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Area-Based Determination of Bone Loss Using the Glenoid Arc Angle

      To the Editor:
      Concerning the article by Dumont et al., “Area-Based Determination of Bone Loss Using the Glenoid Arc Angle,”
      • Dumont G.D.
      • Russell R.D.
      • Browne M.G.
      • Robertson W.J.
      Area-based determination of bone loss using the glenoid arc angle.
      published in the July 2012 issue of Arthroscopy, we appreciate the mathematical-geometrical approach to determine glenoid bone loss
      • Wambacher M.
      • Oberladstätter J.
      • Rieger M.
      Computertomographie der Schulter.
      and hope that it becomes more popular as it was published in this high-level journal.
      Dumont et al. state that a bilateral CT scan for comparison has the inherent disadvantage of added radiation exposure for the patient. This is not correct because recording axial scans of one shoulder with spiral CT automatically causes radiation exposure to both shoulders, because the scanner has to radiograph the entire transversal section. Therefore, recording axial scans of both shoulders has no additional radiation exposure. The radiologist may reconstruct both sides out of the same data set as long as the surgeon requests primary axial scans of both shoulders.
      Jeske et al.
      • Jeske H.-C.
      • Oberthaler M.
      • Klingensmith M.
      • et al.
      Normal glenoid rim anatomy and the reliability of shoulder instability measurements based on intrasite correlation.
      confirmed that the healthy inferior glenoid has the shape of a circle, and they described a perfect side-to-side correlation of the glenoid surface area. This correlation can be applied to improve measurement of bony glenoid defects by using the diameter of the ROI of the nonaffected glenoid as a reference.
      According to our institutional experience, especially large glenoid defect sizes tend to be underestimated, without taking the contralateral healthy glenoid into account. The glenoid arc angle method with bilateral testing may hold the potential for higher reproducibility and practicability, but this has not been proven yet. An exact consistent measurement standard will allow recommendations on treatment of shoulder instability combined with glenoid bone loss and may be the precondition to define the critical size of glenoid bone loss.

      References

        • Dumont G.D.
        • Russell R.D.
        • Browne M.G.
        • Robertson W.J.
        Area-based determination of bone loss using the glenoid arc angle.
        Arthroscopy. 2012; 28: 1030-1035
        • Wambacher M.
        • Oberladstätter J.
        • Rieger M.
        Computertomographie der Schulter.
        in: Habermeyer P. Lichtenberg S. Magosch P. Schulterchirugie. Elsevier GmbH, Urban & Fischer Verlag, München2010: 112-131
        • Jeske H.-C.
        • Oberthaler M.
        • Klingensmith M.
        • et al.
        Normal glenoid rim anatomy and the reliability of shoulder instability measurements based on intrasite correlation.
        Surg Radiol Anat. 2009; 31: 623-625

      Linked Article

      • Area-Based Determination of Bone Loss Using the Glenoid Arc Angle
        ArthroscopyVol. 28Issue 7
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          In patients with anterior glenohumeral instability, the most commonly observed osseous defect involves the anterior portion of the inferior glenoid. The amount of glenoid bone loss guides surgical treatment, with progressively larger defects not being amenable to arthroscopic soft-tissue procedures. Currently, there is no universally accepted method of quantifying glenoid bone loss. Two-dimensional area-based methods and 1-dimensional methods of measuring bone loss have both been described but cannot be used interchangeably.
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      • Author's Reply
        ArthroscopyVol. 30Issue 3
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          In response to the letter by Hengg et al. concerning our article entitled “Area-Based Determination of Bone Loss Using the Glenoid Arc Angle” published in the July 2012 issue of Arthroscopy, we appreciate the clarification regarding the amount of radiation exposure for bilateral shoulder computed tomography. The comments by Hengg et al. bring to our attention the fact that if computed tomography images of the contralateral uninjured shoulder are obtained simultaneously with that of the injured shoulder, no additional radiation is incurred by the patient.
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