A comparison of the reliability of the trochanteric prominence angle test and the alternative method in healthy subjects

A wide range of intra- and inter-rater reliabilities of the trochanteric prominence angle test (TPAT) has been reported. We introduced the transcondylar angle test (TCAT) as an alternative to the TPAT and using a smartphone as a reliable measurement tool for femoral neck anteversion (FNA) measurement. The reliabilities of the TPAT and the TCAT, the reliability of using a smartphone as a clinical measurement tool, and the correlation between the difference value of medial knee joint space (KJS) between rest and tested positions and the difference value between the TPAT and TCAT were assessed. Two physical therapists independently determined the reliabilities of the TPAT with a digital inclinometer, the TCAT with a digital inclinometer, and the TCAT with a smartphone in 19 hips of 10 healthy subjects (5 male and 5 female, 22.2 ± 1.69 years). The medial KJS in rest and the tested position were assessed using a sonography. The intra-class correlation coefficients (ICC) for the intra-rater reliabilities of TPAT with a digital inclinometer (ICC = 0.92), TCAT with a digital inclinometer (ICC = 0.94) and a smartphone (ICC = 0.95) in both testers were substantial. The inter-rater reliability of TPAT with a digital inclinometer was fair (ICC = 0.48) while TCAT with a digital inclinometer (ICC = 0.89) and a smartphone (ICC = 0.85) were substantial. The correlation between the difference value of medial KJS between rest and tested positions and the difference value between TPAT and TCAT was low and statistically non-significant (r = 0.114; p = 0.325). The TCAT would be more reliable than the TPAT in inter-rater test. Using a smartphone is a clinically comparable measuring tool to a digital inclinometer.