Validating the Positioning Protocol for Whole Leg Radiography

Important in the management of varus or valgus induced osteoarthritis (OA) are
whole leg radiographs (WLR) [1]*[6]. WLR*s are being used to determine the
amount of malformation in the leg. These malformations result in increased load
bearing to a certain knee compartment, at the same time an unloading in the
opposite compartment. The increased stress on the carti-lage can cause OA. To
determine whether there is a malalignment in the leg, the hip knee angle (HKA)
is measured on a WLR.

Literature describes many new insights regarding the varying positioning of
patients during a WLR and the effects on the measured HKA. Known affecters are:
knee flexion and exten-sion, foot rotation, hip rotation, weight-bearing and
foot positioning [4], [6]*[20]. There is for instance a difference in patient
positioning between a single or double legged WLR which af-fects the measured
HKA. However, no standard or optimal limb positioning protocol for the WLR is
widely known or is being used [6], [9], [11], [17], [21], [22]. Sheehy and
Cooke pro-posed a more standard protocol, which is to the best of our knowledge
not widely implement-ed or validated [6], [17].

Pre-operative planning uses such WLR*s, where the amount of correction is
derived from the measured HKA. Therefore, pre-operative planning is prone to
errors if patients are not posi-tioned correctly for a WLR, resulting in under-
or overcorrection when performing a correction osteotomy. Thereby, variances in
positioning pre- and post-operative result in wrong interpre-tation of surgical
results. For instant postoperative pain affects the weight-bearing and
there-fore the HKA. [7], [12].

We strongly recommend a more standardized and uniform approach for the
positioning of the patients, which would be suitable to implement in the
current care. We believe that the Akagi line is a good representation of the
antero-posterior alignment of the knee-joint, described by Akagi et al. as the
line between the centre of insertion of the posterior cruciate ligament to the
medial border of the tuberosity [23]*[26]. When using known literature
describing the tibial rotation, the mean is about 25 degrees external rotation
but with a high standard deviation, where there is no difference between OA
patients and healthy population [27]*[31]. This angle is between the Akagi line
and antero-posterior line of the malleoli [26]*[30], [32], [33]. The an-gle
between the Akagi line and longitudinal axes of the feet in neutral stance is
around 10 de-grees, and 0 degrees with the first metatarsus [29], [34]*[39].

We believe that a uniform and standard protocol should be implemented, with the
focus on eliminating leg rotation and take the mean tibial rotation into
account. Patients are positioned in full extension with their heels touching
each other and the feet pointing outwards with 25 10 degrees of rotation. This
is achieved by drawing a V on the ground with an angle of 50 de-grees between
the two lines by placing two feet templates on the ground with an angle of 20
degrees in between, the feet are 10 cm apart from each other. The patients have
to place their medial border of the feet against the lines with the heels
against the crossing point of those lines. Practitioners thereby control the
hip rotation, by placing the upper body in a straightforward position. No
handlebars or support are allowed to ensure full weight-bearing. The
practitioners additionally instruct the patient to distribute the weight
equally to each leg. This protocol is currently being used at UMC Utrecht.
However, its reproducibility is not tested yet.

The aim of this study is to determine the test-retest reproducibility of the
developed positioning protocol for WLR*s of a patient over time. The measured
HKA will be used as the main pa-rameter to calculate the reliability. At the
same timeThe second objective of this study,: we want to compare three
different measuring methods for the measurement of the HKA. This includes one
manual method as being used in the current practice and two semi-automatic
methods.

Primary Objective: Test-retest reliability of the measured HKA when patients
are positioned following our specific positioning protocol.
The main study parameter will be measured using the method as in the current
practice. This is a manual method, where the practitioner uses an angle tool
pro-vided by Sectra and available in Pacs IDS 7 image viewer. The practitioner
has to select 3 points on the WLR, the centre of the femoral head, the centre
of the tibial spines and the centre of the talus. This is a standardized method
with proven re-producibility [4].


Secondary Objective: Compare different measurement methods for calculating the
HKA on a WLR. The first method is the manual technique, the other two methods
are semi-automatic.

Prospective explorative study, with whole leg radiographs.

Patients will be treated following current regular practice and have no direct
benefit of par-ticipating in this study. Results will help to elucidate the
performance of the patient posi-tioning protocol and may provide tools for
improvement of (novel) cartilage repair strate-gies.

The additional risks of one extra radiograph is an added radiation dosage for a
patient of 0.0192 mSv, as determined by our Radiology Division. In 2016 the
RIVM reported an av-erage radiation dose of 0.004 mSv during a West-European
flight. The RIVM also re-ported a yearly background radiation dosage of 2.6 mSv
per citizen per year.