#{149}., - : : - #{149} #{149} -,.: CT Scanning of the Foot and Ankle: 1. Normal Anatomy

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1 1192 Pictorial Essay #{149}., - : : - #{149} #{149} -,.:.... : r# r -, S. I,,, I., CT Scanning of the Foot and Ankle: 1. Normal Anatomy Murray A. Solomon,1 Louis A. Gilula,2 Lawrence M. Oloff,3 Joan Oloff,4 and Terry Cornpton2 Computed tomographic (CT) scanning has become well established for its value in elucidating information in sites of complex anatomy, such as the spine and pelvis. The complex interdigitations between tarsal and metatarsal bones and the close approximation between these bones and adjacent softtissue structures (i.e., tendons and their sheaths) provide a challenge for diagnostic evaluation that so far can be answered only by CT. Many anatomic texts have some information about foot and ankle anatomy [1-8], but none supply a ready reference to explain ankle and foot anatomy in the multiple planes necessary in some cases to answer the presenting clinical question. In order to satisfy this need, we studied the correlative anatomy on CT, plain radiography, and gross sections in the modified coronal, axial (transverse), and sagittal planes. Clinical applications of CT in the foot and ankle are presented in Part 2 [9]. Materials and Methods Three fresh cadaver specimens of the ankle and foot were obtained from the Washington University Department of Anatomy. Each foot and ankle was radiographed using standard anteroposterior, lateral, and oblique projections for baseline information and to ensure that each specimen was grossly normal. Each foot was scanned at consecutive 2-mm intervals using a Siemens Somatom DR 3. The first foot was scanned in a slightly modified coronal plane with the distal tibia and fibula angled about 45#{176} with respect to the foot. This corresponds to a plane that can be obtained in most patients by Received September 5, 1985; accepted after revision December 23, Presented in part at the annual meeting of the American Roentgen Ray Society, Atlanta, April San Jose MRI Center, San Jose, CA placing the plantar aspect of the feet fiat on the table. (True coronal sections can be obtained by reformatting axial sections into the coronal plane.) A second foot was scanned in the transverse (axial) plane, which can be obtained normally in live subjects by placing the plantar aspect of the foot vertical or at right angles to the table. A third foot was scanned in the sagittal plane. It is not possible to scan most live patients in this plane. Sagittal reformations were also obtained from scans performed in the modified coronal plane. After CT scanning, each cadaver foot was sectioned into 6- to 7- mm-thick sections in the plane in which it had been scanned. Each Fig. 1 -Lateral radiograph indicating approximate levels ofcoronal sections in Figures 2-9 (left to right). 2 Mailinckrodt Institute of Radiology. Washington University School of Medicine, Kingshighway Blvd., St. Louis, MO Address reprint requests to L. A. Gilula. 3 Undell Hospital Podiatry Program, St. Louis, MO California College of Podiatry Medicine, San Francisco, CA AJR 146: , June x/86/ American Roentgen Ray Society

2 AJR:146, June 1986 CT OF THE FOOT AND ANKLE 1193 I DISTAL TIBIA 2 DISTAL FIBULA 3 POST. PROCESS OF TALUS 4 BoDY OF CALCANEUS 5 PoST TALOFIBULAR LIG. 6 PERONEUS BREIS I 7 PERONEUS LONGUS T. 8 TIBIALIS POST. I 9 FLEX. DIGITORUM LONGJS T. 10 FLEX. HALLUCIS LONGUS I II TIBIALISANT.T. 2 EXT. HALLUCIS LONGUS I 13 RETINACULUM 14 MEDIAL PLANTAR NEUROVASCULAR BUNDLE 5 GREAT SAPHENOUS V. 6 PERONEUS TERTIUS 7. 7 POST. FACET OF SUBTALAR Fig. 2.