Difference between revisions of "X-ray of patellar dislocation and subluxation"
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| + | ==Planning== | ||
| + | Images must include an axial (skyline) view. | ||
==Evaluation== | ==Evaluation== | ||
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In borderline cases of subluxation, preferably apply the following measurements: | In borderline cases of subluxation, preferably apply the following measurements: | ||
*The '''lateral patellofemoral angle''', formed by:<ref name="SagginSaggin2012">{{cite journal|last1=Saggin|first1=Paulo Renato Fernandes|last2=Saggin|first2=Jose Idílio|last3=Dejour|first3=David|title=Imaging in Patellofemoral Instability|journal=Sports Medicine and Arthroscopy Review|volume=20|issue=3|year=2012|pages=145–151|issn=1062-8592|doi=10.1097/JSA.0b013e3182553cfe}}</ref> | *The '''lateral patellofemoral angle''', formed by:<ref name="SagginSaggin2012">{{cite journal|last1=Saggin|first1=Paulo Renato Fernandes|last2=Saggin|first2=Jose Idílio|last3=Dejour|first3=David|title=Imaging in Patellofemoral Instability|journal=Sports Medicine and Arthroscopy Review|volume=20|issue=3|year=2012|pages=145–151|issn=1062-8592|doi=10.1097/JSA.0b013e3182553cfe}}</ref> | ||
| − | :*A line connecting the most anterior points of the medial and lateral facets of the trochlea | + | :*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.<ref name="SagginSaggin2012"/> | :With the knee in 20° flexed, this angle should normally open laterally.<ref name="SagginSaggin2012"/> | ||
| − | *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. | + | *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.<ref name="SagginSaggin2012"/> |
| + | <gallery mode=packed> | ||
| + | File:Lateral patellofemoral angle.jpg | ||
| + | File:Lateral and medial joint space of patella.jpg | ||
| + | </gallery> | ||
| + | |||
| + | 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. | ||
| + | {|class="wikitable" | ||
| + | |+ Example | ||
| + | |- | ||
| + | | [[File:X-ray of patellar subluxation.jpg|150px|left]] | ||
| + | Knee effusion and mild lateral subluxation. No apparent fractures (minimal radiodensity at the medial margin probably consisting of soft tissue calcification). | ||
| + | |} | ||
{{Bottom}} | {{Bottom}} | ||
Latest revision as of 09:56, 5 August 2019
Author:
Mikael Häggström [notes 1]
Contents
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.
 Knee effusion and mild lateral subluxation. No apparent fractures (minimal radiodensity at the medial margin probably consisting of soft tissue calcification). |
Notes
- ↑ 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.
