Patent ID: 7588578

Claim:
A system comprising: A first measurement tool comprising: A registration interface configured to be coupled to a first bone portion to limit relative translation between the registration interface and the first bone portion along three nonparallel directions, wherein the registration interface comprises a bore having a noncircular shape configured to restrict relative rotation between the registration interface and the first bone portion; A contact feature positionable in contact with a bony landmark; A displacement structure that couples the contact feature to the registration interface such that the contact feature is translatable with respect to the registration interface along three nonparallel axes to indicate displacements between the registration interface and the bony landmark along each of the nonparallel axes, wherein the displacement structure comprises: At least one sliding joint; At least one rod comprising a stop feature configured to prevent accidental withdrawal of the rod from the sliding joint; Wherein the stop feature comprises an intrinsic spring integrally formed with an end of the rod; and A frame attachable directly to the first bone portion such that the frame abuts the first bone portion, the frame comprising a post insertable into the bore to couple the registration interface to the first bone portion.