Operative treatment of AO Weber C fibular fractures with additional posterior malleolar fragment: functional outcome after SYNdesmotic positioning screws or POSTerior fragment fixation. POSTFIX-C trial: a prospective comparative observational study.

In AO Weber type C fractures, there is a combination of a proximal fibular
fracture, a medial fracture or ruptured deltoid
ligament, and a syndesmotic injury. Anatomical repair and reduction of the
syndesmosis is essential to prevent diastasis in
the ankle-joint. Widening and chronical instability of the syndesmosis is
related to worse functional outcome and
development of posttraumatic osteoarthritis in the ankle. There is limited
biomechanical and clinical evidence that
syndesmotic stability in AO Weber type C fractures with an additional posterior
malleolar fracture can also be reached by
fixation of the posterior malleolar fragment. Maybe, this is even superior to
the usual treatment with syndesmotic
positioning screws. Some authors concluded that stability of the syndesmosis in
these fractures can be much more
achieved by fixation of the posterior malleolar fragment than by placement of
syndesmotic positioning screws alone.
Another additional benefit of open reduction and fixation of the posterior
malleolar fragment is that this will lead to an
anatomical reconstruction of the syndesmosis. Although there is no current
evidence, it is likely that a malreduction of the
fibula in the tibial incisura will lead to a worse functional outcome on the
long-term. No clear consensus in the literature is
found as to which fragment size of the posterior malleolus should be internally
fixed. The general opinion is that displaced
fragments that involve more than 25% of the distal articular tibia should be
fixed. Traditionally, reduction of these larger
fragments is indirectly, followed by percutaneous screw fixation in
anterior-posterior direction. Disadvantages are that it is
hard to achieve an anatomical reduction, and that percutaneous fixation of
smaller fragments is very difficult. Recently, a
direct exposure of the posterior tibia via a posterolateral approach in prone
position, followed by open reduction and
fixation with screws in posterior-anterior direction or antiglide plate is
advocated by several authors. This approach allows
perfect visualization of the fracture, articular anatomical reduction, and
strong fixation. Another advantage is that even
small posterior fragments can be addressed. Several case series are published,
which describe minimal major wound
complications, good functional outcomes, and minimal need for reoperation.

To compare the accuracy of syndesmotic reduction on an axial CT-scan
postoperatively (reflecting syndesmotic
malreduction) after anatomical open reduction and fixation of the posterior
malleolar fragment versus no fixation of the
posterior fragment in AO Weber-C ankle fractures with involvement of the
posterior malleolus.

Multicenter Prospective cohort study,
Participating Centers:
1. Haaglanden MC
2. Leiden University Medical Center

Patients presenting with an ankle fracture at the Emergency Department of the
hospital will receive the usual treatment
initially. Patients who met the inclusion criteria will be informed at the
emergency department about the current study and
will get the written patient information. Before visit of the outpatient
clinics a CT-scan of the ankle will be performed.
Preoperatively, at the outpatients clinic or ward, the surgeon will discuss the
study again with the patient and he or she is
asked to participate. The choice will be between placement of syndesmotic
screws (group 1) or Open Reduction and Fixation of the posterior fragment
(group 2).

Patients in the first group will be treated according to the current
directives. If present, medial and distal fibular shaft fractures are fixed
according to AO principles. The syndesmosis will be reduced by 1 or 2
transsyndesmotic screws. The second group will be treated by open reduction and
fixation of the posterior malleolar fragment using the posterolateral approach.
If the ankle shows stability after fixation, no transsyndesmotic screws will be
placed.

Post-operatively, a CT-scan of both ankles will be performed in order to
evaluate the success of reposition of the fibula in the tibial incisura and the
posterior fragment. The postoperative treatment will be identical and according
to the current local protocols. Patients will be seen at the outpatient clinics
at 2 weeks, 6 weeks, 12 weeks, 26 weeks and 52 weeks postoperatively. In
addition to the regular treatment, the patients will be asked to fill in a
questionnaire during every visit and to perform a short functional test during
the last 2 visits. The results between these two groups will be compared.

Additional to the regular treatment, the burden lies in the fact of several
questionnaires which will be answered during the
visits at the outpatient clinic. Also, postoperative a CT-scan of the ankle
will be performed. The additional radiation is in
our eyes negligible respected the normal, daily background radiation in the
Netherlands.
Several case-series showed a comparable rate of woundinfections or reoperations
in the posterolateral approach
compared to the original approach.