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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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