Dynamic Computed Tomography for assessment of Knee Rotational Stability after Anterior Cruciate Ligament Injury

Anterior cruciate ligament injury is one of the most common serious knee
injuries in the young athlete. The anterior cruciate ligament (ACL) plays an
essential role in knee function. It provides stability of the knee in anterior­
posterior direction as well as in rotation. If conservative treatment of an ACL
injury fails or the patient has a very active lifestyle, ACL reconstruction
surgery is the gold standard for treatment. There has been a lot of development
in ACL reconstruction surgery techniques the past decade. The reconstruction of
the ACL complies two main goals, namely: restoration of anterior to posterior
stability and restoration of rotational stability.
The anterior to posterior stability of the knee can be assessed by physical
examination by the Lachman test and the anterior drawer test and the KT­1000
measurement tool. These test are straightforward and have moderate to good
sensitivity and specificity if performed by an experienced orthopaedic surgeon.
Though anterior to posterior stability can be measured in a straightforward
manner. To measure rotational stability, only physical examination by the pivot­
shift test is available. The pivot shift test is a manually performed test,
which has gradings from 0­3. When the patient is apprehensive, the test cannot
be performed reliably. Furthermore there is a lot of inter­observer variability.
One of the reasons the ACL reconstruction fails is assumed to be persistent
rotational instability of the knee after ACL reconstruction. Recent studies
correlate residual rotatory instability with decreased patient satisfaction,
increased functional instability, chondromalacia and the development of
osteoarthritis. The possible importance of knee rotational stability for
patient satisfaction urges the need for an quantitative straight­forward
measuring tool for the assessment of rotational stability of the knee before
and after intervention for ACL injury.
Recently CT scanners have improved a lot. Today it is possible to assess a
beating heart by the use of CT. Scanning time and with this radiation exposure
is decreased tremendously in newly developed machines. These new generation CT
scanners also make it possible to assess moving joints as is already been shown
in the wrist carpal joints and the patella­ femoral joint. The movement of
translation and rotation of different bones can be obtained in a highly
quantitative and reproductive manner. Though, recently it is proved that
dynamic CT scanning can be performed on the patello0­femoral and the wrist
carpal joints. The movement of the tibia in relation to the femur and hereby
assessment of rotational stability of the knee after ACL injury has never been
shown.
The availability of a dynamic CT­scanner in the IJsselland hospital provides
the opportunity to assess rotational stability of the knee using this technique.
This technique might provide essential information of knee dynamics before and
in a later stage after ACL reconstruction and hereby, patient satisfaction.

For this technique is new and has never been applied for assessment of knee
stability, our first goal is to assess the normal rotational stability of the
compared to the ACL­injured knee. Measuring knee rotational stability of ACL
deficient compared to ACL intact knees using dynamic­CT.
We will test the feasibility, and the ease of the technique.

A feasibility study / pilot study will be performed first. The arbitrary number
of 10 subjects with symptomatic unilateral ACL deficiency will be included. A
dynamic CT scan will be performed of the injured as well as the uninjured knee
to assess the rotations of the femur versus the tibia.
It will be a cross­sectional study.

The participants will be informed about this study by the principle
investigator.
The patients will have one additional visit to the hospital for dynamic­CT
scanning of the knees. This visit will take approximately 45 minutes. The
dynamic­CT scan of the knees will give a dose of approximately 0.6 mSv in
total.
This is a low dosage, as in contrast; a normal CT scan of the hip is 3 mSv and
the thorax is 18 mSv. The yearly exposure to radiation from natural sources is
about 2 mSv.
There is no individual benefit for the participant, though the results might in
future predict the patient satisfaction after an intervention, and might change
interventional strategies.