Gordon, Benjamin
Description
Injury to the anterior cruciate ligament (ACL) is a career
limiting event for many sports people. Irrespective of a
person’s activity level and whether they undergo surgery or
conservative rehabilitation, ACL injury can lead to
osteoarthritis later in life and other comorbidities. ACL injury
rates remain high despite considerable research to reduce its
incidence. Therefore, novel methods for preventing ACL injury
are needed.
In a published...[Show more] literature review presented in the introduction of
this thesis it is noted that ACL injury incidence is greater in
athletic populations, particularly in field and court sports,
with approximately 50-80% of those being non-contact in nature.
It showed little disagreement exists about the importance of
dynamic knee joint stability for reducing ACL injury risk. To
date, little research into dynamic knee joint stability has been
conducted. This could be because of difficulty in measuring knee
joint stability dynamically in-vivo, or due to difficulty
identifying novel practices/methods which incorporate dynamic
knee joint stability. This work proposed musculotendinous
stiffness, or ‘stiffness’ as it is referred to in this
thesis, as novel, relevant and worthy of investigation.
A second literature review defined stiffness as a quantification
of resistance against force. Specifically, vertical stiffness
was described as the body’s resistance to vertical displacement
from ground reaction force, affected by the interaction of
connective tissue, muscle and bone, as well as stiffness at each
joint. Therefore, this thesis addresses the question “is
vertical stiffness associated with common traumatic
musculoskeletal injuries in the football codes?”. A novel
method of measuring dynamic knee joint stability and a surrogate
measure of ACL loading in-vivo was applied which involved image
registration of computed tomography with fluoroscopy to build a
4-D model of knee joint motion.
This thesis is a compilation of published research papers. The
study in chapter two showed hamstring and quadriceps
pre-activation and co-activation is related to vertical stiffness
for a task which simulates the manoeuvre typically observed when
non-contact ACL injury occurs in field and court sports. Chapter
three found no difference in vertical stiffness between a cohort
of Australian Rules footballers who sustained a muscle strain
injury and an uninjured cohort. This outcome was important
because muscle inhibition can remain for 12 months following
injury and, as identified in the previous study, thigh muscle
function is important for vertical stiffness and, likely, knee
joint stability. Chapter four used the novel technique described
for measuring dynamic knee joint stability and ACL elongation
in-vivo on a step-up task while also measuring hamstring and
quadriceps activity. It argued hamstring and quadriceps
co-activation is not associated with ACL elongation. Finally,
chapter five used the same method to measure dynamic knee joint
stability on a task similar to that used in chapter two and
failed to find a link between vertical stiffness and ACL
elongation.
This work found no evidence of an association between vertical
stiffness and some common traumatic non-contact injuries. It
concluded training programs which enhance vertical stiffness may
be implemented without concern for injury. Suggestions for
future research are also made.
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