Joint mismatch or in another words joint incongruity between femur head (ball) and acetabulum (socket) of the hip leads to altered mechanics, which can lead to premature degenerative osteoarthritis. Loss of congruity with the acetabulum is common in patients with DDH.
Treatment of incongruity is paramount importance because you have to address it early and the treatment of choice are usually corrective hip osteotomies. In order-from one hand to avert the natural course to the progression of secondary osteoarthritis (OA) and from another hand to avoid- in developing skeleton - to deteriorate more the hip dysplasia the congruity must be objectively and thoroughly evaluated especially at follow up of these procedures in both congruent and incongruent hips. Congruity between the femoral head and acetabulum is determined by the percentage of femoral head covered by the bony acetabulum. The congruity index (CI) is calculated (A/B- ratio converted to a percentage) by diving the (A) distance by the distance (B), where distance (A) is the distance between the teardrop to the lateral acetabular margin and (B) is the distance from the teardrop again to the lateral femoral head edge.
The Congruity Index 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
-Offers a very convenient way to determine the most accurate possibly way an objective value of congruity. By clicking three point at the x-ray picture on your iPhone screen and inserting the side the App calculates the congruity index (CI) which is the percentage of femoral head covered by the bony acetabulum. Congruity between the femoral head and acetabulum is expressed in percentage. Values of Coverage less than 75% is considered pathologic in another words the hip is incongruent
-Save the planned images, for later review or consultation.
All information received from the software output must be clinically reviewed regarding its plausibility before patient treatment! CongruityIndex 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, measuring in X-rays in clinical settings it is time consuming and cumbersome. Accessory instruments like protractors, goniometers, well sharped pencils, rulers or even transparent papers must be available. The app offers a very convenient and accurate way to measure the value of Congruity and help decide what could be considered normal or pathologic.
The app is not a simple goniometer, is an enhanced product which help to monitor objectively during the course of the treatment how much the congruity and evaluate the remodelling. This App is particular useful especially in clinical settings where you need a quick results without losing time. Please see tutorial videos at the developer’s web site.https://www.orthopractis.com/congruity-index-app
Reference
1.Cooperman DR, Wallensten R, Stulberg SD. Acetabular dysplasia in the adult. Clin Orthop 1983; 175: 79
2. Delaunay S, Dussault RG, Kaplan PA, Alford BA Review Radiographic measurements of dysplastic adult hips Radiographic measurements of dysplastic adult hips. Skeletal Radiol. 1997 Feb;26(2):75-81.