title: Tibial fixation of anterior cruciate ligament allograft tendons: comparison of 1-, 2-, and 4-stranded constructs.
abstract: BACKGROUND
  In sum, 1-, 2-, and 4-stranded allografts are used for soft tissue anterior cruciate ligament reconstruction; however, the fixation properties of fixation devices are not well assessed.
  
  
  OBJECTIVE
  There are no differences in the biomechanical characteristics of 1 (Achilles)-, 2 (posterior tibialis)-, and 4 (semitendinosus)-stranded allograft tibial fixation.
  
  
  METHODS
  Controlled laboratory study.
  
  
  METHODS
  Sixty-three fresh-frozen porcine tibiae were used to evaluate the fixation of 1-, 2-, and 4-stranded human tendon allografts (Achilles, posterior tibialis, and semitendinosus) with 3 fixation devices (Delta, Intrafix, and Calaxo screws). With use of a materials testing system, each graft was subjected to 500 cycles of loading (50-250 N, 0.75 mm/sec) to determine displacement and cyclic stiffness, followed by a monotonic failure test (20 mm/min) to determine maximum load and pullout stiffness.
  
  
  RESULTS
  For each graft type, there were no significant biomechanical differences between fixation devices. However, the 1-stranded graft (Achilles) construct demonstrated significantly higher mean displacement (3.17 +/- 1.62 mm), lower cyclical stiffness (156 +/- 25 N/mm), lower load to failure (479 +/- 87 N), and lower pullout stiffness (140 +/- 28 N/mm). In comparison with the 2-stranded graft (posterior tibialis), the 4-stranded graft (semitendinosus) exhibited lower displacement (0.86 +/- 0.44 to 1.12 +/- 0.51 mm) and higher ultimate failure load (832 +/- 255 to 656 +/- 168 N). Numerous differences in fixation properties were noted when comparing a device to each of the 3 grafts.
  
  
  CONCLUSIONS
  The 1-stranded allograft demonstrated inferior biomechanical tibial fixation properties when compared with 2 (posterior tibialis)- and 4 (semitendinosus)-stranded allograft constructs for all fixation devices tested.
  
  
  CONCLUSIONS
  This study demonstrated that not all tibial fixation devices are designed to adequately accommodate different types of anterior cruciate ligament allografts. Biomechanical evidence suggests that caution is warranted when using an Achilles allograft fixated solely with an interference device.
authors.affiliation: Department of Orthopedic Surgery, Rush University Medical Center, Chicago, Illinois, USA.
authors.forename: Daniel K
authors.initials: DK
authors.lastname: Park
authors.forename: Harold A
authors.initials: HA
authors.lastname: Fogel
authors.forename: Sanjeev
authors.initials: S
authors.lastname: Bhatia
authors.forename: Bernard R
authors.initials: BR
authors.lastname: Bach
authors.forename: Aman
authors.initials: A
authors.lastname: Gupta
authors.forename: Elizabeth F
authors.initials: EF
authors.lastname: Shewman
authors.forename: Vincent
authors.initials: V
authors.lastname: Wang
authors.forename: Nikhil
authors.initials: N
authors.lastname: Verma
authors.forename: Matthew T
authors.initials: MT
authors.lastname: Provencher
mesh_terms: D000818:Animals; D016118:Anterior Cruciate Ligament / Q000601:surgery / Q000637:transplantation*; D001696:Biomechanical Phenomena; D001863:Bone Screws; D002102:Cadaver; D019637:Orthopedic Procedures; D013552:Swine; D013977:Tibia / Q000601:surgery*; D014184:Transplantation, Homologous