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Walter 2018
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  AJR:211, August 2018 1 tion, in part because of unfamiliarity with typical imaging ndings [9, 10]. Untreated midtarsal sprains may cause instability and chronic pain; therefore, recognition of mid - tarsal sprains by clinicians and radiologists is important [9, 11].In this article, we discuss Chopart joint anatomy, pathomechanisms of midtarsal sprains, clinical implications, and radio - graphic and cross-sectional imaging ndings, with a focus on MRI. Other injuries affecting the Chopart joint complex, such as fracture-dislocation, will be briey described. Normal Anatomy and MRI of the Chopart Joint Complex The Chopart joint complex, also known as the midtarsal or transverse tarsal joint, is lo - cated between the hindfoot and midfoot and consists of the talocalcaneonavicular and calcaneocuboid joints. The joint complex is named after François Chopart, born in Par - is in 1743, who is the surgeon credited with describing and pioneering an anatomically and functionally expedient method for treat - ing gangrene of the foot by disarticulation at the transverse tarsal joint. The rst descrip - tion of this operation was published in 1792, 3 years before his death [12]. Chopart Joint Function The talocalcaneonavicular and calcaneo - cuboid joints are regarded as a unit despite the distinct functions provided by each. The talus and navicular form the proximal, exi - Imaging of Chopart (Midtarsal)  Joint Complex: Normal Anatomy and Posttraumatic Findings William R. Walter 1 Anna Hirschmann 2 Monica Tafur 3 Zehava S. Rosenberg 1 Walter WR, Hirschmann A, Tafur M, Rosenberg ZS 1 Department of Radiology, Musculoskeletal Division, NYU Langone Orthopedic Hospital, 301 E 17th St, 6th Fl, New York, NY 10003. Address correspondence to W. R. Walter (William.Walter@nyumc.org). 2 Clinic of Radiology and Nuclear Medicine, University of Basel Hospital, Basel, Switzerland. 3 Joint Department of Medical Imaging, University of Toronto, Toronto, ON, Canada. Musculoskeletal Imaging ã Review AJR   2018; 211:1–100361–803X/18/2112–1© American Roentgen Ray Society M idtarsal sprains are dened as a spectrum of soft-tissue and osse - ous injuries at the Chopart joint complex involving the talocalca - neonavicular and calcaneocuboid joints. Typically, midtarsal sprains result from low-energy, inversion-type ankle trauma. They are distinct from Chopart joint fracture-dis -locations, which result from high-energy trauma such as motor vehicle crashes.Midtarsal sprains may affect the support - ing ligaments along the talocalcaneonavic - ular and calcaneocuboid joints. The most commonly injured ligaments are the dor - sal calcaneocuboid, bifurcate, and dorsal ta - lonavicular ligaments and the spring liga - ment complex, with plantar ligament injuries thought to be signicantly less frequent [1–4]. The range of osseous injuries includes contu - sions, avulsions, or impaction fractures of the anterior process of the calcaneus, talar head, cuboid bone, and navicular bone [2, 4, 5].The true incidence of midtarsal sprains is uncertain, with disparate values reported in the literature ranging from 5.5% to 33% of inversion ankle injuries [1, 6, 7], where - as midfoot fracture-dislocations are consid - erably less common, estimated to occur at a frequency of 3.6/100,000 per year [8]. In clinical and radiographic evaluations, mid - tarsal sprains are frequently underdiagnosed and are missed at initial evaluation in up to 41% of cases, resulting in delayed treatment [1]. Recent estimates indicate that 22–40% of midtarsal sprains are missed at presenta - Keywords:  ankle trauma, calcaneocuboid joint, Chopart joint, midtarsal sprain, talonaviculardoi.org/10.2214/AJR.17.19310Received November 17, 2017; accepted after revision January 11, 2018. OBJECTIVE.  The objective of this article is to review the normal anatomy and posttrau - matic ndings of the Chopart joint complex. Key imaging features of the normal ligaments and patterns of ligamentous and osseous injuries are discussed. CONCLUSION.  Traumatic midtarsal injuries, particularly midtarsal sprain, are often overlooked clinically and on imaging but are relatively common and typically are associated with inversion ankle injuries. Radiologists should be familiar with Chopart joint anatomy and the imaging features of midtarsal injuries because early diagnosis may help optimize clinical management. Walter et al.Chopart Joint ComplexMusculoskeletal ImagingReview    A  m  e  r   i  c  a  n   J  o  u  r  n  a   l  o   f   R  o  e  n   t  g  e  n  o   l  o  g  y  2 AJR:211, August 2018  Walter et al. ble part of the medial column of the foot, and the calcaneus and cuboid form the proximal, more rigid segment of the lateral column. The Chopart joint complex allows the hindfoot to pivot while the forefoot remains still with in - version and eversion. The complex locks on heel