-Coronal plane, posterior process of talus. A, Photograph of section. B, CT scan, soft-tissue detail. C, Diagram of section. section was photographed, radiographed, and compared with the corresponding CT sections for elucidation of anatomic detail. Observations Seventeen clinically relevant sections comparing gross and radiographic to CT anatomy in three planes will be illustrated. Owing to lack of space, radiographs of specimens and CT scans at bone window settings will not be included. Corona! Plane The first series of anatomic sections and CT scans were obtained in the coronal plane (Fig. 1). The plantar aspect of a cadaver foot was firmly applied to the CT table. No angulation of the gantry was used. Eight clinically relevant sections are described below (Figs. 2-9). Figure 2 is at the level of the posterior process of the talus. The posterior process of the talus or an accessory bone, the Os tngonum, may be present at this level. There are three subtalar facets: anterior, middle, and posterior. In this section, the most posterior part of the posterior facet of the subtalar articulation is visible. The peroneus brevis and longus tendons are immediately inferior to the lateral malleolus. The tibialis ARTIC. 8 ANt TIBIAL 4.8 V. posterior and the flexor digitorum longus tendons are adjacent to the distal tibia. Figure 3 is about 1 cm anterior to Figure 2. The posterior facet is roughly horizontal in orientation, and it broadens as one moves antenad in the foot. At this level the talus is rectangular. Figure 4 is about 6 mm anterior to Figure 3. The posterior part of the sustentaculum, which is posterior to the middle facet of the subtalar articulation, is visible at this level. The peroneus brevis tendon is situated above the peroneus longus tendon, and both lie near the middle of the calcaneus. Occasionally, one may be able to identify a small bony projection, the peroneal process of the calcaneus, which is situated between the two tendons. The plantar muscles are well visualized at this level because of surrounding fat. Part of the deltoid ligament, which provides medial support, is present on this section. Figure 5 is less than 5 mm anterior to Figure 4. On this section both the middle facet of the subtalar articulation and the tarsal sinus are visible. The interosseous talocalcaneal ligament, which is present in the tarsal sinus, can occasionally be demonstrated with CT. The middle facet is the most common site of tarsal coalition, a form of congenital union that is at first cartilaginous but can ossify at puberty. The deltoid ligament is clearly demonstrated.

3 C SOLOMON ET AL. AJR:146, June 1986 I DISTAL TIBIA 2 TALUS 3 FIBULA- LAT. MALLEOLUS 4 CALCANEUS 5 POST TALOFIBULAR LIG. 6 PERONEUS BREVIS I 7 PERONEUS LONGUS I 8 TIBIALIS POST I. 9 FLEX. DIGITORUM LONGUS T. 10 FLEX. HALLUCIS LONGUS I II ABDUCTOR HALLUCIS M. 2 PLANTAR APONEUROSIS 3 TIBIALIS ANTI 4 EXT HALLUCIS LONGUS T. 6 M. 5 EXT DIGITORUM LONGUS I&M. 6 EXT RETINACULUM 17 CALCANEOFIBULAR L. 18 MEDIAL NEUROVASCULAR BUNDLE 19 GREAT SAPHENOUS V. 20 ANT TIBIAL A., N. 8 V. 21 FLEXOR RETINACULUM 22 PERONEUS TERTIUS I 23 P051 FACET OF SUBTALAR ARTIC. Fig. 3.-Coronal plane, middle of posterior subtalarfacet. A, Photograph of section. B, CT scan, soft-tissue detail. C, Diagram of section. I DISTAL TIBIA 2 TALUS 3 CALCANEUS 4 TIBIALIS ANT T 5 EXT HALLUCIS LONGUS I 6 EXT DIGITORUM LONGUS I 7 ANT TIBIAL A.,V. & N. 8 TIBIALIS POST T 9 FLEX. DIGITORUM LONGUS T 0 FLEX. HALLUCIS LONGUS T I PERONEUS BREVIS I 2 PERONEUS LONGUS T 13 MED. PLANTAR A.B N. 14 QUADRATUS PLANTAE M 5 LAT PLANTAR A.aN. 6 FLEX. RETINACULUM 7 ABDUCTOR HALLUCIS M. 8 FLEX. DIGITORUM BREVIS M. 9 ABDUCTOR DIGITI MINIMI M. 2OPERONEAL PROCESS OF THE CALCANEUS 21 DELTOID LIG. 22 GREAT SAPHENOUS V. 23 EXT RETINACULUM 24 PERONEUS TERTIUS I 25 POST FACET OF SUBTALAR ARTIC. 26 SUSTENTACULUM TALl Fig. 4.-Coronal plane, anterior aspect of posterior subtalar facet. A, Photograph of section. B, CT scan, soft-tissue detail. C, Diagram of section.

