Preoperative Evaluation and Imaging
RICHARD D. FERKEL
GREGORY R. APPLEGATE
The ankle and foot are complex structures composed of multiple joints and anatomic structures. Evaluation of the ankle and foot requires a thorough knowledge of the intra- and extra-articular anatomy, normal variants, kinesiology, and imaging appearance. It is important to be able to separate normal from abnormal complaints and findings and to understand how the ankle and foot relate to the rest or the body.
The most important methods of evaluation are a careful history and a physical examination. Plain radiographs are then obtained, and a preliminary diagnosis is made. Sometimes the diagnosis is not obvious, and various etiologies must be considered in the differential diagnosis. In these cases, additional diagnostic tests may be necessary. Many different tests are useful in the ankle and foot, but they must be used judiciously and a “shotgun” approach avoided (Table 2-1). A keen understanding of the indications and limitations of each test is mandatory for cost-effectiveness; they vary from case to case.
HISTORY
The most common complaints or symptoms patients note in the ankle and foot include one or more of the following: pain, swelling, locking, catching, grinding, loss of motion, giving way, deformity, numbness, or tingling. It is important to note when the pain started and how long the pain has been present. If an accident or injury was involved, the mechanism of injury must be identified. The patient should be asked what brings on the symptoms, how long they last, and what relieves them. Sometimes ankle and foot symptomatology is associated with symptoms in other areas of the body, and this should be sought. If the patient is on medication or using braces, supports, or orthotics, this should be noted in relation to his or her complaints.
Table 2-1. Diagnostic Testing of the Foot and Ankle | |
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A history of current shoe wear is important, because often new shoes are associated with certain types of ankle and foot complaints or can contribute to the symptoms with certain activities. A complete medical history is necessary, because some ankle and foot conditions are related to systemic diseases or conditions in other parts of the body. Moreover, the family history may detect certain congenital abnormalities that cause similar complaints from generation to generation.
The most important complaint in the ankle and foot is pain. Localizing the pain to a specific area helps to narrow the diagnosis. Acute pain must be differentiated from chronic pain. Using the questions mentioned above, a differential diagnosis can be developed, and in many cases, a definitive diagnosis is made. A detailed differential diagnosis of pain in the ankle and foot is beyond the scope of this chapter, and the reader is referred elsewhere for a detailed list.1
Pain, mechanical blockage, muscle/tendon problems, scarring at the joint, and nerve injury can all cause loss of motion. In addition, swelling can be either localized or generalized, painful or nonpainful, and related to activity.
Locking can be due to acute pain, swelling, loose bodies, tendon subluxation, ligamentous injury, or osteoarthritic formation. Although “locking” and “catching” represent different sensations and are usually caused by different pathologies, the patient may use the terms interchangeably.
Patients often complain of popping around the joint, midfoot, or forefoot. These sounds are usually normal but must be investigated if they continue or suggest intra-articular damage. It is not uncommon for the peroneal
tendons to click or pop, particularly in hyperlax patients, or for the extensor tendons to cause similar problems. In a dancer, however, persistent popping or catching on the medial side of the foot may suggest a tenosynovitis of the flexor hallucis longus (FHL) or “hallux saltans.” Deformities about the ankle and foot are usually congenital, insidious, or traumatic in origin. Only when the patient becomes symptomatic is the deformity noted, although it may have been present for a long time. Such is the case with pain over “pump bumps” or in the area of the accessory navicular and occasionally over the base of the fifth metatarsal.
tendons to click or pop, particularly in hyperlax patients, or for the extensor tendons to cause similar problems. In a dancer, however, persistent popping or catching on the medial side of the foot may suggest a tenosynovitis of the flexor hallucis longus (FHL) or “hallux saltans.” Deformities about the ankle and foot are usually congenital, insidious, or traumatic in origin. Only when the patient becomes symptomatic is the deformity noted, although it may have been present for a long time. Such is the case with pain over “pump bumps” or in the area of the accessory navicular and occasionally over the base of the fifth metatarsal.
Numbness and tingling may represent either localized nerve entrapment or referred pain from a nerve injury more proximally or along the spine.
