NavitoolHip App how to measure

Good surgical technique and accurate implantation of the components are likely to improve the longevity and function of Total Hip Arthroplasty (THA). Early revisions at less than five years are due to implant malposition, dislocation and infection which are usually dependent on the surgical technique. Optimal cup implantation (Lewinnek’s s safe zone -anteversion 15± 10 and inclination 40± 10) is critical for good performance and longevity of THA.
Placement of the acetabular cup during surgery can be performed by using free hand technique and or by alignment support frames on the Inserter. The surgeon try to navigate by taking into account the position of the frames. However, the accuracy of these methods is questionable and usually operator’s experience dependent. In addition there are several factors that may impair the surgeon’s ability to accurately place cup in optimal position, difficulty to asses precisely patient’s pelvic position due to clothing, dysplastic acetabulum with anatomical variations, limited visibility etc.
Acetabular cup malposition outside of the Lewinnek’s safe zone increases the risk of complications like decreased range of movements, increased rates of impingement, increased wear rates, acetabular migration, recurrent dislocations, osteolysis, ‘squeaking’, leg-length discrepancy, and early failure rates. Acetabular cup orientation based on surgeon’s visual assessment could result in an inaccurate placement. Computer-assisted navigation systems have been explored in total hip arthroplasty (THA) and in our days is proven that they improve the precision in cup position and leg length restoration. Apple developed and popularised (AR) Augmented Reality technology readily available for its devices.The application take advantage of Augmented reality and merges it with Computer Assisted Orthopaedic Surgery (CAOS) techniques and principles in effort to help an orthopaedic surgeon during operation without the need of expensive CAOS equipment. The app helps expedite the procedure of cup positioning effortlessly.
The App is medical App software aimed for orthopaedic surgeons, providing a tool that allows the surgeon to see:
by registering, with the tip of iPhone-Case-Probe instrument certain anatomical landmarks, to see in Augmented Reality all 3D planes with different transparent colours (sagittal-blue, coronal-red transverse-green),
a transparent sphere inside the real acetabulum centred over the centre of hip rotation and also in augmented reality the bony pelvis whole in the screen.
By attaching the Case -Probe to certain clamp and attaching to the reamer or later to inserter, the surgeon can be oriented by taking into account in real time six angles respectively namely Anatomical Anteversion (AA) and Inclination (AI) , Operative Anteversion (OA) and Inclination (OI) and Radiographic Anteversion (RA) and Inclination (RI),which concurrently presented in real time.
-by seeing in real time all the angles and by changing the direction of the reamer or inserter the surgeon can adjust the position of the cup respectively seeking the recommended final Implant orientation of 45 ± 10 degrees of anatomical inclination (AI) and 15±10 degrees of anatomical anteversion (AA).On screen the
-Acetabular dimension is also printed in mm allowing the surgeon to decide in advance the size of starting reamer and the anteroposterior, mediolateral, and craniocaudal positions.
-During surgery, as long as the measured values by the App of AI and AA are between the above mentioned normal range, the printed colour of them in screen remains green, otherwise whenever the respective real time value are outside the normal range, the values of AI and AA are printed in red colour, indicating in real time that the positioning of the cup placed by the surgeons hand for reaming or impacting is not optimal.
- The app helps the surgeon to obtain positional information in real time in augmented reality and thus to avoid eccentric reaming, also helps impacting the cup in the recommended final Implant orientation of 45 degrees of inclination and 15 degrees of anteversion by adjusting the inserter position according to readings app.
The powerful undo feature gives the user the freedom to make corrections without resetting the whole procedure. Simply by clicking the undo button the measurement returns to last chosen point (or state) and you are ready to choose the same point again, without reseting the whole measurement and starting again from the beginning.