title: Dynamic tracking influenced by anatomy in patellar instability.
abstract: BACKGROUND
  The current study was performed to correlate anatomical parameters related to trochlear dysplasia, tibial tuberosity position, and patella alta with in vivo patellar tracking for subjects with recurrent patellar instability.
  
  
  METHODS
  Eight subjects with recurrent patellar instability that failed conservative treatment were evaluated using computational reconstruction of in vivo knee motion. Computational models were created from dynamic CT scans of the knee during extension against gravity. Shape matching techniques were utilized to position a single model of each bone (femur, patella and tibia) to represent multiple positions of knee extension. Patellar tracking was characterized by the bisect offset index (lateral shift) and lateral tilt. Anatomical parameters were characterized by the inclination of the lateral ridge of the trochlear groove, the lateral distance from the tibial tuberosity to the posterior cruciate ligament attachment (lateral TT-PCL distance), and the Caton-Deschamps index. Stepwise multivariable linear regression analysis was used to relate patellar tracking to the anatomical parameters at low (<20°) and high flexion angles.
  
  
  RESULTS
  At low flexion angles, both lateral trochlear inclination and lateral TT-PCL distance were significantly correlated with bisect offset index (p=0.02). Only lateral trochlear inclination was significantly correlated with lateral tilt (p<0.001). At high flexion angles, bisect offset index and lateral tilt were correlated with only lateral TT-PCL distance (p≤0.02).
  
  
  CONCLUSIONS
  Parameters related to trochlear dysplasia and tibial tuberosity position were both related to patellar tracking, but the relationship changed with the flexion angle.
  
  
  CONCLUSIONS
  The anatomical parameters related to patellar tracking can be used to evaluate the risk of continued instability and guide surgical treatment.
authors.affiliation: Department of Research, Cleveland Clinic Akron General, 1 Akron General Ave, Akron 44307, OH, USA. Electronic address: john.elias@akrongeneral.org.
authors.forename: John J
authors.initials: JJ
authors.lastname: Elias
authors.affiliation: Northeast Ohio Medical University, 4209 St. Rt. 44, PO Box 95, Rootstown 44272, OH, USA.
authors.forename: Neil T
authors.initials: NT
authors.lastname: Soehnlen
authors.affiliation: Department of Research, Cleveland Clinic Akron General, 1 Akron General Ave, Akron 44307, OH, USA.
authors.forename: Loredana M
authors.initials: LM
authors.lastname: Guseila
authors.affiliation: Department of Orthopedic Surgery, Johns Hopkins University, 10753 Falls Rd., Suite 215, Baltimore 21093, MD, USA.
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Cosgarea
mesh_terms: D000328:Adult; D005260:Female; D005269:Femur / Q000000981:diagnostic imaging; D006801:Humans; D021621:Imaging, Three-Dimensional; D007593:Joint Instability / Q000000981:diagnostic imaging*; D007719:Knee Joint / Q000000981:diagnostic imaging*; D008297:Male; D010329:Patella / Q000000981:diagnostic imaging*; D031222:Patellar Dislocation / Q000000981:diagnostic imaging*; D016059:Range of Motion, Articular; D012008:Recurrence; D013977:Tibia / Q000000981:diagnostic imaging; D014057:Tomography, X-Ray Computed; D055815:Young Adult
keywords: Patellar instability; Patellar tracking; Tibial tuberosity; Trochlear dysplasia