Ankle and Foot 47 - Department of Radiology - University of ...

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2304 VII Imaging of the Musculoskeletal System B C A Figure 47-107. Early Jones fracture in a 21-year-old college athlete. A, On the initial anteroposterior radiograph of the base of the fifth metatarsal there is a very subtle periosteal reaction (white arrow). There is a questionable lucency (open arrowheads) extending transversely through the lateral cortex. B, Far lateral sagittal inversion recovery (IR) image reveals bone marrow edema throughout the fifth metatarsal. C, Sagittal IR image through the asymptomatic fourth metatarsal for comparison revealed normal dark marrow signal. Because of the high propensity for Jones fractures to have delayed union or nonunion, elective internal fixation with a lag screw was performed the next day. D, Follow-up anteroposterior radiograph 2 weeks later reveals bone resorption (arrowheads) along the questionable lucency in A, part of the normal early healing response. Subsequent radiographs (not shown) demonstrated solid bony bridging 1 month later. D itive stress in athletes, or as in the case of Sir Robert Jones, “whilst dancing.” 25 The Jones fracture is well recognized to have a high rate of nonunion or delayed union because of the relative hypovascularity of this portion of the fifth metatarsal, prompting orthopedic surgeons to recommend early screw fixation. MRI is useful in confirming the diagnosis when it is suspected in athletes with radiographically occult injuries (Fig. 47-107). March Fracture. The march fracture is found most commonly in the mid- to distal diaphysis of the second metatarsal and less often in the third. Unlike the Jones fracture, which occurs in high-performance athletes, stress fractures in the second and third metatarsals occur in individuals who have previously led relatively sedentary lifestyles, then suddenly increase their level of activity. This fracture was first reported by Breithaupt in 1855, 11 when he described foot pain and swelling in military recruits in the Prussian army who were forced to go on long marches—hence the name “march fracture.” This was of course 40 years before Röntgen’s discovery of x-rays. The first radiographic reports of march fractures were in 1897.* Radiographically, the *In his 2006 academic dissertation for the University of Helsinki, Bone Stress Injuries of the Foot and Ankle (http://ethesis.helsinki.fi/julkaisut/laa/kliin/vk/ sormaala/bonestre.pdf), Sormaala cites these two references: Schulte: Die sogenannte Fussgeschwulst. Arch Klin Chir 1897;55:872. Stechow: Fussödem und Röntgenstrahlen. Deutsche Militärärztliche Zeitschrift 1897;26:465-471. second and third metatarsals respond to stress by forming a periosteal reaction, although this may be imperceptible or subtle early on (Fig. 47-108). Edema-sensitive MRI reveals abnormally bright marrow signal in the diaphysis as well as bright periosteal reaction outside the cortex. • Sesamoid Stress Fractures Sesamoid stress fractures are notoriously difficult to diagnosis radiographically. Perhaps because of their varying presence and appearance, radiologists tend to have a “blind spot” when it comes to the sesamoids. However, when looking at the sesamoids of the first metatarsophalangeal joint, there are some helpful statistics to keep in mind. Although the other sesamoid bones of the foot are present in less than 10% of people, the two sesamoids plantar to the head of the first metatarsal are present in 100% of the population. 16 Absence of either the medial (tibial) or lateral (fibular) sesamoids is always abnormal, and a destructive process should be considered (see Fig. 47-92). And although a multipartite medial sesamoid bone is a common normal variant found in 13% to 30% of the population, a multipartite lateral sesamoid bone is an uncommon variant, found in only 1% of normal feet. When symptoms are referable to the lateral sesamoid and radiographs reveal it to be multipartite, this should be diagnosed as a fracture (Fig. 47-109). Additional diagnostic imaging should not be required, although MRI or a nuclear Ch047-A05375.indd 2304 9/9/2008 5:36:04 PM
47 Ankle and Foot 2305 47 A Figure 47-108. Second metatarsal stress fracture in a 22-year-old who developed foot pain during a 1- week vacation in which the patient did a lot of walking in sandals. A, Oblique radiograph reveals a periosteal reaction along the medial cortex (white bracket in magnified dashed box). B, Long-axis T1-weighted image through the second metatarsal well illustrates the anatomy, but not the pathology. C, Corresponding long-axis T2-weighted fat-suppressed image reveals bone marrow edema throughout the second metatarsal diaphysis, the thickened medial cortex/ periosteum, and edema of the adjacent medial soft tissues. Short-axis T1-weighted (D) and T2-weighted fat-suppressed (E) images through the metatarsal shafts reveal edema in the second metatarsal bone marrow and in the adjacent medial soft tissues overlying the periosteal reaction. Sagittal T1-weighted (F) and inversion recovery (G) images through the marker (m) indicating the site of maximal tenderness show edema in and around the second metatarsal. B C D E F G Ch047-A05375.indd 2305 9/9/2008 5:36:06 PM
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