PHYSICAL EXAMINATION
Standing Examination
To avoid overlooking pertinent findings, the physical examination of the ankle and foot is both tedious and demanding. Each examiner may develop a specific routine, and the exact sequence of the examination is not critical. However, each area must be carefully evaluated, and the entire examination must be integrated with the history. According to Coughlin, Saltzman, and Anderson, the examiner must consider the foot and ankle from three different points of view: first, as parts of the entire body; second, as important constituents of the locomotor system; and third, as relatively recent evolutionary acquisitions and, thus, subject to various individual anatomic and functional variations.2
 FIGURE 2-1. Longitudinal arch. (A) Lateral view of medial longitudinal arch. (B) Posterior view of medial longitudinal arch. Note the transverse arch provided by the metatarsal heads. (Illustration by Susan Brust.) |
Every ankle and foot examination should include inspection, palpation, and manipulation. The sequence varies for walking, standing, or sitting and also varies with and without shoes.
The initial examination should include an assessment of the patient’s gait with and without shoes, noting any limp, asymmetry of the arm swing, degree of toeing in and out, and the amount of excessive pronation or supination. The gait should be analyzed as to normal amount of stance and swing phase; the phase in which the gait abnormalities occur should be noted.
The patient’s shoes should be inspected for the type worn, asymmetry of wear, and any pads, lifts, or orthotics present. Walking should be assessed, as well as the ability to go up on tiptoes and heels while standing and walking, as well as hopping and squatting. Then, the shape of the foot is evaluated. Usually the dorsum of the foot makes a dome, secondary to the medial longitudinal arch (Fig. 2-1A, B). The arch can be unusually high (pes cavus) or diminished (pes planus; Fig. 2-2A-C).
 FIGURE 2-2. Arch types. (A) Cavus foot, with elevation of the medial longitudinal arch and a slight hindfoot varus. (B) Normal arch. (C) Pes planus, with loss of the medial longitudinal arch and hindfoot valgus. From the posterior view, the “too many toe” sign can be noted secondary to a rupture of the posterior tibial tendon. (Illustration by Susan Brust.) |
The alignment of the calf to the hindfoot is also carefully evaluated. Excessive hindfoot valgus with prominence of the medial part of the foot may suggest rupture of the posterior tibial tendon. This can be confirmed by the presence of a positive “too many toe” sign and inability of the patient to go up on his or her tiptoes on the affected side (see Fig. 2-2C). The windlass action of the foot is also evaluated. Normally, dorsiflexion in the toes increases the tension of the plantar aponeurosis, which causes the longitudinal arch to rise. Failure of the longitudinal arch to rise suggests prolonged pes planus, with abnormal stretching and elongation of the plantar aponeurosis (Fig. 2-3).
With the patient standing, a careful assessment is made of the alignment of the hip to the knees to the ankle. A patient with “malicious malalignment” has a combination of abnormalities that contribute to pain about the hip, knee, and ankle (Fig. 2-4). When appropriate, pelvic tilt and lower back abnormalities should also be assessed.
Seated Examination
Once the patient has been carefully evaluated in the standing position, he or she is then examined seated.
Ankle
The ankle is initially evaluated visually for swelling or edema. The examiner should note whether the swelling appears to be intra-or extra-articular and whether it is anterior, posterior, medial, or lateral.
 FIGURE 2-3. Windlass mechanism. (A) Normal position of plantar aponeurosis. (B) Dorsiflexion with the toes increases the tension on the plantar aponeurosis, which causes the longitudinal arch to rise. (Illustration by Susan Brust.) |
Palpation should be done carefully to detect areas of specific pain about the ankle. After a chronic ankle sprain, there is sometimes pain along the lateral portion of the ankle and foot. It is important to pinpoint the exact location of the pain, including whether it is at the syndesmosis, over the lateral gutter and anterior talofibular ligament, or at the sinus tarsi (Fig. 2-5). Sometimes, there is pain in all areas. Posterior ankle pain is sometimes difficult to elicit on examination, and a high index of suspicion is necessary to rule out posteromedial osteochondral lesions and to differentiate them from injuries to the Stieda process or the os trigonum. Attachments of all the ligaments about the ankle should be carefully palpated, including the deltoid, the anterior and posterior inferior tibiofibular ligaments, the anterior and posterior talofibular ligaments, and the calcaneofibular ligaments.
