Savaser and colleagues reported a case of needle track ulceration after RSO of an ankle joint with Re-186 in 1999 [4]. The lesion showed scarred healing after a few weeks without any further treatment. In a series of 38 knee joints treated with Yttrium-90, three patients showed “minor pigmentation at the injection site”; a needle track ulceration was documented in two other patients [5] which required treatment with skin grafting in one case.

While superficial lesions often show (scarred) healing without any special therapy, larger necroses with radiogenic damage of deeper tissue layers should be promptly treated to shorten the course of the disease and to minimize the complaints of the respective patients. Necrosis of para-articular tissue by accidental para-articular injection of the radionuclide is indeed the worst local complication after radiosynovectomy. Due to a restricted blood supply of the necrotic area, the healing process is additionally hampered by a low oxygen content.

The frequency of larger skin or soft tissue necroses is generally assumed to be very low which is proven by the analysis of the periodic safety update reports (see chapter by Fischer et al. in this book). Two necroses from a total of 11,000 RSO procedures were reported by Kolarz and Thumb in 1982 [6]. In another study which involved interrogation of both 260 nuclear medicine physicians performing radiosynovectomy throughout Germany and 20 insurance companies engaged in medical liability using a standardized questionnaire and covering 5 years, a total of 29 necroses were documented [7]. However, the response rate was only 25.7 % after 9 months. Thus, the true number of radionecroses after para-articular radionuclide application is probably higher but will never be reliably documented.

Deeper skin necroses have been documented in case reports [8, 9]. Due to the more pronounced deterioration of deeper tissue layers, a spontaneous healing cannot be expected, and surgical debridement and closure of the defect by skin grafting seems to be the adequate treatment.

Besides an insufficient injection technique, the choice of an inappropriate radionuclide and/or an excessive activity may be the reason for a radionecrosis. The choice of the appropriate radionuclide for a joint depends mainly on the tissue penetration depth of the beta particles which is particularly dependent on the energy of the radionuclide. This penetration depth must be suitable for the size of the joint which should be treated. Yttrium-90 has a maximum beta energy of 2.2 MeV resulting in a maximum tissue penetration depth up to 11 mm (mean value 3.6 mm). Thus, Y-90 is expected to be the most hazardous radionuclide used for radiosynovectomy and is approved for treatment of the knee joint only. Small joints (finger or toe joints, acromioclavicular, sternoclavicular, temporomandibular) must be injected with the low-energy beta emitter Erbium-169 (mean beta energy 0.34 MeV) which has a mean penetration depth of only 0.3 mm. Rhenium-186 is approved for treatment of mid-sized joints like wrist, elbow, ankle, or hip joint and has a mean penetration depth of 1.2 mm.

A further alignment to the different joints is accomplished by using different activities for joints of different sizes. This is documented in both national and international guidelines for radiosynovectomy, although not a legal requirement [10, 11].

Examples of radiogenic damage of the surrounding soft tissue following inappropriate choice of a radionuclide with an energy too high for the treated joint are published in the literature. Two necroses from RSO using Yttrium-90 in finger joints (metacarpophalangeal joint and proximal interphalangeal joint) were documented in an old study from 1972, covering a total of 250 treatment sessions [12]. However, no further information on the clinical course or treatment modalities is given in this paper. More recent studies showed severe complications with large, deep tissue ulcerations in ankle joints treated with Yttrium-90. Two cases of severe necroses were seen in a series of 7 RSO procedures of ankle joints treated with 555 MBq Yttrium-90 [13]. Another case report showed the same complication after RSO using Yttrium-90 in an ankle joint; however, the injected activity is not documented in this publication [14]. Thus, the combination of the “wrong” radionuclide (Yttrium-90 instead of Rhenium-186) and an excessive activity led to these serious complications which needed aggressive treatment with surgical excision of the necrotic soft tissue and closure with a fasciocutaneous flap.

The treatment of choice for these complications is still under debate. Some advice may be gained from therapy of radiogenic lesions after external beam radiation therapy. The common problem in both clinical settings is that radiation leads to parenchymal stem cell and vascular damage. This results in a reduced capacity of tissue regeneration from local hypoxia, finally leading to tissue necrosis [15]. Apart from a “wait-and-see” strategy or local conservative treatment, hyperbaric oxygen therapy may be used to overcome the local oxygen shortage. The higher oxygen partial pressure induces revascularization of irradiated tissue and thus promotes its self-healing mechanisms [16] with clinical success rates up to 93 % in treatment of radiation-induced edema, ulceration, and bone necroses [15]. In our own survey, hyperbaric oxygen therapy was used in three cases of tissue necrosis after para-articular injection of Re-186 colloid with clinical success in two of them. However, in one patient with a local radiogenic tissue defect from Yttrium-90, 40 sessions of hyperbaric oxygen did not prevent tissue necrosis, and surgical therapy was needed [7].

Successful treatment requires complete resection of the damaged tissue with consecutive closure of the defect with well-vascularized, nonirradiated tissue. Depending on the severity and the dimensions of the local defect, either regional pedicled flaps or free-tissue transfer has been used [7, 9]. Despite appropriate surgery, complications with local wound dehiscence, seroma, or blood vessel thrombosis are seen, sometimes resulting in complete flap loss [17]. Due to the very low beta energy, skin ulcers from Er-169 colloids are likely to heal spontaneously with less pronounced tissue damage.