Radiographic Measurements in Reverse Total Shoulder Arthroplasty: Accuracy of Preoperative Planning

Purpose The use of preoperative three-dimensional (3D) planning software has increased when preparing for reverse total shoulder arthroplasty (RSA). Malpositioning of the glenoid baseplate and, subsequently, the glenosphere has been linked to poor patient outcomes and increased rates of revisions. The purpose of this study was to evaluate the accuracy of the radiographic measurements, version, inclination, and RSA angle, in preoperative imaging, the preoperative plan, and postoperative imaging. Methods 73 shoulders that underwent primary RSA with a commercially available 3D planning software program (Blueprint, Wright Medical Technologies Inc., Memphis, TN, USA) were analyzed. Preoperative planning and procedures were performed by two fellowship trained shoulder and elbow surgeons. All patients had complete preoperative and postoperative true anteroposterior and axillary views. Radiographic measurements (version, inclination, and RSA angle) were evaluated and compared on preoperative radiographs, preoperative 3D models with virtually planned RSA constructs, and postoperative radiographs. Results The differences between preoperative and postoperative measurements were significant when comparing native glenoid version with implant version (-6.17o, 95% CI [-7.93o, -4.41o], P<0.001) and native glenoid RSA angle with implant inclination (15.03o, 95% CI [13.61o, 16.45o], P<0.001). Although the differences between planned and postoperative measurements were statistically significant for implant version (1.71o, 95% CI [1.03o, 2.39o], P<0.001) and implant inclination (1.03o, 95% CI [0.4o, 1.67o], P=0.002), clinical significance was not established. Conclusions Significant differences between preoperative and postoperative measurements were observed when comparing native glenoid version with implant version and native RSA angle with implant inclination, demonstrating the value of utilizing preoperative planning software to improve RSA implant positioning. Postoperative measurements of implant version and implant inclination also closely matched the planned measurements, showing that the surgical plan is adequately reproduceable intraoperatively. Continued study of the accuracy in preoperative planning is paramount to understanding its influence on patient outcomes and implant survival in RSA.