Range of Motion
The range of motion of the ankle joint, as with all joints, is assessed passively and actively (Fig. 2-6A).3 It is important to compare one side to the other to detect subtle losses in motion and to determine whether an abnormality exists. In the elderly, physiologic limitation of plantarflexion may be present; it is usually of no clinical significance.4 However, limitation of any dorsiflexion is usually significant. Loss of dorsiflexion of more than 10° should be assessed with the knee in both extension and flexion using the Silfverskiöld test. If dorsiflexion in the ankle is significantly increased by flexion in the knee, a shortened gastrocnemius is diagnosed because this muscle crosses the knee joint, whereas the soleus does not. In this case, flexing the knee should relax the tight gastrocnemius and allow more ankle dorsiflexion. If knee flexion does not improve dorsiflexion, it may be due to contracture of the soleus or gastrocnemius, or both. Ankle dorsiflexion can also be limited secondary to arthrofibrosis, posterior ankle capsular contraction, previous trauma, and osteophytes of the distal tibia and talus (see Fig. 2-6B). Ankle plantarflexion can be limited by a ruptured Achilles tendon, arthrofibrosis, and rupture of the posterior tibial tendon (see Fig. 2-6C).
 FIGURE 2-4. “Malicious malalignment” syndrome. The combination of increased Q-angles of the knee, hindfoot, and forefoot valgus, and femoral neck anteversion contribute to this problem. (Illustration by Susan Brust.) |
 FIGURE 2-5. Pain in the lateral aspect of the ankle can cause confusion as to its origin. The pain can occur at the syndesmosis (top thumb), the anterior talofibular ligament (middle thumb), or the subtalar joint and sinus tarsi (lower thumb). (Illustration by Susan Brust.) |
The dorsum of the foot fits into a socket or mortise formed superiorly by the tibia and laterally by the fibula. Because the talus is wider anteriorly, it is held tightly between the malleoli when the ankle is dorsiflexed. However, when the ankle is plantarflexed, the narrower posterior aspect lies between the malleoli, and there is some mild degree of lateral mobility (Fig. 2-7). Dorsiflexion may be diminished or restricted when the wider anterior part of the talus no longer fits easily into the mortise. This is the case when the intermalleolar distance has been narrowed secondary to persistent equinus of the foot or after fractures or other trauma. Dorsiflexion can also be restricted with incongruity of the mortise after trauma (Fig. 2-8). Moreover, active dorsiflexion may be limited by weakness of the extensor tendons, and in some cases, a ruptured anterior tibial tendon may be missed if a careful assessment of ankle dorsiflexion by the extensor hallucis longus is not made.
Ligament Testing
The anterior talofibular ligament is best tested with the foot in a plantarflexed position. In this position, inversion stress testing of the hindfoot will demonstrate any laxity present in the anterior talofibular ligament (Fig. 2-9). When the foot is dorsiflexed, the calcaneofibular ligament is placed on stretch, and with inversion stress testing, the laxity of this ligament may be noted. With a tear of both the anterior talofibular and calcaneofibular ligaments, a “double ligament tear,” talar tilt will occur in dorsi- and plantarflexion (see Fig. 2-9).
The anterior drawer test is an important test for ligamentous laxity and is performed with the ankle held at 90° and the calcaneus pulled anteriorly and slightly internally rotated, while the examiner’s other hand holds the distal tibia (Fig. 2-10). An appreciation for the amount of forward motion of the talus in relation to the tibia is important. Anterior motion of more than 3 to 4 mm usually indicates laxity and injury in the anterior talofibular ligament.
A significantly increased anterior drawer suggests a double ligament tear (see Fig. 2-10).
A significantly increased anterior drawer suggests a double ligament tear (see Fig. 2-10).
 FIGURE 2-6. Ankle range of motion. (A) Dorsiflexion and plantarflexion of the ankle. (B) Loss of dorsiflexion secondary to anterior osteophytes, posterior capsular contraction, shortened gastrocnemius, or ruptured anterior tibial tendon. (C) Loss of plantarflexion secondary to ruptured posterior tibialis or Achilles or arthrofibrosis of the ankle. (Illustration by Susan Brust.) |
 FIGURE 2-7. Ankle excursion. (A) The width of the talus. The anterior talus is wider than the posterior portion. (B) When the ankle is plantarflexed, the narrower posterior talus lies between the malleoli and some degree of lateral mobility exists. (C) With ankle dorsiflexion, the talus is held tightly between the malleoli. (Illustration by Susan Brust.) |
 FIGURE 2-8. Ankle mortise incongruity. (A) Normal ankle mortise. (B) After a fracture, there is a widened medial clear space and shortening of the lateral malleolus, recognized radiologically as a step off in the alignment of the subchondral plates of the tibia and of the lateral malleolus. (Illustration by Susan Brust.) |
 FIGURE 2-9. Inversion stress test. A single ligament tear allows increased talar tilt (inset). A double ligament tear leads to significant talar tilt with inversion stress. (Illustration by Susan Brust.) |
 FIGURE 2-10. Anterior drawer test. With the tibia secured, the heel is pulled forward and internally rotated. Note the subluxation of the talus anteriorly on the distal tibia (inset). A double ligament tear leads to increased anterior excursion of the talus on the tibia. (Illustration by Susan Brust.) |
It is always important with inversion stress testing and anterior drawer testing to compare the findings with the asymptomatic opposite side. Coughlin et al. have noted a variation of the anterior drawer sign that may be useful to determine how much internal rotation occurs when the lateral aspect of the foot is grasped with one hand and the other hand is placed on the distal tibia, while palpating the articulation between the lateral articular surface of the talus and the anterior aspect of the distal fibula.2 This is done with the ankle in neutral position. Pulling forward on the forefoot while internally rotating sometimes demonstrates a rotatory laxity as a result of an injury to the anterior talofibular ligament.
