title: Inflammation and Neovascularization in Hip Impingement: Not Just Wear and Tear.
abstract: BACKGROUND
  Femoroacetabular impingement (FAI) is a significant cause of osteoarthritis (OA) in young active patients, but the pathophysiology remains unclear. Increasingly, mechanistic studies point toward an inflammatory component in OA.
  
  
  OBJECTIVE
  This study aimed to characterize inflammatory cell subtypes and neovascularization in FAI by exploring the phenotype and quantification of inflammatory cells and neovascularization in FAI versus OA samples.
  
  
  METHODS
  Descriptive laboratory study.
  
  
  METHODS
  Ten samples of the labrum were obtained from patients with FAI (confirmed diagnosis) during open osteochondroplasty or hip arthroscopic surgery. Control samples of the labrum were collected from 10 patients with OA who were undergoing total hip arthroplasty. Labral biopsy specimens were evaluated immunohistochemically by quantifying the presence of macrophages (CD68, CD206, interleukin-13 [IL-13]), T cells (CD3), mast cells (mast cell tryptase), and vascular endothelium (CD34, vascular endothelial growth factor).
  
  
  RESULTS
  Labral biopsy specimens obtained from patients with FAI exhibited significantly greater macrophage, mast cell, and vascular endothelium expression compared with control OA labral samples (P < .05). The most significant difference was noted in macrophage (P < .01) and mast cell (P < .05) expression. Further subtyping of macrophages in FAI using the CD206 tissue marker and IL-13 revealed an M2 phenotype, suggesting that these cells are involved in a regenerate versus degenerate process. There was a modest but significant correlation between mast cells and CD34 expression (r = 0.4, P < .01) in FAI samples.
  
  
  CONCLUSIONS
  This study provides evidence for an inflammatory cell infiltrate in FAI along with significant neovascularization. In particular, the significant infiltration of mast cells and macrophages was demonstrated, suggesting a role for innate immune pathways in the events that mediate hip impingement.
  
  
  CONCLUSIONS
  Further mechanistic studies to evaluate the net contribution and hence therapeutic utility of these cellular lineages and their downstream processes may reveal novel therapeutic approaches to the management of early hip impingement.
authors.affiliation: Institute of Infection, Immunity and Inflammation, College of Medicine, Veterinary and Life Sciences, University of Glasgow, Glasgow, UK Department of Orthopaedic Surgery, Southern General Hospital, Glasgow, UK.
authors.forename: Cameron J
authors.initials: CJ
authors.lastname: Elias-Jones
authors.affiliation: Institute of Infection, Immunity and Inflammation, College of Medicine, Veterinary and Life Sciences, University of Glasgow, Glasgow, UK.
authors.forename: Luke
authors.initials: L
authors.lastname: Farrow
authors.affiliation: Institute of Infection, Immunity and Inflammation, College of Medicine, Veterinary and Life Sciences, University of Glasgow, Glasgow, UK.
authors.forename: James H
authors.initials: JH
authors.lastname: Reilly
authors.affiliation: Institute of Infection, Immunity and Inflammation, College of Medicine, Veterinary and Life Sciences, University of Glasgow, Glasgow, UK.
authors.forename: Shauna
authors.initials: S
authors.lastname: Kerr
authors.affiliation: Department of Orthopaedic Surgery, Southern General Hospital, Glasgow, UK.
authors.forename: R M Dominic
authors.initials: RM
authors.lastname: Meek
authors.affiliation: Department of Orthopaedic Surgery, Western Infirmary, Glasgow, UK.
authors.forename: Michael P
authors.initials: MP
authors.lastname: Kelly
authors.affiliation: Department of Orthopaedic Surgery, Western Infirmary, Glasgow, UK.
authors.forename: J Luke
authors.initials: JL
authors.lastname: Campton
authors.affiliation: Institute of Infection, Immunity and Inflammation, College of Medicine, Veterinary and Life Sciences, University of Glasgow, Glasgow, UK Department of Orthopaedic Surgery, Western Infirmary, Glasgow, UK neal.millar@glasgow.ac.uk.
authors.forename: Neal L
authors.initials: NL
authors.lastname: Millar
mesh_terms: D000328:Adult; D019644:Arthroplasty, Replacement, Hip / Q000379:methods; D001182:Arthroscopy / Q000379:methods; D057925:Femoracetabular Impingement / Q000150:complications / Q000503:physiopathology* / Q000601:surgery; D006801:Humans; D007249:Inflammation / Q000473:pathology*; D008875:Middle Aged; D009389:Neovascularization, Pathologic / Q000473:pathology*; D010003:Osteoarthritis / Q000209:etiology*; D042461:Vascular Endothelial Growth Factor A / Q000378:metabolism; D055815:Young Adult
chemical_list: D042461:Vascular Endothelial Growth Factor A
keywords: femoroacetabular; hip; impingement; inflammation; young adults