Knee Alignment Device - Motion Lab Systems, Inc.
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1. required Shank rotation Repot O Patient El Static plantar flex distn g Parent Physician Static foot rolation o 2nd Physician Figure 2 A Session Form after a static trial was processed with KAD information Tibial torsion measurements were entered prior to processing the static trial The Cycles Window When the Stick figure displayed in the Cycles Window for the static trial collected with Knee Alignment Devices is displayed in the Cycles window the Knee Alignment Device markers are not shown Instead the virtual knee marker is plotted to allow its position to be checked Stick figures in Knee Alignment Device trials should therefore look exactly the same as in non Knee Alignment Device trials User Manual MLS Knee Alignment Device Processing Data in VCM e 15 e a e e amp e a 6 e e e L R Figure 3 A typical view in the VCM Cycles Window when a KAD is used Please refer to Checking for Errors in KAD Use on page 17 for more information about a trial with Knee Alignment Device information displayed in the Cycles Window User Manual MLS Knee Alignment Device Processing Data in VCM e 16 Checking for Errors in KAD Use The Static Trial Stick figures displayed in the Cycles Window for static trial data containing Knee Alignment Device information should look exactly the same as in non Knee Alignment Device trials because rather than the Knee Alignment Device markers only the vi2. the session form both cause the knee joint center to move Internal rotations of the knee flexion axis move the joint center posteriorly External rotations of the knee flexion axis move the joint center anteriorly There are three important related consequences a Ifa thigh marker is placed a long way anterior or posterior from its correct lateral position the application of thigh rotation offsets while still allowing a correct direction for the knee flexion axis will place the knee joint center too far posterior or anterior b This antero posterior mis location of the knee joint center causes small changes in the flexion extension axis of the knee c Knee joint moments which are calculated about the knee joint center will also change Knee Alignment Device Because of the difficulties associated with the basic method of establishing correct rotational alignment far more reliable results can generally be obtained by using the Knee Alignment Device KAD User Manual MLS Knee Alignment Device Joint Axis Determination e 11 Correct placement of the KAD is essential if hip rotation knee valgus varus and knee joint moments are to be calculated correctly This device is placed across the knee during a static subject calibration trial It allows the knee flexion axis to be measured directly independently of the thigh marker From this independent measurement VCM automatically calculated the Thigh Rotation Offset requi
3. User Manual Knee Alignment Device By Motion Lab Systems Inc Released May 6 1998 1 Printing revised June 21 2011 This manual or parts of it may be copied for use with the Knee Alignment Device manufactured by Motion Lab Systems if all copies contain this notice and all copyright notices This manual or parts thereof may not be used with Knee Alignment Devices manufactured by any other company and the descriptions within this manual may not apply to devices manufactured by other companies While every effort has been made to ensure that the information contained within this manual is accurate Motion Lab Systems Inc can not assume responsibility for any errors contained within this document The Motion Lab Systems Knee Alignment Device was developed by Motion Lab Systems Inc for use with the Newington Software and the VICON Clinical Manager program VICON Clinical Manager is a product of Oxford Metrics Ltd who can be contacted at 14 Minns Estate West Way Oxford England OX2 OJB Questions regarding the function and operation of the VICON Clinical Manager software should be directed to Oxford Metrics Ltd AMASS is a registered trademark of Adtech Adelphi Maryland USA VICON and VICON Clinical Manager are registered trademarks of Oxford Metrics Ltd UK Motion Lab Systems Inc 1998 2011 All Rights Reserved Printed in the United States of America Motion Lab Systems 15045 Old Hammond Highway Baton Ro