Injuries to the syndesmosis are often underestimated or overlooked by orthopedists and nonorthopedists alike. Although not entirely clear, the mechanism of injury appears to be primarily an external rotation injury, although hyperdorsiflexion has been reported to lead to tears of the syndesmosis as well. Diagnosis is made by palpating directly over the syndesmosis and more proximally along the interosseous membrane. The “squeeze test” is performed by compressing the fibula to the tibia above the midportion of the calf; the test is considered positive when proximal compression produces distal pain in the area of the torn interosseous membrane and syndesmotic ligament (Fig. 2-11). The “external rotation stress test” is also useful in diagnosing syndesmotic ankle sprains and is performed by applying external rotational stress to the foot and ankle with the knee bent in 90° of flexion and the ankle in neutral position (Fig. 2-12). A positive test produces pain over the anterior or posterior inferior tibiofibular ligament(s) and over the interosseous membrane. The third test is displacement of the fibula at the syndesmosis itself. The fibula sits in a groove on the lateral border of the tibia, but the anterior lip of the tibial groove is more prominent than the posterior lip. Therefore, even in a normal ankle, anterior fibular displacement is difficult, but posterior displacement can often be palpated. In the ankle with an injured syndesmosis, this posterior displacement may be increased and can elicit pain.
Muscle function about the ankle should be carefully assessed. It is important to determine the strength of each muscle and to palpate the tendon to ensure one muscle is not compensating for another. Usually, this is fairly easy, except in cases of injuries to the anterior and posterior tibial tendons. A strong extensor hallucis longus can compensate for the anterior tibial tendon, and this tendon action must be eliminated to assess the anterior tibial tendon accurately.
 FIGURE 2-11. The squeeze test is performed by compressing the fibula to the tibia at the midportion of the calf. With a tear of the interosseous membrane and syndesmotic ligament, pain occurs in the region distally. (Illustration by Susan Brust.) |
Heel and Heel Cord
Varus or valgus deformities of the heel should be noted. The most common cause of heel pain is plantar fasciitis, which will elicit point tenderness along the medial calcaneal tuberosity (Fig. 2-13A). This pain can be due to multiple causes, including systemic diseases such as rheumatoid arthritis or Reiter syndrome, or nerve entrapment (see Fig. 2-13B). Tenderness in the retrocalcaneal bursa can be associated with inflammation of the Achilles tendon or isolated bursal inflammation posterior to the ankle joint. Heel cord shortening was discussed in the ankle section. However, Achilles tendon problems are common and can be classified as inflammation of the peritenon, tendinosis, or partial or complete tears. A nodular thickening may be present in patients with chronic tendinosis or partial Achilles tears. Ruptures of the Achilles tendon are usually obvious and confirmed by a positive Thompson test. Tenderness along the painful thickening of the posterior-superior portion of the os calcis overlying the Achilles tendon is often found, especially in females (“pump bumps”), and is associated with palpable soft tissue thickening. Achilles tendon pain must be differentiated from ankle pain and synovitis.
