title: Patellar tracking after isolated medial patellofemoral ligament reconstruction: dynamic evaluation using computed tomography.
abstract: OBJECTIVE
  Medial patellofemoral ligament (MPFL) reconstruction offers good clinical results with a very low rate of instability recurrence. However, its in vivo effect on patellar tracking is not clearly known. The aim of this study is to investigate the effects of MPFL reconstruction on patellar tracking using dynamic 320-detector-row CT.
  
  
  METHODS
  Ten patients with patellofemoral instability referred to isolated MPFL reconstruction surgery were selected and subjected to dynamic CT before and ≥6 months after surgery. Patellar tilt angles and shift distance were analysed using computer software specifically designed for this purpose. Kujala and Tegner scores were applied, and the radiation of the CTs was recorded. Two protocols for imaging acquisition were compared: a tube potential of 80 kV and 50 mA versus a tube potential of 120 kV and 100 mA, both with a slice thickness of 0.5 mm and an acquisition duration of 10 s.
  
  
  RESULTS
  There were no changes in patellar tracking after MPFL reconstruction. There was no instability relapse. Clinical scores improved from a mean of 51.9 (±15.6)-74.2 (±20.9) on the Kujala scale (p = 0.011) and from a median of 2 (range 0-4) to 4 (range 1-6) on the Tegner scale (p = 0.017). The imaging protocols produced a dose-length product (DLP) of 254 versus 1617 mGycm and a radiation effective estimated dose of 0.2 versus 1.3 mSv, respectively. Both protocols allowed the analysis of the studied parameters without loss of precision.
  
  
  CONCLUSIONS
  Reconstruction of the MPFL produced no improvement in patellar tilt or shift in the population studied. The low-radiation protocol was equally effective in measuring changes in patellar tracking and is recommended. Although the procedure successfully stabilized the patella, knee surgeons should not expect patellar shift and tilt correction when performing isolated patellofemoral ligament reconstruction in patients with recurrent patellar instability.
  
  
  METHODS
  IV.
authors.affiliation: Orthopaedic and Traumatology Institute of São Paulo University, Ovídio Pires de Campos St, 333, 3rd floor, Cerqueira Cesar, São Paulo, SP, 5403-010, Brazil. gobbiortopedia@gmail.com.
authors.forename: Riccardo G
authors.initials: RG
authors.lastname: Gobbi
authors.affiliation: Orthopaedic and Traumatology Institute of São Paulo University, Ovídio Pires de Campos St, 333, 3rd floor, Cerqueira Cesar, São Paulo, SP, 5403-010, Brazil.
authors.forename: Marco K
authors.initials: MK
authors.lastname: Demange
authors.affiliation: Orthopaedic and Traumatology Institute of São Paulo University, Ovídio Pires de Campos St, 333, 3rd floor, Cerqueira Cesar, São Paulo, SP, 5403-010, Brazil.
authors.forename: Luiz Francisco Rodrigues
authors.initials: LFR
authors.lastname: de Ávila
authors.affiliation: Orthopaedic and Traumatology Institute of São Paulo University, Ovídio Pires de Campos St, 333, 3rd floor, Cerqueira Cesar, São Paulo, SP, 5403-010, Brazil.
authors.forename: José de Arimatéia Batista
authors.initials: JAB
authors.lastname: Araújo Filho
authors.affiliation: Orthopaedic and Traumatology Institute of São Paulo University, Ovídio Pires de Campos St, 333, 3rd floor, Cerqueira Cesar, São Paulo, SP, 5403-010, Brazil.
authors.forename: Ramon Alfredo
authors.initials: RA
authors.lastname: Moreno
authors.affiliation: Orthopaedic and Traumatology Institute of São Paulo University, Ovídio Pires de Campos St, 333, 3rd floor, Cerqueira Cesar, São Paulo, SP, 5403-010, Brazil.
authors.forename: Marco Antônio
authors.initials: MA
authors.lastname: Gutierrez
authors.affiliation: Orthopaedic and Traumatology Institute of São Paulo University, Ovídio Pires de Campos St, 333, 3rd floor, Cerqueira Cesar, São Paulo, SP, 5403-010, Brazil.
authors.forename: Marina
authors.initials: M
authors.lastname: de Sá Rebelo
authors.affiliation: Orthopaedic and Traumatology Institute of São Paulo University, Ovídio Pires de Campos St, 333, 3rd floor, Cerqueira Cesar, São Paulo, SP, 5403-010, Brazil.
authors.forename: Luis Eduardo Passarelli
authors.initials: LEP
authors.lastname: Tírico
authors.affiliation: Orthopaedic and Traumatology Institute of São Paulo University, Ovídio Pires de Campos St, 333, 3rd floor, Cerqueira Cesar, São Paulo, SP, 5403-010, Brazil.
authors.forename: José Ricardo
authors.initials: JR
authors.lastname: Pécora
authors.affiliation: Orthopaedic and Traumatology Institute of São Paulo University, Ovídio Pires de Campos St, 333, 3rd floor, Cerqueira Cesar, São Paulo, SP, 5403-010, Brazil.
authors.forename: Gilberto Luis
authors.initials: GL
authors.lastname: Camanho
mesh_terms: D000293:Adolescent; D000328:Adult; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007593:Joint Instability / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000601:surgery*; D008023:Ligaments, Articular / Q000503:physiopathology / Q000601:surgery*; D008297:Male; D061330:Multidetector Computed Tomography; D019637:Orthopedic Procedures; D010329:Patella / Q000000981:diagnostic imaging* / Q000503:physiopathology* / Q000601:surgery; D031222:Patellar Dislocation / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000601:surgery*; D057071:Patellofemoral Joint / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000601:surgery*; D019651:Plastic Surgery Procedures; D012008:Recurrence; D016896:Treatment Outcome; D055815:Young Adult
keywords: Four-dimensional computed tomography; Joint instability; Ligaments/surgery; Multidetector computed tomography; Orthopaedics; Patellar dislocation; Radiology; Tomography; Tomography, X-ray computed