title: Variability of the Ischiofemoral Space Relative to Femur Position: An Ultrasound Study.
abstract: BACKGROUND
  Ischiofemoral impingement is caused by compression of the quadratus femoris muscle between the ischial tuberosity and lesser trochanter. The evaluation of ischiofemoral impingement includes radiologic studies to evaluate the ischiofemoral space dimensions. No prior study has evaluated the effect of femoral position on ischiofemoral space dimensions.
  
  
  OBJECTIVE
  To determine whether the dimensions of the ischiofemoral space vary with changes in femoral position.
  
  
  METHODS
  Cross-sectional study.
  
  
  METHODS
  Academic institution.
  
  
  METHODS
  Six male and four female subjects with no hip pain and no history of hip disorders or surgery were selected to participate in the study. The subjects' mean age was 31.5 years; mean height, 176.8 cm; mean weight, 70.2 kg; and mean body mass index, 23.6 kg/m(2).
  
  
  METHODS
  Ultrasound was used to measure the ischiofemoral space in bilateral gluteal regions of each volunteer. The volunteers underwent imaging in a prone position. The ischiofemoral space was measured with the femur in 9 different positions created through various combinations of frontal (15° abduction, neutral, and 15° adduction) and transverse (30° internal rotation, neutral, and 30° external rotation) plane hip motions.
  
  
  METHODS
  The narrowest ischiofemoral interval, defined as the narrowest distance between the medial cortex of the lesser trochanter and the lateral cortex of the ischial tuberosity.
  
  
  RESULTS
  The anatomic landmarks used to measure the ischiofemoral space were easily identified in all subjects. The frontal plane main effect (F2,18 = 38.611) was statistically significant (P < .001), as was the transverse plane main effect (F2,18 = 82.452, P < .001). These findings indicated that there was a statistically significant difference in ischiofemoral space according to hip position in the frontal and transverse planes. The largest ischiofemoral space measurement occurred with the hip in abduction and internal rotation (51.8 mm; 95% confidence interval [CI], 49.2-54.5 mm), whereas hip adduction and external rotation resulted in the narrowest ischiofemoral space measurement (30.8 mm; 95% CI, 25.5-36.0 mm). The largest difference was between the adduction-external rotation and the abduction-internal rotation positions (mean difference = 21.1 mm; 95% CI, 13.7-28.5 mm; P < .001), and the smallest difference was between the adducted-neutral rotation and the abducted-external rotation positions (mean difference = 0.23 mm; 95% CI, -8.07-8.55 mm; P = .99).
  
  
  CONCLUSIONS
  Femoral position affects ischiofemoral space dimensions. The ischiofemoral space widens with abduction and internal rotation and narrows with adduction and external rotation, and thus femoral position should be considered when imaging and measuring the ischiofemoral space.
authors.affiliation: Department of Physical Medicine and Rehabilitation, Mayo Clinic Sports Medicine Center, 600 Hennepin Ave, #310, Minneapolis, MN 55403; Department of Physical Medicine and Rehabilitation, University of California Davis School of Medicine, Sacramento, CA.
authors.forename: Jonathan T
authors.initials: JT
authors.lastname: Finnoff
authors.affiliation: Department of Radiology, Mayo Clinic, Rochester, MN.
authors.forename: Jeffrey R
authors.initials: JR
authors.lastname: Bond
authors.affiliation: Department of Radiology, Mayo Clinic, Rochester, MN.
authors.forename: Mark S
authors.initials: MS
authors.lastname: Collins
authors.affiliation: Department of Physical Medicine and Rehabilitation, Mayo Clinic Sports Medicine Center, 600 Hennepin Ave, #310, Minneapolis, MN 55403.
authors.forename: Jacob L
authors.initials: JL
authors.lastname: Sellon
authors.affiliation: Department of Physical Medicine and Rehabilitation, Mayo Clinic, Rochester, MN.
authors.forename: John H
authors.initials: JH
authors.lastname: Hollman
authors.affiliation: Department of Physical Medicine & Rehabilitation, University of Minnesota, Minneapolis, MN.
authors.forename: Michael K
authors.initials: MK
authors.lastname: Wempe
authors.affiliation: Department of Physical Medicine and Rehabilitation, Mayo Clinic Sports Medicine Center, 600 Hennepin Ave, #310, Minneapolis, MN 55403.
authors.forename: Jay
authors.initials: J
authors.lastname: Smith
mesh_terms: D000328:Adult; D059925:Anatomic Landmarks / Q000000981:diagnostic imaging*; D003430:Cross-Sectional Studies; D005260:Female; D057925:Femoracetabular Impingement / Q000000981:diagnostic imaging*; D005269:Femur / Q000000981:diagnostic imaging*; D064368:Healthy Volunteers; D006621:Hip Joint / Q000000981:diagnostic imaging*; D006801:Humans; D007512:Ischium / Q000000981:diagnostic imaging*; D008297:Male; D008875:Middle Aged; D014463:Ultrasonography