title: The effect of knee flexion and rotation on the tibial tuberosity-trochlear groove distance.
abstract: OBJECTIVE
  The purpose was to measure the effect of flexion and additional rotation of the femur relative to the tibia on the tuberosity-trochlear groove distance (TT-TG) in the same subject in 20 cadaveric knees joint.
  
  
  METHODS
  In 20 human adult cadavers, formal fixed knees (age: 81.9 years, SD 12.3; 10 female) CT scans were performed in extension and 30° of flexion as well as in neutral, maximal possible internal (IR), and external rotation (ER). On superimposed CT scan images, TT-TG was measured in each position. TT-TG measurements were correlated in all knee positions.
  
  
  RESULTS
  TT-TG in full extension/neutral rotation was 7.8 mm (SD 3.4, range, 2.4-15.3). TT-TG in full extension and IR was significantly lower, and TT-TG in full extension and ER was significantly higher than in neutral rotation (5.4 ± 2.3 vs. 10.9 ± 4.8 mm; P < 0.001). IR and ER varied between 1.0°-7.6° and 0.2°-9.2°, respectively. TT-TG in 30° flexion/neutral rotation was 3.9 mm (SD 1.8, range, 1.3-7.8), which was significantly lower than in full extension and neutral rotation (P < 0.001). TT-TG in 30° flexion and IR was significantly lower, and TT-TG in 30° flexion and ER was significantly higher than values obtained in neutral rotation (2.7 ± 1.2 vs. 6.5 ± 3.4 mm; P < 0.001). IR and ER in 30° flexion varied between 0.6°-10.7° and 1.9°-13.0°, respectively.
  
  
  CONCLUSIONS
  Flexion as well as rotation of the knee joint significantly alters the TT-TG. These results may have wider clinical relevance in assessing TT-TG and further decisions based on it.
authors.affiliation: Paediatric Orthopaedic Department, University Children's Hospital Basle (UKBB), Spitalstrasse 33, 4056, Basel, Switzerland. camathias.carlo@gmail.com.
authors.forename: Carlo
authors.initials: C
authors.lastname: Camathias
authors.affiliation: Orthopaedic Department, University of Basel, University Hospital Basel, Spitalstrasse 21, 4031, Basel, Switzerland.
authors.forename: Geert
authors.initials: G
authors.lastname: Pagenstert
authors.affiliation: Institute of Anatomy, University of Basel, Pestalozzistrasse 20, 4056, Basel, Switzerland.
authors.forename: Ulrich
authors.initials: U
authors.lastname: Stutz
authors.affiliation: Orthopaedic Department, University of Basel, University Hospital Basel, Spitalstrasse 21, 4031, Basel, Switzerland.
authors.forename: Alexej
authors.initials: A
authors.lastname: Barg
authors.affiliation: Institute of Anatomy, University of Basel, Pestalozzistrasse 20, 4056, Basel, Switzerland.
authors.forename: Magdalena
authors.initials: M
authors.lastname: Müller-Gerbl
authors.affiliation: Orthopaedic Department, University of Basel, University Hospital Basel, Spitalstrasse 21, 4031, Basel, Switzerland.|Institute of Anatomy, University of Basel, Pestalozzistrasse 20, 4056, Basel, Switzerland.
authors.forename: Andrej M
authors.initials: AM
authors.lastname: Nowakowski
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D005269:Femur / Q000000981:diagnostic imaging / Q000502:physiology*; D006801:Humans; D007719:Knee Joint / Q000000981:diagnostic imaging / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D016059:Range of Motion, Articular; D012399:Rotation; D013977:Tibia / Q000000981:diagnostic imaging / Q000502:physiology*; D014057:Tomography, X-Ray Computed
keywords: Cadaver; Femoro-patellar instability; Patellar instability; Rotation; Rotation instability; TT–TG; Tibial tuberosity–trochlear groove distance