Abstract: A straight, double-threaded arthrodesis screw that comprises a threaded compression nut mounted thereon. The screw consists of a shank containing distal right-handed threads for screwable connection with a threaded hole in the bone, proximal left-handed threads on which the compression nut is screwably mounted, and a longitudinal perforation for engagement with an installation tool. A hole is first drilled and tapped in the bone to provide an internal right-handed thread conforming to the distal threads of the arthrodesis screw. The screw is installed on the bone by screwably mounting its distal portion in the hole. The compression nut is then rotated toward the proximal cortex of the bone until it contacts the soft tissue surrounding the hole in the bone. The soft tissue is secured in place between the compression nut and the bone's cortical surface by further screwing the distal threads into the bone while preventing the compression nut from turning with respect to the clamped tissue.

Abstract: A method of administering post-operative anesthesia directly to the surgical site through a catheter introduced into the site during the post-operative procedure. The flow of medication into the catheter is regulated by a micro-bore cannula that insures delivery at very small rates. The plunger of a spring-loaded syringe creates the pressure that causes the medication to flow through the cannula and catheter into the wound. Because of the spring's nonlinear characteristics within the range of stroke of the plunger, the pressure exerted on the liquid gradually decreases with the expansion of the spring. By appropriately sizing the spring and the inside diameter of the cannula, a device is developed that administers the required dosages of anesthetic continuously and at decreasing rates.