# US 8,739,801 B2 · System and method for identifying a landmark > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 8,739,801 B2 - Document ID: US8739801B2 - Status: Granted - Kind: B2 - Application number: 12/527,997 - Filed: 2008-02-28 - Published: 2010-06-17 - Granted: 2014-06-03 - Earliest claimed: 2007-02-28 - Assignees: Smith & Nephew, Inc. - Applicants: James K. Rains; Nicholas S. Ritchey; Gene Edward Austin; Henry B. Faber; Nathaniel Kelley Grusin; Tobias Schwägli; William M. Ricci - Inventors: James K. Rains; Nicholas S. Ritchey; Gene Edward Austin; Henry B. Faber; Nathaniel Kelley Grusin; Tobias Schwägli; William M. Ricci - Web page: https://patentgrep.com/patent/US8739801B2 ## CPC - A61B 17/1707: {using electromagnetic effects, e.g. with magnet and external sensors} - A61B 17/1725: {for applying transverse screws or pins through intramedullary nails or pins} - A61B 90/11: with guides for needles or instruments, e.g. arcuate slides or ball joints - A61B 17/72: Intramedullary devices, e.g. pins or nails - A61B 34/20: Surgical navigation systems; Devices for tracking or guiding surgical instruments, e.g. for frameless stereotaxis - A61B 2090/062: {penetration depth} - A61B 2090/3958: {emitting a signal} - A61B 2090/397: {electromagnetic other than visible, e.g. microwave} - A61B: DIAGNOSIS; SURGERY; IDENTIFICATION (usefulness limited to only animals A61D) ## Abstract A system (10, 110) for identifying a landmark is disclosed. The system includes a field generator (16, 116) for generating a magnetic field, an orthopaedic implant (30, 130) located within the magnetic field, the implant having at least one landmark (31) and a first magnetic sensor (32) spaced apart from the landmark, a landmark identifier (18, 118) with a second magnetic sensor (20, 120) and a processor (12, 112) for comparing sensor data from the first and second sensor and using the set distance to calculate the position of the landmark identifier relative to the at least one landmark. The system allows for blind targeting of one or more landmarks. ## Claims ### Claim 1 A system for identifying a landmark, the system comprising: a. a field generator for generating a magnetic field; b. an orthopaedic implant configured to be placed within the magnetic field, the orthopaedic implant having at least one landmark, a proximal end, a distal end, and a longitudinal axis extending from the proximal end to the distal end, the orthopaedic implant defining: i. a cannulation that extends along the longitudinal axis and ii. a longitudinal groove that is at least partially offset from the cannulation, the longitudinal groove extending along the longitudinal axis and having a proximal end portion and a distal end portion; c. a first magnetic sensor configured to be placed in the distal end portion of the longitudinal groove and spaced apart from the at least one landmark a set distance; d. a landmark identifier that includes (i) a drill guide configured to receive a drill bit and (ii) a second magnetic sensor that is attached at a fixed position with respect to the drill guide and is configured to move with the drill guide; and e. configured to compare sensor data from the first and second magnetic sensors and use the set distance to calculate the position of the landmark identifier relative to the at least one landmark. ### Claim 2 (depends on 1) The system of claim 1, further comprising a third sensor for sensing a position of a removable element relative to the landmark identifier when the removable element is received in the landmark identifier. ### Claim 3 (depends on 1) The system of claim 1, wherein the cannulation and the longitudinal groove each have a central longitudinal axis, and the central longitudinal axes of the cannulation and the longitudinal groove extend generally parallel to the longitudinal axis of the orthopaedic implant. ### Claim 4 (depends on 1) The system of claim 1, wherein the cannulation extends distally from the proximal end of the orthopaedic implant, and wherein the longitudinal groove extends distally from the proximal end of the orthopaedic implant. ### Claim 5 (depends on 4) The system of claim 4, wherein the cannulation extends to the distal end of the orthopaedic implant, and wherein the longitudinal groove terminates at a location proximal of the distal end of the orthopaedic implant. ### Claim 6 A system for targeting a landmark, comprising: a medical implant having a landmark, the medical implant defining a groove; a processor; a magnetic field sensor; a landmark identifier; a field generator for generating a magnetic field; and a second sensor for sensing a position of an element relative to the landmark identifier when the element is received in the landmark identifier; the system configured such that with the magnetic field sensor located in the groove and oriented in a predetermined position relative to the landmark, the system can be utilized to guide the placement of the landmark identifier relative to the landmark, and wherein the system is configured to generate data from the second sensor while the element is received in the landmark identifier, and the processor is configured to use the generated data from the second sensor to determine a depth of insertion of the element into bone. ### Claim 7 (depends on 6) The system of claim 6 wherein the field generator and the landmark identifier are spaced apart. ### Claim 8 (depends on 6) The system of claim 6 wherein the magnetic field sensor is embedded in the medical implant. ### Claim 9 (depends on 6) The system of claim 6 wherein the magnetic field sensor is wireless. ### Claim 10 (depends on 6) The system of claim 6 wherein the medical implant comprises an intramedullary nail. ### Claim 11 (depends on 6) The system of claim 6 wherein the landmark comprises a hole. ### Claim 12 (depends on 11) The system of claim 11 wherein the system is configured to be calibrated to account for an offset distance between a center of the landmark and the magnetic field sensor. ### Claim 13 (depends on 6) The system of claim 6 further comprising a lead connected to the magnetic field sensor, the lead being located in