inversion, stabilizing the midfoot during the push-off phase of gait [13, 14]. The Talocalcaneonavicular Joint The talocalcaneonavicular joint, also known as the talonavicular joint, is composed of the talar head, the posterior surface of the navic - ular, and the anterior process of the calcane - us. Extracapsular ligaments of the sinus tarsi and tarsal canal guide motion of the calcaneo - navicular complex, a functional unit moving around the talus. Any motion between the cal - caneus and the talus occurs at the anterior and posterior subtalar joints [14, 15].Ligaments of the talonavicular joint can be divided into ligaments of the acetabu - lum pedis (spring ligament and calcaneona - vicular component of bifurcate ligament), ta - localcaneal ligaments (lateral, medial, and posterior talocalcaneal, interosseous, and cervical ligaments), and dorsal talonavicu - lar ligament (Fig. 1). The talocalcaneal lig - aments will not be discussed, because they pertain to the subtalar joint.  Ligaments of the acetabulum pedis —The head of the talus articulates with the acetab - ulum pedis, which is formed by the navicu - lar anteriorly, the anterior and middle calca - neal facets and the plantar components of the spring ligament complex inferiorly, the superomedial component of the spring lig - ament complex medially, and the calcaneo - navicular component of the bifurcate liga - ment laterally (Fig. 1). The acetabulum pedis adapts to talar head displacement and rota - tion [14]. The spring ligament complex —The spring (calcaneonavicular) ligament complex is composed of the superomedial, medioplan - tar oblique, and inferoplantar longitudinal components (Fig. 1). The superomedial com - ponent is triangular or hammock-shaped, coursing anteromedially from its srcin at the anteromedial aspect of the sustentaculum tali and attaching at the superomedial navic - ular tuberosity. Its inner surface is brocar - tilaginous, resembling an articular surface. Loose connective tissue is interposed be - tween the superomedial component and the posterior tibial tendon, allowing gliding be - tween the two structures. The medioplantar oblique component srcinates from the cor - onoid fossa of the calcaneus, a notch in the anterior process of the calcaneus. It courses medially and obliquely, attaching at the me - dioplantar navicular, just below its tuberos - ity (Fig. 2A). The short and thick inferoplan - tar longitudinal component srcinates in the coronoid fossa, anterolateral to the medio - plantar oblique component, extends forward, and fans out onto the navicular beak [15, 16] (Fig. 2A).The superomedial component is best shown on coronal and axial ankle MR im - ages and on short- and long-axis midfoot MR images [17–19]. It is an intermedi - ate- to low-signal-intensity band on T1- and T2-weighted MRI sequences. The medio - plantar oblique component is best seen on axial ankle or long-axis midfoot planes and has a striated appearance (Fig. 2A). The me - dioplantar oblique component is usually not seen on a single sagittal image because of its oblique course. The inferoplantar longi - tudinal component is best seen on axial and coronal ankle MR images and on long- and short-axis midfoot images, has intermediate to low signal intensity on T1-weighted se - quences, and has variable signal intensity on T2-weighted sequences [20] (Fig. 2A). The bifurcate ligament  —The bifurcate lig- ament consists of the lateral calcaneonavic - ular and medial calcaneocuboid ligaments, supporting the talonavicular and calcaneocu - boid joints (Fig. 1). It is located anterior to the cervical ligament and the srcin of the exten - sor digitorum brevis muscle. The lateral cal - caneonavicular ligament extends between the intermediary tubercle of the calcaneus and the posterosuperior aspect of the lateral margin of the navicular (Figs. 1 and 2B). The medial calcaneocuboid ligament extends between the intermediary tubercle, slightly lateral to the lateral calcaneonavicular ligament, and the dorsum of the cuboid, inserting approximate - ly 15 mm anterior to the calcaneocuboid joint [15] (Figs. 1 and 2C). The lateral calcaneona - vicular ligament was visualized in all speci - mens and imaging planes in a cadaveric study by Melão and colleagues [19], whereas the medial calcaneocuboid ligament was less con - sistently shown, best seen on coronal and sag - ittal ankle MR images or short-axis and sag - ittal foot MR images in another study [4]. On non–fat-saturated MRI sequences, the com - ponents are thin, low- to intermediate-signal-intensity structures highlighted by adjacent fat [19, 20] (Figs. 2B and 2C).  