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CUP ANTEVERSION INCLINATION APP

In Total hip Arthroplasty the orientation, namely anteversion and inclination of the new acetabular component -cup- influences wear, range of movement (ROM), and the likelihood of dislocation after total hip replacement (THR). Evaluating objectively of the cup anteversion, and inclination in hip arthroplasty replacement surgery is of paramount importance. Radiographs are the most important diagnostic means in the follow-up for evaluation of a total hip arthroplasty. Measuring anteversion and inclination in everyday clinical setting is a cumbersome work for a medical doctor. Computation requires a calculator, which requires an additional effort during practice and slows down workflow. 

The  App is medical software aimed for orthopaedic surgeons a tool that allow doctors to:
-Securely import medical images directly from the camera or stored photos.
-By marking certain anatomical landmark and points in a simple  standard AP pelvic radiograph, values for cup inclination and anteversion are being calculated. The app is based on Widmer’s method which is the proven that is the most accurate compared to others. 

-Pelvic tilt expressed by the angle APP is incorporated in measurements and can be adjusted manually according to surgeons preference.
-Radiographic Inclination (RI) and Radiographic Anteversion (RA)  values  are adjusted by taking into account  pelvic tilt (APP angle).
- RI or RA values are printed in red or green, according to measured value in cases these are in certain range (Lewinnek  at al), indicating if the positioning of the cup is optimal (green) or not (red). 
-The data are printed over to screen so each case can easily assessed 
-Save the planned images, for later review or consultation.

Anterior pelvic plane (APP) Plane defined by the two anterior iliac spines and pubic tubercle. The angle between the APP and the coronal plane-  is the APP angle and is used to evaluate the degree of the pelvic tilt Pelvic tilt measured by APP angle affects the functional position of the cup as measured on standard radiographs. Pelvic tilt may lead to misinterpretation of cup position on anteroposterior pelvic radiographs. We added mathematical correction to reduce these errors. The angle APP is added and in calculation and can be adjusted  manually according to surgeons preference. A negative PT angle indicates posterior tilt, and a positive PT angle indicates anterior. In case you surgeon does not have actual value of App angle, by seeing the position of coccyx in pelvis X-ray in relation to pubis symphis the value can be estimated.(Schwarz TJ et al. Correction of Pelvic Tilt and Pelvic Rotation in Cup Measurement after THA - An Experimental Study. Rofo. 2017 Sep;189(9):864-873. ) by pressing + or - value of APP angle is changed accordingly taking also positive or negative values. 
-RI-Radiographic Inclination and RA-Radiographic Anteversion values  are adjusted by taking into account the Pelvic Tilt  (APP angle ) according to mathematical correction algorithm (Lembeck  et al, Pelvic tilt makes acetabular cup navigation inaccurate.Acta Orthop. 2005 Aug; 76 (4) : 517 - 23.).  


The app offers an easy way to quantify cup anteversion and inclination a quick and comfortable manner without the use of a goniometer or a ruler or to calculate elaborated formulas.
All information received from the software output must be clinically reviewed regarding its plausibility before patient treatment! The App is indicated for assisting healthcare professionals. Clinical judgment and experience are required to properly use the software.The software is not for primary image interpretation.
  In a busy THA practice, the examiner to draw lines in X-rays, it is time consuming and cumbersome. Accessory instruments like  calculators, protractors, hinged goniometers, well sharped pencils, rulers or even transparent papers must be available. This App is particular useful in clinical settings where you need a quick results without losing time. Please see tutorial videos

REFERENCE 
1. NOMURA T, NAITO M, ET AL  .AN ANALYSIS OF THE BEST METHOD FOR EVALUATING ANTEVERSION OF THE ACETABULAR COMPONENT AFTER TOTAL HIP REPLACEMENT ON PLAIN RADIOGRAPHS. BONE JOINT J. 2014 MAY;96-B(5):597-603.
2. BACHHAL V, JINDAL N, SAINI G, SAMENT R, KUMAR V, CHOUHAN D,
DHILLON M. A NEW METHOD OF MEASURING ACETABULAR CUP ANTEV-
ERSION ON SIMULATED RADIOGRAPHS. INT ORTHOP. 2012;36:1813–1818.
3. WIDMER KH A SIMPLIFIED METHOD TO DETERMINE ACETABULAR CUP ANTEVERSION FROM PLAIN RADIOGRAPHS. J ARTHROPLASTY. 2004 APR;19(3):387-90.
4. ABDEL MP, VON ROTH P, JENNINGS MT, HANSSEN AD, PAGNANO MW.WHAT SAFE ZONE? THE VAST MAJORITY OF DISLOCATED THAS ARE WITHIN THE LEWINNEK SAFE ZONE FOR ACETABULAR COMPONENT POSITION.CLIN ORTHOP RELAT RES. 2016 FEB;474(2):386-91
5. MURRAY DW: THE DEFINITION AND MEASUREMENT OF ACETABULAR ORIENTATION. J BONE JOINT SURG BR 1993 75:228,
6. LEWINNEK GE, LEWIS JL, TARR R, COMPERE CL, ZIMMERMAN JR. DISLOCATIONS AFTER TOTAL HIP-REPLACEMENT ARTHROPLASTIES. J BONE JOINT SURG AM. 1978;60:217–220
7.SCHWARZ TJ ET AL. CORRECTION OF PELVIC TILT AND PELVIC ROTATION IN CUP MEASUREMENT AFTER THA - AN EXPERIMENTAL STUDY. ROFO. 2017 SEP;189(9):864-873.

