**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

Nuclear Medicine in Musculoskeletal Disorders: Clinical Approach 131

Though scintigraphical examination is ideal in the early stages of diseases, it also plays a complementary role to radiographical investigations in more advanced disease stages. An assessment as complete as possible which includes different complementary studies must be performed to achieve the best diagnostic and prognostic accuracy. In this context, conventional scintigraphy is still a major test in a limited number of rheumatological diseases such as Paget, reflex sympathetic dystrophy and osteonecrosis, and can be a useful complementary study in other diseases. New molecular imaging tools for the evaluation of musculoskeletal diseases are now available and these particular tools will advance the understanding and management of several chronic musculoskeletal diseases. In the next decade, PET/CT and SPECT/CT will be the major workhorses for molecular imaging, with the advantage that PET-based technologies have high sensitivity and the ability to use

Despite the important role of the anatomic imaging techniques in the evaluation of primary bone tumors and metastases, radionuclide imaging techniques have all been used in the assessment of these disorders. PET and hybrid PET/CT imaging are becoming the most

Β-radiation emission from some radionuclides has been exploited by nuclear medicine and has been used to treat benign joint pathologies, as well as treating several forms of neoplasia. It is of interest in the field of rheumatology, since it is as a safe procedure and, after intra-articular administration of suitable radiopharmaceuticals, is able to control proliferation of the inflamed synovial membrane in the treatment of chronic arthropathies,

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**16. References** 

radionuclides have been exploited by nuclear medicine and, as well as treating several forms of neoplasia, this method can also be used to treat a number of benign articular pathologies in the field of rheumatology. Carry out a 'radiosynovectomy' procedure is possible after intra-articular administration of suitable radiopharmaceuticals. The direct irradiation of the synovial membrane can produce a therapeutic effect on persistent synovitis that is resistant to traditional drug treatment. The radiopharmaceuticals that have been used to date for radiosynovectomy are made up of small colloidal particles labelled to β-emitting isotopes (yttrium-90, rhenium-186, erbium-169, samarium-153). These compounds release their radiation energy within a radius of a few millimetres from the uptake sites. These substances are phagocytized by synoviocytes localised in relation to the synovia and it creates a radiation source that can act locally and reduce inflammatory and proliferative elements (Colamussi et al., 2004; as cited in Gumpel et al., 1975). The availability of new radiopharmaceuticals, created by replacing the colloid vector with hydroxyapatite crystals, has allowed the main undesired effect of these substances (radiation to other organs such as drainage lymph nodes, liver, spleen and bone marrow, due to the passage of the radio compound from the articular cavity to the lymphatic and then to the blood flow systems) to be avoided (Clunie et al., 1996). In the absence of side effect, this technique of low cost may be useful, not only in the treatment of advanced stage and drug-resistant arthropathies, but also to manage pain and improve articular function in the first stages of rheumatoid arthritis (Colamussi et al., 2004; as cited in Uyeo et al., 1978). A fundamental element to the success of radiosynovectomy therapy is that treatment is started early in the disease's history. This is because while radiation therapy can successfully control proliferation of the inflamed synovial membrane, it is not effective in joints that have suffered advanced osteo-cartilage damage and where the synovitic component is virtually non-existent (Franssen et al., 1989). Cases reported would further suggest its use in a wider spectrum of rheumatic disorders ranging from spondylitis to Paget's disease and from hæmophiliac synovitis to pigmented villonodular synovitis. Nevertheless, despite abundant anecdotal evidence of its efficacy, there is a paucity of controlled trials and those that have been done have produced conflicting results (Dos Santos et al., 2009, 2011) and/or have been of insufficient sample size. Two meta-analyses have been published. The first one (Jones, 1993) was made in order to assess the evidence on yttrium-90 therapy for chronic synovitis of the knee. It found out that Yttrium was superior to placebo (OR 2.42, 95% CI 1.02-5.73), although possible publication bias limited the interpretation of this result. Yttrium was not superior to triamcinolone (OR 1.89, 95% CI 0.81-10.55) or other active modalities (OR 1.04, 95% CI 0.72-1.52). The second one and most recent (Van der Zant et al., 2009) has been published with the objective to perform a systemic review and meta-analysis on the effectiveness of radiosynoviorthesis. It has shown high success rates of radiosynoviorthesis, but differences in effect with glucocorticoid injection are less evident, although there is marked heterogeneity in study design of a small number of comparative studies. Therefore the efficacy of radiosynovectomy alone or in combination with steroid therapy must be assessed by other sufficiently powered randomised controlled studies.
