Introduction
Syndesmosis injuries account for 11% of all ankle injuries, and can lead to chronic
pain and instability (1,2). Chronic conditions can be challenging for clinicians to
diagnose, debilitating for the patient, and lead to instabilities of structures surrounding the
joint (3,4,5). These conditions can lead to articular surface changes, heterotopic
ossification, scaring, chronic pain, and instability (3,5,6,7). Patient’s rehabilitation
protocols typically will extend for longer periods of time, which can result in time loss
due to the extent of the injury (3,4,6,7,8).
The purpose of this literature review is to emphasize the research about the
anatomy, pathomechanics, recognition, management, and rehabilitation protocols for
conservative and non-conservative syndesmosis conditions. Further encompassing areas
pertaining clinical tests, imaging techniques, surgical procedures, secondary injuries, and
the need for future research studies to help recognize this condition.
Syndesmosis Anatomy
The distal syndesmosis joint consist of the tibia, fibula, anterior inferior tibiofibular ligament (AIFL), posterior inferior tibio-fibula ligament (PIFL), inferior
transverse tibio-fibula ligament (ITFL), inferior interosseous ligament (IL) and the
interosseous membrane (IM) (3). These structures act to stabilize the distal syndesmosis
joint, allowing optimal positioning of the talus within the medial and lateral malleolous
and preventing tibio-fibula separation (10). The AIFL originates on the anterior-lateral
aspect of the tibia and runs obliquely to the anterior- lateral malleolus of the fibula (3).
With assistance from the anterior deltoid ligament, the AIFL prevents excessive eversion
of the talus, and excessive external rotation of the fibula (11). The AIFL along with the
PIFL provides most of the ligamentous stability for the distal syndesmosis joint (4,12,13).
The PIFL is the strongest syndesmosis ligament and runs obliquely from the
posterior malleolus of the tibia to the posterior lateral malleolus of the fibula (4,10). The
PIFL contains a superficial and deep component, which is known as the ITFL (3,10,11).
The ITFL lies inferior and horizontal to the PIFL and is thought to be a continuation of
the PIFL (3,10,11). The PIFL and ITFL help stabilize the posterior aspect of the
syndesmosis joint and are the last ligaments to be injured (10).
The interosseous membrane is composed of fibrous tissue that arises from the
superior lateral tibia, and extends to the distal medial fibula and prevents tibio-fibular
separation (3). Researchers categorized the interosseous ligament as a continuation or
thickening of the interosseous membrane at the distal end syndesmosis joint, and its
function is to transmit up to 15% of axial loads from the tibia to the fibula during weightbearing (3,4,14,15). The interosseous ligament can also assist with separation of the tibia
and fibula during dorsiflexion, which allows the talus to properly fit within the joint
space (3).
Pathomechanics
Syndesmosis injuries can occur in many sports including football, soccer, wrestling,
skiing, or other types of instances where the foot comes with either a player or playing
surfaces (8,10,16). Excessive external rotation motions can cause the talus to displace
laterally against the fibula, which can cause the fibular to externally rotate and separate
from the tibia (3,15,19,20). Research studies conducted on elite skiers concluded that
there is an increase amount of stress placed upon the joint during a dorsiflexed position
(4,17). As a result, the talus wedges itself between the tibia and fibula, increasing the
joint space width between the tibia and fibula (4,17). Research suggests tibiotalar
articulation decreases up to 42% when the talus is displaced laterally more than 1mm
(3,15,21). Typically, the AIFL is the structure most likely to be injured during external
rotation, eversion, dorsiflexion, or combined motions (3,4,10,22). The AIFL, PIFL, IL,
and anterior deltoid ligament help’s prevent rotation, excessive eversion, and movement
of the fibula in respect to the tibia (4,11,20). An injury to the AIFL can cause subsequent
injury to the interosseous ligament (4,23). Research on cadavers concluded that
disruption to the interosseous ligament does not cause disruption to the ankle mortise
during injury loads (4,23).
