title: Pre-operative muscle activation patterns during walking are associated with TKA tibial implant migration.
abstract: BACKGROUND
  Gait biomechanical variables have been associated with total knee arthroplasty tibial implant migration measured with Radiostereometric Analysis (RSA), but no studies have examined the role of the periarticular musculature, which is responsible for a high proportion of the forces on the joint. The purpose of this study was to measure the pre-operative electromyography (EMG) patterns of the periarticular knee muscles during gait and determine the association of these patterns with the post-operative tibial implant migration measured with RSA. We hypothesized that pre-operative muscle activation patterns (specifically the activation patterns of the vastus and gastrocnemius muscle groups) measured with EMG are associated with migration at 6months.
  
  
  METHODS
  Electromyographic data were collected from 6 periarticular knee joint muscles on 37 patients pre-operatively during gait. Radiostereometric exams were performed immediately and at 6 months post-operatively. Relationships between the pre-operative patterns of muscle activation and micromotion of the implant were examined using Pearson correlation and regression models.
  
  
  RESULTS
  Statistically significant correlations were found between the pattern of the quadriceps and gastrocnemius muscle activations during gait and implant translation in the posterior direction. Regression analysis illustrated that a substantial proportion of the variance in the post-operative tibial component posterior translation (R2=0.49) was explained by a prolonged activation of the vastus medialis muscle and higher activation of the lateral gastrocnemius muscle during early stance.
  
  
  CONCLUSIONS
  The variability in migration explained by the muscle activation patterns supports the hypothesis that pre-operative functional characteristics can contribute to predicting implant migration following total knee arthroplasty surgery.
authors.affiliation: Department of Surgery, Division of Orthopedics, Dalhousie University, Halifax, Canada. wilsondaj@gmail.com
authors.forename: David A J
authors.initials: DA
authors.lastname: Wilson
authors.forename: Cheryl L
authors.initials: CL
authors.lastname: Hubley-Kozey
authors.forename: Janie L
authors.initials: JL
authors.lastname: Astephen Wilson
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Dunbar
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D005548:Foreign-Body Migration / Q000209:etiology* / Q000503:physiopathology*; D006801:Humans; D007719:Knee Joint / Q000503:physiopathology* / Q000601:surgery*; D007720:Knee Prosthesis / Q000009:adverse effects*; D008297:Male; D008875:Middle Aged; D009119:Muscle Contraction; D018482:Muscle, Skeletal / Q000503:physiopathology; D011300:Preoperative Care; D011379:Prognosis; D013977:Tibia / Q000503:physiopathology / Q000601:surgery; D016896:Treatment Outcome; D016138:Walking