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

The future of radiosynoviorthesis: bright or bleak?

Radiosynoviorthesis (RSO) is a decades known, effective intra-articular nuclear medicine local therapy, with few rare side-effects, in which inflamed synovial membrane is treated by means of colloidal beta-emitters. There are major variations worldwide in terms of acceptance, frequency of use and approved indications for this procedure. Thus, reliable figures that reflect reality are only available for a few countries. A Europe-wide survey revealed that RSO is carried out most frequently in Germany, where RSO is the most common nuclear medicine therapy with about 70,000 joints treated per year. The main indications include synovitis due to rheumatoid arthritis, hemophilia and pigmented villonodular synovitis (PVNS), and depending on national approvals, osteoarthritis. Despite the many indications, there are very few published scientific studies and therefore, RSO evidence is lacking. Reliable data on the clinical usage of RSO and demographics of RSO specialists are only available in Germany, thus we discuss the future challenges of RSO mainly from a German perspective. In the German healthcare system, RSO is performed primarily on an outpatient basis and plays only a minor role in the university setting. The necessary expertise for RSO is therefore lacking, for the most part, at university training centers. Currently, nearly more than three quarters of the German RSO experts are over fifty years old, illustrating a shortage of young talent. In the future, RSO providers from the non-university or private sector will have to cooperate with universities through networks and will have to intensify their cooperation with referring physicians, such as rheumatologist and orthopedic surgeons, and patients in order to maintain a timely and beneficial exchange of information. In networks of RSO experts, the participants must jointly develop and establish training concepts and facilities for future talents, elaborate on guidelines, if clinically useful expand the range of indications, initiate studies to generate further evidence and finally make the procedure more public. In addition, it is worthwhile to apply this process beyond human medicine to other fields, such as medical physics and veterinary medicine. If these points are implemented, the future of RSO will be bright, if it fails, it looks bleak.

Evaluation of iatrogenic hemarthrosis of the metacarpophalangeal joint as a method of induction of temporary reversible lameness in horses

OBJECTIVE

To determine whether iatrogenic hemarthrosis of the metacarpophalangeal joint could be used as a model for temporary reversible joint pain in horses.

ANIMALS

8 adult horses.

PROCEDURE

Each horse was evaluated on a treadmill before and after injection of 1 metacarpophalangeal joint with 10 mL of autogenous blood. Horses were evaluated subjectively and objectively by use of a computerized force measurement system at intervals until lameness abated. The mean force difference between injected and noninjected limbs at all time periods after injection was compared with the difference between limbs at baseline. From each horse, synovial fluid samples collected before and 24 hours and 30 days after injection were analyzed for total protein concentration and cell type and number. Venous blood samples were collected before and 6 and 24 hours after injection for assessment of plasma cortisol concentration.

RESULTS

For 24 hours after injection, the mean force difference between injected and noninjected limbs was significantly increased over baseline. The greatest force difference was detected after 2 and 4 hours. Baseline and 24-hour force data were not significantly different. Compared with baseline values, synovial fluid protein concentration and nucleated cell and RBC counts were increased significantly at 24 hours after injection but were not different at 30 days after injection. No significant changes in plasma cortisol concentration were detected at any time point.

CONCLUSIONS AND CLINICAL RELEVANCE

In horses, iatrogenic hemarthrosis of the metacarpophalangeal joint appears to induce temporary reversible lameness with a mild to moderate degree of synovitis.

Radiation synovectomy with holmium-166 ferric hydroxide macroaggregate in equine metacarpophalangeal and metatarsophalangeal joints

OBJECTIVES

To evaluate the effects of radiation synovectomy (RSYN) with holmium-166 ferric hydroxide macroaggregate (Ho-166 FHMA) on synovium and synovial fluid in normal metacarpo- and metatarsophalangeal joints of horses and to determine intraarticular distribution of radioactivity after Ho-166 FHMA treatment.

STUDY DESIGN

Either Ho-166 FHMA or nonradioactive Ho-165 FHMA was injected into metacarpo- or metatarsophalangeal joints.

ANIMALS

Six adult mixed-breed horses without any clinical evidence of metacarpo- or metatarsophalangeal joint disease.

METHODS

Joints were injected with a single high dose of Ho-166 FHMA (mean, 1,000 MBq/joint) or a nonradioactive Ho-165 FHMA preparation (controls). Clinical examination, arthroscopy, synovial fluid analyses, and histologic studies were performed to detect effects of RSYN. Scintigraphy was used to localize intraarticular distribution of Ho-166 FHMA.

RESULTS

Ho-166 FHMA treatment induced joint inflammation leading to regional edema, effusion, and scar tissue formation. Scintigraphy revealed the highest intensity of radioactivity in the proximal plantar joint pouch, at which the Ho-166 FHMA treatment caused multifocal necrosis. In the dorsal joint pouch, however, arthroscopic study and histologic analysis showed very little effect of RSYN. There was no regeneration of synovium evident within 2 months. Synovial fluid protein concentration was significantly (P <.01) elevated, and some residual radioactivity remained for 5 days after Ho-166 FHMA injection.

CONCLUSIONS

Injection of a single high dose of Ho-166 FHMA caused multifocal necrosis of synovium and deep, soft-tissue injury in equine fetlock joints.

CLINICAL RELEVANCE

Inflamed equine joints with synovial lining hyperplasia could benefit from Ho-166 FHMA-induced radiation synovectomy if excessive scar tissue formation can be avoided.