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Reliable skeletal maturity assessment for an AIS patient cohort: external validation of the proximal humerus ossification system (PHOS) and relevant learning methodology

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Abstract

Study design

Validation of classification system.

Objectives

To externally validate the Proximal Humerus Ossification System (PHOS) as a reliable skeletal maturity scoring system and to assess the learning curve associated with teaching the procedure to individuals of varying levels of experience.

Background

Assessment of skeletal maturity is essential for treatment decisions in Adolescent Idiopathic Scoliosis (AIS). PHOS is a five-stage system that uses the proximal humeral physis in assessing skeletal maturity and has been shown to reliably grade skeletal age leading up to and beyond peak growth age (PGA). This system is advantageous in the AIS patient, as it is often captured in standard scoliosis films.

Methods

A medical student, an orthopedic surgery resident (PGY-2), spine fellow, and experienced scoliosis surgeon in his 25th year in practice were given a three-slide PHOS learning module. Each participant rated 100 X-rays on two separate occasions, separated by 1 week. Intra- and inter-observer reliability, as well as cross-institutional reliability, were calculated using intraclass correlation coefficients (ICC) with 95% confidence intervals [CI95].

Results

Average intra-observer reliability ICC between scoring sessions was 0.94 [0.92, 0.96] and inter-observer reliability by level of training were 0.94 [0.91, 0.96], 0.93 [0.9, 0.95], 0.94 [0.91, 0.96], 0.96 [0.94, 0.97] for the medical student, PGY-2, fellow, and attending, respectively. Reliability across institutions was 0.99 [0.98, 0.99]. Combined rating observations (n = 400) showed 82% exact matches, as well as 17% and 1% mismatches by 1 and 2 stages, respectively. Similar to the PHOS developers, we found PHOS stage 3 to occur immediately after PGA.

Conclusion

PHOS is easily learned and employed by raters with varying levels of training. It comprises a five-stage system to reliably measure bone age leading up to PGA and thereafter. This new system relies on visualization of the proximal humerus, which is readily available on standard scoliosis X-rays.

Level of evidence

Level III.

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Fig. 1

taken from the PHOS developers. d (right) was adapted from the Human Walking (p. 34) by V. T. Inman, H. J. Ralston, and F. Todd

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Funding

This study was funded by the Pediatric Orthopedic Society of North America (POSNA).

Author information

Authors and Affiliations

  1. Leni & Peter W. May Department of Orthopaedics, Icahn School of Medicine at Mount Sinai, New York, NY, USA

    Theodor Di Pauli von Treuheim, Christopher Mikhail, Daniel Cataldo & Baron Lonner

  2. Department of Orthopaedics and Rehabilitation, Yale School of Medicine, New Haven, CT, USA

    Don T. Li & Daniel R. Cooperman

  3. Department of Cell Biology, Yale School of Medicine, New Haven, CT, USA

    Don T. Li

  4. Division of Orthopaedics, Texas Children’s Hospital, Houston, TX, USA

    Brian G. Smith

  5. Icahn Mount Sinai School of Medicine, 5 East 98th Street, 4th Floor, New York, NY, 10029, USA

    Theodor Di Pauli von Treuheim & Baron Lonner

Authors
  1. Theodor Di Pauli von Treuheim
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  2. Don T. Li
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  3. Christopher Mikhail
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  4. Daniel Cataldo
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  5. Daniel R. Cooperman
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  6. Brian G. Smith
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  7. Baron Lonner
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Contributions

TDPVT, DL, CM, DC, DC, BS, and BL: conception and design, acquisition and data, analysis and interpretation of data, drafting of the manuscript, revision for important intellectual content, administrative, technical or material support, and approval final version of paper. TDPVT and DL: statistical analysis. TDPVT and BL: supervision.

Corresponding author

Correspondence to Baron Lonner.

Ethics declarations

Conflict of interest

Dr. Li reports grants from Pediatric Orthopedic Society of North America, during the conduct of the study. Dr. Lonner reports grants from POSNA, during the conduct of the study; personal fees, non-financial support and other from Depuy Synthes, other from Ethicon, personal fees and other from Zimmer Biomet, personal fees and non-financial support from Apifix, personal fees from Unyq Align, other from Paradigm Spine, non-financial support and other from Spine Search, other from Setting Scoliosis Straight Foundation, personal fees from K2M, outside the submitted work. The remaining authors have nothing to disclose.

Ethical approval

This study was reviewed and approved by the Yale Human Research Protection Program IRB. IRB Submission ID 2000021626.

Informed consent

Obtained by the original investigators who compiled the imaging data set.

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Di Pauli von Treuheim, T., Li, D.T., Mikhail, C. et al. Reliable skeletal maturity assessment for an AIS patient cohort: external validation of the proximal humerus ossification system (PHOS) and relevant learning methodology. Spine Deform 8, 613–620 (2020). https://doi.org/10.1007/s43390-020-00105-5

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  • DOI: https://doi.org/10.1007/s43390-020-00105-5

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