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  Bart Pijls
  Published on: 11 October 2022

• Published on: 11 October 2022

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  • Bart Pijls, Orthopaedic Resident
  • Other Contributors:
    • Henk Arens, Frans Kok, and Nick Guldemond

  Dear Editor

  We have read with great interest the article by Silva et al and acknowledge their innovating and pioneering work in the field of shoulder dyskinesia. Their research uncovered a greater dynamic reduction in subacromial space in tennis players with shoulder dyskinesia (19.3 mm), compared to tennis players without shoulder dyskinesia (13.8 mm). The authors claim there would be an average difference in dy...

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  Dear Editor

  We have read with great interest the article by Silva et al and acknowledge their innovating and pioneering work in the field of shoulder dyskinesia. Their research uncovered a greater dynamic reduction in subacromial space in tennis players with shoulder dyskinesia (19.3 mm), compared to tennis players without shoulder dyskinesia (13.8 mm). The authors claim there would be an average difference in dynamic reduction of 5.2 mm between these groups. It is improbable to have a 19.3 mm reduction in subacromial space, considering the fact that the largest subacromial space in normal individuals is 17 mm.[1] Most likely, some error has occurred and these values should be divided by a factor ten. In a study by Herbert et al a reduction in subacromial space of approximately 2 mm was found between zero and 70 degrees abduction.[2] Values of 1.93 and 1.38 mm instead of 19.3 and 13.8 mm seem therefore more realistic. This implies that the average difference in reduction between shoulders with and without dyskinesia should be 0.52 mm in stead of 5.2 mm.

  We question the fact whether ultrasonographic measurement of the subacromial space is accurate enough to detect such a small difference. Preliminary results from our own study addressing the issue of reproducibility of ultrasonographic measurement of the subacromial space, indicate that an experienced radiologist is capable of reaching an accuracy of approximately 1 mm (figure 1). This implies that the difference of 0.52 mm in dynamic reduction falls within the measurement error of ultrasonographic measurement of the subacromial space. So, even though Silva et al found a statistically significant difference in dynamic reduction in subacromial space in shoulders with and without dyskinesia, the clinical consequence remains unclear. Additional research is therefore necessary to investigate the clinical use for this promising new technique.

  Figure 1: Bland-Altman-Plot showing difference between measurements plotted against their average for ultrasonograhic measurement of the acromiohumeral distance at zero degrees abduction (cm).

  

  References

  1. Azzoni, R.; Cabitza, P.; and Parrini, M.: Sonographic evaluation of subacromial space. Ultrasonics 2004; 42(1-9): 683-7.

  2. Hebert, L. J.; Moffet, H.; Dufour, M.; and Moisan, C.: Acromiohumeral distance in a seated position in persons with impingement syndrome. J Magn Reson Imaging 2003; 18(1): 72-9.

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  Conflict of Interest:
  None declared.

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