the groove. ### Claim 14 (depends on 6) The system of claim 6 wherein the magnetic field sensor is attached to a lead, and the lead and the magnetic field sensor are configured for removable receipt within the groove. ### Claim 15 (depends on 6) The system of claim 6 wherein the groove is a longitudinal groove that extends along an outer surface of the medical implant. ### Claim 16 (depends on 6) The system of claim 6 wherein the magnetic field sensor is at a known location and orientation. ### Claim 17 (depends on 6) The system of claim 6 wherein the magnetic field sensor comprises two transverse coils. ### Claim 18 (depends on 6) The system of claim 6 further comprising a guide attached to the medical implant configured to be used for installation of the medical implant and routing of a sensor lead. ### Claim 19 (depends on 6) The system of claim 6 further comprising a display for use in guiding the placement of the landmark identifier relative to the landmark. ### Claim 20 (depends on 19) The system of claim 19 wherein the system is configured to switch between providing gross tracking information and fine tracking information on the display. ### Claim 21 (depends on 6) The system of claim 6 wherein the medical implant defines a longitudinal cannulation, and wherein the groove comprises a longitudinal groove with a proximal end and a distal end, the longitudinal groove being at least partially offset from the longitudinal cannulation. ### Claim 22 (depends on 6) The system of claim 6, further comprising a cover at an exterior of the medical implant, wherein the medical implant has a proximal end and a distal end, wherein a portion of the groove is disposed between the proximal end and the distal end, and wherein the cover is disposed over at least the portion of the groove. ### Claim 23 (depends on 22) The system of claim 22, wherein the medical implant has a shaft and the shaft has an external surface between the proximal end and the distal end, the shaft defining an opening to the groove through the external surface, and the external surface defining a recess around the opening, and wherein the cover is located over the opening and in the recess such that an outer surface of the cover is substantially flush with the external surface of the shaft. ### Claim 24 (depends on 22) The system of claim 22, wherein the cover is formed of a metal foil. ### Claim 25 (depends on 6) The system of claim 6, wherein the second sensor is located to sense one or more indicators on the element as the element moves relative to the landmark identifier. ### Claim 26 (depends on 22) The system of claim 22, wherein the element is a drill bit, and the indicators are markings on the drill bit. ### Claim 27 (depends on 22) The system of claim 22, wherein the second sensor is configured to generate data indicative of a distance that the element is translated relative to the landmark identifier along an axis defined by the landmark identifier. ### Claim 28 (depends on 6) The system of claim 6, wherein the second sensor is configured to interact with the element and generate data based on the interaction with the element; and wherein the second sensor is attached to and configured to move with the landmark identifier. ### Claim 29 A system for targeting a landmark, comprising: a medical implant having a landmark; a magnetic field sensor; a landmark identifier; a field generator for generating a magnetic field; and one or more processing devices configured to determine a distance of the landmark identifier relative to the medical implant and output data for visual representations of the medical implant; the system configured such that with the magnetic field sensor oriented in a predetermined position relative to the landmark, the system can be utilized to guide locating of the landmark identifier relative to the landmark; the one or more processing devices being configured to switch, based on a distance of the landmark identifier to the medical implant, between (i) providing data for a zoomed-in view of the medical implant and (ii) providing data for a zoomed-out view of the medical implant. ### Claim 30 (depends on 29) The system of claim 29 wherein the one or more processing devices are configure to provide, for display, first data that indicates the distance of the landmark identifier to the medical implant and second data that indicates alignment information for an alignment of the landmark identifier relative to the landmark. ### Claim 31 (depends on 29) The system of claim 29, wherein the one or more processing devices are configured to: select a view from among multiple different views of the medical implant based on the location of the landmark identifier relative to the medical implant; and provide, for display, information indicating the selected view of the medical implant. ### Claim 32 (depends on 31) The system of claim 31, wherein the one or more processing devices are configured to select the view from among multiple different views that each correspond to different angular range with respect to the medical implant. ### Claim 33 A system for targeting a landmark, comprising: a medical implant having a landmark, the medical implant defining a groove; a magnetic field sensor; a landmark identifier; a field generator for generating a magnetic field; and a second sensor for sensing a position of an element relative to the landmark identifier when the element is received in the landmark identifier; the system configured such that with the magnetic field sensor located in the groove and oriented in a predetermined position relative to the landmark, the system can be utilized to guide the placement of the landmark identifier relative to the landmark, and the system configured such that with the element received in the landmark identifier, data from the second sensor can be utilized to determine a depth of insertion of the element into bone, wherein the second sensor is located to sense one or more indicators associated with the element as the element moves relative to the landmark identifier, and wherein the element is a drill bit, and the indicators are markings on the drill bit.