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i31

Pictorial .:

.

MR Imaging Scott

J. Erickson,1

of the Lateral

Judith

Jeffrey E. Johnson,2

The ankle is stabilized by collateral (deltoid) ligament, plex, and the lateral collateral collateral ligament is the one Assessment

of the extent

W. Smith,2’3

Michael

Mario

Collateral

E. Ruiz,1

Steven

has classically

relied

on clinical

evaluation; plain film radiographs (including stress views); and, in some acute situations, ankle arthrography and/or peroneal tenography. In this report we illustrate the use of MR in the evaluation of the lateral collateral ligament. The normal anatomy, pitfalls

in image

interpretation,

and

W. Fitzgerald,1’4

J. Bruce

I

;

of the Ankle Kneeland,1’5

J. Shereff,2 and G. F. Carrera1

three sets of ligaments: the medial the syndesmotic ligamentous comligament. Of these three, the lateral most often injured in ankle sprains.

of injury

Ligament

Essay

findings

in cases

axial, sagittal, coronal, and oblique axial images. In patients, the scanning plane varied depending on the specific clinical indication. Normal anatomic images were selected from both normal subjects and also from patients without signs or symptoms of ligamentous injury in whom studies were performed for other clinical indications. The normal images were compared with corresponding cryomicrotome sections and with standard anatomic texts [1 -3]. Cases of ligamentous injury were correlated with surgical findings.

of ligamen-

tous injury are demonstrated.

Subjects

and Methods

We performed MR imaging in two normal subjects and also reviewed the MR examinations of over 50 patients with various types of ankle abnormalities. The scans were obtained on a 1 .5-T Signa MR unit (General Electric Medical Systems, Milwaukee, WI) in conjunction with the extremity coil provided with the system or a specialized saddle configuration coil. Ti -weighted images were obtained with 500/20 (TR/TE), a 256 x 256 acquisition matrix, a 1 0- to 1 2-cm field of view, and two excitations. T2-weighted images were obtained with 2500/20,80, a 256 x 1 92 acquisition matrix, a 1 2-cm field of view, and one excitation. In all cases, the slice thickness was 3 mm. For Ti-weighted images, we either obtained contiguous slices or used a 1 -mm interslice gap. For T2-weighted images, a 1 -mm interslice gap was used routinely. In the normal subjects we obtained

Fig. 1.-Drawing collateral ligament.

of lateral aspect See abbreviation

of ankle shows components key on page 132.

of lateral

Received June 14, 1990; accepted after revision August 9, 1990. Presented as an exhibit at the annual meeting of the American Roentgen Ray Society, Washington, DC, May 1990. I Department of Radiology, Medical College of Milwaukee, Milwaukee County Medical Complex, 8700 W. Wisconsin Ave., Milwaukee, WI 53226. Address reprint requests to S. J. Erickson. 2 Department of Orthopaedic Surgery. Medical College of Wisconsin, Milwaukee, WI 53226. 3 Present address: Department of Orthopaedic Surgery, Emory Lkiversity, Atlanta, GA 30322. 4 Present address: Department of Radiology, Northwestern MemOrial Hospital, Northwestern University Medical School, Chicago, IL 6001 1. S Present address: Department of Radiology, Hospital of the University of Pennsylvania, Philadelphia, PA 19104. AJR 156:131-136,

January

1991 0361-803x/91/1561-0131

C American

Roentgen

Ray Society

132

ERICKSON

ET AL.

