title: The adductor tubercle as an important landmark to determine the joint line level in total knee arthroplasty: from radiographs to surgical theatre.
abstract: OBJECTIVE
  The restoration of the normal joint line (JL) is important both in primary and revision total knee arthroplasty (TKA). However, the assessment of the femoro-tibial JL is still controversial. A strong correlation between femoral width (FW) and distance from adductor tubercle (AT) to JL was found on radiographs, with a ratio of 0.54. The hypothesis was that this ratio was applicable also in the surgical theatre by using measurements obtained intra-operatively with a caliper.
  
  
  METHODS
  Femoral width, AT to JL distance and the RATIO between AT to JL distance and FW of 40 patients who underwent TKA were measured on radiograph and intra-operatively. Bland-Altman agreement tests with repeated measurements and linear regression analysis were used. The ratio was used to estimate the distance between JL and AT.
  
  
  RESULTS
  The AT to JL distance/FW ratio calculated with linear regression resulted 0.54 for radiographic measurements and 0.53 for intra-operative measurements. There was no difference (0.009 ± 0.03) between the calculated ratios on radiographic and intra-operative measurements, and the correlation between intra-operative and radiographic measurements was 0.5 (p = 0.0016).
  
  
  CONCLUSIONS
  This study shows that the validity of the radiographic method which uses an AT to JL distance/FW ratio to determine the level of the JL is confirmed also when using intra-operatively acquired measurements. Thus, this ratio represents a reliable tool to determine the JL level even in challenging prosthetic revision cases when the anatomical JL is missing.
  
  
  METHODS
  Case series, Level IV.
authors.affiliation: 2nd Orthopaedics and Traumatologic Clinic, Rizzoli Orthopaedic Institute, Via Pupilli 1, 40136, Bologna, Italy, f.iacono@biomec.ior.it.
authors.forename: F
authors.initials: F
authors.lastname: Iacono
authors.forename: G F
authors.initials: GF
authors.lastname: Raspugli
authors.forename: D
authors.initials: D
authors.lastname: Bruni
authors.forename: G
authors.initials: G
authors.lastname: Filardo
authors.forename: S
authors.initials: S
authors.lastname: Zaffagnini
authors.forename: W F
authors.initials: WF
authors.lastname: Luetzow
authors.forename: M
authors.initials: M
authors.lastname: Lo Presti
authors.forename: I
authors.initials: I
authors.lastname: Akkawi
authors.forename: G M
authors.initials: GM
authors.lastname: Marcheggiani Muccioli
authors.forename: M
authors.initials: M
authors.lastname: Marcacci
mesh_terms: D000368:Aged; D019645:Arthroplasty, Replacement, Knee / Q000379:methods*; D001837:Body Weights and Measures; D005260:Female; D005269:Femur / Q000000981:diagnostic imaging / Q000601:surgery*; D006801:Humans; D007432:Intraoperative Period; D007719:Knee Joint / Q000000981:diagnostic imaging / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D020370:Osteoarthritis, Knee / Q000000981:diagnostic imaging / Q000601:surgery*; D011300:Preoperative Care; D011859:Radiography; D015203:Reproducibility of Results; D013977:Tibia / Q000000981:diagnostic imaging / Q000601:surgery*