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Bisect offset ratio and cartilaginous sulcus angle are good combined predictors of recurrent patellar dislocation in children and adolescents
  1. Sheanna Maine1,2,
  2. Christina Ngo-Nguyen1,
  3. Martina Barzan2,
  4. Chris Stockton3,
  5. Luca Modenese2,4,
  6. David Lloyd2,
  7. Christopher Carty1,2
  1. 1 Department of Orthopaedics, Children's Health Queensland Hospital and Health Service, Brisbane, Queensland, Australia
  2. 2 Griffith Centre of Biomedical and Rehabilitation Engineering, Griffith University, Gold Coast, Queensland, Australia
  3. 3 Medical Imaging and Nuclear Medicine, Queensland Children's Hospital, South Brisbane, Queensland, Australia
  4. 4 Department of Civil and Environmental Engineering, Imperial College London, London, UK
  1. Correspondence to Dr Martina Barzan, Griffith Centre of Biomedical and Rehabilitation Engineering, Griffith University, Gold Coast, Queensland, Australia; m.barzan{at}


Objectives Recurrent patellar dislocation (RPD) is found most commonly in the juvenile population. While risk factors have been well-established in adults, there remains a paucity in radiographical data to define normal and pathoanatomical juvenile cohorts. The objectives of this paper were to elucidate the differences in the patellofemoral joint between RPD and typically developed (TD) juvenile populations, using MRI measurements, and determine the best independent and combined predictors of RPD.

Methods A prospective, cross-sectional study was conducted with 25 RPD and 24 TD participants aged between 8 and 19 years. MR images were obtained to assess common measures of lower limb alignment, patellofemoral alignment, and trochlear dysplasia.

Results Significant differences were evident for acetabular inclination, tibial-femoral torsion, tibial tubercle-to-trochlear groove (TT-TG) distance, lateral patellar tilt (LPT), cartilaginous sulcus angle (CSA) and bisect offset ratio (BOR). CSA and BOR were included in the final predictive model, which correctly classified 89.4% of RPD cases.

Conclusion Radiographical parameters that stratify risk of RPD in adults are also able to predict RPD in the pediatric population (TT-TG, LPT, CSA and BOR). Together, CSA and BOR accurately identified 89.4% of RPD. These measures should be included in the evaluation of pediatric patients who present with patellar dislocation.

Level of evidence Level II.

  • knee
  • dislocation
  • MRI
  • joint instability

Data availability statement

Data are available on reasonable request.

Statistics from

Data availability statement

Data are available on reasonable request.

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  • SM and CN-N are joint first authors.

  • Twitter @MartinaBarzan, @modenaxe, @dlloyd290859, @christophrcarty

  • Contributors All authors have made substantial contribution to the work reported in the manuscript. Specific contributions of each authors are: conception and design of the study: SM, CN-N, MB, CC; data collection: MB, CS, SM; analysis and interpretation of data: SM, CN-N, CC, MB, LM, DL; drafting the manuscript: CN-N; revising the manuscript critically for important intellectual content: SM, CC, MB, CS, LM, DL.

  • Funding MB was supported by a Griffith University Research Higher Degree Scholarship. CC was supported by an Advance Queensland Research Fellowship.

  • Competing interests None declared.

  • Provenance and peer review Not commissioned; externally peer reviewed.

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