Method for enabling medical navigation with minimised invasiveness
A method for providing positional relationship data, which represent the position of a marker device relative to a bone which it is affixed to, to a medical navigation system, including receiving bone registration data which represent locations of points on the surface of the bone, calculating, from the bone registration data, the current relative position between the bone and a medical instrument which bears the marker device, determining an offset between the current relative position and a desired relative position; outputting indication information which is based on the calculated offset, receiving bone re-registration data which represent locations of points on the surface of the bone, and calculating the positional relationship data from the bone re-registration data.
1. A method, executed by a computer, for tracking a bone, comprising the steps of:
a) receiving bone registration data that represent locations of points on the surface of the bone;
b) calculating, from the bone registration data, a current relative position between the bone and a medical instrument that bears a marker device;
c) determining an offset between the current relative position and a desired relative position;
d) outputting indication information that is based on the offset;
e) receiving bone reregistration data that represent locations of points on the surface of the bone, wherein the bone reregistration data is a reduced set of data as compared to the bone registration data;
f) augmenting the bone reregistration data based on the bone registration data;
g) calculating positional relationship data from the bone reregistration data; and
h) tracking the bone by tracking the marker device and using the positional relationship data.
2. The method according to claim 1 , wherein Steps a) to d) are repeated until the offset is below a threshold due to movement of one or more of the medical instrument and the bone.
3. The method according to claim 1 , wherein the bone registration data received in Step a) are also used in Step g) to calculate the positional relationship data.
4. The method according to claim 1 , comprising additional steps, between Steps d) and e), of receiving the number of degrees of freedom of movement of the bone and calculating, using the degrees of freedom of movement of the bone, a number of points on the surface of the bone that are required for reregistration.
5. The method according to claim 1 , wherein one or more of the bone registration data or the bone reregistration data are specified in a coordinate system that is defined relative to the marker device.
6. The method according to claim 1 , wherein marker device position data that represent the position of the marker device, and one or more of the bone registration data or the bone reregistration data are specified in an external coordinate system.
7. The method according to claim 1 , wherein the indication information comprises information to indicate that the current relative position between the bone and the medical instrument is invalid.
8. A computer program product for tracking a bone, the computer program product comprising a non-transitory computer readable storage medium having program instructions embodied therewith, the program instructions executable by a processor to cause the processor to:
a) receive bone registration data that represent locations of points on the surface of the bone;
b) calculate, from the bone registration data, a current relative position between the bone and a medical instrument that bears a marker device;
c) determine an offset between the current relative position and a desired relative position;
d) output indication information that is based on the offset;
e) receive bone reregistration data that represent locations of points on the surface of the bone, wherein the bone reregistration data is a reduced set of data as compared to the bone registration data;
f) augment the bone reregistration data based on the bone registration data;
g) calculate positional relationship data from the bone reregistration data; and
h) track the bone by tracking the marker device and using the positional relationship data.
9. The computer program product according to claim 8 , wherein Steps a) to d) are repeated until the offset is below a threshold due to movement of one or more of the medical instrument and the bone.
10. The computer program product according to claim 8 , wherein the bone registration data received in Step a) are also used in Step g) to calculate the positional relationship data.
11. The computer program product according to claim 8 , wherein the program instructions are further executable by a processor to cause the processor to:
receive the number of degrees of freedom of movement of the bone; and
calculate, using the degrees of freedom of movement of the bone, a number of points on the surface of the bone that are required for reregistration between Steps d) and e).
12. The computer program product according to claim 8 , wherein one or more of the bone registration data or the bone reregistration data are specified in a coordinate system that is defined relative to the marker device.
13. The computer program product according to claim 8 , wherein marker device position data that represent the position of the marker device, and one or more of the bone registration data or the bone reregistration data, are specified in an external coordinate system.
14. The computer program product according to claim 8 , wherein the indication information comprises information to indicate that the current relative position between the bone and the medical instrument is invalid.
15. A medical navigation system for computer assisted surgery, comprising:
a cutting block that bears a marker device; and
a non-transitory computer readable storage medium having program instructions embodied therewith, the program instructions executable by a processor to cause the processor to:
a) receive bone registration data that represent locations of points on the surface of the bone;
b) calculate, from the bone registration data, a current relative position between the bone and the medical instrument;
c) determine an offset between the current relative position and a desired relative position;
d) output indication information that is based on the offset;
e) receive bone reregistration data that represent locations of points on the surface of the bone, wherein the bone reregistration data is a reduced set of data as compared to the bone registration data;
f) augment the bone reregistration data based on the bone registration data;
g) calculate positional relationship data from the bone reregistration data; and
h) track the bone by tracking the marker device and using the positional relationship data.
16. The medical navigation system for computer assisted surgery according to claim 15 , wherein the cutting block is an adjustable cutting block that comprises a base and a cutting slot.
17. The medical navigation system for computer assisted surgery according to claim 15 , wherein the marker device comprises a plate, a marker holder and at least one marker sphere.
18. The medical navigation system for computer assisted surgery according to claim 15 , further comprising a computer with a processor, a stereoscopic camera and a pointer with a marker device at one end and a tip at another end.
19. The medical navigation system for computer assisted surgery according to claim 18 , further comprising a database of simple cutting blocks, each cutting block having a different position of the cutting slot.
20. The medical navigation system for computer assisted surgery according to claim 18 , wherein the computer has access to a model of an adjustable cutting block with a cutting slot and represents the effects of adjusting the position of the cutting slot.