Modified Insall-Salvati ratio
Last revised by Jeremy Jones on 27 Jan 2024
Citation, DOI, disclosures and article data
Citation:
Knipe H, Jones J, Roberts D, et al. Modified Insall-Salvati ratio. Reference article, Radiopaedia.org (Accessed on 19 Mar 2024) https://doi.org/10.53347/rID-74625
rID:
74625
Article created:
Disclosures:
At the time the article was created Henry Knipe had no recorded disclosures.
View Henry Knipe's current disclosures
Last revised:
27 Jan 2024,
Jeremy Jones ◉
Disclosures:
At the time the article was last revised Jeremy Jones had no financial relationships to ineligible companies to disclose.
View Jeremy Jones's current disclosures
Revisions:
13 times, by
6 contributors -
see full revision history and disclosures
Systems:
Synonyms:
- Modified Insall-Salvati index
- Modified Insall-Salvatti index
The modified Insall-Salvati ratio or index is another technique to assess patellar height.
On this page:
Usage
It was proposed to avoid mismeasurement due to the variable shape of the inferior patella pole 2, however, the Insall-Salvati ratio has been demonstrated to be more reproducible 3.
Measurement
The modified Insall-Salvati ratio is applied on a lateral 30° flexed knee radiograph like the Insall-Salvati ratio but is measured differently:
- A: distance from the inferior margin of the patellar articular surface (as opposed to the lower pole of the patella itself) to the patellar tendon insertion
- B: length of the patellar articular surface
Modified Insall-Salvati ratio = A/B
Interpretation
- normal: 1.25 (range 1.2-2.1) 2
-
patella alta: >2
- at this cut-off, 3% of normal knees will be classified as patella alta 3
References
- 1. Grelsamer RP, Meadows S. The modified Insall-Salvati ratio for assessment of patellar height. Clin. Orthop. Relat. Res. 1992; (282): 170-6. Pubmed citation
- 2. W. Norman Scott. Insall & Scott Surgery of the Knee E-Book. (2011) ISBN: 9781455727896
- 3. Mark D. Miller, Stephen R. Thompson. DeLee and Drez's Orthopaedic Sports Medicine E-Book. (2009) ISBN: 9781437721713
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