title: Mechanical factors explain development of cam-type deformity.
abstract: OBJECTIVE
  A cam-type deformity drastically increases the risk of hip osteoarthritis (OA). Since this type of skeletal anomaly is more prevalent among young active adults, it is hypothesized that the loading conditions experienced during certain types of vigorous physical activities stimulates formation of cam-type deformity. We further hypothesize that the growth plate shape modulates the influence of mechanical factors on the development of cam-type deformity.
  
  
  METHODS
  We used finite element (FE) models of the proximal femur with an open growth plate to study whether mechanical factors could explain the development of cam-type deformity in adolescents. Four different loading conditions (representing different types of physical activities) and three different levels of growth plate extension towards the femoral neck were considered. Mechanical stimuli at the tissue level were calculated by means of the osteogenic index (OI) for all loading conditions and growth plate shape variations.
  
  
  RESULTS
  Loading conditions and growth plate shape influence the distribution of OI in hips with an open growth plate, thereby driving the development of cam-type deformity. In particular, specific types of loads experienced during physical activities and a larger growth plate extension towards the femoral neck increase the chance of cam-type deformity.
  
  
  CONCLUSIONS
  Specific loading patterns seem to stimulate the development of cam-type deformity by modifying the distribution of the mechanical stimulus. This is in line with recent clinical studies and reveals mechanobiological mechanisms that trigger the development of cam-type deformity. Avoiding these loading patterns during skeletal growth might be a potential preventative strategy for future hip OA.
authors.affiliation: Department of Biomechanical Engineering, Faculty of Mechanical, Maritime, and Materials Engineering, Delft University of Technology, Mekelweg 2, Delft 2628 CD, The Netherlands. Electronic address: paulineroels@gmail.com.
authors.forename: P
authors.initials: P
authors.lastname: Roels
authors.affiliation: Department of Orthopedics, Erasmus Medical Center, Rotterdam, The Netherlands. Electronic address: r.agricola@erasmusmc.nl.
authors.forename: R
authors.initials: R
authors.lastname: Agricola
authors.affiliation: Department of Radiology, Erasmus Medical Center, Rotterdam, The Netherlands. Electronic address: e.oei@erasmusmc.nl.
authors.forename: E H
authors.initials: EH
authors.lastname: Oei
authors.affiliation: Department of Biomechanical Engineering, Faculty of Mechanical, Maritime, and Materials Engineering, Delft University of Technology, Mekelweg 2, Delft 2628 CD, The Netherlands; Department of Orthopedics, University Medical Center, Utrecht, The Netherlands; Department of Rheumatology, University Medical Center, Utrecht, The Netherlands. Electronic address: H.H.Weinans@umcutrecht.nl.
authors.forename: H
authors.initials: H
authors.lastname: Weinans
authors.affiliation: Department of Biomechanical Engineering, Faculty of Mechanical, Maritime, and Materials Engineering, Delft University of Technology, Mekelweg 2, Delft 2628 CD, The Netherlands. Electronic address: g.campoli@tudelft.nl.
authors.forename: G
authors.initials: G
authors.lastname: Campoli
authors.affiliation: Department of Biomechanical Engineering, Faculty of Mechanical, Maritime, and Materials Engineering, Delft University of Technology, Mekelweg 2, Delft 2628 CD, The Netherlands. Electronic address: a.a.zadpoor@tudelft.nl.
authors.forename: A A
authors.initials: AA
authors.lastname: Zadpoor
mesh_terms: D001696:Biomechanical Phenomena; D002648:Child; D057925:Femoracetabular Impingement / Q000150:complications*; D005272:Femur Neck / Q000002:abnormalities*; D006132:Growth Plate / Q000002:abnormalities; D006801:Humans; D008297:Male; D016474:Weight-Bearing
keywords: Cam femoroacetabular impingement; Etiology; Finite element method; Growth plate shape; Mechanical loading