4 AJR:146,June 1986 CT OF THE FOOT AND ANKLE 1195 TALUS 2 SUSTENTACULUM TALl 3 CALCANEUS 4 INTEROS5EOUS TALOCALCANEAL LIG a TARSAL SINUS 5 TIBIALIS ANT I 6 EXT HALLUCIS LONGUS T 7 EXT DIGITORUM LONGUS I 8 DELTOID LID 9 TIBIALIS POST I 10 FLEX. GITORUM LONGUS I I I FLEX HALLUCI5 LONGUS I 2 QUADRATUS PLANTAE P.1 3 ABDUCTOR HALLUCIS M 14 FLEX. D4GITORUM BREVIS M 5 ABDUCTOR MINIMI M. 6 MED. PLANTAR A. a N. 17 LAT PLANTAR A.& N. 23 IS LAT TAWCALCAJE4L LID. 9 PERONEUS BREVIS I 20 PERONEUS LONGUS I 21 FLEX RETINACULUM 22 GREAT SAPHENOUS V. 23 PERONEAL TUBERCLE 24 PERONBJS TERTIUS I 25 MIDDLE FAcET, SUBTALAR JT. 26 DORSALIS PEDIS A., V. a N Fig. 5.-Coronal plane, middle subtalar facet, talocalcaneal ligament. A, Photograph of section. B, CT scan, soft-tissue detail. C, Diagram of section. I TALUS 2 SUSTENTACULUM TALl 3 CALCANEUS 4 GREAT SAPHENOUS V 5 TIBIALIS ANT I 6 EXT HALLUCIS LONJ5 I. 7 EXT DIGITORUM LONGUS I 8 DELTOID UG 9 TIBIALIS POST I 10 FLEX DIGITORUM LONGUS I II FLEX HALLUCISLONGUST 2 PERONEUS BREVIS I 13 PERONEUS LONGUS I 14 QUADRATUS PLANTAE M 5 ABDUCTOR HALLUCIS M. 6 FLEX. DIGITORUM BREVIS M 17 ABDUCTOR DIGIII MINIMI M 18 MED. PLANTAR SN. A. 19 PERONEUS TERTIUS 20 INTEROSSEUS TALOCALCANEAL LID. (TARSAL SINUS) 21 LAT TALOCALCANEAL UG. 22 DELTOID LID 23LAT PLANTAR N,A,V 24 DORSALIS PEDIS A S V 25 MIDDLE SUBIALAR FACET ARTIC. OF Fig. 6.-Coronal plane, anterior aspect of middle subtalar facet. A, Photograph of section. B, CT scan, soft-tissue detail. C, Diagram of section. The anterior aspect of the middle facet is demonstrated in Figure 6. The tarsal sinus and interosseous talocalcaneal ligament are again visualized. At this level, the calcaneus has only slightly more cross-sectional area than the talus. The neck between the sustentaculum tali and the body of the calcaneus is narrow and can be fractured with a comminuted fracture of the calcaneus. Figure 7, about 1 cm anterior to Figure 6, is at the level of the anterior facet of the subtalar articulation. Rarely, this is a site of tarsal coalition. In this section, the head of the talus

