| Abstract / Summary | Background and Aim:
Traumatic anterior shoulder instability is a condition that impairs shoulder and upper limb function, particularly affecting young and active individuals. This condition can negatively impact activity levels, work ability, and overall quality of life. The role of biomechanics in the management of these patients remains poorly understood. Despite advancements in diagnostic techniques, there is still no consensus on the best way to assess shoulder biomechanics, particularly in dynamic contexts. The aim of this thesis was to explore biomechanical changes in shoulders with traumatic anterior instability, with a focus on anterior-posterior glenohumeral translation, and to evaluate the potential of two examination methods.
Methods:
The thesis includes four studies. Study I is a systematic review evaluating the current literature on anterior-posterior glenohumeral translation. Study II assesses the validity and reliability of a skin marker-based optical motion capture (OMC) model developed at our facilities. Study III examines the reliability of a standardized ultrasound protocol for measuring anterior-posterior glenohumeral translation. Study IV is an ongoing prospective cohort study investigating the effect of arthroscopic Bankart repair on biomechanical properties and neuromuscular control. A protocol article outlining the study design has been published and is included in this thesis.
Results:
Study I revealed substantial heterogeneity in the methodologies and outcomes across studies, with no consistent approach to measuring anterior-posterior glenohumeral translation. Overall, the translation was larger and often more anteriorly directed in unstable than in stable shoulders, but no specific threshold was found for abnormal translation or the shoulder positions or motion tasks that trigger it. Study II demonstrated that the skin marker-based OMC model had errors of less than 8° in scapular kinematics and more than 3 mm in glenohumeral kinematics, with inconsistent reliability across measures. The ultrasound protocol in Study III demonstrated variability in both intra- and interrater reliability, with differences observed in measurements for both single and multiple raters. The inclusion process for Study IV finished in September 2024 and while data collection is expected to be completed in November 2025, the protocol article was published to ensure transparency, facilitate reproducibility, and strengthen the credibility of the results.
Conclusion:
This thesis highlights the significant gaps in biomechanical research on traumatic anterior shoulder instability, emphasizing the need for standardized methodologies and greater transparency in reporting. The substantial variability across existing studies limits the ability to draw definitive conclusions about glenohumeral translation and its role in instability. A more precise understanding of these biomechanical changes could improve clinical assessment and patient management.
By exploring non-invasive examination methods, this thesis provides valuable insights into their potential and limitations. While optical motion capture and ultrasound seem promising for dynamic shoulder assessment, their clinical applicability remains limited by variability in measurement accuracy and reliability. These findings lay the groundwork for future research aimed at refining assessment techniques and establishing improved methodologies. Additionally, they may help prevent the use of inaccurate models that fail to meet clinical standards.
With the completion of data collection for the ongoing prospective cohort study in 2025, we anticipate that further insights into the interplay between biomechanical, neuromuscular, and clinical outcomes will emerge. Our goal is that these findings will contribute to a more comprehensive understanding of shoulder instability, ultimately guiding improvements in diagnostic and therapeutic approaches.
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| Andre oplysninger | Anterior-posterior glenohumeral translation in shoulders with traumatic anterior instability: a systematic review of the literature.
Malmberg C, Andreasen KR, Bencke J, Hölmich P, Barfod KW.
JSES Rev Reports, Tech. 2023;3(4):477-493. doi:10.1016/j.xrrt.2023.07.002
Three-dimensional measurements of scapular kinematics: Interrater reliability and validation of a skin marker-based model against an intracortical pin model.
Malmberg C, Jensen SE, Michaud B, Andreasen KR, Hölmich P, Barfod KW, Bencke J.
Heliyon. 2024;10(8):e29414. doi:10.1016/j.heliyon.2024.e29414
Reliability of ultrasound measurements of glenohumeral instability.
Malmberg C, Andreasen KR, Bencke J, Kjær BH, Hölmich P, Barfod KW.
August 2025: Manuscript accepted for publication in the Danish Medical Journal.
Biomechanical and neuromuscular characteristics in patients with traumatic anterior shoulder instability undergoing arthroscopic Bankart repair: a clinical prospective cohort study protocol.
Malmberg C, Andreasen KR, Bencke J, Kjær BH, Hølmich P, Barfod KW.
BMJ Open. 2024;14(3):e078376. doi:10.1136/bmjopen-2023-078376
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