A 17 year-old female who recently started training for a marathon presents with progressively severe pain over her midfoot, notable for point tenderness over the 2nd metatarsal shaft. The above image was obtained (Image 1. X-ray of the left foot. Image courtesy of Matthew Negaard, MD).
The most likely diagnosis is a 2nd metatarsal stress fracture secondary to the patient’s recent increase in physical activity and bony tenderness. The above x-ray image is normal which is not uncommon as the sensitivity of x-rays for stress fracture has been reported as low as 10% at the initial presentation .
While MRI is the gold standard to diagnose stress fractures, ultrasound has also been shown to be an adequate tool. When evaluating for a metatarsal stress fracture, ultrasound has a sensitivity of 83% and a specificity of 76% with +LR of 3.45 and -LR 0.22 . Ultrasound findings suggestive of a stress fracture include hypoechoic periosteal elevation above cortical bone (Image 2), cortical disruption, and increased vascularity on Doppler signal around the periosteal lesion (Image 3) .
Image 2: Ultrasound image of the 2nd Metatarsal with hypoechoic periosteal elevation suggestive of a stress fracture. Image courtesy of Matthew Negaard, MD.
Image 3: Ultrasound Image of the 2nd Metatarsal with increased Doppler signal at the site of hypoechoic periosteal elevation suggestive of a stress fracture. Image courtesy of Matthew Negaard, MD.
The athlete should be assessed for Relative Energy Deficiency in Sport (formerly known as Female Athlete Triad) which consists of low energy availability (with or without eating disorder), menstrual dysfunction, and low bone mineral density. Energy Availability (kcal/kg/lean body mass) of less than 30kcal/kg/LBM is associated with amenorrhea . A list of screening questions was provided by the Female Athlete Triad Coalition in 2014 in their consensus statement .
Table from the 2014 Female Athlete Triad Consensus Statement .
The goal is to reduce pain and counsel the patient. A dressing with a firm, supportive shoe (such as a surgical shoe) and progressive weight-bearing are recommended. Crutches may be necessary. Counsel the patient to stop marathon training and have her follow up with Sports Medicine. You may consider an outpatient referral to an orthopedic surgeon for operative consideration if one of the following is present: 1st metatarsal involvement, proximal 5th metatarsal involvement, multiple metatarsal involvement, or intra-articular or displaced fracture.
Banal F, et al. Sensitivity and specificity of ultrasonography in early diagnosis of metatarsal bone stress fractures: a pilot study of 37 patients. The Journal of Rheumatology 2009; 36 (8) 1715-1719. PMID: 19567620
Joy E, De Souza MJ, Nattiv A, et al. 2014 female athlete triad coalition consensus statement on treatment and return to play of the female athlete triad. Curr Sports Med Rep. 2014;13(4):219–232. PMID: 25014387