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Special Radiographic Projections of the Foot and Ankle: A Primer for Residents and Fellows Arlene J. Richardson, MD, Michel A. Scott, RT(R), Gregory S. Stacy, MD University of Chicago Medical Center, Department of Radiology, Chicago, IL USA ABSTRACT Purpose: The ACR-SPR-SSR Practice Guideline for the Performance of Radiography of the Extremities provides recommendations for “routine” radiographic views of the foot and ankle. The purpose of this exhibit is to present non-routine or “special” radiographic projections of the foot and ankle that are often useful for diagnosing abnormalities not readily seen on routine views. Methods Used: Cases of “routine” and “special” radiographic views of the foot and ankle were collected from the imaging database at our institution, and are presented here. Results: Following a brief review of anatomy depicted on routine radiography of the foot and ankle, as well as the limitations of these projections, a variety of special radiographic views of the foot and ankle commonly used at our institution are discussed. Pictorial examples of normal anatomy depicted on these non-routine views, as well as examples of abnormalities better seen on these projections, are provided. Conclusions: Radiography is the mainstay of foot and ankle imaging. Standard projections are recommended for initial evaluation, with supplemental special views obtained to evaluate a specific problem or condition. These optional radiographic views of the foot and ankle can allow a more detailed and cost-effective evaluation of various pathologic conditions, which may be incompletely assessed by standard radiographic views. INTRODUCTION Foot and ankle disorders are common, yet potentially complex, representing a wide range of conditions. Indications for radiography of the foot and ankle include, but are not limited to, pain, trauma, arthropathies, infections, neoplasms, systemic diseases, congenital and developmental disorders, and preoperative or postoperative evaluation and follow-up. Routine radiographic views of the foot and ankle are typically the first line of imaging. • Routine radiographs of the ANKLE include AP, lateral and oblique views. The preferred oblique view is obtained with 15-20o of medial rotation of the leg and foot – the “mortise” view, which provides the best assessment of mortise congruity and the talar dome. An oblique view obtained with 45o of medial rotation of the leg and foot is used in some practices. AP view (left) allows evaluation of distal tibia and fibula, tibiotalar joint, proximal talus, and peripheral borders of tarsals. Note overlap of distal fibula and anterior tibial tubercle, as well as overlap of distal fibula and talus, limiting evaluation of tibiofibular and talofibular articulations, but implying ligamentous integrity. Lateral view (right) allows evaluation of tibiotalar joint congruity and potential effusion, talocalcaneal relationships, and 5th metatarsal base. Medial and lateral talar domes are superimposed, and fibula overlies posterior half of tibia. Medial oblique “mortise” view with 15-20o of medial rotation (left) allows evaluation of congruity of entire ankle mortise (arrows) with no overlap of distal fibula with anterior tibial tubercle or talus. Medial oblique view with 45o of medial rotation (right) allows evaluation of lateral malleolus and distal tibiofibular joint (arrow); distal tibia and fibula are often superimposed with talus. • REVERSE OBLIQUE VIEWS • Obtained with LATERAL (rather than medial) rotation; also called “LATERAL or EXTERNAL OBLIQUE” VIEWS • For the reverse (lateral) oblique view of the FOOT, the patient is positioned supine with the leg and foot rotated laterally until the plantar surface of foot forms an angle of 30 degrees to image receptor (elevation of the medial aspect of the foot). The central ray is directed to the 3rd metatarsal base, perpendicular to the image receptor. • This view can better demonstrate the bones of the medial aspect of the midfoot, which typically overlap one another on routine views, and can reveal subtle fractures of the 1st metatarsal base, medial cuneiform, navicular, and accessory navicular, as well as assess 1st TMT joint fusion following surgery. Lateral view (left) allows assessment of talus and calcaneus, and their relationship to midfoot and ankle joint, although bones of forefoot and midfoot partially obscured due to overlap. • • • • AP (far left), medial oblique (left) and lateral (top) foot radiographs show no fracture. Reverse/lateral oblique radiograph (right) shows navicular fracture (arrow). • For the reverse (lateral) oblique view of the ANKLE, the leg and foot are rotated 45o laterally. This view, which can add information about the medial malleolus, is used