title: Is the hip capsule thicker in diseased hips?
abstract: OBJECTIVE
  The purpose of this study was to compare the thickness of the hip capsule in patients with surgical hip disease, either with cam-femoroacetabular impingement (FAI) or non-FAI hip pathology, with that of asymptomatic control hips.
  
  
  METHODS
  A total of 56 hips in 55 patients underwent a 3Tesla MRI of the hip. These included 40 patients with 41 hips with arthroscopically proven hip disease (16 with cam-FAI; nine men, seven women; mean age 39 years, 22 to 58) and 25 with non-FAI chondrolabral pathology (four men, 21 women; mean age 40 years, 18 to 63) as well as 15 asymptomatic volunteers, whose hips served as controls (ten men, five women; mean age 62 years, 33 to 77). The maximal capsule thickness was measured anteriorly and superiorly, and compared within and between the three groups with a gender subanalysis using student's t-test. The correlation between alpha angle and capsule thickness was determined using Pearson's correlation coefficient.
  
  
  RESULTS
  Superiorly, the hip capsule was significantly greater in cam- (p = 0.028) and non-FAI (p = 0.048) surgical groups compared with the asymptomatic group. Within groups, the superior capsule thickness was significantly greater than the anterior in cam- (p < 0.001) and non-FAI (p < 0.001) surgical groups, but not in the control group. There was no significant correlation between the alpha angle and capsule thickness. There were no gender differences identified in the thickness of the hip capsule.
  
  
  CONCLUSIONS
  The thickness of the capsule does not differ between cam- and non-FAI diseased hips, and thus may not be specific for a particular aetiology of hip disease. The capsule is, however, thicker in diseased surgical hips compared with asymptomatic control hips.Cite this article: K. S. Rakhra, A. A. Bonura, R. Nairn, M. E. Schweitzer, N. M. Kolanko, P. E. Beaule. Is the hip capsule thicker in diseased hips? Bone Joint Res 2016;5:586-593. DOI: 10.1302/2046-3758.511.2000495.
authors.affiliation: Associate Professor, The Ottawa Hospital/Ottawa Hospital Research Institute, General Campus, 501 Smyth Road, Ottawa, Ontario, K1H 8L6, Canada krakhra@toh.on.ca.
authors.forename: K S
authors.initials: KS
authors.lastname: Rakhra
authors.affiliation: Liverpool and Campbelltown Hospital, Locked Bag 7103, Liverpool, Australia.
authors.forename: A A
authors.initials: AA
authors.lastname: Bonura
authors.affiliation: Sir Charles Gairdner Hospital, Hospital Avenue, Nedlands, Western Australia.
authors.forename: R
authors.initials: R
authors.lastname: Nairn
authors.affiliation: Stony Brook University, HSC Level 4 - Room 120, 100 Nicolls Road; Stony Brook, New York, USA.
authors.forename: M E
authors.initials: ME
authors.lastname: Schweitzer
authors.affiliation: Stony Brook University, HSC Level 4 - Room 120, 100 Nicolls Road; Stony Brook, New York, USA.
authors.forename: N M
authors.initials: NM
authors.lastname: Kolanko
authors.affiliation: Department of Medical Imaging, The Ottawa Hospital, General Campus, 501 Smyth Road, Ottawa, Ontario, K1H 8L6, Canada.
authors.forename: P E
authors.initials: PE
authors.lastname: Beaule
keywords: Alpha angle; Cam; Femoroacetabular impingement; Hip capsule; Hip joint