Reliability of weight-bearing heel pad thickness measurements by ultrasound

OBJECTIVE: To evaluate the intra- and inter-operator reliability of measuring weightbearing heel pad thickness in healthy subjects. BACKGROUND: Heel pad thickness has been reported to be an important factor in determining stresses observed in healthy as well as pathological feet. To date no published data are available on inter- and intra-operator variation in sonographic heel pad thickness measurements in adults. METHOD: bilateral heel pad thickness was measured in 10 adult subjects, with no history of plantar heel pain, by two experienced operators, on two separate occasions. Limits of agreement for three replicate measurements by each ultrasonographer and for replicate measurements were determined. RESULTS: Replicate heel pad thickness measurements in 95% of cases differ by less than 0.39 mm, and the magnitude of variations is similar when measurements are made by either single or different ultrasonographers, and were similar for right and left heel pad thickness measurements. Between scan measurements demonstrated a coefficient of variation of 3.2%. CONCLUSION: Weightbearing heel pad thickness measurements by ultrasound using a standardised technique in normal adult feet are reasonably reliable. RELEVANCE: Heel pad thickness can be measured reliably. Heel pad thickness may be an important predictor in the cause of ulceration in diabetics, and a potential risk factor in plantar pain affecting athletes. Further work assessing the heel pad in pathological conditions and athletes merits further study.