During classical osteotomy techniques, it is very difficult to achieve exactly the defined preoperative objective planned over X-Rays.The lack of exact intraoperative real time control of the mechanical axis often results in post-operative malalignments, which is one reason for poor long term results. These problems can be addressed by using computer assisted surgery but are expensive and elaborate systems.
Osteotomy AR app is an App and that merges the operative field with Augmented Reality and offers intraoperative assisted quidance during Osteotomies. After intraoperative registration app offers in AR:
After intraoperative registration app offers in AR:
- real time measurement of the deformities, navigational guidance of correction, and planning of the osteotomy. The osteotomy wedge size, joint line orientation, and tibial plateau slope are monitored.
-in real time the result of changing parameters, eg, the orientation of the osteotomy plane. The angle of the osteotomy in the plane and the distance of the osteotomy plane to the tibial plateau can be accurately assessed predicted and seen before real osteotomy is done.
- to see the mechanical axis and its position which is updated accordingly given , by changing the planned mechanical axis to pass at the preferred percentage (Fujisawa point) and monitor in AR in real time its location while in operative field.
- to select the spatial location of hinge axis of correction osteotomy by changing the degree of correction in AR the planes of osteotomy offering spatial simulation of the wedge osteotomy in AR allowing intraoperatively in an instant to comprehend what parameters could be modified favourably.
- powerful calculations in a instant of the mechanical axis deviation (in mm) MAD, anatomical and mechanical femoral axes angle (aMFA), mechanical lateral proximal femoral angle (mLPFA), mechanical lateral distal femoral angle(mLDFA), joint line convergence angle (JLCA), mechanical medial proximal tibial angle (mMPTA), mechanical lateral distal tibial angle (mLDTA), Hip Knee Ankle line (HKA) and Mid joint line (MJL) orientation that gives the surgeon valuable objective intraoperatively informations.
- an evaluation in real time of the success of intended osteotomy by evaluating the kinematic alignment of the knee (KAO) avoiding residual joint obliquity or malalignment.
- a navigating guidance of saw bone blade, surgeon is able to monitor the position and orientation of saw blade in Augmented Reality minimizing the risk of intraoperative technical pitfalls and achieve a safe and accurate osteotomy.
- errors to be discovered and corrected during the surgery, enabling the surgeon to achieve an optimally balanced leg alignment. Osteotomy wedge size, joint line orientation, and tibial plateau slope are monitored during correction. The app works as a whole interchangable interacting unit in AR which allows to modify in instant parameters.
- to combine correction- Biplanar-, at coronal plane (a angle) and sagittal plane (β angle) by real time measuring the previous angles, tibia slope, tibia torsion and provides the direction of the the osteotomy plane (ω angle) in which (open or closed) should be made, the height the opening or closing of the wedge and the correction angle (Δ angle) which values are update in real time continuously.
-to try intaroperatively, before real bone cuts are done different strategies in relation to the location, the type of osteotomy, the joint obliquity.
1. Hernigou J et all Computer Navigation Technique for Simultaneous Total Knee Arthroplasty and Opening Wedge High Tibial Osteotomy in Patients with Large Tibial Varus Deformity Surg Tech Internal. 2020 Nov 28;37:265-274.
2. Sang Jun Song et all Computer-Assisted Navigation in High Tibial Osteotomy Clin Orth Surg 2016 Dec;8(4):349-357.
3. Schröter S, et all Surgical accuracy in high tibial osteotomy: coronal equivalence of computer navigation and gap measurement. Knee Surg Sports Traumatol Arthrosc. 2016;24:3410-7.
