INTRAOPERATIVE FORCE-SETTING DID NOT IMPROVE THE MECHANICAL-PROPERTIES OF AN AUGMENTED BONE-TENDON-BONE ANTERIOR CRUCIATE LIGAMENT GRAFT INA GOAT MODEL
Jj. Smith et al., INTRAOPERATIVE FORCE-SETTING DID NOT IMPROVE THE MECHANICAL-PROPERTIES OF AN AUGMENTED BONE-TENDON-BONE ANTERIOR CRUCIATE LIGAMENT GRAFT INA GOAT MODEL, Journal of orthopaedic research, 14(2), 1996, pp. 209-215
It has been hypothesized that load affects the mechanical properties o
f an anterior cruciate ligament graft while it remodels. The goal of t
his study was to use an existing goat model to evaluate the effect of
intraoperative set force on the postoperative mechanical properties of
an autograft that had been augmented with a synthetic segment. The fo
llowing questions were addressed. Do augmented autografts set with a h
igh force intraoperatively have improved structural and material graft
properties and lower anterior-posterior knee laxity at 3 months after
surgery, compared with autografts set with a low intraoperative force
? How do the structural and material properties of these implanted aut
ografts compare with the mechanical properties of an intact anterior c
ruciate ligament or an unimplanted control autograft? The anterior cru
ciate ligament was reconstructed in seven goats with use of a composit
e graft consisting of a bone-patellar tendon-bone autograft and a synt
hetic augmentation device. A force-setting technique was used intraope
ratively to establish the load-sharing between the autograft and augme
ntation segments such that the autograft carried either a high (16.5 N
in four animals) or low (1.5 N in three animals) level of force, whil
e the total force in the composite graft remained constant. Tensile te
sting was performed at 3 months after surgery to determine the materia
l and structural properties of the autograft, the intact anterior cruc
iate ligament from the normal contralateral knee, and a control bone-p
atellar tendon-bone graft of similar size that was harvested from the
contralateral knee at the time of necropsy and had never been implante
d in the joint. The structural and material properties of the autograf
ts initially set to high or low loads at surgery were not significantl
y different after 3 months of implantation. The strength and stiffness
of the implanted tendons were an average of 24 and 20% of the strengt
h and stiffness of the normal anterior cruciate ligament and 31 and 62
% of the control tendons, respectively. Intraoperative set force in an
augmented anterior cruciate ligament graft at the levels chosen in th
is study did not significantly affect weakening of the autograft at 3
months.