 FIGURE 2-12. The external rotation stress test produces pain over the anterior and posterior inferior tibiofibular ligaments and the interosseous membrane when positive. (Illustration by Susan Brust.) |
Subtalar Joint
The subtalar joint can be a difficult area to examine and diagnose. The range of motion of the subtalar joint varies, but Isman and Inman, in a series of feet in cadaver specimens, found a minimum of 20° and a maximum of 60° motion.5 Subtalar motion is tested by holding the calcaneus in one hand and the forefoot, including the transverse
tarsal joint, in the other and bringing the subtalar joint into both inversion and eversion (Fig. 2-14). The most accurate method of determining subtalar motion is to place the patient prone and flex the knee to 135°.2 If motion is limited and considerable pain occurs on passive motion along with spasm, subtalar pathology should be suspected. Usually this is associated with tenderness along the sinus tarsi and posterior talocalcaneal joint and occasionally tenderness along the medial portion of the subtalar joint. If loss of subtalar motion is detected, the examiner should consider the possibility of an arthritic process in the subtalar joint, peroneal spastic flatfoot, or an anatomic abnormality such as tarsal coalition.
tarsal joint, in the other and bringing the subtalar joint into both inversion and eversion (Fig. 2-14). The most accurate method of determining subtalar motion is to place the patient prone and flex the knee to 135°.2 If motion is limited and considerable pain occurs on passive motion along with spasm, subtalar pathology should be suspected. Usually this is associated with tenderness along the sinus tarsi and posterior talocalcaneal joint and occasionally tenderness along the medial portion of the subtalar joint. If loss of subtalar motion is detected, the examiner should consider the possibility of an arthritic process in the subtalar joint, peroneal spastic flatfoot, or an anatomic abnormality such as tarsal coalition.
 FIGURE 2-13. Plantar fasciitis. (A) Palpation of the plantar fascia at the medial calcaneal tuberosity often elicits pain. (B) There are numerous causes for plantar heel pain, including entrapment of the medial or lateral plantar nerves; rarely is a calcaneal spur the source of pain. (Illustration by Susan Brust.) |
Muscle function about the subtalar joint should also be carefully assessed. Posterior tibial tendon function may be difficult to differentiate from the anterior tibial tendon when checking inversion. The posterior tibial tendon can usually be assessed by palpation with the patient actively inverting the foot in plantarflexion. The tendon can also be checked by placing the foot into an everted position and then asking the patient to invert against some resistance (Fig. 2-15). Weakness of the peroneal tendons may be confusing because the peroneal brevis muscle everts the foot and the peroneal longus brings about plantarflexion of the medial border of the foot but can only weakly evert the foot. To test the peroneal longus, the patient should plantarflex the medial side of the foot and the examiner should resist beneath the first metatarsal head.
Tendinitis of the FHL tendon behind the medial malleolus is so common in dancers that it is known as “dancer’s tendinitis.” This condition can be misdiagnosed as Achilles or posterior tibial tendinitis if the examiner is not careful to find the exact location of the pain. The FHL tendon is injured as it passes through the fibro-osseous tunnel
from the posterior aspect of the talus to the level of the sustentaculum tali and acts like a rope through a pulley. When injured, it begins to bind and a nodular partial tear may be present, causing triggering of the big toe or so-called hallux saltans6 (Fig. 2-16).
from the posterior aspect of the talus to the level of the sustentaculum tali and acts like a rope through a pulley. When injured, it begins to bind and a nodular partial tear may be present, causing triggering of the big toe or so-called hallux saltans6 (Fig. 2-16).
 FIGURE 2-14. Subtalar motion. (A) Inversion motion. (B) Inversion testing against resistance. (C) Eversion motion. (D) Eversion testing against resistance. (Illustration by Susan Brust.) |
Transverse Tarsal Joint
The motion of the transverse tarsal joint can be determined by holding the calcaneus in line with the long axis of the tibia and the forefoot parallel to the floor. Abduction and adduction are then determined and noted. There should be twice as much adduction as abduction of the forefoot. In conditions such as rupture of the posterior tibial tendon or degenerative arthritis of the midtarsal joints, a neutral position cannot be achieved because the foot is constantly maintained in a chronically abducted position. Involvement at one or more of the midtarsal joints is not uncommon and is isolated by local joint pain and tenderness. Charcot disorder of the foot may also start in this area with palpable bony thickening.
