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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
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Procedures(s) |
{MRI Knee} |
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View(s) |
{Lateral Knee (flexed at 30 degrees)} |
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Sex at Birth |
{Male,Female} |
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Age |
[10,90] |
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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. |
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Osgood Schlatter |
Fragmentation of the tibial tubercle may produce an inaccurate measurement (falsely low TL value). |
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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
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Procedure |
MRI Knee |
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Views |
Sagittal PD, T2 or T1 MRI |
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Data Type |
DICOM |
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Modality |
MRI |
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Body Region |
Lower Extremity |
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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.