title: Influence of knee flexion angle and weight bearing on the Tibial Tuberosity-Trochlear Groove (TTTG) distance for evaluation of patellofemoral alignment.
abstract: OBJECTIVE
  The aim of the present study was to investigate the influence of knee flexion and weight bearing on the Tibial Tuberosity-Trochlear Groove (TTTG) distance.
  
  
  METHODS
  Magnetic resonance imaging of the knee was carried out in 8 healthy volunteers. An open 0.25 T scanner equipped with a C-shaped permanent tilting magnet allowing examinations in weight-bearing conditions was used for the present investigation. A 3D gradient-echo sequence with axial slice orientation was obtained in a lying and an upright position with the knee straight and at 30° of knee flexion. The medial, central and lateral trochlear heights as well as the TTTG were determined.
  
  
  RESULTS
  The mean medial trochlear height was 76.2 ± 4%, the central trochlear height was 72.2 ± 3%, and lateral trochlear height was 82.9 ± 3 %. The mean TTTG distance was 11.6 ± 4.4 mm in lying position at 0° knee flexion and 7.3 ± 2.9 mm (n.s.) at 30° knee flexion. Under weight bearing, the mean TTTG was significantly smaller at both 0° knee flexion 6.3 ± 3.2 mm (p = 0.040) and 30° knee flexion 4.9 ± 3.9 mm (p = 0.006) compared to the lying position with 0° knee flexion.
  
  
  CONCLUSIONS
  Tibial Tuberosity-Trochlear Groove distance depends on both knee flexion angle and weight bearing. The latter only seems to be of relevance in full extension.
authors.affiliation: Department of Orthopedic and Trauma Surgery, University Medical Center Freiburg, Hugstetter Straße 55, 79106, Freiburg, Germany, izadpanah@me.com.
authors.forename: Kaywan
authors.initials: K
authors.lastname: Izadpanah
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Weitzel
authors.forename: Marco
authors.initials: M
authors.lastname: Vicari
authors.forename: Jürgen
authors.initials: J
authors.lastname: Hennig
authors.forename: Matthias
authors.initials: M
authors.lastname: Weigel
authors.forename: Norbert P
authors.initials: NP
authors.lastname: Südkamp
authors.forename: Philipp
authors.initials: P
authors.lastname: Niemeyer
mesh_terms: D000328:Adult; D005260:Female; D005269:Femur / Q000033:anatomy & histology* / Q000502:physiology; D006801:Humans; D007719:Knee Joint / Q000033:anatomy & histology* / Q000502:physiology; D008279:Magnetic Resonance Imaging; D008297:Male; D057071:Patellofemoral Joint / Q000033:anatomy & histology* / Q000502:physiology; D016059:Range of Motion, Articular; D013977:Tibia / Q000033:anatomy & histology* / Q000502:physiology; D016474:Weight-Bearing