title: Electromechanical delay of the knee flexor muscles is impaired after harvesting hamstring tendons for anterior cruciate ligament reconstruction.
abstract: BACKGROUND
  Changes in electromechanical delay during muscle activation are expected when there are substantial alterations in the structural properties of the musculotendinous tissue. In anterior cruciate ligament reconstruction, specific tendons are being harvested for grafts. Thus, there is an associated scar tissue development at the tendon that may affect the corresponding electromechanical delay.
  
  
  OBJECTIVE
  This study was conducted to investigate whether harvesting of semitendinosus and gracilis tendons for anterior cruciate ligament reconstruction will affect the electromechanical delay of the knee flexors.
  
  
  METHODS
  Case-control study; Level of evidence, 3.
  
  
  METHODS
  The authors evaluated 12 patients with anterior cruciate ligament reconstruction with a semitendinosus and gracilis autograft, 2 years after the reconstruction, and 12 healthy controls. Each participant performed 4 maximally explosive isometric contractions with a 1-minute break between contractions. The surface electromyographic activity of the biceps femoris and the semitendinosus was recorded from both legs during the contractions.
  
  
  RESULTS
  The statistical comparisons revealed significant increases of the electromechanical delay of the anterior cruciate ligament-reconstructed knee for both investigated muscles. Specifically, the electromechanical delay values were increased for both the biceps femoris (P = .029) and the semitendinosus (P = .005) of the reconstructed knee when compared with the intact knee. Comparing the anterior cruciate ligament-reconstructed knee against healthy controls revealed similar significant differences for both muscles (semitendinosus, P = .011; biceps femoris, P = .024).
  
  
  CONCLUSIONS
  The results showed that harvesting the semitendinosus and gracilis tendons for anterior cruciate ligament reconstruction significantly increased the electromechanical delay of the knee flexors. Increased hamstring electromechanical delay might impair knee safety and performance by modifying the transfer time of muscle tension to the tibia and therefore affecting muscle response during sudden movements in athletic activities. However, further investigation is required to identify whether the increased electromechanical delay of the hamstrings can actually influence optimal sports performance and increase the risk for knee injury in athletes with anterior cruciate ligament reconstructions.
authors.affiliation: Orthopaedic Sports Medicine Center of Ioannina, Department of Orthopaedic Surgery, University of Ioannina, Ioannina, Greece.
authors.forename: Stavros
authors.initials: S
authors.lastname: Ristanis
authors.forename: Elias
authors.initials: E
authors.lastname: Tsepis
authors.forename: Dimitrios
authors.initials: D
authors.lastname: Giotis
authors.forename: Nicholas
authors.initials: N
authors.lastname: Stergiou
authors.forename: Guiliano
authors.initials: G
authors.lastname: Cerulli
authors.forename: Anastasios D
authors.initials: AD
authors.lastname: Georgoulis
mesh_terms: D000293:Adolescent; D000328:Adult; D016118:Anterior Cruciate Ligament / Q000601:surgery*; D001178:Arthroplasty / Q000009:adverse effects*; D016022:Case-Control Studies; D004576:Electromyography; D006801:Humans; D007537:Isometric Contraction; D007719:Knee Joint / Q000502:physiology / Q000601:surgery*; D008297:Male; D018482:Muscle, Skeletal / Q000502:physiology*; D013710:Tendons / Q000637:transplantation*; D055815:Young Adult