Many Radiologic Indices for Patellofemoral Instability Are Unreliable: A Radiologic Interrater Reliability Study Peter D. Fabricant, MD, MPH1; Madison Heath, BS1; Douglas Mintz, MD1; Kathleen H Emery, MD2; Matthew W Veerkamp, BA2; Simone
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Many Radiologic Indices for Patellofemoral Instability Are Unreliable: A Radiologic Interrater Reliability Study Peter D. Fabricant, MD, MPH1; Madison Heath, BS1; Douglas Mintz, MD1; Kathleen H Emery, MD2; Matthew W Veerkamp, BA2; Simone Gruber, MS1; Daniel W. Green, MD, MS, FACS1; Eric J. Wall, MD2; Marc Tompkins, MD3; Benton E. Heyworth, MD4; The JUPITER Study Group; Beth E Shubin Stein, MD1; Shital N. Parikh, MD, FACS2.
1Hospital for Special Surgery, New York, NY, USA. 2Cincinnati Children’s Hospital, Cincinnati, OH, USA. 3TRIA Orthopedic Center, Bloomington, MN, USA. 4 Boston Children’s Hospital, Harvard Medical School, Boston, MA, USA.
The JUPITER Study Group: Jacqueline Brady, MD; Caitlin Chambers, MD; Henry B. Ellis, MD; Jack Farr, MD; Jason L. Koh, MD, MBA; Dennis Kramer, MD; Robert Magnussen, MD; Lauren Redler, MD; Seth Sherman, MD; Philip Wilson, MD.
Acknowledgement: Matthew Milewski, MD; Sabrina Strickland, MD; Yi-Meng Yen, MD<br>
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Disclosure The authors have nothing to disclose<br>
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Introduction Surgical decision making for children and adolescents with patellofemoral instability relies heavily on accurate and consistent assessment of anatomic risk factors
The assessment of risk factors from radiographs and MRIs can help predict risk of recurrence, guide treatment plan and dictate surgical procedures<br>
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Purpose To evaluate the interrater reliability of common radiographic parameters used to evaluate anatomic risk factors for patellofemoral instability
2. To attempt to improve reliability for measurements that demonstrate unacceptable interrater reliability.<br>
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Methods Reliability study on prospectively collected data
2 fellowship-trained musculoskeletal radiologist assessed 50 patients with patellofemoral instability.
22 M / 28 F
Average age: 14 yrs (+/-2)
27 measurements were performed on X-rays and MRI including:
Trochlear dysplasia
Caton-Deschamps index
Patellar tilt<br>
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Methods Intraclass correlation coefficients (ICC) were calculated for each measurement
For all measurements with unacceptable reliability (ICC < 0.6), authors discussed consensus methods to improve reliability.
Raters then re-measured a subset of 20 new patients.
All measurements with an ICC less than 0.6 after consensus building and re-measurement were considered to be unreliable.<br>
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Results First round interrater reliability was acceptable for 5 radiographic measurements and 7 MRI measurements.
After consensus building 4 additional radiographic measurements and 2 MRI measurements were reliable.
6 radiographic measurements and 3 MRI measurements remained unacceptably unreliable even after consensus training.<br>
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Results Radiographs were reliable for Caton Deschamps Index and leg length discrepancy / alignment
MRI were reliable for trochlear dysplasia and patellar tilt
Dejour classification for trochlear dysplasia was unreliable even after consensus training<br>
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Conclusion This study found that many of the clinically relevant patellofemoral instability measurements have unacceptably low reliability across raters.
However, with additional training and better definitions, some measurements do improve across raters.
There are several measurements that did not improve even after additional consensus building and training. This may be due to ambiguity, the difficultly of the measurement, or for indices that are rarely used.
Physicians should ensure that they are using a standardized definition or technique for radiographic measurements in patients with patellofemoral instability.
Unreliable measurements should not be used in clinical decision making process.<br>
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References 1. Dejour H, Walch G, Nove-Josserand L, Guier C. Factors of patellar instability: An anatomic radiographic study. Knee Surgery, Sport Traumatol Arthrosc. 1994;2(1):19-26. doi:10.1007/BF01552649.
2. Smith TO, Davies L, Toms AP, Hing CB, Donell ST. The reliability and validity of radiological assessment for patellar instability. A systematic review and meta-analysis. Skeletal Radiol. 2011;40(4):399-414.
3. Lippacher S, Dejour D, Elsharkawi M, et al. Observer Agreement on the Dejour Trochlear Dysplasia Classification: A Comparison of True Lateral Radiographs and Axial Magnetic Resonance Images. Am J Sports Med. 2012;40(4):837-843. doi:10.1177/0363546511433028.
4. Pfirrmann A, Zanetti M, Romero J, Hodler J. Femoral Trochlear Dysplasia: MR Findings. Radiology. 2000;216:858-864.
5. Ye Q, Yu T, Wu Y, Ding X, Gong X. Patellar instability: The reliability of magnetic resonance imaging measurement parameters. BMC Musculoskelet Disord. 2019;20(1):317. doi:10.1186/s12891-019-2697-7.<br>
