Ankle and Foot Show
The ankle is the most frequently injured of all the major weight-bearing joints in the body. Most victims are young adults injured while participating in athletic activities such as running, skiing, and soccer. Ankle structures susceptible to injury include bones, ligaments, tendons, and syndesmoses; ligaments can be damaged in the absence of fractures. When this occurs, damage to ligaments may go unrecognized on conventional radiographs, with the result that the patient is not properly treated. The type of fracture usually indicates the mechanism of injury determined, as Kleiger has pointed out, by the position of the foot, the direction and intensity of the applied force, and the resistance of the structures making up the joint. The mechanism of injury may in turn serve as an indicator of which ligament structures are damaged. Although occasionally meticulous history taking and clinical examination can help determine the mechanism of trauma and predict damage to the various structures, radiologic examination is the key to reliable evaluation of the site and extent of injury. There are two basic types of ankle trauma: inversion injuries and eversion injuries. These, however, may be complicated by internal or external rotation, hyperflexion or hyperextension, and vertical compression forces. Foot injuries are also common and usually result from direct trauma, such as a blow or a fall from a height; only rarely do such injuries result from indirect forces such as abnormal stress or strain of muscles or tendons. Foot fractures, accounting for 10% of all fractures, are more common than dislocations, which usually are associated with fractures, and occur at the midtarsal, tarsometatarsal, and metatarsophalangeal articulations. Anatomic-Radiologic Considerations The ankle joint proper consists of the tibiotalar and distal tibiofibular articulations, the latter a syndesmotic joint rather than a true synarthrodial one. In matters of injury, however, one must consider that the ankle joint acts as a unit with other joints of the foot, particularly the talocalcaneal (subtalar) articulation, where application of stress can have great impact on ankle injuries. The ankle joint is formed by three bones—the distal tibia and fibula and the talus—and three principal sets of ligaments—the medial collateral (deltoid) ligament; the lateral collateral ligament, consisting of the anterior talofibular, posterior talofibular, and calcaneofibular ligaments; and the syndesmotic complex, a fibrous joint between the distal tibia and the fibula (Fig. 10.1). The distal tibiofibular syndesmotic complex, one of the most important anatomic structures in maintaining ankle integrity and stability, consists of three elements: the distal anterior tibiofibular ligament, the distal posterior tibiofibular ligament, and the interosseous membrane. From the viewpoint of anatomy and kinetics, the foot is divided into three distinct sections: hindfoot, midfoot, and forefoot. The hindfoot, separated from the midfoot by the midtarsal (or Chopart) joint, includes the talus and calcaneus; the midfoot, separated from the forefoot by the tarsometatarsal (Lisfranc) joint, includes the navicular, cuboid, and three cuneiform bones; and the forefoot includes the metatarsals and phalanges (Fig. 10.2). The muscles attached to the tibia and fibula end in tendons proximal to or at the level of the ankle joint. These tendons insert into the foot (Fig. 10.3). A word about terminology is in order because the terminology describing motion of the ankle and foot in the literature is not uniform and confusion has been created about the various mechanisms of ankle and foot injuries. Frequently, but incorrectly, the terms adduction, inversion, varus, and supination have been used interchangeably, as have their counterparts abduction, eversion, valgus, and pronation. However, supination and pronation are more appropriately applied to compound motion. Supination consists of adduction and inversion of the forefoot (motion in the tarsometatarsal and midtarsal joints) and inversion of the heel, which assumes a varus configuration (motion in subtalar joint), as well as slight plantar flexion of the ankle (tibiotalar) joint. In pronation, compound motion consists of abduction and eversion of the forefoot (motion in the tarsometatarsal and midtarsal joints) and eversion of the heel, which assumes a valgus configuration (motion in the subtalar joint), together with slight dorsiflexion (or dorsal extension) of the ankle (Fig. 10.4). Adduction properly applies to medial deviation of the forefoot, and abduction to lateral deviation of the forefoot, both motions occurring in the tarsometatarsal (Lisfranc) joint; adduction of the heel refers to inversion of the calcaneus; and abduction of the heel refers to eversion of the calcaneus, both motions occurring in the subtalar joint. Plantar flexion refers to caudad (downward) foot motion, dorsiflexion to cephalad (upward) foot motion— motions occurring in the ankle (tibiotalar) joint. Varus and valgus should not be used to describe motion but should be reserved for the description of ankle or foot position in case of deformity. Occasionally, varus and valgus are used interchangeably with inversion and eversion to describe the applied stress. Imaging of the Ankle and Foot Ankle The standard radiographic examination of the ankle, as a rule, includes the anteroposterior (including the mortise), lateral, and oblique projections. Stress views are also frequently obtained for evaluating ankle injuries. These may also need to be supplemented with special projections.
