Background: The determination of anatomical reference frames in the rearfoot during three-dimensional multisegment foot modeling has been hindered by a variety of factors. One of these factors is related to the difficulty in palpating, or the absence of, anatomical landmarks. A novel device (the Calcaneal Marker Device) aimed at standardizing marker placement at the calcaneus was, therefore, developed and evaluated for its reliability.
Methods: Throughout a random repeated-measures design, the repeatability of calcaneal marker placement was evaluated for two techniques: manual placement and placement using the Calcaneal Marker Device. Translational changes after marker placement and the clinical effect on intersegment angle calculation were quantified.
Results: Intraobserver variability was greater in therapist 2 (<5.3 mm) compared with therapist 1 (<2.9 mm). Intraobserver variability was also found to be less than 1.6 mm throughout use of the device. Interobserver variability was found to be significantly higher for the position of markers placed manually (5.8 mm), whereas with the Calcaneal Marker Device, the variability remained lower (<1.3 mm). The effect on the computed intersegment angles followed a similar trend, with variability of 0.4° to 4.0° and 1.0° to 8.7° for CMD and manual placement, respectively.
Conclusions: These findings suggest that variations in marker placement are considerably reduced when the novel Calcaneal Marker Device is used, possibly toward the limits dictated by the fine motor skills of therapists and tissue artifacts.