Precision of novice sonographers concerning median nerve and Achilles tendon measurements

The aim of this study was to quantify how precise the measurements of beginner sonographers (relative to an expert) are concerning small and large ellipsoid structures (median nerve and Achilles tendon).

During a 4-day musculoskeletal ultrasonography course at a secondary-care center, 19 attendants and an expert physiatrist sonographer were enrolled. After the hand practice session, the physicians performed median nerve measurements (short axis, long axis, and cross-sectional area) at the level of carpal tunnel on the same subject. Repeat measurements were done at the end of the following day. Similarly, achilles tendon measurements were taken during 2 consecutive days (after the ankle-foot session). An expert sonographer also performed the same evaluations twice, together with the attendants. The mean values of the expert's measurements were used as the "test value" for each parameter.

Median nerve long-axis values pertaining to the first trial were found to be smaller than that of the test value (P = 0.003), but those of the second trial were similar to the test value (P = 0.107). Median nerve short-axis and area measurements were not different from the test value in either trials (P > 0.05). Achilles tendon measurements were significantly larger than the test value (P < 0.05) at the first trial but were similar to the test value at the second trial (P > 0.05). Percentage deviations of the attendants' measurements (median nerve short and long axes) were negatively correlated with their sonography experience.

We imply that novice sonographers tend to measure small structures smaller and large structures larger. Personal experience seems to play a role especially for small structures, and practice affects the precision of these measurements favorably.