Normal

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Key to Abbreviations

and Symbols

anterior

atif c cf f pbt pIt ptaf ptif sn spr ta

anterior tibiofibular ligament calcaneus calcaneofibular ligament fibula peroneus brevis tendon peroneus longus tendon posterior talofibular ligament posterior tibiofibular ligament sural nerve superior peroneal retinaculum talus tibia malleolar fossa

open arrows

January 1991

Anatomy

Used in Figures

ataf

ti

talofibular

AJA:156,

The

ligament

lateral

collateral

ligament

of the

ankle

includes

ligaments

are approximately

in the same

plane,

the anterior

talofibular ligament extending from the anterior aspect of the fibula to the lateral talar neck, and the posterior taloflbular ligament from the distal aspect of the malleolar fossa to the lateral tubercle of the posterior talar process (Figs. 2 and 3). The anterior talofibular ligament is actually located within the anterior joint capsule, analogous to the anterior glenohumeral ligaments of the shoulder. While the anterior ment appears homogeneously hypointense

quences,

the posterior

homogeneous,

similar

talofibular

ligament

to the anterior

talofibular ligaon all MR se-

often appears

cruciate

ligament

!

Fig 2.-Normal

anterior

talofibular

ligament,

axial plane. See abbreviation

4

key on this page.

A, Cryomicrotome section. B, Ti-weighted image, 500/20. C, T2-weighted image, 2500/80.

:

ta

the

following structures: the anterior talofibular ligament, the postenor talofibular ligament, and the calcaneofibular ligament (Fig. i). With the ankle in neutral position, the two talofibular

I ,

H p

A

Fig. 3-Normal posterior talofibular ligament, axial plane. See abbreviation A, Cryomicrotome section. B, Ti-weighted image, 500/20. C, T2-weighted image, 2500/80. Note fluid within joint (arrowheads).

key on this page.

V

in-

of the

AJA:156, January 1991

MR

Fig. 4.-Normalcalcaneofibularligament.

OF

LATERAL

COLLATERAL

LIGAMENT

OF ANKLE

i33

See

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abbreviation key on page 132. A, Coronal spin-density image, 2500/20. B, Axial Ti-weighted image, 500/20.

Fig. 5.-Normal calcaneofibular ligament. See abbreviation A, Cryomicrotome section. B, Sagittal localizer demonstrates oblique axial plane. C, Oblique axial Ti-weighted image, 500/20, shows entire

key on page

course

132.

of calcaneofibular

ligament

(arrowheads).

knee (Fig. 3C). These two ligaments are best demonstrated in the axial plane, although with experience they may be identified in either the coronal or sagittal plane. The calcaneofibular ligament courses deep to the peroneus brevis and peroneus longus tendons, extending from the tip of the lateral malleolus to a small tubercle on the lateral aspect of the calcaneus. This ligament is often seen in part on either coronal or axial images (Fig. 4), but is best identified by using an oblique axial scanning plane (Fig. 5), or by scanning in the axial plane with the foot in plantar flexion [4].

Pitfalls Fig. 6.-Drawing See abbreviation

of lateral aspect key on page 132.

of ankle

shows

tibiofibular

ligaments.

in MR Image

The talofibular adjacent anterior

Interpretation

ligaments can be easily and posterior tibiofibular

confused ligaments

with the on MR

ERICKSON

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134

Fig. 7.-Normal

tibiofibular

ligaments,

A, Cryomicrotome section. B, Corresponding Ti-weighted C, Ti-weighted image, 500/20,

Fig. 8.-Distinction

of talofibular

axial plane. See abbreviation

image, 500/20. obtained at level of ankle

from tibiofibular

AJR:156, January 1991

key on page 132.

joint, slightiy

ligaments,

ET AL.

superior

to B.

coronal plane. See abbreviation

key on page 132.

