Reliability and validity of goniometric turnout measurements compared with MRI and retro-reflective markers

Abstract

There is no consensus on a valid and reliable method of measuring turnout. However, there is a building awareness that such measures need to exist. Total turnout is the sum of hip rotation, tibial torsion, and contributions from the foot. To our knowledge, there has been no research that directly measures and then sums each individual component of turnout to verify a total turnout value. Furthermore, the tibial torsion component has not previously been confirmed by an imaging study. The purpose of this study was to test the validity and reliability of a single total passive turnout (TPT) test taken with a goniometer by comparing it with the sum of the individual components. Fourteen female dancers were recruited as participants. Measurements of the subjects' right and left legs were gathered for the components of turnout. Tibial torsion was measured using Magnetic Resonance Imaging (MRI). Retro-reflective marker assisted measurements were used to calculate the static components of TPT. Hip external rotation, TPT, and total active turnout (TAT) were measured by goniometer. Additional standing turnout values were collected on rotational disks. Tibial torsion and hip rotation were summed and compared with three whole-leg turnout values using Two-Tailed T-Tests and Pearson product-moment correlation coefficients. Tibial torsion measurements in dancers were found to demonstrate substantial variation between subjects and between legs in the same subject. The range on the right leg was 16 degrees to 60 degrees, and the range on the left leg was 16 degrees to 52 degrees. Retro-reflective markers and biomechanical theory demonstrated that when the knee is extended and locked, "screwed home," it will not factor into a whole-leg turnout value. TAT and turnout on the disks were not statistically significant when compared with the summed total. Statistical significance was achieved in four of the eight measurement series comparing TPT with the summed value of tibial torsion and hip rotation. The advantages of a standard, valid, and reliable method of measuring turnout are many, and the risks are few. Some advantages include improved training techniques, mastery of the use of turnout at an earlier age, better dancer and teacher compliance with suggested turnout rates, understanding the use of parallel position, understanding the etiology of many dance-related injuries, and possible development of preventative measures.