Affiliations: [a] Department of Orthopaedic Surgery, Hannover Medical
School (MHH), Hannover, Germany
Note: [] Corresponding author: Dr. med. Sven Ostermeier,
Orthopädische Klinik der MHH, Klinik II im Annastift, Anna-von-Borries-Str.
1-7, Hannover, Germany. Tel.: +49 511 5354 548; Fax: +49 511 5354 682; E-mail:
sven.ostermeier@annastift.de
Abstract: Background: The objective of this study was to investigate
dynamically the load on the cruciate ligaments and the effect of simulated
co-contraction of the hamstrings muscles on quadriceps force and load on the
cruciate ligaments. Methods: Load transducers were fixed in the fibers of
the anterior and posterior cruciate ligament of seven knee specimens.
Isokinetic extension motions applying an extension moment of 31 Nm,
representing an extension moment capable by healthy human volunteers in
isokinetic extension tests, were simulated in a knee simulator from
120° to full knee extension. Quadriceps force and load on the cruciate
ligaments were measured in the absence and presence of a 200 N hamstrings
co-contraction. Results: Quadriceps force significantly (p=0.04)
increased under the application of hamstrings co-contraction. Anterior cruciate
ligament load significantly increased below 20° knee flexion up to
161 N and was significantly (p=0.04) reduced to 29 N under hamstrings
co-contraction at full knee extension. Posterior cruciate ligament load without
hamstrings co-contraction showed a maximum load at 112° knee flexion
of 38 N, reducing to knee extension and was not significantly increased
(p=0.20) under hamstrings co-contraction, showing a maximum load of 66 N near
knee flexion. Conclusions: This dynamic in vitro study revealed the
dependency of anterior cruciate ligament load on knee flexion angle during an
isokinetic extension cycle. With a co-contraction of hamstring muscles the peak
load on the anterior cruciate ligament was significantly decreased in knee
extension with a non significant concomitant increase of posterior cruciate
load at knee flexion. These findings have implications for graft donor site
selection and postoperative rehabilitation, e.g. after anterior cruciate
ligament reconstructions.