infrequently. • Routine radiographs of the FOOT include AP, lateral and oblique views. The oblique view is obtained with 30-40o of medial rotation of the foot (elevation of the lateral aspect of the foot with a radiolucent support block) AP view (left) allows evaluation of the phalanges, metatarsals, and tarsal bones anterior to the talus, although the second through fifth metatarsal bases, lateral cuneiform and cuboid, and anterior process of calcaneus are partially obscured due to overlap (red box). Oblique view (right) allows better assessment of lateral tarsometatarsal articulations by reducing overlap (green box). Note stress fracture (arrow). “SPECIAL” RADIOGRAPHS OF THE FOOT AND ANKLE (continued) “SPECIAL” RADIOGRAPHS OF THE FOOT AND ANKLE ROUTINE RADIOGRAPHS OF THE FOOT AND ANKLE Normal Broden I view (above). Note visualization of subtalar joint (arrow) and calcaneus. • Reverse/lateral oblique radiograph of ankle shows medial malleolus (arrows) and superior aspect of calcaneus. • • • SESAMOID VIEW A tangential projection of the sesamoid bones at the 1st MTP joint can be performed with the patient prone and the foot dorsiflexed so that the ball of the foot is perpendicular to the horizontal plane; the toes are then dorsiflexed at the MTP joints and placed on the image receptor (the Lewis Method). Alternatively, the patient may be seated on the table with the back of the heel placed on the image receptor and the plantar surface of the foot 75o relative to the horizontal; the patient then uses a band to dorsiflex his/her toes. In either case, the central ray is directed tangential to the ball of the foot and perpendicular to the image receptor. This view can allow visualization of both sesamoids without overlap with other bones, and hence can be useful for diagnosing fractures, arthritis, osteonecrosis and osteomyelitis. The Causton method involves placing the medial aspect of the foot on the image receptor, and then directing the central ray to the 1st MTP joint at and angle of 40o toward the heel; there is slight overlap of the sesamoids using this projection. Routine AP, oblique and lateral radiographs of the ankle show tri-malleolar “SER-IV” fractures (arrows) and bullet fragment in lateral soft tissues. Tangential projection (above) showing normal sesamoid bones. • • • Routine AP, lateral and oblique radiographs of the foot demonstrate typical changes of Charcot arthropathy (arrows) of the midfoot. Axial radiographs of the right and left calcaneus show abnormal slanting of the middle facet of the left subtalar joint (arrow) suggestive of nonosseous coalition, confirmed on CT • Routine radiographs of the OS CALCIS include lateral and axial views. The axial view can be obtained with the patient supine and the posterior aspect of the dorsiflexed heel placed on the image receptor, with the central ray angled 40o cephalad from the long axis of the foot (plantodorsal projection); alternatively, it can be obtained with the patient prone and the sole of the foot placed on the image receptor perpendicular to the tabletop with the central ray angled 40-45o caudally (dorsoplantar projection). A similar dorsoplantar projection with the patient standing on the image receptor was described by Harris and Beath in 1948. While the plantodorsal projection is often used in trauma, the dorsoplantar projection typically better shows the subtalar articulations. • Lateral view (left) shows calcaneus in profile and allows assessment of talus, subtalar joint, and calcaneocuboid joint. Axial view (right) obtained using dorsoplantar projection shows posterior and medial facets of subtalar joint (arrows), as well as alignment of heel Lateral view (left) shows slight deformity of posterior tuberosity of calcaneus and “double density”, concerning for fracture. Axial view (right) obtained using plantodorsal projection better shows fracture of posterior tuberosity (arrow), without evidence of extension to subtalar joint. CANALE VIEW The CANALE VIEW is a talar neck view described by Canale and Kelly for fracture evaluation. It is obtained by placing the ankle in maximal equinus with the foot pronated and internally rotated 450. The x-ray beam is centered on the talar neck and angled 15 degrees cephalad. Minimally displaced fractures of the talar neck may assume varus deformity at the fracture site that is not appreciated on routine radiographs. The Canale view is helpful for fracture detection as well as assessing degree of fracture angulation and displacement and adequacy of reduction Normal Canale view (above). The talar neck is well visualized. • • AP and lateral views (top left and center) show mild irregularity of lateral sesamoid bone, which is obscured by overlying bone. Tangential projection (top right) better shows increased density of lateral sesamoid