[Radiosynoviorthesis of the knee joint: Influence on Baker's cysts]

The study examines the influence of a radiosynoviorthesis of the knee joint on the Baker's cyst volume over time.

Patients with radiosynoviorthesis of the knee joint with simultaneous Baker's cyst were retrospectively selected and asked for a sonographic control. The presence of a pre-therapeutic sonography with imaging of the Baker's cyst in longitudinal and cross-sectional view to determine the volume was necessary. Exclusion criterion was an intermediate therapy with influence on the volume of the Baker's cyst. Groups were formed with a time interval of 3 months (2 to 4 months, 5 to 7 months, etc.) after radiosynoviorthesis. If the number of patients within a group was too small, the group was combined with the following group. Pre- and posttherapeutic Baker's cyst volumes were compared. In 4 evaluable groups, the significance level was determined to p = 0.0125 using Bonferoni-correction.

102 radiosynoviorthesis in 84 patients aged between 23 and 86 years could be evaluated. These could be assigned to groups with a distance to the radiosynoviorthesis of 2 to 4 months, 5 to 7 months, 8 to 16 months as well as 20 and more months. In group 1 the volume decreased by 53 % (p < 0.007), in group 2 by 47 % (p < 0.007), in group 3 by 18 % (p < 0.005) and in group 4 by 73 % (p < 0.0007). No serious complications occurred with any radiosynoviorthesis.

The study shows a positive effect of a radiosynoviorthesis on an existing Baker's cyst, even over a longer period of time. Therefore, it seems reasonable to establish radiosynoviorthesis as a component of a multimodal therapy, for example before surgical intervention.