On the anteroposterior view, the distal tibia and fibula, including the medial and lateral malleoli, are well demonstrated (Fig. 10.5). On this projection, it is important to note that the fibular (lateral) malleolus is longer than the tibial (medial) malleolus. This anatomic feature, important for maintaining ankle stability, is crucial for reconstruction of the fractured ankle joint. Even minimal displacement or shortening of the lateral malleolus allows lateral talar shift to occur and may cause incongruity in the ankle joint, possibly leading to posttraumatic arthritis. A variant of the anteroposterior projection, in which the ankle is internally rotated 10 degrees, is called the mortise view because the ankle mortise is well demonstrated on it (Fig. 10.6). The lateral view is used to evaluate the anterior aspect of the distal tibia and the posterior lip of this bone (the so-called third malleolus) (Fig. 10.7). Some fractures oriented in the coronal plane can be better visualized on this projection. Ankle joint effusion can also be assessed on this view (see Fig. 10.65). The oblique view of the ankle, best obtained with the foot internally rotated approximately 30 to 35 degrees, is effective in demonstrating the tibiofibular syndesmosis and the talofibular joint (Fig. 10.8). An external oblique view may also be required to evaluate the lateral malleolus and the anterior tibial tubercle (Fig. 10.9). Most ankle ligament injuries require stress radiography, ankle joint arthrography, computed tomography (CT), or magnetic resonance imaging (MRI) (see later) for demonstration and sufficient evaluation. Some, however, can be deduced from the site and extension of fractures on the standard radiographic examination. A thorough knowledge of the skeletal and soft-tissue topographic anatomy of the ankle, together with an understanding of the kinematics and mechanism of ankle injuries, will aid the radiologist in correctly diagnosing traumatic conditions and predicting ligament injuries. With such understanding, the radiologist can even determine the sequence of injury to the various structures. Some ligament injuries may be diagnosed on the basis of disruption of the ankle mortise and displacement of the talus; others can be deduced from the appearance of fractured bones. For example, fibular fracture above the level of the ankle joint indicates that the distal anterior tibiofibular ligament is torn. Fracture of the fibula above its anterior tubercle strongly
suggests that the tibiofibular syndesmosis is completely disrupted. Fracture of the fibula above the level of the ankle joint without accompanying fracture of the medial malleolus indicates rupture of the deltoid ligament. Transverse fracture of the medial malleolus indicates that the deltoid ligament is intact. High fracture of the fibula associated with a fracture of the medial malleolus or tear of the tibiofibular ligament, the
When radiographs of the ankle are normal, however, stress views are extremely important in evaluating ligament injuries (see Fig. 4.5). Inversion (adduction) and anterior-draw stress films are most frequently obtained; only rarely is an eversion (abduction)-stress examination required. On the inversion-stress film, obtained in the
anteroposterior projection, the degree of talar tilt can be measured by the angle formed by lines drawn along the tibial plafond and the dome of the talus (Fig. 10.10). This angle helps diagnose tears of the lateral collateral ligament. However, the wide range of normal values for these measurements may make interpretation difficult, and thus comparison studies of
the contralateral ankle should be obtained. Even this method is not always accurate; up to 25 degrees of talar tilt has been reported in people with no history of injury, and occasionally, there will be a patient whose ankles exhibit considerable variation in measurement. Many authorities advise that with forced inversion, tilt less than 5 degrees is normal,
The anterior-draw stress film, obtained in the lateral projection, provides a useful measurement for determining injury to the anterior talofibular ligament (Fig. 10.11). Values of up to 5 mm of separation between the talus and the distal tibia are considered normal; values between 5 and 10 mm may be normal or abnormal, and the opposite ankle should be stressed for comparison. Values above 10 mm always indicate abnormality. Ancillary imaging techniques are essential to the diagnosis and evaluation of many ankle injuries. CT may be required to determine the position of comminuted fragments in complex fractures, for example, of the distal tibia, talus, and calcaneus. Arthrography (Fig. 10.12) is occasionally used for assessing the integrity of the ligamentous structures in acute trauma, although recently, it