A Comparison of Methods Measuring Glenoid Bone Loss in Patients with Shoulder Instability (SS-08)

Abstract

IntroductionThe shoulder joint is the most dislocated joint (4% incidence rate), with higher incidence rates in athletic and military populations. Recurrent instability is a particular problem in the shoulder as recurrence rates have been reported between 20-90%. Recurrent shoulder instability typically begins with a major trauma which may result in significant bony abnormalities at the glenoid, increasing the risk of future dislocations. The accurate measurement of bone loss at the glenoid is critical to the diagnosis and treatment (soft tissue repair v bony reconstruction) of recurrent shoulder instability. The current gold standard for the measurement of glenoid bone loss is arthroscopic estimation. However, recent studies indicate that arthroscopic estimation may have a strong tendency to overestimate glenoid bony defect size. In addition, numerous other studies have shown the reliability of methods using 3D CT in the preoperative assessment of glenoid bone loss. We hypothesize that arthroscopic estimation will overestimate glenoid bone loss in comparison to methods using 3D CT.Methods20 patients experiencing recurrent shoulder instability had bilateral shoulder CT scans performed and were found to have significant glenoid bone loss. Arthroscopic estimation of glenoid bone loss was performed on each of the 20 patients. Subsequently, two individual observers measured the glenoid bone loss of each patient using the Surface Area Method, Pico Method, Ratio Method, and AP Distance from Bare Area Method. A mean percent bone loss for each patient with each method was calculated and compared to the percent bone loss estimated during arthroscopy to determine the reliability of arthroscopy in the measurement of glenoid bone loss. Statistical analysis was performed using a repeated measures ANOVA. Subsequent statistical analyses included four paired, two-tailed t tests to determine any significant differences between arthroscopic estimation and each of the four methods.ResultsThe mean percent bone loss calculated with the Surface Area Method, Pico Method, Ratio Method, and AP Distance from Bare Area method was 12.15+8.50%, 12.77+8.17%, 9.50+8.74%, and 12.44+10.68%, respectively. The mean percent bone loss determined by arthroscopic estimation was 18.13+11.81%. Statistical analysis using a repeated measures ANOVA demonstrates that the estimates of glenoid bone loss by the four methods using 3D CT reconstruction are significantly less than the percent bone loss estimated by arthroscopy (F4,76=13.168, p<.05).ConclusionThese findings call into question the validity of arthroscopic estimation by demonstrating that arthroscopic estimation significantly overestimates glenoid bone loss and may not be an adequate gold standard. Inconsistencies in the diagnosis and treatment of recurrent shoulder instability may result due to the disparity between arthroscopic estimation and the methods using 3D CT reconstruction. The degree of bone loss may influence the choice of surgical procedure utilized and inaccurate estimation of glenoid bone loss may result in the incorrect use of a surgical procedure on a case of recurrent shoulder instability. These findings suggest the need for establishing a standard method of measurement, which will allow for the establishment of glenoid bone loss ranges in which specific forms of treatment will be used to treat recurrent shoulder instability. IntroductionThe shoulder joint is the most dislocated joint (4% incidence rate), with higher incidence rates in athletic and military populations. Recurrent instability is a particular problem in the shoulder as recurrence rates have been reported between 20-90%. Recurrent shoulder instability typically begins with a major trauma which may result in significant bony abnormalities at the glenoid, increasing the risk of future dislocations. The accurate measurement of bone loss at the glenoid is critical to the diagnosis and treatment (soft tissue repair v bony reconstruction) of recurrent shoulder instability. The current gold standard for the measurement of glenoid bone loss is arthroscopic estimation. However, recent studies indicate that arthroscopic estimation may have a strong tendency to overestimate glenoid bony defect size. In addition, numerous other studies have shown the reliability of methods using 3D CT in the preoperative assessment of glenoid bone loss. We hypothesize that arthroscopic estimation will overestimate glenoid bone loss in comparison to methods using 3D CT. The shoulder joint is the most dislocated joint (4% incidence rate), with higher incidence rates in athletic and military populations. Recurrent instability is a particular problem in the shoulder as recurrence rates have been reported between 20-90%. Recurrent shoulder instability typically begins with a major trauma which may result in significant bony abnormalities at the glenoid, increasing the risk of future dislocations. The accurate measurement of bone loss at the glenoid is critical to the diagnosis and treatment (soft tissue