SYSTEM AND METHOD FOR MEASURING MUSCULAR-SKELETAL ALIGNMENT TO A MECHANICAL AXIS

• US 20140276885A1
• Filed: 09/13/2013
• Published: 09/18/2014
• Est. Priority Date: 03/18/2013
• Status: Active Grant

• Current Assignee: Howmedica Osteonics Corp. (Stryker Corporation)
• Original Assignee: OrthoSensor, Inc (Stryker Corporation)
• Inventors: Stein, Marc, Roche, Martin
• Granted Patent: US 9,492,238 B2
• Time in Patent Office: Days
• US Class Current: 606/102
• CPC Class Codes: A61B 17/154 for preparing bone for knee prosthesis
• CPC Class Codes: A61B 17/155 Cutting femur
• CPC Class Codes: A61B 17/157 Cutting tibia
• CPC Class Codes: A61B 17/1764 for the knee
• CPC Class Codes: A61B 2034/102 Modelling of surgical devices, implants or prosthesis
• CPC Class Codes: A61B 2034/104 Modelling the effect of the tool, e.g. the effect of an implanted prosthesis or for predicting the effect of ablation or burring
• CPC Class Codes: A61B 2034/105 Modelling of the patient, e.g. for ligaments or bones
• CPC Class Codes: A61B 34/10 Computer-aided planning, simulation or modelling of surgical operations
• CPC Class Codes: A61B 34/20 Surgical navigation systems; Devices for tracking or guiding surgical instruments, e.g. for frameless stereotaxis
• CPC Class Codes: A61B 34/25 User interfaces for surgical systems
• CPC Class Codes: A61B 5/103 Detecting, measuring or recording devices for testing the shape, pattern, colour, size or movement of the body or parts thereof, for diagnostic purposes A61B5/08 takes precedence; measuring aids for tailors A41H1/00; measuring instruments specially adapted for dentistry A61C19/04
• CPC Class Codes: A61B 5/1036 Measuring load distribution, e.g. podologic studies
• CPC Class Codes: A61B 5/1072 measuring distances on the body, e.g. measuring length, height or thickness A61B5/1076 takes precedence
• CPC Class Codes: A61B 5/1121 Determining geometric values, e.g. centre of rotation or angular range of movement
• CPC Class Codes: A61B 5/45 For evaluating or diagnosing the musculoskeletal system or teeth A61B5/1036, A61B5/1074, A61B7/006 take precedence
• CPC Class Codes: A61B 5/4528 Joints A61B5/4533, A61B5/4538 take precedence
• CPC Class Codes: A61B 5/4571 Evaluating the hip
• CPC Class Codes: A61B 5/4585 Evaluating the knee
• CPC Class Codes: A61B 5/4851 Prosthesis assessment or monitoring
• CPC Class Codes: A61B 5/4887 Locating particular structures in or on the body
• CPC Class Codes: A61B 5/686 : Permanently implanted devices, e.g. pacemakers, other stimulators, biochips A61B5/6861 takes precedence
• CPC Class Codes: A61B 90/37 : Surgical systems with images on a monitor during operation
• CPC Class Codes: A61F 2/38 : for elbows or knees
• CPC Class Codes: A61F 2/3836 : Special connection between upper and lower leg, e.g. constrained
• CPC Class Codes: A61F 2/461 : of knees
• CPC Class Codes: A61F 2/4657 : Measuring instruments used for implanting artificial joints for surgical instruments A61B90/06
• CPC Class Codes: A61F 2/4684 : Trial or dummy prostheses
• CPC Class Codes: A61F 2002/4658 : for measuring dimensions, e.g. length
• CPC Class Codes: A61F 2002/4668 : for measuring angles
• CPC Class Codes: G06F 3/0481 : based on specific properties of the displayed interaction object or a metaphor-based environment, e.g. interaction with desktop elements like windows or icons, or assisted by a cursor's changing behaviour or appearance

Abstract

A system and method is disclosed herein for measuring alignment of the muscular-skeletal system. The system comprises a sensored module that can be placed within a prosthetic component to measure load, position of load, and joint alignment. The system further includes a remote system for receiving, processing, and displaying quantitative measurements from the sensors. Alignment relative to a mechanical axis is measured. In a two bone system with a joint therebetween the total alignment measured comprises offsets measured for each bone. The joint is placed in a predetermined flexion that supports measurement of the joint as it is moved. The joint pivots on a point that is along the mechanical axis. Points along the arc made by the joint rotating between a first and second point are measured. An arc maximum is determined. The arc maximum is then converted to varus or valgus offset relative to the mechanical axis.

