Surgical power drill including a measuring unit suitable for bone screw length determination
View Patent ↗A device ( 25 ) for drilling holes in bone and configured to determine bone screw length, the device ( 25 ) including a surgical power drill ( 2 ) comprising: a) a housing ( 12 ) and; b) a measuring device ( 1 ) releasably attached or fixed to the housing ( 12 ), wherein the measuring device ( 1 ) is configured to measure the distance (x) covered by the housing ( 12 ) in the direction of the longitudinal axis ( 7 ) and relative to a surface of an implant ( 26 ) or a bone during a drilling process, wherein the measuring device ( 1 ) comprises a processing unit ( 14 ) to record the distance (x) covered with respect to time; the processing unit ( 14 ) comprises one or more differentiators to determine at least the first and second derivatives of the distance (x) covered with respect to time; and the processing unit ( 14 ) further comprises a peak detector to analyze one or more peaks occurring in the graph of the highest derivative with respect to time, and wherein the measuring device ( 1 ) comprises a laser device or an ultrasound position sensor for displacement assessment.
1. A method for analyzing a bone drilling operation, the method comprising steps of:
advancing a drill bit of a surgical power drill into a bone along a drilling direction so as to drill a hole in the bone and;
during the advancing step, measuring a position of a cutting tip of the drill bit along the drilling direction with respect to time, the position of the cutting tip being measured relative to one of 1) a surface of the bone and 2) a surface of an implant;
determining at least first and second derivatives of the position versus time, so as to determine velocity, acceleration, respectively, versus time; and
identifying one or more peaks of a highest one of the derivatives with respect to time so as to determine that the cutting tip has exited a cortex of the bone.
2. The method of claim 1 , wherein the measuring step is a contactless measuring step.
3. The method of claim 2 , wherein the measuring step comprises actuating one of a laser device and an ultrasound position sensor so as to measure the position of the cutting tip.
4. The method of claim 2 , further comprising the step of performing laser triangulation so as to perform the measuring step.
5. The method of claim 1 , wherein the step of determining at least the first and second derivatives is performed in real time.
6. The method of claim 1 , further comprising the step of determining a relative position between a first member that is fixed to a housing of a surgical drill that includes the drill bit, and a second member which is displaceable along a longitudinal direction that includes the drilling direction when it has been determined that the cutting tip has exited the cortex of the bone.
7. The method of claim 6 , further comprising the step of selecting a bone screw having a length corresponding to the relative position between the second member and the first member.
8. The method of claim 6 , further comprising the step of frictionally fitting a clamping portion of the second member to the drill bit.
9. The method of claim 6 , further comprising:
positioning the surgical power drill relative to the bone so that a front end of the second member and the cutting tip of the drill bit abut the surface of the bone; and
storing a relative position from the positioning step as a starting point for measurement of a position of the cutting tip relative to the surface of the bone in the drilling direction with respect to time.
10. The method of claim 1 , further comprising the step of identifying an acceleration peak when a maximum value of determined acceleration exceeds a predefined threshold value.
11. The method of claim 1 , wherein the cortex comprises a near cortex of the bone.
12. The method of claim 1 , wherein the cortex comprises a far cortex of the bone.
13. The method of claim 1 , further comprising the step of determining a third derivative of the position versus time, so as to determine jerk versus time.
14. The method of claim 13 , further comprising the step of identifying a jerk peak of the jerk so as to determine that the cutting tip has exited the cortex of the bone during the advancing step.
15. The method of claim 14 , wherein the step of identifying the jerk peak occurs when a maximum value of the jerk versus time exceeds a predefined threshold value.
16. The method of claim 14 , wherein the cortex comprises a near cortex of the bone.
17. The method of claim 14 , wherein the cortex comprises a far cortex of the bone.