title: Influence of rupture patterns of the medial patellofemoral ligament (MPFL) on the outcome after operative treatment of traumatic patellar dislocation.
abstract: OBJECTIVE
  Patellar dislocation usually occurs to the lateral side, leading to ruptures of the medial patellofemoral ligament (MPFL) in about 90 % of all cases. Reliable prognostic factors for the stability of the patellofemoral joint after MPFL surgery and satisfaction of the patient have not been established as yet.
  
  
  METHODS
  This multicentric study retrospectively included 40 patients with a mean age of 22.4 ± 8.1 years (range 9-48) from 5 German Trauma Departments with first-time traumatic patellar dislocation and operative treatment. Surgery was limited to soft tissue repairs, and a preoperative magnetic resonance imaging (MRI) was performed in all cases. Evaluation of the MRI included sulcus angle, dysplasia of the trochlea, depth and facet asymmetry of the trochlea, Insall-Salvati index, Tibial tuberosity to trochlear groove (TTTG) distance, and rupture patterns of the MPFL. Patients were interrogated after 2 years about recurrent dislocation, satisfaction, and the Kujala score.
  
  
  RESULTS
  Trochlea facet asymmetry was significantly lower in patients with redislocation (23.5 ± 18.8) than in patients without redislocation (43.1 ± 16.5, p = 0.03). Patients with a patellar-based rupture were significantly younger (19.5 ± 7.2 years) than patients without patellar-based rupture (25.4 ± 8.1 years, p < 0.02). Patients with femoral-based ruptures were significantly older (25.7 ± 9.2 years) than patients without femoral-based rupture (19.7 ± 6.1 years, p < 0.02), and had a significantly higher TTTG distance (10.2 ± 6.9 vs. 4.5 ± 5.5, p < 0.02). Patients with incomplete ruptures of the MPFL had a significantly lower Insall-Salvati index (1.2 ± 0.2 vs. 1.4 ± 0.2, p = 0.05). The Kujala score in patients with redislocations was significantly lower (81.0 ± 10.5 points) than in patients without redislocation (91.9 ± 9.2 points, p < 0.02).
  
  
  CONCLUSIONS
  Younger patients more often sustain patellar-based ruptures following first-time traumatic patella dislocation, while older patients more often sustain femoral-based ruptures of the MPFL. Incomplete MPFL ruptures are correlated with lower Insall-Salvati indices. Low trochlear facet asymmetry is correlated with higher rates of redislocation. These results may be of relevance for the operative and postoperative treatment in the future.
  
  
  METHODS
  Prognostic study, Level IV.
authors.affiliation: Trauma Department, Hannover Medical School (MHH), Carl-Neuberg-Straße 1, 30625, Hannover, Germany. petri.maximilian@mh-hannover.de
authors.forename: M
authors.initials: M
authors.lastname: Petri
authors.forename: C
authors.initials: C
authors.lastname: von Falck
authors.forename: M
authors.initials: M
authors.lastname: Broese
authors.forename: E
authors.initials: E
authors.lastname: Liodakis
authors.forename: P
authors.initials: P
authors.lastname: Balcarek
authors.forename: P
authors.initials: P
authors.lastname: Niemeyer
authors.forename: M
authors.initials: M
authors.lastname: Hofmeister
authors.forename: C
authors.initials: C
authors.lastname: Krettek
authors.forename: C
authors.initials: C
authors.lastname: Voigt
authors.forename: C
authors.initials: C
authors.lastname: Haasper
authors.forename: J
authors.initials: J
authors.lastname: Zeichen
authors.forename: K H
authors.initials: KH
authors.lastname: Frosch
authors.forename: H
authors.initials: H
authors.lastname: Lill
authors.forename: M
authors.initials: M
authors.lastname: Jagodzinski
mesh_terms: D000293:Adolescent; D000328:Adult; D002648:Child; D005260:Female; D006801:Humans; D007593:Joint Instability / Q000209:etiology* / Q000503:physiopathology; D008023:Ligaments, Articular / Q000293:injuries* / Q000503:physiopathology / Q000601:surgery; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D031222:Patellar Dislocation / Q000150:complications / Q000175:diagnosis / Q000503:physiopathology / Q000601:surgery*; D057071:Patellofemoral Joint; D012189:Retrospective Studies; D012421:Rupture; D055815:Young Adult