title: Quantitative stress radiography of the patella and evaluation of patellar laxity before and after lateral release for recurrent dislocation patella.
abstract: OBJECTIVE
  The aims of the present controlled clinical study were to (1) compare patella laxity determined in the outpatient clinic with that in anaesthetized patients and (2) evaluate patella laxity before and after lateral release.
  
  
  METHODS
  The study evaluated data on 33 knees from 33 patients (average age 19.7 years) between 2007 and 2011. All patients were diagnosed with recurrent dislocation of the patella. Patellar stability was evaluated in each patient thrice: patellas were first imaged in the outpatient clinic prior to surgery at 45° knee flexion with 20 N stress from the medial to lateral side and from the lateral to medial side; then, at the time of surgery, patella stress images were obtained in the same manner before and after the lateral release procedure. Radiological assessments were performed using the medial stress shift ratio (MSSR) and lateral stress shift ratio (LSSR).
  
  
  RESULTS
  There were no significant differences in the LSSR and MSSR before surgery (outpatient data) and in anaesthetized patients before the lateral release procedure. Furthermore, there was no significant difference in MSSR at the time of surgery before and after the lateral release procedure. However, LSSR increased significantly after the lateral release procedure.
  
  
  CONCLUSIONS
  The results of the present study suggest that quantitative patella stress radiography in the outpatient clinic is useful when it comes to investigating laxity of the patella, and that lateral release significantly increases lateral, but not medial, laxity in patients with recurrent patellar dislocation.
  
  
  METHODS
  IV.
authors.affiliation: Department of Orthopaedic Surgery, Higashihiroshima Medical Center, 513 Jike, Saijyou-chou, Higashihiroshima, Hiroshima, Japan, takuniimoto@gmail.com.
authors.forename: Takuya
authors.initials: T
authors.lastname: Niimoto
authors.forename: Masataka
authors.initials: M
authors.lastname: Deie
authors.forename: Nobuo
authors.initials: N
authors.lastname: Adachi
authors.forename: Muhammad Andry
authors.initials: MA
authors.lastname: Usman
authors.forename: Mitsuo
authors.initials: M
authors.lastname: Ochi
mesh_terms: D000293:Adolescent; D000328:Adult; D002648:Child; D005260:Female; D006801:Humans; D007593:Joint Instability / Q000000981:diagnostic imaging*; D007719:Knee Joint / Q000601:surgery; D008297:Male; D008875:Middle Aged; D010329:Patella / Q000000981:diagnostic imaging* / Q000601:surgery; D031222:Patellar Dislocation / Q000000981:diagnostic imaging* / Q000601:surgery; D011859:Radiography; D055815:Young Adult