change in the X-ray joint space is a sign of joint damage. Uniform narrowing of the joint space most often indicates a degenerative state of the articular cartilage. Uneven narrowing is observed in arthritis and can be combined with the destruction of the end plates and the subchondral layer of the articulating bones. In fibrous ankylosis, the disappearance of the end bone plate is determined, and in bone ankylosis, the transition of bone beams from one epiphysis to another.

The above are far from all the radiographic symptoms of skeletal injuries and diseases, but it is clear from the above how many diverse and non-standard combinations of them can be observed in reality. Although the X-ray image of the bone seems demonstrative and understandable, for accurate recognition of its lesions, the doctor needs good general clinical training and a pedantic analysis of radiation semiotics.