5 C 1196 SOLOMON ET AL. AJR:146, June 1986 I TALUS 2 CALCANEUS 3 ANT FACET OF SUBIALAR JI 4 GREAT SAPHENOUS V. 5 TIBIALIS ANT I 6 EXT HALLUCIS LONGUS I 7 EXT DIGITORUM LONGUS I 8 TIBIALIS POST I 9 FLEX. DIGITORUM LONGUS I 0 FLEX. HALLUCIS LONGUS I I I ABDUCTOR HALLUCIS M. 2 FLEX. DIGITORUM BREVIS M 13 ABDUCTOR DIGITI MINIMI M. 4 PERONEUS LONGUS I 5 PERONEUS BREVI5 I 16 DELTOID LID Fig. 7.-Coronal plane, anterior subtalar facet. A, Photograph of section. B, CT scan, soft-tissue detail. C, Diagram of section. 7 MED. PLANTAR A.& N. 18 LAT PLANTAR A.,N. B V. 19 PLANTAR APONEUROSIs 2OPERONEUS TERTIUS I 2IDORSALIS PEDIS A&V. I HEAD OF TALUS 2 NAVICULAR 3 CALCANEUS - ANT PROCESS 4 CUBOID 5 GREAT SAPHENOUS V 6 IIBIALIS ANT I 7 EXT HALLUCIS LONGUS I 8 EXT DIGITORUM LONGUS I 9 TIBIALIS POST I 10 FLEX DIGITORUM LONGUS AND FLEX HALLUCIS LONGUS TS II PERONEUS BREVIS I 12 PERONEUS LONGUS T (CUBOID TUNNEL) 13 POSITION OF MED PLANTAR NA. 14 POSITION OF LAT PLANTAR NA. 15 QIJADRATUS PLANTAE N 6 ABDUCTOR HALLUCIS N 7 FLEX DIGITORUM BREVIS N 18 ABDUCTOR DIGITI MINIMI N 19 LONG. PLANTAR LIG. 2OEXT RETINACULUM 21 EXT DIGITORUM BREVIS N. 22 CALCANEOCUBOID LIG. 23 PLANTAR APONEUROSIS 24 DORSALIS PEDIS A., V a N Fig. 8.-Coronal plane, talonavicular articulation. A, Photograph of section. B, CT scan, soft-tissue detail. C, Diagram of section. has an oval configuration, which technically is an elliptical paraboloid. Figure 8 is about 1.5 cm anterior to Figure 7. The head of the talus is situated superiorly, and there is a rim of navicular bone beneath the talus. Thus this talonavicular articulation has the appearance of an egg in a cup. An anterior projection of the calcaneus, the anterior process, is visible on this section. The last coronal section, illustrated in Figure 9, is at the level of the sesamoid bones of the first metatarsal. This level corresponds to the ball of the foot, which is a common site of ulceration, soft-tissue infection, and osteomyelitis in diabetes. The tendon of the flexor hallucis longus muscle is situated between the medial and lateral sesamoids of the first metatarsal. Above each metatarsal is an extensor hood apparatus.