4. alue of Tibial torsion must be entered into the Session form before the static trial is processed User Manual MLS Knee Alignment Device Joint Axis Determination 12 If a negative value of Tibial Torsion is used then ankle plantar dorsiflexion axis is externally rotated as is normally required with respect to the knee flexion axis and the ankle joint center is moved anteriorly If a positive value of Tibial Torsion is used the ankle plantar dorsifexion axis is internally rotated with respect to the knee flexion axis and the ankle joint center is moved posteriorly If this method is used to establish an inter malleolar direction for the axis the ankle width should be measured obliquely between the malleoli On average using this method with 15 20 degrees of Tibial Torsion the ankle joint is 3 5 degrees plantarflexed by comparison with the parallel axes method Method C Alignment of the Shank wand with the Ankle Flexion Axis with or without KAD Whether or not the KAD is used to determine the knee flexion axis it is always possible to set up the rotational alignment of the ankle plantar dorsiflexion axis by the placement of the shank marker This may by useful as a direct means of incorporating the Tibial Torsion of a standing subject Especially when using a shank marker wand aligned directly above the inter malleolar axis of a standing subject this method may provide a more accurate way of setting true tibial torsi
5. arly some other corroboration is required The standard physical examination and test for hip rotation involves lying the subject prone flexing the knee to close to 90 degrees and moving the leg medially and laterally This test relies on the assumption true for many pathologies that as the foot is raised from the table the knee moves in pure flexion If the knee has any significant valgus varus instability hip rotation from this test will be unreliable If in the report graphs from a walking trial there is a hip external rotation offset AND a knee valgus wave during swing the knee flexion axis has been externally rotated The thigh marker was placed too far posteriorly b ahip internal rotation offset AND a knee valgus wave during swing the knee flexion axis has been internally rotated The thigh marker was placed too far anteriorly In case a the hip external rotation offset and the knee valgus wave are both corrected by entering a small internal ve Thigh Rotation Offset in the VCM Session form and reprocessing the walking trial In case b the hip internal rotation offset and the knee varus wave are both corrected by entering a small external ve Thigh Rotation Offset in the VCM Session form and reprocessing the walking trial Knee Joint Center Position Since the thigh rotation offset is applied about the knee joint marker changes in the placement of the thigh marker and thigh rotation offsets entered into
6. ds In this basic method the static trial is used only to establish the position of the forefoot marker relative to the alignment of the foot by temporarily adding a heel marker No corrections are made to the flexion axes of the knee and ankle Thigh and Tibial Markers The correct antero posterior alignment of the thigh and tibial markers is not an easy task If the knee and ankle flexion axes are incorrectly determined a number of highly characteristic errors will result in the kinematic results After learning to recognize these errors the operator can make mathematical adjustments which compensate for incorrect thigh and shank marker placement User Manual MLS Knee Alignment Device Joint Axis Determination e 10 Exactly the same assumption can be used with the VICON Clinical Manager to check for correct placement of the thigh marker and to correct offsets in hip rotation Recognizing Errors in Hip Rotation Hip rotation is measured about the long axis of the femur Its neutral position occurs when the flexion axis is aligned with the lateral axis of the pelvis If the thigh marker is placed too far forward the flexion axis of the knee is internally rotated and a corresponding internal rotation offset error appears in hip rotation It is almost impossible to obtain an independent measure of hip rotation in a standing subject so a non zero hip rotation may either be real or due to incorrect thigh marker placement Cle
