Abstract: According to one aspect of the present invention, a computer assisted orthopaedic surgery system for performing joint replacement or resurfacing surgeries includes a computer that contains software that is adapted to permit an operator of the system to physically evaluate post-operative laxity and stiffness of a joint based on planned implant placement, prior to all cuts being made for at least one side of the joint to accommodate the implant and before components of the implant are installed in the joint, wherein the planned implant placement is measured in terms of a position of at least one virtual implant.

Abstract: A DHD hammer that can exhaust working air volumes partially through a proximal end of the DHD hammer's actuator assembly includes a drive chamber, a return chamber, and a backhead that includes exhaust ports. Working air volumes from the drive chamber are exhausted through the backhead while working air volumes from the drive chamber are exhausted primarily through a drill bit.

Abstract: A medical instrument includes a base; an upper member; and a linkage mechanism coupled to the base and the upper member and being operable to maintain the upper member in a variable fixed position that is substantially parallel to the base and spaced a predetermined, variable distance therefrom, wherein the linkage mechanism includes at least three linkage elements that are arranged at angles relative to one another such that when one link element opens, the other link elements open with at an equal angle resulting in the upper member being constrained to remain parallel to the base.

Abstract: A computer-assisted orthopaedic surgery system includes a device for generating a three dimensional geometrical surface model of a first bone and a database containing three 3 dimensional implant models of a plurality of available implants. The system includes a computer that is configured to permit a user to select from the database a first implant and display on a screen the three dimensional implant model of the first implant. The computer superimposes on the screen the implant model on top of the model of the first bone such that the two models are visually identifiable from one another.