, Volume 471, Issue 8, pp 2463-2470
Date: 08 Nov 2012

The Crossover Sign Overestimates Acetabular Retroversion

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The crossover sign is a radiographic finding associated with cranial acetabular retroversion and has been associated with pincer-type femoroacetabular impingement (FAI) in patients with hip pain. Variable morphology, location, and size of the anterior inferior iliac spine (AIIS) may contribute to the crossover sign even in the absence of retroversion. Thus, the sign may overestimate the incidence of acetabular retroversion.


We asked: Can the crossover sign appear on standardized, well-positioned AP pelvis radiographs despite the absence of acetabular retroversion? And what is the contribution of variable size and morphology of the AIIS to a crossover sign?


We evaluated radiographs of 53 patients with symptomatic FAI in the absence of substantial chondral degenerative changes (< Tönnis Grade 2). Forty-one radiographs met the appropriate criteria of neutral tilt and obliquity. Three independent reviewers determined presence and location of the crossover sign. Acetabular version was defined using high-resolution three-dimensional CT. CT reconstructions were used to define three AIIS types addressing AIIS morphology.


Nineteen of 38 radiographs with a crossover sign on AP radiographs had focal or global acetabular retroversion on three-dimensional CT (positive and negative predictive values = 50%). In contrast, the AIIS extended to or below the level of the anterior superior acetabular rim and was partially or completely responsible for the appearance of a radiographic crossover sign in all 19 hips with an anteverted acetabulum. High interobserver reliability (kappa > 0.8) was found for AIIS types.


A crossover sign is frequently present on well-positioned AP pelvis radiographs in the absence of acetabular retroversion. Variable AIIS morphology may explain the appearance of this sign in the presence or absence of acetabular retroversion.

Level of Evidence

Level III, diagnostic study. See Instructions for Authors for a complete description of levels of evidence.

Each author certifies that he or she, or a member of his or her immediate family, has no commercial associations (eg, consultancies, stock ownership, equity interest, patent/licensing arrangements, etc) that might pose a conflict of interest in connection with the submitted article.
All ICMJE Conflict of Interest Forms for authors and Clinical Orthopaedics and Related Research editors and board members are on file with the publication and can be viewed on request.
Each author certifies that his or her institution approved the human protocol for this investigation, that all investigations were conducted in conformity with ethical principles of research, and that informed consent for participation in the study was obtained.
This work was performed at the Hospital for Special Surgery, New York, NY, USA.