Tibial fixation of anterior cruciate ligament allograft tendons: comparison of 1-, 2-, and 4-stranded constructs.
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.
Park
Daniel K
DK
Department of Orthopedic Surgery, Rush University Medical Center, Chicago, Illinois, USA.
Fogel
Harold A
HA
Bhatia
Sanjeev
S
Bach
Bernard R
BR
Gupta
Aman
A
Shewman
Elizabeth F
EF
Wang
Vincent
V
Verma
Nikhil
N
Provencher
Matthew T
MT
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