Clinical Orthopaedics and Related Research®

, Volume 468, Issue 8, pp 2143–2151

Cams and Pincer Impingement Are Distinct, Not Mixed: The Acetabular Pathomorphology of Femoroacetabular Impingement

  • Justin Cobb
  • Kartik Logishetty
  • Kinner Davda
  • Farhad Iranpour
Basic Research

DOI: 10.1007/s11999-010-1347-z

Cite this article as:
Cobb, J., Logishetty, K., Davda, K. et al. Clin Orthop Relat Res (2010) 468: 2143. doi:10.1007/s11999-010-1347-z

Abstract

Background

Many impinging hips are said to have a mix of features of femoral cam and an overcovered acetabulum causing pincer impingement. Correction of such a mixed picture by reduction of the cam lesion and the acetabular rim is the suggested treatment.

Questions/purposes

We therefore asked two questions: (1) Is the acetabulum in cam impingement easily distinguishable from the pincer acetabulum, or is there a group with features of both types of impingement? (2) Is version or depth of socket better able to distinguish cam from pincer impingement?

Methods

We analyzed the morphologic features of the acetabulum and rim profile of 20 normal, healthy hips, 20 with cams and 20 with pincers on CT. Pelvises were digitized, orientated to the best-fit acetabular plane, and a rim profile was plotted.

Results

Cam hips were shallower than normal hips, which in turn were shallower than pincer hips (84° ± 5° versus 87° ± 4° versus 96° ± 5°, respectively). The rim planes of cam, normal, and pincer hips had similar version (23°, 24°, 25°), but females were 4° more anteverted than males.

Conclusions

We concluded cam and pincer hips are distinct pathoanatomic entities. Cam hips are slightly shallower than normal, whereas pincers are deeper.

Clinical Relevance

Before performing surgery for cam-type femoroacetabular impingement, surgeons should consider measuring the acetabular depth. The cam acetabulum is shallower than normal and may be rendered pathologically shallow by acetabular rim resection leading to early joint failure.

Copyright information

© The Association of Bone and Joint Surgeons® 2010

Authors and Affiliations

  • Justin Cobb
    • 1
  • Kartik Logishetty
    • 1
  • Kinner Davda
    • 1
  • Farhad Iranpour
    • 1
  1. 1.Department of OrthopaedicsImperial College, Charing Cross HospitalLondonUK

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