Sagittal Balance App
The assessment of global sagittal alignment and the compensatory mechanisms which are implicated in the spine and the spinopelvic jucture are of paramount importance for spine and joint replacement surgeon. The dynamic interplay between flexibility and balance around the axis of gravity determine the type and the amount of influence in spine and hips. Radiographic parameters to evaluate objectively the sagittal balance are Pelvic incidence (PI), Sacral slope (SS), Pelvic Tilt (PT), Lumbar lordosis (LL),Thoracic Kyphosis, C7 plumb line (C7PL) and its ratio. Drawings in patients X-rays and precise measurements are important in order to quantify the magnitude of spinal deformities, to monitor the success or failure of treatment and thus optimise the management of patients according to the severity of the imbalance.
The Sagittal Balance App is medical software aimed for orthopaedic surgeons, providing tools that allow doctors to:
-Securely import medical images directly from the camera or stored photos.
-By marking several points at the image of X-ray, the App calculates and offers a very convenient way to determine the most accurate possibly way at once, Pelvic incidence (PI), Sacral slope (SS), Pelvic Tilt (PT), Lumbar lordosis (LL), thoracic kyphosis, C7 plumb line (C7PL), C7PLD/sfd ratio, PI–LL, theoretical normal pelvic tilt (tPT),theoretical normal L1-S1 lumbar lordosis (tL1S1), Spino-sacral angle (SSA) According to measured parameters the app categorizes the severity of the imbalance of spine, in three different stages: optimal balanced, balanced with compensatory mechanisms and imbalanced.
-Save the planned images, for later review or consultation.The measured values are compared by normal reference databases and also data are exported as txt file, ready to print or to input as cells to excel for research.
-The app also allows the calculations of centroids after choosing points in vertebra body in independent manner from order.
All information received from the software output must be clinically reviewed regarding its plausibility before patient treatment! Sagittal Balance App 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 everyday practice, the examiner have to draw lines in X-rays or in clinical settings, this it is time consuming and cumbersome. Accessory instruments like protractors, hinged goniometers, well sharped pencils, rulers or even transparent papers must be available. The app offers a very convenient and accurate way to perform most common radiographic measurements for spine, and spinopelvic juncture in a blink of an eye in front of your screen. The build in feature of the app, allows results to be categorized may help decide what could be considered normal or pathologic.
The app is not a simple goniometer, is an enhanced product which helps to monitor objectively the course of the treatment and evaluate optimally the spine. This App is particular useful especially in clinical settings where you need a quick results without losing time. Please see tutorial videos at the develop
Reference databases
1.Legaye J, Duval-Beaupe`re G, Hecquet J, Marty C (1998) Pelvic incidence: a fundamental pelvic parameter for three-dimensional regulation of spinal sagittal curves. Eur Spine J 7(2):99–103
2. Cavanilles-Walker JM, Ballestero C, Iborra M, Ubierna MT, Tomasi SO (2014). "Adult Spinal Deformity: Sagittal Imbalance". International Journal of Orthopaedics.
How to measure with Sagittal Balance App
The first thing is to load one image from your photo library or capture a photo from x-rays photos of a patient. Next you aim to mark four points (P1,P2,P3,P4) at the four corners of the rectangular body of C7 vertebra by clicking the point ‘button” you mark the edges of superior and inferior end plates of the C7 vertebra - the order of markings does not affect the measurement. The app will automatically determines the centroid of the C7 vertebral body and a vertical orange line is dropped from centroid, and the C7 plumb line (C7PL) is drawn. Aiming at the T4 vertebra and by clicking the button ‘point’ the point P5 over the left edge of the superior end plate of the T4 is marked and by the same manner locating the right edge of the superior end plate the point P6 is also marked- the order of marking does not affect the measurement. The line P5P6 is drawn. By the same manner you mark two points P7,P8 over the anterior and posterior, superior endplate of vertebra body of L1 and a green line appears P7P8.
Next you aim at the posterior corner on the top margin of S1 of the sacrum and by clicking the button ‘point’ the P9 point is marked and automatically also a magenta vertical line is erected (SVA-Sagital Vertical Axis). By clicking the ‘point’, button at the anterior corner of the superior end plate of S1 vetebra , the point P10 is marked. Next you aim at centers of the femoral heads and by clicking the ‘point’ button you mark the centers of each femoral head C11, C12 . A line C11C12 (hip axis line- HA) is drawn and from the midpoint (C point) of HA line a vertical yellow axis (bi-coxo-femoral axis -BCFA) is erected.
What is calculated in the Sagittal Balance App
1. Spino-sacral angle (SSA)-the angle between the sacral plate and the line connecting the centroid of C7 vertebral body and the midpoint of the sacral plate
2. Lumbar lordosis Angle (LL) -Cobb angles L1-S1
3. Thoracic Kyphosis Angle (TK)- Cobb angles T4-T12
4. C7Pl/SFD ratio - in normal population the value of this ratio is -0.9 ± 1
6. C7PLD- a horizontal distance between C7 plumb line (PL) and the vertical axis on the superior posterior corner on the top margin of S1 of the sacrum (SVA- Sagittal vertical axis)
7. SFD-femoral distance (SFD) is the horizontal distance between the vertical bi-coxo-femoral axis (BCFA) and the vertical line passing through the superior posterior corner of the sacrum(SVA).
8. Pelvic incidence Angle (PI) -the angle subtended by the perpendicular to the sacral plate at its midpoint and the line connecting this point to the femoral heads axis (point C)
9. Sacral slope Angle (SS) the angle subtended by the superior plate of S1 and a horizontal reference line (HRL).
10. Pelvic tilt Angle (PT), the angle subtended by the vertical bi-coxo-femoral axis (BCFA) and the line connecting the midpoint of the sacral plate .
11. PI–LL- Pelvic incidence Angle (PI) minus Lumbar lordosis Angle (LL) ,normal valus < 10degrees
12. tPT - theoretical normal pelvic tilt, difference between theoretical value and measured value is a compensation phenomenon
13. tL1S1 - theoretical normal L1-S1 lumbar lordosis
