How To Detect Chronic Heel Pain With Musculoskeletal Ultrasound
One can scan the heel with the patient supine or prone. The preferred method is to have the patient in the prone position. Most clinicians lean toward this position because it tends to be easier for the examiner. Assess all three bands: medial, central and lateral. The examiner can scan in the long axis (sagittal plane) and the short axis (coronal plane). By far, the long axis will give the best information on the status of the fascia.
One should assess the quality of the fascia. A normal fascia will have a fibrillar pattern. There will be anisotropy present where the fibers attach to the inferior aspect of the calcaneus. Take care not to confuse this with pathology. When documenting this properly, it is important to include a photo with the written description. Assessment then proceeds with measurement of the plantar fascia. Measure at the inferior aspect of the heel. Place the digital calipers at the hyperechoic line that represents the inferior aspect of the heel and the hyperechoic outline of the fascia at its most plantar expansion.
(Just to clarify, the superior aspect of the image on the screen represents the plantar aspect of the heel. In other words, the image is inverted. By U.S. convention, the right of the screen should represent distal and the left of the screen would be proximal. Turning the probe 180 degrees will correct the orientation if one finds this not to be the case.)
A fascial thickness of 4 mm has been mentioned as the upper limit of normal. When it comes to fascial thickness, I have even heard that one should consider upper normal limits of 4 mm for the medial band, 3 mm for the central band and 2 mm for the lateral band. Barrett, et. al., have looked at cadavers and plantar fascial thickness.1
It stands to reason that fascial thickness will vary depending on the size of the individual. I have seen this in my own practice. I have measured a patient’s normal fascia at 5 mm in thickness numerous times. Accordingly, when it comes to a unilateral case, one must compare the affected heel to the contralateral side. Another pitfall to avoid is including the deep musculature (i.e. flexor digitorum brevis) in one’s measurement. In some individuals, the muscular layer can be delineated deep to the fascia at the heel.
Documentation of an ultrasound of the heel can be in a separate report or as a subset of the objective part of one’s notes. Either way, photos should accompany the written report. The assessment should include the measurements of all three bands of the symptomatic fascia and, in a unilateral case, the asymptomatic heel as a comparison. Along with the quantitative assessment, one should include a qualitative description as well and utilize proper terminology. Here are some of the more common terms:
• Hyperechoic: increased echo or brightness on the screen
• Hypoechoic: decreased echo or gray to dark on the screen
• Anechoic: lack of echo or black on the screen
• Fibrillar pattern: normal fiber pattern of tendon or ligament
• Echotexture: general term referring to the internal architecture of the structure and the echo pattern seen