How are swan-neck deformities in rheumatoid arthritis (RA) classified?

Updated: Jun 11, 2021
  • Author: Michael Neumeister, MD, FRCSC, FACS; Chief Editor: Joseph A Molnar, MD, PhD, FACS  more...
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Nalebuff classified swan-neck deformities into the following 4 types, on the basis of PIP joint mobility. [12] The classification is widely accepted and aids in the choice of surgical treatment for this complex condition.

  • Type I - PIP joints are flexible in all positions.

  • Type II - PIP joint flexion is limited in certain positions.

  • Type III - PIP joint flexion is limited in all positions.

  • Type IV - PIP joints are stiff and have a poor radiographic appearance.

An alternative classification was proposed by Welsh and Hastings, who classified swan-neck deformity as mobile, snapping, or fixed, on the basis of the condition of the digital intrinsic muscles [13] and subdivided swan-neck deformity into 2 types:

  • Type I - Caused primarily by PIP joint disease

  • Type II - Caused primarily by MP joint disease

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