6 C MR:146, June 1986 CT OF THE FOOT AND ANKLE 1197 Transverse (Axial) Plane Six sections in the axial or transverse plane are described here. Figure 1 0 indicates the level at which each transverse section was obtained. Figure 1 1 demonstrates a section of the distal tibia and fibula just superior to the malleoli. At this level, the achilles tendon has a crescentic or semilunar configuration and is well outlined by surrounding fat. The soleus muscle in some cases will extend to this level and can be seen just anterior to the Achilles tendon. Anterior to the distal tibia, several tendons are evident. From medial to lateral, they are the tibalis anterior, extensor hallucis longus, extensor digitorum longus, and peroneus tertius tendons. The dome of the talus and the medial, lateral, and postenor malleoli are demonstrated on the section in Figure 12. The posterior malleolus, which can be a site of occult fracture, is actually the posterior part of the distal tibia. A dense band, the posterior tibiofibular ligament, joins the postenor and lateral malleoli. The flexor tendons are in close proximity to the posterior aspect of the distal tibia. The section illustrated in Figure 1 3 was obtained more than 2 cm below that in Figure 1 2. The talus has a rather unusual configuration in this projection, and the neck of the talus appears relatively narrow. The superior aspect ofthe posterior facet of the subtalar articulation at this level possesses an 4 S_JND S THIRD METATARSAL 6 FOURTH METATARSAL 7 FOURTH PROX. PHALANX 8 FIFTH PROX PHALANX 9 EXT HALLUCIS LONGUS T 0 EXT. HALLUCIS BREVIS T II DORSALIS PEDIS A.,V. (2 EXT DIGITORUM LONGUS AND BREVIS I (SECOND TOE) 3 EXT DIGITORUM LONGUS AND BREVIS T (THIRD TOE) 4 THIRD AND FOURTH INTEROSSEOUS DORSALIS MS. IS ABDUCTOR HALLUCIS M. 6 FLEX HALLUCIS LONGUS I 17 ADDUCTOR HALLUCIS M 18 FLEX DIGITORUM LONGUS M. 9 TRANSVERSE METATARSAL LID. 20 EXT. HOOD APPARATUS 21 PREMETATARSAL SPACE 22 COMMON PLANTAR DIGITAL N. Fig. 9.-Coronal plane, sesamoids of first metatarsal. A, Photograph of section. B, CT scan, soft-tissue detail. C, Diagram of section. L configuration. The talonavicular articulation is well profiled in the axial plane, as are the articulations between the three cuneiforms and the navicular. The middle facet of the subtalar articulation slants about 450 with respect to the plantar aspect of the foot. The posterior part of the middle facet is more superiorly situated than its anterior aspect. Because of this 45#{176} orientation, the middle articular facet can be well demonstrated on either a coronal or transverse section. Figure 1 4 was obtained at the superior aspect of the calcaneocuboid articulation. The first three metatarsotarsal articulations and part of the plantar calcaneonavicular (spring) ligament are demonstrated at this level. A final transverse section is portrayed in Figure 1 5. It is inferior to the talus and navicular and profiles the inferior aspect of the calcaneocuboid joint. The retrocalcaneal bursa, which exists between the posterior aspect of the calcaneus and the Achilles tendon, is demonstrated at this level. Sagittal Plane At present, it is usually not possible to obtain CT sections in the true sagittal plane. Although a cadaver foot was scanned in the sagittal plane at 2-mm intervals, those images will not be used here. Rather, sagittal reformations, which