7. e to or over the medial epicondyle ai When the knee is fully extended particularly in the adult knee the fibrous and fatty covering of the lateral joint capsule tends to push the lateral pad of the Knee Alignment Device forward internally rotating the measured knee flexion axis This must be avoided by adjusting the Knee Alignment Device position to reflect the correct knee axis wi The alignment of the Knee Alignment Device stem with the knee flexion axis must be thoroughly checked While the medial and lateral epicondyles of the knee provide a good approximation for the correct positions of the Knee Alignment Device pads in normal adult knees in abnormally shaped knees these landmarks may not represent the optimal positions for the pads User Manual MLS Knee Alignment Device KAD Placement e 4 wi The alignment of the Knee Alignment Device stem with the knee flexion axis must be thoroughly checked While the medial and lateral epicondyles of the knee provide a good approximation for the correct positions of the Knee Alignment Device pads in normal adult knees in abnormally shaped knees these landmarks may not represent the optimal positions for the pads wi Always check the position of the Knee Alignment Device immediately prior to data collection The Knee Alignment Device could slip if the subject moves between placing the device on the subjects knee and collecting the data If the Knee Alignment Device is not in the cor
8. ee flexion extension axis Any discrepancy between the two axes was corrected in the VCM model by entering in a measured value for tibial torsion usually obtained by direct manual measurement of the subject Tibial torsion could also be directly calculated by collecting a static trial with medial markers and using the Vicon BodyBuilder software to calculate the tibial torsion Marker Size The Vicon Workstation and Vicon Nexus software uses the KAD to define a virtual knee VKNE marker at the position where the plane containing the VKNE and the KD1 KD2 markers is also perpendicular to the line from the VKNE to the KAX marker This calculation has two mathematical solutions Plug in Gait assumes that KD1 is above KD2 to figure out the correct solution and orientation of the KAD in 3D space Using the VKNE Plug in Gait calculates the offset angle between the technical coordinate system defined by HJC THI VKNE and the anatomical coordinate system defined by HJC KJC and KAX The offset angle depends on the correct marker diameter not of markers on the KAD but of the marker that will be used on the knee and everywhere else in the dynamic The marker diameter to be used in the static processing is not the one used for the KAD markers but the one used for the ordinary marker set thus the KAD markers are not required to be the same size as the standard subject marker set as the VKNE marker size is defined by the fixed KAD dimensions and NOT by
9. er sufficiently flexible to allow several different methods to be used for calculation the kinematics of the ankle joint Method A Parallel Knee and Ankle Flexion Axes with KAD If a KAD is used to determine the knee flexion axis in a static subject calibration trial VCM will by default calculate a second axis with the same rotation about the long axis of the tibia as the knee flexion axis and passing through the ankle marker VCM automatically calculates a Shank Rotation Offset in exactly the same manner as the Thigh Rotation Offset and saves it in the Session form Plantar dorsiflexion measured about this axis corresponds most closely to ankle angle which is seen in a sagittal plane projection of the subject However it results in an ankle joint center which is directly medial to the lateral marker If this marker is placed on the lateral malleolus the joint center ends a long way posterior resulting in a kinematic dorsiflexion offset and an increase in plantarflexion moment One remedy to this problem is to place the ankle marker anterior to the lateral malleolus remembering to measure the ankle width correctly at this narrower point Method B Tibial Torsion between Knee and Ankle Flexion Axes with KAD If a KAD is used for the static subject calibration trial a value of Tibial Torsion can be used to alter the direction of the plantar dorsiflexion axis of the ankle and the location of the ankle joint center This v
10. ght thigh wand marker Left knee Right knee Left tibial wand marker Right tibial wand marker Left ankle Right ankle Left toe Right toe Left heel LKD1 LKD2 RKAX RKD1 RKD2 PELV Right heel Left knee axis Left knee device 1 Left knee device 2 Right knee axis Right knee device 1 Right knee device 2 dummy pelvis center The KAD specific marker names are shown in bold note that this format does not require a marker count at the top of the list Please call Oxford Metrics Ltd technical support if further instructions are required to add KAD labels to your MKR files or if you are in doubt about which file you should edit User Manual MLS Knee Alignment Device Editing the Appropriate Files 8 AMASS and VICON VX Systems DES files Following are the instructions to add marker labels to a DES file as used by AMASS and VICON VX AMASS Adtech Adelphi MD These commands are all issued from the VICON VX shell Please call Oxford Metrics Ltd technical support if further instructions are required 1 2 BON SON SIE is 2D 9 Enter the VICON shell by typing VIC at the VAX prompt Enter the Analysis Menu by typing A at the VICON Main Menu prompt Enter the Parameters Menu by typing P at the Analysis Menu prompt Select Update type U at the Parameters Menu prompt Type DES when the system asks for the file to update Type L P for List Point parameters at the file promp