Assisted by the anterior deltoid ligament during dorsiflexion, the AIFL, and IL are
aligned in a horizontal plane during dorsiflexion (3,7,19,20). As a result, the talus wedges
within the joint space allowing for optimal ankle mobility (3,7,19,20). During
plantarflexion, motion occurs in the opposite direction causing the AIFL, and IL to move
vertically (7). The fibula internally rotates and moves distally, placing tension on the
AIFL during injury (7).
Clinical Examination Findings
Patients report a history of pain with activity, distal anterior-lateral leg pain, tenderness
between tibia and fibula, weakness, instability, and reduced range of motion
(3,4,8,9,20,24). It is critical for the examiner to note the location of tenderness from the
distal end to proximal end of the tibia and fibula (4,8,10,20,24,25). Researchers indicate
that tenderness length is directly correlated to time loss and severity of injury
(4,8,20,24,25). Test frequently administered include a positive squeeze test, kleigers test,
cotton test, and positive one-legged hop test (10,6,4,2,28).
X-ray
Radiographs typically are used to rule out avulsion fractures, fibula displacement and
any heterotopic ossification within the joint (4,5,8,9,10,20,21,27). Research suggests that
an anterior-posterior, lateral, and mortise view should be taken to confirm the integrity of
the tibiofibular clear space, tibiofibular overlap and mortise (4,5,8,9,10,20,27). An
anterior-posterior can determine the tibiofibular clear space, which is normally less than
6mm (4,5,8,9,10,20,27). The amount of tibiofibular overlap with anterior-posterior views
is typically greater than 42% of the fibula width (4,8,9,10,19,20,27,28).
Studies suggest lateral views could be taken with patients in non-weight bearing, and
external rotation to determine the extent of fibula displacement (4,19,29,30). Researchers
indicate normal medial clearance space to be between 2-4 mm (10,27,31). Radiographs
can exclude anterior deltoid ligament injuries exceeding in 1-2mm width between the
medial malleolus and the medial talus (10,27,31).
MRI & CT Scan
MRI and CT scans are 3 dimensional images that are usually taken in a front, axial,
and saggital view to determine the extent of injury (9,10,27,31). MRI can be used as a
tool to confirm the severity of disruption to ligaments, articular surfaces, and provide
information about the integrity of the distal tibiofibular joint (4,9,10,27,31,32). In
addition, MRI’s can detect any secondary conditions associated with the injury
(4,9,10,21,27,31,32). Research suggest CT scans can be more effective than radiographs
by showing less than 3mm of disruptions within joint (9,10,33,34).
Arthroscopy
Arthroscopy is considered to be the most reliable and precise tool when predicting
syndesmosis disruptions (5,36). Arthroscopic finding indicate that injuries can occur to
the AIFL, articular surfaces, and tibiofibular clear space (5,36). Researchers used the
Outerbridge Classification Scale to grade the extent of articular surface damage found
during arthroscopy (5,36). Researchers distinguish articular surface damage into five
different classifications: Grade 0 indicates normal cartilage (5,36). Grade 1 indicates
softening and swelling to the surfaces (5,36). Grade 2 indicates fissures and flaking of the
subchondral bone (5,36). Grade 3 indicates increase erosion and damage to the
subchrondral bone (5,36). Grade 4 indicates exposure to the subchrondral bone (5,36).
Classification of Injury
Researchers used the West Point Ankle Instability Scale to classify injuries into three
categories including mild, moderate to severe (9,20,37,38,39). Grade 1 syndesmosis is
considered to be a mild disruption of the AIFL, and the IL without instability
(9,20,37,38,39). Grade 2 and Grade 3 syndesmosis injuries are considered to be unstable
injuries, which require surgical intervention (9,20,37,38,39). Grade 2 injuries can cause
disruption of the AIFL, IL, and anterior deltoid ligament causing possible joint instability
(9,20,37,38,39). Grade 3 injuries are associated with disruption of the AIFL, IL, anterior
deltoid ligament, which could be associated with several fractures (9,20,37,38,39).
