title: Medial Meniscal Root Avulsion: A Biomechanical Comparison of 4 Different Repair Constructs.
abstract: OBJECTIVE
  To evaluate the time-zero load-to-failure strength of 4 different constructs used to repair medial meniscal root avulsions.
  
  
  METHODS
  Sixty fresh-frozen cadaveric knees with a mean age of 74 years were used for this study. Each knee was dissected to isolate the attachment of the posterior root of the medial meniscus to the tibial plateau. An Instron machine (Instron, Norwood, MA) with a custom-designed clamp was used to avulse the intact posterior meniscal root in 12 control specimens. An additional 48 specimens were tested after transection of the native meniscal root to evaluate the pullout strength of 4 different repair constructs using No. 0 FiberWire suture (Arthrex, Naples, FL): a single suture (n = 12), a double suture (n = 12), a loop stitch (n = 12), and a locking loop stitch (n = 12). Analysis of variance was used to compare load to failure and stiffness of all 4 groups; pair-wise, between-group differences were also assessed.
  
  
  RESULTS
  Repair failure occurred most commonly by suture pullout in 94% of the specimens in the repair groups. For the controls, failure occurred most commonly at the meniscus-clamp interface. Failure load was highest for the control group (mean, 359.5 ± 168 N), followed in descending order by the locking loop stitch (191.4 ± 45.1 N), loop stitch (119.6 ± 55.0 N), double suture (96.2 ± 51.4 N), and single suture (58.2 ± 29.6 N). The control group was significantly stronger than 3 of the experimental groups (single suture [95% CI, 3.8 to 11.3], double suture [95% CI, 2.1 to 6.4], and loop stitch [95% CI, 2.0 to 4.5]; P < .0001) but not the locking loop stitch (P = .003; 95% CI, 1.2 to 3.2). The locking loop stitch was significantly stronger than the single suture (P < .0001; 95% CI, 2.0 to 5.4) and double suture (P = .003; 95% CI, 1.2 to 2.9). The locking loop stitch was significantly stiffer than the single suture (P < .0001; 95% CI, 3.8 to 20.3), double suture (P < .0001; 95% CI, 2.0 to 9.8), and loop stitch (P = .03; 95% CI, 1.1 to 5.5) but not significantly different from the control group (P = .93; 95% CI, 0.3 to 1.9). Age and gender had no effect on pullout strength.
  
  
  CONCLUSIONS
  The results of this study show that the locking loop stitch provided time-zero load-to-failure strength that most closely approximated the strength of the native meniscal root in addition to being significantly stronger and stiffer than 3 other commonly used repair methods. The true strength of the native meniscal root is unknown based on limitations with our testing methodology.
  
  
  CONCLUSIONS
  The locking loop stitch exhibited the highest load to failure and stiffness of the 4 fixation methods tested, despite the fact that none of the fixation methods replicated the strength of the intact meniscal root. It is currently unknown what strength of fixation is required for healing of meniscal root repairs.
authors.affiliation: Department of Orthopedic Surgery, Washington University, St. Louis, Missouri, U.S.A.
authors.forename: Richard
authors.initials: R
authors.lastname: Mitchell
authors.affiliation: Department of Orthopedic Surgery, Washington University, St. Louis, Missouri, U.S.A.
authors.forename: Ryan
authors.initials: R
authors.lastname: Pitts
authors.affiliation: Department of Orthopedic Surgery, Chungnam National University School of Medicine, Daejeon, Republic of Korea.
authors.forename: Young-Mo
authors.initials: YM
authors.lastname: Kim
authors.affiliation: Department of Orthopedic Surgery, Washington University, St. Louis, Missouri, U.S.A.. Electronic address: matavam@wudosis.wustl.edu.
authors.forename: Matthew J
authors.initials: MJ
authors.lastname: Matava
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001696:Biomechanical Phenomena; D002102:Cadaver; D005260:Female; D006801:Humans; D008297:Male; D008592:Menisci, Tibial / Q000503:physiopathology / Q000601:surgery*; D008875:Middle Aged; D008953:Models, Anatomic; D013536:Suture Techniques; D013537:Sutures; D000070600:Tibial Meniscus Injuries; D016474:Weight-Bearing; D014945:Wound Healing