title: Impact of Hamstring Graft Diameter on Tendon Strength: A Biomechanical Study.
abstract: OBJECTIVE
  The purpose of this study was to compare the tensile strength of hamstring grafts of varying combined pull-through diameters within the clinically relevant range of 6 to 9 mm.
  
  
  METHODS
  We tested 44 non-irradiated allograft hamstring grafts (11 per group). Combined looped semitendinosus and gracilis grafts were allocated to the 6-, 7-, 8-, or 9-mm group based on the smallest-diameter lumen that the graft could be "pulled through" using a surgical sizing instrument. Testing was performed on an Instron materials testing machine (Instron, Norwood, MA). Samples were secured with cryoclamps, prestressed, and pulled to failure at a rate of 10% gauge length per second.
  
  
  RESULTS
  The mean load to failure was 2,359 ± 474 N, 3,263 ± 677 N, 3,908 ± 556 N, and 4,360 ± 606 N for the 6-, 7-, 8-, and 9-mm grafts, respectively. Minimum failure loads were as low as 1,567 N, 2,288 N, 2,874 N, and 3,720 N for each group, respectively. There were statistically significant differences between the 6- and 7-mm, 6- and 8-mm, 6- and 9-mm, and 7- and 9-mm groups (P = .01).
  
  
  CONCLUSIONS
  Statistically different increasing tensile strength was seen as graft diameter increased. Significant variability exists in the strength of multi-stranded hamstring allografts within the diameter range of 6 to 9 mm that often falls well below the commonly accepted value of 4,000 N for a hamstring graft.
  
  
  CONCLUSIONS
  Recent evidence suggests a higher early failure rate of hamstring autografts in subsets of patients with graft diameters of 8 mm or less. This study may increase awareness that hamstring grafts may not be nearly as strong as previously appreciated and that increasing tendon diameters by 1 to 2 mm may dramatically affect graft strength. These data may be helpful in preoperative discussions regarding variable hamstring size, strength, and potential intraoperative augmentation options.
authors.affiliation: Eastern Virginia Medical School, Norfolk, Virginia, U.S.A.
authors.forename: Michael R
authors.initials: MR
authors.lastname: Boniello
authors.affiliation: Eastern Virginia Medical School, Norfolk, Virginia, U.S.A.
authors.forename: Paul M
authors.initials: PM
authors.lastname: Schwingler
authors.affiliation: Jordan-Young Institute for Orthopedic Surgery & Sports Medicine, Virginia Beach, Virginia, U.S.A.
authors.forename: Justin M
authors.initials: JM
authors.lastname: Bonner
authors.affiliation: Jordan-Young Institute for Orthopedic Surgery & Sports Medicine, Virginia Beach, Virginia, U.S.A.
authors.forename: Samuel P
authors.initials: SP
authors.lastname: Robinson
authors.affiliation: LifeNet Health, Virginia Beach, Virginia, U.S.A.
authors.forename: Andrew
authors.initials: A
authors.lastname: Cotter
authors.affiliation: Jordan-Young Institute for Orthopedic Surgery & Sports Medicine, Virginia Beach, Virginia, U.S.A.. Electronic address: kfbonner@cox.net.
authors.forename: Kevin F
authors.initials: KF
authors.lastname: Bonner
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D016118:Anterior Cruciate Ligament / Q000601:surgery*; D059549:Anterior Cruciate Ligament Reconstruction / Q000379:methods*; D005260:Female; D006085:Graft Survival; D006801:Humans; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000637:transplantation; D013710:Tendons / Q000033:anatomy & histology / Q000502:physiology / Q000637:transplantation*; D013718:Tensile Strength; D016474:Weight-Bearing; D055815:Young Adult