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

Validation of Mechanical Hypothesis of hip Arthritis Development by HIPSTRESS Method

“…Smaller lateral extension of the greater trochanter z and larger interhip distance l increase the magnitude of resultant hip force R/W B . Peak hip stress decreases with decreasing (ϑ CE + ϑ R ) up to (ϑ CE + ϑ R = π/2) and increases with increasing R/W B [25]. For low hip stress (ϑ CE + ϑ R ) is large enough that the curve p max r 2 /W B (ϑ CE +ϑ R ) is almost flat, mostly on the account of large ϑ CE .…”

“…Model for contact hip stress was thorougly described in a previous contribution [24] and will be only briefly described here. Femoral head is represented by a part of the sphere and acetabulum is represented by a part of the spherical shell.…”

“…the medial border is for the angle π/2 allienated from the stress pole. The connection between the resultant hip force and the hip stress distribution , p = ò R dA (5) where the integration is performed over the load bearing area, yields three equations for three unknowns: the angles defining the position of the hip stress pole (Θ and Φ) and the value of stress at the pole p 0 [20,24] 0, , F = p…”

Understanding Hip Biomechanics: From Simple Equilibrium to Personalized HIPSTRESS Method

“…The model HIPSTRESS for contact hip stress has previously been described in detail in Ref. [5]; therefore, only brief description will be given here. The readers who wish to understand the derivation of the equations are kindly asked to refer to the pointed literature.…”

“…In the first case, the peak stress is identical to the value of stress at the pole p max ¼ p 0 , while in the second case, the peak stress is taken at the point on the load-bearing area that is closest to the stress pole. If this takes place at the acetabular rim, the peak stress is calculated according to the expression p max ¼ p 0 cos ðϑ CE À ΘÞ [5]. It was shown that biomechanical parameters calculated with HIPSTRESS models for resultant hip force and contact hip stress were useful in explaining early osteoarthritis in dysplastic hips [7], hips with primary osteoarthritis, hips subject to avascular necrosis of the femoral head [5], hips that were in childhood subject to the Perthes disease [8], effect of different osteotomies [9][10][11][12], and the direction and volumetric wear of total hip endoprosthesis [13].…”