11. he Knee Alignment Device will be incorrect Correct alignment of the knee flexion axis can be estimated in two manners First as mentioned above if care was taken to place the thigh wand in the plane defined by the knee flexion axis and the hip joint center then the calculated thigh rotation offset value should be minimal A value greater than 10 may signify misplacement of the Knee Alignment Device Secondly the knee varus valgus and hip rotation graphs from a dynamic trial can be used to determine Knee Alignment Device misplacement If in the report graphs from a walking trial there is e Hip external rotation offset AND a knee valgus wave during swing the knee flexion axis has been externally rotated The thigh marker was placed too far posteriorly e A hip internal rotation offset AND a knee varus wave during swing the knee flexion axis has been internally rotated The thigh marker was placed too far anteriorly User Manual MLS Knee Alignment Device Checking for Errors in KAD Use e 18 Hip Rotation Figure 6 These hip rotation values appear normal but the red line is suspect because of the knee varus graph Knee Valgus Varus 100 D 75 Gal Cycke Figure 7 The red line in this graph displays the knee varus wave during swing In the first case the hip external rotation offset and the knee valgus wave can both be corrected by entering a small internal positive Thigh Rotation Offset in the VICON Clin
12. ical Manager Session form and reprocessing the walking trial In the second case the hip internal rotation offset and the knee varus wave can both be corrected by entering a small external negative Thigh Rotation Offset in the VICON Clinical Manager Session form and reprocessing the trial Whenever the KAD is placed incorrectly you will see significant valgus varus values which on close examination tend to follow the knee flexion extension trace For normal gait the knee varus valgus graph should be relatively flat any deviation from this should alert you to the probability of errors in the alignments of KAD or the thigh marker wands User Manual MLS Knee Alignment Device Checking for Errors in KAD Use e 19 Using Vicon Nexus KAD usage with Vicon software The KAD axis is calculated by the Vicon Plug in Gait module using exactly the same code in both Vicon Workstation and Vicon Nexus In both Vicon Workstation and Vicon Nexus the KAD processing defines the knee coronal plane of the femur and relieves the user of the need to accurately place the Thigh Marker THI in the coronal plane of the femur An offset angle is calculated which from the intermediate coordinate system defined by HJC THI KNE is able to re create the anatomical coordinate system for the femur in the dynamic trials Tibial Torsion The original implementation of the KAD in Vicon Clinical Manager VCM assumed that the transmalleolar axis was parallel to the kn
13. ical Manager through the Marker group in the CFG file as lt L R gt KAX or KNE lt L R gt KD1 and lt L R gt KD2 Each Knee Alignment Device marker in the C3D file should have a unique marker label assigned to it However as there are no knee markers present during a Knee Alignment Device static trial the same label can be used for both the knee markers lt L R gt KNE and the Knee Alignment Device stem markers lt L R gt KAX Both assignments must be present in the Marker group in the CFG file When the VICON Clinical Manager software detects the presence of the Knee Alignment Device markers in a three dimensional data file it recognizes the presence of Knee Alignment Device s As knee markers cannot be present at the same time as Knee Alignment Device s the program assigns the shared labels to the Knee Alignment Device stem marker s Clearly it is important that the labels assigned to the other Knee Alignment Device markers lt L R gt KD1 and lt L R gt KD2 are not shared by any other markers User Manual MLS Knee Alignment Device Editing the Appropriate Files 6 Markers SACR sacr Sacral wand LASI lasi Left ASIS marker LTHI Ithi Left thigh wand LKNE lkne Left knee marker LTIB ltib Left shank wand LANK lank Left ankle marker LTOE Itoe Left toe marker RASI rasi Right ASIS marker RTHI rthi Right thigh wand RKNE rkne Right knee marker RTIB rtib Right shank wand RANK
