Phalangeal finger joint prosthesis and method

A phalangeal finger joint replacement kit, comprising:

• a first pin having an elongate shaft for inserting into a proximal end of a phalange on a first side of a finger joint, the first pin further including a head with a lower surface mounted on the shaft and a convex cylindrically-shaped bearing surface that is opposite the lower surface and defines an axis of curvature;
• a second pin having an elongate shaf for inserting into a distal end of a phalange on a second side of the finger joint, the second pin further including a head with a lower surface mounted on the shaf and a convex cylindrically-shaped bearing surface that is opposite the lower surface and defines with an axis of curvature;
• and
• a multiplicity of spacers that are configured to be disposed between the heads of the first and the second pins, each spacer having opposed bearing surfaces that are configured to mate with the bearing surface of one of the heads so that the bearing surfaces of the heads are generally oriented toward each other and coupled in a spaced relationship with parallel axes of curvature to form a finger joint prosthesis and to permit the prosthesis to flex and extend in a single plane while constraining abduction, adduction and rotation of the prosthesis, the spacers having various depths, measured as the shortest distance between the bearing surfaces of the spacer.

A method for replacing a phalangeal finger joint that includes adjacent phalanges with articulating ends that define a pivotal axis, the method comprising:

• resecting at least a portion of the articulating ends of the phalanges to form mounting surfaces;
• providing a pair of opposed pins, which each have a shaft configured to extend into the end of one of the phalanges and a head with lower surface mounted on the end and a convex, cylindrically-shaped bearing surface that is opposite the lower surface and defines an axis of curvature, and a spacer configured to be disposed between the bearing surfaces of the bone-engaging members, the spacer having opposed bearing surfaces that are each configured to receive the cylindrical bearing surface of one of the heads so that the bearing surfaces of the heads are generally oriented toward each other and coupled in a spaced relationship with parallel axes of curvature to form a finger joint prosthesis and to permit the prosthesis to flex and extend in a single plane while constraining abduction, adduction and rotation of the prosthesis;
• inserting the shaft of a first pin into the end of one of the phalanges so that the lower surface of the first pin is adjacent the mounting surface on that phalange and the axis of curvature of the bearing surface is parallel to the pivotal axis of the joint;
• inserting the shaft of the other pin into the end of the other phalange so that the lower surface of the corresponding pin is adjacent the mounting surface on that phalange and the axis of curvature of the head is parallel to the pivotal axis of the joint;
• and
• placing the spacer between the heads of the pins so that the bearing surfaces on the spacer align with the bearing surfaces on the heads to permit the prosthesis to flex and extend in a first plane while constraining abduction, adduction and rotation of the prosthesis.