Assessment of Inter- and Intrasurgeon Variability in Preoperative Planning of Reverse Shoulder Arthroplasty: A Multicenter Evaluation.

 To evaluate the intra and intersurgeon variability regarding the positioning and selection of implants in reverse shoulder arthroplasty.  A cross-sectional study assessed computed tomography images of the shoulder joint of patients diagnosed with degenerative joint diseases. The study team included seven specialists in shoulder surgery, representing six different institutions. Surgeons were instructed to plan all cases twice, and then we evaluated inter- and intrasurgeon variability.  The interclass correlation for version and inclination showed low agreement concerning inclination (0.26), and moderate agreement for version (0.73) and graft selection (0.54). The intrasurgeon evaluation revealed a moderate correlation for version (0.55), inclination (0.58), and implant selection (0.46), while for lateralization the correlation was high (0.77).  This comparative study of preoperative planning by different surgeons showed the lack of consensus on implant positioning parameters during reverse shoulder arthroplasty planning. However, most surgeons tend to plan for zero degrees of version and inclination.