A, Cryomicrotome section. B, Spin-density image, 2500/20. C, T2-weighted image, 2500/80.

images (Fig. 6). The latter course obliquely from the anterior and posterior aspects of the distal tibia to insert onto the anterior and posterior aspects of the fibula (Fig. 7). The fibular sites of attachment are superior to the attachments of the talofibular ligaments, that is, above the level of the malleolar

ments. These structures are difficult to demonstrate with MR and should not cause diagnostic confusion. The normal talofibular ligaments may be mistaken for abnormal conditions, particularly in the sagittal plane. For ex-

fossa (Fig. 8). The configuration of the fibula, therefore, can be used to distinguish the tibiofibular from the talofibular

ies (Fig. 9). Such tures on adjacent

ligaments on axial images. The inferior transverse ligament and the tibial slip of the posterior talofibular ligaments are diminutive structures situ-

Ligamentous

ated between

the posterior

talofibular

and tibiofibular

liga-

ample, these hypointense

The

errors slices

structures

can simulate

can be avoided by tracing to their sites of attachment.

loose bodthe struc-

Injury

lateral collateral inversion stress. The

ligament is commonly weak anterior talofibular

injured with ligament is

AJR:156,

MR

January 1991

OF

LATERAL

COLLATERAL

LIGAMENT

OF

ANKLE

135

Fig. 9.-Posterior talofibular and tibiofibular ligaments mimicking loose bodies, sagittal plane. See abbreviation key on page i32. A, Cryomicrotome B, Corresponding

section.

spin-density

image,

2500/

20.

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C, Spin-density D, T2-weighted

Image, image,

2500/20, 2500/80,

lateral to B. at same level

as C.

-,

..

.

-----

‘,

. .,

D

Fig. 10.-Anterior talofibular ligament See abbreviation key on page 132. A, Axial spin-density image, 2500/20,

injury. shows

ligamentous discontinuity (arrowheads). B, lntraoperative image shows torn ligament (marked by sutures).

ends

usually injured fibular ligament

may show the anterior tablax, or discontinuous (Figs.

first. MR imaging to be attenuated,

of

i 0 and 1 i). In acute cases, there may be accompanying

high

signal

(Fig.

intensity

within

the joint

or adjacent

soft tissues

1 1). In one chronic case, a “mass” probably representing organizing hematoma was identified (Fig. i 2). The calcaneofibular ligament may be injured with more severe inversion stress, and is almost always associated with

ERICKSON

136

ET AL.

AJA:156, January 1991

Fig. 1 1.-Acute anterior talofibular ligament injury. See abbreviation key on page 132. (Case courtesy of S. F. Quinn, Portland, OR.)

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A, Axial spin-density image, 2500/20, shows torn end of ligament (solid arrow). B, Axial T2-weighted image, 2500/80, shows torn end of ligament (solid arrow) with adjacent fluid (arrowheads).

‘

Fig. 12.-Anterior key on page 132.

talofibular

ligament

injury with probable

organizing

A, Axial Ti-weighted image, 500/20, shows absent ligament B, Coronal T2-weighted image, 2500/80, shows predominantly

an anterior

talofibular

injury. MR imaging

hematoma.

and hypointense hypointense

may show attenua-

tion or abnormal thickening ofthe ligament (Fig. i 3). Anatomic variability in the configuration of the ligament, combined with relative difficulty in identification, may make assessment of injury a diagnostic challenge.

Posterior

talofibular

ligament

almost always associated tabofibular and calcaneofibular

injury

with injury ligaments.

is uncommon, to both

the

and is anterior

See abbreviation hematoma (arrows).

hematoma

(arrows).

Fig. 13.-Calcaneofibular ligament Oblique axial Ti-weighted image, 500/20, abnormal thickening of ligament (arrows). breviation key on page 132.

injury. shows See ab-

REFERENCES 1 . Netter FH. The Ciba collection of medical illustrations, vol. 8. Musculoskeletal system, part I. Anatomy, physiology and metabolic disorders. Summit, NJ: Ciba-Geigy, 1987 2. Anderson JE. Grant’s atlas of anatomy, 7th ed. Baltimore: Williams & Wilkins, 1978 3. Williams PL, Warwick A, Dyson M, Bannister LH. Gray’s anatomy, 37th ed. Edinburgh: Churchill Livingstone, 1989 4. Rijke AM. Acute ankle sprains: What is the role of the radiologist? AppI Radiol i989;i8:11-16