Metatarsophalangeal Joints
Pain over the metatarsophalangeal joint of the great toe is usually due to either degenerative arthritis or a bunion-type deformity. The joint should be palpated carefully for the presence of not only pain but also synovitis or instability. The metatarsophalangeal joints of toes 2 through 5 should also be examined. Synovitis is often present in either the second or third metatarsophalangeal joints, and a Lachman-type maneuver at the metatarsophalangeal joint will demonstrate instability indicative of disruption of the plantar plate mechanism. The medial and lateral sesamoids should also be carefully checked beneath the first metatarsal head to rule out inflammation or fracture. Motion of the metatarsophalangeal joints is measured by placing the ankle at 90° and having the patient actively dorsi- and plantarflex at these joints and at the interpha-langeal joints. Normal motion is 70° dorsiflexion and 45° plantar flexion (Fig. 2-17). Because there is much individual variability in motion, it is important to compare the normal to the abnormal side. Loss of motion of the great toe metatarsophalangeal joint is usually associated with degenerative joint disease and osteophyte formation, either traumatic or idiopathic in origin. Loss of motion of the interphalangeal joints may be secondary to synovitis, degenerative joint disease, Freiberg infarction, or instability.
The second metatarsal is relatively immobile and is usually the longest metatarsal. Therefore, if there is an abnormality of the first metatarsophalangeal joint such as a significant hallux valgus deformity or as a result of
bunion surgery that produces shortening, dorsiflexion, or instability of the first metatarsophalangeal joint, a painful diffuse callus may develop beneath the second metatarsal. In contrast, the fourth metatarsal is the most mobile and is rarely associated with any significant pathologic condition.
bunion surgery that produces shortening, dorsiflexion, or instability of the first metatarsophalangeal joint, a painful diffuse callus may develop beneath the second metatarsal. In contrast, the fourth metatarsal is the most mobile and is rarely associated with any significant pathologic condition.
 FIGURE 2-15. Posterior tibial tendon testing. (A) Normal inversion with intact tendon. (B) Loss of inversion with ruptured posterior tibial tendon. (C) Testing the ruptured tendon, starting from an everted position. (Illustration by Susan Brust.) |
 FIGURE 2-16. Hallux saltans can develop from tendinitis of the flexor hallucis longus as it passes through the fibro-osseous tunnel on the medial side of the foot. (Illustration by Susan Brust.) |
 FIGURE 2-17. Dorsiflexion and plantar flexion of the great toe. With degenerative joint disease of this joint, motion is lost in both planes. (Illustration by Susan Brust.) |
Referred Pain
When examining the foot and ankle, all other joints in the lower extremity should also be carefully evaluated with a complete examination. Pathology in the lumbar back, hip, or knee may refer pain to the foot or ankle region. Symptoms of pain, numbness, weakness, and swelling can all be due to causes outside of the foot and ankle (Fig. 2-18).
RADIOLOGIC IMAGING
After a careful history and physical examination, radiologic evaluation is critical to the proper diagnosis and treatment of ankle and foot disorders. Over the last 10 to 15 years, newer imaging techniques have given us the opportunity to better understand numerous pathologic disorders and sometimes to diagnose previously unknown conditions.7
Routine Radiography
At least two orthogonal radiographs should be performed. The anterior/posterior (AP) radiograph is the best overview of the ankle and is particularly valuable to verify that an intact distal tibiofibular joint is present (Fig. 2-19A). On the lateral view, the articular space between the talus and tibia is seen, as well as the articulation of the talus with the navicular and calcaneus (see Fig. 2-19B). Weight-bearing AP and lateral ankle x-rays demonstrate standing alignment and accentuate non-weight-bearing deformities.
 FIGURE 2-18. Pain in the foot can be referred from the back, hip, or knee. (Illustration by Susan Brust.) |
 FIGURE 2-19. Normal ankle x-rays. (A) Anterior/posterior view of the ankle. The medial clear space is well seen with overlap of the fibula with the distal tibia and talus. (B) Lateral view of the ankle. Both the distal anterior and posterior portions of the tibia can clearly be seen, as can the space between the distal tibia and talus and subtalar joint. (C) Mortise view of the ankle. Normally, the medial clear space measures 2 mm as does the tibiofibular syndesmosis. The zone of rarefaction in the talus shows the posterior facet of the subtalar joint. |
The ankle mortise is best evaluated by having the patient recumbent with the leg and foot rotated internally 20° or 30° (see Fig. 2-19C). If the radiograph is properly performed, the medial and lateral clear spaces and the distal tibiofibular syndesmosis can be well seen.