4. D. Saragaglia, et all. Role of computer-assisted surgery in osteotomies around the knee. Knee volume; 24 pages3387–3395 (2016)
5. D.Paley: Principles of Deformity Correction
6.Marti CB, et al (2004) Accuracy of frontal and sagittal plane correction in
open-wedge high tibial osteotomy. Arthroscopy 20:366–372
7. Song et all Navigated open wedge high tibial osteotomy. Sports Med Arthrosc (2008) 16(2):84–90
8.Billings A, Scott DF, Camargo MP et al (2000) High tibial osteotomy with a calibrated osteotomy guide, rigid internal fixation, and early motion. Long-term follow-up. J Bone Joint Surg Am 82:70–79
9.H Gottschling, M Roth and R Burgkart: Intraoperative, fluoroscopy-based planning for complex osteotomies of the proximal femur: The International Journal of Medical Robotics and Computer Assisted Surgery MRJ010303.3d
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11 Computer assisted alignment of opening wedge high tibial osteotomy provides limited improvement of radiographic outcomes compared to flouroscopic alignment KNEE. 2016 Mar;23(2):289-94.
Tips why App is helpful
Deformities of the lower extremity can be addressed by various sort of ostotomies During classic osteotomies, the electrocatery wire under fluoroscopic control examination, or sterile radiopaque grid placed beneath the patient’s leg intraoperatively or k wires or templates to monitor axial alignment of the leg, could help but are inaccurate
Bone cutting One of the most required result is the accuracy of the procedure. All drill holes should be parallel in both the frontal and sagittal planes, and each bone cut with osteotom should also follow the same direction. An inappropriate drill or bone cut may cause problems, such as pin penetration of the tibial plateau or damage to the tibial neurovascular structures. With the use of navigation system, we can address this technical problems. App helps by the navigated to in real time th saw blade
Deformity correction is the most difficult step. The navigation guidance enables the surgeon to perform deformity correction accurately. The alignment is achieved and the internal fixation implant is in place. During final correction in cases the osteotomy is complete especially the proximal tibia part could slip thus accidentally increasing or reducing the tibia slope which affects the outcome o correction. The real time in augmented reality of passive sensor helps the the surgeon to correct without repeating x-rays opposite cortical fracture, Tibial torsion is measure in real time so is if an accidental rotation of the distal part is done the passive sensor sense this and the TT angle is changed
The benefit of computer-assisted navigation lies in the improved accuracy and precision of postoperative coronal and sagittal alignments. In addition, the navigation system can allow adjustment of the hinge axis position and reduce the risk of opposite cortical hinge fracture. Could be especially useful in Anterior cruciate ligament reconstruction combined with valgus tibial osteotomy (combined procedure) where registration could be more easily done by arthroscopic portals
Our navigation system without needing a preoperative CT scan ,display in real time and calculates all parameters , allowing the surgeon to monitor the degree of correction data throughout the trial, aiding at more complex osteotomies, such as combined femoral and tibial osteotomies (double-level osteotomy) for severe genu varum.
How it works
Three kinds of instruments that determine the exact spatial orientation act as dynamical reference and should be 3D printed before using the app. downloading the appropriate 3D files accordingly You should first be in contact with us . Each instrument is recognised by separate dedicated attached QR code Images. A built-in known dedicated QR-code Image should be exported from the app-by pressing export button.The QR images are exported in photo library - after printing them in a common colour printer preferably as an adhesive label then should to be attached firmly to each dedicated instrument for certain dedicated surface plane. Each one is dedicated for certain position. The dimension of the printed adhesive QR-cod dedicated rectangular surface. The printed QR Image is intended to work as unique dedicated tracker (femur, upper tibia distal tibia ,pointer respectively) and should be in the visual field of iPhones camera. In details, each time the QR code image is recognised inside the screen, a different colour sphere (red for femur, magenta for pointer, blue for distal tibia, green for upper tibia) is assigned, appearing at the center of the rectangular image over the surface respectively for each dedicated QR code. The QR-code Images are captured recognised continuously and tracked by in real time by the App as long as the QR-code Images are constantly recognised as along as the top centred button is on - highlighted.The tracking system is the iPhones camera.
A. Passive sensor (PS). Passive sensors (PS)are dedicated to act as dynamic reference array during tracking. Once the three Passive sensors are 3D printed the adhesive QR-image label over the dedicated surface. Each passive sensor should be placed in a sterilized waterproof sealable bag and then firmly mounted on bone by the use of preferably to Swanz screw or a body of mini external fixator according to surgeon preference.The attached position is dictated by recognised QR image respectively according to the colour of the sphere which appears over the QR image namely red for Femoral Passive Sensor (FPS), green for proximal tibia passive sensor (PTPS), blue for distal tibia (DTPS).
