Plantar fasciitis is a low-grade inflammation of the plantar fascia and perifascial tissues. It is a common cause of heel pain and usually affects middle-aged women, as well as younger, predominantly male, runners (1). The condition is likely related to repeated strain, leading to microtears and inflammation. Imaging is commonly used to confirm the diagnosis, and exclude other causes of posterior heel pain (2).Although MR imaging may be used to diagnose plantar fasciitis, many authors suggest ultrasound is an accurate, simple, and noninvasive technique to diagnose the condition. Previous investigators have reported that the most important diagnostic findings in plantar fasciitis are thickening and hypoechogenicity, and occasionally fluid collections adjacent to the fascia. Wall et al. (3) suggest that a plantar fascia thickness greater than 4 mm is consistent with plantar fasciitis. This value has been used as a reference value in several studies (4-6).To our knowledge, there are no data about the ultrasound appearance of the plantar fascia in asymptomatic subjects. Hence, it is not known if certain commonly used ultrasound criteria of plantar fasciitis might be seen in such a population. If so, this may entail the risk of attributing the patients' symptoms to a reference point where the plantar fascia crossed the anterior aspect of the inferior border of the calcaneus. The measurement points are indicated in the figures by calipers (Figs. 1-3). The plantar fascia was evaluated for echogenicity. It was only considered hypoechoic if its echogenicity was markedly decreased with respect to the subcutaneous heel fat. The plantar fascia was also assessed for presence of calcification defined as markedly hyperechoic foci, with or without acoustic shadowing, vascularity with Doppler, tear, and fluid adjacent to the fascia. The saved images were reviewed by 2 investigators. Statistical analysis was performed using a t-test (independent samples) (IBM SPSS Statistics 20, Armonk, NY). The significance threshold was set at p = 0.05.
ResultsA total of 62 plantar fascias in 31 subjects (14 men, 17 women), aged from 17 to 79 years (mean age, 45 years) were evaluated ( Fig. 1-3). The results are shown in Tables I and II. The mean thickness of the plantar fascia in men was 3.7 mm (range, 2.5-7 mm), and in women 3.5 mm (range, 1.7-5.1 mm). There was no statistically significant difference between the thickness of the fascia in men and women (p = 0.21). There was no significant difference between the right and the left foot (p = 0.64).The thickness of the plantar fascia was greater than 4 mm in 4 men plantar fasciitis while other abnormalities may be overlooked and not further investigated. Therefore we decided to evaluate the plantar fascia in asymptomatic subjects with high resolution ultrasound.
Materials and methodsInstitutional Review Board approval for our study was obtained and consent from the asymptomatic subjects. They were interviewed to confirm they had not been symptomatic at the sole of the foot. Other exclusion cr...