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Return to Play Prediction Accuracy of the MLG-R Classification System for Hamstring Injuries in Football Players: A Machine Learning Approach

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Abstract

Background and Objective

Muscle injuries are one of the main daily problems in sports medicine, football in particular. However, we do not have a reliable means to predict the outcome, i.e. return to play from severe injury. The aim of the present study was to evaluate the capability of the MLG-R classification system to grade hamstring muscle injuries by severity, offer a prognosis for the return to play, and identify injuries with a higher risk of re-injury. Furthermore, we aimed to assess the consistency of our proposed system by investigating its intra-observer and inter-observer reliability.

Methods

All male professional football players from FC Barcelona, senior A and B and the two U-19 teams, with injuries that occurred between February 2010 and February 2020 were reviewed. Only players with a clinical presentation of a hamstring muscle injury, with complete clinic information and magnetic resonance images, were included. Three different statistical and machine learning approaches (linear regression, random forest, and eXtreme Gradient Boosting) were used to assess the importance of each factor of the MLG-R classification system in determining the return to play, as well as to offer a prediction of the expected return to play. We used the Cohen’s kappa and the intra-class correlation coefficient to assess the intra-observer and inter-observer reliability.

Results

Between 2010 and 2020, 76 hamstring injuries corresponding to 42 different players were identified, of which 50 (65.8%) were grade 3r, 54 (71.1%) affected the biceps femoris long head, and 33 of the 76 (43.4%) were located at the proximal myotendinous junction. The mean return to play for grades 2, 3, and 3r injuries were 14.3, 12.4, and 37 days, respectively. Injuries affecting the proximal myotendinous junction had a mean return to play of 31.7 days while those affecting the distal part of the myotendinous junction had a mean return to play of 23.9 days. The analysis of the grade 3r biceps femoris long head injuries located at the free tendon showed a median return to play time of 56 days while the injuries located at the central tendon had a shorter return to play of 24 days (p = 0.038). The statistical analysis showed an excellent predictive power of the MLG-R classification system with a mean absolute error of 9.8 days and an R-squared of 0.48. The most important factors to determine the return to play were if the injury was at the free tendon of the biceps femoris long head or if it was a grade 3r injury. For all the items of the MLG-R classification, the intra-observer and inter-observer reliability was excellent (k > 0.93) except for fibres blurring (κ = 0.68).

Conclusions

The main determinant for a long return to play after a hamstring injury is the injury affecting the connective tissue structures of the hamstring. We developed a reliable hamstring muscle injury classification system based on magnetic resonance imaging that showed excellent results in terms of reliability, prognosis capability and objectivity. It is easy to use in clinical daily practice, and can be further adapted to future knowledge. The adoption of this system by the medical community would allow a uniform diagnosis leading to better injury management.

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Author information

Authors and Affiliations

  1. FC Barcelona Medical Department, Barcelona, Spain

    Xavier Valle, Sandra Mechó, Ricard Pruna, Gil Rodas & Xavier Yanguas

  2. Hospital Universitari Dexeus (ICATME), Barcelona, Spain

    Xavier Valle

  3. PhD Student at the “Departament de Cirurgia i Ortopèdia”, Universitat Autonoma de Barcelona, Barcelona, Spain

    Xavier Valle

  4. Department of Radiology, Hospital de Barcelona, SCIAS, Barcelona, Spain

    Sandra Mechó

  5. Instituto Cugat, Barcelona, Spain

    Eduard Alentorn-Geli

  6. Fundación García Cugat, Barcelona, Spain

    Eduard Alentorn-Geli

  7. Mutualidad Española de Futbolistas, Delegación Cataluña, Federación Española de Fútbol, Barcelona, Spain

    Eduard Alentorn-Geli

  8. Tampere University and Tampere University Hospital, Tampere, Finland

    Tero A. H. Järvinen

  9. Sports Trauma Research Unit, Hospital Mehiläinen NEO, Turku, Finland

    Lasse Lempainen

  10. Department of Orthopedic Surgery, Parc de Salut Mar, Hospital del Mar I L’Esperança, Barcelona, Spain

    Joan C. Monllau

  11. ICATME, Hospital Universitari Dexeus, Bellaterra, Spain

    Joan C. Monllau

  12. Universitat Autònoma de Barcelona, Bellaterra, Spain

    Joan C. Monllau

  13. Musculoskeletal Imaging Specialist, Barcelona, Spain

    Jaime Isern-Kebschull

  14. Department of Radiology at Hospital Clinic, Universitat de Barcelona, Barcelona, Spain

    Jaime Isern-Kebschull

  15. FIFA Medical Centre of Excellence, Dubai, United Arab Emirates

    Mourad Ghrairi

  16. Catalan Sports Council, Generalitat de Catalunya, Barcelona, Spain

    Ramon Balius

  17. Department of Sports Medicine, Clínica Diagonal, Barcelona, Spain

    Ramon Balius

  18. Institute of Pharmaceutical Sciences, Department of Chemistry and Applied Biosciences, ETH Zurich, Zurich, Switzerland

    Adrian Martinez-De la Torre

Authors
  1. Xavier Valle
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  2. Sandra Mechó
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  3. Eduard Alentorn-Geli
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  4. Tero A. H. Järvinen
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  5. Lasse Lempainen
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  6. Ricard Pruna
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  7. Joan C. Monllau
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  8. Gil Rodas
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  9. Jaime Isern-Kebschull
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  10. Mourad Ghrairi
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  11. Xavier Yanguas
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  12. Ramon Balius
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  13. Adrian Martinez-De la Torre
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Corresponding author

Correspondence to Xavier Valle.

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Funding

No funding was received for the present study.

Conflict of interest

None of the authors has a conflict of interest related to the present investigation.

Ethics Approval

This study was assessed and approved by the Ethics Committee of the “Consell Català de l’Esport” with the number 10/CEICGC/2020. The present study was performed in accordance with the standards of ethics outlined in the Declaration of Helsinki.

Consent to Participate

Appropriate written informed consent to participate in research projects was obtained from all FC Barcelona football players.

Consent for Publication

Appropriate written informed consent for publication was obtained from all participants in the present study.

Availability of Data and Material

The datasets generated during and/or analysed during the current study are not publicly available because of the fact that many of the players had their injury status publicly informed in the mass media and, therefore, some personal information from the players regarding their injuries could be deduced. This could imply a violation of the patients’ privacy and confidentiality noted in statement number 24 of the Declaration of Helsinki. We could make it available from the corresponding author on reasonable request, from a medical institution.

Code Availability

Not applicable.

Author Contributions

XV and XY collected all the data. XV and SM analysed the magnetic resonance images. AM conducted all the statistical analyses. XV, SM, EAG, TJ and AM prepared the manuscript. RP, LL, GR, JCM, JI, MG and RB were the major contributors to the preparation of the manuscript. All authors contributed to the last editing and approval of the final manuscript.

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Valle, X., Mechó, S., Alentorn-Geli, E. et al. Return to Play Prediction Accuracy of the MLG-R Classification System for Hamstring Injuries in Football Players: A Machine Learning Approach. Sports Med 52, 2271–2282 (2022). https://doi.org/10.1007/s40279-022-01672-5

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