title: Clinical and electromyographic results of proximal and distal realignment procedures in young patients with recurrent patellar dislocations.
abstract: BACKGROUND
  Until now, no study has been published about the electromyographic changes in the extensor apparatus after the Green procedure for proximal realignment in young patients with recurrent patellar dislocations. This electromyographic study was performed to analyze imbalances between the vastus medialis and vastus lateralis muscles after different patellar realignment procedures.
  
  
  OBJECTIVE
  Surgical proximal realignment leads to electromyographic changes in the extensor apparatus of the knee and to imbalances between the vastus medialis and vastus lateralis muscles.
  
  
  METHODS
  Cohort study; Level of evidence, 3.
  
  
  METHODS
  A total of 28 knees of 25 patients, with a mean age of 15 years, were treated operatively for recurrent patellar dislocations. The mean follow-up was 6.3 years. Depending on the type of surgical intervention, the patients were assigned to 3 different groups: the patients of group 1 underwent only the Green vastus medialis obliquus (VMO) advancement, group 2 was treated with a combination of the Green proximal and the Roux-Goldthwait distal realignment, and group 3 was treated with a combination of the Green proximal realignment and an additional tubercle transfer. All patients underwent clinical, radiological, and electromyographic examinations. The muscle activities of a healthy control group without patellar dislocations were used for comparison.
  
  
  RESULTS
  A combination of the Green procedure and tubercle transfer led to significantly better clinical results and a lower number of redislocations (P < .05) compared with patients who underwent only the Green proximal realignment. While ascending or descending stairs, the ratio between the electromyographic activities of the vastus medialis and vastus lateralis muscles in groups 1 and 2 was significantly smaller compared with the control group (P < .02). Only the electromyograms of group 3 revealed a balanced extensor apparatus during loading with comparable activities of the vastus medialis and vastus lateralis muscles and no significant difference to the control group (P = .37).
  
  
  CONCLUSIONS
  Our electromyographic investigations showed the importance of the vastus medialis in the pathogenesis of malalignment of the extensor mechanism. The Green VMO advancement without tibial tubercle transfer is not able to balance the activities of the vastus medialis and vastus lateralis muscles and cannot be recommended for further use.
authors.affiliation: Department of Orthopaedic Surgery, University Medical Center Rostock, Doberanerstrasse 142, 18057 Rostock, Germany. peter.kreuz@uni-rostock.de
authors.forename: Peter C
authors.initials: PC
authors.lastname: Kreuz
authors.forename: Lars
authors.initials: L
authors.lastname: Peterson
authors.forename: Natascha
authors.initials: N
authors.lastname: van der Werf-Grohmann
authors.forename: Michael
authors.initials: M
authors.lastname: Vohrer
authors.forename: Ludwig
authors.initials: L
authors.lastname: Schwering
mesh_terms: D000293:Adolescent; D000328:Adult; D002648:Child; D002675:Child, Preschool; D015331:Cohort Studies; D004576:Electromyography; D005260:Female; D006801:Humans; D008297:Male; D031222:Patellar Dislocation / Q000209:etiology / Q000601:surgery*; D052097:Quadriceps Muscle / Q000502:physiology; D012008:Recurrence; D055815:Young Adult
keywords: control group; distal realignment; electromyogram; patellar dislocation; proximal realignment