A comparison of sagittal MRI and lateral radiography in determining the Insall–Salvati ratio and diagnosing patella alta in the pediatric knee

A comparison of sagittal MRI and lateral radiography in determining the Insall–Salvati ratio and diagnosing patella alta in the pediatric knee

Background The Insall–Salvati ratio is a technique for determining patellar height that relies on bony landmarks. Magnetic resonance imaging (MRI) and plain radiography are used interchangeably to assess the Insall–Salvati ratio in the pediatric population despite the lack of validity in the literat...

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Bibliographic Details
Published in:Pediatric radiology Vol. 52; no. 3; pp. 527 - 532
Main Authors: Kurowecki, Darya, Shergill, Ravi, Cunningham, Kelly M., Peterson, Devin C., Takrouri, Heba S. R., Habib, Neuman O., Ainsworth, Kelly E.
Format: Journal Article
Language:English
Published: Berlin/Heidelberg Springer Berlin Heidelberg 01-03-2022
Springer Nature B.V
Subjects:
Adolescent
Child
Growth plate
Humans
Imaging
Knee
Knee Joint - diagnostic imaging
Magnetic resonance imaging
Magnetic Resonance Imaging - methods
Medical diagnosis
Medicine
Medicine & Public Health
Neuroradiology
Nuclear Medicine
Oncology
Original Article
Patella
Patella - diagnostic imaging
Patients
Pediatrics
Radiographs
Radiography
Radiology
Reliability analysis
Reproducibility of Results
Statistical analysis
Ultrasound
Knee
Patella alta
Radiography
Patellar instability
Insall–Salvati ratio
Magnetic resonance imaging
Patella
Children
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Summary:Background The Insall–Salvati ratio is a technique for determining patellar height that relies on bony landmarks. Magnetic resonance imaging (MRI) and plain radiography are used interchangeably to assess the Insall–Salvati ratio in the pediatric population despite the lack of validity in the literature. Objective The purpose of this study was to investigate if the Insall–Salvati ratio and patella alta as determined on MRI are comparable to those determined on radiography in pediatric patients. Materials and methods We conducted a retrospective review of 49 pediatric patients (age range: 7.5–17.0 years) with unfused growth plates who underwent both knee MRI and lateral knee radiography. Measurements for calculating the Insall–Salvati ratio (the ratio of patella tendon length to patella length) were obtained by three observers. Data were analyzed using paired t -tests and Pearson’s correlation. A reliability assessment and inter-method agreements were performed. Patella alta was defined as an Insall–Salvati ratio > 1.2. Additional cutoffs of Insall–Salvati ratios > 1.3 and > 1.4 were also analyzed. Results There was no statistically significant difference between Insall–Salvati ratio as determined on MRI (mean: 1.20) and radiographs (mean: 1.25; P  > 0.05). There was a strong correlation between Insall–Salvati ratio as determined on MRI and radiographs (Pearson’s r  = 0.6) with moderate consistency (Cronbach’s alpha = 0.78). There was a good level of agreement between the diagnosis of patella alta on MRI and radiographs when defined as an Insall–Salvati ratio greater than 1.2 and 1.3 (Cohen’s kappa = 0.61). Conclusion The results demonstrate a strong association between Insall–Salvati ratio and patella alta derived from MRI and radiographs in children ages 7.5 years and older.
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ISSN:0301-0449
1432-1998
DOI:10.1007/s00247-021-05207-4