Claims

1. A method of measuring alignment to a mechanical axis comprising the steps of:

positioning a joint to a first target flexion value;

rotating the joint between a first point and a second point where the first and second points are on opposing sides of the joint;

calculating an alignment value of a first bone relative to the mechanical axis;

positioning the joint to a second target flexion value;

rotating the joint about a third point and a fourth point where the third and fourth points are on opposite sides of the joint;

calculating an alignment value of a second bone relative to the mechanical axis; and

calculating alignment relative to a mechanical axis of the first and second bones.

2. The method of claim 1 further including a step of rotating the joint between the first and second points from a first pivot point.

3. The method of claim 2 further including a step of rotating the joint between the third and fourth points from a second pivot point where the first and second pivot points differ.

4. The method of claim 1 further including a step of zeroing the sensor module to a first reference plane and a second reference plane.

5. The method of claim 1 further including a step of positioning the joint at approximately a 45 degree angle when pivoting on the first pivot point where a sensored module configured to measure parameters of the muscular-skeletal system resides in a prosthetic component of the joint.

6. The method of claim 5 further including the steps of:

rotating the joint between the first and second points at least two times;

measuring points of an arc generated as the joint is moved between the first and second points; and

determining a maximum of the arc.

7. The method of claim 6 further including the steps of:

calculating a tilt value of a bone cut of the first bone;

converting the tilt value to a varus or valgus number in relation to a mechanical axis the joint for the first bone.

8. The method of claim 7 further including a step of positioning the joint where the sensor module is at approximately 45 degree angle when pivoting on the second pivot point.

9. The method of claim 8 further including the steps of:

calculating a tilt value of a bone cut of the second bone;

converting the tilt value to a varus or valgus number in relation to a mechanical axis of the joint for the second bone.

10. The method of claim 9 further including a step of subtracting the varus or valgus number of the second bone from the varus or valgus number of the first bone to calculate the alignment of the first and second bones to the mechanical axis.

11. A method of measuring alignment of a tibia to a mechanical axis of a leg comprising the steps of:

placing a heel of a leg in an approximately fixed location;

positioning a knee joint to a target flexion value;

rotating the knee joint between a first point and a second point, where the first and second points are respectively on a medial and lateral side of the knee joint, and where the knee joint is pivoting on the heal of the leg during rotation;

measuring points along an arc made by the knee joint as the knee joint is moved between the first and second points; and

calculating an alignment value of the tibia relative to the mechanical axis.

12. The method of claim 11 further including a step of maintaining an ankle in a fixed position relative to the heel.

13. The method of claim 11 further including a step of positioning the knee joint where a sensored module in a prosthetic component of the knee joint is at approximately a 45 degree angle.

14. The method of claim 11 further including the steps of:

rotating the knee joint between the first and second points at least two times;

measuring points along an arc of the anterior-posterior axis of the knee joint during rotation; and

determining an arc maximum.

15. The method of claim 14 further including the steps of:

calculating a tilt value along a medial-lateral line of a proximal end of the tibia;

converting the tilt value to a varus or valgus number in relation to a mechanical axis of the leg for the tibia.

16. A method of measuring alignment of a femur comprising the steps of:

positioning a knee joint to a target flexion value;

rotating the knee joint between a first point and a second point, where the first and second points are respectively on a medial and lateral side of the knee joint, where the knee joint is pivoting on a hip joint of the leg during rotation; and

calculating an alignment value of the femur relative to the mechanical axis.

17. The method of claim 16 further including a step of positioning the knee joint where a sensored module in a prosthetic component of the knee joint is at approximately a 45 degree angle.

18. The method of claim 17 further including a step of holding the leg in approximately extension.

19. The method of claim 16 further including the steps of:

rotating the knee joint between the first and second points at least two times where the sensored module is coupled to a distal end of the femur;

measuring data points along an arc of the anterior-posterior axis of the knee joint during rotation; and

determining an arc maximum.

20. The method of claim 19 further including the steps of:

calculating a tilt value along a medial-lateral line of a distal end of the femur;

converting the tilt value to a varus or valgus number in relation to a mechanical axis of the leg for the femur.