Musculoskeletal: bones, soft tissues and inflammation

The diagnosis of infections is based on the presence of clinical symptoms like erythema, swelling and pain. Also, the diagnosis is based on the presence of clinical signs such as fever, tachycardia and shock and laboratory test such as leukocytosis and C protein reactive. However, the clinical symptoms and signs of infection may not be specific, especially in the early stages of the disease. In these cases, Imaging tests play a fundamental role in the early diagnosis of infections and the differential diagnosis. The most important radiological findings for inflammatory and infections soft tissue are: 1/ Intramuscular fluid collections. 2/ Soft tissue air. 3/ Fascial fluid collections and 4/Muscle oedema. Potential causes of these radiological findings are diverse, including, infectious, autoimmune, inflammatory, neoplastic, neurologic, traumatic and iatrogenic conditions. Some of these conditions require prompt medical or surgical management, whereas others do not benefit from medical intervention. Necrotising fasciitis is a rare, life-threatening soft-tissue infection and a medical and surgical emergency that radiologist must know. The presence of gas within the necrotised fascia is characteristic, but may be lacking. The main finding is thickening of the deep fascia due to fluid accumulation and reactive hyperemia. All these findings may be seen in other different conditions. The ability to accurately diagnose these conditions is therefore necessary. Clues to the correct diagnosis and whether a biopsy is necessary or appropriate are often present on the images techniques, especially when they are correlated with clinical features.

Arthropathies are one of the most common health problems and the leading cause of disability in adults. Imaging plays an essential role in their diagnosis and follow-up. Plain films remain the first line imaging tool in the diagnosis and management of arthropathies, whereas MR imaging is essential to ascertain the presence of active inflammation and disruption of intra- and periarticular structures. This interactive presentation focuses on radiological features of common (and several less common) arthropathies and how they help in narrowing the differential diagnostic considerations.

In this lecture, we’ll focus on imaging osteomyelitis of the appendicular and axial skeleton, and their differential diagnosis using radiographs, US, and especially MRI and PET-CT. Understanding the interaction between invading organisms and intact or compromised host response is essential in the interpretation of imaging features. Major routes of infection include hematogeneous or contiguous routes occurring in respectively pediatric-geriatric, or immunocompromised and diabetic, or post-procedure infections. Location in the metaphysis and vertebral body are hallmarks of hematogenous spread. Location in bones close to skin defects, pressure points, and soft tissue infection are hallmarks of contiguous spread, especially in diabetic foot, intensive care patients, and following surgical or image guided procedures. Knowledge of age and the comorbidity-related relationship between vasculature on one-hand and growth plates and discs, on the other hand, is essential in the diagnosis of infection. Also, imaging features of host response depend on the pressure within anatomical compartments. The most relevant differential diagnostic issues including posttraumatic sequelae, degenerative disease, Charcot foot and spine, sterile inflammatory disease (CRMO, SAPHO), tumours, and also the differentiation between mild and life-threatening infection like necrotising fasciitis will be discussed. The impact of imaging on clinical outcome as it depends on treatment options, cost-effectiveness, predictive values of various imaging studies relative to clinical and laboratory tests, is addressed.

The diagnosis of a bone tumour is based on clinical findings, the age of the patient, the anatomic location of the lesion, its radiologic appearance, and if imaging does not allow for a specific diagnosis, its histopathologic features. Radiography remains the initial imaging modality for evaluation of the location of the lesion with respect to the longitudinal and axial planes of the involved bone, for estimation of its biologic activity by analysing the patterns of bone destruction and periosteal response, and for the depiction of matrix mineralisation. CT is typically used to obtain “radiographic” information in regions of complex skeletal anatomy such as the skull, spine, pelvis and shoulder girdle. MR imaging is best suited to determine the local extent of a bone tumour (local staging), but can also be helpful to narrow the differential diagnosis in specific lesions such as cysts and cartilage-forming tumours. With a clear emphasis on conventional radiography, this course will review the basic imaging features of the most common benign and malignant bone tumours. Important radiographic findings, such as bone destruction patterns, types of periosteal reactions and matrix mineralisation, will be explained step by step in correlation with histopathology as well as advanced imaging techniques.

Bone marrow consists of trabecular bone, a stroma of connective tissue, hematopoietic cells (red marrow) and fat (yellow marrow). Distribution of red and yellow marrow is age-dependent, with gradual conversion of red to yellow marrow in the limbs during childhood, and patchy heterogeneity in the spine in the elderly patient. There are many causes of reconversion from yellow to red bone marrow, like smoking, long distance running, obesity, anaemia, erythropoietin, etc. Depletion may occur in aplastic anaemia and after radiation therapy. Gelatinous transformation is seen in anorexia nervosa, cachexia, HIV and after successful therapy in multiple myeloma. Bone infarction and avascular necrosis are well-delineated areas of dead bone marrow. The value of different imaging techniques, including plain radiography, (dual-energy)-CT, bone scintigraphy, PET and the most sensitive technique, MRI (conventional T1, T2, fat suppression techniques, in-phase, out-phase and diffusion imaging), will be explained. The imaging characteristics of many diseases will be reviewed (diffuse bone marrow replacement in hematologic diseases, multiple myeloma, metastases; treatment-related changes of bone marrow, primary bone tumors, and multiple causes of bone marrow edema, like bone contusion, stress fracture, insufficiency fracture, Modic changes, spondylodiscitis, osteomyelitis, abscess, arthritis and specific bone tumors).

All imaging modalities can play a role in the diagnosis and management of soft tissue tumours and pseudotumours with a variable contributory performance to both sensitivity and specificity. MRI steals the show with an unparalleled role in soft tissue assessment ranging from detection, localisation, characterisation, identifying multiple lesions, other syndrome stigmata, the probability of benignity/malignancy, local staging and recurrence identification. Sonography does have a supporting role especially in the initial assessment of the likelihood of cystic/benign/abnormal malignant Colour Doppler flow patterns. This presentation aims to provide a distillation of the knowledge regarding soft tissue tumour imaging which can be applied in practice using a stepwise analytical approach. Despite an overwhelming spectrum of potential histological diagnosis, the radiologist needs to remember that eight benign and six malignant lesions account for 80% of all soft tissue tumours.

Bone sarcomas are rare (0.2% of all neoplasms, annual incidence in Europe is 0.8 per 100.000 population), in contrast to benign bone tumours and the so-called tumour-like lesions. The incidence of these benign entities is relatively high, but not known exactly as these are often asymptomatic. The WHO (version 2013) classified benign and malignant bone tumours in 13 main categories; chondrogenic, osteogenic, fibrogenic, fibrohistiocytic, hematopoietic, osteoclastic giant cell rich, notochordal, vascular, myogenic, lipogenic, undefined neoplastic nature and miscellaneous tumours. Each category is further subdivided into 1-14 tumour types. Imaging plays an important role in diagnosis, monitoring therapy, staging, and detecting recurrent disease. Diagnosis is mainly based on conventional radiography using morphologic appearance in combination with location, and age. Advanced imaging techniques are used for local staging (MR), detection of metastases (chest CT), monitoring therapy (MR, ultra-sound, PET-CT), detecting recurrence (MR, ultra-sound, PET-CT). Typical imaging features based on the WHO classification system will be presented with a focus on conventional radiography, common tumours, and relevance.