Evaluation of samarium-153 for synovectomy in an osteochondral fragment-induced model of synovitis in horses.

The study evaluates the effectiveness of intraarticular administration of samarium-153 (153Sm), a radioactive isotope, combined with hydroxyapatite microspheres for synovectomy in horses suffering from synovitis, an inflammation of the joint lining, due to osteochondral chip-induced injury. The research suggests that 153Sm bound to hydroxyapatite microspheres can cause a synovectomy and may be beneficial for treating persistent synovitis that is unresponsive to traditional methods.

Methodology

• The study involved fifteen horses that did not have pre-existing joint disease. The horses were randomly divided into two groups: one with seven members and the other with eight.
• Osteochondral fragments were harvested from the lateral ridge of the trochlea of the talus, an ankle bone of the horses, and implanted bilaterally into a metacarpophalangeal joint (a joint of the toe or finger) and a middle carpal joint (a joint of the wrist).
• Days post-implantation, intraarticular administration of 10 to 15 mCi of 153SmM, 153Sm bound to hydroxyapatite microspheres measuring 20 to 50 microm in diameter, was given into the joint with the fragment implant. The opposite joint served as the control.
• For comparison, three horses were treated with non-radioactive hydroxyapatite fragments.
• All horses underwent clinical exams until they were euthanized either 14 or 30 days later, after which an evaluation of both control and treated joints was performed to determine the effects of the 153SmM on the synovial membrane and cartilage.

Findings

• The administration of 153SmM resulted in a transient flare characterized by lameness, effusion, and edema lasting between 48 to 72 hours.
• The implanted osteochondral chips induced synovitis, leading to variable extent of joint damage and synovial infiltration.
• The use of 153SmM caused a synovectomy of variable depth and extent, indicating the possibility of it being a useful method for removal of inflamed synovial membrane.

Conclusions

• The study concluded that intraarticular 153SmM has the potential to be a useful method for synovectomy in horses, especially in cases of persistent synovitis not responsive to traditional methods. However, further testing is necessary to establish this.
• The short-term adverse effects such as lameness, effusion, and edema should also be taken into consideration when planning for wider application of this method.