Purpose
To establish the accuracy and reliability of the circle-line method (CLM) of measuring
glenoid bone loss; to compare the CLM calculation with a traditionally used method
of calculating a ratio; and to evaluate surgeons' ability to estimate the amount of
glenoid bone loss before performing any calculations.
Methods
Three-dimensional reconstructions of computed tomography scans of consecutive patients
with anterior instability and glenoid bone loss were reviewed by 13 surgeons blinded
to the diagnosis. The reviewers made estimations of bone loss before creating any
measurements by viewing the available computed tomography scan as well as the 3-dimensional
reconstructions. They selected an en face view of the glenoid to create a best-fit
circle. Bone loss calculation with a traditional linear method as well as a CLM calculated
by algebraic geometry was completed. The CLM requires calculation of the diameter
of a best-fit circle on the glenoid, as well as the length of a single line along
the circle representing the line of bone loss. All methods were compared with a computerized
method of tracing the area of the glenoid within a best-fit circle. Interobserver
and intraobserver calculations were performed. Analysis-of-variance testing was used
to compare the estimates of bone loss versus the CLM-calculated bone loss. Tukey post
hoc analysis was used to define the accuracy of the CLM calculation compared with
a more traditional method of calculating bone loss.
Results
Bone loss estimations were significantly different from CLM-calculated bone loss in
all cases except those with greater than 25% bone loss. The CLM was more accurate
in all types of bone loss except cases of greater than 25% bone loss. Interobserver
reliability was very good for the glenoid diameter measurement and moderate for the
CLM. Intraobserver reliability ranged from moderate to good for all methods of measurement.
Conclusions
Surgeon estimations of glenoid bone loss, as well as traditional line-measurement
calculations, are inconsistent and unreliable for accurate determination of the optimal
surgical treatment for anterior shoulder instability. The CLM is a simple, reproducible,
and accurate method for determining glenoid bone loss and does not require specialized
software or imaging protocols.
Level of Evidence
Level II, diagnostic study.
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Article Info
Publication History
Published online: October 21, 2017
Accepted:
July 27,
2017
Received:
January 17,
2017
Footnotes
The authors report the following potential conflict of interest or source of funding: M.T.P. receives support from AOSSMA/AANA, Arthrex/JRF, PRORP shoulder instability database. Arthrex. Suture washer and pec button. Elsevier–Arthroscopy Journal, Shoulder Instability Textbook, Rehabilitation Textbook. Full ICMJE author disclosure forms are available for this article online, as supplementary material.
Identification
Copyright
Published by Elsevier on behalf of the Arthroscopy Association of North America
