XI. Radiographic diagnosis of the musculoskeletal system

About 40% of the work load of a general radiology department relates to the examination of bones and joints. The most common indication for such examinations is a traumatic or degenerative disease of the bones and joints.

Bones

Methods of examination

Plain radiograph: Usually bi-directional, and visualizes the bone structures in fine detail, especially with a high-resolution (fine) screen or without intensifying screen.
Conventional tomography: This is used to visualize the parts that are usually obscured in a summation radiograph (ex. sacroiliac joint and sternum).
Bone scintigraphy: This is suitable for visualization of the entire skeleton; an increase in uptake indicates an increased osteoblast activity (some osteolytic processes are not necessarily visualized!).
Bone densitometry (DEXA): This serves to measure the mineral content of bone.
Computer tomography (CT): This is used to produce slice scans from which scans in other planes can be reconstructed. This visualizes the changes in the bones and surrounding soft tissues.
Magnetic resonance (MRI): The bones themselves are poorly visualized, but this is the most suitable method for clarification of the status of the bone-marrow and soft tissues: the muscles, tendons, ligaments, cartilage, fat and fluid are differentiated from one another with high certainty and accuracy.

Basic changes in the bones

Osteoporosis: A decrease in the calcium content of the bone, with concurrent consumption of the organic matrix.
Osteomalacia: A decrease in the calcium content, without a change in the organic matrix of the bone, resulting in softening of the bone.
Osteosclerosis: A focal or isolated increase in the calcium content of the bone.
Osteolysis: Following an increase in the osteoclast activity, the bone matrix is absorbed.
Osteonecrosis: Following a nutritional defect, the bone tissue dies, the macrophages clear the inorganic matrix, and calcium is laid down in unstructured isolated islands.
Osteodysplasia: The original lamellar bone structure heals and is replaced by a braided-cystic structure.

Diseases and their radiographic examination

Developmental anomalies (amyelia, phocomyelia, absent extremity, syndactyly, polydactyly, etc.): With radiography, their features and degree of criticalness can be exactly clarified.
Hip dysplasia congenital hip dislocation: These can be demonstrated in the newborn and screened by ultrasound/radiographic examination.
Generalized congenital bone diseases (osteogenesis imperfecta, osteopetrosis, multiplex hereditary exostosis, multiplex enchondromatosis, chondrodysplasia and mucopolysaccharidosis): The radiographic examination itself is diagnostic, or leads to a suspicion of the disease process.
Inflammatory bone diseases (osteomyelitis, Brodie's abscess, panaritium osseale, tuberculosis of the joint space, etc.): The MR examination points to the disease process in an early phase, while radiography is positive only after approximately 2 weeks: first porosis, later osteolysis and then necrosis develop. The dead bone pieces are absorbed, or are enclosed by a surrounding "bone cast". The disease process can be accompanied by joint space inflammation or a cold abscess.
Metabolic bone diseases (rachitis, uremic arthritis and eosinophil granuloma): Radiography reveals a typical picture, but laboratory examinations are necessary to confirm the diagnosis.
Hormonal bone lesions (acromegaly, hyperthyroidism, hyperparathyroidism, Cushing syndrome, etc.): Radiographic examination draws attention to the typical bone lesions, but the diagnosis is based on the laboratory examination results.
Traumatic bone lesions (simple and multiple, open and closed, dislocated and wedged, etc. fractures): The diagnosis of a fracture or assessment of the degree of criticalness and healing is performed by radiographic examination, with the exception of spine, pelvic and skull lesions, where CT/MR examination may be required.
Benign tumors (osteoma, non-ossified bone fibroma, juvenile bone cyst and haemangioma), semi-malignant tumors (osteochondroma and osteoclastoma), malignant bone tumors (osteosarcoma, chondrosarcoma, Ewing sarcoma and myeloma multiplex): The bone tumors are revealed in a radiograph, but their exact spread and relationship with the surrounding tissue are clarified by CT or MR.
Bone metastasis: The presence of invasion is demonstrated by a positive bone scintigraphy scan; differentiation is achieved by radiography/CT/MR examination.

Joints

Methods of examination

Plain bi-directional radiograph: This visualizes the joint spaces and the bones comprising them.
Arthrography: The radiographic films are made after contrast material has been injected into the joint space.
Ultrasound (US): This is suitable for examination of the cartilage and the soft tissues surrounding the joint.
Computer tomography (CT): This serves for examination of the bones and the surrounding soft tissues.
Magnetic resonance imaging (MRI): This is a suitable procedure for visualization of the joint capsule, space, cartilage, ligaments and surrounding soft tissues.

Diseases and their radiographic examination

Inborn anomalies (pes equinovarus, pes valgus convex, etc.): The presence of joint anomalies, their features and extent can be clarified by radiography.
Inflammatory diseases (septic arthritis, tuberculosis, gonorrheal arthritis, viral infections, arthritis of synovial origin, ex. rheumatoid arthritis, ankylosing spondylarthritis, psoriatic arthritis and Reiter syndrome): US and MR are used to show lesions in the soft tissue, the joint space and the surrounding environment; bony lesions are visible in a radiograph.
Degenerative joint diseases (arthrosis deformans and spondylosis deformans): US and MR are used to demonstrate lesions in the soft tissue, the joint space and in the surrounding environment; bony lesions are visible in a radiograph.
Metabolic joint diseases (uremic arthritis, chondrocalcinosis and ochronosis): The typical changes are seen in a radiograph, which, together with the clinical picture, ensures the diagnosis.
Traumatic lesions (sprain, subluxation and luxation): The radiographic examination clarifies the mutual relationship of the bones comprising the joint. Soft tissue injuries can be diagnosed by US/MR examination.
Osteochondritis dissecans: US or MR examination can reveal the cartilage destruction and the broken-off cartilage piece.