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ANKLE: LATERAL SPRAINS
Arie M. Rijke1Frank C. McCue III
Andrew M. Schuett2
1 Department of Radiology2Department of Orthopedics
University of Virginia Health Sciences CenterCharlottesville, VA 22908
Ankle injuries make up a large proportion of injuries in
sports. Primary care and emergency departments report as many
as 10% of presentations to involve the ankle joint. The vast
majority of these are sprains. Eighty - five percent of ankle
sprains occur on the lateral side. These sprains are caused
by inversion of the foot with external rotation of the lower
leg on the fixed foot. As such they are most frequently seen
in sports that involve running and jumping such as basketball,
volleyball and football. There is no predisposition for age
or sex, but systematically trained and supervised athletes are
less likely to sustain a lateral sprain than amateur or
weekend athletes.
The most important ligaments involved in a lateral ankle
sprain are the anterior talo-fibular ligament and the
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calcaneofibular ligament. Less important is the posterior
talofibular ligament that stabilizes against posterior
displacement of the talus and is usually spared in the milder
forms of lateral sprains. However, isolated ruptures of this
ligament have been occasionally found at surgery and on
magnetic resonance imaging (MRI) scanning.
It is preferable to grade lateral ankle sprains according
to the ligaments involved in the trauma rather than the
severity of their clinical presentation:
• Grade 1, partial tear of the anterior talofibular
ligament with intact calcaneofibular ligament.
• Grade 2, complete rupture of the anterior
talofibular ligament with intact
calcaneofibular ligament.
• Grade 3, complete rupture of the anterior
talofibular ligament and partially torn
calcaneofibular ligament.
• Grade 4, both ligaments are completely torn.
Isolated tears of the calcaneofibular ligament have been
reported to occur in 3% of sprains and are specifically
associated with hyperdorsiflexion, but no isolated tears were
encountered in studies of several hundred patients with
lateral ligament injury.
There is no consensus on how to treat acute sprains in
spite of their common occurrence and the large number of
comparative studies. Many surgeons manage these patients
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conservatively with elastic bandages, a cast, a pneumatic
brace, or simple immobilization of the foot, with satisfactory
results in most cases. Early mobilization has been beneficial
for early return to activity, because range-of-joint motion
may stimulate healing of the torn ligaments. Nevertheless, 20%
to 40% of conservatively treated patients seek further medical
attention for residual symptoms. These may include pain and
swelling, or a sense of instability when walking on uneven
ground. When conservative management fails, reconstruction of
the lateral ligaments eliminates disabling symptoms and
restores good function in a high percentage of ankles.
However, there is reason to believe that surgical repair of
acutely injured ligaments has a higher success rate than any
reconstructive method for old ruptures.
There is no question about the success of surgical
treatment of acute lateral ligament tears. Various authorities
have reported excellent results in as many as 97% of sprains
and, for this reason, surgery is the treatment of choice in
some centers, particularly in Europe. However, these results
have to be balanced against the 70% satisfactory results with
casting, bracing, and taping, as originally reported by
Broström in 1966. Since then, the pneumatic brace has become
available, and aggressive rehabilitation programs have proved
their value. We must consider, therefore, whether a surgical
procedure is justified to achieve an additional 27% (or less)
increase in satisfactory results. This is why some surgeons
only operate on severe sprains in highly competitive athletes
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who are eager to return to sports participation, or on a
patient's specific request. Although such a selection of
patients seems reasonable, the significant number of
conservatively treated patients with persisting symptoms
suggests that many lateral ligament lesions are either
incompletely diagnosed or inadequately managed or both.
Diagnosis
History and physical examination relate to an experience
of a sudden, sharp pain on impact followed by inability to
support weight and the rapid development of an egg - shaped
soft tissue swelling over the lateral anterior aspect of the
ankle joint. Frequently the patient cannot detail the exact
course of events that led to the sprain. Icing and an ace
bandage provide some relief and support. Later, discoloration
of the skin occurs in the more severe cases.
A careful physical examination is indispensable in the
diagnosis of lateral sprains, but it cannot assess the
separate involvement of individual ligaments. Because the
prognosis for conservatively treated ankle sprains is largely
determined by the extent of ligament injury, an early and
complete analysis is needed to decide on the treatment of
choice. Plain x-rays of the ankle-including anteroposterior,
lateral, and oblique views to rule out fractures and
dislocations-should be searched for avulsion fractures of the
tip of the distal fibula, the talus, and the medial malleolus.
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These x-rays should also be examined for evidence of joint
fluid and soft-tissue swelling over the lateral malleolus,
which may indicate lateral ligament injury. Physical
examination should also include an anterior drawer test. If
there is any question about the translation in that
compartment, further work-up is indicated.