indicating osteonecrosis (arrow). Lateromedial oblique radiograph of calcaneus shows calcaneal tuberosity (arrow), cuboid and sinus tarsus The REVERSE BRODEN (BRODEN II) is also useful for evaluating the subtalar joint, as well as the posterior talus, which is seen in profile • The foot is positioned as for an AP ankle radiograph and dorsiflexed, but rotated 45o laterally. The central ray is angled cephalad 15o to a point 2cm anterior and caudal to the medial malleolus. Normal Broden II view (above). Note that posterior process of the talus is seen in profile. • Posterior talar fracture fixation (arrow) is better assesed on Broden II view (right), in comparison with the lateral ankle radiograph (left). The ISHERWOOD method consists of radiographs of the subtalar joint obtained with medial rotation of the foot (for the anterior facet), medial rotation of the ankle (for the middle facet) and lateral rotation of the ankle (for the posterior facet). Normal Isherwood projections with medial rotation of the foot (left), medial rotation of the ankle (center) and lateral rotation of the ankle (right), demonstrating anterior, middle and posterior facets, respectively. • • WEIGHT-BEARING AND STRESS VIEWS WEIGHT-BEARING VIEWS are used to assess structural changes such as joint narrowing, subluxation and malalignment. Although considered “special” views, some practices recommend weight-bearing radiographs for all evaluations unless clinically contraindicated. Lateral view of AP view of foot obtained foot obtained with with patient patient weightweight-bearing bearing (left) better (top) better demonstrates demonstrates LisFranc disruption pes planus. (arrow). • STRESS VIEWS may be obtained to assess ligamentous stability in patients with suspected soft tissue injuries. Medial oblique (left) and lateral (central) radiographs show orthopaedic fixation of talus, but poor visualization of talar neck fracture. Canale view (right) better demonstrates talar neck fracture (arrow). LATEROMEDIAL OBLIQUE PROJECTION OF CALCANEUS This weight-bearing view of the calcaneus is obtained with the patient standing on the image receptor. The central ray is directed to the lateral malleolus lateromedially at a caudal angle of 45o. Broden I radiographs in 3 different patients showing intra-articular calcaneaus fracture (left), subtalar dislocation (center) and subtalar fusion (right). Posterior talar fracture is clearly seen on Broden II view (right), and not as well visualized on lateral ankle radiograph (left). • Routine radiographs of the TOES also include AP, lateral and oblique views. Enhanced detail and reduced superimposition of toes allows for better assessment of phalanges and interphalangeal joints than with routine foot radiographs AP, lateral and oblique foot radiographs (left, cropped to show forefoot) in kickboxer with great toe pain show no abnormality. Great toe radiographs (right) of same patient show avulsion fracture (arrow). SUBTALAR JOINT VIEWS The complex anatomy of the subtalar joint presents a diagnostic challenge that can require special views and advanced imaging for full evaluation. A variety of projections for depiction of the subtalar joint and hindfoot have been described, including the Broden and Isherwood methods. At our institution, the BRODEN views are ordered most frequently. • The foot is positioned as for an AP ankle radiograph, then dorsiflexed and rotated 45o medially. In our practice, the central ray is angled cephalad 20o to a point 2-3cm anterior and caudal to the lateral malleolus; views at multiple angles (10-40o) can also be obtained. • Allows visualization of the posterior facet of the subtalar joint and used to evaluate intra-articular calcaneus fractures and subtalar fusions. AP ankle radiographs without (left) and with (right) eversion stress demonstrate abnormal widening of medial joint space indicating deltoid ligament tear and unstable tibiotalar joint AP foot radiograph without stress (right) shows equivocal LisFranc disruption. Radiograph with stress (right) confirms TMT joint offset and LisFranc injury REFERENCES • • • • • • • ACR–SPR–SSR Practice Guideline for the Performance of Radiography of the Extremities Bontrager, KL. Textbook of radiographic positioning and related anatomy, 5th ed. 2001, Mosby, Inc. Slovenkai MP. Radiography of the ankle. Foot Ankle Clin 2000;5:149-164 Surgery of the Foot and Ankle, 8th Edition. Coughlin, Mann, Saltzman George Koulouris, MD, and William B. Morrison, MD. Foot and Ankle Disorders: Radiographic Signs. Seminars in Roentgenology Volume 40, Issue 4 , Pages 358-379, October 2005 Merrill’s Atlas of Radiographic Positioning and Procedures, 12th Edition. Frank, Long, Smith R. Harris and T. Beath. Etiology of Peroneal Spastic Flat Foot. Journal of Bone and Joint Surgery. June 1948