Clinical Orthopaedics and Related Research

, Volume 466, Issue 3, pp 677–683 | Cite as

Ischial Spine Projection into the Pelvis

A New Sign for Acetabular Retroversion
  • Fabian Kalberer
  • Rafael J. Sierra
  • Sanjeev S. Madan
  • Reinhold Ganz
  • Michael Leunig
Original Article Spine

Abstract

Femoroacetabular impingement may occur in patients with so-called acetabular retroversion, which is seen as the crossover sign on standard radiographs. We noticed when a crossover sign was present the ischial spine commonly projected into the pelvic cavity on an anteroposterior pelvic radiograph. To confirm this finding, we reviewed the anteroposterior pelvic radiographs of 1010 patients. Nonstandardized radiographs were excluded, leaving 149 radiographs (298 hips) for analysis. The crossover sign and the prominence of the ischial spine into the pelvis were recorded and measured. Interobserver and intraobserver variabilities were assessed. The presence of a prominent ischial spine projecting into the pelvis as diagnostic of acetabular retroversion had a sensitivity of 91% (95% confidence interval, 0.85%–0.95%), a specificity of 98% (0.94%–1.00%), a positive predictive value of 98% (0.94%–1.00%), and a negative predictive value of 92% (0.87%–0.96%). Greater prominence of the ischial spine was associated with a longer acetabular roof to crossover sign distance. The high correlation between the prominence of the ischial spine and the crossover sign shows retroversion is not just a periacetabular phenomenon. The affected inferior hemipelvis is retroverted entirely. Retroversion is not caused by a hypoplastic posterior wall or a prominence of the anterior wall only and this finding may influence management of acetabular disorders.

Level of Evidence: Level II, prognostic study. See the Guidelines for Authors for a complete description of levels of evidence.

Notes

Acknowledgments

We thank Burkhardt Seifert, Department of Biostatistics, ISPM, University of Zürich, Switzerland.

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Copyright information

© The Association of Bone and Joint Surgeons 2008

Authors and Affiliations

  • Fabian Kalberer
    • 1
    • 5
  • Rafael J. Sierra
    • 2
  • Sanjeev S. Madan
    • 3
    • 5
  • Reinhold Ganz
    • 1
    • 5
  • Michael Leunig
    • 4
    • 5
  1. 1.Department of OrthopedicsBalgrist University Hospital, University of ZürichZurichSwitzerland
  2. 2.Department of Orthopedic SurgeryMayo ClinicRochesterUSA
  3. 3.Department of OrthopaedicsSheffield Children HospitalSheffieldUK
  4. 4.Department of OrthopaedicsSchulthess ClinicZurichSwitzerland
  5. 5.Department of Orthopaedic SurgeryUniversity of BerneBerneSwitzerland

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