The QR-code Image attached over PS acts as a dynamic reference base attached to the system. Prerequisite is visual contact through i-Phones screen of QR-code Image. The position of all future register points are updated continuously while the QR-code Image acts as a dynamic reference guide marker. In case the leg is placed in different position during surgery and the attached PS change position move as a whole array. Accidental intraoperatively changing position is common ,without the need to reregistering the points. App updates the position of registered points in AR according to the new position.
B.Pointer Probe Tool (PPT) - a device dedicated for surface registration - should be 3D printed. The device consist of the dedicated rectangular resurface connected with a rod. Rod has a predefined length (200 cm) and it is attached perpendicular to the surface. The other side of the rod is the side that acts as mechanical pointer tip locator.
QR-code image dedicated for the PPT should also be exported from the app and printed in a common colour printer preferably as an adhesive label and attached firmly to dedicated rectangular surface plane. The QR-code Image marker is captured and recognised continuously in real time by the App and a magenta sphere appears over the center of the QR image. Once the QR code image is recognised in Augmented reality view a cylinder appears with two spheres at the edges, one proximal (magenta) appear over the center of the attached QR code image over the dedicated rectangular surface and second distally a red sphere appears over the tip of rod at the pointer tip in augmented reality (AR). Distal sphere and should coincide with the tip and this should be corrected before registration by calibration.
Calibration is achieved by simply pressing the directions buttons (+,-) over the screen, the position (XYZ) of magenta tip sphere and the attached grey cylinder in augmented reality (magenta and red sphere are the edge of cylinder) are adjusted as whole construction accordingly. The user aim the pointer tip sphere in AR to be aligned in all dimensions and coincide over the mechanical pointer tip location of the rod of the PPT tool.
More specific :
-by pressing the + or - button in the upper row, the (z) distance is adjusted respectively - it is recommended, first to measure manually the distance from tip-pointer to case, by default this is 20 cm, and calibrate first the Z distance - real distance from the magenta sphere at center of QR image surface to tip of the pointer. The following x y calibration procedure are in two dimension over the screens phone (x,y), aiming to bring the presented red sphere to coincide optically with actual pointer tip.
-in the intermediate row the + - button adjust the (x) distance of magenta sphere e.
-in the last row by pressing the +or - button the (y) distance magneta sphere is adjusted likewise.
Saw Adaptor (SA)
The SA helps to navigate the saw blade accurately. SA can be 3D printed and inserted as an accessory to real saw blade. A QR code image dedicated for the saw adaptor should be recognized by the App and should continuously tracked. Saw adaptor can be adapted over conventional saw orthopaedic blade and calibration is unnecessary as long the distance between Q code image and cutting edge saw is 26mm (Z axis) .
The SA help o determine the exact spatial orientation of saw blade aiding the accuracy of the oscillating Bone saw blade. Two perpendicular crossed rectangular planes appears (one blue horizontal, one vertical green ) in AR . The crossing point of the planes is passing to the center of the saw blade
ω angle depicts direction of osteotomy plane. In case ω angle is 0° the osteotomy is directed perpendicular to sagittal plane and only in the coronal plane the deformity is corrected.
ω’ angle depicts the angle that is formed by current direction of saw blade in relation to preferred planned ω angle. In others word once in real time our saw blade is aligned with the planned osteotomy direction in coronal plane , ω’ takes a zero value the in osteotomy plane
Once the horizontal plane depicted by the blue plane of saw blade is parallel to the red osteotomy plane and the omega angle is zero a hit sound is played confirming that direction of saw blades is this the right according to planed.
Operative set up.
The patient pelvis is in decubitus position in supine position . - In case you place the patient in lateral decubitus only first three registration points should be chosen in sagittal plane instead by <<touching>> three points preferably at the surface of two back post of the patient.
