Foot & Ankle International - September 2020 - 1159

Mococain et al
fracture and possible syndesmotic injury. PER injuries also
include these level IV fractures results in an unstable ankle,
with widening of the medial clear space, lateral translation
of the talus, and decreased tibiotalar contact area.9
Bimalleolar equivalent ankle fractures consistent of a lateral
malleolus fracture with concurrent deltoid ligament injury
and insufficiency instead of a medial malleolus fracture.
The current standard for operative stabilization of bimalleolar ankle fractures is open reduction and internal fixation
(ORIF) of the lateral and medial malleoli followed by syndesmotic stabilization if there is widening of the syndesmosis after fixing the medial and lateral structures. In
bimalleolar equivalent ankle fractures, there is controversy
regarding the necessity of repairing the deltoid ligament,
especially in the setting of concomitant syndesmotic injury.
Typically, the lateral malleolus is reduced and fixed and
syndesmotic fixation is performed if necessary. This closes
the medial clear space through indirect reduction and
restores the anatomic relationship between the medial malleolus and the talus, which allows the deltoid ligament to
heal with appropriate length and tension. However, syndesmotic fixation is accompanied by the risk of tibiofibular
synostosis, screw breakage, and late diastasis.13 Additionally,
screws are frequently removed, which necessitates another
operative procedure and its associated risks and costs.
Recently, stabilization of the syndesmosis with a suture button device has been shown to have better patient-reported
and radiographic outcomes, and it does not require removal.1
However, this method of fixation is also not without complications, as there are reports of skin irritation from the
medial button and infection with abscess formation surrounding the nonabsorbable sutures in the device.12
An alternative strategy for treatment of bimalleolar
equivalent ankle fractures is to fix the lateral malleolus fracture and to restore the native anatomy of the ankle solely by
repairing the deltoid ligament, without placing a screw or
other fixation device across the syndesmosis. Comparable
clinical outcome has been reported when this approach is
used,6 but supporting biomechanical evidence is lacking. To
address that deficit, this investigation was designed to comprehensively quantify ankle joint stability in an ankle fracture soft tissue injury model with syndesmosis and deltoid
disruption when treated with syndesmotic fixation alone,
deltoid ligament repair alone, and both syndesmotic reduction and deltoid repair. The authors hypothesized that a deltoid ligament repair with syndesmotic fixation would
improve stability in this model when compared to syndesmotic fixation alone.

Methods
Institutional IRB approval was obtained for this study. Nine
fresh-frozen whole lower limbs were disarticulated at the
knee joint, and the skin and muscle superior to the ankle

1159

Figure 1. Posterior view of lower leg mounted in testing
apparatus.

joint were removed. The mean age at death for the specimen
donors was 56 years of age, with a range of 33 to 68. Three
8-mm-diameter lag screws were inserted into the tibial plateau such that their shanks projected superiorly and embedded in an aluminum tube filled with polyester auto body
filler to facilitate attachment to the testing apparatus. The
length of the screws was variable based on anatomy and
long enough to ensure adequate fixation to the testing apparatus. The tube was maintained coaxial with the tibial shaft
during this embedding process. In a similar fashion, several
8-mm lag screws were inserted into the plantar surface of
the calcaneus and their projecting shanks embedded in an
aluminum cup oriented parallel to the transverse plane of
the limb with the ankle in neutral position.
The limb was placed in a specially designed testing device
such that the tibia shaft was vertical, and the cup located at
the superior end was clamped to a carriage incorporating linear and rotary bearings that permitted unconstrained rotation
and superior-inferior translation during subsequent application of internal and external rotational forces (Figure 1). The
rotary bearing allowed precise torsional loads to be applied to
the tibia through a system of levers, cables, pulleys, and
weights. Tibia shaft rotation was measured with a resolution
of 0.001 degree during the testing by a modified digital
machinist's protractor fixed to the rotary bearing (Model
54-440-750; Fred V. Fowler Company). The cup to which the

Foot & Ankle International - September 2020

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