title: Biomechanical consequences of a nonanatomic posterior medial meniscal root repair.
abstract: BACKGROUND
  Posterior medial meniscal root tears have been reported to extrude with the meniscus becoming adhered posteromedially along the posterior capsule. While anatomic repair has been reported to restore tibiofemoral contact mechanics, it is unknown whether nonanatomic positioning of a meniscal root repair to a posteromedial location would restore the loading profile of the knee joint.
  
  
  OBJECTIVE
  The purpose of this study was to compare the tibiofemoral contact mechanics of a nonanatomic posterior medial meniscal tear with that of the intact knee or anatomic repair. It was hypothesized that a nonanatomic root repair would not restore the tibiofemoral contact pressures and areas to that of the intact or anatomic repair state.
  
  
  METHODS
  Controlled laboratory study.
  
  
  METHODS
  Tibiofemoral contact mechanics were recorded in 6 male human cadaveric knee specimens (average age, 45.8 years) using pressure sensors. Each knee underwent 5 testing conditions for the posterior medial meniscal root: (1) intact knee; (2) root tear; (3) anatomic transtibial pull-out repair; (4) nonanatomic transtibial pull-out repair, placed 5 mm posteromedially along the edge of the articular cartilage; and (5) root tear concomitant with an ACL tear. Knees were loaded with a 1000-N axial compressive force at 4 flexion angles (0°, 30°, 60°, 90°), and contact area, mean contact pressure, and peak contact pressure were calculated.
  
  
  RESULTS
  Contact area was significantly lower after nonanatomic repair than for the intact knee at all flexion angles (mean = 44% reduction) and significantly higher for anatomic versus nonanatomic repair at all flexion angles (mean = 27% increase). At 0° and 90°, and when averaged across flexion angles, the nonanatomic repair significantly increased mean contact pressures in comparison to the intact knee or anatomic repair. When averaged across flexion angles, the peak contact pressures after nonanatomic repair were significantly higher than the intact knee but not the anatomic repair. In contrast, when averaged across all flexion angles, the anatomic repair resulted in a 17% reduction in contact area and corresponding increases in mean and peak contact pressures of 13% and 26%, respectively, compared with the intact knee.
  
  
  CONCLUSIONS
  For most testing conditions, the nonanatomic repair did not restore the contact area or mean contact pressures to that of the intact knee or anatomic repair. However, the anatomic repair produced near-intact contact area and resulted in relatively minimal increases in mean and peak contact pressures compared with the intact knee.
  
  
  CONCLUSIONS
  Results emphasize the importance of ensuring an anatomic posterior medial meniscal root repair by releasing the extruded menisci from adhesions and the posteromedial capsule. Similar caution toward preventing displacement of the meniscal root repair construct should be emphasized.
authors.affiliation: Steadman Philippon Research Institute, Vail, Colorado, USA.
authors.forename: Christopher M
authors.initials: CM
authors.lastname: LaPrade
authors.affiliation: Quality Care Clinic and Surgicenter, Clinton, Iowa, USA.
authors.forename: Abdullah
authors.initials: A
authors.lastname: Foad
authors.affiliation: Steadman Philippon Research Institute, Vail, Colorado, USA.
authors.forename: Sean D
authors.initials: SD
authors.lastname: Smith
authors.affiliation: Steadman Philippon Research Institute, Vail, Colorado, USA.
authors.forename: Travis Lee
authors.initials: TL
authors.lastname: Turnbull
authors.affiliation: Steadman Philippon Research Institute, Vail, Colorado, USA.
authors.forename: Grant J
authors.initials: GJ
authors.lastname: Dornan
authors.affiliation: Oslo Sports Trauma Research Center, Norwegian School of Sport Sciences, Oslo, Norway Oslo University Hospital, University of Oslo, Oslo, Norway.
authors.forename: Lars
authors.initials: L
authors.lastname: Engebretsen
authors.affiliation: Steadman Philippon Research Institute, Vail, Colorado, USA.
authors.forename: Coen A
authors.initials: CA
authors.lastname: Wijdicks
authors.affiliation: Steadman Philippon Research Institute, Vail, Colorado, USA The Steadman Clinic, Vail, Colorado, USA drlaprade@sprivail.org.
authors.forename: Robert F
authors.initials: RF
authors.lastname: LaPrade
mesh_terms: D000328:Adult; D001696:Biomechanical Phenomena; D002102:Cadaver; D002357:Cartilage Diseases / Q000601:surgery; D002358:Cartilage, Articular / Q000601:surgery*; D006801:Humans; D007718:Knee Injuries / Q000601:surgery*; D007719:Knee Joint / Q000601:surgery*; D008297:Male; D008592:Menisci, Tibial / Q000601:surgery*; D008875:Middle Aged; D016059:Range of Motion, Articular; D000070600:Tibial Meniscus Injuries
keywords: anatomic; meniscal root repair; meniscal tear; root tear