Bicortical, partially threaded pins Screws for the passive sensor are inserted through a tiny (<1 cm) skin incision percutaneously into the epiphysis and metaphysis of the proximal tibia and distal femur both 10 cm away from the joint line. On the femur, the pins are placed starting approximately 5 cm superior to the patella. All three Passive sensors should be placed in a sterilized waterproof sealable bag and then should firmly attached to a bodies of mini external fixator in the predetermined location respectively namely red for Femoral Passive Sensor (FPS) green for proximal tibia passive sensor (PTPS), blue for distal tibia (DTPS).
Prerequisite is visual contact through i-Phones camera of QR-code Image over passive Sensor.
Initially the the Femoral Passive Sensor (FPS) is to be recognised by starting the app before any registration attempt. The position of all future register points are updated continuously while the QR-codes Images acts as a dynamic reference guide marker
Once recognised the QR image over the PPT tool and this is confirmed by appearing a magenta sphere over the middle or dedicated QR code a grey cylinder appears in AR overlaid on the actual PPT tool in AR . PPT tool is ready to used for registering points over a surface. Coloured spheres in augmented reality appear at the tip of PPT after touching any point over the iPhone screen, calibration of the pointer should be done before registration
A.XYZ planes- registration.
- The surgeon selects sequentially three different points (P1,P2,P3) over the surgical bed in the same plane. Through the selected points the coronal plane is defined and a red hazy transparent plane is depicted (coronal) passing through the green spheres constantly in augmented reality.
With the same manner during the registration phase certain stable epicutaneous, pre-defined, pelvic anatomical landmarks-obtained through the drapes, have to be registered. The points that should be acquired are first the Anterior Superior Iliac Spine (ASIS) (P4) and second - the second Anterior Superior Iliac Spine (ASIS)(P5) across, By registering both points a green transparent plane (transverse plane) passing through the green spheres, perpendicular to previous transparent red plane (coronal) is depicted in augmented reality. By repeating the same procedure and registering at last the symphysis pubis (P6), a transparent blue plane appears (saggital plane) passing through the sphere, perpendicular to previously planes. For every three points of registration - three green spheres appears and in the centroid position between these points in space a light blue sphere appears which represents the final registration point of interest.
Femoral Head registration
The integration of a conventional X-ray intensifier into the navigation system makes it possible to use the fluoroscopy as an adjunvant to the registration of anatomical points
The tip of the PPT is placed over the patient skin at the tip of femoral trochanter major and three points are registered and centroid appear as point T first and second aiming at the femoral head centre and guided by overlaid on fluoroscopic radiographic images and by pressing the over the screen three green spheres appear and a new red one is displayed inside the body calculated and placed at the spatial locations of real femoral head Centre in AR
In case more accuracy is preferred the following technique could be done .The hip is rotated to register the hip center. Internal rotation of the whole leg eliminates anteversion and under simultaneous fluoroscopy user can register three points over the skin of the tip trochanter major first and then over the skin, three points, at the femoral head by aiming under fluoroscopic control at the center of femoral head. The app calculates the presumed center of femoral head by taking into about the position of trochanter and combing and calculating the spatial position of Femoral Head center and a red centroid point appears deep inside the body in AR at the center of the femur head.
Femoral shaft landmarks Registration.
By circumcerefential registration of three points around the distal part of femoral thigh under fluoroscopic control a dark brown sphere appears ( Anterior Femoral cortex point)
Knee joint landmarks Registration.
In case the right limp is measured the user should select the following anatomical points sequentially in certain clock-wise fashion starting in following order : most distal and lateral point of lateral femora condyle, most medial and distal point of medial femur condyle, most medial and proximal tibia point and most lateral and proximal tibia point please see tutorial videos at orthopractis.com. By the same manner for distal right tibia user should registered in following order most lateral distal point of tibia at ankle joint one posterior second anterior most lateral proximal over talus in ankle joint , medial distal point of tibia in ankle joint or most medial and proximal over talus in ankle joint one anterior one posterior. (right limp clock-wise).