The tibiofibular clear space, the tibiofibular overlap, and the medial clear space are measured on the AP and mortise views (Fig. 2-20). The tibiofibular clear space is the distance between the incisura fibularis of the posterior tibia and the medial border of the fibula, measured
1 cm proximal to the tibial plafond articular line on the AP and mortise views. This space is usually considered within normal limits if it is <6 mm. The tibiofibular overlap is the distance between the medial border of the fibula and the lateral border of the anterior tibia, measured 1 cm proximal to the tibial plafond articular line. A normal tibiofibular relationship is indicated by at least 1 mm overlap of the tibia and the fibula on the AP and mortise views. The medial clear space is the distance between the medial border of the talar dome and the lateral border of the medial malleolus, measured 1 cm distal from the tibial plafond articular line. The distance defines the integrity of the ankle mortise and is normally 2 to 3 mm. A medial clear space of more than 3 to 4 mm is associated with ankle fractures or syndesmotic injuries in which the talus shifts laterally. This finding also indicates a rupture of the deltoid ligament. In addition, a detailed evaluation of the tibiotalar joint congruity on the lateral view can be important in the overall evaluation of a syndesmosis injury. Anterior widening of the tibiotalar joint is consistent with a syndesmotic injury. It is always important to obtain comparison radiographs of the contralateral ankle to help with the assessment.8
1 cm proximal to the tibial plafond articular line on the AP and mortise views. This space is usually considered within normal limits if it is <6 mm. The tibiofibular overlap is the distance between the medial border of the fibula and the lateral border of the anterior tibia, measured 1 cm proximal to the tibial plafond articular line. A normal tibiofibular relationship is indicated by at least 1 mm overlap of the tibia and the fibula on the AP and mortise views. The medial clear space is the distance between the medial border of the talar dome and the lateral border of the medial malleolus, measured 1 cm distal from the tibial plafond articular line. The distance defines the integrity of the ankle mortise and is normally 2 to 3 mm. A medial clear space of more than 3 to 4 mm is associated with ankle fractures or syndesmotic injuries in which the talus shifts laterally. This finding also indicates a rupture of the deltoid ligament. In addition, a detailed evaluation of the tibiotalar joint congruity on the lateral view can be important in the overall evaluation of a syndesmosis injury. Anterior widening of the tibiotalar joint is consistent with a syndesmotic injury. It is always important to obtain comparison radiographs of the contralateral ankle to help with the assessment.8
 FIGURE 2-20. Normal radiographic relationships that are important in evaluation of the tibiofibular articulation. (A, tibiofibular clear space; B, tibiofibular overlap; C, medial clear space.) (Illustration by Susan Brust.) |
Less common projections include the Harris-Beath view or the axial view of the calcaneus. This is useful for evaluating subtle calcaneal fractures, injuries to the subtalar joint, and talocalcaneal coalitions. The Broden view is helpful in visualizing the posterior facet of the subtalar, talofibular, and tibiofibular joints. Different portions of the subtalar joint can be seen depending on the tube angle. The Cobey view, used to evaluate the position of the calcaneus relative to the tibial axis and the ankle joint, is particularly helpful in looking at varus and valgus alignment.9
Weight-bearing AP and lateral views of the foot are routinely taken to evaluate foot disorders, and oblique x-rays are often helpful to better demonstrate the sinus tarsi, calcaneocuboid, and tarsometatarsal arrangements (Fig. 2-21A-C).
Hindfoot Alignment View
Saltzman and Ek-Khoury have popularized the coronal plane hindfoot alignment view.10 Using this view, the moment arm between the weight-bearing axis of the leg and the contact point of the heel can be estimated. They presented normative data on 57 asymptomatic patients. This is particularly helpful in determining varus and valgus malalignments in the coronal plane (Fig. 2-22).
Stress Radiographs
Stress x-rays are used to evaluate ligamentous integrity about the ankle and subtalar regions. These x-rays may be done manually by the physician or an experienced assistant or by a mechanical device or jig. Comparison x-rays are essential because there is a large variation in normal ligamentous laxity. To generate a reproducible amount of stress, the Telos device can be used11 (Fig. 2-23). A maximum stress of 15daN (decaNewtons) is applied in eversion, inversion, or anterior drawer, as indicated. The Telos device has advantages that include the following:
1. No radiation exposure to the examining physician
2. Reproducible patient motion
3. Gradual and accurate application of stress, which avoids muscle splinting
4. Reproducible fixation in 18° internal rotation to approximate the mortise view during stress
Stress views are most useful for evaluating the lateral and medial ligament complexes. Plantarflexion/inversion stress is a better indicator of the integrity of the anterior talofibular ligament; dorsiflexion/inversion stress is best for testing the calcaneofibular ligament.11 Sauser and coworkers,12 using the Telos device, found that a talar tilt of 10° or more was associated with a lateral ligament injury in 99% of cases. Normal values for talar tilt reportedly range from 5° to 23°.13 Chrisman and Snook14 noted when comparing both ankles that a difference of more than 10° was significant when measuring the anterior talofibular and calcaneofibular ligaments (Fig. 2-24). Cox and Hewes15 noted that a 5° difference in talar tilt between the two ankles was clinically significant, and we use this number to help assist us in determining which patients need ankle ligament reconstruction.
