Foot & Ankle International - June 2017 - 695

LaMothe et al
the tibial plafond led to a 42% decrease in contact area. This
has come to be the rationale for reducing and repairing syndesmotic injuries.
Syndesmotic reduction is critical for stabilizing the
joint22 and improving patient outcomes following an ankle
injury, and malreduction of the syndesmosis has been linked
to worse patient outcomes.4,14,24,26,34 Several syndesmotic
reduction techniques have been reported and may influence
ankle contact mechanics differently. Using a clamp to
reduce syndesmotic injuries may predispose to syndesmotic
malreduction.20 Other strategies to reduce syndesmotic
injuries include open reduction21 or arthroscopic assisted29
reduction, and reduction can be held with a conventional
screw construct or a suture-button construct,30 the effect of
which is poorly understood. Therefore, it is important to
identify how different reduction and fixation techniques
affect global tibial plafond contact mechanics.
The purpose of this study was to determine if syndesmotic reduction techniques restore global tibial plafond
contact mechanics in an unstable syndesmotic injury model.
We tested 3 reduction techniques: screw reduction without
a clamp, screw reduction with a clamp, and reduction using
a suture-button construct. We hypothesized that reducing
the syndesmosis with a clamp would overconstrain the joint
and increase contact pressure and decrease contact area
while the other techniques would restore intact contact
mechanics.

Materials and Methods
Ten skeletally mature lower leg specimens (mean age, 64 ±
7 years) with intact proximal tibiofibular joints were used.
The sample size was chosen based on the reported difference in contact area with syndesmotic and deltoid disruption, using a power of 0.8 and α = .05.3 This resulted in a
sample size of 5 based on the conditions of maximum difference (intact vs completely disrupted). We chose to double the sample size to test for the smaller difference in mean
values likely present with the different conditions of reduction. Skin, muscles, and tendons were removed from the
ankle joint from 10 cm proximal to the ankle joint to the
midfoot while preserving the Achilles tendon. The plantar
aspect of the foot as well as all ligaments and joint capsules
were left intact. All specimens were free of any lower
extremity malalignment or trauma. Proximal tibiae were
dissected free of soft tissue to the level of the fibular head,
preserving the proximal tibiofibular articulation. The proximal tibia was secured in epoxy cement (Bondo; 3M, Atlanta,
GA, USA) with the mechanical axis of the tibia vertical in
no varus/valgus or flexion/extension. The specimen was
then placed in a mechanical testing device, and the foot was
placed on a low friction plastic surface and allowed unconstrained accommodative motion.

695
Using a cadaveric loading model,1 we examined the
effects of syndesmotic reduction techniques on ankle joint
contact mechanics. We applied a ground reaction force of
400 N and Achilles tension of 350 N to test 5 conditions:
intact, syndesmotic injury, screw reduction without a clamp,
screw reduction with a clamp, and suture-button reduction.
Prior to creating the syndesmotic injury, a fellowshiptrained foot and ankle trauma surgeon prepared a screw
hole for a best-case scenario of syndesmotic reduction: a
2.9-mm drill hole was placed along the transmalleolar axis
at the proximal aspect of the physeal scar. A drill hole was
placed in the intact situation to exclude gross malreduction
from the analyses. Next, we created a syndesmotic injury by
sectioning the syndesmotic ligaments (anteroinferior tibiofibular ligament, posteroinferior tibiofibular ligament,
transverse ligament, and distal 10 cm of interosseous ligament) and the deltoid ligament. This injury model was chosen as it represents the most unstable ankle syndesmotic
injury.12 The syndesmosis was then reduced using 3 techniques and tested in a randomized order.
Syndesmotic injuries were reduced using 3 techniques: a
thumb technique (no clamp), a reduction clamp, and a
suture-button construct. The thumb technique used the surgeon's thumb to palpate congruence of the anterior distal
tibiofibular incisura. No additional compression was used
with the thumb, and the thumb was only used to palpate
congruence of the reduction. When the fibula was manipulated with the thumb so that there was no palpable step or
gap between the tibia and fibula, this was defined as
reduced, and a 0.045-inch K-wire was used to provisionally
secure the fibula to the tibia. A tetracortical 4.0-mm screw
was then placed through the predrilled 2.9-mm drill hole,
and the K-wire was then removed. The clamp reduction
technique used a large Weber reduction clamp placed along
the transmalleolar axis with the ankle in neutral dorsiflexion. The transmalleolar axis was visualized perfectly on the
bones, and this is where the tines were placed. The clamp
was squeezed firmly to a point that estimated intraoperative
pressure. Standardized measures were not possible due to
the difference between cadaveric specimens. All clamping
was performed by a trauma and foot and ankle fellowshiptrained surgeon in a similar fashion. There was no noted
difference in anterior or posterior fibular translation with
clamping. The clamp was firmly squeezed to allow the syndesmosis to be firmly held in place. Following clamping,
the syndesmosis was secured with a tetracortical 4.0-mm
screw through the previously placed 2.9-mm drill hole. The
screw was tightened until the screw head was seated flush
with the lateral fibular cortex. A torque screwdriver was not
used given the variability in the material properties of the
different cadaveric specimens. If the ankle was clamped in
plantarflexion, there was visible medial and lateral ankle
joint gutter impingement that prevented normal articulation

Table of Contents for the Digital Edition of Foot & Ankle International - June 2017