**13.2.2 Legg-Calve Perthe disease**

Legg-Calve Perthes disease is an idiopathic ischemic necrosis of the femoral head that occurs characteristically in children between 5 to 8 years. Bone scintigraphy is more sensitive than radiography for early diagnosis, and comparable to MRI (Shammas, 2009; as cited in Ma et al., 2007). Studies performed early after the onset of clinical symptoms show absence of activity in the capital femoral epiphysis and it may precede radiographic changes (Shammas, 2009; as cited Connolly & Treves, 1998). Later scans may demonstrate increased activity due to revascularization and remodeling. Bone scintigraphy has also a pronostic value and can be used in routine management to identify patients at high risk for a poor outcome (Shammas, 2009; as cited in Comte et al., 2003): Persistent absence of bone uptake in the proximal femoral epiphysis after 5 months or metaphyseal hyperactivity is highly correlated with more severe disease and a poorer prognosis. The early formation of a lateral column of tracer uptake in the capital femoral epiphysis, even before radiography, is associated with a good prognosis due to early revascularization (Shammas, 2009; as cited in Conway, 1993 and Tsao et al., 1997).

#### **13.2.3 Slipped capital femoral epiphysis**

Slipped capital femoral epiphysis is characterized by a displacement of the capital femoral epiphysis from the femoral neck through the physeal plate with medial and posterior rotation of the epiphysismost commonly in the adolescence. Bone scintigraphy is useful for

Nuclear Medicine in Musculoskeletal Disorders: Clinical Approach 129

to other radiologic investigations. Its major advantage is the increased sensitivity in detecting evidence of soft-tissue and bone trauma (25%to 50%), and in the documentation of specific and characteristic sites of abuse, such as in the ribs or the diaphyses of the extremities (Nadel &

Benign bone tumors are by far the most common type of tumors that grow within the skeleton. Nonossifying fibromas, osteochondromas and simple bone cysts are the types most often found in children and teenagers. Children between the ages of 6 and 12 are the most likely to develop benign bone tumors, although the tumors sometimes show up in children as young as age 2. Exostosis tumors are slightly more common in boys than girls. Nonossifying fibroma usually is in the actively growing sections of long bones such as the thighbone (femur). Exostosis (osteochondroma) contains both bone and cartilage and usually grows in the thighbone, the shinbone (tibia) or the bone in the upper arm (humerus). Unicameral (simple) bone cysts are holes in the bone that fill with fluid and tissue. They usually occur in the bone in the upper arm or in the upper part of the thighbone. In some cases, a benign bone tumor can cause problems while it grows. It can weaken the child's bone and make it more likely that the bone will break. Tumors also can press on nerves and cause pain. In cases like these, surgery may be necessary. Malignant primary bone tumors make up 5% of childhood malignancies, and osteosarcoma is the most commonly isolated malignant bone tumor in children, followed by Ewing's sarcoma. These bone neoplasms usually begin during childhood and adolescence, when bones are growing quickly and they often are taking part in sports and other physical activities. Langerhans cell histiocytosis is also more common in the pediatric population. A smaller number of patients have other diagnosis such as malignant fibrous histiocytoma, angiosarcoma and chondrosarcoma, but these conditions are very rare in paediatric population. The use of nuclear medicine techniques in the diagnosis, staging and monitoring of the different bone tumors has been detailed in a previous section of this chapter. FDG-PET has become to be one of the best tools for the baseline evaluation and follow-up, although some benign bone lesions may show high 18F-FDG accumulation, equivalent to osteosarcomas. Despite this, 18F-FDG-PET has a high specificity for excluding malignant bone tumors (Cook et al., 2010). FDG- PET has been shown to help determine the presence and extent of sarcomas and even may allow the noninvasive estimation of the histologic grade of some tumors, although the biopsy remains necessary. This technique allows targeted biopsies, which can reduce the likelihood of underestimation of tumor grade and inadequate therapy. Furthermore, 18F-FDG-PET is useful in the pediatric population for detection of skip metastases in cases of

Stilwell, 2001; as cited in Conway et al., 1993, Sty & Wells, 1994).

**13.2.7 Primary bone tumors in childhood** 

equivocal MRI findings (Even-Sapir, 2007).

**14. Therapeutic alternatives with radionuclides: Radiosynoviorthesis** 

In the treatment of inflammatory rheumatic diseases with chronic course, operative and respectively arthroscopic synovectomy on the one hand and synoviorthesis on the other hand come into question. Synoviorthesis by corticosteroids has a very large indication if the corresponding measures of precaution are heeded. Chemical synoviorthesis, mainly by osmium tetroxide, is applied above all in exudative inflammatory diseases, whereas radiosynoviorthesis with the nuclides used at present is mainly applied in proliferative diseases. The cytotoxic effects intrinsic to the beta radiation emission from some

assessing the vascularity of the femoral head. In the absence of avascular necrosis, the bone scan findings in slipped capital femoral epiphysis are nonspecific and consist of mildly increased activity with widening and blurring of the growth plate activity (Shammas, 2009; as cited in Connolly et al., 2006, 2007).