I case left limp is measured the above pattern should be followed likewise but the points should be selected in counter-clockwise fashion.
Likewise by registering two times, three points separately each time at femur lateral condyle the result are two purple centroids (FMC1, FMC2). By the same manner three points at medial femur condyle, one white point centroid (FLC1) appear. -Right limp-
A yellow cylinder connecting the centroid of FMC1 and FMC2 and the FLC1 and a yelow plane appear perpendicular to femur axis which represents the femur joint surface.
With the same manner once the blue QR image is recognised user can register the tibial anatomical landmarks by selecting three point, a purple sphere (medial tibial Anterior plateaux-) appear (MTA) likewise a purple sphere (centroid) after selecting three point medially aiming at medial tibial Posterior plateaux (ΜΤP), and at medial tibial Lateral plateaux MTL. Likewise aiming at Lateral tibial Anterior plateaux the white sphere LTA appear and at Lateral tibial Posterior plateaux, the white sphere LΤP and at Lateral tibial Lateral plateaux the white sphere LTL .
Tibial joint surface is depicted by yellow planes which passes between the three white spheres appear and three purple spheres. A vertical purple cylinder appears perpendicular to tibia plates for measuring the tibia torsion .
Distal Tibial landmarks Registration
The most prominent points on the medial and lateral malleoli are registered with the blunt tip probe. After Proximal tibia QR code recognition, likewise after three points registration the following anatomical landmarks should be selected: lateral malleolus posterior-, a centroid white sphere LMP appears- , lateral malleolus anterior - white LMAn sphere appears , medial malleolus anterior, purple sphere MMAn appears , medial malleolus posterior a purple MMP sphere appears.
Selection of osteotomy site
User can select the location of hinge by selecting in space over bone two points, point 1 -red sphere, point 2 - red sphere. Both points are connected by red line forming the Hinge Axis of correction osteotomy
By aiming at the preferred side across the Hinge axis over the other side of the bone with the pointer the surgeon selects the entry point - D point -starting the opening or closing wedge osteotomy. Two red planes appear in AR connecting the hinge axis and the D point representing the planes forming the triangular wedge of the osteotomy in space. The + or - button appear at screen, the degrees of correction also appear - default value is 0 ° - for every click by pressing + or - button, one degree of correction is added or subtracted respectively and the second plane of osteotomy emerges and printed in AR as second red plane (HD`) from Hinge axis to point D`. All measured values and location of drawn cylinders lines are being updated in real time accordingly.
Between the planes of the osteotomy HD and HD` , angle Δ is measured which is the actual correction angle of the wedge. The base of the triangle (DD`) the lateral cortex corresponds to the height of the wedge. By pressing the + or - button, with center the hinge axis either clockwise or counter- clockwise, the corresponding height (DD`) of opening or closing osteotomy is increase or reduced respectively. The projection of angle Δ at coronal plane (varus-valgus osteotomy) is depicted by the a angle and the projection of angle Δ at saggital plane (flexion-extension osteotomy) is depicted by β angle.
In case double correction is planned,- biplanar osteotomy- combined correction at coronal (a angle) and sagittal plane (β angle) are obtained. These angles of combine corrections at coronal and sagittal plane are depicted and their values are continuously updated -projections of final correction angle delta (Δ) .
The direction of osteotomy between in the coronal to sagittal is also presented by measuring the (ω) angle which is the angle formed between them. The posterior proximal tibia angle PPTA and the actual Tibial slope PS is calculated continuously in the sagittal plane and by adding or reducing the β angle tibia slope measurement change respectively.
By trying different combination of correction in augmented reality environment in real time surgeon can be helped to decide the optimal combination of all measured parameters before actually proceeds to real osteotomy.
In case ω angle is 90° the osteotomy is directed perpendicular to sagittal plane and only in the coronal plane the deformity is corrected (varus- valgus). Δ angle equals a angle and β angle equals 0°.
