**1. Introduction**

96 12 Chapters on Nuclear Medicine

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Nuclear medicine supplies with functional perspective in the diagnosis of different pathologies of the musculoskeletal system. Bone scintigraphy is one of the most used nuclear medicine techniques in our clinical practice for location, evaluation and diagnosis of these pathologies because of its high sensitivity. This technique identifies functional changes before structural lesions have been established. For the study of musculoskeletal disorders, the usage of three-phase bone scintigraphy is applied more often than conventional bone scintigraphy. However, due to its low specificity, it has been replaced by other techniques such as magnetic resonance imaging (MRI) in the evaluation of localized lesions. New techniques in nuclear medicine which provide precision with high sensitivity are currently available, such as single-photon emission computed tomography (SPECT), useful in the evaluation of lumbar and hip pathology, or the presence of inflammation in small joints (hands and feet), and positron emission tomography (PET), which provides a metabolic imaging. Several radionuclides can be used in the scintigraphic evaluation, although the most commonly used for bone scintigraphy are labelled with technetium 99-m (99mTc), standing out diphosphonate compounds such as methylene diphosphonate (MDP). This radiopharmaceutical (Tc-99m-MDP) is used for studying metabolic bone diseases like Paget´s disease, transient osteoporosis and reflex sympathetic dystrophy. And it is also useful in the location of polytopic forms of avascular osteonecrosis, in the study of hidden painful radiologic bone lesions such as osteoid osteoma or others bone tumours, in the evaluation of soft-tissue lesions, and in the assessment of spread pattern of bone metastases. Furthermore, this radionuclide may locate bone fractures, identify the cause of pain in patients with chronic pain after arthroplasty, show the evolution of heterotopic ossification and provide information about musculoskeletal system infections (in combination with other radionuclides) and paediatric diseases. Other radionuclides commonly used in the evaluation of infectious or inflammatory processes in the musculoskeletal system are gallium citrate and indium 111-labelled leukocytes, since the latter increases the specificity of technetium radiotracer. Local treatments can be applied by radio isotopic techniques. One of these is radiosynoviorthesis, used in the treatment of patients with persistent monoarthritis in different stages (from inflammatory poliarthritis to pigmentary villonodular sinovitis).

Nuclear Medicine in Musculoskeletal Disorders: Clinical Approach 99

Head and neck: Skull sutures, pterion, occipital protuberance, angle of mandible,

Thorax: Sternoclavicular joint, acromioclavicular joint, sternal foramina,

Abdomen and pelvis: Kidney, bladder, bladder diverticulae, pelvic diastasis (post

Long bones: Deltoid tuberosity/deltoid insertion, trochanteric bursitis

partum women)

addition of dextrose solutions, may affect uptake of radioactivity in bone.

Table 1. Normal Variants of uptake on 99mTc-MDP Bone Scan.

paraspinal muscles (stippled appearance)

Many causes may lead to false pathologic imaging or pitfalls (Naddaf et al., 2004). Bladder diverticula or bladder image over pubic bones, urine leakage or urinary retention and patient rotation are some common examples. Artifacts on bone scintigraphy can be technical or patient-related (**Table 2**). The technical artifacts include equipment, radiopharmaceutical, and image processing-related problems. Equipment-related artifacts may be due to inadequate quality-control procedures and calibration. Faulty radiopharmaceutical preparation alters biodistribution and can compromise the diagnostic quality of the images. Increased tracer uptake in the stomach, thyroid, and salivary glands can be seen if there is free pertechnetate, in the radiopharmaceutical. A number of factors, for example, presence of reduced aluminum ions, if the radiopharmaceutical is left unused for a long time, inappropriately high pH and

Finally, the most common artifact on the bone scan is due to extravasation at the site of injection, that may occasionally cause confusion with a bone abnormality, and it is therefore important to document the site of injection in all patients. Further, ipsilateral lymph node(s) may be seen due to extravasation of radiotracer and can on occasion cause confusion,

disease and microcalcification of thyroid cartilage

hyperostosis frontalis, sinuses (ethmoidal and maxillary), dental

costochondral uptake, manubrium sternum/xiphisternum, tip of scapulae, symmetrical muscle insertion in the posterior ribs of

Fig. 1. Normal bone scintigraphy.

The objective of this chapter is to make a simple but detailed review of the main nuclear medicine clinical applications in the appraisal and management of musculoskeletal problems.
