Dg. Nagarkatti et al., Mechanical evaluation of a soft tissue interference screw in free tendon anterior cruciate ligament graft fixation, AM J SP MED, 29(1), 2001, pp. 67-71
In this study of bioabsorbable screw fixation of free tendon grafts used in
anterior cruciate ligament reconstruction, we performed load-to-failure an
d cyclic loading of tendon fixation in porcine bone. Bone density measureme
nts from dual photon absorptometry scans were obtained to correlate bone de
nsity with fixation failure. The average density of porcine bone (1.42 g/cm
(2)) was similar to that of young human bone (1.30 g/cm(2)) and significant
ly higher than that of elderly human cadaveric bone specimens (0.30 g/cm(2)
). Cyclic loading was performed on free tendon grafts fixed with a bioabsor
bable screw alone and on grafts fixed with a bioabsorbable screw and an anc
hor (polylactic acid ball or cortical bone disk). Stiffness of fixation inc
reased substantially with the addition of a cortical bone disk anchor or po
lylactic acid ball compared with the interference screw alone. Tensile fixa
tion strength of central quadriceps free tendon and hamstring tendon grafts
were significantly superior in porcine bone of density similar to young hu
man bone than in elderly human cadaveric bone. The bioabsorbable interferen
ce screw yielded loads at failure comparable with traditional bone-tendon-b
one and hamstring tendon fixation when controlled for bone density. The add
ition of a cortical bone disk anchor provided the mast optimal fixation of
free tendon with the bioabsorbable screw and reduced slippage with cyclic l
oading to a very low level.