The Twist Test: A New Test for Hip Labral Pathology (SS-37)

Abstract

Introduction Acetabular labral pathology is now recognized as a more common injury than previously thought. With cost constraints of MRI and invasiveness of MRI arthrogram, physical examination remains essential for diagnosis. Most tests for labral pathology are currently done in the supine position. We have developed the “twist test,” which is done with the patient standing and can evaluate the patient in functional, weight bearing position. The purpose of this study is to describe the twist test and compare its reliability to MRI arthrogram. Methods Between June 2009 and August 2010, the twist test was performed on all patients presenting to our clinic with complaint of hip pain. 371 patients had the twist test performed. Of these, 247 had an MRI arthrogram (MRA) of the affected hip. The twist test results were compared with MRA findings. A labral tear, degeneration, fraying, and paralabral cyst were considered as a positive MRA. The twist test is done with the patient facing the examiner, toes pointing forward. The patient bends their knees to 30 degrees and performs a windshield wiper like action with maximal excursion to the left and right. If the patient tolerates this, then the patient first gets on the unaffected leg, again with the knee bent at 30 degrees, and “does the twist” one-legged, with the examiner holding their hands gently for balance. The test is then repeated on the affected hip. A positive test is groin pain on the affected hip, apprehension with performing the test on the affected hip, or gross range of motion deficits on the affected hip compared with the unaffected side. Results Among 160 patients with a positive twist test, 154 patients had positive MRA and 6 had negative MRA. Among 87 patients with a negative twist test, 72 had positive MRA and 15 had negative MRA. In comparison with MRA, the sensitivity and specificity of twist test for labral injury were 68.14% and 71.5%, respectively. Positive predictive value (precision) of twist test for diagnosis of labral lesion was 96.25% and the accuracy was 68.4%. Conclusion Physical examination tests for hip pathology are an important screening tool. Current tests include the McCarthy test and the impingement test. We introduce a new test for hip labral pathology, which is done standing. In our study, the twist test had a high positive predictive value (96.25%), so this test can be beneficial for ruling out labral pathology. An added benefit is that this test is quick to perform, so it could be incorporated into a general sports physical screening examination.