Effect of glenoid deformity on glenoid component placement in primary shoulder arthroplasty

Background: Malposition of the glenoid component can result in premature component loosening or instability. This study was designed to test the ability of an experienced shoulder surgeon to position the glenoid component using standard preoperative planning and surgical bone preparation. Materials and methods: Thirteen patients having primary total shoulder arthroplasty were evaluated using 3-dimensional surgical simulator. Ideal version was considered to have version as close to perpendicular to the plane of the scapula, with complete contact of the back side of the component on glenoid bone and maintenance of the center peg of the component within bone. Results: The average retroversion angle was 13 degrees (mean, standard deviation [SD] 12 degrees), with a range of 1-42 degrees. In 7 of these 13 cases, preoperative glenoid retroversion was greater or equal to 10 degrees. In 3 cases, the component was malpositioned with greater than 10 degrees of ideal version. In cases with less than 10 degrees of preoperative retroversion, the glenoid component was placed within 10 degrees of ideal version in all cases. Conclusion: Traditional methods to correct moderate to severe glenoid deformity and place the glenoid component within 5 degrees of the ideal position are not consistent. Optimal glenoid component placement can be achieved when there is minimal bone deformity. Retroversion greater or equal to 20 degrees makes it difficult to place a pegged glenoid component perpendicular to the plane of the scapula by asymmetric reaming without center peg perforation. Level of evidence: Level IV, Case Series, Treatment Study. (C) 2012 Journal of Shoulder and Elbow Surgery Board of Trustees.