Background: Loss of knee extension has been reported by many authors
to be the most common complication following anterior cruciate ligament
reconstruction. The objective of this in vitro study was to determine the
effect, on loss of knee extension, of the knee flexion angle and the tension
of the bone-patellar tendon-bone graft during graft fixation in a
reconstruction of an anterior cruciate ligament.
Methods: The anterior cruciate ligament was reconstructed with use
of tibial and femoral bone tunnels placed in the footprint of the native
anterior cruciate ligament in ten cadavers. The graft was secured with an
initial tension of either 44 N (10 lb) or 89 N (20 lb) applied with the knee
at 0° or 30° of flexion. The knee flexion angle was measured with use
of digital images following graft fixation.
Results: Tensioning of the graft at 30° of knee flexion was
associated with loss of knee extension in this cadaver model. Graft tension
did not affect knee extension under the conditions tested.
Conclusions: The results suggest that one of the common causes of
the loss of full knee extension may be diminished if the graft is secured in
full knee extension when the tibial and femoral tunnels are placed in the
footprint of the native anterior cruciate ligament. More importantly, even
when the femoral and tibial tunnels are placed in the femoral and tibial
footprints of the native anterior cruciate ligament, fixing a graft in knee
flexion can result in the loss of knee extension.