The app approximate true biomechanical conditions in hip as realistically as possible Now we are able to predict the biomechanical effect on load and pressure of an operative procedure by computational means.Load determinations in the literature are based essentially on the load model developed by Pauwels in 1935, . Technical difficulties prevented an explicit load calculation until 1977, when the difficulties were resolved by Legal . The model described by Legal et al. which is based on a uniform stress distribution and the calculation of maximum pressure during one leg stance in walking, without involving complicated mathematics and physics, for evaluating the biomechanical efficacy of current standard operations, and for the explicit calculation of prevailing joint pressure in the individual case which has been used in app.
Tonnis presented the whole method for extracting from simple geometric parameters from a standard AP pelvic radiographs of a complete biomechanical evaluation of patient hip and in his book and presented in 1987 in order to measure pressure and load in patient hip. This procedure has been in time forgotten , but after thorough study and taking advantage of computational power of iPhone and iPad and the unique power of X-code which allow us to calculate complex equations has make this sound biomechanical study- concept now available in simple iPhone in a sec to compute very complex and difficult equations by clicking few points in screen.
The App computes weight-bearing contact surface, the load (R) and stress (P) on the measured hip.
Data from load and pressure distribution in the hip - like in a real biomechanicals tests- are being measured and depicted graphically as vectors over the X-ray in the screen over the joint. The distribution also of compressive stresses over the acetabulum, which is usually associated radiographic sclerosis over the acetabular margin, are printed in real time over the screen and thus can be easily and objectively evaluated. Besides that, the App provides data in export for diagrams of load (R) pressure (P), which each can be plotted as a curve allowing easy comparison with normal data and thus help decide the orthopaedic surgeon which procedure is objectively indicated. More at www.orthopractis.com
Reference
1. Legal H (1977) Biomechanische Analyse des Hiiftgelenks. Ein Beitrag mit besonderer Berucksichtigung der Druckberechnung und der klinischen Anwendung. Habilitationsschrift, Universitat Erlangen Nurnberg.
2. Pauwels F (1935) Der Schenkelhalsbruch, ein mechanisches Problem. Grundlagen des Heilungsvorganges, Prognose und kausale Therapie. Z Orthop Chir 63 (Beilageheft).
3. Tönnis, Dietrich (1987) Dysplasia and Dislocation of the Hip in Children and Adults. Chapter 4, Current Knowledge on the Biomechanics of the Hip, page 26-57. Book
