Automated Insall-Salvatti Index- ISI

Purpose

Provide an automated calculation of the ISI to determine Patella Alta or Patella Baja

Tag(s)

 

Panel

Musculoskeletal Panel

Define-AI ID

19050024

Originator

Munib Sana
Lead Munib Sana

Panel Chair

Jay Patti

Panel Reviewers

Musculoskeletal Panel

License

Creative Commons 4.0 
Status Public Comment
RadElement Set RDES88
                               

Clinical Implementation


Value Proposition


Patella alta can lead to a number of pathologic processes including chondromalacia, patellar maltracking, patellofemoral instability, and a predisposition for patellar dislocation. Measuring and calculating the Insall-Salvatti Index (ISI) can be tedious and for the most part, patella alta is an “eyeball” diagnosis. An automated ISI will help improve radiology efficiency. It will also improve accuracy of diagnosis making this an objective finding rather than a subjective finding.

Narrative(s)


25 year old female presents with anterior knee pain and an MRI is performed.

Workflow Description


The images are taken and sent to PACS and the AI engine. The algorithm is triggered by the MRI scan of the knee. The images are analyzed and an ISI is calculated on every exam. The radiologist can toggle the lines/measurements on and off to see the ISI value and if it was measured accurately. If the lines/measurements are not accurately drawn, the radiologist can adjust the measurements and correct the ISI. The radiology group can also set a user-defined limit for an abnormal threshold and/or if the AI engine should alert the radiologist when there is an abnormal value.

Measurements are as follows:
Tendon Length (TL) - Length of the inner border of the patellar tendon from the lower pole of the patella to the notch in the tibial cortex at the superior border of the tibial tubercle.
Patellar Length (PL) - Oblique line connecting the inner margin of the upper pole of the patella with the most inferior point of the lower pole. This is measured at the level of the mid patella.
ISI = TL/PL.

Considerations for Dataset Development



Procedures(s)

{MRI Knee}

View(s)

{Lateral Knee (flexed at 30 degrees)}

Sex at Birth

{Male,Female}

Age

[10,90]

Patellar morphology

Elongated inferior pole of the patella (Cyrano nose) can lead to false negatives. Truncated lower pole of the patella can lead to false positives.

Osgood Schlatter

Fragmentation of the tibial tubercle may produce an inaccurate measurement (falsely low TL value).

Sinding Larsen Johanssen or Periosteal Sleeve Avulsion

Irregularity of the inferior pole of the patella may produce an inaccurate measurement (falsely elevated PL value).

Technical Specifications


Inputs

  

DICOM Study

Procedure

MRI Knee

Views

Sagittal PD, T2 or T1 MRI

Data Type

DICOM

Modality

MRI

Body Region

Lower Extremity

Anatomic Focus

Knee



Primary Outputs

 

TL Measurment 

 

 

RadElement ID

RDE513

Definition

Length of the inner border of the patellar tendon from the lower pole of the patella to the notch in the tibial cortex at the superior border of the tibial tubercle.

Data Type

Numeric

Value Set

N/A

Units

N/A

 

 

 

PL Measurment

 


RadElement ID

RDE514

Definition

Oblique line connecting the inner margin of the upper pole of the patella with the most inferior point of the lower pole. This measurement should be obtained in the mid patella.

Data Type

Numeric

Value Set

N/A

Units

N/A

 

 

ISI

 


RadElement ID

RDE515

Definition

ISI = TL/PL

Data Type

Numeric

Value Set

N/A

Units

N/A

 

 

 

 

Future Development Ideas


  • Add Modified ISI if blunted or elongated patellar morphology detected.