Operative guidelines for the reconstruction of the native glenoid plane: an anatomic three-dimensional computed tomography-scan reconstruction study

Background: Reconstruction of the native plane in biconcave eroded glenoids is difficult. Nevertheless, accurate reconstruction of this plane is imperative for successful total shoulder arthroplasty. This study aims to determine guidelines that can increase the accuracy of glenoid component positioning. Methods: Three different circular planes were determined on 3-dimensional computed tomography (CT) scans of 152 healthy shoulders. First, the circular max (CM) plane is formed with the superior tubercle and 2 points, 1 anterior and 1 posterior, at the rim of the inferior third of the glenoid. Second, the circular inferior (CI) plane is formed by 3 points at the inferior 2 quadrants of the glenoid rim. Third, the circular minima (Cm) plane is formed with 3 points situated at the noneroded sector of the anterior glenoid. The angulation of the spinal scapular axis (SSA), the line between the most medial point of the scapular spine and the center of the three different glenoid planes, and the correlation coefficient between the radius of the circle and the length of SSA are calculated. Results: Angle SSA in the x-axis were 94 degrees, 93 degrees, 93 degrees and in the y-axis were 95 degrees, 111 degrees, and 111 degrees for CM, CI, and Cm, respectively. Correlation coefficient between the radius of the circle and the length of SSA: r = 0.69 for CM, r = 0.75 for CI, and r = 0.75 for Cm. Conclusion: Three points situated at the native anterior glenoid can reconstruct, within 2 degrees accuracy (95% confidence interval, 1.8 degrees-2.3 degrees), the CI plane. A relationship exists between the radii of the 3 glenoid circles and the width of the scapula (SSA length). Level of evidence: Basic Science Study, Anatomic Study, Imaging. (C) 2012 Journal of Shoulder and Elbow Surgery Board of Trustees.