title: Biomechanical evaluation of a transtibial pull-out meniscal root repair: challenging the bungee effect.
abstract: BACKGROUND
  A common treatment for posterior meniscal root tears is transtibial pull-out repair, which has been biomechanically reported to restore tibiofemoral contact mechanics to those of the intact knee. Biomechanical data suggest that there is significant displacement of the repaired meniscal root with cyclic loading, which may be responsible for the poor healing and meniscal extrusion demonstrated in some clinical studies.
  
  
  OBJECTIVE
  The purpose of this study was to quantify the time-zero displacement of the posterior meniscal root in response to cyclic loading after transtibial pull-out repair and to quantify the individual contributions to displacement of the following: (1) suture elongation, (2) button-bone interface, and (3) meniscus-suture interface. The meniscus-suture interface was hypothesized to result in significantly more displacement than the button-bone interface or suture elongation.
  
  
  METHODS
  Descriptive laboratory study.
  
  
  METHODS
  Transtibial pull-out repair of the posterior medial meniscal root was performed in 6 porcine knees, and cyclic displacement was measured using a loading protocol representative of postoperative rehabilitation. Displacement from (1) suture elongation, (2) the button-bone interface, and (3) the meniscus-suture interface was determined by cyclically loading 6 specimens for each construct using the same loading protocol to determine the contribution of each component to the overall displacement of the repair construct.
  
  
  RESULTS
  After 1000 cycles, the repair construct displaced by a mean of 3.28 mm (95% CI, 2.07-4.49). The meniscus-suture component (mean, 2.52 mm; 95% CI, 2.21-2.83) displaced significantly more than the button-bone component (mean, 0.90 mm; 95% CI, 0.64-1.15; P = .006) and suture elongation component (mean, 0.71 mm; 95% CI, 0.36-1.06; P = .006) after 1000 cycles. Displacement of the button-bone and suture elongation components was not significantly different after 1000 cycles (P = .720).
  
  
  CONCLUSIONS
  There was substantial displacement of the posterior medial meniscal root repaired with the transtibial pull-out technique under a cyclic loading protocol simulating postoperative rehabilitation. The meniscus-suture interface contributed to significantly more displacement than the button-bone interface and suture elongation in the transtibial pull-out repair construct.
  
  
  CONCLUSIONS
  The results provide a framework for optimizing the transtibial pull-out repair technique. Future studies should focus on improving suture fixation strength within the meniscus-suture interface.
authors.affiliation: Steadman Philippon Research Institute, Vail, Colorado, USA The Steadman Clinic, Vail, Colorado, USA.
authors.forename: Anthony J
authors.initials: AJ
authors.lastname: Cerminara
authors.affiliation: Steadman Philippon Research Institute, Vail, Colorado, USA.
authors.forename: Christopher M
authors.initials: CM
authors.lastname: LaPrade
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 The Steadman Clinic, Vail, Colorado, USA.
authors.forename: Michael B
authors.initials: MB
authors.lastname: Ellman
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: D000818:Animals; D008592:Menisci, Tibial / Q000601:surgery*; D023421:Models, Animal; D009984:Orthopedic Fixation Devices; D019637:Orthopedic Procedures / Q000379:methods*; D013536:Suture Techniques; D013552:Swine; D013718:Tensile Strength / Q000502:physiology*; D016474:Weight-Bearing / Q000502:physiology*
keywords: medial meniscus; meniscal repair; meniscal root tear; transtibial pull-out repair