Difference between revisions of "X-ray of patellar dislocation and subluxation"

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Also, look for any resultant fractures of the patella.
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Also, look for:
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*Any resultant fractures of the patella
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*Knee effusion, seen as increased space under the patella.
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==Report==
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Report even the absence of dislocation or fracture.
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{|class="wikitable"
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|+ Example
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| [[File:X-ray of patellar subluxation.jpg|150px|left]]
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Knee effusion and mild lateral subluxation. No apparent fractures (minimal radiodensity at the medial margin probably consisting of soft tissue calcification).
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|}
 
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Latest revision as of 09:56, 5 August 2019

Author: Mikael Häggström [notes 1]

Planning

Images must include an axial (skyline) view.

Evaluation

In obvious patellar dislocation, make a rough estimation of the distance compared to normal position.

In borderline cases of subluxation, preferably apply the following measurements:

  • The lateral patellofemoral angle, formed by:[1]
  • A line connecting the most anterior points of the medial and lateral facets of the trochlea.
  • A tangent to the lateral facet of the patella.
With the knee in 20° flexed, this angle should normally open laterally.[1]
  • The patellofemoral index is the ratio between the thickness of the medial joint space and the lateral joint space (L). With the knee 20° flexed, it should measure 1.6 or less.[1]

Also, look for:

  • Any resultant fractures of the patella
  • Knee effusion, seen as increased space under the patella.

Report

Report even the absence of dislocation or fracture.

Example
X-ray of patellar subluxation.jpg

Knee effusion and mild lateral subluxation. No apparent fractures (minimal radiodensity at the medial margin probably consisting of soft tissue calcification).

Notes

  1. For a full list of contributors, see article history. Creators of images are attributed at the image description pages, seen by clicking on the images. See Radlines:Authorship for details.

References

  1. 1.0 1.1 1.2 Saggin, Paulo Renato Fernandes; Saggin, Jose Idílio; Dejour, David (2012). "Imaging in Patellofemoral Instability ". Sports Medicine and Arthroscopy Review 20 (3): 145–151. doi:10.1097/JSA.0b013e3182553cfe. ISSN 1062-8592.