Diagnostic Accuracy of MRI Evaluation of Patellar Position According to the Physeal Line in Pediatric Patients

Abstract

Aim: Abnormal positioning of the patella, of which the superior position is defined as patella alta (PA), whereas the inferior position is defined as patella baja (PB). Most of the measurements of patellar position evaluations are time-consuming. In this study, we aimed to examine the diagnostic accuracy of visual evaluation of the patellar position according to the physeal line and to determine the inter- and intraobserver agreement of this evaluation in MRI examinations. Material and Methods: Knee MRI examinations performed between 2019-2021 with different knee symptoms and prediagnoses were retrospectively analyzed in this study. As a reference test, Insall-Salvati Ratio was calculated by the following formula: Tendon length/patellar length. Two visual evaluation methods were used; physis line to the patella (PLP) and physis line to patellar joint cartilage (PLC). Results: Three hundred and sixty consecutive children aged 60-215 months were included in the study. There was excellent an agreement of both intra- and interobserver on PLP and PLC for two observers (κ > 0.800, for all). When we evaluated intra- and interobserver agreements according to groups, almost perfect agreements were detected (κ > 0.750, for all). Diagnostic accuracy for both two observers on the visual evaluation of PLP was almost perfect (Sensitivity 95.5%, specificity 87.2% for observer 1, and Sensitivity 94.7%, specificity 87.2% for observer 2), and on the PLC evaluation was also good (Sensitivity 89.3%, specificity 82.9% for observer 1, and Sensitivity 88.1%, specificity 85.5% for observer 2). Conclusion: Even though direct radiography is used in the diagnosis of PA and PB, it has been shown that MRI can also be used in pediatric patients in daily practice. Instead of the time-consuming measurements used in MRI, it may be kept in mind to use these methods in our study for practical and accurate diagnosis.

Keywords

• MRI
• insall-salvati ratio
• patella alta
• patella baja
• agreement
• pediatric patients

Kaynakça

1. Miller TT, Staron RB, Feldman F. Patellar height on sagittal MR imaging of the knee. AJR Am J Roentgenol. 1996;167:339-41.
2. Degnan AJ, Maldjian C, Adam RJ, et al. Comparison of Insall-Salvati ratios in children with an acute anterior cruciate ligament tear and a matched control population. AJR Am J Roentgenol. 2015;204:161-6.
3. Insall J, Goldberg V, Salvati E. Recurrent dislocation and the high-riding patella. Clin Orthop Relat Res. 1972;88:67-9.
4. Insall J, Falvo KA, Wise DW. Chondromalacia Patellae. A prospective study. J Bone Joint Surg Am. 1976;58:1-8. Møller BN, Krebs B, Jurik AG. Patellar height and patellofemoral congruence. Arch Orthop Trauma Surg. 1986;104:380-1.
5. Insall J, Salvati E. Patella position in the normal knee joint. Radiology. 1971;101:101-4.
6. Kurowecki D, Shergill R, Cunningham KM, et al. A comparison of sagittal MRI and lateral radiography in determining the Insall-Salvati ratio and diagnosing patella alta in the pediatric knee. Pediatr Radiol. 2022;52:527-32.
7. Giovagnorio F, Olive M, Casinelli A, et al. Comparative US-MRI evaluation of the Insall-Salvati index. Radiol Med. 2017;122:761-65.
8. Lee PP, Chalian M, Carrino JA, et al. Multimodality correlations of patellar height measurement on X-ray, CT, and MRI. Skeletal Radiol. 2012;41:1309-14.

9. Laugharne E, Bali N, Purushothamdas S, et al. Variability of measurement of patellofemoral indices with knee flexion and quadriceps contraction: An MRI-Based Anatomical study. Knee Surg Relat Res. 2016;28:297-301.
10. Verhulst FV, van Sambeeck JDP, Olthuis GS, et al. Patellar height measurements: Insall-Salvati ratio is most reliable method. Knee Surg Sports Traumatol Arthrosc. 2020;28:869-75.
11. Walker P, Harris I, Leicester A. Patellar tendon-to-patella ratio in children. J Pediatr Orthop. 1998;18:129-31.
12. Marchevsky AM, Walts AE, Lissenberg-Witte BI, et al. Pathologists should probably forget about kappa. Percent agreement, diagnostic specificity and related metrics provide more clinically applicable measures of interobserver variability. Ann Diagn Pathol. 2020;47:151561.
13. Vaisman AB, Schmidt-Hebbel AN, Guiloff RK, et al. Is the clinician's eye a valid and reproducible tool for diagnosing patella alta on a lateral knee radiography? J Am Acad Orthop Surg Glob Res Rev. 2020;4:e2000098.
14. Park MS, Chung CY, Lee KM, et al. Which is the best method to determine the patellar height in children and adolescents? Clin Orthop Relat Res. 2010;468:1344-51.
15. Biedert RM, Albrecht S. The patellotrochlear index: a new index for assessing patellar height. Knee Surg Sports Traumatol Arthrosc. 2006;14:707-12.
16. Seil R, Müller B, Georg T, et al. Reliability and interobserver variability in radiological patellar height ratios. Knee Surg Sports Traumatol Arthrosc. 2000;8:231-6.
17. Grelsamer RP, Proctor CS, Bazos AN. Evaluation of patellar shape in the sagittal plane. A clinical analysis. Am J Sports Med. 1994;22:61-6.