Is the internal rotation lag sign a sensitive test for detecting hip abductor tendon ruptures after total hip arthroplasty?

The patient is placed in lateral position on a stretcher with hips and knees in neutral position. The knee is flexed to 45° and the hip passively abducted and elevated by the investigator. With the foot passively abducted, the patient is then asked to bring his knee in direction to the examination table. This motion is also tested passively. The test is regarded positive, if no internal rotation is possible and/or if this is painful. If groin pain is elicited during either of the exercises, the test is also rated positive.We evaluated this test in 20 patients clinically and by magnetic resonance imaging (MRI). All patients demonstrated a positive internal rotation lag sign. Twelve of them lag of internal rotation and evidence of anterior abductor tendon rupture on MRI, 8 with lag of internal rotation and no evidence of abductor tendon rupture.The new clinical diagnostic sign presented here may improve the diagnosis of abductor tendon rupture in the future.Level of Evidence: Diagnostic study, level I.Total hip arthroplasty (THA) is one of the most frequently performed procedures in orthopaedic surgery done more than 300'000 times annually in the United States alone with an increase of 158% between 1990 and 2004 [1]. In addition, the number of total joint replacements is expected to rise to 600'000 by 2030 [2].Among the regularly performed approaches to the hip joint are the anterior (Smith-Peterson) [3,4], anterolateral (Watson-Jones) [5,6], lateral transgluteal (Hardinge) [7], and posterior (Moore), [8] approach, virtually each of which has been modified for minimally invasive hip replacement surgery [9-14] and comprises its distinct features, problems and pitfalls [15-17]. In patients with THA implanted by a direct lateral transgluteal approach, weakness of external hip rotation due to iatrogenic damage to the external rotators is possible [18,19]. Heterotopic ossifications are a possible complication [20]. Among potential consequences are mechanical malfunction, m