Assessment of fixed flexion deformity of the hip.

The time-honored method of measuring fixed flexion deformity of the hip of Hugh Owen Thomas (HOT) gives misleading results, because hip movements are not separated from pelvic and spinal movement. A photographic method of measuring the angle between the thigh and pelvis was used to compare the results of the HOT with those of a new test, whereby the patient is examined prone, with the ipsilateral thigh flexed over the side of the examination couch. The errors inherent in Thomas's test ranged from 5 degrees to 20 degrees, while the errors in the new prone test ranged from 0.5 degrees to 4.5 degrees. A comparison of the two tests demonstrated that the HOT consistently gave greater angles, depending on the amount of flexion imposed on the contralateral hip by the examiner.