The anterior drawer stress test specifically tests the integrity of the anterior talofibular ligament and is the most
reliable indicator of injury to it. Gould and colleagues16 found that an increase of 4 mm indicated instability in the anterior drawer test. However, Laurin and associates17 considered an increase of more than 9 mm to be abnormal. Overall values of up to 4 mm separation between the talus and distal tibia are considered normal, values of 4 to 10 mm are probably abnormal, and values over 10 mm are grossly abnormal. These measurements are best performed at the posterior aspect of the talar and distal tibial articular surfaces (Fig. 2-25).
reliable indicator of injury to it. Gould and colleagues16 found that an increase of 4 mm indicated instability in the anterior drawer test. However, Laurin and associates17 considered an increase of more than 9 mm to be abnormal. Overall values of up to 4 mm separation between the talus and distal tibia are considered normal, values of 4 to 10 mm are probably abnormal, and values over 10 mm are grossly abnormal. These measurements are best performed at the posterior aspect of the talar and distal tibial articular surfaces (Fig. 2-25).
 FIGURE 2-21. Normal foot x-rays. Degenerative joint disease, subluxation or dislocation, avascular necrosis, accessory bones, and other abnormalities can be noted on these x-rays. (A) Anterior posterior view; (B) true lateral view; (C) oblique view. |
Subtalar instability can also be tested with the Telos device. Although this is more difficult to diagnose, the stress x-ray can detect laxity in the joint when done properly (Fig. 2-26).18, 19 Using the device, a Broden stress view of the subtalar joint when positive will show loss of talus and calcaneus facet parallelism. In addition, a lateral view of the subtalar joint with inversion stress of the hindfoot can demonstrate anterior translation of the posterior facet of the calcaneus relative to the posterior facet of the talus.
Tomography
In tomography, a focal point for each image is established and the structures anterior and posterior to this fulcrum are blurred out of focus by the movement of the x-ray tube and film in tandem. The tube and film can move in several different motions to optimize detail
in different planes. Tomograms can be unidirectional (linear tomography) or pluridirectional (complex). The main indications for tomography include evaluations for nonunions, most arthrodeses, and occasionally Lisfranc fracture-dislocations. Infrequently, they are used to evaluate osteochondral fractures of the talus, navicular stress fractures, calcaneal fractures, and subtalar arthritis. The disadvantages of tomography include high radiation exposure and an inaccurate picture of the structures not exactly perpendicular to the plane of the tube motion. Conventional tomography is no longer widely available and has been replaced by CT. Recently, however, with digital radiography (DR), some manufacturers have included a tomographic technique into their DR systems, which may have limited utility.
in different planes. Tomograms can be unidirectional (linear tomography) or pluridirectional (complex). The main indications for tomography include evaluations for nonunions, most arthrodeses, and occasionally Lisfranc fracture-dislocations. Infrequently, they are used to evaluate osteochondral fractures of the talus, navicular stress fractures, calcaneal fractures, and subtalar arthritis. The disadvantages of tomography include high radiation exposure and an inaccurate picture of the structures not exactly perpendicular to the plane of the tube motion. Conventional tomography is no longer widely available and has been replaced by CT. Recently, however, with digital radiography (DR), some manufacturers have included a tomographic technique into their DR systems, which may have limited utility.
Related posts:
Regional Anesthesia for Foot and Ankle Arthroscopy
Diagnostic Arthroscopic Examination
Arthroscopic and Open Approaches to Ankle Instability
Prone Arthroscopy for Posterior Ankle and Subtalar Joint Pathology
Endoscopic Plantar Fascia Release, Gastrocnemius Recession, and Intermetatarsal Nerve Decompression
Endoscopic Procedures for Retrocalcaneal Bursitis, Achilles Tendon, Posterior Tibial Tendon, Peroneal Tendons, and Flexor Hallucis Longus Tendon
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