title: Femoral subchondral bone properties of patients with cam-type femoroacetabular impingement.
abstract: Morphological deformities of the hip, such as femoroacetabular impingement (FAI) may be responsible for up to 80% of hip osteoarthritis. In cam type FAI, the pathomechanism has been attributed to repeated abnormal contact between the femur and the antero-superior acetabular rim, resulting in cartilage and labrum degeneration. Subchondral bone stiffness likely plays a major role in the process, but little is known of the mechanical properties of the cam deformity. The purpose of this study was to determine tissue modulus and the trabecular micro-architecture of the subchondral bone of the cam deformity of patients undergoing resection surgery as well as comparing these parameters to healthy aged matched controls.
  
  
  
  Twelve osteochondral bone biopsies were obtained from symptomatic FAI patients and ten osteochondral control specimens were harvested from cadaveric femurs. A combination of mechanical testing, micro-CT and finite element (FE) analysis were used to determine tissue modulus, bone volume fraction, trabecular thickness, trabecular and spacing, and trabecular number.
  
  
  
  The mean tissue modulus of the cam-type FAI deformities (E = 5.4 GPa) was significantly higher than normal controls (E = 2.75 GPa, P = 0.038), but no statistically significant differences were found in bone micro-architectural parameters.
  
  
  
  The data suggests that subchondral bone of the cam deformity consists of older secondary mineralized bone. This supports the notion that the cam deformity is a primary malformation with intrinsic biomechanical abnormalities rather than a secondary deformity as part of the degenerative process of the covering cartilage or remodeling due to repeated impingement.
authors.affiliation: Department of Mechanical and Aerospace Engineering, Carleton University, 1125 Colonel By Drive, Ottawa, ON, K1S 5B6, Canada. Electronic address: ifaz.haider@gmail.com.
authors.forename: I
authors.initials: I
authors.lastname: Haider
authors.affiliation: Department of Mechanical and Aerospace Engineering, Carleton University, 1125 Colonel By Drive, Ottawa, ON, K1S 5B6, Canada. Electronic address: andrew.speirs@carleton.ca.
authors.forename: A
authors.initials: A
authors.lastname: Speirs
authors.affiliation: Department of Mechanical and Aerospace Engineering, Carleton University, 1125 Colonel By Drive, Ottawa, ON, K1S 5B6, Canada. Electronic address: aalnabel@gmail.com.
authors.forename: A
authors.initials: A
authors.lastname: Alnabelseya
authors.affiliation: Division of Orthopaedic Surgery, Department of Surgery, The Ottawa Hospital General Campus, University of Ottawa, 501 Smyth Road, Ottawa, ON, K1H 8L6, Canada. Electronic address: pbeaule@ottawahospital.on.ca.
authors.forename: P E
authors.initials: PE
authors.lastname: Beaulé
authors.affiliation: Department of Mechanical and Aerospace Engineering, Carleton University, 1125 Colonel By Drive, Ottawa, ON, K1S 5B6, Canada. Electronic address: hanspeter.frei@carleton.ca.
authors.forename: H
authors.initials: H
authors.lastname: Frei
mesh_terms: D001842:Bone and Bones; D057925:Femoracetabular Impingement; D005269:Femur; D020342:Finite Element Analysis; D006801:Humans; D015207:Osteoarthritis, Hip
keywords: Femoroacetabular impingement; Finite element; Subchondral bone; Tissue modulus