repair v bony reconstruction) of recurrent shoulder instability. The current gold standard for the measurement of glenoid bone loss is arthroscopic estimation. However, recent studies indicate that arthroscopic estimation may have a strong tendency to overestimate glenoid bony defect size. In addition, numerous other studies have shown the reliability of methods using 3D CT in the preoperative assessment of glenoid bone loss. We hypothesize that arthroscopic estimation will overestimate glenoid bone loss in comparison to methods using 3D CT. Methods20 patients experiencing recurrent shoulder instability had bilateral shoulder CT scans performed and were found to have significant glenoid bone loss. Arthroscopic estimation of glenoid bone loss was performed on each of the 20 patients. Subsequently, two individual observers measured the glenoid bone loss of each patient using the Surface Area Method, Pico Method, Ratio Method, and AP Distance from Bare Area Method. A mean percent bone loss for each patient with each method was calculated and compared to the percent bone loss estimated during arthroscopy to determine the reliability of arthroscopy in the measurement of glenoid bone loss. Statistical analysis was performed using a repeated measures ANOVA. Subsequent statistical analyses included four paired, two-tailed t tests to determine any significant differences between arthroscopic estimation and each of the four methods. 20 patients experiencing recurrent shoulder instability had bilateral shoulder CT scans performed and were found to have significant glenoid bone loss. Arthroscopic estimation of glenoid bone loss was performed on each of the 20 patients. Subsequently, two individual observers measured the glenoid bone loss of each patient using the Surface Area Method, Pico Method, Ratio Method, and AP Distance from Bare Area Method. A mean percent bone loss for each patient with each method was calculated and compared to the percent bone loss estimated during arthroscopy to determine the reliability of arthroscopy in the measurement of glenoid bone loss. Statistical analysis was performed using a repeated measures ANOVA. Subsequent statistical analyses included four paired, two-tailed t tests to determine any significant differences between arthroscopic estimation and each of the four methods. ResultsThe mean percent bone loss calculated with the Surface Area Method, Pico Method, Ratio Method, and AP Distance from Bare Area method was 12.15+8.50%, 12.77+8.17%, 9.50+8.74%, and 12.44+10.68%, respectively. The mean percent bone loss determined by arthroscopic estimation was 18.13+11.81%. Statistical analysis using a repeated measures ANOVA demonstrates that the estimates of glenoid bone loss by the four methods using 3D CT reconstruction are significantly less than the percent bone loss estimated by arthroscopy (F4,76=13.168, p<.05). The mean percent bone loss calculated with the Surface Area Method, Pico Method, Ratio Method, and AP Distance from Bare Area method was 12.15+8.50%, 12.77+8.17%, 9.50+8.74%, and 12.44+10.68%, respectively. The mean percent bone loss determined by arthroscopic estimation was 18.13+11.81%. Statistical analysis using a repeated measures ANOVA demonstrates that the estimates of glenoid bone loss by the four methods using 3D CT reconstruction are significantly less than the percent bone loss estimated by arthroscopy (F4,76=13.168, p<.05). ConclusionThese findings call into question the validity of arthroscopic estimation by demonstrating that arthroscopic estimation significantly overestimates glenoid bone loss and may not be an adequate gold standard. Inconsistencies in the diagnosis and treatment of recurrent shoulder instability may result due to the disparity between arthroscopic estimation and the methods using 3D CT reconstruction. The degree of bone loss may influence the choice of surgical procedure utilized and inaccurate estimation of glenoid bone loss may result in the incorrect use of a surgical procedure on a case of recurrent shoulder instability. These findings suggest the need for establishing a standard method of measurement, which will allow for the establishment of glenoid bone loss ranges in which specific forms of treatment will be used to treat recurrent shoulder instability. These findings call into question the validity of arthroscopic estimation by demonstrating that arthroscopic estimation significantly overestimates glenoid bone loss and may not be an adequate gold standard. Inconsistencies in the diagnosis and treatment of recurrent shoulder instability may result due to the disparity between arthroscopic estimation and the methods using 3D CT reconstruction. The degree of bone loss may influence the choice of surgical procedure utilized and inaccurate estimation of glenoid bone loss may result in the incorrect use of a surgical procedure on a case of recurrent shoulder instability. These findings suggest the need for establishing a standard method of measurement, which will allow for the establishment of glenoid bone loss ranges in which specific forms of treatment will be used to treat recurrent shoulder instability.