To avoid overcorrection especially during exaggerated joint laxity correction angle a is adjusted by taking into account ligament laxity measured by joint line convergence angle (JLCA) the JLa joint ligament adjusted angle is measured by the following mathematical formula (JLa = a - JLCA-2/2 - if JLCA>2) this could be helpful in surgeon who wants to correct the deformity by taking in to account the ligament joint laxity .
The selection of the amount of correction should based over the experience to avoid over or under correction .
The App helps to categorize objectively deviation or deformity in the frontal plane (varus or valgus) and differentiate the level of deformity (femoral and or tibial origin) and according to measured angles objectively suggest where indicated, medial or lateral, open or closed-wedge distal femur osteotomy or high-tibial osteotomy or double osteotomies. Restoring the mechanical axis by osteotomies around knee is easily calculated and presented on screen. In addition by measuring Hip Knee Ankle line (HKA) and Mid joint line (MJL) orientation, App allows to evaluate in real time the success of intended osteotomy by evaluating the kinematic alignment of the knee (KAO), avoiding residual joint obliquity or malalignment.
In case femoral angle (mLDFA) and tibial angle (mMPTA) and Hip Knee Ankle line (HKA) and Mid joint line (MJL) are in abnormal range double osteotomy is suggested and which kind of double osteotomy is indicated. In case femoral angle (mLDFA) or tibial angle (mMPTA) abnormal, Single osteotomy is suggested.
Outcome of planned degree of correction is also presented and a green coloured message of successful osteotomy is presented on screen, in case femoral angle (mLDFA) , tibial angle (mMPTA) , MJL are normal and also HKA is normal -otherwise with a red letter appears that the osteotomy is not successful.
Bone Saw cut navigation
The Saw Adaptor (SA) helps to navigate the saw blade accurately. A QR code image dedicated for the saw adaptor and should be recognized and continuously tracked by the App . Position of the osteotomy planes of resection are defined and a red hazy transparent osteotomy plane is depicted passing through the tibia constantly in augmented reality. Once the dedicated QR code image dedicated for the saw adaptor is recognised two perpendicular planes around the saw blade appeared with different hazy transparent colours (green-sagittal coronal-blue,) in augmented reality over the center of tip of the bone saw blade , extending also over the blade span. The coronal plane - blue hazy transparent plane is depicted passing through two blue spheres constantly in augmented reality which are extending at the edges of the blade. A green transparent plane (saggital) is passing through the green spheres, perpendicular to previous transparent blue plane (coronal) .
Over the screen in real time two angles corresponding to the direction of saw blade are depicted. For simplicity reason every colour of a plane corresponds certain direction more specifically:
The row with green tile by red tile represent the angle subtended by sagittal plane (green ) of the blade saw and the saggital osteotomy plane (blue). Also ω’ angle is printed which is calculated in real time and is the difference of current direction of saw blade during osteotomy with the previous planed direction of osteotomy plane (ω angle). Once ω’ angle and ω angle are zero is indicated that the current position of saw plate in saggital plane meet the planed position of direction of osteotomy .
The row with blue tile by red tile represented the angle subtended by the coronal plane of the blade saw (red) and coronal osteotomy plane (red). The angle formed by navigated saw blade and the osteotomy plane in coronal plane should be zero indicating that the navigated saw blade is parallel to planned osteotomy plane.
The following two conditions during bone cut by the navigated saw blade should be full-filled in order to hear an audible hit sound, an indication that we are at right plane according to planed osteotomy in space:
a. ω’ angle and ω angle to be 0°±3°
b. The angle formed by navigated saw blade and the osteotomy plane in coronal plane is 0°±3°
Both values separately turn green whenever the 0°±3° criterion is meet according to current position otherwise return red.
Manipulating the Oscillating Bone Saw Cutting Machine Orthopedic Power Tool in real time the surgeon, values of all above mentioned angles change respectively, obtaining positional information and direction with accuracy in real time in augmented reality by observing the screen
In quick view,
Sphere in Ar over QR code image of:
pointer probe tool (PPT) - magenta sphere
Saw Adaptor (SA)- orange
femur -red sphere
Proximal Tibial -green sphere.