HOW TO MEASURE WITH THE APP

Pelvic tilt may lead to misinterpretation of cup position on anteroposterior pelvic radiographs. The angle APP is added and in calculation and can be adjusted manually according to surgeons preference. In case Pelvic tilt measured by APP angle is known, by pressing + or - button the preferred angle, either negative or positive, can be selected - a negative angle indicates posterior pelvic tilt, a positive APP angle indicates anterior pelvic tilt - otherwise the APP angle takes by default  zero value. 
     By  moving the transparent circular yellow template over the tear drop and by clicking the “point” button the  tear drop of the selected side is marked (T1 point) (the order of the selection right-left or left-right does not influence the results of measurement). Next by clicking over the other side’s teardrop, T2 point is marked and the yellow inter teardrop line is drawn T1T2.
     By pressing the “point” button aiming at the most medial part of the acetabular component the C3 point is marked, by repeating the same procedure at the most lateral part of the cup the point C4 is marked. A C3C4 line- light blue- is drawn, the long axis of the imaginary eclipse. The Angle subtended between line C3C4 (long Axis) and line T1T2 (inter teardrop line) forms the Radiographic Inclination Angle of the cup (RI) which is calculated and printed over the screen.
     By aiming the most caudal lip - Absorption of x-rays by metallic prosthetic heads disguises part of upper lip of the ellipse - of the acetabular component you mark the C5 point, a green coloured eclipse of the acetabular component is drawn and the short axis - purple line perpendicular to long axis C3C4 - is depicted. Next the most cephalad point of the cup is selected and by pressing the “point” button  the C6 point is marked and a perpendicular orange line to long axis C3C4 is drawn, the total length (TL) of the cup is depicted. Also an orange perimeter of the cup is drawn.
The Cup anteversion (AV) is calculated through the formula: arcsin ( short axis / total length-short axis ) is calculated by the app and printed over the screen.
    In quick view , the following reference points  you have to choose sequentially manually are shown below by the following order:
 
+ or - button →Pelvic tilt measured by APP angle, the preferred angle selected- in case you left blank, zero value is taken by default.
T1 → right or left  acetabular teardrop.
T2 → left or right  acetabular teardrop.
C3 → right most medial point of the cup.
C4 → right most lateral point of the cup. 
C5 → right most caudal point of the cup. 
C6 → cephalad point of the cup.
Without repeat the selection of teardrop points (T1,T2) you can proceed to the other side.
C7 → left most medial point of the cup
C8 → left most lateral   point of the cup
C9 → left most caudal point of the cup
C8 → left cephalad point of the cup 
T1T2 → inter-teardrop line
C3C4 → long axis of the ellipse of the acetabular component 
C5C6 → total length of the Cup
-Screen readings of Inclination and Anteversion  Angles of the acetabular component
RI-Radiographic Inclination 
RA-Radiographic Anteversion 
OI-Operative Inclination 
OA-Operative Anteversion
AI-Anatomical Inclination 
AA-Anatomical anteversion
   In case the measured values by the App of Radiographic Inclination- RI or  Radiographic Anteversion- RA are between  normal range (40°±10° of inclination or 15° ± 10° of anteversion, Lewinnek et al. ), the printed colour of them in screen is green, otherwise whenever falls outside the normal range, the values of RI or RA are printed in red colour, indicating that the positioning of the cup is not optimal. 
Please see tutorial videos at the developer’s web site www.orthopractis.com
All information received from the software output must be clinically reviewed regarding its plausibility before patient treatment! The App is indicated for assisting healthcare professionals. Clinical judgment and experience are required to properly use the software.The software is not for primary image interpretation.