Research suggests acute injuries are less than four weeks while chronic injuries persist
more than three months (9).
Treatment
Treatment of syndesmosis injures can vary and are based on the length of symptoms
and severity of the injury (4,7,8,9,10,20,33). Protocols can consist of conservative
treatment or operative treatment depending on the patient’s goals, and recommendations
of medical personnel. Grade 1 injuries, non-fractures, and possibly Grade 2 injuries can
be treated with conservative treatment (4,7,8,9,10,20,33). Grade III injuries typically
require operative treatment to restore mobility (4,8,7,9,10, 20,33).
Conservative Rehabilitation Protocols
Rehabilitation results can vary from patient to patient, but usually range from 2-4
weeks for Grade 1 sprains, and 6-8 weeks for Grade 2 sprains (4,7,8,9,10). The goals of
phase I are to reduce pain, reduce inflammation, reduce scaring, protect the injury,
increase range of motion and maintain cardiovascular fitness (4,7,8,9,10,20,33).
Phase I of the rehabilitation typically begins 0-5 days for Grade 1 sprains and 5-10
days for Grade 2 sprains (1,4,7,8,9,10). Immobilization can range from 0-5 days for
Grade 1 sprains and 6-8 weeks for Grade 2 sprains (1,4,7,8,9,10,20). Immobilization
techniques include splinting, casting, cam-walkers, and crutches (1,4,7,8,9,10,20).
Researchers recommend non-thermal ultrasound, cryotherapy, and electric-stimulation to
manage pain and swelling (1,4,7,8,9,10,20). Manual exercises consisting of 30*degrees
of plantar flexion, light passive stretches, dorsiflexion towel stretches, ankle pumps and
toe curls are recommended to increase range of motion, and reduce inflammation (4,8).
Phase II of the rehabilitation could range from 6-10 days for Grade 1 sprains and up
to 2-8 weeks for Grade 2 sprains (1,433,40,41). The goals of phase II are progression to a
full range of motion, injury protection, pain reduction, increase proprioception, increase
strength, functional activity, progression to pre-injury levels, and maintaining
cardiovascular fitness (1,4,7,8,10,20,33). For example, balance pads, toe raises, single leg
raises, baps boards, resistance bands, manual resistance, joint mobilization, cycle
ergometer, and light sports specific exercises are recommend during this stage of the
rehabilitation (1,4,7,8,10,20,33). Bracing, ultrasound, cryotherapy, stretching and other
modalities are recommended during this stage of the rehabilitation (7,8).
Phase III of the rehabilitation can range from 18-25 days depending on the severity of
the injury (1,33). The goals are to reduce pain, increase pain free activity, increase
strength, proprioception, advance sport specific activities, and maintain cardiovascular
fitness (1,4,7,8,10,33). Researchers recommend using a single leg hop test to determine if
the patient is able to perform advance sports specific activities (8). Rehabilitation
exercises can include shuttle runs, advanced single leg exercises, figure eight drills, cycle,
advanced sports specific activities, and high intensity cardiovascular training using
stirrup bracing for protection (1,4,8,9,10,18,20,33). Researchers indicate full return to
play when patients can demonstrate full strength, full range of motion and can pass all
functional testing (8,20,38).
Phase IV of the rehabilitation can range from 28-56 days depending on the severity of
the grade II injury (10,33,40,41). Rehabilitation exercises can include dumbbell squats,
lunges, figure eight drills, advanced sports specific activities, and Phase III exercises
(4,33,40,41). Full return to play can range from 6-8 weeks depending on the patients
ability to demonstrate full strength, full range of motion and pass all functional tests (10).
