Samarium 153-labeled hydroxyapatite microspheres for radiation synovectomy in the horse: a study of the biokinetics, dosimetry, clinical, and morphologic response in normal metacarpophalangeal and metatarsophalangeal joints.
OBJECTIVE
To determine the effects of Samarium-153 bound to hydroxyapatite microspheres (153SmM) when injected into the metacarpophalangeal and metatarsophalangeal joints of horses.


METHODS
- Horses were injected with 153SmM in metacarpophalangeal and metatarsophalangeal joints with the diagonal contralateral joints used as untreated controls.


METHODS
Twelve adult horses without pre-existing disease involving the metacarpo/metatarsophalangeal joints.


METHODS
Horses were divided into three groups: high-dose Samarium-153 (12.5 to 17.0 millicurie [mCi]), intermediate dose (6.5 to 12.0 mCi), and low dose (3.5 to 6.0 mCi). Horses were examined daily for 7 days postinjection for clinical abnormalities, lameness, and surface and systemic radiation levels. One horse from each group was euthanatized at 14, 30, and 60 days postinjection and the effects of the 153SmM examined microscopically in the cartilage and synovial membrane.


RESULTS
Intraarticular(153)SmM caused inflammation characterized by lameness, effusion, and regional edema for 48 to 72 hours. Minimal levels of active 153SmM were identified in the blood or urine and were well below the maximal tolerance of 1 mCi. Microscopically the radiation caused no effects on the articular cartilage. The synovectomy created was good but not ideal in that some areas did have necrosis into the subintimal regions and a few islands of intact intimal cells persisted.


CONCLUSIONS
The use of 153SmM is an effective means of targeting the synovial intimal cells with minimal extrasynovial leakage of radiation.


CONCLUSIONS
The metacarpophalangeal and metatarsophalangeal joints of the horse can be safely treated with 153SmM without damage to the cartilage or significant extracapsular leakage.
Yarbrough
T B
TB
Department of Surgical and Radiologic Sciences, University of California, Davis 95616, USA.
Lee
M R
MR
Hornof
W J
WJ
Koblik
P D
PD
Brodack
J
J
Troup
C
C
O'Brien
T R
TR
Pool
R
R
D000818:Animals; D001672:Biocompatible Materials; D017886:Durapatite; D006736:Horses / Q000601:surgery*; D008863:Microspheres; D011868:Radioisotopes / Q000008:administration & dosage / Q000627:therapeutic use*; D011874:Radiometry / Q000662:veterinary; D012016:Reference Values; D012493:Samarium / Q000008:administration & dosage / Q000627:therapeutic use*; D000074402:Synovectomy; D013583:Synovial Membrane / Q000528:radiation effects; D013640:Tarsal Joints / Q000528:radiation effects / Q000601:surgery*
D001672:Biocompatible Materials; D011868:Radioisotopes; D012493:Samarium; D017886:Durapatite