Distal tibia- blue sphere
The whole procedure of registration is activate first by recognising initially the distal femur QR code image (red sphere). Once the QR code image of the pointer is recognised (magenta sphere) the pointer is activate and by pressing anywhere over screen iPhone at the tip of the pointer a new sphere appear, registrating spatially the current point of selection. User has to choose sequentially and manually the following certain anatomical landmarks - points, which are shown below with the following correct order:
1.three point selected over the over an imaginary triangular placeced
P1,P2,P3 cover at surgical bed - red transparent plane appear -coronal plane is depicted in AR - (P1,P2,P3)
Pelvic landmarks Registration.
2. Anterior Superior Iliac Spine (ASIS) -(three points should be registered in space around the region of interest and a centroid light blue sphere appears respectively - P4 ) .
3. The other Anterior Superior Iliac Spine (ASIS)- (three point should be registered in space around the region of interest and a centroid light blue sphere appears respectively - (P5) a green transparent plane -transverse plane - (P4,P5)
4. symphysis pubis (three point should be registered-green spheres- in space around the region of interest and a centroid light blue sphere appears respectively - (P6) ) a transparent blue plane appears (saggital plane) perpendicular to all planes perpendicular to previous transparent red plane (coronal) reality.
Femoral head landmarks Registration.
Preferably under pelvic fluoroscopic control
5.T tip of trochanter major, three points.
6. HC- Femur head centre, three points.
Femoral shaft landmarks Registration.
7. Anterior Femoral cortex - three points , circumferential in around the distal part of femoral thigh - dark brown sphere appears
Knee joint landmarks Registration.
8. Two lateral femur condyle 1. Femur lateral condyle three point a purple centroid FMC1, 9. Femur lateral condyle three points, a purple centroid FMC2
10. One medial femur condyle, three point a white centroid FLC1
Cylinder connecting the centroid of FMC1 and FMC2 and the yelow plane appears depicting distal femur joint plane.
Proximal Tibial landmarks Registration is activate after QR image recognition dedicated for Proximal Tibial (green sphere).
A.medial tibial plateaux, light purple sphere centroid after three points registration
11.MTA medial tibial Anterior plateaux
12.ΜΤP medial tibial Posterior plateaux,
13. MTL medial tibial Lateral plateaux,
B.lateral tibial plateaux, white spheres
14.LTA Lateral tibial Anterior plateaux
15.LΤP Lateral tibial Posterior plateaux,
16.LTL Lateral tibial Lateral plateaux,
yellow plane appear depicting Proximal Tibial joint plane
Distal Tibial landmarks Registration is activate after QR image recognition dedicated for Proximal Tibial (blue sphere).
17.lateral malleolus posterior (LMP), after three points registration a centroid white sphere
18.lateral malleolus anterior (LMAn), after three points registration a centroid white sphere
19. medial malleolus anterior (MMAn), after three points registration a centroid purple w sphere
20. medial malleolus posterior (MMPs), after three points registration a centroid purple white sphere
orange line = current mechanical axis of the leg.
blue line- Fujisawa line = Corrected mechanical axis passing at Fujisawa point.
Activation after QR image recognition dedicated for Saw Bone Adaptor (orange sphere).
By pressing + or - button the blue line with center the femoral head is rotated clock wise or counter clockwise intersecting the tibial plateau at Fujisawa point (F) while the respective percentage appears over the button.
Hinge Axis point 1 -red point
Hinge Axis point 2 - red pont
Red line connect the above points forming the hinge axis.
D → across the Hinge Axis to the other side of the bone-the opening of the wedge.
Two Red planes appear superimposed, main osteotomy Plane passing through D, second osteotomy plane passing through D’
Final degree of correction - for every click by pressing + or - button, default value is 0 ° -
one degree of correction is added or subtracted respectively and second plane of osteotomy emerges in AR and opens or closes according to degree of correction Between two red planes a Δ -angle is formed.
Point - point registration-enter.
Export - all QR codes images are exported to current image library
Undo - return to previous point selection.
Save - screen contents is saved as an image to the photo album of the device.