Ideally, an examination of the sprained ankle would
provide information on which ligaments are torn and correlate
the resulting anatomic derangement with loss of ankle
stability. A dynamic test that quantifies the loss of
functional support in terms of ligament injury is required.
Follow-up examinations should use the same parameters to
monitor therapeutic results. In actual practice, few
controlled studies have been performed that fulfill these
needs. In a typical study, the efficacy of the various modes
of treatment is evaluated by relating history and physical
examination scores at follow-up to the diagnostic findings
based only on indirect signs at the time of trauma.
Arthrography
Ankle arthrography has been used by many investigators to
determine the extent of ligament damage. Here, capsular
extravasation of contrast and leakage anterior to, around, and
lateral to the distal fibula are read as indications of
rupture of the anterior talofibular ligament. If simultaneous
filling of the peroneal tendon sheath occurs, the
calcaneofibular ligament is assumed to be ruptured as well.
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The validity of ankle arthrography is based on the intimate
relationship between the anterior talofibular ligament and the
ankle capsule. In fact, the ligament is often seen at surgery
as a thickening of the anterolateral aspect of the capsule.
Parallel tracts of contrast medium into the peroneal tendon
sheath indicate calcaneofibular ligament injury and are a
result of the close anatomic relationship between this
ligament and the tendons of the peroneus longus and brevis.
Apparently, rupture of the extracapsular calcaneofibular
ligament produces a communication between the joint space the
peroneal tendon sheath. Not unexpectedly, occasional false-
negative results have been obtained because the ligament
ruptured while leaving the peroneal sheath intact. Also,
naturally occurring communications between the peroneal sheath
and the joint space in the presence of an intact
calcaneofibular ligament have been reported in both cadaver
and clinical studies, leading to false-positive results.
Despite these shortcomings, arthrography is extremely
accurate in diagnosing ligament rupture in the acute rupture-
that is, when performed within 72 hours of trauma; it is
unreliable if the examination is further delayed. This is due
to the formation of blood clots and fibrin that eventually
close off the communication between the joint space and the
peroneal space. Arthrography has no role in follow-up
examinations and in the evaluation of chronic ankle
instability.
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Stress Radiography
Stress examinations are regarded as standard noninvasive
procedures in the diagnostic analysis of acute ankle sprains.
The examination procedure is simple and straightforward. An
inversion force is applied to the lateral dorsal part of the
foot while keeping the lower leg fixed. This separates the
articular surfaces of the tibia and talus with an angle
opening laterally on the anterior posterior view; this is
referred to as the talar tilt angle. Alternatively, a force
can be applied to the anterior aspect of the distal tibia with
the heel remaining fixed. Viewed in the lateral projection a
resulting displacement called the anterior drawer, can be
observed. The stress can be applied manually or mechanically.
Mechanical devices have the obvious advantage that the applied
force can be quantified and examiner-to-examiner variability
can be eliminated. Local anesthesia may be needed to ensure
the patient's cooperation and to prevent muscle splinting.
Because the measured talar tilt angle and anterior drawer
result from a discrete force, instrumented stress examination
provides, at least in principle, a basis for making
distinction among different grades of ligament injury.
However, the ranges of talar tilt angles and anterior drawers
that represent low or high grade lesions have been the subject
of much controversy, largely as a result of the extensive
overlap of ranges for normal and abnormal ankles. This
overlap can be significantly reduced if patients with a
history of ligament trauma to the opposite ankle (which
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routinely serves as normal comparison) can be excluded. In
some studies, as many as 35% of patients had a positive
history on the opposite ankle. Nonetheless, there remain
serious difficulties when trying to differentiate low from
high grade lesions and selection of patients for conservative
or surgical treatment on the basis of these findings alone
remains controversial.
It has also been shown that the average talar tilt angle
of the opposite ankle increases with the extent of ligament
damage to the injured ankle. A predisposition for ankle
sprains in patients with preexisting ligament instability
probably explains this finding. Other studies also seem to
point this out. Sanders has shown that the average talar tilt
angle of normal volunteer subjects is lower than that of the
opposite ankles of patients with ankle sprains. It is
unlikely, however, that preexisting ligament laxity is the
single most important factor in causing ligament injury.
Activities that involve running and jumping, such as basket
ball and football, predispose individuals to repeated sprains
far beyond the relatively low prevalence of true laxity
disease, such as Marfan syndrome and Ehlers-Danlos syndrome.
This is evidenced by the high percentage of often-forgotten
sprains of the opposite ankle.
