title: Impact of hip anatomical variations on the cartilage stress: a finite element analysis towards the biomechanical exploration of the factors that may explain primary hip arthritis in morphologically normal subjects.
abstract: BACKGROUND
  Hip arthritis is a pathology linked to hip-cartilage degeneration. Although the etiology of this disease is not well defined, it is known that age is a determinant risk factor. However, hip arthritis in young patients could be largely promoted by biomechanical factors. The objective of this paper is to analyze the impact of some normal anatomical variations on the cartilage stress distributions numerically predicted at the hip joint during walking.
  
  
  METHODS
  A three-dimensional finite element model of the femur and the pelvis with the most relevant axial components of muscle forces was used to simulate normal walking activity. The hip anatomical condition was defined by: neck shaft angle, femoral anteversion angle, and acetabular anteversion angle with a range of 110-130°, 0-20°, and 0-20°, respectively. The direct boundary method was used to simulate the hip contact.
  
  
  RESULTS
  The hydrostatic stress found at the cartilage and labrum showed that a ±10° variation with respect to the reference brings significant differences between the anatomic models. Acetabular anteversion angle of 0° and femoral anteversion angle of 0° were the most affected anatomical conditions with values of hydrostatic stress in the cartilage near 5MPa under compression.
  
  
  CONCLUSIONS
  Cartilage stresses and contact areas were equivalent to the results found in literature and the most critical anatomical regions in terms of tissue loads were in a good accordance with clinical evidence. Altogether, results showed that decreasing femoral or acetabular anteversion angles isolatedly causes a dramatic increase in cartilage loads.
authors: Biomechanics and Mechanobiology, Institute for Bioengineering of Catalonia, Spain.
authors: Antonio J
authors: AJ
authors: Sánchez Egea
authors: Department of Orthopedic and Traumatology, Santa Creu i Sant Pau Hospital, Universitat Autonoma de Barcelona, Spain.
authors: Marius
authors: M
authors: Valera
authors: Biomechanics and Mechanobiology, Institute for Bioengineering of Catalonia, Spain.
authors: Juan Manuel
authors: JM
authors: Parraga Quiroga
authors: Department of Orthopedic and Traumatology, Santa Creu i Sant Pau Hospital, Universitat Autonoma de Barcelona, Spain.
authors: Ignasi
authors: I
authors: Proubasta
authors: Biomechanics and Mechanobiology, Institute for Bioengineering of Catalonia, Spain.
authors: Jérôme
authors: J
authors: Noailly
authors: Biomechanics and Mechanobiology, Institute for Bioengineering of Catalonia, Spain; INSIGNEO Institute for in silico Medicine, Department of Mechanical Engineering, University of Sheffield, United Kingdom. Electronic address: d.lacroix@sheffield.ac.uk.
authors: Damien
authors: D
authors: Lacroix
mesh_terms: D000077:Acetabulum / Q000033:anatomy & histology*; D000369:Aged, 80 and over; D001696:Biomechanical Phenomena; D002358:Cartilage, Articular / Q000502:physiology*; D005260:Female; D005269:Femur / Q000033:anatomy & histology*; D020342:Finite Element Analysis; D006621:Hip Joint / Q000033:anatomy & histology* / Q000502:physiology*; D006801:Humans; D008953:Models, Anatomic; D013314:Stress, Mechanical; D016474:Weight-Bearing / Q000502:physiology
keywords: Cartilage load; Femoral and acetabular anteversions; Finite element analysis; Hip arthritis; Hip joint contact; Neck shaft angle