The SSM-based reconstruction method is able to accurately reconstruct the native glenoid surface and to predict the native anatomic parameters. Based on this outcome, statistical shape modeling can be considered a successful technique for use in the preoperative planning of shoulder arthroplasty.

Background: Assessment of glenoid bone defects is important to select the optimal glenoid component design during shoulder arthroplasty planning and implantation. This study presents a fully automated method to describe glenoid bone loss using three-dimensional measurements and without the need for a healthy contralateral reference scapula. Methods:The native shape of the glenoid is reconstructed by fitting a statistical shape model (SSM) of the scapula. The total vault loss percentage, local vault loss percentages, defect depth, defect area percentage and subluxation distance and region are computed based on a comparison of the reconstructed and eroded glenoid. The method is evaluated by comparing its results with a contralateral-based reconstruction approach, on a dataset of 34 scapulae and humeri pairs with unilateral glenoid bone defects. Results:The SSM-based defect measurements deviated from the contralateral-based measurements with a mean absolute difference of 5.5% on the total vault loss percentage, 4.5 to 8.0% on the local vault loss percentages, 1.9mm on the defect depth, 14.8% on the defect area percentage and 1.6mm on the subluxation distance. The SSM-based method was found to be statistically equivalent to the contralateral-based method for all parameters except for the defect area percentage. Conclusion:The presented method is able to automatically analyze glenoid bone defects using three-dimensional measurements, without the need for a healthy contralateral bone.

The anatomic parameters of scapular offset, glenoid inclination, and version are quite symmetrical and fall into the currently technically feasible accuracy of shoulder arthroplasty implantation. The healthy scapula can be used as a template to guide the reconstruction of the glenoid during shoulder arthroplasty planning in the case of unilateral advanced arthropathy.