Intra- and inter-observer reliability of Laredo classification system in Legg–Calvé–Perthes Disease

  • Serkan Erkus
  • Ali Turgut
  • Onder KalendererEmail author
  • Kivanc Yuksel
Original Article • HIP - PAEDIATRIC


The purpose of the current study was to investigate intra- and inter-observer reliability of arthrographic Laredo classification system in Perthes disease. Forty-seven patients were included in this cross-sectional descriptive study. Patients’ age, gender, physical findings and hip arthrographs were collected from hospital medical records. Two different sets of power point slides were prepared in which the order of cases was randomized and blinded. Observers were divided into three groups according to their surgical experience (9 residents, 10 seniors, 10 pediatric orthopedists), and they assessed two times 1 month’s intervals. Statistical analysis was performed by using the SPSS v21. Inter- and intra-observer reliabilities were calculated using intra-class correlation coefficient, weighted kappa and percentage agreement. Percentage agreement of Laredo classification was about 50% for all groups (residents, seniors and pediatric orthopedists); intra-observer reliabilities were excellent, excellent and fair, respectively. Inter-observer reliability of Laredo classification for each set was found to be excellent for all groups. Length of experience did not correlated significantly with the level of intra-observer agreement. As a conclusion, our results showed that Laredo’s arthrographic classification system’s intra-observer reliability is at least at a fair level and inter-observer reliability is at an excellent level. We believe that this classification system is valuable for an orthopedic surgeon who deals with the treatment of Perthes disease.


Arthrography Reliability Laredo classification Perthes Children 



We thank Asuman Filiz Guzelant for her contribution.

Compliance with ethical standards

Conflict of interest

The authors declare that they have no conflict of interest.


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Copyright information

© Springer-Verlag France SAS, part of Springer Nature 2019

Authors and Affiliations

  • Serkan Erkus
    • 1
  • Ali Turgut
    • 1
  • Onder Kalenderer
    • 1
    Email author
  • Kivanc Yuksel
    • 2
  1. 1.Department of Orthopaedics and TraumatologyTepecik Training and Research HospitalİzmirTurkey
  2. 2.Ege University School of Medicine ARGEFARİzmirTurkey

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