title: Is the internal rotation lag sign a sensitive test for detecting hip abductor tendon ruptures after total hip arthroplasty?
abstract: BACKGROUND
  Total hip arthroplasty (THA) is one of the most frequently performed procedures in orthopaedics and weakness of external rotators is often recognized thereafter. However, the etiology of lateral hip pain is multifaceted. For the diagnosis of abductor tendon rupture, magnetic resonance imaging (MRI) is the gold standard. As not every patient can be subjected to MRI, a clinical diagnostic test for easy detection of lesions of the abductor tendon is missing. Here, we present the internal rotation lack sign indicating abductor tendon pathology.
  
  
  METHODS
  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.
  
  
  RESULTS
  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.
  
  
  CONCLUSIONS
  The new clinical diagnostic sign presented here may improve the diagnosis of abductor tendon rupture in the future.
  
  
  METHODS
  Diagnostic study, level I.
authors.affiliation: Department of Surgery, Division of Trauma Surgery, University Hospital Zurich, Raemistrasse 100, 8091 Zurich, Switzerland. Clement.Werner@usz.ch.
authors.forename: Christian
authors.initials: C
authors.lastname: Ossendorf
authors.forename: Laurent
authors.initials: L
authors.lastname: Bohnert
authors.forename: Nadja
authors.initials: N
authors.lastname: Mamisch-Saupe
authors.forename: Daniel
authors.initials: D
authors.lastname: Rittirsch
authors.forename: Guido A
authors.initials: GA
authors.lastname: Wanner
authors.forename: Hans-Peter
authors.initials: HP
authors.lastname: Simmen
authors.forename: Claudio
authors.initials: C
authors.lastname: Dora
authors.forename: Clément Ml
authors.initials: CM
authors.lastname: Werner