Arrows pointing up above normal arrow pointing down below normal
mLPFA = mechanical lateral proximal femoral angle, normal value 90° ± 5°, yellow
mLDFA= mechanical lateral distal femoral angle, normal value 87° ± 3°, orange
aLDFA = Anatomical lateral distal femoral angle, normal value 81° ± 2°,green
aMFA = anatomical mechanical femoral axes angle, normal value 6° ±1°.
JLCA = joint line convergence angle, normal value 0-2°. Light blue
d= distance in mm between femoral joint center and tibia joint centre normal values <=6mm, subluxation due to ligament laxity
Ant - femoral anteversion aproximatly
mMPTA = mechanical medial proximal tibial angle, normal value 87° ± 3°, brown.
mLDTA= mechanical lateral distal tibial angle 89 ° ± 3°, blue
aFTA = anatomical femorotibial angle, standard value 173-175°.
MAD = mechanical axis deviation in mm.
Type of deformity
normal no message ,
femoral (mLDFA ≥ 87° ± 3°) varus otherwise valgus, deviation or deformity,
Tibia (mMPTA ≥ 87° ± 3°) valgus otherwise varus , deviation or deformity,
differentiate between a femoral and a tibial cause of malalignment
Genu varum, Anatomical femorotibial angle(aFTA) > 173–175° and
Genu valgum, Anatomical femorotibial angle (aFTA) < 173–175°
FL=femoral length in cm
TL=tibia length in cm
LL’=Mechanical Axis length in cm
HKA =Hip Knee Ankle line, normal range 180 ° ± 3° otherwise knee <177° varus valgus >184
MJL = Mid joint line orientation (normal 87° - 94°, varus<86 ° valgus >94 °
KAO=Kinematical Aligned Osteotomy, normal if HKA and MJL are normal, otherwise abnormal.
JLa = correction angle adjusted by taking into account ligament laxity measured by joint line convergence angle (JLCA) JLa = a - JLCA-2/2 - if JLCA>2
Δ -angle Final opening or closing correction angle between the red planes.
a =final opening or closing correction angle in coronal plane.
β angle = correction angle at saggital plane
[a] → initial calculated opening or closing correction angle in coronal plane
HD= initial plane of triangular, mediolateral diameter the opening or closing of the osteotomy in mm
DD`=base of the triangle, or osteotomy gap opening or closing in mm correction at osteotomy plane plane -at Δ angle .
PPTA posterior proximal tibia angle normal values 80 ° ± 3.5°
PS Tibia slope (90-PPTA)
ω angle =direction of osteotomy plane. In case ω angle is 90° the osteotomy is directed perpendicular to sagittal plane and only in the coronal plane the deformity is corrected.
Outcome: Successful osteotomy if femoral angle (mLDFA) and tibial angle (mMPTA) and MJL normal HKA normal otherwise with red not successful osteotomy
Osteotomy suggestion: Single osteotomy, distal femur osteotomy (DFO) or high-tibial osteotomy (HTO) - Medial or Lateral open or closed wedge accordingly or double osteotomy both distal femur osteotomy (DFO) and high-tibial osteotomy (HTO) Medial or Lateral open or closed wedge
TT Tibial Torsion angle =the angle between the magenta cylinders that are perpendicular axis to proximal tibia and distal tibia in AR
ω’ angle = the difference of current direction of saw blade during osteotomy plane with the planed direction of osteotomy plane (ω angle).
Calibration buttons of Pointer
z + or - buttons in the upper row —> adjust the (z) distance-depth
y + or - buttons in the intermediate row —> adjust the (y) distance, up-down
x + or - buttons in the last row the + - button —> adjust the (x) distance, left-right
L + or - buttons enlarge or reduce length of grey cylinder ending to yellow sphere namely the tip of the real instrument should coincide with the yellow sphere.
All information received from the software output must be clinically reviewed regarding its plausibility before patient treatment! The App indicated for assisting during operation the Operator. Judgment and experience are required to properly use the App. The software is not for primary image interpretation. Any influence the operators in making decisions during operation remains Surgeons own responsibility and experience.