14. ined ankle flexion axes will lie parallel to the knee flexion axes and will pass through the lateral malleolus marker For some individuals this is incorrect therefore this built in assumption may be overwritten if desired by entering the subject s tibial torsion measurement directly into the VICON Clinical Manager Session Form prior to processing the static trial causing VCM to rotate the ankle flexion axes during its kinematics calculations wi Please note that an external tibial torsion measurement must be entered into the VICON Clinical Manager Session Form as a negative value Repair of your KAD The Motion Lab Systems Inc KAD is a precision device that should give you many years of trouble free service However it is possible that it may become worn or damaged during use Please contact Motion Lab Systems for service or exchange of any damaged Knee Alignment Device User Manual MLS Knee Alignment Device Introduction e 3 KAD Placement Defining the Flexion Axis The placement of the Knee Alignment Device defines the flexion axis of the knee and the ankle for the VICON Clinical Manager software so correct positioning of the device is essential if these two axis are to be measured correctly by the VICON Clinical Manager The soft hollow outer pad of the Knee Alignment Device jaw is placed directly over the lateral surface intersection of the knee flexion axis and the inner pad is placed on the medial aspect of the knee clos
15. l a aia ain Marker SiE netii cad teenie User Manual MLS Knee Alignment Device Contents e 1 Introduction When to use a Knee Alignment Device The purpose of the Motion Lab Systems Knee Alignment Device also known as a KAD is to allow the VICON Clinical Manager software application from Oxford Metrics Ltd VCM to automatically establish the knee flexion axis during a static trial These devices are supplied in sets of two units each looking like the illustration below The devices are generally used in pairs one on each leg The Knee Alignment Device is a spring loaded metal jig that fits gently over the subjects knee while a static calibration data collection is performed The design of the Knee Alignment Device is such that the absolute distance between all three of the markers on the device is identical 5 66 inches The design of the Motion Lab Systems KAD enables the VICON Clinical Manager software to establish a virtual knee marker at the central joint of the Knee Alignment Device and this combined with the KAD wand marker enables the knee flexion axis to be measured User Manual MLS Knee Alignment Device Introduction e 2 A C3D Coordinate 3d Data file contains the 3D marker locations of the KAD and other subject markers When the VICON Clinical Manager software finds marker labels for a Knee Alignment Device defined in the C3D file it uses the orientation of the three markers on the Knee Align
16. les used with 370 software version 2 01 or lower use the first format MKR 1 format while the 2 5 version of the 370 software current at the time of writing uses the MKR 2 format Make sure that you are using the correct format The following is a sample MKR file as used by 370 software version 2 01 and lower MKR 1 19 SACR Sacral wand marker LASI Left ASIS LTHI Left thigh wand marker User Manual MLS Knee Alignment Device Editing the Appropriate Files 7 j Hy nw eA v9 w Z RWAHHE ve Hi O zi zo jam Left knee Left tibial wand marker Left ankle Left toe Right ASIS Right thigh wand marker Right knee Right tibial wand marker Right ankle Right toe Left heel Right heel LKD2 Right top Knee Alignment Device marker Right bottom Knee Alignment Device marker Left top Knee Alignment Device marker Left bottom Knee Alignment Device marker The KAD specific marker names are shown in bold note that if you add marker names to this format then you must change the marker count at the top of the list In this example there are 19 marker lines and the count is set to 19 The following is a sample MKR file as used by 370 software version 2 5 MKR 2 Labels List SACR LASI RASI LTHI RTH J ci NON UNH ye H O O j W vs jan Sacral wand marker Left ASIS Right ASIS Left thigh wand marker Ri
