Differences in transverse knee moment in healthy, ACL-deficient, and ACL-reconstructed patients during standing target matching
Date
2012
Authors
Journal Title
Journal ISSN
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Publisher
University of Delaware
Abstract
Anterior cruciate ligament (ACL) injury is a common injury affecting nearly
250,000 Americans a year (Boden et al. 2000). Reconstructive surgery costs add up to
approximately $1.5 billion annually not including initial evaluation or post-operative
rehabilitation (Boden et al. 2000). The anterior cruciate ligament (ACL) limits
anterior tibial translation and internal tibial rotation and so in the absence of the ACL
rotational instability is common. Transverse knee moment, which has not been the
focus of much research, can determine ACL-deficient (ACL-d) subjects’ ability or
inability to compensate for this rotational instability. Target matching, both standing
and seated, has provided insight for understanding neuromuscular control in both ACL
deficient and reconstructed patients via EMG measurements (Williams et al. 2003;
Macleod et al. 2011). We are now beginning to look at kinetic measures like
transverse knee moment during this task in healthy, ACL-d and ACL reconstructed
patients.
Therefore the first aim of this work was to investigate transverse knee
moment measured during a neuromuscular task in a healthy population. There is no
difference in transverse knee moment between the right and left limbs of healthy
subjects during standing target matching. Additionally, the shear forces generated by
the mobilizing limb strongly correlate with the transverse knee moment of the
stabilizing limb. These results indicate kinetic measures produced during standing
target matching are dictated by target matching role not the limb itself. The second aim of this work was to evaluate transverse knee moment
measured during a neuromuscular task in ACL-d patients. Our results show those with
ACL injury have significantly higher internal rotation moments than healthy uninjured
subjects. Increased rotational loads are present when subjects generate medial shear
forces. This indicates an area of interest and the importance of joint stability in this
medial direction.
The third and final aim of this work was to evaluate changes in transverse knee
moment during a neuromuscular task in ACL reconstructed patients. In particular we
tested subjects within six months to one year post reconstruction when re-injury risk is
highest (Salmon et al. 2005; Paterno et al. 2012). From this study we found those who
undergo ACL reconstruction produce higher internal rotation moments when
compared to uninjured subjects. We also see increased rotational loading at medial
targets. In our group of subjects it appears that increased rotational loading occurs
after injury and is not mitigated by reconstruction.
The resulting increase in joint loading may have implications for high re-injury
rates seen post reconstruction (Hewett et al. 2012) and high rotational loads have
already correlated with increased cartilage loss (Henriksen et al. 2012). Producing
force in a medial direction may be dangerous for those with ACL injury even after
reconstruction and could be used to identify those at higher risk of re-injury. These
results provide a basis to explore rotational loading corresponding to different graft
types while exploring possible interventions to create joint stability in this medial
direction.