title: Correlation of the tibial tuberosity-trochlear groove distance with the Q-angle.
abstract: OBJECTIVE
  The Q-angle has been used for years to quantify lateralization of the patella. The tibial tuberosity-trochlea groove distance (TT-TG distance) was introduced to analyse patellar tracking. Does a significant correlation exist between these two parameters? Do other significant interrelations exist between the Q-angle/TT-TG distance, torsion of the femur and tibia, the frontal axis, overall leg length, gender, former patellar dislocation, BMI?
  
  
  METHODS
  One hundred knees in 55 patients with patellofemoral symptoms were included in a prospective study. All patients underwent clinical examination, including measurement of the Q-angle. A torsional CT was obtained from all patients.
  
  
  RESULTS
  The correlation coefficient was 0.33/0.34 (left/right leg), showing that the TT-TG distance tends to rise in direct ratio to a rising Q-angle. Thus, a significant correlation was found (p = 0.017). Femoral and tibial torsion had a positive effect on the TT-TG distance, but showed no significant correlation. Leg length had a significant effect on the TT-TG distance (p = 0.04). The frontal axis had a nonsignificant influence on the Q-angle or TT-TG distance. On average, the Q-angle in women was 2.38° greater than it was in men, but the difference was not significant.
  
  
  CONCLUSIONS
  A significant correlation was noted between the Q-angle and the TT-TG distance. Both depend on various parameters and must be assessed for the analysis of patellofemoral maltracking. The Q-angle did not differ significantly between men and women; thus, the conclusion is that no different ranges need not be used.
  
  
  METHODS
  Diagnostic study, Level III.
authors.affiliation: Klinik für Orthopädie und Unfallchirurgie, Klinikum Bamberg, Buger Strasse 80, 96049, Bamberg, Germany. Joerg.dickschas@sozialstiftung-bamberg.de.
authors.forename: Jörg
authors.initials: J
authors.lastname: Dickschas
authors.affiliation: Klinik für Orthopädie und Unfallchirurgie, Klinikum Bamberg, Buger Strasse 80, 96049, Bamberg, Germany. joerg.harrer@sozialstiftung-bamberg.de.
authors.forename: Jörg
authors.initials: J
authors.lastname: Harrer
authors.affiliation: Radiologisches Institut, Universitätsklinikum Erlangen, Maximiliansplatz 1, 91054, Erlangen, Germany. thomas.bayer@uk-erlangen.de.
authors.forename: Thomas
authors.initials: T
authors.lastname: Bayer
authors.affiliation: Institut für Medizininformatik, Biometrie und Epidemiologie, Friedrich-Alexander-Universität Erlangen-Nürnberg, Waldstr. 6, 91054, Erlangen, Germany. judith.schwitulla@fau.de.|, Universitätsstr. 22, 91052, Erlangen, Germany. judith.schwitulla@fau.de.
authors.forename: Judith
authors.initials: J
authors.lastname: Schwitulla
authors.affiliation: Klinik für Orthopädie und Unfallchirurgie, Klinikum Bamberg, Buger Strasse 80, 96049, Bamberg, Germany. wolf.strecker@sozialstiftung-bamberg.de.
authors.forename: Wolf
authors.initials: W
authors.lastname: Strecker
mesh_terms: D000328:Adult; D017760:Bone Malalignment / Q000000981:diagnostic imaging; D005260:Female; D005269:Femur / Q000000981:diagnostic imaging*; D006801:Humans; D007593:Joint Instability / Q000000981:diagnostic imaging; D007719:Knee Joint / Q000000981:diagnostic imaging; D008297:Male; D008875:Middle Aged; D010329:Patella / Q000000981:diagnostic imaging*; D031222:Patellar Dislocation / Q000000981:diagnostic imaging; D057071:Patellofemoral Joint / Q000000981:diagnostic imaging*; D011446:Prospective Studies; D013977:Tibia / Q000000981:diagnostic imaging*; D014057:Tomography, X-Ray Computed
keywords: Lower limb alignment; Patellar instability; Patellofemoral imbalance; Q-angle; TT–TG distance; Tibial tuberosity–trochlear groove distance