17. ment Device to establish the knee flexion axis After the knee flexion axis has been established VICON Clinical Manager calculates the relative transverse alignment of this axis to the transverse plane orientation of the thigh and shank as calculated using the mid thigh and mid shank stick markers These relative alignments are stored in the subject s Session form as Thigh and Shank Rotations and are applied to all dynamic data within the session Thus the correct alignment of the thigh and shank wands becomes less critical as any minor alignment errors are measured during the static trial and can be automatically removed during the processing of the dynamic trials Please refer directly to the Oxford Metrics VCM User Guide or contact the manufacturer for information on the kinematic processing that is performed within the VICON Clinical manager software program wi A Knee Alignment Device should be used only during a static trial The thigh and shank rotation offset values calculated in VICON Clinical Manager are used to align the knee and ankle flexion axes during the dynamic trials Please do not attempt to use the Knee Alignment Device during a dynamic or walking trial as it has not been designed to be worn while the subject is walking The KAD Environment When a Knee Alignment Device is used during a static trial the VICON Clinical Manager software assumes that the knee and ankle flexion axes are parallel The Knee Alignment Device def
18. on into the alignment of the plantar dorsiflexion axis Leaving Tibial Torsion to zero process a static trial with the KAD in the normal way After the program has saved the rotation offsets in the Session form reset the Shank Rotation Offset to zero before processing any walking trials As with the previous method if the axis is set up with an inter malleolar alignment the ankle width should be measured obliquely between the malleoli On average using this method introduces the equivalent of more than 20 degrees of Tibial Torsion and the ankle joint is 5 7 degrees plantarflexed by comparison with the parallel axes method If Knee Rotation is required as a VCM report graph it may include an offset due to the non alignment of knee and ankle axes This offset can be reduced by entering a value of Tibial Torsion into the Session form after processing of the static trial No variable other than Knee Rotation is affected Method D Foot Aligned Ankle Flexion Axis with or without KAD The last model method is radically different from the three previous The Grood and Suntay convention for joint articulation fixes the flexion axis in the segment proximal to a joint However once the location of the ankle joint center has been established using any of the above methods it is possible for VCM to establish a plane which lies through the knee and ankle joint centers and the forefoot marker The axis for plantar dorsiflexion can then be se
19. rank Right ankle marker RTOE rtoe Right toe marker LHEE lhee Left heel marker static only RHEE rhee Right heel marker static only LKAX Ikne Left knee axis stick Knee Alignment Device static only LKD1 Ikd1 Left knee wand marker 1 Knee Alignment Device static only LKD2 Ikd2 Left knee wand marker 2 Knee Alignment Device static only RKAX rkne Right knee axis stick Knee Alignment Device static only RKD1 rkd1 Right knee wand marker 1 Knee Alignment Device static only RKD2 rkd2 Right knee wand marker 2 Knee Alignment Device static only Marker Definition DES or MKR File The marker labels used to define the Knee Alignment Device markers must be present in the VICON marker definition files Depending on the system that you are using these will be either DES files AMASS and VICON VX motion capture systems or MKR files VICON 370 motion capture systems VICON 370 Systems MKR files The MKR file used in conjunction with the VICON 370 system is an ASCII file that is usually stored in the 370 MODELS directory for older 370 systems or in the VICON CFG directory in many of the newer 370 systems Locate and open this file using the NOTEPAD application and check that the correct labels exist You many need to add the marker label names if they are not present These labels must match those used in the VICON Clinical Manager CFG file There are two slightly different formats for this file fi
20. rect position during a static trial there is no way to correct the data acceptably User Manual MLS Knee Alignment Device KAD Placement e 5 Editing the Appropriate Files Configuration Files lt L R gt means either Left or Right side markers In most cases your motion capture system will have been set up with the correct configuration files when it was installed If this is the case then you can probably skip this chapter This section is useful for anyone installing a copy of VICON Clinical Manager themselves anyone who did not purchase the Knee Alignment Device at the same time as VICON Clinical manager or anyone who is upgrading their data collection system Before you can process data collected with the Motion Lab Systems Knee Alignment Device you must first configure your data collection system as well as your copy of the VICON Clinical Manager software so that it knows what marker labels you will be using to identify the Knee Alignment Device markers This information will usually need to be entered in two places Once in the VICON Clinical Manager configuration file CFG File and again in your motion capture systems Marker Definition file MRK or DES file It is most important that you take care to use identical marker labels and names in both files otherwise the system will not work VICON Clinical Manager CFG file In general the three markers on each Knee Alignment Device are identified internally by VICON Clin
