title: Decreased Synovial Inflammation in Atraumatic Hip Microinstability Compared With Femoroacetabular Impingement.
abstract: OBJECTIVE
  To compare the inflammatory profile of hip synovial tissue in those with atraumatic microinstability to patients with femoroacetabular impingement (FAI).
  
  
  METHODS
  Patients with cam and mixed-type FAI (FAI group) and patients with hip instability underwent sampling of the anterolateral synovium. Demographic data, intraoperative measurements, and functional outcome scores (International Hip Outcomes Tool and Short Form-12) were recorded. Cryosections were stained and examined under light microscopy as well as confocal fluorescent microscopy for anti-CD45 (common leukocyte antigen), anti-CD31 (endothelial), and anti-CD68 (macrophage) cell surface markers. A grading system was used to quantify synovitis under light microscopy whereas digital image analysis was used to quantify immunofluorescence staining area. Comparison were made with Student t test, Mann-Whitney U, χ2, and regression analysis.
  
  
  RESULTS
  There were 12 patients in the FAI group and 5 in the instability group. Mean age was not significantly different (P > .05), but there was a significantly greater proportion of females in the instability group versus the FAI group (P < .001). There was a significant correlation (r = 0.653; P = .005) between number of turns needed for 10 mm of distraction and increased synovitis. Synovitis scores also were increased significantly in patients with cam morphology and articular cartilage damage (P = .024) versus those without. Immunohistochemistry did not reveal differences (P > .082) between the instability and FAI groups, but CD68 staining was significantly greater in those with cam morphology and cartilage damage (P < .045). CD45+/CD68- cells were noted in the perivascular area while CD45+/CD68+ cells were noted within the synovial lining in both groups.
  
  
  CONCLUSIONS
  Increased synovial inflammation was associated with an increased number of turns to achieve joint distraction. Both instability and FAI groups demonstrated baseline levels of synovial inflammation. Synovitis scores also were increased in patients with cartilage damage.
  
  
  CONCLUSIONS
  An understanding of the molecular and cellular mechanisms behind both hip instability and FAI may lead to novel therapeutic anti-inflammatory therapy, which may serve as an adjunct to treatment of mechanical abnormalities in this conditions.
authors.affiliation: Department of Orthopedic Surgery, Stanford University, Palo Alto, California, U.S.A.; Veterans Administration Palo Alto, Palo Alto, California, U.S.A.. Electronic address: gabrams@stanford.edu.
authors.forename: Geoffrey D
authors.initials: GD
authors.lastname: Abrams
authors.affiliation: Veterans Administration Palo Alto, Palo Alto, California, U.S.A.
authors.forename: Ayala
authors.initials: A
authors.lastname: Luria
authors.affiliation: Veterans Administration Palo Alto, Palo Alto, California, U.S.A.
authors.forename: Joshua
authors.initials: J
authors.lastname: Sampson
authors.affiliation: Veterans Administration Palo Alto, Palo Alto, California, U.S.A.
authors.forename: Rachel A
authors.initials: RA
authors.lastname: Madding
authors.affiliation: Rheumatology Division, Department of Medicine, Stanford University, Palo Alto, California, U.S.A.; Veterans Administration Palo Alto, Palo Alto, California, U.S.A.
authors.forename: William H
authors.initials: WH
authors.lastname: Robinson
authors.affiliation: Department of Orthopedic Surgery, Stanford University, Palo Alto, California, U.S.A.
authors.forename: Marc R
authors.initials: MR
authors.lastname: Safran
authors.affiliation: Rheumatology Division, Department of Medicine, Stanford University, Palo Alto, California, U.S.A.; Veterans Administration Palo Alto, Palo Alto, California, U.S.A.
authors.forename: Jeremy
authors.initials: J
authors.lastname: Sokolove
mesh_terms: D000328:Adult; D015703:Antigens, CD / Q000378:metabolism; D015214:Antigens, Differentiation, Myelomonocytic / Q000378:metabolism; D001182:Arthroscopy; D005260:Female; D057925:Femoracetabular Impingement / Q000473:pathology*; D005471:Fluoroscopy; D006621:Hip Joint / Q000473:pathology*; D006801:Humans; D007593:Joint Instability / Q000473:pathology*; D017493:Leukocyte Common Antigens / Q000378:metabolism; D008264:Macrophages / Q000378:metabolism; D008297:Male; D008853:Microscopy; D013585:Synovitis / Q000473:pathology*; D014143:Traction; D000097382:CD68 Molecule
chemical_list: D015703:Antigens, CD; D015214:Antigens, Differentiation, Myelomonocytic; D017493:Leukocyte Common Antigens; C067980:CD68 antigen, human; D000097382:CD68 Molecule; C516769:PTPRC protein, human