7 1198 SOLOMON ET AL. AJR:146, June 1986 can be generated on most modern CT scanners, will be presented. In Figure 1 6 an anatomic section and sagittal CT reformatins along the first ray are presented. The sustentaculum tali and middle articular facet are clearly demonstrated. The dome Fig. 10.-Lateral radiograph indicating approximate levels of transverse (axial) CT sections in Figures (left to right). of the talus can be evaluated in this plane, as can the following articulations: talonavicular, navicular-medial cuneiform, and medial cuneiform-first metatarsal. The plantar fascia and musculature can be reviewed in their entire extent with sagittal reformations. A sagittal reformation through the second ray is illustrated in Figure 1 7. The posterior facet of the subtalar articulation and the most lateral aspect of the middle facet are profiled at this level. The Achilles tendon inserts along the posterior aspect of the calcaneus. The lateral aspect of the talonavicular and navicular-middle cuneiform articulations are visualized. The final figure, Figure 1 8, is an anatomic section and sagittal reformation through the third ray of the foot. Part of the posterior facet and the calcaneocuboid articulation are shown to good advantage. Conclusions There are now a number of recognized dinical applications for CT scanning in the foot and ankle [9]. Proper interpretation of these images requires a thorough knowledge of anatomy or ready access to such anatomy in the coronal, axial (transverse), and sagittal planes. In preparation for clincal work, we performed correlative studies of CT scans, radiography, and anatomic sections of cadaver feet. Clinically relevant CT and anatomic sections are presented. Although CT scans at bone window settings are not included, we believe it is important to always include both bone and soft-tissue window settings with foot CT in order not to miss significant pathology. ACKNOWLEDGMENTS We thank Roy Peterson, Gail King, and Bob Feidhaus for support with anatomic material; Norman Hente, Cramer Lewis, and Vickie Friedman for photography; John Grzeskowiak for radiography; and Sharon Keathley and Unda Macker for manuscript preparation. I DISTAL TIBIA 2 DISTAL FIBULA 3 GREAT SAPHENOUS V 4 IIBIALI5 ANT T 5 EXT HALLUCIS LONGUS I a N 6 EXT DIGITORUN LONGUS T B N 7 IIBIALI5 POST I 8 FLEX DIGIIORUN LONGUS I 9 PERONEUS LONGUS (LI AND BREVIS IBI TS 10 FLEX I4ALLUCIS LONGUS N I I FLEX HALLUCIS LONGUS I 12 FAT IPREACHILLES SPACEI 3 ACHILLES T 14 ANT IIBIAL A IDORSALIS PEDIS) IS POST IIBIAL A., V. 16 POSITION OF SMALL SAPHENOUS V I? POSITION OF SOLEUS M INAY NOT EXTEND THIS INFERIORLYI IS PERONEUS TERTIUS T 19 ANT TIBIOFIBULAR L 20 POST TIBIO-FIBULAR 21 FLEX RETINACULUN 22 POST PERONEAL VESSELS 23 TIBIO FIBULAR SYNDESMOSIS Fig Transverse plane, distal tibla and fibula. A. Photograph of section. B, CT scan, soft-tissue detail. C, Diagram of section. C 24 DEEP PERONEAL N. 25 TIBIAL N 26 SURAL N. 27 SAPHENOUS N 28 SUPERFICIAL PERONEAL N. 29EXT. RETINACULUN

8 AJR:146, June 1986 CT OF THE FOOT AND ANKLE 1199 C Photograph of section. B, CT scan, soft-tissue detail. C, Diagram of section. I NAVICULAR 2 BODY OF TALUS 3 NED MALLEOLUS 4 POST NALLEOLUS 5 LAT NALLEOLUS 6 POST TIBIOFIBULAR LIG 7 ANT TALOFIBULAR LID 8 POSITION OF GREAT SAPHENOUS V. 9 IIBIALIS ANT I 10 EXT HALLUCIS LONGUS I S N I I EXT DIGIIORUM LONGUS I S M 12 PERONEUS BREVIS I 13 PERONEUS LONGUS I 14 POST TIBIALIS I 15 FLEX DIGITORUM LONGUS I 16 NEUROVASCULAR BUNDLE IT FLEX HALLUCIS LONGUS I 8 POSITION OF SURAL N 19 POSITION OF SMALL SAPHENOUS V 20 FAT I PREACHILLES SPACEI 21 ACHILLES I 22 DELTOID LID 23 FLEX RETINACULUN 24 LAT a NED. PLANTAR N 25 EXT RETINACULUM 26 TALONAVICULAR UG Fig. 12.-Transverse plane, posterior malleolus oftibia. A, Photograph of section. B, CT scan, soft-tissue detail., Diagram of section. I SECOND METATARSAL BASE 2 MED CUNEIFORM 3 MIDDLE CUNEIFORM 4 LAT CUNEIFORM 5 NAVICULAR 6 HEAD OF TALUS 7 NECK OF TALUS 8 BODY OF TALUS 9 CALCANEUS 10 TIBIALIS ANT I II EXT HALLUCIS LONGUS I 12 POSITION OF EXT DIGITORUM LONGUS IS 3 INTEROSSEOUS TALOCALCANEAL LID 14 TIBIALIS POST I 5 FLEX. DIGITORUM LONGUS I 16 POST TIBIAL A. S V. IT FLEX. HALLUCIS LONGUS I 18 MEDIAL PLANTAR N. 19 PRE-ACHILLES SPACE 2OHILLES TENDON 21 SMALL SAPHENOUS V. 22 LAT. PLANTAR N. 23 PERONEUS BREVIS I 24 PERONEUS LONGUS I 25 GREAT SAPHENOUS V. 26 DELTOID LID. 27SURAL N. 28 DORSALIS PEDIS BRANCHES 29 EXT. DIGITORUM BREVIS N.