Dorsal talonavicular ligament  —The dor - sal talonavicular ligament is a capsular thick - ening connecting the dorsal aspect of the talar neck and the dorsal surface of the na - vicular bone [15] (Fig. 1). It is hypointense on T1- and T2-weighted MRI sequences and is best visualized on sagittal MR images [19, 20] (Fig. 2D). The Calcaneocuboid Joint The calcaneocuboid joint is formed by the quadrilateral facets of the calcaneus and A Fig. 1— Anatomy of Chopart joint complex. A,  Schematic drawing of supporting ligaments of Chopart joint depicts dorsal talonavicular ligament (TN), bifurcate ligament (calcaneonavicular and calcaneocuboid components), and dorsal calcaneocuboid ligament (DCC; dorsal and lateral bundles). Short and long plantar ligaments (not shown) stabilize plantar aspect of joint. B,  Schematic drawing of spring ligament complex depicts medioplantar oblique (MPO), inferoplantar longitudinal (IPL), and superomedial (SM) components. (Reprinted from Magnetic Resonance Imaging Clinics of North America , Vol. 25/edition 1, Tafur M, Rosenberg ZS, Bencardino JT. MR Imaging of the Midfoot Including Chopart and Lisfranc Joint Complexes, Pages 95–125, Copyright 2017, with permission from Elsevier) [20]. B    A  m  e  r   i  c  a  n   J  o  u  r  n  a   l  o   f   R  o  e  n   t  g  e  n  o   l  o  g  y  AJR:211, August 2018 3 Chopart Joint Complex cuboid bone. The calcaneus articular sur - face is saddle-shaped, forming a groove di - rected inferomedially. At its posteromedial end is the calcaneal coronoid fossa, which articulates with the beak of the cuboid. The posterior surface of the cuboid is also sad - dle-shaped, with the cuboid beak lodging in the calcaneal coronoid fossa during forefoot exion and adduction [15]. Four ligaments connect the calcaneus and cuboid: the me - dial calcaneocuboid ligament (component of bifurcate, described in the previous section), the dorsal calcaneocuboid ligament, and the plantar calcaneocuboid ligaments (Fig. 1). The dorsal calcaneocuboid ligament  — The dorsal calcaneocuboid ligament, also called the dorsolateral calcaneocuboid lig - ament, has been described as a thin, broad band between the superolateral aspect of the anterior process of the calcaneus, lateral to the medial calcaneocuboid component of the bifurcate ligament, and the dorsal surface of the cuboid (Fig. 1). However, in a cadaveric study by Dorn-Lange and colleagues [21], al - most half of the cases showed morphologic variation including a V-shaped ligament, a meniscoid band, or two or more separate lig - aments (dorsal and lateral calcaneocuboid ligaments). The normal dorsal calcaneocu - boid ligament is often difcult to identify on sagittal images because of its small size and volume-averaging effects with the overlying extensor digitorum brevis muscle. Melão and colleagues [19] found dorsal calcaneocuboid ligaments in all specimens and that the dorsal calcaneocuboid ligament was better shown on coronal ankle MR images or short-axis midfoot MR images. The dorsal calcaneocu - boid ligament is also well depicted on axial MR images of the ankle [4, 20] (Fig. 2A). The plantar calcaneocuboid ligaments — The long and short plantar ligaments form the supercial and deep components of the inferior calcaneocuboid ligament, respec - tively. The long plantar ligament srcinates from the inferior surface of the calcaneus between the posterior and anterior tubercles and divides distally into at least two bands that attach to the cuboid (lateral band) and variably to the metatarsal bases (medial band). When present, the medial band forms the roof of the peroneus longus tunnel [22]. On MRI, the long plantar ligament has ho - mogeneous to striated low signal intensity and is well depicted on all ankle and midfoot planes [19] (Fig. 2C). The short plantar liga -ment srcinates at the plantar surface of the calcaneus, anterior to the long plantar liga- ment. It extends anteromedially to the plan - tar surface of the cuboid, proximal to the CA Fig. 2— MRI anatomy of Chopart joint ligaments in different patients. Insets show level ( lines  ) of each image. A, Axial   T1-weighted image of 37-year-old man/woman. Lateral band of dorsal calcaneocuboid ligament ( arrowhead  ) is seen adjacent to extensor digitorum brevis muscle ( asterisk  ). Note also inferoplantar longitudinal ( short arrow  ) and medioplantar oblique ( long arrow  ) components of spring ligament complex. B and  C, T1-weighted images of 26-year-old man/woman show that lateral calcaneonavicular ligament ( arrowhead  , B ) and more laterally located medial calcaneocuboid ligament ( wavy arrow  , C ) form bifurcate ligament. Long plantar ligament ( curved arrow  , C ) typically has striated appearance. D,  Fat-saturated proton density–weighted image of 51-year-old man/woman. Talonavicular ligament ( arrow  ) reinforces talonavicular joint capsule. E,  T1-weighted image of 44-year-old man/woman. Short plantar ligament ( arrow  ) typically has striated appearance. EDB    A  m  e  r   i  c  a  n   J  o  u  r  n  a   l  o   f   R  o  e  n   t  g  e  n  o   l  o  g  y  4 AJR:211, August 2018  Walter et al. peroneus longus tunnel. The short plantar ligament appears striated and of intermedi - ate signal intensity in all ankle and midfoot planes on MRI [19, 20] (Fig. 2E). Midtarsal Injuries: Pathomechanisms Midtarsal sprains reect a spectrum of in -  juries resulting from low-energy trauma of the Chopart joint complex and encompass both soft-tissue capsuloligamentous injuries and bony injuries, including ligament tears or sprains as well as avulsion or impaction fractures, depending on the severity of the trauma and the mechanism-dependent forc - es involved. Although midtarsal sprains most commonly result from ankle inversion, ever - sion injuries are also a possible mechanism. Each mechanism results in a distinct inju - ry pattern at the Chopart joint complex, and recognition of these patterns is critical for ra- diologists to propose a unied, accurate di - agnosis of a midtarsal sprain (Table 1). Inversion Midtarsal Sprains Most midtarsal sprains are thought to oc - cur as a result of an inversion injury (Fig. 3A), resulting in distraction forces across the lateral and dorsolateral aspects of the cal - caneocuboid joint [1, 2, 6] and, if the mag - nitude of forces involved are sufciently se - vere, impaction along the medial column of the foot. Distraction injuries often result in avulsion fractures in combination with a tear or sprain of the ligament stabilizing the joint. Impaction injuries frequently cause contusion, osteochondral injury, or impaction fractures at the involved bony interfaces; occasionally, ligamentous contusion can also accompany impaction injuries.Common injuries in this setting include avulsion of the dorsal calcaneocuboid liga - ment and calcaneocuboid component of the bifurcate ligament as well as extensor digi - torum brevis srcin avulsion. Impaction in -  juries medially may produce contusions or fractures of the talar head and navicu - lar body. Occasionally, because of its com - plex saddle shape, the calcaneocuboid joint may suffer distraction forces laterally and impaction forces medially. Furthermore, dis - traction forces across the Chopart joint com - plex may cause avulsions of the plantar com - ponents of the spring ligament. When ankle inversion is accompanied by plantar ex - ion (as can occur while wearing high-heeled shoes), distraction forces propagate dorsally through the talonavicular joint, often caus - ing dorsal talonavicular ligament avulsion. Distraction forces at the medial calcaneocu - boid joint may also produce joint capsule and short plantar ligament avulsion injuries. Eversion Midtarsal Sprains Although a less common injury mecha - nism, ankle eversion can also result in mid - tarsal sprains (Fig. 3B). The distinguish - ing feature of this injury is the compressive impaction (instead of distraction) force at the lateral aspect of the calcaneocuboid joint, producing impaction fractures of the anteri - or process of the calcaneus and posterolater - al cuboid, referred to as “nutcracker” injuries [23] (Fig. 3B). These impaction fractures are often comminuted and depressed. Distrac - tion forces medially can cause navicular tu - berosity avulsion fractures due to pull by the posterior tibial tendon. High-Energy Midtarsal Injuries Other uncommon mechanisms of injury known to cause Chopart joint complex inju - ries include direct longitudinal forces propa - gating along the metatarsal axes from a di - TABLE 1: Mechanisms of Midtarsal Sprains CharacteristicMechanismAnkle Inversion Ankle EversionPrimary injurious forceVarus distraction at the lateral calcaneocuboid joint, impaction at talonavicular joint, talonavicular plantar flexionValgus compression at the lateral calcaneocuboid joint, distraction at talonavicular jointPrimary injuryLateral calcaneocuboid ligamentous or bony avulsion, dorsal  talonavicular ligamentous or bony avulsion a , impaction of plantar talar head and navicular bodyLateral calcaneocuboid contusion or impaction fracture (i.e., nutcracker injuries)Ligaments involvedDorsal calcaneocuboid and calcaneocuboid components of bifurcate ligament, dorsal talonavicular ligamentShort and long plantar ligamentsSecondary injuriesMedial calcaneocuboid joint impaction, plantar ligament contusion or avulsion, plantar spring ligament avulsionPlantar ligament avulsion, navicular tuberosity avulsion, talar head impaction a With superimposed plantar flexion during injury (e.g., wearing high-heeled shoes). A Fig. 3— Schematic drawings show typical inversion and eversion injury mechanisms of Chopart joint complex. (Drawings by Tafur M, used with permission) A, Inversion, most common mechanism, will cause distraction forces and avulsions of calcaneocuboid ligaments and concomitant impaction forces at talonavicular joint. Commonly associated plantar flexion can cause dorsal talonavicular ligament sprain. Arrow shows direction of forces. B, Eversion of foot may lead to impaction injury of calcaneocuboid joint, which is also known as “nutcracker effect.” Arrow shows direction of forces. B    A  m  e  r   i  c  a  n   J  o  u  r  n  a   l  o   f   R  o  e  n   t  g  e  n  o   l  o  g  y
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