Target Outcome
Prerequisites
Infrastructure
For more details see ["Infrastructure/ExperimentationMechanics"].
Previous Protocols
For more details see ["Specifications/Specimens"].
For more details see ["Specifications/ExperimentationAnatomicalImaging"]
For more details see ["Specifications/Registration"].
For more details see ["Specifications/ExperimentationJointMechanics"].
Protocols
Joint Testing Preparation
Initial Specimen Preparation
- Obtain specimens based on ["Specifications/Specimens"]
- Full leg should be procured (foot to femoral head)
- The specimen should be thawed for 12-18 hours prior to specimen preparation at room temperature
- Specimen demographics (e.g., age, height, weight, race etc) will be recorded.
- Remove all soft tissue on the femur side proximal to 5 inches from the epicondylar axis
- Remove all soft tissue on the tibia side distal to 4 inches from the epicondylar axis
Optoelectronic Marker Mounting
The use of an optoelectronic camera system (Optotrak, Northern Digital Inc., Waterloo, Ontario, Canada) requires repeatable placement of the orthopedic research pin markers http://www.ndigital.com/lifesciences/spineresearchpins.php
- In order to ensure repeatable placement, brass (MRI compatible) fixtures were designed to be rigidly secured to the tibia and femur throughout experimentation.
- The fixtures are composed of:
- A threaded brass plug attached to the bone through the use of three brass screws. Bone cement is used to ensure purchase between the screws and bone.
- A second brass fixture that can be securely screwed onto the plug through the used of two pins in a repeatable fashion.
attachment:optotrak_mounting_assembly.png
- The centers of the fixtures should be mounted on the:
- Tibia - ~5 inches from the epicondylar axis
- attachment:tibia_optotrak_mount.png
- Femur - ~6 inches from the epicondylar axis
- attachment:femur_optotrak_mount.png
- Patella - on the center of the patella
- Tibia - ~5 inches from the epicondylar axis
MRI Registration Marker Mounting
Tibia and Femur
- Three spherical markers should be rigidly mounted to the tibia and the femur as close to joint line as possible without damaging ligamentous structures (~50-60 mm)
- Tibia spheres should be mounted on the medial, lateral, posterior sides of the bone.
- Femur spheres should be mounted on the anterior, medial, lateral sides of the bone.
attachment:knee_with_registration_markers.png
- Spherical markers are hollow plastic spheres (10 mm radius ) filled with water based gel and are attached to the bones using plastic screws for the tibia and femur for MRI registration.
attachment:spherical_marker.png Anchor(Patella_MRI_marker)
Patella
- MRI [:Specifications/Registration#Patella_Registration:patella registration] consists of a 3D printed attachment with three resin filled spheres. There are six divots on the attachment that can be used to register where the spheres are with respect to the attachment.
- The MRI registration attachment is mounted to the patella using the same [:Specifications/SpecimenPreparation#Marker_Mounting:fixture] used to mount the optoelectronic markers.
attachment:patella_registration.png
Specimen Digitization/Registration Procedure
MRI Compatible Markers
- Patella
- The digitization of points and the registration of the [:Specifications/Registration#Patella_MRI_CS:patella MRI marker coordinate system] can be done prior to specimen preparation.
- The plug of the optoelectronic marker [:Specifications/SpecimenPreparation#Marker_Mounting:fixture] should be rigidly secured to a piece of wood that is fixed in space.
- The patella optoelectronic marker should be secured to the plug and the position/orientation data should be recorded to identify where the sensor is in space
- The [:Specifications/SpecimenPreparation#Patella_MRI_marker:patella MRI registration marker] attachment should be mounted on the plug and the 6 divots should be digitized using the digitizing probe.
attachment:digitizing_probe.png
Anatomical Landmarks
After the [:Specifications/SpecimenPreparation#Marker_Mounting:optoelectronic markers] have been secured to the specimen, the anatomical landmarks can be digitized with respect to the markers.
A digitizing probe should be used to take each point with respect to the bone's respective marker.
- The [:Specifications/Registration#Tibia_CS:tibia coordinate system] requires the digitization of the following points
- T1. Medial tibial plateau
- T2. Lateral tibial plateau
- T3. Medial malleolus of the tibia
- T4. Lateral malleolus of the fibula
- The [:Specifications/Registration#Femur_CS:femur coordinate system] requires the digitization of the following points
- F1. Lateral epicondyle of the femur
- F2. Medial epicondyle of the femur
- F3-F6. 4 points around the epiphyseal line of the femur
- The [:Specifications/Registration#Patella_CS:patella coordinate system] requires the digitization of the following points
- P1. Most lateral point
- P2. Most medial point
- P3. Most superior point
- P4. Most inferior point
Tissue testing sample preparation
Dissection
Tissue sample punches
Vibratome
Sample labelling