Mid-foot cellulitis? Ultrasound imaging of stress fracture at the third metatarsal bone
Journal
Kaohsiung Journal of Medical Sciences
Journal Volume
32
Journal Issue
3
Pages
162-163
Date Issued
2016
Author(s)
Su D.C.-J.
Abstract
Dear Editor, We feel necessary to write this letter in order to emphasize the importance of an ultrasound survey in early stress fracture by sharing a recent case. A 42-year-old woman, who ran 3 km/time and 3 times/wk for years, started to develop left mid-foot pain with local skin erythema and tenderness 3 months previous. The pain was constant and had no direct correlation with running at the time of presentation. The negative results on plain film combined with skin erythema led to an initial diagnosis of cellulitis (Figure 1A). She was referred for an ultrasonographic examination due to failure of antibiotics treatment, showing hypervascularity, cortical disruption, and periosteal reactions of the third metatarsal bone (Figures 1B and 1C) compared with the contra-lateral side (Figure 1D). Magnetic resonance imaging later confirmed the diagnosis of stress fracture, revealing moderate periosteal formation and increased bone marrow signals over the distal third metatarsal bone (Figure 1E). The bone mineral density was therefore tested, demonstrating severe osteoporosis with a T score of −3.5. Diagnosis: (A) erythema over the left dorsal foot mimicking cellulitis; (B) short-axis and (C) long-axis view of the ultrasound images of the affected foot; (D) long-axis view of the ultrasound image of the asymptomatic foot; and (E) sagittal plane of T2-weighted magnetic resonance imaging at the third meta-tarsal bone on the affected foot. Stress fracture takes place when microdestruction of bone exceeds the rate of self-repair. In lower extremities, stress fractures can occur in the tibia (most common), tarsal navicular, metatarsals, femur, pelvis, and sacrum [1]-[3]. Metatarsal stress fractures commonly occur over the second and third toes and together constitute 20% of total stress fractures of the lower extremities [2]. Female athlete triad, including inadequate strength of flexor foot muscles, decreased calcaneal bone mineral density, inaccurate biomechanics such as pes planus, or leg length discrepancy may predispose to this condition. Regarding early detection of stress fracture, magnetic resonance imaging has the highest sensitivity and specificity. Plain films have limited use in early detection because the development of callus takes approximately 3 weeks [4]. Sonography, however, is a cost-effective modality in the detection of early stress fracture and can serve as a screening tool due to a low false-negative rate [5]. In addition, a dynamic scan can be done to test dynamic movements of intrinsic flexor muscles, laxity or rigidity of the foot, nerve excursion under pressure, and the metatarsal bursa during toe flexion and extension. In our case, fluid accumulation and its relation with adjacent bones were delineated by ultrasound. The etiologies of periosseous fluid include hematoma, infection, or edema. Ultrasound cannot establish the final diagnosis but can be used as a screening tool for stress fracture. A combination of ultrasound and other images to diagnose stress fracture is essential. In a case with foot pain and local erythema mimicking foot cellulitis, we emphasize the importance of ultrasound images for differentiating early stress fracture of the foot.
SDGs
Other Subjects
antibiotic agent; adult; antibiotic therapy; bone density; case report; cellulitis; disease duration; drug treatment failure; echography; erythema; female; foot fracture; foot pain; human; Letter; metatarsal bone; metatarsal bone stress fracture; nuclear magnetic resonance imaging; osteoporosis; running; stress fracture; cellulitis; diagnostic imaging; foot; metatarsal bone; stress fracture; ultrasound; Adult; Cellulitis; Female; Foot; Fractures, Stress; Humans; Metatarsal Bones; Ultrasonics
Publisher
Elsevier (Singapore) Pte Ltd
Type
letter