A reproducible and inexpensive method of measuring hip abductor strength

The evaluation of hip abductor strength is useful in assessing of the outcome of hip surgery. Hand-held dynamometers are available, but they are less reliable in assessing hip abductor strength than some other muscle groups. We describe a new device designed to measure hip abductor strength, which is practical in a clinical setting. A system of constraints, pads and reference points was devised to make force measurements as little examiner-dependent as possible. Reproducibility was assessed in a controlled setting. The abductor strength of ten healthy young subjects ( average age 28 years) was tested twice on each side by two independent examiners. Tests were performed in a supine position, eliminating the influence of gravity and examiner intervention. The results indicated high reproducibility, the maximal measurement uncertainty being within 1 N. Intra-class correlation coefficients ranged from 0.85-0.98 for intra-rater reproducibility, and 0.81-0.96 for inter-rater reporoducibility. The coefficient of variation was lower than 10%. The device described may be suitable for routine clinical assessment of patients after hip surgery.