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In an acute traumatic setting, the dropfoot origin should
be clearly identified. In cases in which no tendon or nerve
damage are evident, neurapraxia is the most probable cause.
After a prudent period of observation (approximately 1
year), if no neurologic improvement is demonstrated, ten-
don transfers can be considered.8
A tendon transfer procedure has to fulfill several princi-
ples to be successful. The tendon to be transferred should be
a healthy tendon, restore normal anatomic relationships
between the tendon and its sheath, reroute through adequate
tissue to allow proper gliding, restore normal tendon ten-
sion, re-create anatomical tendon insertion, and establish
proper line of tendon pull.12 A usually preserved function-
ing tendon is the tibialis posterior. This tendon is frequently
a deforming force too, yielding active unopposed plan-
tarflexion and inversion. Therefore, it is a good candidate to
be transferred in cases in which the function of the antero-
lateral compartment of the leg is compromised. Many
aspects of tendon transfers are still debated, such as route of
transfer, transferred tendon tension, type of bone attach-
ment, tendon to be transferred depending on the motor unit
lost, number of tendons to transfer, and so on. There are
some techniques that use combined transfers for dropfoot
cases. The Bridle procedure11 combines the peroneals and
flexors to balance and strengthen the tibialis posterior dor-
siflexion. The study published by Vigasio et al15 shows a
similar principle as the Bridle, but with tendon to tendon
tenorrhaphy instead of tendon to bone attachment.
Two main routes exist for the tibialis posterior tendon
transfer (ie, transmembranous and circumtibial [CT]).
There are studies that support both routes with satisfactory
outcomes.1,6 The transmembranous is performed through an
interosseous membrane window, 15 cm above the ankle
joint. The CT is routed through the subcutaneous fatty tis-
sue in the distal tibia, around the medial surface of the
medial malleolus, being substantially easier and faster than
the transmembranous, potentially having a greater lever
arm and thus better muscle strength.6,17 Nevertheless, given
its subcutaneous and oblique passage around the tibia, there
could exist an increased tendon friction that may hinder a
good functioning transfer. Other risks include adhesions
and the possibility of a palpable tendon, given that the
whole transfer is subcutaneous. The transmembranous
transfer is more mechanically sound, given its more direct
line of pull, but it has a smaller lever arm, having potentially
less strength but better dorsiflexion capability.13 However, a
few additional risks exist (ie, narrowing of the membrane
window with possible entrapment, neurovascular damage
risk, tendon adhesions to the membrane, etc).5,10
The transmembranous transfer can be performed above
and below the extensor retinaculum. The current recom-
mendation is to perform the transfer above the extensor reti-
naculum.6 Nevertheless, there is no serious biomechanical
comparison among both routes.

Foot & Ankle International 39(7)
The objective of this study was to compare and analyze
the CT and transmembranous transfer routes, measuring the
tendon gliding resistance and foot kinematics for each
transfer in a cadaveric specimen. In addition, 2 transmem-
branous transfers were analyzed, above the ankle extensor
retinaculum (TMAR) and under the retinaculum (TMUR).
Our first hypothesis was that the transmembranous route
would achieve better kinematic function with less gliding
resistance than the CT route. Our second hypothesis was
that the TMAR transfer would achieve less gliding resis-
tance than the TMUR transfer.

Methods
Eight cadaveric fresh frozen foot-ankle distal tibia speci-
mens were prepared, with at least 30 cm of tibia and fibula,
identifying all extensor and flexor tendons proximally. The
skin and subcutaneous tissue were kept intact. All speci-
mens were inspected to rule out any evidence of previous
trauma or decreased ankle range of motion. The mean age
of the donors was 56 years (range, 52-65). Specimens were
kept frozen at −20°C in a sealed plastic bag. Before testing,
each specimen was thawed at room temperature one at a
time, and extra care was taken to keep the specimens at a
constant temperature and moisturized with saline solution.
Each specimen was mounted on a special frame, and reflec-
tive markers were attached to the skin to adapt it to the
Oxford Foot Model.14
The foot was filmed in a closed room, to determine the
tridimensional change in position of every foot when sub-
jected to testing. Any associated supination, pronation,
adduction, and abduction was recorded. This was performed
with 8 infrared cameras (Vicon Serie-T, Vicon Motion
Systems Lt., Oxford. UK) symmetrically positioned around
the room that detected (sample rate = 50 Hz) the reflective
markers movement throughout the testing.
A dead weight equal to 50% of the stance phase force was
applied to almost every tendon: peroneus brevis, peroneus
longus, flexor digitorum longus, flexor hallucis longus,
extensor digitorum longus, and extensor hallucis longus
(Figure 1). No weight was applied to the Achilles tendon.
Each specimen served as its own control, testing dorsi-
flexion when pulling the tibialis anterior, performing a
10-repetition cycle of dorsiflexion and plantarflexion using
a tensile testing machine (Kinetecnics, Santiago, Chile). The
movement of the foot was recorded, and the force needed to
achieve dorsiflexion was registered in every cycle.
Then, a TMAR tibialis posterior tendon transfer was per-
formed in each specimen, through 4 incisions as in a real
clinical situation. The first incision was on the medial aspect
of the foot, just proximal to the insertion of the tibialis pos-
terior tendon on the navicular bone. The tendon was
obtained as long as possible and recovered from a second
medial and more proximal incision 15 cm above the ankle



Table of Contents for the Digital Edition of Foot & Ankle International - July 2018

Contents
Foot & Ankle International - July 2018 - Intro
Foot & Ankle International - July 2018 - Cover1
Foot & Ankle International - July 2018 - Cover2
Foot & Ankle International - July 2018 - i
Foot & Ankle International - July 2018 - ii
Foot & Ankle International - July 2018 - Contents
Foot & Ankle International - July 2018 - iv
Foot & Ankle International - July 2018 - v
Foot & Ankle International - July 2018 - vi
Foot & Ankle International - July 2018 - vii
Foot & Ankle International - July 2018 - viii
Foot & Ankle International - July 2018 - 1A
Foot & Ankle International - July 2018 - 1B
Foot & Ankle International - July 2018 - ix
Foot & Ankle International - July 2018 - x
Foot & Ankle International - July 2018 - xi
Foot & Ankle International - July 2018 - xii
Foot & Ankle International - July 2018 - 2A
Foot & Ankle International - July 2018 - 2B
Foot & Ankle International - July 2018 - xiii
Foot & Ankle International - July 2018 - xiv
Foot & Ankle International - July 2018 - xv
Foot & Ankle International - July 2018 - xvi
Foot & Ankle International - July 2018 - xvii
Foot & Ankle International - July 2018 - xviii
Foot & Ankle International - July 2018 - xix
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Foot & Ankle International - July 2018 - xxi
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Foot & Ankle International - July 2018 - xxiii
Foot & Ankle International - July 2018 - xxiv
Foot & Ankle International - July 2018 - xxv
Foot & Ankle International - July 2018 - xxvi
Foot & Ankle International - July 2018 - 3A
Foot & Ankle International - July 2018 - 3B
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Foot & Ankle International - July 2018 - Cover3
Foot & Ankle International - July 2018 - Cover4
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