Quantitative analysis of the Trendelenburg test and invention of a modified method

While the Trendelenburg test has been used for 120 years to detect hip abductor muscle weakness, the methodology has not been standardised.

This study undertook to quantitatively analyze the relation between abductor muscle activity and pelvic tilt angle in the Trendelenburg one-leg stance, examine the pitfalls associated with performing the T-test, and develop a modified method that will produce reliable results.

A convenience sample of 15 healthy males was asked to assume a one-leg stance in ten different postures, five with mild flexion on the unsupported side, and five with severe flexion. Trunk sway angle, pelvic tilt angle, and the pelvic on femur (POF) angle were measured for each posture. Statistical analysis was used to assess differences in hip abductor activity and public tilt angle between the control posture and the test postures.

With minimum trunk sway, hip abductor muscle activity increases when the pelvis is elevated and decreases when it is dropped. With trunk sway toward the test side, abductor muscle activity decreased when the pelvis was elevated; with trunk sway toward the non-test side, muscle activity stayed approximately constant when the pelvis was dropped.

Based on the results we developed a modified T-test methodology that would improve reliability. This test should be performed with minimum trunk sway and severe flexion on the non-test side. The assessment of muscle weakness is based on whether the patient can keep the single-leg standing posture when forced to elevate the pelvis, not simply on the pelvic drop. In future research, we will perform the modified T-test on patients with a suspected hip abductor deficiency, and assess the usefulness of the modified test.