Evaluation of a Physical Exam Test for Determination of Leg Length Discrepancy Versus the Standard Postural X-ray Series in Low Back Pain Patients

Objective: To determine if the hip (pelvic) swing test for short leg is equivalent to the postural x-ray series for determination of leg length discrepancy in patients with low back pain. Methods: Patients between the ages of 18 and 65 years who presented to the UNTHSC Department of OM with low back pain and a short leg on clinical exam were enrolled in the study. A hip swing test was performed with the patient barefoot. The test was repeated with heel lifts of various heights to determine which lift allowed for equal rotational motion of the hips. The height of the correct heel lift was recorded in the patient’s chart. Each patient was then referred to Radiology Associates for a postural standing x-ray series. The measure of sacral base unleveling was recorded. The correlation between physical exam test and postural x-ray results was analyzed using a kappa correlation. Results: 30 subjects participated in the study. All subjects underwent the hip swing test and postural standing x-rays. There was a positive correlation (P value) between heel lift height, as determined by physical exam test, and sacral base unleveling measured with imaging. Conclusion: The study shows that the hip swing test may be as reliable and clinically applicable as postural standing x-rays in the evaluation of leg length discrepancy in patients with low back pain. These findings have the potential to alleviate the need for x-rays in the future, thus saving money and reducing the risk of radiation exposure to patients.