Graded Stress Radiography
Recently, a graded stress technique has been developed
that makes it possible to distinguish the different grades of
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ligament lesions. Any stress device that combines proper
positioning of the foot with the capability to monitor the
applied pressure, thus permitting consistent and reproducible
measurements of the talar tilt angle and the anterior drawer,
can be used for this purpose (Fig. 1). The stress is
increased gradually and anterior posterior x-rays are taken
after application of increasing pressures (Fig. 2 a, b).
To assess the extent of injury to the individual
ligaments the applied pressure (or force) is plotted against
( -1/2), where represents the ratio between the lengths of
the stretched and unstretched lateral ligaments. According to
viscoelastic theory the pressure P = G( -1/2), where the
proportionality factor G is related to the cross-sectional
area of the unstretched ligaments and to their shear modulus.
Figures 3a and b show such plots for grade 2 and grade 4
lesions, respectively. Note that the applied pressure in
kiloPascals is plotted against linear increments of (-1/2)
on the lower x-axis. The corresponding talar tilt angles from
which (-1/2) has been calculated, are plotted on the upper
x-axis in non-linear increments. Using this type of
preprinted graphical arrangement makes it unnecessary to
perform multiple calculations from the observed talar tilt
angles.
Using the above method of graphical plotting, intact
ligaments show as a straight line going through the origin,
with a slope in the range of 16 to approximately 40 kPa
reflecting the anatomic variation among patients. An isolated
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anterior talofibular injury will reduce the slope proportional
to the extent of injury and allow an estimate, at least in
principle, of the percentage of rupture of the ligament by
comparing it with the findings on the intact ligaments of the
opposite ankle. A grade 2 lesion shows the slope as 50% of
normal, whereas a grade 3 lesion reduces the slope even
further. A grade 4 lesion, on the other hand, is represented
by a straight or curved relationship that does not go through
the origin.
The validity of these concepts have been tested on nine
cadaver ankles and one freshly amputated lower leg. The
accuracy of this method has been further verified in 24
surgically treated patients. Similar results are obtained
when evaluating the anterior drawer, but we prefer the talar
tilt examination because this procedure is simpler and
requires no correction for photographic magnification.
By accurately assessing the extent of ligament
involvement, graded stress radiography has proved to be a
powerful tool in grading lateral ligament injury and has
therefore helped in deciding between conservative or surgical
treatment. The examination, including the graph evaluation,
can be completed in 15 minutes. Unlike arthrography, graded
stress radiography can supply diagnostic information
independent of the time of injury and is therefore
particularly well suited for follow-up studies and for the
evaluation of chronic ankle instability. Because the same
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parameters are measured at the time of injury and at follow-
up, the data can be directly compared.
We have applied this technique to 36 athletes with acute
and nonacute lateral ankle injuries who were reexamined 11/2 to
5 years after treatment. Of the surgically treated patients
with grade 4 lesions, 83% showed 70% to 100% recovery of
ligament function compared with 21% of patients treated
conservatively with a short leg case, elastic bandages, a
brace, crutches, high-top shoes, or a combination of these.
If we assume that optimal management of conservatively treated
grade 1,2 or 3 lesions results in a recovery rate of nearly
100%, we can calculate (based on the above figures and the
observed 2:1 prevalence of low-grade lesions over high-grade
lesions) that conservative treatment for all patients,
regardless of their grade of injury, would result in a 73%
success rate. This figure is close to Broström's estimate of
70% and correlates well with the 20% to 40% of conservatively
treated patients who seek further medical attention for
persisting symptoms.
These results underscore the importance of the diagnostic
distinction between grade 1,2 and 3 lesions on one hand, and a
grade 4 lesion on the other. They also emphasize the
importance of modern, aggressive methods of nonoperative
treatment and rehabilitation. Patients with grade 4 lesion,
particularly competitive athletes, should be further screened
for possible surgery.
MRI
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MRI scanners are now fairly widely available in the
larger institutions. Because of its capability of
demonstrating soft tissue detail, the potential of MRI in
detecting lateral ankle ligament injury has been recently
explored. The anterior and posterior talofibular ligaments
can be adequately demonstrated on axial scans with the foot in
neutral position. The calcaneofibular ligament can be best
seen in plantar flexed position. Acute tears are usually not
directly visualized in the presence of hemorrhage and edema,
but in the subacute or chronic stage disruption and fraying of
the injured ligaments can be identified. Occasionally, a wavy
course of the ruptured calcaneofibular ligament can be seen
associated with a grade 3 or 4 injury (Fig. 4). Atrophy of the
ligament may show as a nubbin at its site of attachment.
