Transport of Radioactive Sodium Across the Synovial Membrane of Normal Human Subjects.

Any investigation of physiological function of the synovial membrane of joints is limited by suitable technics for the study of this relatively inaccessible structure. The availability of a variety of isotopes obviates some of these difficulties. The present investigation was designed to study the sodium clearance of the synovial membrane by means of radioactive sodium. A group of 35 healthy adults were injected in the knee synovial space with Na24 and the clearance rate determined. The results of this study of normal subjects reveal that significant differences are encountered between normal men and women. The present report describes these variations. Method. Radioactive sodium (Na24) was obtained from the Oak Ridge National Laboratories as Na242C03. It was converted to Na24Cl and suitably diluted to produce an 0.85% sodium chloride solution with an adjusted pH of 7.3. The concentration of Na24 was 30-40 °c in each milliliter. After local novocaine anesthesia a 20-gauge needle was inserted under the lateral inferior border of the patella into the synovial space of the knee. Two milliliters of the sterile radioactive sodium chloride were injected and the needle withdrawn. By means of a Geiger-Mueller counter tube placed 6-10 cm from the lateral aspect of the knee, the amount of gamma radiation from the knee was automatically recorded on a rate meter at 2-minute intervals. The subject was not allowed any activity during the course of the experiment. All recordings were made with the leg in extension. Continuous observations were made over a 40-minute period. A total of 35 healthy adults consisting of 12 males and 23 females was studied. Two of the males and one of the females were studied on 2 different occasions. None had any preceding history of arthritis or traumatic injury to the knee.