9 C I FIRST METATARSAL BASE 2 SECOND METATARSAL BASE 3 THIRD METATARSAL BASE 4 MED CUNEIFORM 5 MIDDLE CUNEIFORM 6 LAT CUNEIFORM 7 NAVICULAR 8 CUBOID 9 TALUS 0 CALCANEUS II IIBIALIS ANT I. 12 EXT HALLUCIS LONGUS I. 13 EXT DIGITORUM LONGUS IS. 14 PERONEUS BREVIS I (5 PERONEUS LONGUS I 6 POSITION OF SURAL N. 17 SPRING LID 18 TIBIALIS POST I (9 FLEX. DIGITORUM LONGUS I 20 FAT (PREACHILLES SPACE) 21 ACHILLES I 22 FLEX. HALLUCIS LONGUS M 23 MED. B LAI PLANTAR N., A. B V. 24 SMALL SAPHENOUS V. Fig. 14.-Transverse section, calcaneocuboid articulation. A, Photograph of section. B, CT scan, soft-tissue detail. C, Diagram of section. I FIRST METATARSAL 2 SECOND METATARSAL 3 THIRD METATARSAL 4 FOURTH METATARSAL 5 FIFTH METATARSAL 6 MED. CUNEIFORM 7 LAT. CUNEIFORM 8 CUBOID 9 SUSTENTACULUM TALl (0 BODY OF CALCANEUS II EXT DIGITORUM TS. 2 PERONEUS BREVIS I. 3 PERONEUS LONGUS I 14 QUADRATUS PLANTAE M. 5 POSITION OF LAT PLANTAR N.,A.&V. 6 POSITION OF MED. PLANTAR N.,A.& V. 7 ABDUCTOR HALLUCIS M. 8 FLEX. DIGITORUM LONGUS I 19 FLEX. HALLUCIS LONGUS T. 20 DEEP PLANTAR A. 21 TIBIALIS ANT M. 22 MEDIAL CALCANEAL N. 23 RETROCALCANEAL BURSA 24 ACHILLES I. 25 TIBIALIS POST. I. C Fig. 15.-Transverse section, medial cuneiform-first metatarsal articulation. A, Photograph of section. B, CT scan, soft-tissue detail. C, Diagram of section.

10 MR:146, June 1986 CT OF THE FOOT AND ANKLE 1201 I DISTAL TIBIA 2 TALUS 3 MIDDLE SUBTALAR JOINT 4 SUSIENIACULUM TALl 5 NAVICULAR 6 MED CUNEIFORM 7 FIRST METATARSAL 8 SESAMOID BONE 9 FIRST PROX PHALANX 10 FIRST DISTAL PHALANX II TIBIALIS POST I 12 FLEX. DIGIT LONGUS I 13 POST TIBIAL A, N S V 14 FLEX. HALLUCIS LONGUS I I 5 PLANTAR CALCANEONAVICULAR LID. (SPRING LID.) 16 TIBIALIS ANT I I7 EXT HALLUCIS LONGUS I IS FLEX. HALLUCIS BREVIS N. 9 ABDUCTOR HALLUCIS M. 2OMEDIAL PLANIAR A.,V.&N. 21 IIBIALIS POST T. 22 PLANTAR DIGITAL N. Fig. 16.-Sagittal plane, first ray, sustentaculum tali. A, Photograph of section. B, Transverse plane for reconstructed image C. C, Reconstructed CT section, soft-tissue window. D, Diagram of section.

