Foot & Ankle International - September 2020 - 1147

Haupt et al

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Figure 3. Demonstration of the "center-center" view obtained on a lateral fluoroscopic projection with over-internal rotation at
3 heights above the tibial plafond within a single specimen. The specimen also has a Kirschner wire and cannulated screw implanted.
The horizontal line demonstrates the height at which "center-center" is being evaluated. The height of the "center-center" position
progressively increases from A to C away from the tibial plafond. The increase in distance from the plafond requires a compensatory
increase in limb internal rotation for each image. This is supported by the lateral malleolar shadow at the level of the tibiotalar joint
appearing more anterior in each image from A to C, as well as rotation of the screw and kirschner wire.

Additionally, Miller et al demonstrated that when the clamp
and screw axis deviate from a neutral axis, it will result in
syndesmosis displacement.11 Based on the images provided,
their neutral axis was located approximately 5 degrees posterior to the centroid and center-center axes but was found to
cause minimal malreduction. In comparison, 15- and
30-degree anterior axis deviations caused progressively
greater displacement.
A clinically important secondary finding was that external rotation of both center-center and centroid axes occurred
in unison as a function of increasing distance from the tibial
plafond (Figure 3). The rotational change varied by individual, ranging up to 6 degrees per 10-mm distance change.
These data indicate that the limb rotation must be adjusted
for each location used for center-center fixation axis
alignment.
The primary limitation of this study is the simulation of
the fluoroscopically produced center-center alignment methodology using axial CT slices. Although axial CT slices differ from the lateral fluoroscopic view that would be used
intraoperatively when implementing the center-center technique, the anatomy and measured anatomical landmarks are
equivalent. In other words, regardless of whether a centercenter fluoroscopic view or an axial CT centroidal view is
used, the goal is equal spacing between the medial border of
the fibula and tibia and the lateral border of these same
bones. The fact that the goal is driven by anatomy, not

imaging plane, gives credence to our simulation method.
Secondary limitations include the study's retrospective
design and sampling methodology, which identified only
normal ankle CT scans. Although the strict inclusion criteria
were implemented to filter patients with injury or deformity,
which may skew the results, it also limited the sample size
and may have affected the measured variability. Despite
these limitations, the studied images represent a small, but
diverse, set of individuals in terms of sex and age. The next
logical step will be a clinical simulation study evaluating the
accuracy and precision of placing syndesmotic fixation
along the centroid axis using the center-center technique in
cadaveric specimens prior to prospective clinical work.

Conclusion
As a whole, the findings of this study strongly suggest that
the center-center technique is a viable clinical strategy for
accurately aligning syndesmosis fixation axis alignment
through the centroids of the tibia and fibula. This alignment
rotated externally as a function of distance proximal from the
tibia plafond. This method empirically achieves patient-specific syndesmosis fixation and amounts to a novel and apparently valid refinement over the traditional technique that has
potential for broad impact on clinical practice. However, further work is needed to assess the center-center technique in
terms of efficacy, accuracy, precision, and safety.

Foot & Ankle International - September 2020

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