Comparison of pullout strength for seven- and nine-millimeter diameter interference screw size as used in anterior cruciate ligament reconstruction.
This study compares biomechanical properties of 7- and 9-mm diameter screws providing interference fixation in anterior cruciate ligament reconstruction. Sixteen pairs of fresh-frozen bovine knees were evaluated. Uniaxial load to failure was performed at a deformation rate of 30 mm/s along the mechanical axis of the ligament graft with the knees secured at 45 degrees of flexion in a custom jig. A video analyzer was used to measure ligament strain and bone-to-bone deformation. Ultimate force, deformation, and failure mode were recorded and compared. The 7-mm screws provided 98% yield strength, and 95% ultimate force compared with the 9-mm screws. The average femoral pullout strength was 1161 +/- 93 N in the 7-mm group and 1198 +/- 142 N in the 9-mm group. Failure mode was similar in both groups. Clinically, the usage of 7-mm screws may reduce iatrogenic injuries to the patellar tendon graft compared with larger screws. This study shows that the biomechanical advantages of 9-mm screws compared with 7-mm screws are minimal.
Sports Medicine Center of Metro Detroit, Michigan, USA.
J D
JD
Shapiro
D W
DW
Jackson
H M
HM
Aberman
T Q
TQ
Lee
T M
TM
Simon
D000818:Animals; D016118:Anterior Cruciate Ligament / Q000601:surgery*; D001178:Arthroplasty / Q000295:instrumentation*; D001696:Biomechanical Phenomena; D001863:Bone Screws; D002417:Cattle; D066298:In Vitro Techniques; D007719:Knee Joint / Q000503:physiopathology; D013710:Tendons / Q000637:transplantation