Summary
Placement of markers on anatomical landmarks represents a large source of error in
three-dimensional kinematics. Our objectives were to test the accuracy and precision
of a custom-made pointer and compare it to conventional skin markers in dogs. The
pointer was first assessed by pointing at the surface of a spherical marker of known
dimensions and position in space. Secondly, a point located cranio-distally to the
lateral epicondyle was marked in 12 canine elbows with a Steinmann pin and reflective
markers. Ability to locate a landmark was compared between the pointer and skin-mounted
marker. The distance between experimental and true locations was compared between
the two methods. A sphere was mathematically fitted through 29 collected points on
the spherical marker. Centre, diameter and volume overlap of the fitted sphere were
compared to that of the marker. A 0.729 mm bias was found indicating good accuracy.
Residual values were small indicating good precision. The average distance between
the true and experimental position of the anatomical landmarks were 9.55 ± 4.20 mm
and 9.32 ± 3.28 mm for the pointer and the marker respectively. No significant differences
were observed between the two methods. The pointer proved to be accurate and reliable
for localizing virtual points and was at least equivalent to skin mounted markers
for the detection of anatomical landmarks in the dog. It should prove useful in the
localization of anatomical landmarks for kinematic analysis.
Keywords
Three-dimensional kinematics - pointer - calibration - virtual landmarks - dog