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Patella height measurements in patients with patellofemoral instability: the power to predict patella height indices

  • Orthopaedic Surgery
  • Published:
Archives of Orthopaedic and Trauma Surgery Aims and scope Submit manuscript

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Abstract

Introduction

Numerous indices for patella height measurement are described in the literature; however, there is not a universally accepted ‘gold standard’. Choice of indices varies depending on personal preference and previous experience, making it difficult to compare results between studies. The aims of this study were to assess the correlation between different patella height indices and generate statistically derived formulae that can be used to predict the value of one patella height ratio when another is known.

Materials and Methods

Patients with patellofemoral instability were radiologically evaluated using both X-ray and Magnetic Resonance Imaging (MRI) of the knee. Two observers measured six validated patella height indices at two separate time intervals. All measurements were aggregated together and a mean average for each patella height ratio was calculated. These results were then statistically analysed using Pearson product-moment correlation and linear regression tests.

Results

Forty-four patients were included in the study. A statistically significant correlation was found between the majority of patella height ratios. On X-ray, the strongest correlation (r = 0.92, p < 0.001) and regression (R2 = 0.85, p < 0.001) coefficients were between the Blackburne-Peel and Caton-Dechamps ratios, with the formula; CD = 0.20 + (0.95xBP). On MRI, the strongest correlation (r = − 0.84, p < 0.001) and regression (R2 = 0.71, p < 0.001) coefficients were between the Patellophyseal index and Patellotrochlear index, with the formula; PP = 1.02-(1.10xPT).

Conclusion

The formulae produced in this study can predict the value of one patella height ratio when the results of another are known. This could facilitate systematic reviews and meta-analyses by allowing the pooling together of data from many studies.

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Data availability

Data for this study is not available for further dissemination due to the host intuitions patient data protection policy.

Change history

  • 27 February 2024

    In the discussion section, the following sentence has been changes from “The mean angle of knee flexion measured on MRI for the present study is 17.2 degrees, which is closer to the more universally accepted measurement the position of 30 degrees” to “The mean angle of knee flexion measured on MRI for the present study is 17.2 degrees, which is closer to the more universally accepted measurement position of 30 degrees” in the sixth paragraph.

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Funding

This study did not receive any funding from any source.

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Authors and Affiliations

  1. Department of Trauma and Orthopaedic Surgery, South Tyneside District Hospital, Harton Lane, South Tyneside, NE34 0PL, UK

    Stephen Picken, Harry Summers & Oday Al-Dadah

  2. Translational and Clinical Research Institute, Faculty of Medical Sciences, Newcastle University, Framlington Place, Newcastle-Upon-Tyne, NE2 4HH, UK

    Oday Al-Dadah

Authors
  1. Stephen Picken
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  2. Harry Summers
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Correspondence to Stephen Picken.

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This was a retrospective radiological study which did not require IRB / ethics committee approval.

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Informed consent was not required for the study as it evaluated existing clinical practice, for which informed consent was obtained.

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Picken, S., Summers, H. & Al-Dadah, O. Patella height measurements in patients with patellofemoral instability: the power to predict patella height indices. Arch Orthop Trauma Surg 144, 1511–1522 (2024). https://doi.org/10.1007/s00402-024-05204-w

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  • DOI: https://doi.org/10.1007/s00402-024-05204-w

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