21. red to correct for any misplacement of the thigh marker and saves the offset in the Session form Over reliance on anatomical landmarks can be misleading The only safe method is to examine the knee as it is flexed and extended and to mark the skin at the medial and lateral points which are seen to remain in a constant position relative to both the thigh and shank a task that requires practice The KAD pads are then placed over these marks When the knee is fully extended particularly in the adult knee the fibrous and fatty covering of the lateral joint capsule tends to push the lateral pad of the KAD forward internally rotating the measured knee flexion axis This must be avoided by adjusting the KAD position During a static trial using a KAD the subject s hip flexion abduction and rotation knee flexion are not important only the correct alignment of the KAD relative to the knee joint axis will ensure that reports from the session s trials are accurate Ankle Joint Kinematics You need to consider what is meant by the common phrase plantar dorsiflexion at the ankle If the subject stands with the long axis of the foot aligned directly antero posterior is the plantar dorsiflexion axis lateral through the lateral malleolus or is it aligned between the medial and lateral malleoli Or is it somewhere else The compound joint between the tibia and hindfoot is only approximated by the relatively simple model in VCM The model is howev
22. rtual knee marker is displayed If the stick figure looks bowlegged and or displays the knee joint center lateral to the knee marker either the markers were labeled incorrectly or the markers are defined incorrectly in the VICON Clinical Manager CFG file If this information is correct please contact Oxford Metrics technical support for assistance with VICON Clinical Manager L R Figure 4 When the KAD markers are labeled incorrectly the VICON Clinical Manager Cycles Window displays the joint centers lateral to their true position User Manual MLS Knee Alignment Device Checking for Errors in KAD Use e 17 e a e e amp e a 6 e e e L R Figure 5 Only the knee marker of a KAD is displayed in the VICON Clinical Manager Cycles Window when a KAD is used If care was taken to place the thigh wand in the plane defined by the knee flexion axis and the hip joint center then the calculated thigh rotation offset value can also be used to indicate misplacement of the Knee Alignment Device If care was taken during the thigh wand marker placement then the thigh rotation offset value should be minimal A value greater than 10 may signify misplacement of the Knee Alignment Device If this is true please continue to the Dynamic Trial section The Dynamic walking Trial It is possible to place the Knee Alignment Device incorrectly or for it to slip prior to data collection In either case the knee flexion axis defined by t
23. t Type C LA for Change Labels Press the Return key until the marker label is not displayed after the prompt At this point enter RKD1 and press Enter Enter RKD2 and press Enter 10 Enter LKD1 and press Enter 11 Enter LKD2 and press enter User Manual MLS Knee Alignment Device Editing the Appropriate Files 9 Joint Axis Determination Using VICON Clinical Manager The VICON Clinical Manager software provides a number of alternative methods for determining the axes of the knee and ankle joints Basic Rotation Alignments In the most basic method the rotations of these axes about the long axes of the femur and tibia are determined by the placement of markers on the mid thigh and mid shank As the fixation of any one of these markers is moved anteriorly around the limb there is an interior rotation of the flexion axis of the joint which lies below it This rotation always occurs about the marker placed on the lateral side of the joint so the flexion axis always passes through this joint marker giving the operator complete control over both the direction of the flexion axis and the center of the joint Note that the height and distance from the limb of these rotation sensing markers has no effect on the results Provided their antero posterior location relative to the distal joint marker is carefully controlled they can be placed wherever visibility and steady fixation to the limb are optimal with or without wan
