Steps toward the validation of the Trendelenburg test: the effect of experimentally reduced hip abductor muscle function on frontal plane mechanics.

OBJECTIVE

To investigate the validity of the Trendelenburg test (TT) using an ultrasound-guided nerve block (UNB) of the superior gluteal nerve and determine whether the reduction in hip abductor muscle (HABD) strength would result in the theorized mechanical compensatory strategies measured during the TT.

DESIGN

Quasi-experimental.

SETTING

Hospital.

PARTICIPANTS

Convenience sample of 9 healthy men. Only participants with no current or previous injury to the lumbar spine, pelvis, or lower extremities, and no previous surgeries were included.

INTERVENTIONS

Ultrasound-guided nerve block.

MAIN OUTCOME MEASURES

Hip abductor muscle strength (percent body weight [%BW]), contralateral pelvic drop (cPD), change in contralateral pelvic drop (ΔcPD), ipsilateral hip adduction, and ipsilateral trunk sway (TRUNK) measured in degrees.

RESULTS

The median age and weight of the participants were 31 years (interquartile range [IQR], 22-32 years) and 73 kg (IQR, 67-81 kg), respectively. An average 52% reduction of HABD strength (z = 2.36, P = 0.02) resulted after the UNB. No differences were found in cPD or ΔcPD (z = 0.01, P = 0.99, z = -0.67, P = 0.49, respectively). Individual changes in biomechanics showed no consistency between participants and nonsystematic changes across the group. One participant demonstrated the mechanical compensations described by Trendelenburg.

CONCLUSIONS

The TT should not be used as a screening measure for HABD strength in populations demonstrating strength greater than 30%BW but should be reserved for use with populations with marked HABD weakness.

CLINICAL RELEVANCE

This study presents data regarding a critical level of HABD strength required to support the pelvis during the TT.