has been almost completely supplanted by MRI. It is still, however, an effective technique for evaluating the articular cartilage and detecting and localizing loose osteocartilaginous bodies. It is also helpful in evaluation of chondral and osteochondral fractures and osteochondritis dissecans, which usually affects the dome of the talus. A singlecontrast study is usually performed to assess the integrity of the ankle ligaments. For evaluating the articular cartilage, a double-contrast study (combining a positive contrast agent and air) is more effective. Ankle tenography is a useful procedure for evaluating tendon tears, particularly tears of the Achilles tendon, peroneus longus and brevis, tibialis posterior, flexor digitorum longus, and flexor hallucis longus. According to Bleichrodt and colleagues, tenography particularly has proved to be reliable in the diagnosis of injuries of the calcaneofibular ligament, with a sensitivity of 88% and specificity of 87% to 94%. In a procedure similar to that for ankle arthrography, a 22-gauge needle is inserted into the tendon sheath, with the needle tip directed distally, and 15 to 20 mL of contrast medium is injected under fluoroscopic guidance. Radiographs are then obtained in the standard projections (Fig. 10.13). Tear is indicated by the extravasation of contrast agent from the tendon sheath, abrupt termination of the contrast-filled tendon sheath, or leak of contrast into the adjoining articulations (see Figs. 10.68, 10.69, and 10.70). Recently, this technique has been completely replaced by MRI (see Fig. 10.71). CT is an effective modality to evaluate various ligaments and tendons because the soft-tissue contrast resolution of CT allows the easy differentiation of these structures from surrounding fat. Specifically, tendon injuries including tendinitis, tenosynovitis, and rupture and dislocation of tendons can be effectively diagnosed. The major limitation in evaluating pathologic conditions of tendons with CT is the inability to scan the tendons in the coronal and sagittal planes. Reformation images, while occasionally helpful, suffer from the lack of spatial resolution and require additional examination time. For adequate CT of the ankle and foot, proper positioning of the leg in the gantry is essential. In addition, because nomenclature for imaging planes of the feet occasionally creates a problem, it is important to recognize that the coronal, sagittal, and axial planes of the ankle and foot are determined the same way as for the body (Fig. 10.14A). For coronal images, the knees are flexed and the feet are positioned flat against the gantry table. The coronal sections are obtained with the beam directed to the dorsum of the foot. More commonly modified coronal images are obtained by angling the gantry or by using a foot wedge (Fig. 10.14B). A lateral scanogram helps to establish the degree of necessary gantry tilt. Axial images are obtained with the feet perpendicular to the gantry table, great toes together, and the knees fully extended. The beam is directed parallel to the soles of the feet. Sagittal images are usually generated by using reformation technique, although direct sagittal sections can also be obtained by placing the patient in the lateral decubitus position. Images in all planes are usually acquired using 3- or 5-mm thin contiguous sections. For threedimensional (3D) reconstruction, 1.5- or 2-mm contiguous sections are required, although 5-mm sections with a 3-mm overlap can also be used. MRI, with its direct multiplanar capabilities and excellent soft-tissue contrast resolution, has proved to be superior to
CT for the evaluation of ankle tendons and ligaments. The tendons show uniformly low signal intensity in all spin echo pulse sequences, with the exception of the Achilles tendon and tibialis posterior tendon. These two tendons, on long repetition time (TR) sequences, occasionally show small foci of intermediate signal intensity within their substance, particularly near their insertions to the calcaneal tuberosity and the navicular bone, respectively. From a practical point of view, it is helpful
to memorize the location and relationship
On the sections in the sagittal plane, the tibialis posterior, flexor digitorum longus, and flexor hallucis longus tendons are identified on the medial cuts. The peroneus longus and brevis tendons are seen on the lateral sections (Fig. 10.18). The Achilles tendon is best seen on midline sagittal
The pathologic conditions of tendons and ligaments are demonstrated by discontinuity of the anatomic structure, the presence of high signal intensity within the tendon substance on T2-weighted images, and inflammatory changes within or around the tendons, which again can be demonstrated by a change in the normal signal intensity.