The role of MRI in the detection of lateral ankle sprains
is limited. Assessment of anatomical damage is restricted to
the subacute and chronic stages only, and unlike the cost-
effective graded stress radiography, does not correlate with
the observed ankle instability.
Treatment
The ultimate goals in the treatment of ligament injuries
are to obtain rapid and complete rehabilitation with minimal
morbidity and cost. The method chosen should also insure the
lowest possible risks for chronic late instability patterns.
Basically, the choice is between some form of conservative
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treatment and some type of surgical procedure. The current
trend favors individualized activity and sports-specific
proprioceptive training program as part of a non-surgical
rehabilitation, whereas surgery is reserved for severe sprains
in highly competitive athletes eager to return to sports
participation, and for those athletes who have failed to
respond to individualized conservative treatment. Late
reconstructive attempts are, however, no more successful than
acute repair. The need for these late reconstructions will
decrease with accurate diagnosis at the time of injury and
proper choice of management.
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Conservative Approach
Acute, conservative management of the lateral ankle
ligament injury should include ice, elevation, compression and
stabilization. Initial goals include minimizing the secondary
hypoxic injury caused by decreased oxygen delivery to the
region. Many authors have stated, however, that optimal non-
operative management of lateral ankle sprains has not been
established.
• Grade 1 injuries may be associated with minor
tenderness and swelling with the patient able to
functionally bear weight. With increased
activity, or return to play, this population
becomes symptomatic and has a high risk of re-
injury. This risk is greater with immediate
return, and the individual must be protected with
some sort of ankle support.
• Grade 2 injures can be defined as moderate, with
significant swelling and tenderness. They can walk
with difficulty but are unable to re-initiate peak
levels of activity.
Grade 3 and 4 injuries are defined as severe, with
significant pain and tenderness. The inability to
bear weight without rigid immobilization or
crutches is usually associated with a complete
tear of the anterior talofibular and partial or
complete tear of the calcaneofibular ligament.
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Immediate treatment for all injuries should include
symptom relief and protection from further injury. Grading
these injuries via physical examination in the acute period is
difficult to perform especially in the moderate and severely
involved cases. Treatment of the acute grades 2,3, or 4
sprains should involve placement of a well padded posterior
splint made of plastic with or without a stirrup support.
Rest, ice compression and elevation should be mandatory over
the first two to three days. At this time, the injury should
be reassessed. If swelling has decreased adequately, the
stirrup splint should be replaced with a pneumatic type brace
placed over the TED hose or Ace bandage. Gradually, increases
in weight bearing are permitted until the crutches are no
longer necessary. At this time, the patient is placed in a
Swedo-type brace or lace-up ankle support and encouraged to
begin weight bearing as tolerated. Beyond day 10 post-injury,
flexibility, strengthening and proprioceptive exercise should
be started. Many different post-injury rehabilitative
regimens have been reported in the literature.
The noncompliant patient with a severe grade 4 injury
represents a treatment challenge. Casting should be considered
initially but must be weighed against numerous factors
including initial swelling and likelihood of follow-up.
Alternative forms of immobilization must be considered, if
possible, unless rigid external support offers the only
solution to disability and pain. The short-leg cast should be
non-weight bearing when placed after initial swelling
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decreases. It should remain in place one to three weeks,
followed by a weight bearing short-leg cast. Close follow-up
and removal every 10 to 14 days should be attempted. When the
patient can bear full weight on the injured extremity with the
cast on, it is removed and functional bracing can be started.
Surgical Options
Surgical treatment of an acute injury may be appropriate
in highly competitive athletes or when the injury is
recurrent, a large bony avulsion is present or when
ipsilateral injury makes traditional methods impractical.
Primary repair essentially consists of an anastomosis of
ruptured ligaments ends or re-attachment of a ligament that is
avulsed off its bony attachment. Following surgery a short-leg
cast is fitted with three weeks non-weight bearing and
crutches. The next three weeks in a cast are partially weight
bearing. After six weeks, the patient begins stretching,
strengthening and proprioceptive exercises.
When non-operative measures have failed to return an
individual to an acceptable level of function, surgical
intervention should be considered. The Watson-Jones
reconstruction attempts to recreate stability through the
peroneus brevis tendon. The proximal aspect of the peroneus
brevis tendon is released at its musculotendinous junction and
sutured to the peroneus longus. The free distal aspect of the
tendon is placed through a fibular tunnel from posterior to
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anterior, then through a talar tunnel inferior to superior.
The tendon is sutured to itself with the ankle in an everted
and dorsiflexed posture. Post-operative immobilization and
are similar to the acute procedure.