11 1202 SOLOMON ET AL. AJR:146, June 1986 C D I I TIBIA 2 TALUS 3 CALCANEUS 4 POST SUBTALAR JOINT 5 ANT AND MIDDLE FACETS OF THE SUBTALAR JOINT 6 NAVICIJLAR N. 7 MID CUNEIFORM B SEC. METATARSAL BASE 9 SEC METATARSAL HEAD 10 VASCULAR CALCIFICATION II PROX PHALANX 2 DISTAL PHALANX 3 ACHILLES T 14 RETROCALC ISPLANTAR 1 IS EXT HALLU 5 LONGUS I..11 RUN LONGUS I X. t.ucis LONGUS IS N. ACHII.ES FAT,..)UCTOR DIGITI NINIMI N. 22 FLEX. DIGITORUN BREVIS N. 23FLEX ACCESSORIUS N T4LAT PLANTAR N,A.SV. 5 TIBIALIS POST I FLEX. HALLUCIS BREVIS T 7NED. PLANTAR N,A.SV 29 QUADRATUS POSTPLANTAE N N Fig. 17.-Sagittal plane, second ray, posterior subtalar facet. A, Photograph of section. B, Transverse plane for reconstructed image C. C, Reconstructed CT section, soft-tissue window. D, Diagram of section.

12 AJR:146, June 1986 CT OF THE FOOT AND ANKLE 1203 I TIBIA 2 TALUS 3 CALCANEUS 4 POST SUBTALAR JOINT 5 CUBOID 6 LAT. CUNEIFORM 7 THIRD METATARSAL 8 THIRD PROX. PHALANX 9 THIRD MIDDLE PHALANX 0 THIRD DISTAL PHALANX II FLEX HALLUCIS LONGUS M 2 ACHILLES I 13 PREACHlLLES FAT TRIANGLE 14 PLANTAR APONEUROSIS 15 ANKLE JOINT CAPSULE 6 EXT DIGITORUM LONGUS I 17 SHORT PLANTAR LIG. 8 LONG PLANTAR LIG. 19 LAT PLANTAR A 20 FLEX. DIGITORUM BREVIS M. 21 INTEROSSEOUSM. Fig Sagittal plane, third ray. calcaneocuboid articulation. A, Photograph of section. B, Transverse plane for reconstructed image C. C, Reconstructed CT section, soft-tissue window. 0, Diagram of section. REFERENCES 1. Bassett DL. A stereoscopic atlas of human anatomy, section VII: The lower extremity. Portland: Sawyer s, 1962:204, Resnick 0. Radiology of the talocalcaneal articulations. Radiology 1974;111 : Keifer SA, Heitzman ER. An atlas of cross sectional anatomy. Philadelphia: Harper & Row, Ledley RS, Huang HK, Mazziotta JC. Cross sectional anatomy: an atlas for computerized tomography. Baltimore: Williams & Wilkins, Bo WJ, Meschan I, Krueger WA. Basic atlas of cross sectional anatomy. Philadelphia: Saunders, 1980: McMinn RMH, Hutchings AT, Logan BM. Color atlas of foot and ankle anatomy. Norwalk: Appleton Century Crofts, 1982: Wagner M, Lawson TL. Segmental anatomy, applications to clinical anatomy. New York: Macmillan, 1982: Sarrafian SK. Anatomy of the foot and ankle. Philadelphia: Lippincott, Solomon MA, Gilula LA, Oloff LM, Oloff J. CT scanning of the foot and ankle: 2. Clinical applications and review ofthe literature. AJR 1986;146:12O4-1214

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