Foot Most injuries to the foot can be sufficiently evaluated on the standard radiographic examination of the foot, which includes the anteroposterior, lateral, and oblique projections. Only occasionally are special tangential projections required. The anteroposterior radiograph of the foot adequately demonstrates the metatarsal bones and phalanges
(Fig. 10.21) This view reveals an important anatomic feature known as the first intermetatarsal angle, which normally ranges from 5 to 10 degrees (Fig. 10.21C). This angle is an important factor in the evaluation of forefoot
deformities because it represents a way to quantify the amount of metatarsus primus varus associated with hallux valgus. On the lateral radiograph (Fig. 10.22A,B), Boehler angle (also known as a tuber angle), an important anatomic relation of the talus and the calcaneus, can be appreciated
(Fig. 10.22C). In fractures of the calcaneus, this angle, which normally ranges from 20 to 40 degrees, is decreased because of compression of the superior aspect of the bone (see Fig. 10.81). This measurement also aids in the evaluation
of depression of the posterior facet of the subtalar joint. On the lateral view, calcaneal pitch can also be evaluated. This measurement is an indication of the height of the foot and normally ranges from 20 to 30 degrees (Fig. 10.22D). Higher values indicate a cavus foot deformity (pes cavus), and lower values indicate a flat foot deformity (pes
planus). The other important measurement obtained on the lateral foot radiograph is the angle of Gissane (also known as a critical angle), which is formed by the downward and upward slopes of the calcaneal dorsal surface (Fig. 10.23). The normal values of this angle are 125 to 140 degrees. The greater values suggest a fracture of the
posterior facet of the subtalar joint. An oblique radiograph of the foot is also obtained as part of the standard radiographic examination (Fig. 10.24). Injuries to the
Radiographic evaluation of foot injuries is complicated by the presence of multiple accessory ossicles, which are considered secondary centers of ossification, and the sesamoid bones, which may mimic a fracture (Fig. 10.28A,B); conversely, a chip fracture can be misinterpreted as a mere ossicle (Fig. 10.28C,D). Thus, it is important to recognize these structures on conventional radiographs. In addition to radiography, ancillary imaging techniques may need to be used in the evaluation of injury to the foot. Radionuclide imaging (bone scan) is a valuable means of detecting stress fractures, common foot injuries that are not always obvious on the standard radiographic examination. CT is especially effective in assessing complex fractures, particularly of the calcaneus. Tenographic examination may also be required to evaluate injury to the tendons of the foot (see previous text and Figs. 10.13 and 10.80). MRI is now frequently used to evaluate trauma to the foot. During evaluation of MRI of the ankle and foot, it is helpful to use checklist as provided in Table 10.1. Injury to the Ankle All ankle injuries can be broadly classified, according to the mechanism of injury, as resulting from inversion (Fig. 10.30) or eversion (Fig. 10.31) stress forces. Inversion injuries are much more common, accounting for 85% of all traumatic conditions involving the ankle. These groupings apply to both fractures and injuries to the ligament complexes of the ankle. However, it is in the latter type of injuries that they are particularly helpful in determining and evaluating the specific type of ligament injury, especially in the presence of certain fractures about the ankle. Fractures About the Ankle Joint In addition to being classified by mechanism of injury, fractures about the ankle joint can also be classified by the anatomic structure involved (Fig. 10.32) and designated as:
These fractures, when viewed from the standpoint of pathomechanics, may be either inversion or eversion injuries or a combination of both. The various types of eversion fractures are best known by their eponyms, including the Pott, Maisonneuve, Dupuytren, and Tillaux fractures (see later). All of the following ankle fractures involving the distal tibia and fibula can be diagnosed on the standard radiographic projections. However, CT may be useful in delineating the extent of the fracture line, and this modality is particularly effective in evaluating lateral displacement in the juvenile Tillaux fracture. To evaluate associated ligament injuries, MRI is the technique of choice.
Only gold members can continue reading. Log In or Register to continue Which projection of the foot will show the cuboid in profile?Foot PA Oblique (Medial Rotation)
Cuboid is shown in profile. Position of patient Lateral recumbent position on affected side. Fully extend leg. Turn patient toward prone position until plantar surface of foot forms an angle of 45 degrees to plane of IR.
Which projection of the foot will best demonstrate the longitudinal arch?Chapter 7. Which of the following projection will best demonstrate the tarsal navicular free of superimposition?Cards
What projection will best demonstrate the tibiofibular articulations quizlet?Which of the following projections of the ankle would best demonstrate the distal tibiofibular joint? To best demonstrate the distal tibiofibular articulation, a 45° medial oblique projection of the ankle is required. The 15° medial oblique is used to demonstrate the ankle mortise (joint).
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