Medacta International SA
Strada Regina
Phone +41 91 696 60 60
***************
99.29.14g e n  r e v .06 – L a s t  u p d a t e  D e c e m b e r  2017
TABLE OF CONTENTS
1Introduction (3)
2Standard Considerations (3)
3Patient position and stabilization (4)
3.1Ankle (4)
3.2Knee (4)
3.3Hip (5)
4Image Requirements (5)
5Scanning Parameters (6)
5.1Ankle and Hip (6)
5.2Knee (6)
5.3Suggested Parameters for All MRI Machines (7)
5.4Additional Scanning Suggestions (8)
6Image Acquisition (9)
6.1Ankle Imaging (9)
6.2Knee Imaging (9)
6.3Hip Imaging (11)
6.4Final Check (11)
7Uploading Images to the MyKnee Website (12)
8Examples of Acceptable MRI Series for the Knee (14)
9Examples of Not Acceptable MRI Series of the Knee (14)
1Introduction
This document describes the guidelines that radiology centers must adhere to when performing MRI scans as required by Medacta International SA so the MyKnee® patient specific cutting blocks can be manufactured. MyKnee patient specific cutting blocks are used to facilitate the implantation of a Medacta total knee prosthesis. The directives outlined in this document are intended to help improve the quality of the submitted MRI scans and reduce imaging failures.
It is the responsibility of the radiology center to manage their MRI machine’s specific protocol setting
s. Medacta International SA highly recommends that before scanning a patient for an official case, the radiology center should perform a DEMO scan to ensure the parameters are correct. For additional information about this procedure, please refer to the “MyKnee WebPortal - How To Manual” (ref. 99.MYK.1HT).All modifications made to this protocol are to be discussed with and approved by Medacta International SA in advance.
For more information, please contact Medacta International SA at ********************.
2Standard Considerations
Scans must be performed up to 7 months before the surgery. Images will be considered expired if the surgery will take place more than 7 months later the MRI exam.
It is a requirement that a MRI machine have the following features:
1.  A magnetic field of 1.5 T or bigger.
2.The ability to use a receive-only knee coil or a flexible receive-only coil for the scan of the
knee joint.
3.The ability to have all three series (axial hip, sagittal knee, axial ankle) in the same frame of
reference.
Please bear in mind that there is a strong risk of MRI scan rejection in the following cases:
1.patients not able to stand still in supine position during acquisition phase
2.patients having implants or other metallic devices into the hip or ankle of the leg that has
to undergo knee replacement.
In such cases, we highly suggest to avoid MRI and switch to a CT scan. Caution: please, always avoid MRI and switch to a CT scan in case of patients having implants or other metallic devices into the knee being operated.
If the patient has an implant or any other metallic device in the contralateral limb, the MRI scan can be accepted ONLY if the resulting images of the knee are not affected by metallic artefact. Otherwise, a CT scan has to be performed.
move off
3Patient position and stabilization
The patient must be in supine position, as close as possible to the isocenter, without running out of space on the body coil.
MRI technicians are recommended to inform the patients about what the exam consists on and what indications the patients are asked to follow during the scan. Well-informed patients generally result in good and conforming images.
3.1Ankle
Place a small sponge (3-4 cm) under the ankle and use sandbags around the malleoli to secure the ankle into the proper anterior/posterior position. Put tape across the ankle (silk tape is recommended), stretching it from one side of the table to the other side, to secure the placement of the sandbags and ankle. This procedure will limit the patient’s ability to move the ankle during the scan.
3.2Knee
First, wrap the diseased knee with the coil. You want to wrap the coil as tight as possible; use tape to secure the coil if necessary. If the knee is too large for the coil to completely wrap around, place the opening on either the medial or lateral side of the knee. You want to ensure the coil has the best coverage anteriorly and posteriorly.
For patient comfort, place two small sponges (3-4 cm)
under the patient’s knee being scanned.
This will be especially helpful for those patients who are externally rotated and getting their knee to la
y completely flat is impossible. Place an additional small sponge under the opposite leg for extra comfort. Put tape across the knee, stretching it from one side of the table to the other, to secure the wrapped knee in place. This will limit the patient’s ability to move the knee during the scan. The image below show the suggested set-up.
3.3 Hip
Ensure the patient’s arms are not near the hip area. The images below show the suggested two possible positions for the patient’s arms.
4 Image Requirements
Images of the hip, knee and ankle must include the following:
▪ Hip : The whole femoral head and at least 10 cm of proximal femur must be included.
▪ Knee : The distal femur, proximal tibia and proximal fibula are required. The FOV must be set so that approximately 7 cm of the distal part of the femur and approximately 5 cm of the proximal part of the tibia are clearly demonstrated.
▪ Ankle : Both of the malleoli must be included. The series must cover at least 5 cm of the distal tibia.

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