Operative Treatment
Arthroscopy can be used for patients with acute or chronic disruptions (4,7,8,9,10,
20,33). Operative treatment is indicated for Grade 2 and Grade 3 injuries, which can
cause instability and leave the patient at risk for further injuries (4,7,8,9,10, 20,33). The
goals for surgical intervention are to restore disrupted structures thru reduction, fixations,
and autographs (1,4,9,10,33). Rehabilitation goals consist of protecting the surgical
repair, reduce pain, reducing inflammation, restoring range of motion, proprioception,
and strength to pre-injury levels (1,4,9,10,33).
Open Reduction and Internal Fixations
Open reduction and internal fixation techniques can be used to restore unstable
fractures, tibiofibular clearance space, with emphasis placed on the integrity of structural
ligaments (9,10). Researchers recommend four 4.5mm cortical screws if a fracture
occurs to the fibula, medial malleolus, or displacement of the fibula and mortise.
(9,10,42,43). Research indicates using a modified brostrum procedure to repair the
deltoid ligament if disruption occurs (9,27). The semitendinosus, gracilis and plantaris
could be used as autographs to restore the integrity of disrupted ligaments (9,27).
Complications associated with the procedure include screw breakage, types of screws,
wound infections, interosseous membrane calcification, and stiffness within the joint
(9,10).
Post-Operative Rehabilitation Protocols
Post-operative rehabilitation results can vary from patient to patient, but usually range
from 4-8 months for a full return to play (9,18). Research suggests that follow up
radiographs be performed every two weeks to assess the integrity of the surgical repair
(10). The goals of phase I are to reduce pain, reduce inflammation, protect the surgical
repair, and increase range of motion (9).
Phase I of the rehabilitation begins with immobilization of the injury using splinting,
cam-walkers, casting and crutches for 6-8 weeks (7,9,10). None weight bearing, crutches,
home stretching programs, and cryotherapy are recommended during the first week of
rehabilitation (9). Manual exercises performed during phase I of conservative treatment
can be used during this stage of the rehabilitation (4,8,9).
Phase II of the rehabilitation can begin at three to six weeks. The patient can begin
partial weight bearing using one crutch and a cam-walker at 3-6 weeks (9,18). The goals
are to reduce pain, increase pain free activities, increase strength, proprioception, and
maintain cardiovascular fitness (9). Rehabilitation exercises can include baps board,
resistance bands, stationary bikes, gait training and manual exercises performed during
phase I of the conservative rehabilitation protocol (9). Research indicates that patients
should progress from stationary bike to the elliptical at six weeks (9).
Phase III is when patients are allowed full weight bearing using a cam-walker at eight
to twelve weeks (4,9,18,44). Patients can progress to functional activities including
running, and exercises used during phase II of the conservative rehabilitation (9). Screw
fixations are typically removed at 3 months, and patients should continue a progression in
full weight bearing activities (9,18).
Phase IV of the rehabilitation can begin at four to eight months, and typically return
to full participation is at 6-8 months (9,18). Patients should perform exercises using phase
III and phase IV of the conservative rehabilitation protocol and progress as tolerated
using bracing up to the first year post injury (9,18,33,40,41,43). Patients should
successfully perform strength, range of motion, and functional tests before full
participation is granted. (8,20,37).
Conclusion
Syndesmosis injuries can be more challenging to recognize and manage when
compared to lateral ankle sprains (1,3,4,6,7,8,9). It is important for clinicians to recognize
the extent of injury and rule out associated injuries using clinical examinations, imaging
techniques, and surgical intervention to successfully manage syndesmosis injuries.
Further research is warranted in regards to imaging reliability, clinical tests reliability,
predicting time loss, predicting the extent of injury and the effectiveness of surgical
techniques to effectively manage syndesmosis injuries (4,8,9,10,18,20). Furthermore,
research is warranted to effectively develop a standard rehabilitation protocol to properly
manage this condition.
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