Failed adaptability in motor programming after ACL injury ?

Most athletes who sustain an injury to the ACL and want to stay active in of
sports elect to have their injured ACL reconstructed. However, successful ACL-
reconstruction in terms of restoring the ligaments of the knee joint does not
automatically mean restoration of normal knee function. For example, normal
walking is regained in only 31% of ACL-reconstructed patients 1 year after
surgery. In addition, functional abnormalities have also been reported in more
demanding tasks such as jumping. The findings of these functional deficits
reported in the literature are not fully understood until now. It appears that
patients sustaining an ACL injury develop an adaptive motor programm. An ACL
injury leads to a loss of proprioception in the knee-stabilizing muscles of the
thigh. Indeed, direct reflex pathways haven been reported between the ACL and
the muscles around the knee. An increase in the latency of the hamstring
reflex induced by anterior tibia translation, may be induced by a deficient
proprioception. There is some evidence that a lesion of the ACL results in:
1) Modifications in the response properties of the Central Nervous System (CNS)
such as increased response threshold or latency
2) Changes of the cortical representation by afferent inputs of the nearest
areas;
3) Reorganization of the spinal input.
These changes were present after injury of the ACL, but interestingly persisted
after reconstruction of the ACL. This implies that cognitive changes in motor
control may have occurred after injury of the ACL.
It is hypothesized that patients (un-)consciously hold on to the protective
motor program that suited the first post-injury period but may not be
functional anymore six months ore longer after surgery. Hence, the latency
reflexes are the primary interest of this study as information can be gathered
about possible alterations in CNS processing after the injury.

The goal of the study is to gain insight in the changes in motor control
programming after injury to the ACL and subsequent reconstruction of the ACL.
The following hypotheses: will be tested:
1. Reflex latencies on the involved side are increased when compared to the
uninvolved side in patients
2. Reflex latencies in the involved side in patients are increased when
compared to control subjects.
3. Reflex latencies in side to side comparison in patients are increased under
dual task conditions when compared to healthy subjects

The study will be a longitudinal observational study. Patients will be tested
pre-operatively within 1 year after they sustained an injury to the ACL .
Post-operatively they will be tested at 6 months and finally at 1 year. The
healthy controls will only be tested once to establish comparison data.

Minimal risk or discomforts, as physical injury or harm, to the subjects as a
result of each procedure is involved in this study as this research proposal is
viewed as involving little or no risk to human subjects. The main possible risk
of injury is giving way during the performance of the task. However, the
probability and magnitude of harm or discomfort anticipated in the proposed
research are not greater than those ordinarily encountered during the
performance of routine athletic activities. Furthermore, in order to minimize
the risk of injury, the subjects are well-trained healthy athletes and they
have the opportunity to get familiar with the movements before starting the
measurements.