A new clinical design measuring the vertical axial rotation through tibial shaft resulting from passive knee and subtalar joints rotation in healthy subjects: A reliability study

The main purposes of the study are to determine the intra-inter rater reliability of a new special designed clinical evaluation system; to measure the amount of the vertical axial rotation of the tibia resulting from passive rotation of knee and subtalar joints. To achieve this, the Measuring the Vertical Axial Rotation Tibial Shaft (MVARTS) system was designed. The system apparatus is applied to each knee and measured the vertical axial rotation of the tibia and subtalar rotations together. Fifty healthy subjects were examined using the suggested system. Two evaluators measured the tibial internal and external rotations, passively. The pure tibial rotation was also measured radiologically on the X-Ray in only 24 subjects. The intra and inter observer variation was calculated between 2.1 and 3.8 degrees with high correlation (0.84-0.98). There was no significant difference between intra and inter observers' results (p>0.05). On the other hand, amount of the internal combined rotations was lower than the external rotation (p<0.0 1). The radiological external pure tibial rotations are 19.8±6.2 deg (right), 17.0±4.6 deg (left) for the males whilst 28.7±4.0 deg (right), 23.0±5.3 deg (left) for the females. The difference between the male and female subjects was also seen to be significant (p<0.05). The results showed that the WARTS system is an appropriate, noninvasive, fast to measure combined tibial and subtalar joint rotation in addition to be economically very efficient.