It has recently been shown that graft fixation close to the ACL insert
ion site is optimal in order to increase anterior knee stability. Hams
tring tendon fixation using interference screws offers this possibilit
y and a round threaded titanium interference screw has been previously
developed. The use of a round threaded biodegradable interference scr
ew may be equivalent. In addition, to increase initial fixation streng
th, graft harvest with a distally attached bone plug may be advantageo
us, but biomechanical data do not exist. This study compares the initi
al pullout force, stiffness of fixation, and failure modes of three st
rand semitendinosus grafts in 36 proximal calf tibiae using either bio
degradable poly-(D,L-lactide) (Sysorb; Sulzer Orthopaedics Ltd, Munsin
gen, Switzerland) or round threaded titanium (RCI; Smith & Nephew DonJ
oy, Carlsbad, CA) interference screws, harvested either without (biode
gradable: group I, titanium III) or with (biodegradable: group II, tit
anium: group IV) attached tibial bone plugs. Maximum pullout force in
group I (507 +/- 93 N) was significantly higher than in group III (419
+/- 77 N). Pullout force of bone plug fixation was significantly high
er than that of direct tendon fixation (717 +/- 90 N in group II and 6
02 +/- 117 N in group TV). Pullout force of biodegradable fixation was
significantly higher in both settings. These results indicate that in
itial pullout force of hamstring-tendon graft interference screw fixat
ion can be increased by using a biodegradable interference screw. In a
ddition, initial pullout force of hamstring-tendon graft fixation with
an interference screw can be greatly increased by harvesting the graf
t with its distally attached tibial bone plug.