24. t perpendicular to this plane passing through the ankle joint center This redefined flexion axis is of course not fixed relative to the rotation of the tibia so tibial torsion has no effect However extreme the internal or external rotation of the foot downward movements of the toe are always treated as plantarflexion and upward movements as dorsiflexion This measure of ankle plantar dorsiflexion can be calculated in addition to normal ankle flexion by calling up an extra GCD variable FootBasedDorsiPlanFlex see documentation supplied with the VICON Clinical Manager software for details User Manual MLS Knee Alignment Device Joint Axis Determination 13 Processing Data in VCM I Used a KAD Now What The Session Form Once a static trial is collected it must be processed by the VICON Clinical Manager software so that the information about the relative positions of the markers can be determined A Knee Alignment Device static trial is processed in the same manner as a Static trial that does not contain KAD information There are only the following two differences between the methods 1 A tibial torsion measurement may be included in the Session Form prior to processing a static trial that contains Knee Alignment Device information 2 When the static trial is processed Thigh and Shank Rotations values other than 0 0 are stored in the Session database and displayed in the Session form The thigh rotation offset value is
25. the angular difference between the transverse alignments of the knee flexion axis defined by the Knee Alignment Device versus the transverse plane of the thigh as defined using the thigh wand Session 3 Trials Patiert No Last name first name s Session no Session dae Age Height Wright Inter ASIS dislance om a Left Pigh Maker diarmm Frame Rate Config file splenic Thigh rotation Date Repot required Shank rotation Repot O Patient disn g Parent o Physician Static olantar flex Static foot rolation o 2nd Physician Figure 1 A Session Form after a static trial was processed with KAD information User Manual MLS Knee Alignment Device Processing Data in VCM e 14 The shank rotation offset value is the angular difference between the transverse alignments of the knee flexion axis defined by the Knee Alignment Device versus the transverse plane of the shank as defined using the shank wand If tibial torsion measurements are entered into the Session Form prior to processing a trial the shank rotation offset value is calculated taking the values into account Session 3 Trials T Patiert No Last name first name s Session no Session dae Age Height Weight Ca S E C Let ight inter ASIS distance om _ acistotroc dist eae dia i Frame Rac m Leglength em eo 1E e lE Knee width er ontig fi gaki el r Tibial torsion Videotape Reference a EAT Ln Thigh rotation Date Repor
26. the subject marker dimensions User Manual MLS Knee Alignment Device Using Vicon Nexus e 20
27. uge Louisiana 70816 1 225 272 7364 support motion labs com http www motion labs com Contents Introduction When to use a Knee Alignment Device eeeseeeseeesneeeeeeeeees The KAD Environments iesiri aai Repair of your KAD ourer poa aaa ae a T a oad KAD Placement Defining the Flexion AXiS eceesceeeseceseeeeseeeenceceneeceneeseneeeses Editing the Appropriate Files Configuration Pues titis nis nana ttt aiken eal aeianiens VICON Clinical Manager CFG file ee Marker Definition DES or MKR File Joint Axis Determination Using VICON Clinical Manager 0 eee cece eee eeeeeeeeeees Basic Rotation Alignment cescesceeeseeeseeeeeeeeeneees Thigh and Tibial Markers 00 0 eceeeeeeesceceseeeeseeeneeeeees Recognizing Errors in Hip Rotation eeeeeeeeeeeeeee Knee Joint Center Position eee eeeeeeeseeeteeeeees Knee Alignment Device 0 cee ceesceesceeeeneeeneeeeeeeeeeees Ankle Joint Kinematics 2 0 0 eee eeeeseeseeseeeseeeeeeees Processing Data in VCM T Used a KAD Now What hnknin rt aarre THE SESSiOMN FORM ccc5cki et nannan he Sane a The Cycles Window siienrornanned eriat Checking for Errors in KAD Use The Static Vial kepe steeds ates Ane hates ee eae haetida bias ts The Dynamic walking Trial 0 0 cee eesceeesceeesneceeeeeeseeeeeeeeees Using Vicon Nexus KAD usage with Vicon software ceeccesseceseeeeseeeneeeesneeeeees Tibial TOS Oi nenaon e
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