Abstract: A modular prosthesis has an intramedullary rod element which is to be inserted in a bone, an artificial trochanter and a neck for carrying the ball. The intramedullary rod has a proximal end and a distal end telescoped together allowing free relative rotation of the ends. A split sleeve is fitted between the telescoped portions of the rod to form a rigid connection when the ends are separated longitudinally. A jack screw within the intramedullary rod separates the proximal end from the distal end.

Abstract: A screw for use in spinal and other surgical procedures has a tapered core and fixed pitch threads. The threads have a compound curved inferior surface and constant width crest. The screw may be provided with a helical thread in which at least the lead thread adjacent to the screw tip is ledged and the following threads have sharp apices. A method of making the screw requires two tool bits making two different angular cuts to the inferior surface of the threads.

Abstract: A modular prosthesis has an intramedullary rod element which is to be inserted in a bone. The rod has a shaped proximal portion which is telescoped into one end of a bore in the body element. The mating surfaces of the shaped rod and the body bore form a rotationally immovable connection. A neck element is telescoped into the other end of the body bore. The neck and the body have mating planar surfaces visually discernable as being spaced apart. The neck and body have complementary tapered walls. The prosthesis is subjected to compression to eliminate the visual gap and produce a rigid area seal. All the elements are secured together by a compression screw through the neck, body and rod.

Abstract: A modular prosthesis has an intramedullary rod element which is to be inserted in a bone. The rod has a shaped proximal portion which is telescoped into one end of a bore in the trochanter element. The mating surfaces of the shaped rod and the trochanter bore form a rotationally immovable connection. A neck element is telescoped into the other end of the trochanter bore permitting rotational adjustment. All the elements are locked together by a bolt through the neck and rod.

Abstract: A joint prosthesis having an intramedullary insert. The intramedullary insert has an elongated body with an attached coil spring. The coil spring may be constructed to provide variable flexibility at different locations along the spring. A control rod is inserted through the coil spring and attached thereto further modifying the flexibility of the coil spring. The shape of the control rod may be varied throughout its length producing different flexibility. The selection of a particular coil spring and a particular control rod resulting in particular joint prosthesis.