Role of Biomechanical Parameters in Hip Osteoarthritis and Avascular Necrosis of Femoral Head

It is considered that living organisms are subject to physical laws. Forces and stresses importantly influence the development of tissues and cells. In order to manipulate physiological and patophysiological states of the organism, it is necessary to understand the underlying mechanisms. Experience has led to mechanical hypothesis stating that some diseases or disorders are a consequence of unfavorable load distribution which is expressed by biomechanical parameters (e.g. forces, stresses, load bearing areas). Since 1993 we have considered contact stress in the hip joint. We took part in development of a mathematical model for determination of the contact hip stress distribution (Iglic (1993b); Ipavec (1999)) and in population studies which were performed to validate themodel. Different diseases and disorders of the hip were considered by this model: hip dysplasia (Mavcic (2002; 2008); Pompe (2003; 2007)), slipped epiphysis of the femoral head (Zupanc (2008)), avascular necrosis of the femoral head (Daniel (2006); Dolinar (2003)), postoperative changes in hip geometry (Herman (2002); Kralj (2005); Vengust (2001)) and osteoarthritis of the hip (Recnik (2007; 2009a;b)). The method HIPSTRESS was put forward consisting of mathematical model for resultant hip force (Iglic (1990; 1993a)), mathematical model for contact hip stress (Iglic (1993b); Ipavec (1999)) and the corresponding software. Themodels require as an input geometrical parameters of the hip and pelvis. These parameters can be assessed from images as for example from standard anteroposterior radiograms. As appropriate images are available from clinical practice and from the archives, prospective and retrospective studies of the development of different diseases can be performed. A thorough survey on resultant hip force and the corresponding stress has recently been published (Daniel (2011)).