Another frequently used technique is the Chrismann-Snook
procedure. Here, the peroneus brevis is split longitudinally
in half from its proximal musculotendinous attachment. Post-
operative immobilization and care are similar to the Watson-
Jones procedure. Other operative interventions are the Evans
procedure and the Karlsson reconstruction. These have similar
post-operative immobilization and functional rehabilitation
protocols.
Athroscopy of the ankle is used primarily in patients
with chronic ankle pain and instability. It provides a
potential diagnostic and therapeutic option prior to an open
reconstruction attempt. Its indications include debridement
of osteophytes, loose bodies, synovitis, adhesions and
osteochondritis dissecans of the talus.
Conclusions
Lateral ankle ligament injuries are very common in
athletes and need a complete diagnostic work-up to determine
the extent of ligament damage at the time of trauma. A
careful history and physical examination, including the
appropriate radiographic analysis are essential for a good
prognosis in conservatively managed sprains and serves to
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identify candidates for surgery. X-rays should be searched
for fractures and signs that may indicate ligament injury.
Anterolateral instability is an indication for further work-up
of the ligament trauma, either by arthrography in the acute
phase, or better, by graded stress radiography. The latter
method permits accurate grading of the injury in terms of
remaining ligament function and monitoring of functional
improvement at follow-up by comparison with previous
examinations.
Treatment options include vigorous non-operative
rehabilitation and surgery in highly competitive athletes and
patients with chronic functional instability and pain. Proper
patient selection is a priority as cost, morbidity and long-
tern results are not conclusive in surgical versus non-
surgical care. The often poor results seen with lateral
ligament injuries are probably due to inadequate conservative
treatment of underdiagnosed lesions, such as severe grade 4
lesions with wide separation of the ruptured ligament ends.
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References
1. Ahovuo J, E. Kaartinen, and P. Slätis. Diagnostic value of
stress radiography in lesions of the lateral ligaments of
the ankle. Acta Radiol 29:711-714, 1988.
2. Bergfeld, J.A., J.S. Cox, and D. Drez Jr: Symposium:
Management of acute ankle sprains. Contemp Orthop 13:, 1986.
3. Broström, L. Sprained ankles. V. Treatment and prognosis in
recent ligament ruptures. Acta Chir Scand 132:537-550,
1966..
4. Cox, J.S.: Surgical and non-surgical treatment of acute
ankle sprains. Clin. Orthop. 198:118-126, 1985.
5. Dunlop, M.G., T.F. Beattie, G.K. White, et al. Guidelines
for selective radiological assessment of inversion ankle
injuries. Br Med J (Clin Res) 293(6547):603-605, 1985.
6. Lassiter Jr., T.E., T.R. Malone, and W.E. Garrett Jr.
Injury to the lateral ligaments of the ankle. Orthop. Clin.
North Am. 20:629-640, 1989.
7. Prins, J.G.: Diagnosis and treatment of injury to the
lateral ligament of the ankle. Acta Chir Scan 486(suppl):1-
149, 1978.
8. Rijke AM: Lateral ankle sprains. Graded stress radiography
for accurate diagnosis. Phys. Sports Med.;19:107-118, 1991.
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LEGENDS
Fig. 1 - Telos stress device with patient's foot mounted for
measuring talar tilt angle.
Fig. 2a - Talar tilt angles at 6,9, 12, and 15 kPa of a 22
year old baseball player with a grade 1 ligament injury of the
left ankle, confirmed by arthrography. Talar tilt angles for
the left ankle range from 2° to 7°; for the normal right
ankle, from 1.2° to 3.5°.
Fig. 2b - Talar tilt angles at 6,9,12, and 15 kPa of a 28 year
old basketball player who sprained his left ankle. Talar tilt
angles for the left ankle range from 6.9° to 11.2°; for the
normal right ankle, from 1.5° to 3.7°. Surgery showed a grade
4 lesion.
Fig. 3a - Plot of applied pressure against talar tilt angle in
degrees on the upper x-axis and in linear increments against
(-1/2) on the lower x-axis, showing the grade 1 lesion of
the patient in Fig. 2a. From the difference in slope of the
lines, the lesion involving the left ankle can be calculated
to be a 40% tear.
Fig. 3b - Plot of applied pressure against talar tilt angle in
degrees on the upper x-axis and in linear increments against
(-1/2) on the lower x-axis, showing the grade 4 lesion of
the patient in Fig. 2b.
Fig. 4 - MRI of the right ankle of a patient with a subacute,
grade 4 lesion. The foot is in plantar flexion. Open arrows
point to wavy appearance of the disruptered calcaneofibular
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ligament. Curved arrow points to residual hemorrhage or
possibly granulation tissue medial to the distal fibula.
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